Molecular epidemiology of clinical isolates of ampc producing Klebsiella pneumoniae.

Department of Microbiology, University College of Medical Sciences, New Delhi - 110 095, India.
Indian Journal of Medical Microbiology (Impact Factor: 1.04). 07/2006; 24(3):177-81.
Source: PubMed

ABSTRACT AmpC producing K. pneumoniae have been increasingly reported from India but epidemiological studies are lacking. In the present study, molecular epidemiology of extended-spectrum AmpC beta-lactamases (ESACs) producing clinical isolates of K. pneumoniae prevalent in our hospital was studied.
Fifty-one non-repeat, consecutive, clinical isolates of K. pneumoniae producing AmpC enzymes, were subjected to whole cell protein profile analysis (SDS-PAGE) and ribotyping. The antimicrobial susceptibility was determined using standard disk diffusion technique. The isolates showing decreased susceptibility to cefoxitin (< 18 mm) or cefotetan (< 16 mm) were subjected to modified three- dimensional test for detection of AmpC enzyme.
Six different types of protein profiles were observed. Ribotyping could further discriminate between the strains that were clustered by protein fingerprinting. Twelve different ribo-patterns were identified. Ribotyping was found to have a better Discriminatory Index (0.98) than that of SDS-PAGE (0.78). Of the 26 isolates that showed decreased susceptibility to cefoxitin and/or cefotetan 13 isolates were found to harbour AmpC enzyme.
The study demonstrated the usefulness of SDS-PAGE whole cell protein profile analysis and ribotyping to identify the clonality of the ESACs isolates, the latter having a higher discriminatory power. The presence of ESACs isolates in the community as well as in hospital settings emphasizes the need for regular monitoring of antimicrobial resistance.

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    ABSTRACT: The occurrence of multiple β-lactamases among bacteria only limits the therapeutic options but also poses a challenge. A study using boronic acid (BA), an AmpC enzyme inhibitor, was designed to detect the combined expression of AmpC β-lactamases and extended-spectrum β-lactamases (ESBLs) in bacterial isolates further different phenotypic methods are compared to detect ESBL and AmpC. A total of 259 clinical isolates of Enterobacteriaceae were isolated and screened for ESBL production by (i) CLSI double-disk diffusion method (ii) cefepime- clavulanic acid method (iii) boronic disk potentiation method. AmpC production was detected using cefoxitin alone and in combination with boronic acid and confirmation was done by three dimensional disk methods. Isolates were also subjected to detailed antibiotic susceptibility test. Among 259 isolates, 20.46% were coproducers of ESBL and AmpC, 26.45% were ESBL and 5.40% were AmpC. All of the 53 AmpC and ESBL coproducers were accurately detected by boronic acid disk potentiation method. The BA disk test using Clinical and Laboratory Standards Institute methodology is simple and very efficient method that accurately detects the isolates that harbor both AmpCs and ESBLs.
    The Pan African medical journal. 01/2013; 14:28.
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    ABSTRACT: AmpC β-lactamases are cephalosporinases that hydrolyze cephamycins as well as other extended-spectrum cephalosporins and are poorly inhibited by clavulanic acid. Although reported with increasing frequency, the true rate of occurrence of AmpC β-lactamases in different organisms, including members of Enterobacteriaceae, remains unknown. The present study was designed to determine the occurrence of AmpC enzyme-harbouring Gram-negative clinical isolates in a tertiary care hospital in Pondicherry state, South India. A total of 235 Gram negative clinical isolates were tested for resistance to cefoxitin, third generation cephalosporin (3GC) antibiotics, ampicillin, amikacin, co-trimoxazole, gentamicin, meropenem and tetracycline by disc diffusion method. Isolates found resistant to 3GC and cefoxitin were tested for the production of AmpC β -lactamases by three dimensional extraction method and AmpC disc method. Isolates found to sensitive to 3GC were subjected to disc antagonism test for inducible AmpC production. One hundred and thirty four (57%) strains were resistant to 3GC, among which 63(47%) were positive for plasmid-mediated AmpC beta lactamases production. Among the 101 strains sensitive to 3GC, 23 (22.7%) revealed the presence of inducible AmpC beta lactamases by disc approximation test. A total of 80.9% (51/63) of screen positive isolates were detected by Amp C disc test and 93.6% (59/63) by three dimensional extraction method. Out of the 86 AmpC producers, 67 (77.9%) were cefoxitin resistant .Inducible AmpC was not found in Esch.coli and Klebsiella spp. The AmpC producers also concurrently showed multidrug resistance pattern. AmpC producers were found to be prevalent in our hospital and though three dimensional extraction test detects AmpC better, the disk test is easier to perform routinely and is user- friendly.
    Brazilian Journal of Microbiology 07/2010; 41(3):596-602. · 0.45 Impact Factor