RESUMEN
Higher generation cephalosporins, resistant to ß-lactamases were designed to combat bacterial resistance to first generation ß-lactam antibiotics. This led to the emergence of extended spectrum ß-lactamases (ESBLs), which conferred bacterial resistance to these drugs. Now, combination drugs employing a ß-lactam drug + a ß-lactamase inhibitor (Clavulanate, Sulbactam, Tazobactam) are used against ESBL-producing pathogens. This study aimed to evaluate the efficacy of these combination drugs against ESBL-producers and also screening for the presence of inducible AmpC ß-lactamase producers. Enterobacteriaceae family culture isolates exhibiting resistance to the 2nd / 3rd generation cephalosporins by the Disk Agar Diffusion test were tested for ESBL production by the Double Disk Synergy Test. Staphylococcal species culture isolates were tested for ßlactamase production by the Nitrocefin spot test. The Disk Antagonism test was used to screen for the presence of inducible Amp C ß-lactamase producers. The combination drugs included in this study were Cefepime/Tazobactam, Cefoperazone/Sulbactam, Cefotaxime/ Sulbactam, Ceftriaxone/ Sulbactam & Ceftriaxone/ Tazobactam. 128 clinical isolates were tested for ß-lactamase activity. Of the 26 S.aureus isolates, 88.4% (23) were ß-lactamase positive and 57.1 % coagulase negative Staphylococci were positive. Amongst Enterobacteriaceae family, 67.8% of E.coli; 53.1% of K.pneumoniae and 53.8% of Proteus species were confirmed ESBL producers. For E.coli, the best drug was Cefepime/ Tazobactam. All drugs were effective against Proteus spp. K.pneumoniae and S.aureus isolates were resistant to these drugs due to the production of AmpC ß-lactamases. 3.4% of E.coli, 4.5% of S.aureus and 14.2% of Proteus spp were confirmed inducible AmpC ß-lactamase producers.