Spread of blaCTX-M-type and blaPER-2 β-lactamase genes in clinical isolates from Bolivian hospitals

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To assess the prevalence and types of genes encoding extended-spectrum β-lactamases (ESBLs) in clinical isolates of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter spp. from Bolivia.


A total of 642 clinical isolates were collected consecutively during a 4 month period (September to December 2004). Resistance or reduced susceptibility to cefotaxime and/or ceftazidime and/or aztreonam was assessed using double disc synergy tests using clavulanic acid, cefotaxime, ceftazidime and aztreonam to identify putative ESBL-producing isolates. The ESBL determinants were characterized by colony blot hybridization, PCR and DNA sequencing.


Of the 642 isolates, 220 (34.3%) showed resistance or reduced susceptibility to cefotaxime and/or ceftazidime and/or aztreonam, and 150 (23.4%) were putative ESBL producers. A total of 106 ESBL-producing isolates contained the blaCTX-M-2 gene, and 32 isolates had a novel allele, blaCTX-M-43. blaCTX-M alleles were detected in all P. aeruginosa and Acinetobacter spp. studied. In contrast, only 12 ESBL-producing isolates had blaPER-2, mainly Enterobacteriaceae, although it was also found in a strain of P. aeruginosa.


This is the first study on ESBL-producing strains in Bolivia and it reveals a high prevalence of blaCTX-M genes. The PER-2 enzyme was less prevalent, but its gene was detected in several species, including P. aeruginosa, which is consistent with horizontal transfer.

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