Spatiotemporal distribution of Vibrio parahaemolyticus in relation to environmental parameters in a coastal lagoon on the Pacific coast of northwestern Mexico

Rivas-Montaño, Ana M; Luis-Villaseñor, Irasema E; Piña-Valdez, Pablo; Gómez-Gil, Bruno; Lizárraga-Partida, Marcial L; Rivas-Montaño, Ana M; Luis-Villaseñor, Irasema E; Piña-Valdez, Pablo; Gómez-Gil, Bruno; Lizárraga-Partida, Marcial L

doi:10.7773/cm.v44i3.2772

Servicios Personalizados

Revista

Articulo

Indicadores

Citado por SciELO
Accesos

Links relacionados

Similares en SciELO

Otros
Otros

Permalink

Ciencias marinas

versión impresa ISSN 0185-3880

Cienc. mar vol.44 no.3 Ensenada sep. 2018 Epub 30-Jul-2021

https://doi.org/10.7773/cm.v44i3.2772

Articles

Spatiotemporal distribution of Vibrio parahaemolyticus in relation to environmental parameters in a coastal lagoon on the Pacific coast of northwestern Mexico

Distribución espaciotemporal de Vibrio parahaemolyticus con relación a los parámetros ambientales en una laguna costera en la costa del Pacífico del noroeste de México

Ana M Rivas-Montaño¹²

Irasema E Luis-Villaseñor¹^*

Pablo Piña-Valdez¹

Bruno Gómez-Gil³

Marcial L Lizárraga-Partida⁴

^¹Facultad de Ciencias del Mar, Universidad Autónoma de Sinaloa, Paseo Claussen, s/n, Colonia Los Pinos, CP 80000, Mazatlán, Sinaloa, Mexico.

^²Instituto Tecnológico de Mazatlán (ITMAZ), no. 203, Colonia Urías, CP 82070, Mazatlán, Sinaloa, Mexico.

^³Centro de Investigación en Alimentación y Desarrollo, Av. Sábalo Cerritos, s/n, CP 82100, Mazatlán, Sinaloa, Mexico.

^⁴Centro de Investigación Científica y de Educación Superior de Ensenada Baja California, Carretera Ensenada-Tijuana, no. 3918, Zona Playitas, CP 22860, Ensenada, Baja California, Mexico.

Abstract

Vibrio parahaemolyticus has been responsible for the increasing number of diarrhea cases in Sinaloa, Mexico, since 2003. We investigated the presence, distribution, and content of V. parahaemolyticus toxigenic genes detected in water, zooplankton, and sediment samples in relation to environmental variables in Caimanero Lagoon (Mazatlán, Sinaloa). Samples were analyzed by PCR to detect the presence of V. parahaemolyticus and its toxigenic factors. Of all the samples analyzed, 57.5% tested positive for thermolabile hemolysin (tlh), a gene indicative of the species. The thermostable direct hemolysin (tdh) and tdh-related hemolysin (trh) genes, which are both pathogenicity markers of this species, were detected in 9% and 6% of the samples, respectively. The orf8 fragment, which has been recently detected in pandemic strains (O3:K6), was detected in 11% of the samples. Vibrio parahaemolyticus was detected more frequently in zooplankton, with the highest incidence observed in February. Salinity was positively correlated with V. parahaemolyticus; however, no correlation was found between V. parahaemolyticus and temperature. The presence of toxigenic V. parahaemolyticus during the different seasons indicates the need to maintain continuous sanitary inspection of fish products from Caimanero Lagoon.

Key words: coastal lagoon; pathogenic genes; Vibrio parahaemolyticus; environmental parameters

Resumen

Vibrio parahaemolyticus ha sido responsable del creciente número de casos de diarrea en Sinaloa, México, desde 2003. Investigamos la presencia, la distribución y el contenido de los genes toxigénicos de V. parahaemolyticus que fueron detectados en muestras de agua, zooplancton y sedimento y su relación con las variables ambientales en la laguna Caimanero (Mazatlán, Sinaloa). Las muestras fueron analizadas por reacción en cadena de la polimerasa para detectar la presencia de V. parahaemolyticus y sus factores toxigénicos. De todas las muestras analizadas, el 57.5% resultaron positivas para la hemolisina termolábil (tlh), un gen indicativo de la especie. Los genes de la hemolisina directa termoestable (tdh) y la hemolisina relacionada a la tdh (trh), considerados marcadores de la patogenicidad de la especie, fueron detectados en el 9% y el 6% de las muestras, respectivamente. El fragmento orf8, que recientemente se ha detectado en cepas pandémicas (O3:K6), se detectó en el 11% de las muestras. Vibrio parahaemolyticus fue detectado con mayor frecuencia en el zooplancton, con la incidencia más alta observada en febrero. La salinidad se correlacionó positivamente con V. parahaemolyticus; sin embargo, no se registró correlación entre V. parahaemolyticus y la temperatura. La presencia de V. parahaemolyticus toxigénico durante las diferentes temporadas indica la necesidad de mantener la vigilancia sanitaria continua de los productos pesqueros de la laguna Caimanero.

Palabras clave: laguna costera; genes patógenos; Vibrio parahaemolyticus; parámetros ambientales

Introduction

The genus Vibrio currently contains 147 species (^{Parte 2018}), some of which are pathogenic to humans, for example Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae (^{Kaysner and
DePaola 2004}, ^{Johnson 2013}). The members of this genus are free-living microorganisms that are found in marine and estuarine water and sediment habitats, but they can also be associated with the fishes, bivalves, or plankton in an ecosystem (^{Cariani et al. 2012}, ^{Ottaviani et al.
2013}, ^{Givens et al. 2014}).

Vibrio parahaemolyticus (Fugino et al. 1951) is a major causative agent of gastroenteritis in humans following ingestion of contaminated raw shellfish (^{Paranjpye et al. 2012}, ^{Wang et al. 2015}). The symptoms of V. parahaemolyticus infection include diarrhea with abdominal pain, nausea, vomiting, headache, and fever (^{FAO/WHO
2011}, ^{Letchumanan et al. 2014}). Thermostable direct haemolysin (tdh) and tdh-related haemolysin (trh) are the primary pathogenic factors that have been identified in V. parahaemolyticus (^{Zhang and Orth 2013}, ^{Ceccarelli and Colwell 2014}). Since 1996 outbreaks of tdh+/O3:K6 V. parahaemolyticus infections have been recorded in Asia (^{Miyoshi 2013}, ^{Chung-Saint et al. 2016}), Europe (^{Martinez-Urtaza et al. 2016}), the United States (^{Xu et al. 2015}), and Latin America (^{Gavilán and Martínez 2011}, ^{García et al. 2013}, ^{Velazquez-Roman et al. 2014}).

In Mexico, toxigenic V. parahaemolyticus has been reported primarily in the state of Veracruz, near the Gulf of Mexico. ^{Flores-Primo et
al. (2014)} and ^{López-Hernández
(2015)} reported the presence of V. parahaemolyticus in oysters growing in the coastal lagoons of Veracruz. Coastal lagoons along the Pacific coast of Mexico, on the other hand, have been less studied than those along the shoreline of the Gulf of Mexico. In 2004, more than 1,230 V. parahaemolyticus O3:K6 clinical gastroenteritis cases were recorded after the consumption of raw shrimp from the Huizache-Caimanero lagoon system (Sinaloa, Mexico) (^{Cabanillas-Beltrán et al. 2006}). The Caimanero and Huizache lagoons support an important artisanal shrimp fishery, the products of which are distributed to restaurants in tourist areas in the state of Sinaloa and other states in Mexico. The Huizache-Caimanero lagoon system is characterized by extreme salinity fluctuations (between 3 and 60), a seawater temperature range of 20 to 30 ºC, and an intermittent input of non-native nutrients (^{De la
Lanza and Rodríguez 1990}). Overfishing and eutrophication by effluents loaded with nutrients from shrimp farms in the Huizache and Caimanero areas have contributed to changes in the natural ecological conditions of the lagoons and have thus affected the distribution and abundance of microbial populations, including those of bacteria (^{Beltrán-Pimienta and
Retamoza-Leyva 2003}, ^{Romero-Beltrán et
al. 2014}). Bacterial associations with nutrient-rich effluents have also been observed in agricultural activities in other parts of Sinaloa (^{Ahumada-Santos et al. 2014}). This study aimed to determine the presence and distribution of V. parahaemolyticus, its toxigenic variants, and its relation to environmental variables in Caimanero Lagoon.

Materials and methods

Study areas and sampling sites

The study was conducted in Caimanero Lagoon, which is part of the Huizache-Caimanero lagoon system. This lagoon is located approximately 25 km southeast of the port of Mazatlán, Sinaloa (Mexico), between 22º50ʹ00ʺN and 106º01ʹ00ʺW. Water enters the lagoon by means of direct precipitation, drainage from surrounding streams, and inputs from a river through the marshes that connects the system to other rivers and the ocean (i.e., the Anonas Estuary with the Baluarte River and the Pacific Ocean, the Ostial Estuary with the Presidio River and the Pacific Ocean). Water level in the lagoon decreases through evaporation and because of the tidal flow through the Ostial Estuary. Caimanero Lagoon has a total surface area of 134 km², with a maximum length of 19.6 km, ranging widths of 2.5-9.5 km, and ranging depths of 0.2-2.0 m. The largest dimensions are seen only during the rainy season (^{Ramsar 2007}). Climate in the region is tropical, with mean temperature of 22 ºC and a marked rainy season from July to September that accounts for 80% of total rainfall (1,000 mm).

Five sampling sites were selected based on the ecological and hydrological characteristics of the lagoon and on the distance from the lagoon to shrimp farm discharges. Site 1 (22º50ʹ0.99ʺN, 106º1ʹ56.76ʺW) is an area where the Baluarte River drains and seawater enters from the Pacific Ocean. Site 2 (22º53ʹ5.59ʺN, 106º3ʹ40.36ʺW) was the primary access point to the lagoon and was located in an active fishing area (shrimp fishery cooperative). Site 3 (22º57ʹ6.67ʺN, 106º4ʹ21.33ʺW) and site 4 (22º57ʹ6.67ʺN, 106º4ʹ21.33ʺW) were both affected by aquaculture activities (i.e., shrimp farming and production of shrimp larvae). Site 5 (23º0ʹ40.86ʺN, 106º8ʹ59.91ʺW) corresponded to a zone influenced by the Huizache Lagoon and was the point farthest from the shrimp farming activities.

Sampling

Eight surveys were carried out from June 2014 to February 2016, and a total of 120 samples were collected (i.e., 40 water samples, 40 zooplankton samples, and 40 sediment samples). All samples were taken in duplicate. Water samples were collected 10 cm below the surface using a sterile plastic bag (200 mL). Zooplankton was collected from the surface runoff by towing a plankton net (202 µm mesh size, 0.30 m mouth diameter, 2 m length) provided by a flake collector (10 cm in diameter, 20 cm in length) with 4 circular windows (3 cm in diameter) for 5 min. Each collector was covered with the same mesh as the plankton net to allow water release and concentrate zooplankton (100 mL). Sediment samples were collected with a dredge (jaws 10 cm in diameter, 150 mL volume capacity) below the aqua-sediment interface in the first 5 cm depth. Sediment samples of approximately 100 g each were taken. All samples were placed in an ice chest and transported to the laboratory for analysis within 6 h.

Environmental variables were measured at each site. Temperature and pH were measured with a mercury thermometer and a field potentiometer (Orion). Salinity was measured using a refractometer (Fisher) (salinity range of 0 to 50) with ±0.5 precision. A YSI-50-B oximeter was used to measure dissolved oxygen. All equipment was calibrated prior to use.

Bacteriological analyses

Assessment of the presence or absence of V. parahaemolyticus in the different types of samples was done by PCR using primers for the thermolabile haemolysine (tlh) gene and the methodology described by ^{Kaysner and
DePaola (2004)}. The procedure was carried out as follows. A 100-mL water sample and a 50-mL zooplankton sample were separately filtered through a polyethersulfone membrane (45 mm diameter, 0.2 μm pore size; Supor-200 Pall Corporation) placed on a Millipore base. Each filter was then placed in 50 mL of Alkaline Peptone Water. For sediment analysis, 1 g of each sample was weighed, placed in a flask with 50 mL of Alkaline Peptone Water, and incubated at 35 ºC for 24 h. All samples were analyzed in duplicate. After incubation, 1 mL of the culture medium was extracted from flasks showing turbidity and placed in a 1.5-mL tube for DNA extraction. The tube was vigorously mixed with a vortex mixer (Genie 2) and incubated at 95 ºC for 5 min. The tube was mixed for a second time and placed on ice for 5 min. Finally, the tube was centrifuged at 1,400 rpm for 5 min, and the samples were stored at -20 ºC until use.

Identification of the tlh, tdh, trh, and orf8 genes by conventional PCR

The presence of the tlh gene (species-specific marker for V. parahaemolyticus) in samples with Alkaline Peptone Water was confirmed by PCR. The presence of the tlh gene was determined using a 12.5 µL reaction mix that was prepared with 6.19 µL of deionized water (18 Ω), 2.5 µL of Green-Go-Tag Flexi buffer with MgCl₂ (Promega; Madison, WI, USA), 0.25 µL of dNTPs (10 µL) (Promega Corporation; Madison, WI, USA), 1.25 µL of forward primer (10 µL), 1.25 µL of reverse primer (10 µL), 0.06 µL of Taq polymerase (Axygen) (0.025 U·µL^-1), and 1.0 µL of DNA from the sample that was to be analyzed. The samples that tested positive for the tlh gene were used for detection of toxigenic genes (tdh and trh), using the same component concentrations as the ones used for detection of the tlh gene. The primers used for the tlh, tdh, and trh genes were described by ^{Bej et al. (1999)}. Amplification of the orf8 DNA segment was done with primers described by ^{Myers et al. (2003)}. An Axygen MaxyGene thermocycler (Union City, CA, USA) was used to amplify the tlh gene and its toxigenic genes, with the following amplification conditions: denaturation cycle at 94 ºC for 10 min, 35 cycles at 94 ºC for 1 min, annealing at 58 ºC for 1 min, extension at 72 ºC for 2 min, and final extension at 72 ºC for 10 min. The annealing temperature for the orf8 gene primers was modified to 60 ºC. To visualize the obtained products, electrophoresis on a 1.2% agarose (w/v) gel was carried out with a TAE 1× buffer (40 mM Tris acetate, 1 mM EDTA, pH 8.0) and 0.5 µL of GelRed (10,000X BIOTIUM) in an electrophoresis chamber (Enduro 10.10 horizontal Gel Box, 10 × 10 cm, Labnet) at 90 V for 40 min. Electrophoresis results were observed in a transilluminator with a UVP lamp. Molecular weight markers with size range of 100-3,000 bp (Axygen Biosciences, CA, USA) were used. Control strains were obtained from the Collection of Aquatic Important Microorganisms (CAIM), which was provided by the Research Center for Food and Development in Mazatlán, Sinaloa (Mexico). Positive controls were CAIM 320 for the tlh gene, CAIM 1772 for the tdh and trh genes, and CAIM 1400 for the orf8 gene. A reaction mixture with no DNA was used as a negative control. Only samples with duplicate sequence-specific amplifications were considered positive for V. parahaemolyticus.

Statistical analysis

A one-way analysis of variance (ANOVA) was used to determine significant differences in the presence of the tlh gene among sampling sites. One-way ANOVA was also used to evaluate significant differences in the monthly variation of environmental variables (i.e., temperature, salinity, pH, and dissolved oxygen) and the tlh gene. The analyses were implemented in SigmaPlot 11.0. Spearman’s correlation coefficient was used to determine the relationship between the frequency of the tlh gene indicative of V. parahaemolyticus and the environmental variables. The contribution of environmental parameters to the frequency of the tlh gene indicative of V. parahaemolyticus was analyzed using a principal component analysis, which was carried out with XLSTAT v2017.1. The level of significance was P < 0.05.

Results

Detection of the tlh gene and toxigenic genes

The tlh gene was isolated from all the samples. Frequency was highest during the dry season (June 2014, February 2015, May 2015, and February 2016), followed by the rainy season (September 2014 and 2015). The highest proportion was found in zooplankton samples (65%), compared to the water (57%) and sediment (50%) samples. With respect to sampling sites, the highest tlh gene frequency (37%) occurred at site 4, but it was not significantly different from frequencies at the other sites (P = 0.752) (Table 1).

Table 1 Presence of the tlh gene indicative of Vibrio parahaemolyticus, and toxigenic and pandemic genes in environmental samples from Caimanero Lagoon. 0 = not detected.

		Water				Zooplankton				Sediment				Total
Sampling	Site	tlh	tdh	trh	orf8	tlh	tdh	trh	orf8	tlh	tdh	trh	orf8	tlh	tdh	trh	orf8
June 2014	1	+	-	-	+	+	-	-	-	+	+	-	-	3	1	0	1
	2	0				+	-	-	-	+	-	-	+	2	0	0	1
	3	+	-	-	+	0				+	-	-	-	2	0	0	1
	4	+	-	-	-	+	-	-	-	0				2	0	0	0
	5	+	-	-	-	+	-	-	-	+	-	-	-	3	0	0	0
September 2014	1	0				0				0				0
	2	0				0				0				0
	3	0				+	+	-	-	0				1	1	0	0
	4	0				+	+	-	-	0				1	1	0	0
	5	0				0				0				0
November 2014	1	0				+	-	-	-	0				1	0	0	0
	2	+	-	-	+	+	-	-	-	+	-	-	+	3	0	0	2
	3	0				+	-	-	-	0				1	0	0	0
	4	+	-	-	-	+	-	-	-	+	-	-	-	3	0	0	0
	5	0				+	-	-	-	0				1	0	0	0
February 2015	1	+	-	-	-	+	-	-	-	+	-	-	-	3	0	0	0
	2	+	-	-	-	+	-	-	-	+	-	-	-	3	0	0	0
	3	+	-	-	+	+	-	-	+	+	-	-	-	3	0	0	2
	4	+	-	-	-	+	-	-	-	+	-	-	-	3	0	0	0
	5	+	-	-	-	+	-	-	+	+	-	-	-	3	0	0	1
May 2015	1	+	-	-	-	0				+	-	-	-	2	0	0	0
	2	+	-	-	-	+	-	-	-	+	-	-	-	3	0	0	0
	3	+	-	-	-	+	-	-	-	0				2	0	0	0
	4	-	-	-	-	+	-	-	-	0				1	0	0	0
	5	+	-	-	-	+	-	-	-	+	-	-	-	3	0	0	0
September 2015	1	0				0				0				0
	2	0				0				0				0
	3	0				0				+	-	-	-	1	0	0	0
	4	0				0				0				0
	5	0				0				+	-	-	-	1	0	0	0
November 2015	1	0				+	-	-	-	0				1	0	0	0
	2	+	-	-	-	0				0				1	0	0	0
	3	+	-	-	-	+	-	-	-	0				2	0	0	0
	4	+	-	-	-	0				+	-	-	-	2	0	0	0
	5	0				0				+	-	-	-	1	0	0	0
February 2016	1	+	-	+	-	0				0				1	0	1	0
	2	+	-	+	-	+	-	-	-	0				2	0	1	0
	3	+	-	+	-	+	+	-	-	0				2	1	1	0
	4	+	-	-	-	+	+	-	-	+	-	-	-	3	1	0	0
	5	+	-	-	-	+	+	+	-	+	-	-	-	3	1	1	0
	Total	23	0	3	4	26	5	1	2	20	1	0	2	69	6	4	8

The tdh and trh toxigenic genes were detected in zooplankton samples collected in September 2014 (sites 3 and 4) and February 2016 (sites 3-5). The trh gene was detected only in water samples collected in February 2016 (sites 1-3) (Table 1). The tdh gene was not detected in water, but the trh and orf8 genes were found in 13% (3/23) and 17% (4/23) of the positive samples, respectively. In zooplankton, tdh, trh, and orf8 were detected in 19% (5/26), 4% (1/26), and 8% (2/26) of the samples, respectively. In the sediment, tdh was detected in 5% (1/20) of the samples and orf8 in 10% (1/20) of the positive samples, but trh was not detected.

Environmental parameters and correlation with the tlh gene

Enviromental variables showed temporal variations in Caimanero Lagoon (Table 2). Seawater temperature varied between 24.7 and 31.1 ºC. Values for pH varied between 7.1 and 9.4, with no significant differences. Salinity was high in June 2014 (mean = 41.20), with significant differences (P < 0.05) between all months except for May 2015 and February 2016. Dissolved oxygen was variable, trending between 4.6 and 13.8 mg·L^-1. In May 2015, dissolved oxygen concentration was high (mean = 10.10 mg·L^-1) and significantly different (P < 0.05) from concentrations in September 2014 and February and September 2015.

Table 2 Mean values (±SD) for environmental parameters in Caimanero Lagoon.

Environmental parameters	2014			2015				2016
Environmental parameters	June	September	November	February	May	September	November	February
Temperature (ºC)	31.1 ± 1.8^ab	31.8 ± 1.1^b	27.3 ± 1.3^ab	27.7 ± 1.1^ab	24.7 ± 2.4^a	30.5 ± 1.3^ab	24.8 ± 3.1^a	26.0 ± 4.8^ab
Salinity	41.2 ± 18.8^b	10.0 ± 7.1^ac	11.4 ± 6.0^ac	22.2 ± 7.3^ac	31.2 ± 13.3^b	8.0 ± 5.7 ^a	18.6 ± 6.8^ac	27.8 ± 6.3^bc
pH	8.5 ± 0.3^a	7.7 ± 0.3^a	8.5 ± 0.7 ^a	8.3 ± 0.3^a	8.0 ± 0.3^a	7.7 ± 0.4ª	8.5 ± 0.4^a	8.0 ± 0.5^a
Dissolved Oxigen (mg·L^-1)	7.5 ± 1.1^ab	5.8 ± 0.6^a	6.9 ± 0.9 ^ab	5.6 ± 0.2^a	10.1 ± 2.6^b	5.9 ± 0.7 ^a	7.9 ± 1.2 ^ab	8.1 ± 2.5 ^ab

^{a, b}Means with different letters are significantly different (P < 0.05) between seasons.

A principal component analysis was used to analyze the contribution of environmental parameters to the presence of the tlh gene in all the samples from the lagoon. The relation between environmental parameters and the tlh gene explained 69.59% of total variance. Salinity accounted for 15.78% of the variability in the presence of the tlh gene, pH accounted for 31.45%, dissolved oxygen accounted for 37.55%, and temperature accounted for 15.21%. Salinity levels were significantly associated with the presence of the tlh gene (Fig. 1). The environmental parameters considered in this study to possibly affect the presence or absence of V. parahaemolyticus are listed in Table 3. The presence of the bacterium in the samples was significantly correlated with salinity, but no correlation was observed between the tlh gene and temperature (Table 3).

Figure 1 Principal component analysis of the environmental parameters affecting the presence of the tlh gene. Red vectors indicate environmental parameters (S = salinity, T = temperature [ºC], DO = dissolved oxygen [mg·L^-1]). Blue vectors indicate presence of Vibrio parahaemolyticus (tlh) in all samples (water, sediments, and zooplankton). Variables with vectors projecting on the same plane were considered to be positively correlated.

Table 3 Spearman correlation between the tlh gene and the environmental parameters at the different sampling sites (P < 0.05).

Site	Temperature (ºC)	Salinity	pH	Dissolved oxygen (mg·L^-1)
1	0.018 (P < 0.963)	0.794 (P < 0.048)	0.482 (P < 0.302)	-0.441 (P < 0.302)
2	-0.510 (P < 0.236)	0.505 (P < 0.267)	0.566 (P < 0.200)	0.359 (P < 0.444)
3	-0.235 (P < 0.582)	0.726 (P < 0.058)	0.848 (P < 0.011)	0.183 (P < 0.665)
4	-0.346 (P < 0.389)	0.222(P < 0.619)	0.321 (P < 0.462)	-0.012 (P < 0.977)
5	-0.350 (P < 0.389)	0.760 (P < 0.037)	0.100 (P < 0.840)	0.250 (P < 0.536)

Discussion

The distribution of the tlh gene indicative of V. parahaemolyticus and its relation to environmental parameters in the coastal lagoons in northwest Mexico are little known. The presence of the tlh gene in Caimanero Lagoon was detected throughout the survey. It was detected with less frequency at site 1 (water entry to the lagoon system), which was not affected by aquaculture activities or major salinity fluctuations owing to its geographic location. The lowest tlh gene frequency in Caimanero Lagoon was recorded in September, when heavy rainfall caused an abrupt decrease in salinity (salinity = 8). These results suggest that V. parahaemolyticus can be affected by low salinity.

Several studies have shown that when salinity decreases during the rainy season in a tropical zone, the concentration of V. parahaemolyticus increases (^{Reyes-Velázquez et al. 2010}, ^{Machado and Bordalo 2016}). However, in this study the frequency of V. parahaemolyticus was higher during the dry season. ^{Collin and Rehnstam-Holm (2011)} obtained similar results, as they found V. parahaemolyticus in 73.2% of their samples at the end of the dry season. ^{Flores-Primo et al. (2014)} observed high densities of the tlh gene in oysters during the dry season. ^{Deepanjali et al.
(2005)} observed that water temperature in the tropical coastal regions of India was always optimal and did not significantly affect V. parahaemolyticus. ^{Esteves et al.
(2015)} indicated that, in a Medetirranean coastal lagoon, salinity was crucial for the development of Vibrio, compared to small changes in temperature. In the present study, temperature did not correlate with the presence of the tlh gene by site because there were little temperature variations in the lagoon. Similar results were reported by ^{Turner et
al. (2014)}, who showed that, for plankton, the tlh gene in V. parahaemolyticus did not correlate with temperature. ^{Whitaker et al. (2010)} reported that V. parahaemolyticus grows best when pH is neutral; however, ^{Parveen et al. (2008)} found low correlation between V. parahaemolyticus and this parameter (r² = 0.3514, P < 0.085). In the present study, a positive correlation between pH and the presence of the tlh gene was found only for site 3. Variations in pH were normal in this study; therefore, pH could not atypically effect the tlh gene.

The highest tlh gene frequency was detected in zooplankton. Several studies have also found higher frequencies of the tlh gene in zooplankton than in water (^{Baffone et al.
2006}, ^{Turner et al. 2009}, ^{Caburlotto et al. 2010}, ^{Johnson et al. 2010}, ^{Martinez-Urtaza et al. 2012}, ^{Rehnstam-Holm et al. 2014}). Vibrio parahaemolyticus can survive in sediments during the coldest months of the year, incorporating itself back into the water column when temperature rises in the summer (^{DePaola et al. 1994}, ^{Fukushima and Seki 2004}, ^{Böer et
al. 2013}). However, Caimanero Lagoon is in a tropical zone where temperature variations are small, and this is why V. parahaemolyticus was detected throughout the study period. The results of the present study are consistent with the findings by ^{Johnson et al. (2010)} and ^{Vezzulli et al. (2013)}.

The tdh gene was detected at a higher frequency in zooplankton taken from sites affected by aquaculture activity. The presence of pathogenic genes in this study was low (i.e., in less than 10% of the samples), and previous studies in this area have reported similar results (^{Cabanillas-Beltrán et al. 2006}, ^{Velasco
2007}, ^{Sánchez 2016}). However, ^{Velazquez-Roman et al. (2012)} and ^{Hernández-Díaz et al. (2015)} respectively reported 52.0% and 65.3% of pathogenic genes in strains that were isolated from environmental samples taken from coastal areas in Sinaloa. This increase in the percentage of pathogenic genes was probably due to the high number of samples analyzed and to the selective isolation of V. parahaemolyticus.

^{Nasu et al. (2000)} indicated that serotypes O3:K6 produce tdh and enconde a single orf8 gene; however, we found samples that tested positive for the orf8 gene but negative for the tdh gene. Likewise, other studies have reported samples that tested positive for the tlh gene (species-specific), negative for the toxigenic genes (tdh, trh), and positive for the gene encoding the serotype O3:K6 (orf8) (^{Nair et al. 2007}, ^{Kam et al.
2008}, ^{Velazquez-Roman et al. 2012}, ^{Mala et al. 2016}). ^{Hara-Kudo et al. (2003)} found tdh-negative and O3:K6-positive strains and suggested that these strains may have been variants that diverged from the ancestor of the present pandemic strains, which may have lost the tdh gene as they adapted to the environment and thus lost their virulence. On the other hand, ^{Velazquez-Roman et al.
(2014)} mentioned that in some countries of the Americas there were reported cases of gastroenteritis due to pandemic strains of O3:K6 and its serovariants.

The years 2014 and 2015 were affected by an El Niño event, with atypical changes in temperature and precipitation in September 2014 (228.0 mm) and September 2015 (474.5 mm), indicating salinity variations at almost every site in the lagoon. Enviromental changes caused by climatic events such as El Niño have a direct impact on Vibrio populations because of the increase in temperature and changes in the ecology and hydrology of the systems (^{Ceccarelli and Colwell 2014}). In the present study, water temperature in Caimanero Lagoon fluctuated slightly, but salinity showed the highest fluctuation and was the most important factor determining the presence of the tlh gene. These results clearly indicate that flood events can strongly affect V. parahaemolyticus abundance. This is the first time that an abrupt decrease in V. parahaemolyticus abundance following the rainy season and the concomitant decrease in salinity has been recorded in situ.

In conclusion, this study establishes the importance of environmental parameters affecting the distribution and presence of the tlh gene indicative of V. parahaemolyticus. Our results also indicate the optimal niches for the survival of this species and identify the effects of changes in salinity due to rainfall on the presence of the tlh gene, highlighting that a single environmental parameter alone should not be investigated to determine the presence and distribution of V. parahaemolyticus. The results confirm that the ecology of V. parahaemolyticus varies with respect to geographic locations. The presence of the pathogenic tdh and trh genes and the orf8 gene suggests that constant health surveillance is needed to prevent local public health problems.

Acknowledgments

This work was supported by the National Institute of Technology of Mexico (project no. 6114.17-P), the National Council for Science and Technology (Mexico, grant no. 1395601), and project INFR-2015/251448. The authors thank Diana Sánchez-Zambrano and Carmen Bolán for their assistance.

References

Ahumada-Santos YP, Báez-Flores ME, Díaz-Camacho SP, Uribe-Beltrán MJ, López-Angulo G, Vega-Aviña R, Chávez-Duran FA, Montes-Avila J, Carranza-Díaz O, Möder M, et al. 2014. Spatiotemporal distribution of the bacterial contamination of agricultural and domestic wastewater discharged to a drainage ditch (Sinaloa, Mexico) = Distribución espaciotemporal de la contaminación bacteriana del agua residual agrícola y doméstica descargada a un canal de drenaje (Sinaloa, México). Cienc. Mar. 40(4): 277-289. https://doi.org/10.7773/cm.v40i4.2456 [ Links ]

Baffone W, Tarsi R, Pane L, Campana R, Repetto B, Mariottini GL, Pruzzo C. 2006. Detection of free-living and plankton-bound vibrios in coastal waters of the Adriatic Sea (Italy) and study of their pathogenicity-associated properties. Environ. Microbiol. 8(7): 1299-1305. https://doi.org/10.1111/j.1462-2920.2006.01011.x [ Links ]

Bej AK, Patterson DP, Brasher CW, Vickery MCL, Jones DD, Kaysner CA. 1999. Detection of total and hemolysin-producing Vibrio parahaemolyticus in shellfish using multiplex PCR amplification of tl, tdh and trh. J. Microbiol. Methods 36(3): 215-225. https://doi.org/10.1016/s0167-7012(99)00037-8 [ Links ]

Beltrán-Pimienta R, Retamoza-Leyva S. 2003. Evaluación de uso de purina en la captura de camarón en la laguna El Caimanero, Sinaloa, México. Instituto Nacional de la Pesca. Secretaría de Agricultura, Ganadería, Desarrollo Rural, Pesca y Alimentación. Sinaloa, México, 21 pp. [ Links ]

Böer SI, Heinemeyer EA, Luden K, Erler R, Gerdts G, Janssen F, Brennholt N. 2013. Temporal and spatial distribution patterns of potentially pathogenic Vibrio spp. at recreational beaches of the German North Sea. Microb. Ecol. 65(4): 1052-1067. https://doi.org/10.1007/s00248-013-0221-4 [ Links ]

Cabanillas-Beltrán H, Llausás-Magaña E, Romero R, Espinoza A, García-Gasca A, Nishibuchi M, Ishibashi M, Gomez-Gil B. 2006. Outbreak of gastroenteritis caused by the pandemic Vibrio parahaemolyticus O3:K6 in Mexico. FEMS Microbiol. Lett. 265(1): 76-80. https://doi.org/10.1111/j.1574-6968.2006.00475.x [ Links ]

Caburlotto G, Haley BJ, Lleò MM, Huq A, Colwell RR. 2010. Serodiversity and ecological distribution of Vibrio parahaemolyticus in the Venetian Lagoon, Northeast Italy. Environ. Microbiol. Rep. 2(1): 151-157. https://doi.org/10.1111/j.1758-2229.2009.00123.x [ Links ]

Cariani A, Piano A, Consolandi C, Severgnini M, Castiglioni B, Caredda G, Candela M, Serratore P, De Bellis G, Tinti F. 2012. Detection and characterization of pathogenic vibrios in shellfish by a Ligation Detection Reaction-Universal Array approach. Int. J. Food Microbiol. 153(3): 474-482. https://doi.org/10.1016/j.ijfoodmicro.2011.11.010 [ Links ]

Ceccarelli D, Colwell RR. 2014. Vibrio ecology, pathogenesis, and evolution. Front. Microbiol. 5:256. https://doi.org/10.3389/fmicb.2014.00256 [ Links ]

Chung-Saint L, Tser-Sheng L, Din-Yuan Y, Yi-Cheng Su, Yung-Hsiang T. 2016. Identification of Vibrio parahaemolyticus in seafood by multiplex PCR. J. Aquatic Food Product. Technol. 25(8): 1301-1310. https://doi.org/10.1080/10498850.2015.1056864 [ Links ]

Collin B, Rehnstam-Holm AS. 2011. Occurrence and potential pathogenesis of Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus on the South Coast of Sweden. FEMS Microbiol. Ecol. 78(2): 306-313. https://doi.org/10.1111/j.1574-6941.2011.01157.x [ Links ]

De la Lanza G, Rodríguez Medina M. 1990. Regional Characterization of the Caimanero Lagoon, Sinaloa Mexico, through some geochemical variables = Caracterización regional de la Laguna de Caimanero, Sinaloa, México. Cienc. Mar. 16(3): 27-44 https://doi.org/10.7773/cm.v16i3.701 [ Links ]

Deepanjali A, Kumar HS, Karunasagar I, Karunasagar I. 2005. Seasonal variation in abundance of total and pathogenic Vibrio parahaemolyticus bacteria in oysters along the southwest coast of India. Appl. Environ. Microbiol. 71(7): 3575-3580. https://doi.org/10.1128/aem.71.7.3575-3580.2005 [ Links ]

DePaola A, Capers GM, Alexander D. 1994. Densities of Vibrio vulnificus in the intestines of fish from the U.S. Gulf Coast. App. Enviro. Microb. 60(3): 984-988. [ Links ]

Esteves K, Hervio-Heath D, Mosser T, Rodier C, Tournoud MG, Jumas-Bilak E, Colwell RR, Monfort P. 2015. Rapid proliferation of Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae during freshwater flash floods in French Mediterranean coastal lagoons. Appl. Environ. Microbiol. 81 (21): 7600-7609. https://doi.org/10.1128/aem.01848-15 [ Links ]

[FAO/WHO] Food and Agriculture Organization of the United Nations/World Health Organization. 2011. Risk assessment of Vibrio parahaemolyticus in seafood: Interpretative summary and technical report. Microbiological Risk Assessment Series No. 16. [Accessed 12 June 2017] FAO, Rome. http://apps.who.int/iris/bitstream/10665/44566/1/9789241548175_eng.pdf [ Links ]

Flores-Primo A, Pardío-Sedas V, Lizarrága-Partida L, López-Hernández K, Uscanga-Serrano R, Flores-Hernández R. 2014. Seasonal abundance of total and pathogenic Vibrio parahaemolyticus isolated from American oysters harvested in Mandinga Lagoon system, Veracruz, Mexico: Implications for food safety. J. Food Prot. 77(7): 1069-1077. https://doi.org/10.4315/0362-028x.jfp-13-482 [ Links ]

Fukushima H, Seki R. 2004. Ecology of Vibrio vulnificus and Vibrio parahaemolyticus in brackish environments of the Sada River in Shimane Prefecture, Japan. FEMS Microbiol. Ecol. 48(2): 221-229. https://doi.org/10.1016/j.femsec.2004.01.009 [ Links ]

García K, Bastías R, Higuera G, Torres R, Mellado A, Uribe P, Espejo RT. 2013. Rise and fall of pandemic Vibrio parahaemolyticus serotype O3:K6 in southern Chile. Environ. Microbiol. 15(2): 527-534. https://doi.org/10.1111/j.1462-2920.2012.02883.x [ Links ]

Gavilán RG, Martínez-Urtaza J. 2011. Factores ambientales vinculados con la aparición y dispersión de las epidemias de Vibrio en América del Sur. Rev. Peru. Med. Exp. Salud Pública 28(1): 109-115. https://doi.org/10.1590/s1726-46342011000100017 [ Links ]

Givens CE, Bowers JC, DePaola A, Hollibaugh JT, Jones JL. 2014. Occurrence and distribution of Vibrio vulnificus and Vibrio parahaemolyticus - potential roles for fish, oyster, sediment and water. Lett. Appl. Microbiol. 58(6): 503-510. https://doi.org/10.1111/lam.12226 [ Links ]

Hara-Kudo Y, Sugiyama K, Nishibuchi M, Chowdhury A, Yatsuyanagi J, Ohtomo Y, Saito A, Nagano H, Nishina T, Nakagawa H, et al. 2003. Prevalence of pandemic thermostable direct hemolysin-producing Vibrio parahaemolyticus O3:K6 in seafood and the coastal environment in Japan. Appl. Environ. Microbiol. 69(7): 3883-3891. https://doi.org/10.1128/aem.69.7.3883-3891.2003 [ Links ]

Hernández-Díaz LJ, Leon-Sicairos N, Velazquez-Roman J, Flores-Villaseñor H, Guadron-Llanos AM, Martinez-Garcia JJ, Vidal JE, Canizalez-Roman A. 2015. A pandemic Vibrio parahaemolyticus O3:K6 clone causing most associated diarrhea cases in the Pacific Northwest coast of Mexico. Front. Microbiol. 6(221): 1-11. https://doi.org/10.3389/fmicb.2015.00221 [ Links ]

Johnson CN. 2013. Fitness Factors in vibrios: A Mini-review. Microb. Ecol. 65(4): 826-851. [ Links ]

Johnson CN, Flowers AR, Noriea NF, Zimmerman AM, Bowers JC, DePaola A, Grimes DJ. 2010. Relationships between environmental factors and pathogenic vibrios in the northern Gulf of Mexico. Appl. Environ. Microbiol. 76(21): 7076-7084 https://doi.org/10.1128/aem.00697-10 [ Links ]

Kam KM, Luey CKY, Parsons MB, Cooper KLF, Nair GB, Alam M, Islam MA, Cheung DTL, Chu YW, Ramamurthy T, et al. 2008. Evaluation and validation of a PulseNet standardized pulsed-field gel electrophoresis protocol for subtyping Vibrio parahaemolyticus: An International Multicenter Collaborative study. J. Clin. Microbiol. 46(8): 2766-2773. https://doi.org/10.1128/jcm.00424-08 [ Links ]

Kaysner CA, DePaola A Jr. 2004. BAM: Vibrio. US Food and Drug Administration, Bacteriological Analytical Manual, 8th ed. [Accessed 17 June 2017] Silver Spring (MD). http://www.fda.gov/Food/FoodScienceResearch/LaboratoryMethods/ucm070830.htm [ Links ]

Letchumanan V, Chan KG, Lee LH. 2014. Vibrio parahaemolyticus: a review on the pathogenesis, prevalence, and advance molecular identification techniques. Front. Microbiol. 5(705): 1-13. https://doi.org/10.3389/fmicb.2014.00705 [ Links ]

López-Hernández KM, Pardío-Sedas VT, Lizárraga-Partida L, Williams JJ, Martínez-Herrera D, Flores-Primo A, Uscanga-Serrano R, Rendón-Castro K. 2015. Environmental parameters influence on the dynamics of total and pathogenic Vibrio parahaemolyticus densities in Crassostrea virginica harvested from Mexico’s Gulf coast. Mar. Pollut. Bull. 91(1): 317-329. https://doi.org/10.1016/j.marpolbul.2014.11.015 [ Links ]

Machado A, Bordalo AA. 2016. Detection and quantification of Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus in coastal waters of Guinea-Bissau (West Africa). Ecohealth 13(2): 339-349. https://doi.org/10.1007/s10393-016-1104-1 [ Links ]

Mala W, Alam M, Angkititrakul S, Wongwajana S, Lulitanond V, Huttayananont S, Kaewkes W, Faksri K, Chomvarin C. 2016. Serogroup, virulence, and molecular traits of Vibrio parahaemolyticus isolated from clinical and cockle sources in northeastern Thailand. Infect., Genet. Evol. 39: 212-218. https://doi.org/10.1016/j.meegid.2016.01.006 [ Links ]

Martinez-Urtaza J, Blanco-Abad V, Rodriguez-Castro A, Ansede-Bermejo J, Miranda A, Rodriguez-Alvarez MX. 2012. Ecological determinants of the occurrence and dynamics of Vibrio parahaemolyticus in offshore areas. ISME J. 6(5): 994-1006. http://dx.doi.org/10.1038/ismej.2011.156 [ Links ]

Martinez-Urtaza J, Powell A, Jansa J, Castro RJL, Paz MO, García CM, Zamora LMJ, Pousa A, Faraldo VMJ, Trinanes J, et al. 2016. Epidemiological investigation of a foodborne outbreak in Spain associated with US West Coast genotypes of Vibrio parahaemolyticus. Springerplus 5(87): 1-8. https://doi.org/10.1186/s40064-016-1728-1 [ Links ]

Miyoshi SI. 2013. Extracellular proteolytic enzymes produced by human pathogenic Vibrio species. Front. Microbiol. 4: 339 https://doi.org/10.3389/fmicb.2013.00339 [ Links ]

Myers ML, Panicker G, Bej AK. 2003. PCR detection of a newly emerged pandemic Vibrio parahaemolyticus O3:K6 pathogen in pure cultures and seeded waters from the Gulf of Mexico. Appl. Environ. Microbiol. 69(4): 2194-2200. https://doi.org/10.1128/aem.69.4.2194-2200.2003 [ Links ]

Nair GB, Ramamurthy T, Bhattacharya SK, Dutta B, Takeda Y, Sack DA. 2007. Global dissemination of Vibrio parahaemolyticus serotype O3:K6 and its serovariants. Clin. Microbiol. Rev. 20(1): 39-48. https://doi.org/10.1128/cmr.00025-06 [ Links ]

Nasu H, Iida T, Sugahara T, Yamaichi Y, Park KS, Yokoyama K, Makino K, Shinagawa H, Honda T. 2000. A filamentous phage associated with recent pandemic Vibrio parahaemolyticus O3:K6 strains. J. Clin. Microbiol. 38(6): 2156-2161. [ Links ]

Ottaviani D, Leoni F, Rocchegiani E, Mioni R, Costa A, Virgilio S, Serracca L, Bove D, Canonico C, Di Cesare A, et al. 2013. An extensive investigation into the prevalence and the genetic and serological diversity of toxigenic Vibrio parahaemolyticus in Italian marine coastal waters. Environ. Microbiol. 15(5): 1377-1386. https://doi.org/10.1111/j.1462-2920.2012.02839.x [ Links ]

Paranjpye R, Hamel OS, Stojanovski A, Liermann M. 2012. Genetic diversity of clinical and environmental Vibrio parahaemolyticus strains from the Pacific northwest. Appl. Environ. Microbiol. 78(24): 8631-8638. https://doi.org/10.1128/aem.01531-12 [ Links ]

Parte AC. 2018. LPSN-List of prokaryotic names with Standing in Nomenclature (bacterio.net), 20 years on. Int. J. Syst. Evol. Microbiol. 68: 1825-1829. http://dx.doi.org/10.1099/ijsem.0.002786 [ Links ]

Parveen S, Hettiarachchi KA, Bowers JC, Jones JL, Tamplin ML, McKay R, Beatty W, Brohawn K, DaSilva LV, DePaola A. 2008. Seasonal distribution of total and pathogenic Vibrio parahaemolyticus in Chesapeake Bay oysters and waters. Int. J. Food Microbiol. 128(2): 354-361. https://doi.org/10.1016/j.ijfoodmicro.2008.09.019 [ Links ]

Ramsar. 2007. Ramsar sites information Service. Laguna Huizache-Caimanero. [Accessed 06 October 2016] [Ramsar Secretariat]. http://rsis.ramsar.org/ris/1689. [ Links ]

Rehnstam-Holm AS, Atnur V, Godhe A. 2014. Defining the niche of Vibrio parahaemolyticus during pre- and post-monsoon seasons in the coastal Arabian Sea. Microb. Ecol. 67(1): 57−65. http://dx.doi.org/10.1007/s00248-013-0311-3 [ Links ]

Reyes-Velázquez C, Castañeda-Chávez MR, Landeros-Sánchez C, Galaviz-Villa I, Lango-Reynoso F, Minguez-Rodríguez MM, Nikolskii-Gavrilov I. 2010. Pathogenic vibrios in the oyster Crassostrea virginica in the lagoon system of Mandinga, Veracruz, Mexico. Hidrobiológica 20(3): 238-245. [ Links ]

Romero-Beltrán E, Aldana-Flores G, Muñoz-Mejia EM, Medina -Osuna PM, Valdéz-Ledón P, Bect-Valdez JA, Gaspar-Dillanes MT, Huidobro-Campos L, Romero-Correa A, et al. 2014. Estudio de la calidad del agua y sedimento en lagunas costeras del estado de Sinaloa, México. Instituto Nacional de la Pesca, Secretaría de Agricultura, Ganadería, Desarrollo Rural, Pesca y Alimentación. Mazatlán, Sinaloa, México. [ Links ]

Sánchez ZD. 2016. Incidencia, distribución espacio-temporal y toxigenia de serovariedades de Vibrio parahaemolyticus, en camarón blanco (Litopenaeus vannamei) de la laguna Caimanero, Sinaloa, México. MSc thesis. Instituto Tecnológico de Mazatlán, Mazatlán, Sinaloa, Mexico. [ Links ]

Turner JW, Good B, Cole D, Lipp EK. 2009. Plankton composition and environmental factors contribute to Vibrio seasonality. ISME J. 3(39): 1082-1092. https://doi.org/10.1038/ismej.2009.50 [ Links ]

Turner JW, Malayil L, Guadagnoli D, Cole D, Lipp EK. 2014. Detection of Vibrio parahaemolyticus, Vibrio vulnificus and Vibrio cholerae with respect to seasonal fluctuations in temperature and plankton abundance. Environ. Microbiol. 16(4): 1019-1028. https://doi.org/10.1111/1462-2920.12246 [ Links ]

Velasco API. 2007. Variación espacio-temporal de Vibrio parahaemolyticus total y toxigénico en el sistema lagunar Huizache-Caimanero, Sinaloa, México. MSc. thesis, Centro de Investigación en Alimentación y Desarrollo, Mazatlán, Sinaloa, Mexico. [ Links ]

Velazquez-Roman J, León-Sicairos N, Flores-Villaseñor H, Villafaña-Rauda S, Canizalez-Roman A. 2012. Association of Pandemic Vibrio parahaemolyticus O3:K6 present in the coastal environment of Northwest Mexico with cases of recurrent diarrhea between 2004 and 2010. Appl. Environ. Microbiol. 78(6): 1794-1803. https://doi.org/10.1128/aem.06953-11 [ Links ]

Velazquez-Roman J, León-Sicairos N, Hernández-Díaz L de J, Canizalez-Roman A. 2014. Pandemic Vibrio parahaemolyticus O3:K6 on the American continent. Front. Cell. Infect. Microbiol. 3: 1-14. https://doi.org/10.3389/fcimb.2013.00110 [ Links ]

Vezzulli L, Colwell RR, Pruzzo C. 2013. Ocean warming and spread of pathogenic vibrios in the aquatic environment. Microb. Ecol. 65(4): 817-825. https://doi.org/10.1007/s00248-012-0163-2 [ Links ]

Wang R, Zhong Y, Gu X, Yuan J, Saeed AF, Wang S. 2015. The pathogenesis, detection, and prevention of Vibrio parahaemolyticus. Front. Microbiol. 6: 1-13. https://doi.org/10.3389/fmicb.2015.00144 [ Links ]

Whitaker WB, Parent MA, Naughton LM, Richards GP, Blumerman SL, Boyd EF. 2010. Modulation of responses of Vibrio parahaemolyticus O3:K6 to pH and temperature stresses by growth at different salt concentrations. Appl. Environ. Microbiol. 76(14): 4720-4729. https://doi.org/10.1128/aem.00474-10 [ Links ]

Xu F, Ilyas S, Hall JA, Jones SH, Cooper VS, Whistler CA. 2015. Genetic characterization of clinical and environmental Vibrio parahaemolyticus from the Northeast USA reveals emerging resident and non-indigenous pathogen lineages. Front. Microbiol. 6. https://doi.org/10.3389/fmicb.2015.00272 [ Links ]

Zhang L, Orth K. 2013. Virulence determinants for Vibrio parahaemolyticus infection. Curr. Opin. Microbiol. 16(1): 70-77. https://doi.org/10.1016/j.mib.2013.02.002 [ Links ]

Received: March 01, 2017; Accepted: February 01, 2018

^*Corresponding author. E-mail: irasemaluis@uas.edu.mx

This is an open-access article distributed under the terms of the Creative Commons Attribution License