Cefoxitin resistance mediated by loss of a porin in clinical strains of Klebsiella pneumoniae and Escherichia coli.

PURPOSE: Porins are outer membrane protein (OMP) that form water filled channels that permit the diffusion of small hydrophilic solutes like beta-lactam antibiotics across the outer membrane. Two major porins that facilitate diffusion of antimicrobials have been described in Klebsiella spp. and Escherichia coli. The present study was carried out to examine the role of porins among Extended Spectrum beta-Lactamase (ESBL) and AmpC beta-Lactamase positive strains of Klebsiella spp. and E.coli. METHODS: Preparation of OMP from phenotypically characterized clinical isolates K.pneumoniae and E.coli and the separation of the proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were performed as per a previously described procedure. RESULTS: OMP analysis revealed that cefoxitin and ceftazidime resistance was mediated by loss of a porin Omp K35 in the isolates of K.pneumoniae and E.coli. CONCLUSIONS: Loss of porin mediated resistance mechanism against cefoxitin was observed among the multidrug resistant K.pneumoniae and E.coli.

AmpC beta-lactamase producing multidrug resistant strains of Klebsiella spp. & Escherichia coli isolated from children under five in Chennai.

BACKGROUND & OBJECTIVES: AmpC beta-lactamases are Group I cephalosporinases that confer resistance to a wide variety of beta-lactam drugs. Plasmid mediated AmpC beta-lactamases has been discovered most frequently in isolates of Klebsiella pneumoniae, K. oxytoca, Salmonella, Proteus mirabilis and Escherichia coli. The present study was undertaken to study the occurrence of multidrug resistant and AmpC beta-lactamase producing Klebsiella spp. and Escherichia coli in children less than five years of age as this age group is very susceptible to intestinal and extraintestinal infections. METHODS: A total of 116 isolates of Klebsiella species and 32 isolates of Esch. coli were tested for resistance to cephamycin such as cefoxitin, third generation cephalosporin (3GC) antibiotics (ceftazidime, cefotaxime, ceftriaxone), ampicillin, amikacin, cephaloridine, cefuroxime, co-trimoxazole, gentamycin, imipenem and tetracycline by disc diffusion method. Isolates found resistant to cefoxitin were tested for the production of AmpC beta-lactamases by three dimensional extract method. Transconjugation experiments were done to study the transfer of drug resistance and AmpC beta lactamase production from AmpC producing Klebsiella and Esch. coli isolates to a recipient Esch. coli strain (K12 J62-2). RESULTS: Twenty eight isolates (24.1%) of Klebsiella spp. and 12 (37.5%) of Esch. coli were found to be AmpC beta-lactamase producers; 66.6 per cent and 81 per cent of Klebsiella and Esch. coli isolates respectively showed resistance to all the 3GCs. All the strains were found to be sensitive to imipenem. Eighty four (72%) of Klebsiella isolates and 20 (62.5%) of Esch. coli were found to be resistant to cefoxitin. Transfer of cefoxitin resistance to the recipient strain was observed in all the AmpC producing strains of Klebsiella spp. Of the 12 AmpC producing strains of Esch. coli, only 4 (33.3%) showed the transfer of cefoxitin resistance to the recipient strain. INTERPRETATION & CONCLUSION: This study has shown the occurrence of AmpC beta-lactamase producing Klebsiella and Esch. coli strains in children in Chennai. Since AmpC beta-lactamase production is frequently accompanied by multiresistance to antibiotics, therapeutic options become limited resulting a need for new measures for the management of Klebsiella and Esch. coli infections. Also failure to identify AmpC beta-lactamase producers may lead to inappropriate antimicrobial treatment and may result in increased mortality. Detecting plasmid mediated AmpC beta-lactamase producing strains is technically difficult and the phenotypic tests for AmpC detection are not well defined. If an investigational AmpC beta-lactamase inhibitor was made available for diagnostic testing, it could be useful in combination with a suitable cephamycin to confirm AmpC production.

Extended spectrum beta lactamase (ESBL) mediated resistance to third generation cephalosporins among klebsiella pneumoniae in Chennai.

PURPOSE: To examine the incidence of extended spectrum b lactamase (ESbL) producing strains and multidrug resistant strains of Klebsiella pneumoniae isolated from children between 0-5 years of age. METHODS: Multidrug resistance and ESbL production was studied in a total of 120 isolates of Klebsiella pneumoniae obtained from patients aged 0-5 years. RESULTS: 95% of the isolates showed resistance or decreased susceptibility to atleast one of the three third generation cephalosporins [3GC (ceftazidime, cefotaxime, ceftriaxone)] used for the study. 87% of the isolates showed resistance to all the three 3GC antibiotics and this resistance to all the three 3GC was found to coexist with resistance to other antibiotics. All the isolates were found sensitive to the antibiotic imipenem. ESbL production was detected in 8 strains of Klebsiella pneumoniae. The ESbL activity could be experimentally transferred to recipient E.coli (K12 J62-2). Resistance to b-lactam antibiotics was co-transferred with resistance to gentamicin. CONCLUSIONS: This study has shown the incidence of ESbL producing Klebsiella pneumoniae strains among children in Chennai. Tests for the detection of ESbL producing Klebsiella strains should be carried out in all diagnostic centers routinely and the therapeutic use of all the 3GC should be avoided against Klebsiella strains that appear resistant to any third generation antibiotic.

Extended spectrum beta lactamase production & multidrug resistance in Klebsiella species isolated from children under five with intestinal & extraintestinal infections.

BACKGROUND & OBJECTIVES: Extended spectrum beta-lactamases (ES beta L) are enzymes produced in some Gram-negative bacilli that mediate resistance to third generation cephalosporins (3GC) and aztreonam. These are common in Klebsiella spp. and Escherichia coli and in other members of the family enterobacteriaceae. ES beta L production is accompanied by resistance to other antibiotics as these are encoded by multi drug resistance conjugative plasmids. The present study was undertaken to study the incidence of multi drug resistant and ES beta L producing Klebsiella spp. in children under five years of age suffering from intestinal and extraintestinal infections. METHODS: A total of 90 strains of Klebsiella spp. (76 isolates of K. pneumoniae and 14 of K. oxytoca) were tested for resistance to 3GC antibiotics (ceftazidime, cefotaxime, ceftriaxone), amikacin, ampicillin, erythromycin, gentamycin and streptomycin by disc diffusion method. Isolates found resistant to 3GC antibiotics were tested for the production of ES beta L by double disc diffusion synergy test. Transconjugation experiments were done to study the transfer of drug resistance and ES beta L production from Klebsiella isolates to an Esch. coli strain (K12 J62-2). RESULTS: All the 90 isolates showed multi drug resistance; 87 (96.6%) isolates showed resistance or decreased susceptibility to at least one of the three 3GC. ES beta L production was detected in four strains of K. pneumoniae and two K. oxytoca. ES beta L activity could be experimentally transferred to recipient Esch. coli in all the 6 isolates. Resistance to beta-lactam antibiotics was co-transferred along with resistance to gentamycin. INTERPRETATION & CONCLUSION: This study has shown the incidence of ES beta L producing Klebsiella strains in children in Chennai, and possibly poses a threat in the treatment and management of Klebsiella associated infections. The incidence of ES beta L producing strains of Klebsiella and other members of enterobacteriaceae should be carefully monitored in children to prevent unnecessary use of antibiotics especially 3GC and aminoglycoside antibiotics. Hence, tests for the detection of ES beta L producing Klebsiella strains should be carried out routinely for better therapeutic management.