RESUMO
Although autochthonous vibrio densities are known to be influenced by water temperature and salinity, little is understood about other environmental factors associated with their abundance and distribution. Densities of culturable Vibrio vulnificus containing vvh (V. vulnificus hemolysin gene) and V. parahaemolyticus containing tlh (thermolabile hemolysin gene, ubiquitous in V. parahaemolyticus), tdh (thermostable direct hemolysin gene, V. parahaemolyticus pathogenicity factor), and trh (tdh-related hemolysin gene, V. parahaemolyticus pathogenicity factor) were measured in coastal waters of Mississippi and Alabama. Over a 19-month sampling period, vibrio densities in water, oysters, and sediment varied significantly with sea surface temperature (SST). On average, tdh-to-tlh ratios were significantly higher than trh-to-tlh ratios in water and oysters but not in sediment. Although tlh densities were lower than vvh densities in water and in oysters, the opposite was true in sediment. Regression analysis indicated that SST had a significant association with vvh and tlh densities in water and oysters, while salinity was significantly related to vibrio densities in the water column. Chlorophyll a levels in the water were correlated significantly with vvh in sediment and oysters and with pathogenic V. parahaemolyticus (tdh and trh) in the water column. Furthermore, turbidity was a significant predictor of V. parahaemolyticus density in all sample types (water, oyster, and sediment), and its role in predicting the risk of V. parahaemolyticus illness may be more important than previously realized. This study identified (i) culturable vibrios in winter sediment samples, (ii) niche-based differences in the abundance of vibrios, and (iii) predictive signatures resulting from correlations between environmental parameters and vibrio densities.
Assuntos
Água do Mar/microbiologia , Vibrio parahaemolyticus/fisiologia , Vibrio vulnificus/fisiologia , Alabama , Animais , Proteínas de Bactérias/metabolismo , Toxinas Bacterianas/metabolismo , Meio Ambiente , Sedimentos Geológicos/microbiologia , Proteínas Hemolisinas/metabolismo , Mississippi , Oceanos e Mares , Ostreidae/microbiologia , Reação em Cadeia da Polimerase , Salinidade , Temperatura , Vibrio parahaemolyticus/patogenicidade , Vibrio vulnificus/patogenicidadeRESUMO
AIMS: Two well-characterized Vibrio parahaemolyticus pathogenicity factors - thermostable direct haemolysin (TDH) and TDH-related haemolysin - are produced by strains containing the tdh and trh genes, respectively. Most strains of V. parahaemolyticus contain two nonredundant type III secretion systems (T3SS), T3SS1 and T3SS2, both of which contribute to pathogenicity. Furthermore, a recent study has revealed two distinct lineages of the V. parahaemolyticus T3SS2: T3SS2α and T3SS2ß. The aim of this study was to determine the incidence of these pathogenicity factors in environmental isolates of V. parahaemolyticus. METHODS AND RESULTS: We collected 130 V. parahaemolyticus isolates (TCBS agar) containing tdh and/or trh (determined by colony hybridization) from sediment, oyster and water in the northern Gulf of Mexico and screened them and 12 clinical isolates (PCR and agarose gel electrophoresis) for pathogenicity factors tdh, trh, T3SS1, T3SS2α and T3SS2ß. The majority of potential pathogens were detected in the sediment, including all tdh(-) /trh(+) isolates. T3SS2α components were detected in all tdh(+) /trh(-) isolates and zero of 109 trh(+) isolates. One T3SS2α gene, vopB2, was found in all tdh(+) /trh(-) clinical strains but not in any of the 130 environmental strains. Fluorescence in situ hybridization adapted for individual gene recognition (RING-FISH) was used to confirm the presence/absence of vopB2. T3SS2ß was found in all tdh(-) /trh(+) isolates and in no tdh(+) /trh(-) isolates. CONCLUSIONS: The combination of haemolysins found in each isolate consistently corresponded to the presence and type of T3SS detected. The vopB2 gene may represent a novel marker for identifying increased virulence among strains. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to confirm the presence of T3SS2ß genes in V. parahaemolyticus strains isolated from the Gulf of Mexico and one of the few that examines the distribution and co-existence of tdh, trh, T3SS1, T3SS2α and T3SS2ß in a large collection of environmental strains.
Assuntos
Proteínas Hemolisinas/genética , Vibrio parahaemolyticus/patogenicidade , Animais , Toxinas Bacterianas/genética , Sedimentos Geológicos/microbiologia , Oceanos e Mares , Ostreidae/microbiologia , Reação em Cadeia da Polimerase , Vibrio parahaemolyticus/genética , Vibrio parahaemolyticus/isolamento & purificação , Virulência , Fatores de Virulência/genética , Microbiologia da ÁguaRESUMO
Pathogenic Vibrio parahaemolyticus (Vp) (tdh(+)/trh(+)) represent a small percentage of environmental Vp populations, and very little is known about this subpopulation. Repetitive extragenic palindromic PCR and multilocus sequence analysis revealed heterogeneity among 41 Vp containing thermostable direct hemolysin (tdh) and tdh-related hemolysin (trh) that were isolated from Mississippi coastal environments from October 2006 to April 2007. There was no source-specific sequestering in oysters, water, or sediment.
Assuntos
Toxinas Bacterianas/genética , Crassostrea/microbiologia , Proteínas Hemolisinas/genética , Vibrio parahaemolyticus/genética , Animais , Técnicas de Tipagem Bacteriana , DNA Bacteriano/genética , Sedimentos Geológicos/microbiologia , Mississippi , Filogenia , Análise de Sequência de DNA , Vibrio parahaemolyticus/classificaçãoRESUMO
Vibrio parahaemolyticus is indigenous to coastal environments and a frequent cause of seafood-borne gastroenteritis in the United States, primarily due to raw-oyster consumption. Previous seasonal-cycle studies of V. parahaemolyticus have identified water temperature as the strongest environmental predictor. Salinity has also been identified, although it is evident that its effect on annual variation is not as pronounced. The effects of other environmental factors, both with respect to the seasonal cycle and intraseasonal variation, are uncertain. This study investigated intraseasonal variations of densities of total and pathogenic V. parahaemolyticus organisms in oysters and overlying waters during the summer of 2004 at two sites in the northern Gulf of Mexico. Regression analyses indicated significant associations (P < 0.001) between total V. parahaemolyticus densities and salinity, as well as turbidity in water and in oysters at the Mississippi site but not at the Alabama site. Pathogenic V. parahaemolyticus organisms in Mississippi oyster and water samples were detected in 56% (9 out of 16) and 78% (43 out of 55) of samples, respectively. In contrast, 44% (7 out of 16) of oyster samples and 30% (14 out of 47) of water samples from Alabama were positive. At both sites, there was greater sample-to-sample variability in pathogenic V. parahaemolyticus densities than in total V. parahaemolyticus densities. These data suggest that, although total V. parahaemolyticus densities may be very informative, there is greater uncertainty when total V. parahaemolyticus densities are used to predict the risk of infection by pathogenic V. parahaemolyticus than previously recognized.