CTX-M extended-spectrum ß-lactamase-producing Klebsiella spp, Salmonella spp, Shigella spp and Escherichia coli isolates in Iranian hospitals

Abstract This study was conducted in Iran in order to assess the distribution of CTX-M type ESBLs producing Enterobacteriaceae. From January 2012 to December 2013, totally 198 E. coli, 139 Klebsiella spp, 54 Salmonella spp and 52 Shigella spp from seven hospitals of six provinces in Iran were screened for resistance to extended-spectrum cephalosporins. After identification and susceptibility testing, isolates presenting multiple-drug resistance (MDR) were evaluated for ESBL production by the disk combination method and by Etest using (cefotaxime and cefotaxime plus clavulanic acid). All isolates were also screened for bla CTX-M using conventional PCR. A total of 42.92%, 33.81%, 14.81% and 7.69% of the E. coli, Klebsiella spp, Salmonella spp and Shigella spp isolates were MDR, respectively. The presence of CTX-M enzyme among ESBL-producing isolates was 85.18%, 77.7%, 50%, and 66.7%, in E. coli, Klebsiella spp, Salmonella spp and Shigella spp respectively. The overall presence of CTX-M genes in Enterobacteriaceae was 15.4% and among the resistant isolates was 47.6%. This study indicated that resistance to β-lactams mediated by CTX-M enzymes in Iran had similar pattern as in other parts of the world. In order to control the spread of resistance, comprehensive studies and programs are needed.

Production of cytotoxins and enterotoxins by strains of Shigella and Salmonella isolated from children with bloody diarrhea

The role of toxins in the pathogenesis of bloody diarrhea caused by Shigella and Salmonella isolated from children with bloody diarhea was studied for production of toxins active on cells in culture and in rat intestinal loops. Humman epithelial cellls from colon carcinoma (HT-29), Chinese hamster ovary cells (CHO) and kidney fibroblast from rhesus monkey (Vero) were used to detect cytotoxins. On HT-29 almost 50 percent of the Shigella and about 20 percent of the Salmonella strain caused rounding of cells; on CHO over 50 percent Salmonella and 20 percent of Shigella strains caused elongation of cells, some strains caused also rounding of these cells whereas on Vero over 60 percent of Salmonella and 40 percent of Shigella strains caused rounding of cells. Cytotoxicity on Vero and CHO cells was strongly inhibited with cholera toxin antiserum, whereas that on HT-29 was inhibited with C. difficile toxin B antiserum. Cytotonic activity on CHO cells and rounding on Vero cells seem to be suitable models to detect toxins cross-reacting with cholera toxin. Both species, Shigella and Salmonella, produce cytotoxins and enterotoxins which could play a role in intestinal disease

Beta-lactamase diversity in Shigella spp

Some properties of the beta-lactamases produced by one strain of Shigella flexneri, one strain of Shigella sonnei, and one strain of Shigella boydii are studied. Susceptibility of these microorganisms to ampicillin and to cephalotin is investigated before and after a curing treatment with acridine oragne. The substrate profiles of these beta-lactamases, as well as their inducibility, their release to the extracellular environment by osmotic shcok,their susceptibility to enzime inhibitors, and their isoelectric points are also investigated. Transference of ampicillin resistance is tried by bacterial conjugation using a recipient strain of Escherichia coli K-12. The extrachromosomal DNA of the strain is also investigated. Through the analysis of the results the classification of these beta of these beta-lactamases is attempted in relation to the main groups of enzymes which are known at the present time. The three strains proved to be resistant to ampicillin and cephalotin but the transference of this resistance by conjugation was positive only for Sh. flexneri. Several bands of extrachromosomal DNA were observed in these microorganisms. It is concluded that, according to the properties of the enzymes, the beta-lactamase produced by Sh. flexneri belong to the TEM group of enzymes (plasmid-coded beta-lactamases). In relation to the beta-lactamase of Sh. sonnei, its general properties agree with those previously described for enzymes of the same bacterial species and allow the classification of this beta-lactamase as a constitutive cephalosporinase. It is also concluded that the bata-lactamase produced by Sh. boydii is plasmic-coded, since a curing effect was obtained with acridine orange and enzyme activity was released by osmotic shock procedure to the extracellualar environment in more than 80%. However, according to other properties (isolectric point and inhibition profile), this enzyme does not seem to belong to any of the know groups of plasmid-coded beta-lactamases...