Isolation and genetic characterization of metallo-p-lactamase and carbapenamase producing strains of Acinetobacter baumannii from patients at Tehran hospitals

Carbapenems are therapeutic choice against infections caused by gram-negative bacilli including strains of Acinetobacter baumannii. Resistance to these antibiotics is mediated by efflux pumps, porins, PBPs and B-lactamases. The aim of this study was to determine the possibility of existence of MBLs, OXAs and GES-1 betalactamase genes among clinical isolates of Acinetobacter collected from Tehran hospitals. Two hundred and three Acinetobacter isolates were collected from patient at Tehran hospitals. The isolates were identified using biochemical tests. The susceptibility to different antibiotics was evaluated by disk diffusion method and MICs of imipenem were determined using Micro broth dilution method [CLSI]. PCR was performed for detection of bla[VIM-2], bla[SPM-1], bla[IMP-2], bla[GES-2], bla[OXA-51, bla[OXA-23] betalactamase genes. Clonal relatedness was estimated by PFGE with the restriction enzyme Smal. Of 100 isolates of imipenem resistant Acinetobacter spp. collected from Tehran hospitals in 2009 and 2010,6 isolates produced metallo-beta-lactamases and 94 isolates produced OXA- type carbapenemase. The bla[spm-1], bla[GES-1], bla[OXA-51, bla[OXA-23] genes were detected by PCR among 6, 2, 94 and 84 isolates of A. baumannii, respectively. The MICs of isolates to imipenem were 8-128 microg/mL. PFGE analysis of 29 bla[OXA-51] and BLA[OXA-23]-positive A baumannii isolates gave 6 different patterns. This is the first report of SPM-1 and GES-1 beta-lactamase producing A. baumannii. Production of the OXA-23, OXA-51, GES-1 and SPM-1 enzyme presents an emerging threat of carbapenem resistance among A. baumannii in Iran

Rapid, cost-effective, sensitive and quantitative detection of Acinetobacter baumannii from pneumonia patients

Pneumonia with Acinetobacter baumannii has a major therapeutic problem in health care settings. Decision to initiate correct antibiotic therapy requires rapid identification and quantification of organism. The aim of this study was to develop a rapid and sensitive method for direct detection of A. baumannii from respiratory specimens. A Taqman real time PCR based on the sequence of bla[oxa-51] was designed and used for direct detection of A. baumannii from 361 respiratory specimens of patients with pneumonia. All specimens were checked by conventional bacteriology in parallel. The new real time PCR could detect less than 200 cfu per ml of bacteria in specimens. There was agreement between the results of real time PCR and culture [Kappa value 1.0, p value < 0.001]. The sensitivity, specificity and predictive values of real time PCR were 100%. The prevalence of A. baumannii in pneumonia patients was 10.53% [n = 38]. Poly-microbial infections were detected in 65.71% of specimens. Acinetobacter baumannii is the third causative agent in nosocomial pneumonia after Pseudomonas aeroginosa [16%] and Staphylococcus aureus [13%] at Tehran hospitals. We recommend that 10[4] CFU be the threshold for definition of infection with A. baumannii using real time PCR

Antimicrobial resistance pattern of gram-negative bacilli isolated from patients at ICUs of army hospitals in Iran

Patients at intensive-care-unit [ICU] are at risk of acquiring nosocomial infections which contributes to higher rates. Approximately 25% of all hospital infections and 90% of outbreaks occur in ICUs. Multi-resistant gram-negative rods are important pathogens in ICUs, causing high rate of mortality. The purpose of this study was to investigate the antimicrobial resistance patterns among common Gram-negative bacilli isolated from patients with nosocomial infection at Army Hospitals. A total of 187 isolates of Gram-negative bacilli were isolated from 904 patients at ICUs of three Army hospitals in Iran during May 2007 to May 2008. All isolates were examined for antimicrobial resistance using disc diffusion method. The most frequent pathogens were E. coli [32.08%] followed by K. pneumoniae [31%], P. aeruginosa [12.8%] and Acinetobacter spp. [9.1%]. High rate of resistance to third generation cephalosporines was observed among isolates of E. coli and K. pneumoniae. Production of extended spectrum beta lactamases [ESBLs] was found in 46.6% of isolates of both organisms, but in 38% of all Gram negative bacteria. The prevalence of ESBL producing strains at three Army Hospitals is considerable [38%]. However, resistance to imipenem has emerged in these hospitals. Furthermore, studies are required to clarify the situation with multi-drug resistant organisms including the Gram positive bacteria at Army hospitals

Interaction of dietary oils and microflora in experimental colitis

There is growing evidence indicating the benefits of Lactobacilli and Bifidobacteria in attenuation of colitis. On the other hand, some studies have shown that n-3 fatty acids can ameliorate inflammation in colitis. The aim of this study was to examine the interaction between different dietary oils and intestinal microflora in an experimental model of colitis. Eight week-old BALB/C mice [n = 9] were fed isocaloric diets varying only in fat composition for 4 weeks. A group fed the chow diet served as control. The diets contained 20% fat from fish oil, canola oil, safflower oil, or beef tallow. Colitis was induced by intracolonic administration of acetic acid on day 21. Inflammation, fecal microflora and serum lipid profile were compared among the groups one week after induction. The highest degree of inflammation was seen in the chow-diet group, followed by safflower, canola-, and fish oil-fed groups [p < 0.05]. As compared to the experimental groups, the number of fecal bacteroideceae was significantly higher [p < 0.05], and the number of fecal bifidobacteria significantly lower, in the control group [p < 0.05]. Moreover, fish oil could reduce the plasma level of triacylglycerole significantly [p < 0.05]. These results indicate that n-3 fatty acids can affect intestinal microfloral populations in favor of increasing the number of bifidobacteria. They might be recommended as an adjunct therapy to patients with colitis

Aminoglycosides modifying enzymes genes among the population of enterococci in Tehran

Resistance to high level concentration of gentamicin is widespread among isolates of enterococci at Tehran Hospitals. To understand the mechanism of resistance among the Iranian isolates, we screened a collection of E. faecalis and E. faecium isolates to detect aminoglycoside modifying enzymes genes. To detect the high level gentamicin resistant isolates of enterococci [HLGR phenotype, MIC>500 microg/ml], 114 clinical isolates of E.faecalis [n=79] and E. faecium [n=35] were tested with disks containing 120 microg of gentamicin. The macrobroth dilution assay was then used to determine the minimum inhibitory concentration of gentamicin. The susceptibility of isolates against amikacin, netilmicin, tobramycin, kanamycin were also determined by Kirby-Bauer method. All isolates were subjected to polymerase chain reaction assays targeting aminoglycoside modifying enzyme [AMEs] genes including aac [6']-aph [2"], aph [2"]-Ib, aph [2"]-Ic, aph [2"]-Ia, aph [2"]-Id. Aph[3']-IIIa and ant [4']-Ia. All isolates with HLGR phenotype and those showing 64

Prevalence of clostridium difficile- associated diarrhean in hospitalized patients with nosocomial diarrhea

Clostridium difficile is a frequently identified cause of nosocomial gastrointestinal disease. It has been proved to be a causative agent in antibiotic-associated diarrhea, antibiotic-associated colitis, and pseudomembraneous colitis. This study was aimed to determine the prevalence of C.difficile- associated diarrhea in hospitalized patients with nosocomial diarrhea. The 942 hospitalized patients stool samples with nosocomial diarrhea were collected at three hospitals in Tehran from Dec 2002 to Feb 2004.All the stool samples were cultured and in 97 [prevalence: 10.9%] samples grew C.difficile that 57 [prevalence: 6.1%] isolates were toxigenic by cytotoxicity assay and so 57 patients had C.difficile- associated diarrhea. Results of statistical analysis showed significant difference between the rate of C.difficile associated diarrhea and the patients ages [P<0.05]