Occurrence of Plasmid-Mediated AmpC β-Lactamases Among Escherichia coli and Klebsiella pneumoniae Clinical Isolates in a Tertiary Care Hospital in Bangalore

Abstract

Therapeutic options for infections caused by gram-negative organisms expressing plasmid-mediated AmpC b-lactamases are limited because these organisms are usually resistant to all the b-lactam antibiotics, except for cefepime, cefpirome and the carbapenems. These organisms are a major concern in nosocomial infections and should therefore be monitored in surveillance studies. Hence, this study was aimed out to determine the prevalence of plasmid-mediated AmpC b-lactamases in E. coli and K. pneumoniae from a tertiary care in Bangalore. A total of 63 E. coli and 27 K. pneumoniae were collected from a tertiary care hospital in Bangalore from February 2008 to July 2008. The isolates with decreased susceptibility to cefoxitin were subjected to confirmation test with three dimensional extract tests. Minimum inhibitory concentrations (MICs) were determined by agar dilution method. Conjugation experiments, plasmid profiling and susceptibility testing were carried out to investigate the underlying mechanism of resistance. In our study, 52 (57.7%) isolates showed resistance to cefoxitin, the occurrence of AmpC was found to be 7.7% of the total isolates. Plasmid analysis of the selected isolates showed the presence of a single plasmid of 26 kb in E. coli and 2 Kb in K. pneumoniae. Plasmid-mediated AmpC b-lactamases were found in 11.1% of K. pneumoniae and in 6.3% of E. coli. Curing and conjugation experiments showed that resistance to cephamycins and cephalosporins was plasmid-mediated. Our study has demonstrated the occurrence of plasmid-mediated AmpC in E. coli and K. pneumoniae which illustrates the importance of molecular surveillance in tracking AmpC-producing strains at general hospitals and emphasizes the need for epidemiological monitoring.

Prevalence of ESBLs among Enterobacteriaceae and their Antibiotic Resistance Pattern from Various Clinical Samples

“…32 Most studies showed 100% sensitivity toward imipenem. 33,22,34 Incidences of meropenem resistance higher than that of imipenem among nosocomial pathogens was observed by Gupta et al, 35 The resistance exhibited in our case is due to existence of carbapenemase producing isolates in our setting. This may be because patients in Intensive Care Unit are directly being treated with carbapenems that has led to development of such multidrugresistant isolates in our health-care setting.…”

Investigation of Plasmid Mediated AmpC Beta-Lactamases Among Escherichia coli and Klebsiella pneumoniae Isolated from Blood Cultures

“…Bir diğer sorun ise, porin kaybı ve/veya yüksek düzeyde kromozomal AmpC üretiminin benzer fenotiplere yol açabilmesidir. Bu birleşik mekanizmalar özellikle E.coli'de görülmektedir 10,11 . pAmpC üreten izolatların belirlenmesinde, genişle-tilmiş spektrumlu sefalosporinler (seftazidim, sefotaksim) ve sefoksitin direncine sahip izolatların seçilmesi önerilen bir yöntemdir 12 .…”

Inducible and Plasmid Mediated AmpC Beta-Lactamase among Klebsiella pneumoniae in a Tertiary Care Teaching Hospital of South India

“…In the present study 28.7% of the isolates were found to be plasmid mediated AmpC producer which is higher compared to other studies from India. Study from Chennai during 2005 reveals 20.8% AmpC producers whereas study from Bangalore during 2012 reveals 7.7% as AmpC producers among K pneumonia (Sasirekha et al, 2012). Studies also reveal a relatively higher percentage of these enzymes when compared to earlier report of 2.2% for K pneumoniae isolates in Karnataka (Ratna et al, 2003).…”