Diarrheagenic Escherichia coli pathotypes isolated from children with diarrhea in the Federal Capital Territory Abuja, Nigeria.

INTRODUCTION: Escherichia coli are frequently isolated from diarrheic children in the Federal Capital Territory Abuja, Nigeria, but their virulent properties are not routinely evaluated. Therefore, the etiology of childhood diarrheal disease attributable to diarrheagenic Escherichia coli (DEC) in Abuja, Nigeria remains unknown. METHODOLOGY: Stool specimens from 400 acute diarrheic children between 0 and 60 months of age were studied. E. coli strains isolated were evaluated by polymerase chain reaction (PCR) for nine virulence genes and HEp-2 cell adherence to detect and identify five distinct diarrheagenic E. coli categories. RESULTS: Diarrheagenic E.coli was detected in 51 (12.8%) of the diarrheic children. The observed DEC pathotypes were enteropathogenic E. coli (EPEC) in 18 (4.5%) children, enterotoxigenic E. coli (ETEC) in 16 (4.0%), enteroaggrative E. coli (EAEC) in 8 (2.0%), enterohaemorrhagic E. coli (EHEC) in 6 (1.5%), and enteroinvasive E. coli (EIEC) in 3 (0.8%). Four (1.0 %) EPEC strains with only the eae+ gene that adhered diffusely to HEp-2 cell were identified as atypical EPEC. All the DEC categories except atypical EPEC were identified in children between 6 and 12 months of age. CONCLUSIONS: This study underscores the need for routine evaluation of diarrheic children for virulence properties of infectious DEC. Atypical EPEC are emerging among the DEC pathotypes isolated from childhood acute gastroenteritis in Abuja, Nigeria.

Occurrence of plasmid-mediated quinolone resistance determinants and rmtB gene in Salmonella enterica serovar enteritidis and Typhimurium isolated from food-animal products in Tunisia.

Four hundred and thirty Salmonella isolates, recovered from various food-animal products, were tested for nalidixic acid resistance, plasmid-mediated quinolone resistance, and genetic relationship. One hundred fifteen isolates (113 Salmonella serovar Enteritidis and two Salmonella serovar Typhimurium isolates) of 430 (26.7%) Salmonella isolates exhibited nalidixic acid resistance. Polymerase chain reaction screening for qnrA, qnrB, qnrS, qepA (encoding fluoroquinolones resistance) and rmtB (encoding aminoglycosides resistance) showed that 5 (1.16%) isolates were positive for qnr- and qepA-type genes, and the aac(6')-Ib-cr gene was observed in two (1.7%) Enteritidis isolates concomitantly with qnrA or qnrB. The co-occurrence of qepA and rmtB in one Typhimurium isolate is noteworthy. Pulsed-field gel electrophoresis revealed a high genetic homogeneity of nalidixic-resistant isolates and the persistence of clonal clusters over 4 years in different regions in Tunisia and from various food-animal products. To the best of our knowledge, this is the first report of co-occurrence of qepA and rmtB in a Salmonella strain.

Effects of static magnetic field on cell growth, viability, and differential gene expression in Salmonella.

In the present study, we investigated the effect of exposure to A static magnetic field (SMF) on cell growth, viability, and gene expression of Salmonella enterica subsp. enterica serovar Hadar. Our results indicated that SMF exposure (200 mT, 13 hours) failed to alter cellular growth but induced a decrease of colony-forming units (CFU) between 3 and 6 hours followed by an increase from 6 to 9 hours. The analysis of the differential expression of rpoA, dnaK, katN, and 16S rRNA genes under SMF exposure (200 mT, 10 hours) showed that the expression level of the 16S rRNA mRNA remained stable during the exposure and can thus be used as a reference gene for the analysis on the differential gene expression of Salmonella Hadar. Interestingly, mRNAs of rpoA, katN, and dnaK genes were over-expressed following 10 hours of SMF exposure (200 mT). These data suggest a possible stress response of Salmonella Hadar to static magnetic field.

Etiology of acute diarrhea in children and adults in Tunis, Tunisia, with emphasis on diarrheagenic Escherichia coli: prevalence, phenotyping, and molecular epidemiology.

A total of 271 stool specimens were collected from children (diarrheagenic, n = 115 and control, n = 54) and adults (diarrheagenic, n = 73 and control, n = 29) from Tunis, Tunisia, and processed to detect bacterial enteropathogens, parasites, and viruses. Diarrheagenic Escherichia coli (DEC) were identified by their virulence genes (polymerase chain reaction) and adherence patterns (tissue culture assays). The most frequently isolated enteric pathogens from diarrheagenic children were enterotoxigenic E. coli (ETEC, 32.3%), enteroaggregative E. coli (EAEC, 11.3%), enteroinvasive E. coli (EIEC, (11.3%), adenovirus (10.4%), enterohemorrhagic E. coli (EHEC, 10.4%), and Salmonella spp. (9.5%). For children in the control group, ETEC (37%), EAEC (15%), EHEC (11.1%), and typical enteropathogenic E. coli (EPEC, 11.1%) were the most common enteric pathogens. In adults in the diarrheagenic group, Salmonella spp. (34.2%), ETEC (12.3%), adenovirus (7%), and Shigella spp. (4%) were the most common enteric pathogens. In adults in the control group, ETEC (31%) was the most common enteric pathogen. Multiple pathogens were recovered from 22% of the diarrheagenic children and 7% of the diarrheagenic adults. Escherichia coli strains showed high resistance rates to tetracycline, streptomycin, and beta-lactams. The most frequent combinations were ETEC-rotavirus and ETEC-adenovirus. Pulsed-field gel electrophoresis for DEC indicated a large number of DEC clones (five major clones) persistent in the community reservoir for a considerable period of time that caused diarrhea in the population. This suggests the confluence of small epidemics by clonally related DEC strains circulating in this region.

Trends in Salmonella enterica serotypes isolated from human, food, animal, and environment in Tunisia, 1994-2004.

OBJECTIVE: The present study was conducted to investigate, for the first time in Tunisia, the current trends in Salmonella enterica serotypes in Tunisia (human, food, animal, and environment) which would help to improve the control and prevention of Salmonella infections. METHODS: Data from 1994 to 2004 from the National Centre of Enteropathogenic Bacteria - Pasteur Institute - Tunis, were analysed a total of 16,214 Salmonella isolates that were reported from all over Tunisia and serotyped according to the Kauffman-White scheme. Statistical analysis was done by SPSS v.11.5 software. RESULTS: The isolation rate was decreasing in the human and food categories only. The top three frequently isolated serotypes during the 11-years were: Enteritidis (25.5%), Anatum (14%), and Corvallis (13.2%), indicating Tunisia as an endemic area for these serotypes. Among human isolates, Enteritidis was the most common serotype, accounting for 24% of all isolates. Among nonhuman isolates, Anatum (28%), Enteritidis (69%), and Corvallis (17.3%) were reported as the first common serotypes for food, animal and environmental samples, respectively. Percentage of Salmonella isolates demonstrated a marked pattern of seasonality, increasing in the warm spring months for human, food and animal isolates. Except for environmental isolates which increased in the spring season. Human salmonellosis outbreak by serotypes Mbandaka, Livingstone, and Typhi Vi+ had been reported during the years: 1997, 1999, 2002 and 2004. CONCLUSION: Importance of enhancing the Salmonella surveillance system not only in Tunisia but also in the neighboring countries, and the need to get a better monitoring of trends in serotypes over time which would provide information about emerging serotypes and about the efficacy of prevention and control measures.