Detection of β-lactamase-mediated resistance

Abstract

beta-Lactams are the most widely used antibiotics, and beta-lactamases are the greatest source of resistance to them. An understanding of beta-lactamase detection and identification is therefore valuable. Colorimetric, acidimetric and iodometric tests of beta-lactamase production are good, rapid indicators of penicillin and ampicillin resistance in Haemophilus, Moraxella and Neisseria spp. These methods can also be applied to Gram-negative aerobic bacilli but are less useful, since the usual question is not whether a beta-lactamase is produced by these organisms, but which beta-lactamase? Accurate identification of the beta-lactamases of Enterobacteriaceae demands gene or protein sequencing, but the broad type of enzyme produced by an isolate can often be inferred from antibiotic susceptibility data. Resistance to ceftazidime or cefpodoxime implies extended-spectrum beta-lactamase (ESBL) production in Escherichia coli and Klebsiella spp., especially if susceptibility to cefoxitin is retained. ESBL production can be confirmed with double disc tests or with various commercial kits. Derepression of AmpC beta-lactamases in Enterobacter spp. and Citrobacter freundii is another important mechanism and can be inferred from cross-resistance to beta-lactamase inhibitor combinations and to all cephalosporins except fourth-generation agents. Antagonism between cefoxitin and cefotaxime can be used to infer the presence of inducible AmpC enzymes in these species, indicating the risk of segregation of derepressed mutants, but in general this risk is better predicted from accurate speciation.

Biodegradation of Pharmaceutical Wastes in Treated Sewage Effluents by Bacillus subtilis 1556WTNC

“…Both cefuroxime and ampicillin belong to β-lactam antibiotics, which represent about 50 % of the universal antibiotic consumption in the world (Livermore 1998;Livermore and Brown 2001). Ciprofloxacin is also effective against Gram-negative and Gram-positive bacteria (Kummerer et al 2000;Kummerer 2003), but the usage of ciprofloxacin is less than β-lactam antibiotics.…”

Nosocomial infection and characterization of extended-spectrum β-lactamases-producing Enterobacteriaceae in Northeast Brazil

“…A new family of ESBLs, CTX-M, has emerged over recent years, especially in E. coli. This family has become one of the most important families of ESBL enzymes in many countries [28][29][30] . CTX-M ß-lactamases are the predominant type of ESBLs in Europe and South America 29,31 , including Brazil 32 .…”

Microbial based assay for specific detection of β-lactam group of antibiotics in milk

“…Data was analysed statistically and expresses as the mean (±SD) of three replicates according to Snedecor and Cochran (1980) Result & discussion B. cereus 66 was screened for β-lactamase production using iodometric method (Livermore and Brown 2001) with slight modifications. The test ampoules containing culture and penicillin G, showed color change within 15-25 min as a result of induction of β-lactamase indicating the presence of inducer i.e.…”

“…Screening for β-lactamase B. cereus 66 procured from NCDC, NDRI, Karnal was activated overnight in nutrient broth at 37°C and were streaked on nutrient agar followed by incubation at 37°C for 12 h. Colony from respective plates was picked up for ß-lactamase enzyme by iodometric method (Livermore and Brown 2001).…”