Bacteriological and physico-chemical assessment of wastewater in different region of Tunisia: impact on human health

<p>Abstract</p> <p>Background</p> <p>In many parts of the world, health problems and diseases have often been caused by discharging untreated or inadequately treated wastewater. In this study, we aimed to control physico-chemical parameters in wastewater samples. Also, microbiological analyses were done to reveal <it>Salmonella </it>strains and each <it>Escherichia coli </it>(<it>E.coli</it>) pathotype.</p> <p>Findings</p> <p>Sixty wastewater samples were collected from fifteen different regions of Tunisia. All physico-chemical parameters (pH, residual free chlorine, total suspended solids, biological oxygen demand, and chemical oxygen demand) were evaluated.</p> <p>For microbiological analyses, samples were filtered to concentrate bacteria. DNA was extracted by boiling and subjected to polymerase chain reaction (PCR) using different pairs of primers.</p> <p>The mean pH values recorded for the sampling point were above the WHO pH tolerance limit. The total suspended solids (TSS) concentrations varied between 240 mg/L and 733 mg/L in entrance points and between 13 mg/L and 76 mg/L in exit points. In entrance points, the studied wastewater has an average COD concentration that varied between 795 mg/mL to 1420 mg/mL. Whereas, BOD concentration of the wastewater ranged between 270 mg/L to 610 mg/L. In exit points, COD concentration varied between 59 mg/L and 141 mg/L, whereas BOD concentration ranged from 15 mg/L to 87 mg/L.</p> <p>The bacteriological control of wastewaters showed that, in entrance points, <it>Escherichia coli </it>(<it>E.coli</it>) was detected at the rate of 76.6%. Three <it>E.coli </it>pathotypes were found: ETEC (53.3%), EAEC (16.6%) and EIEC (6.6%).</p> <p>Concerning the ETEC isolated strains, 8 of 16 (50%) have only the heat-labile toxin gene, 5 of 16 (31.2%) present only the heat-stable toxin gene and 3 of 16 (18.7%) of strains possess both heat-labile toxin gene and heat-stable toxin gene. In exist point, the same pathotypes were found but all detected ETEC strains present only the "est" gene.</p> <p>Concerning <it>Salmonella </it>isolated strains; percentages of 66.6% and 20% were found in entrance and exit points respectively.</p> <p>Conclusions</p> <p>Wastewaters contain a large amount of pathogenic bacteria that present a real impact on human health. Assessment wastewater treatment stations have to consider in account enterobacterial pathogens as potential pathogens that should be correctly controlled.</p

Analysis of Vibrio cholerae O139 Bengal isolated from different geographical areas using macrorestriction DNA analysis

Vibrio cholerae O139 isolated from different countries, as well as from different locations within a country, were examined using macrorestriction DNA analysis to determine the clonality of the O139 strains. NotI digests of genomic DNA of representative strains from Nepal, India, Bangladesh, China, Thailand, and Malaysia revealed very similar but not identical patterns. Examinations of the banding patterns generated by pulsed-field gel electrophoresis of strains isolated within countries revealed complete homogeneity. These results further reiterate the spread of an identical clone of V. cholerae O139 although it appears that genetic polymorphism among the O139 strains is becoming apparent

Evaluation and Validation of a PulseNet Standardized Pulsed-Field Gel Electrophoresis Protocol for Subtyping Vibrio parahaemolyticus: an International Multicenter Collaborative Study▿

The pandemic spread of Vibrio parahaemolyticus is an international public health issue. Because of the outbreak potential of the organism, it is critical to establish an internationally recognized molecular subtyping protocol for V. parahaemolyticus that is both rapid and robust as a means to monitor its further spread and to guide control measures in combination with epidemiologic data. Here we describe the results of a multicenter, multicountry validation of a new PulseNet International standardized V. parahaemolyticus pulsed-field gel electrophoresis (PFGE) protocol. The results are from a composite analysis of 36 well-characterized V. parahaemolyticus isolates from six participating laboratories, and the isolates represent predominant serotypes and various genotypes isolated from different geographic regions and time periods. The discriminatory power is very high, as 34 out of 36 sporadic V. parahaemolyticus strains tested fell into 34 distinguishable PFGE groups when the data obtained with two restriction enzymes (SfiI and NotI) were combined. PFGE was further able to cluster members of known pandemic serogroups. The study also identified quality measures which may affect the performance of the protocol. Nonadherence to the recommended procedure may lead to high background in the PFGE gel patterns, partial digestion, and poor fragment resolution. When these quality measures were implemented, the PulseNet V. parahaemolyticus protocol was found to be both robust and reproducible among the collaborating laboratories