Occurrence & detection of AmpC beta-lactamases at a referral hospital in Karnataka.

BACKGROUND & OBJECTIVES: AmpC beta-lactamases confer resistance to a wide variety of beta-lactam drugs except for cefepime, cefpirome and carbapenems. They are known to be responsible for nosocomial outbreaks, therapeutic failures and multidrug resistance. Although reported with increasing frequency the true rate of occurrence of these beta-lactamases in Enterobacteriaceae is not known. Hence the present study was undertaken to determine the occurrence of AmpC enzymes among clinical isolates. METHODS: A total of 520 consecutive, non-repeat clinical isolates were included in the present study. Twenty eight strains resistant to cefoxitin were tested for AmpC beta-lactamases by the modified 3-dimensional extract method. Isolates harbouring AmpC beta-lactamases were tested for inducible beta-lactamases by disc diffusion. RESULTS: Sixteen (3.3%) isolates were positive for AmpC beta-lactamases. Based on the species 9 (3.3%) Escherichia coli, 4 (2.2%) Klebsiella pneumoniae, 2 (5%) Citrobacter freundii and 1 (5.5%) isolate of Enterobacter aerogenes harboured AmpC enzymes. Nine (56.3%) of AmpC harbouring strains, were urinary isolates. All the isolates were sensitive to imipenem and variably sensitive to aminoglycosides and co-trimoxazole. INTERPRETATION & CONCLUSION: Our findings document the presence of AmpC enzymes in this region. Hence AmpC beta-lactamase detection should be undertaken in clinical isolates showing resistance to broad-spectrum cephalosporins.

In vitro activity of norfloxacin against uropathogens and drug efficacy in simulated bladder model under diabetic conditions.

PURPOSE: The in vitro activity of norfloxacin was determined to maximize the correlation between susceptibility testing of the drug and the results of clinical therapy of urinary tract infection in diabetics. This study was carried out to observe the effect of changing concentration of norfloxacin on the growth of uropathogens under diabetic conditions. METHODS: The standard broth microdilution method was carried out to determine the minimum inhibitory concentration (MIC) using Mueller Hinton broth by varying pH of the medium (5.0, 5.5, 6.0, 6.5 and 7.0) and glucose concentration (100, 250, 500, 1000 and 2000 mg/dL). A specially designed mechanical bladder model system simulating hydrokinetic conditions that exist in the urinary tract of diabetics was employed. RESULTS: The loss of activity of norfloxacin was more pronounced (> four folds) at pH 5.0 and 2000 mg/dL sugar concentration. These findings were consistent with the experiment 'in vitro simulated bladder model' by exposing bacterial growth to varied norfloxacin and sugar concentration. CONCLUSIONS: Although norfloxacin is a drug of choice for non-diabetic and diabetic individuals with mild to moderate glucosuria, in severe diabetic individuals norfloxacin may not be an effective drug.

Asymptomatic bacteriuria in school going children.

PURPOSE: The present study was undertaken to determine the prevalence of asymptomatic bacteriuria in school going children of different age groups and sex and to isolate the organisms responsible for asymptomatic bacteriuria and to know their antimicrobial susceptibility pattern. METHODS: A total of 1817 school children were screened by collecting mid-stream urine and isolating the organisms. RESULTS: Asymptomatic bacteriuria was observed in 192 cases (10.57%) with female preponderance over male. The maximum isolates were E.coli (32.8%). Followed by Klebsiella pneumoniae (22.4%) and Staphylococcus aureus (15.1%). CONCLUSIONS: In the present study there was a steady increase in the incidence of asymptomatic bacteriuria in different age groups. Most of the isolates were resistant to one or more antibiotics.