Prevalence of blaSHV, blaTEM and blaCTX-M antibiotic resistance genes in selected bacterial pathogens from the Pretoria Academic Hospital

Abstract

Extended spectrum beta-lactamases (ESBLs) are considered one of the most important antibiotic resistance mechanisms. Multidrug resistance is emerging in many Gram-negative pathogens and is associated with severe nosocomial infections. The emergence of ESBL-producing bacteria coincided, in the 1980s, with the increased usage of cephalosporins. This study investigated the prevalence of ESBLs in 56 selected clinical bacterial isolates, collected over a three week period during August 2006, from the Pretoria Academic Hospital. Isolates included: one Citrobacter freundii; 13 Escherichia coli; three Morganella morganii ssp morganii; four Enterobacter cloacae; 34 Klebsiella pneumoniae and one Proteus penneri. Multiplex PCR was used to detect the presence of the blaSHV, blaTEM and blaCTX-M genes. The results were as follow for each of the isolates: i) E. coli: blaSHV detected in 8% (1/13); blaTEM and blaSHV detected in 15% (2/13); blaTEM and blaCTX-M detected in 23% (3/13) and blaTEM detected in 54% (7/13) of the isolates. ii) M. morganii: blaSHV detected in 33% (1/3) and blaTEM and blaCTX-M detected in 33% (1/3) of the isolates. The third M. morganii isolate was negative for all the genes. iii) The P. penneri isolate was positive for the blaTEM gene only. iv) K. pneumoniae: blaSHV detected in 3% (1/34); blaSHV and blaTEM detected in 6% (2/34); blaTEM detected in 15% (5/34) and blaTEM and blaCTX-M detected in 35% (12/34) of the isolates. v) E. cloacae: blaTEM detected in 25% (1/4); blaSHV and blaTEM detected in 25% (1/4); blaSHV and blaCTX-M detected in 25% (1/4) while the last isolate was negative for all three genes. The overall prevalence of these ESBL genes in this study was 48% (27/56). According to the literature these results were higher when compared to 33% for E. coli and 15% for K. pneumoniae in Europe and only 0.8% in Denmark for similar pathogens. These research findings indicated that it is crucial to routinely monitor the prevalence of these resistance genes in a hospital setting to ensure that antibiotic treatment regimens can be adjusted accordingly.