Ertapebem disk performance to predict Klebsiella pneumoniae carbapenemase produced by Gram-negative bacilli isolated in a São Paulo city public hospital

Abstract

Objective: To evaluate ertapenem disk performance to predict Klebsiella pneumonie carbapenemase production by Gram-negative bacilli. Methods: All Gram-negative bacilli isolated between January 2010 and June 2011 were tested by disk diffusion (Oxoid™) for sensitivity to ertapenem, meropenem and imipenem. Resistant or intermediate sensitivity strains (diameter ≤22 mm for ertapenem) were also tested for the blaKPC gene by polymerase chain reaction. Disk predictive positive value for Klebsiella pneumoniae carbapenemase and specificity were calculated. Results: Out of the 21839 cultures performed, 3010 (13.78%) were positive, and Gram-negative bacilli were isolated in 708 (23.52%) of them. Zone of inhibition diameter for ertapenem disk was ≤22 mm for 111 isolates, representing 15.7% of all Gram-negative isolates. The PCR assay for blaKPC detected 40 Klebsiella pneumoniae carbapenemase-producing strains. No strains intermediate or resistant to meropenem and imipenem were sensitive to ertapenem. The ertapenem disk presented a positive predictive value of 36% to predict blaKPC and 89% specificity. Conclusion:The resistance of Gram-negative bacilli detected by disk diffusion against ertapenem does not predict Klebsiella pneumoniae carbapenemase production. Other mechanisms, such as production of other betalactamases and porin loss, may be implicated. The need to confirm the presence of the blaKPC is suggested. Therefore, ertapenem was a weak predictor for discriminating strains that produce Klebsiella pneumoniae carbapenemase.

Nosocomial infections by Klebsiella pneumoniae carbapenemase producing enterobacteria in a teaching hospital

“…(9; 19.1%). These results are in agreement with the study conducted by Almeida et al ( 14 ) in the city of São Paulo (SP), in which, from 40 samples that presented with the bla KPC gene (PCR), 38 were K. pneumoniae and 2 were Enterobacter cloacae . Still in this study, the authors found that the isolates originated from different clinical specimens such as urine, tracheal secretion, blood culture, pancreatic abscess secretion, and the largest isolation occurred in a rectal swab, representing 42.5%, ( 14 ) different from the present study in which the greatest isolation was in tracheal aspirates (12; 25%), followed by urine (10; 21%).…”

“…Ertapenem constituted a marker of resistance to carbapenems, and could be directly related to the KPC enzyme or to other mechanisms that decrease sensitivity to these antimicrobials in a specific way, such as with the production of other beta-lactamases and loss of purines. ( 14 ) In the study by Bratu et al, which involved 62 isolates of K. pneumoniae that produced KPC, the resistance to carbapenems imipenem, meropenem, and ertapnenem was 98%, 96%, and 100%, respectively. In this study, the authors concluded that the resistance to ertapenem represented the most sensitive clinical test for detection of KPC production.…”

“…(9; 19,1%). Esses resultados estão de acordo com o estudo realizado por Almeida et al, ( 14 ) na cidade de São Paulo (SP), no qual, de 40 amostras que apresentaram o gene bla KPC (PCR), 38 eram K. pneumoniae e 2 Enterobacter cloacae . Ainda nesse estudo, os autores constataram que os isolados foram oriundos de diferentes espécimes clínicos, como urina, secreção traqueal, hemocultura, secreção do abscesso pancreático e o maior isolamento ocorreu em swab retal, representando 42,5%, ( 14 ) diferentemente do presente estudo, em que o maior isolamento ocorreu dos aspirados traqueais (12; 25%), seguidos de urina (10; 21%).…”

“…O ertapenem constitui um marcador de resistência aos carbapenêmicos, podendo estar relacionado diretamente à enzima KPC ou a outros mecanismos, que diminuem a sensibilidade a esse antimicrobiano de forma específica, como produção de outras betalactamases e perda de porinas. ( 14 ) Na pesquisa realizada por Bratu et al, a qual envolveu 62 isolados de K. pneumoniae produtoras de KPC, a resistência aos carbapenêmicos imipenem, meropenem e ertapnenem foi de 98%, 96% e 100%, respectivamente. Nesse estudo, os autores concluíram que a resistência ao ertapenem representou o teste clínico mais sensível para detecção da produção de KPC.…”

Incidência de infecções por Enterobactérias resistentes a carbapenêmicos em pacientes previamente colonizados

“…Os dados são preocupantes, uma vez que polimixina B é considerado tratamento de última linha para essas infecções graves. Já o percentual de resistência a ertapenem era esperado, pois para os carbapenêmicos já é considerado um marcador de resistência, podendo ou não estar associado à produção enzimática 37 .…”