Extended-spectrum beta-lactamase (ESBL)-producing strains of Klebsiella pneumoniae have caused major therapeutic problems worldwide since the majority are resistant to various antibiotics commonly used for treatment of most bacterial infections. In sub-Saharan Africa nosocomial infections caused by multi-drug-resistant K. pneumoniae are becoming increasingly common. For instance, in a Kenyan referral hospital, all K. pneumoniae isolates obtained from sporadic infections in neonatal wards over a 6-month period were uniformly resistant to ampicillin, cephradine, cefuroxime, cefotaxime, carbenicillin, ceftazidime and tetracycline. However, they were susceptible to co-amoxyclav, ceftazidime, aztreonam, streptomycin, co-trimoxazole, gentamicin and nalidixic acid. Isolates had MIC of 24 and 1 mg/mL for cefotaxime and ceftazidime, respectively. The presence of clavulanic acid decreased the MIC of cefotaxime 750-fold to 0.032 mg/mL, resistance was shown to be a result of production of CTX-M-12-extended-spectrum b-lactamases (Kariuki et al. 2001).
In a separate study in Nigeria (Soge et al. 2006) CTX-M plasmids isolated from uropathogenic K. pneumoniae were large (58-320 kb) and carried the following genes: aac(6')-Ib (aminoglycoside resistance) which included aac(6')-Ib-cr (aminoglycoside-fluoroquinolone resistance), aadA2 (aminoglycoside resistance), erm(B) (macrolide-lincosamide-streptogramin B resistance), blaTEM-1 (ampicillin resistance), tet(A) (tetracycline resistance), sul1 (sulphonamide resistance), dfr (trimethoprim resistance) and intI1, an integrase associated with class 1 integrons. Often, such high-level resistance in K. pneumoniae may lead to treatment failure using commonly available antibiotics. In Algeria, environmental isolates of K. pneumoniae resistant to extended-spectrum cephalosporins with a phenotype and genotype indicating CTX-M-15 enzyme production were found to be identical to K. pneumoniae clinical isolates recovered from urinary tract infection from hospitalized patients (Touati et al. 2007).
ESBL-producing K. pneumoniae have also caused major therapeutic problems in many other developing countries including Iran (Liu et al. 2007) where 33% of ESBL strains were also resistant to ciprofloxacin and aminoglycosides, while in India (Shukla et al. 2004) ESBL-producing strains also showed resistance against amoxicillin, gentamicin, ciprofloxacin and amikacin in 93.3, 70, 10.4 and 26.1% of the isolates, respectively.
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