investigation of aac[6']-le-aph[2"]-la gene in MDR and HLGR enterococcus faecalis and E. faecium strains isolated from clinical samples

Enterococci are important nosocomial pathogens. Multiple drug resistance [MDR] is common among Enterococci and presents difficulties for treatment. High level gentamicin resistance [HLGR] in enterococci, is a significant therapeutic problem. Bactericidal antimicrobial activity usually is obtained by the synergistic combination of a cell wall active agent such as penicillin or glycopeptide with an aminoglycoside. Enterococci can acquire aminoglycoside resistance genes that mediate production of aminoglycoside-modifying enzymes, which eliminate this synergistic bactericidal effect. The most clinically important HLGR genes is aac [6']-le-aph [2"]-la. In the present study, a total of 437 clinical samples from 5 hospital and 3 private laboratory in Tehran, from azar 1384 to Tir 1385, were collected and 300 enterococcal isolates recovered all of the strains were identified to the species level by conventional biochemical tests and assayed for their susceptibility to 11 antibiotics, ampicillin, tetracycline, erythromycin, ciprofloxacin, high dose gentamicin, vancomycin, cotrimoxazole, quinopristin -daifopristin [synercid], linezolid, teicoplanin and nitrofurantoin by disk diffusion method. Gentamicin MIC was accomplished for HLGR strains. The most frequent species was E. faecalis [81.3%] and then E. faecium [18.7%]. MDR strains were detected in 50% and 95% of E.faecalis and E.faecium, respectively. The number of HLGR strains for E.faecalis and E.faecium were found to be 19.5% and 23.5%, respectively. All HLGR strains showed MIC>1024 microg/mL The PCR results showed that 83% and 100% of E.faecalis and E.faecium strains carried aac[6']-le-aph[2"]-la gene as detected by PCR. The present study indicates high rate dissemination of aac[6']-le-aph[2"]-la gene, suggesting the possible mechanism of transfer of gentamicin resistant genes within the enterococcal population and in this case probable need to new aminoglycosides or other antibiotics would be predictable

Report on Clonal Dissemination of a New Vibrio cholerae Serotype O1 Biotype El Tor Strain in Kurdstan in Summer of 2007

Cholerae disease caused by toxigenic V. cholerae, is a major public health problem in developing countries including Iran. Epidemiological surveillance and comparative molecular analysis of isolates have demonstrated clonal diversity among epidemic strains and a continual emergence of new clones of toxigenic V. cholerae. A total of 20 V.cholerae strains were sent to Pasteur Institute of Iran in September of 2007 from Kordestan province which includes strains of different sub-serotypes. After biochemical identification, isolates subjected to molecular analysis including Pulsed-Field Gel Electrophoresis [PFGE] of NotI digested genomic DNA according to the standardized protocol by Centre of Disease Control [CDC]. PFGE results showed a single pattern for all isolates. The results were interpreted in comparison with patterns obtained by isolates of previous years and showed clonal dissemination of a new clone in Kordestan province in this year

[ prevalence and molecular characterization of vancomycin resistant gram positive cocci isolated from patients in Tehran]

Gram positive bacteria, particularly, Staphylococcus aureus, coagulase negative staphylococci and enterococci are of particular concern in hospitals. But there has been increasing concern about the development of vancomycin resistant enterococci and MRSA strains with reduced susceptibility to vancomycin over the last decade. Therefore, the present study was carried out to confirm the identification of vancomycin resistant gram positive cocci, to determine antibiotic resistance pattern and to study vancomycin resistance genes. The isolates from clinical samples were collected from hospitalized patients and outpatients in Tehran. Gram positive cocci species identification was performed by using conventional tests and PCR using specific primers. VRE isolates were subjected to antibiotic susceptibility testing, MICs of vancomycin were determined by the E-test method. Determination of vancomycin resistance genes, vanA and vanB were performed with PCR. Confirmation of transposons was performed with specific primers for vanS. Out of 1030 gram positive isolates, none of the staphylococci or streptococci isolates were resistant to vancomycin. Most of vancomycin resistant isolates in this study were VRE. faecium [96%] and harbored vanA. All of the isolates were positive for vanS the conserved fragment of transposon and carried the identical digestion pattern like type strain. According to the results of this study, all of the vancomycin resistant isolates were enterococcus spp. Vancomycin resistant enterococci itself is now a major and largely untreatable infection, and can pass the vancomycin resistance genes to the other highly virulent gram positive cocci

Characterization of vancomycin resistant enterococcus faecium

To determine the species distribution, updated drug susceptibility patterns and genes conferring resistance in clinical vancomycin resistant enterococcal [VRE] isolates. Clinical enterococcal isolates collected during 7 months, from September 2005 to April 2006 from hospitalized patients and outpatients were studied. Twenty five VRE were isolated from 450 enterococci samples [5.6%]. VRE isolates were subjected to antibiotic susceptibility tests. Genotype of these isolates was determined by PCR. All of the isolates were E. faecium and carried the vanA gene. Antibiotic susceptibility tests showed that the isolates were resistant to ampicillin 25[100%], ciprofloxacin 25[100%], gentamicin 24[96%], erythromycin 25[100%], tetracyclin 10[40%] and chloramphenicol 2[8%]. VRE strains were resistant to three antibiotics and were susceptible to new antibiotics linezolid and dalfopristin- quinupristin. Switching to treatment with these antibiotics would relieve the problem for a short time

Serogroup Distribution of Shigella in Tehran

In recent years, the importance of Shigella as an enteric pathogen with global impact has been increasingly recognized. In this study, serogroup distribution of Shigella isolated from clinically diagnosed cases of gastroenteritis and acute diarrhea in Tehran, capital of Iran was investigated between December 2002 and November 2003. Fecal specimens and rectal swabs were cultured for Shigella spp. using st and ard microbiological techniques. The isolates of Shigella were identified by biochemical assay and serological testing. From a total of 302 Shigella isolates, 178, 110, 10 and 4 strains were identified as S.sonnei [58.9%; 95% CI: 53.2-64.5], S. flexneri [36.4%; 95% CI: 31.0-42.2], S.boydii [3.3%], and S. dysenteriae [1.3%], respectively. The peak of infection occurred during summer. Overall, 167 patients [55.3%] were males and 135 [44.7%] were females