Distribution of genes encoding toxins and antibiotic resistance patterns in diarrhoeagenic Escherichia coli isolates in Tehran

Pathogenicity of Escherichia coli can involve a large number of virulence factors, toxins being the most obvious. We assessed the distribution of genes encoding toxins among E. coli isolates from diarrhoeal cases using DNA probes. From 200 isolates, 92 [46.0%] carried genes encoding for toxins, 43.5% of these being multitoxigenic. Enteroaggregative heat- stable enterotoxin was detected in 40 [43.5%] isolates, verotoxin in 38 [41.3%], cytolethal distending toxin in 24 [26.1%], heat- stable enterotoxin in 12 [13.0%] and heat- labile enterotoxin in 10 [10.9%]. Furthermore, 40 strains [70.0%] carried resistance. We conclude that toxigenicity and antibiotic resistance are the main contributing factors leading to the virulence potential of these E. coli isolates

Assessment of GM-CSF receptors by real-time RT-PCR on cell lines expressing high and low affinity receptors and their relation to cytotoxic effect of chimeric protein[StxA1-GM-CSF]

Immunotoxins, which are composed of both the cell targeting and the cell killing moieties are the new approach for targeted therapy of human disease. In all immunotoxins that GM-CSF has been used as cell targeting; only cell lines expressing high affinity receptor have been used for cytotoxicity studies. In the present study, various cell lines expressing high and low affinity receptors were used for assessment of the cytotoxic effect of hybrid chimeric protein. The expression of GM-CSF receptor [GM-CSFR] was quantified by real-time RT- PCR. The cell lines K562 and THP1 expressing high affinity receptor and MC-7, PC-3 and DU145 expressing low affinity receptor were used for this study. The chimeric hybrid protein was found to be toxic for various cell lines used in this investigation and cytotoxicity was more effective in cell lines bearing high affinity receptors. Overall, our results showed that the recombinant hybrid protein could have wide range of application on various cancer cell lines even cells bearing low affinity receptors for GM-CSF

Detection and characterization of verotoxin-producing strains among sorbitol non-fermenting Escherichia coli

The presence of genes for verotoxin 1 and 2 [VT1 and 2] among sorbitol non-fermenting Escherichia coli isolates from diarrhoeal cases was assessed using polymerase chain reaction assay. Of 60 [88%] positive isolates, 37 [62%] harboured VT1 and 23 [38%] both VT1 and VT2. In HeLa cell adherence assay, 48 [71%] isolates exhibited mannose-resistant adherence to HeLa cells. Multidrug resistance was observed in 56 [82%] isolates, with ampicillin, chloramphenicol, streptomycin, sulfamethoxazole-trimethoprim and tetracycline pattern being the most common. There were 13 common and 22 single biochemical phenotypes identified. Isolates belonging to common biochemical phenotypes normally had a similar pattern of adherence and VT production, but differed greatly in their pattern of antibiotic resistance, pointing to a high rate of antibiotic-resistance transfer among these isolates

Characterization of verotoxin producing strains of enteropathogenic Escherichia coli [EPEC] from children with diarrhea: effects of the toxin on rabbit intestine

249 enteropathogenic Escherichia coli [EPEC] strains from faecal samples of 90 children with diarrhoea were examined for verotoxin [VT] production. Polymyxin B extracts of 61 strains belonging to 9 serogroups from 35 children produced various verotoxins [VTs], The titre of these various VTs ranged from 1:40 to 1:1280. Of the 26 [43.6%] adherent strains, 19 [73%] exhibited localized adherence [LA] and 7 [27%] manifested enteroadherent-aggregative [EA-Agg] patterns. The remaining 35 strains were nonadherent. Verotoxin producing EPECs elicited diverse effects on rabbit intestine ranging from no effect to severe damage to epithelial architecture, irrespective of their adherence patterns of HEp-2 cells. In conclusion, as far as EPEC pathogenesis is concerned, the role of verotoxins could not be established, but strains producing moderate to high levels of verotoxins may have an increased pathogenicity over non-producers

Drug resistance in diarrhogenic escherichia coli [ETEC,EPEC]

A total of 429 enteropathogenic and enterotoxigenic E. coli isolated from diarrhoeal cases during 1986 and 1989 was tested and compared for resistance against 10 commonly used antimicrobial agents by disk diffusion method. The highest resistance in both years and among all strains was against ampicillin and the least against gentamicin. Multiresistance was common among the isolates with A/C/T/SXT and A/C/T/SXT/S comprising the most prevalent pattern. This study, which is also the first report of antimicrobial drug resistance among ETEC, underlines the need for regular surveillance and its bearing on drug policy is discussed