Prevalence of qnr and aac[6']-Ib-cr genes in clinical isolates of klebsiella pneumoniae from Imam Hussein Hospital in Tehran

Background: Plasmid mediated quinolone resistance [PMQR] has been shown to play an important role in resistance not only to quinolones, but also [beta]-lactams and aminoglycosides. In fact, qnr genes are frequently carried along with [beta]-lactamase determinants on the same plasmids. We studied the prevalence of qnrA, qnrB, qnrS and aac[6']-Ib-cr genes among quinolone and cephalosporin resistant clinical isolates of Klebsiella pneumoniae [K. pneumoniae], as well as the association between PMQR genes with resistance to quinolones, cephalosporins and Aminoglycosides

Methods: The study was conducted on 79 K. pneumonia clinical isolates collected from Imam Hussein hospital in Tehran between July 2010 and January 2011, based on their resistance to quinilones and cephalosporins. Antibacterial susceptibility was determined to 15 antibiotics by disc diffusion. Presence of qnrA, qnrB, qnrS and aac[6']-Ib-cr genes were investigated using specific primers and PCR

Results: Of the 79 K. pneumoniae isolates, 47 [59.5%] carried the PMQR determinants. Among these, 42 [89.4%] carried aac[6']-Ib-cr of which, 21 [50%] also harbored qnrB. Three isolates carried qnrB alone, two [4.2%] harbored qnrS and none had qnrA. Resistance to aminoglycosides and cephalosporins was significantly higher in the isolates carrying both qnrB and aac[6']-Ib-cr genes compared to aac[6']-Ib-cr alone

Conclusion: This study showed a high prevalence of aac[6']- Ib-cr and qnrB genes among the Iranian K. pneumonia clinical isolates as well as co-carriage of the two genes. There was a significant association between qnrB gene carriage and resistance to quinolones, cephalosporins, and aminoglycosides

Cloning and enhanced expression of an extracellular alkaline protease from a soil isolate of Bacillus clausii in Bacillus subtilis

Alkaline proteases are of industrial importance, mainly in the detergent industry. In this study, the extracellular alkaline serine protease gene, aprE, from Bacillus clausii was amplified by PCR and further cloned and expressed in B. subtilis WB600 using the pWB980 expression vector. Protease activity of the recombinant B. subtilis WB600 harboring the plasmid pWB980/aprE reached up to 1020 U/ml, approximately 3-folds higher than the native B. clausii strain. Characterization of the recombinant alkaline protease by SDS-PAGE and zymogram analyses indicated a molecular weight of 31 kDa. DNA sequence analysis and the deduced amino acid sequence revealed 98% homology with the extracellular alkaline serine protease from B. clausii KSM-K16

Biofilm formation and detection of IcaAB genes in clinical isolates of methicillin resistant staphylococcus aureus

Methicillin-resistant Staphylococcus aureus [MRSA] in an important cause of nosocomial and community infections. Biofilm formation, mediated by a polysaccharide intercellular adhesion [PIA] and encoded by the ica operon, is considered to be an important virulence factor in both S. epidermidis and S. aureus. However, the clinical impact of the ica locus and PIA production is less well described in s. aureus. We studied biofilm formation in clinical isolates of MRSA in relation to the presence of the ica operon. Forty five MRSA were studied for biofilm formation by colony morphology on Congo red agar [CRA] and the microtitre plate assay [MtP]. Presence of the ica genes was detected by PCR and specific primers. The results showed that 53.3% of the isolates had the potential to form biofilm by colony morphology of which, 75% carried the ica operon. Weak biofilm production was observed in the MtP assay by 57.8%, of which 53.8% harbored the ica operon. However, about 70% of biorilm non-producers also carried the ica operon. Overall, there was no agreement between the icaAB gene carriage and biofilm phenotype by either of the two phenotypic methods. However, 91% of biofilm formers on CRA also produced biofilm in the MtP assay

Genetic profiling of Pseudomonas aeruginosa isolates from Iranian patients with cystic fibrosis using RAPD-PCR and PFGE

Pseudomonas aeruginosa is the most important cause of chronic lung infections and death in patients with cystic fibrosis. Determining the distribution of specific strains within patient populations is important in order to examine the epidemiology of the disease and the possibility of cross infection among patients. Forty six Iranian patients with cystic fibrosis were studied for colonization with P. aeruginosa. Colony phenotype was recorded and antibiotic susceptibility to 11 antibiotics was determined using the disc diffusion method. Genetic fingerprinting was carried out by RAPD-PCR and by PFGE. Forty five P. aeruginosa isolates were recovered from 31 patients including sequential cultures from 9 subjects. The rate of colonization increased with age. All isolates were susceptible to tobramycin and ciprofloxacin, 97.8% were sensitive to amikacin and piperacillin, 93.3% to gentamycin, 91.1% to ticarcillin, 86.7% to colistin, 80% to carbenicillin, 48.9% to cefotaxime, 26.7% to imipenem and 11.1% to ceftazidime. Genetic fingerprinting showed similar distribution profiles for RAPD-PCR and PFGE and the majority of the isolates had unique fingerprints. No relationship was observed between the obtained genotypes and antibiotic susceptibility profiles and common predominant virulent clones were not found among the isolates

Antibacterial activity of twenty Iranian plant extracts against clinical isolates of helicobacter pylori

Due to increasing emergence of drug-resistance in Helicobacter pylori isolates, traditional plants are potentially valuable sources of novel anti-H. pylori agents. In this research, anti-H. pylori activity of the organic extracts of twenty native Iranian plants was determined against ten clinical isolates of H. pylori. Disc diffusion was used to determine the biological activity of 20 plant extracts as well as 8 antibiotics commonly used to treat H. pylori infections. Minimum inhibitory concentrations were also measured by tube and agar dilution methods for the biologically active plant extracts. Of the twenty plant extracts analyzed, sixteen exhibited good anti-H. pylori activity, using disc diffusion. The ten most active extracts were Carum bulbocastanum, Carum carvi, Mentha longifolia, Saliva limbata, Saliva sclarea, Ziziphora clinopodioides, Thymus caramanicus, Glycyrrhiza glabra, Xanthium brasilicum and Trachyspermum copticum. Minimum inhibitory concentrations measured for the 10 biologically active plant extracts were within the range of 31.25 to 500 micro g/ml. Among the ten plant extracts effective against H. pylori clinical isolates, Carum carvi, Xanthium brasilicum and Trachyspermum copticum showed the highest activity

beta-lactamase typing by substrate hydrolysis in clinical isolates of methicillin resistant Staphylococcus aureus

Staphylococcus aureus is one of the most important causes of nosocomial infections and most clinical isolates are multidrug resistant. Resistance to beta-lactam antibiotics is most often due to bacterial beta-lactamase production. Characterization of beta-lactamases is important for choosing appropriate antibiotic therapy. Thirty methicillin resistant Staphylococcus aureus [MRSA] were identified by standard biochemical methods. Antibacterial susceptibility to 9 beta-lactam antibiotics was determined. Beta-lactamase production was shown in all isolates using the colony iodometric test and nitrocefin discs. Beta-lactamase typing was carried out by measuring the relative substrate hydrolysis rates. The MRSA isolates were resistant to the majority of beta-lactam antibiotics. The results showed that 90% of the isolates displayed type A substrate hydrolysis profile of beta-lactamase. The alarming high level of resistance to beta-lactam antibiotics including methicillin and 3[rd] generation beta-lactams show the need for extensive studies on alternative treatment protocols and use of new drugs

Characterization of beta-lactamases from urinary isolates of escherichia coli in Tehran

Knowledge of antimicrobial resistance patterns in E. coli, the predominant pathogen associated with urinary tract infections [UTI] is important as a guide in selecting empirical antimicrobial therapy. To describe the antimicrobial susceptibility of E. coli associated with UTI in a major university hospital in Tehran [Iran], seventy-six clinical isolates of E. coli were studied for susceptibility to beta-lactam antibiotics by the disc diffusion method and Minimal Inhibitory Concentrations determination. All isolates were resistant to ampicillin, amoxicillin and oxacillin. Resistance to the other tested antibiotics was shown to be 93.4% to cefradine, 76.3% to carbenicillin, 47.3% to cefazoline, 50% to cefalexin and 32.8% to cephalothin while 1.3% expressed resistance to cefoxitime, and 2.6% were resistant to ceftizoxime and ceftriaxone. Two isolates [2.4%] harbored extended spectrum b-lactamases [ESBL] shown by the double disc diffusion method. Substrate hydrolysis by ultra violet spectroscopy showed that 87.4% harbored penicillinases, 9% produced cephlosporinases and 3.6% degraded both substrates. Clavulanic acid inhibited enzyme activity in 82.9%, of which 78.95% was penicillinases [group IIa] and 3.95% was cephalosporinases [group IIb] of the Bush classification system. The rest of the isolates [6.58%] were placed in group IV beta-lactamases. No group III b-lactamase was found, as EDTA inhibited none of the enzymes. DNA amplification by polymerase chain reaction using specific primers for ampC, TEM and SHV type beta-lactamases for all of the isolates showed that 47 organisms [60%] carried the TEM gene and 18 isolates [24%] harbored blaTEM and ampC genes. About 26% of the organisms harbored SHV type enzymes. These results indicate that E. coli can posses a variety of b-lactamases that are responsible for beta-lactam resistance