Resistance to Third-Generation Cephalosporins and Other Antibiotics by Enterobacteriaceae in Western Nigeria

Problem statement: The emergence and spread of resistance to third-generation cephalosporins are threatening to create species resistant to all currently available agents. The most common cause of bacterial resistance to beta-lactam antibiotics is the production of beta-lactamases and many of the 2nd and 3rd-generation penicillins and cephalosporins were specifically designed to resist the hydrolytic action of major beta-lactamases. However new beta-lactamases emerged against each of the new classes of beta-lactams that were introduced and caused resistance. This study was designed to determine the rate of resistance to 3rd-generation cephalosporins and other classes of antibiotics by the Enterobacteriaceae in this environment. Approach: One hundred bacteria isolates belonging to the family Enterobacteriaceae identified from different clinical specimens between October and December 2007 using standard bacteriological methods. These were subjected to antibiotic susceptibility testing to third-generation cephalosporins and other classes of antibiotics which included quinolones and an aminoglycoside using the Kirby-Bauer method of disc diffusion test. Results: Out of the total number of Enterobacteriaceae isolated in the study period, only 54.8% of the klebsiella species isolated were sensitive to ceftazidime, 48.4% to ceftriaxone and 30.7% to cefotaxime. With Escherichia coli however, the susceptibility pattern to the 3rd-generation cephalosporins was better (65.6% were sensitive to ceftazidime, 62.5% to ceftriaxone and 71.9% to cefotaxime). In proteus species, the susceptibility pattern was generally poor to the three classes of antibiotics(50% were sensitive to ceftazidime and ceftriaxone, 0% to cefotaxime, 33.3% to ciprofloxacin, 50% to gentamycin and 0% to amoxycillin/clavulanate). Conclusion/Recommendations: The poor susceptibility to amoxicillin/clavulanate demonstrated by all the isolates in this study showed the probability of new beta-lactamases production. Further studies therefore need to be done in this environment to determine the types of the beta-lactamases produced by the Enterobacteriaceae here, the prevalent rate of such isolates and the molecular analysis of the new beta-lactamases produced.