Detection of β-Lactamase Activity in Various Clinical Bacterial Isolates by Three Different Methods and its Correlation with Drug Resistance

Background: β-lactams such as penicillins are the most widely used antibiotics, and β- lactamases are the greatest source of resistance to penicillins. aims and objectives: to study β-lactamase production in clinical isolates of family enterobacteriaceae, p. aeruginosa and staphylococci by three different methods and to correlate its potential with drug resistance; with an endeavour to evaluate convenient and economical method duly supported by relevant minimum inhibitory concentration (mic) studies. material and methods: total 240 clinical isolates (gram-negative bacilli-191, staphylo-coccia) were subjected to antimicrobial susceptibility testing by kirby-bauer disk diffusion method and mic for ampicillin and penicillin was determined by agar dilution method. b-lactamase was detected by broth acidometric, iodometric cell suspension and microbiological method. results: multidrug resistance was observed in more than 90% isolates. one hundred and ninety gram-negative bacilli were resistant to ampicillin and 47 staphylococcal isolates were resistant to both penicillin and ampi- cillin. though microbiological method gave highest positive results 210 (87.5%), iodometric method could detect β-lactamase in apparently sensitive isolates as well giving satisfactory [207 (86.25%)] comparable results. conclusion: in view of the noted bacte rial resistance, tests for b-lactamase should be carried out on a routine basis for an early imple mentation of appropriate antimicrobial therapy. iodometric method is eminently convenient, economical and reliable method. isolates showing mic <0.125^g/ml for penicillin and mic <8^g/ml for ampicillin should be checked for b-lactamase production