Extended-Spectrum-Beta-Lactamase Production Among Escherichia Coli and Klebsiella Species at The Komfo Anokye Teaching Hospital in Kumasi, Ghana.

Extended-Spectrum-Beta-Lactamases (ESBLs) are enzymes which confer antibiotic resistance on certain bacteria in the family Enterobacteriaceae (Yan et al., 2000). ESBLs are penicillin- destroying enzymes capable of efficiently hydrolyzing penicillins, narrow spectrum cephalosporins, many extended-spectrum cephalosporins, the oxymino group containing cephalosporins (e.g. cefotaxime and ceftazidime), and monobactams (Paterson and Bonomo, 2005). Enterobacteriaceae are Gram negative rods with peritirichous flagella all over their surface. They possess a complex antigenic structure, and produce a variety of toxins and other virulence factors. They also ferment a wide range of carbohydrates and produce carbon dioxide and other gases. They may be found in the intestinal tracts of animals and humans, in soil or in water. Examples are, Salmonella spp., Escherichia coli, Klebsiella spp., Enterobacter spp. and Proteus spp., (Cheesbrough, 2000 and Brooks et al., 2004). Of particular interest to this study are Escherichia coli and Klebsiella spp., the most common Gram negative rods isolated in the laboratory (Brooks et al., 2004). It has become very important to study the prevalence of ESBL-producing organisms because of the increasing antimicrobial resistance and the decreasing number of new drugs available against such microbes (Kader et al., 2006). Since the initial description of ESBLs, microbial isolates that are resistant to broad-spectrum cephalosporins are being increasingly recognized (Itokazu et al., 1996). The problem of antimicrobial resistance may be due to the fact that antibiotics can be obtained and used without medical authorization or supervision in developing countries (Hart and Kariuki, 1998), such as Ghana. This situation has led to inappropriate usage of antibiotics with patients taking the drugs for insufficient length of time or at suboptimal dosages, which may result in antimicrobial resistance. The presence of an ESBL-producing organism in a clinical infection can cause significant treatment problems because ESBL-mediated resistance may result in treatment failure if any of the third generation cephalosporins (e.g., ceftazidime, cefotaxime, and ceftriaxone) or a monobactam (aztreonam) are used (Kang et al., 2004 and Drieux et al., 2008). ESBL-producing organisms may also be difficult to detect because of the effect of their different levels of activity against various cephalosporins, thus making the choice of which cephalosporin to test critical. If an ESBL-producer is detected, it should always be reported as resistant to the penicillins, cephalosporins, and monobactams even if in vitro test results indicate susceptibility, since these may fail in treatment (Harbarth et al., 2003 and Clinical and Laboratory Standards Institute, 2007). It is worth noting that the therapeutic options for infections caused by ESBL-producing organisms are significantly limited because the organisms are also frequently resistant to other non beta-lactam drugs such as aminoglycosides, quinolones, trimethoprim or trimethoprim-sulfamethoxazole and tetracyclines (Kang et al., 2004 and Pitout et al., 2005). This is because the plasmids bearing the genes which encode for ESBLs frequently also carry genes encoding for resistance to these classes of antibiotics (Paterson and Bonomo, 2005).

Source: KNUST