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Acta Médica Costarricense

On-line version ISSN 0001-6002Print version ISSN 0001-6012


ARAYA-FONSECA, Carlos et al. Infecciones nosocomiales por bacterias productoras de ß lactamasa de espectro ampliado: prevalencia, factores de riesgo y análisis molecular. Acta méd. costarric [online]. 2007, vol.49, n.2, pp.90-96. ISSN 0001-6002.

Aim: Production of ß-lactamases is a very frequent mechanism of resistance to antibiotics in Gram-negative bacteria. Since the 80’s, new types of these enzymes, extended spectrum ß -lactamases (ESBL) were described in isolates of Escherichia coli and Klebsiella pneumoniae in Europe and in North America. These bacteria are resistant to all ß -lactam antibiotics, except the carbapenems. Its global dissemination has been fast, creating an important therapeutic challenge. The objectives of this study were to analyze the prevalence of infections with these bacteria in patients admitted to the Hospital San Juan de Dios, a 700 beds tertiary care hospital, the risk factors associated and to perform a molecular analysis of the identified enzymes. Methods: Records from the Bacteriological Laboratory were reviewed in order to identify E.coli and K.pneumoniae ESBL-producers between March and July 2004 In a case - control study, risks factors to acquire these bacteria in hospitalized patients were analyzed. Automated equipment (Vitek-bioMerieux ®) was used to identify bacteria, susceptibilities to antibiotics as well as ESBL production. Verification of enzyme production was done by the disc diffusion susceptibility testing using cefotaxime, cefotaxime + clavulanate, ceftazidime and ceftazidime + clavulanate. The sequence analysis of ß - lactamases types SHV-5, CTX-M and TEM was done using the PCR amplification technique. Results: ESBL were demonstrated in 12% isolates of E.coli and 16% isolates of K.pneumoniae in 2004 and 18% of E.coli and 40% K.pneumoniae in 2005. Forty four patients and 47 controls were studied during the study period. The risks factors for infections due to ESBL- producing organisms were: long hospitalization stay (p<0.05), prior use of ciprofloxacin (p<0.001), use of various antibiotic mixtures (p<0.01), the presence of a central venous catheter or a urinary catheter (p<0.01), the presence of diabetes mellitus or chronic renal insufficiency (p<0.02). High resistance to gentamicin (78%), ciprofloxacin (85%), trimetoprim-sulfametoxazol (91%), piperacilin-tazobactam (78%) and cefepime (100%) were found in ESBL-producing E. coli and K. pneumoniae. ESBL types demonstrated in E.coli were TEM (94%), SHV-5 (76%) and CTX-M (3%) and in K. pneumoniae TEM(100%), CTX-M(30%). In some isolates, more than 1 ESBL type was shown. Conclusion: Infections with ESBL-producing E. coli and K. pneumoniae are an increasing problem in our hospital. Risks factors associated with these infections were long hospital stay, antimicrobial use, the presence of chronic diseases and the use of in-dwelling catheters. High resistance patterns to some antimicrobials were found in these organisms also previously reported in other series. ESBL types identifies were similar to observed in other countries, but the lack of SHV-5 in K. pneumoniae is a remarkable finding. We analyze these findings and discuss their clinical and epidemiologic implications.

Keywords : extended spectrum ß -lactamases; Klebsiella pneumoniae; Escherichia coli; antibiotic resistance.

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