Abstract
Pseudomonas aeruginosa and Acinetobcter spp. are important nosocomial pathogens and carbapenem resistance is an emerging threat. Therapeutic options for infections with these isolates include colistin. This study was conducted to determine the prevalence of carbapenem resistance in P. aeruginosa and Acinetobacter spp. bloodstream isolates, phenotypically characterize the resistance mechanisms and evaluate the in vitro activity of colistin. Consecutive 145 (95 P.aeruginosa and 50 Acinetobacter spp.) non-repeat isolates were included. Antibiotic susceptibility testing was performed per CLSI guidelines. MIC for carbapenems and colistin was performed using Etest. Isolates showing reduced susceptibility or resistance to the carbapenems were tested for metallo-β-lactamase (MBL) production using imipenem-EDTA combined disk and MBL Etest. Carbapenem resistance was observed in 40% P. aeruginosa and 66.0% Acinetobacter spp. Carbapenem-resistant (CA-R) isolates were significantly (p <0.05) more frequently resistant to the other antibiotics than carbapenem-susceptible isolates. Approximately half of the CA-R strains were multidrug-resistant, and 3.1-5.5% were resistant to all antibiotics tested. MBL was found in 76.3% and 69.7% of the P. aeruginosa and Acinetobacter spp., respectively. Colistin resistance was observed in three (6.0%) Acinetobacter isolates and eight (8.4%) P. aeruginosa. MIC50 for carbapenems were two to four times higher for MBL-positive compared to MBL-negative isolates, but no difference was seen in MIC for colistin. Carbapenem resistance was observed to be mediated by MBL in a considerable number of isolates. Colistin is an alternative for infections caused by CA-R isolates; however, MIC testing should be performed whenever clinical use of colistin is considered.
Highlights
Pseudomonas aeruginosa and Acinetobcter spp. are important nosocomial pathogens and carbapenem resistance is an emerging threat
Data of the antibiotic susceptibilities of Acinetobacter spp. from different geographical regions reveal that the resistance of Acinetobacter to IPM was in the range of no resistance to 40% (2000-2004) [5],which has subsequently risen to 85-87% (2007) in the ICUs of European countries such as Greece, and in the USA [6], while resistance to MEM has risen from 18% (1997-2000) to 43.4% (2006) as reported from multicentric data by the MYSTIC program [7,8]
In India, carbapenem resistance ranges from 10.9- 69% [10, 11] in P. aeruginosa; a range of 9.1-100% [12,13] in Acinetobacter spp. has been reported in various patient
Summary
Pseudomonas aeruginosa and Acinetobcter spp. are important nosocomial pathogens and carbapenem resistance is an emerging threat. Therapeutic options for infections with these isolates include colistin. Colistin is an alternative for infections caused by CA-R isolates; MIC testing should be performed whenever clinical use of colistin is considered. Non-fermenting bacilli such as Pseudomonas aeruginosa and Acinetobacter spp. are pathogens emerging as frequent causes of nosocomial infections, especially pneumonia and sepsis, with mortality rates of 27-48% in critically ill patients [1,2]. The introduction of carbapenems meropenem (MEM) and imipenem (IPM) into clinical practice was a great advance in the treatment of serious infections caused by these multidrug-resistant (MDR) bacteria; carbapenems are often employed as drugs of last resort in these bacteria. The emergence and increasing frequency of isolation of carbapenem-resistant (CA-R) P. aeruginosa and Acinetobacter spp. is a cause for concern [4]. In India, carbapenem resistance ranges from 10.9- 69% [10, 11] in P. aeruginosa; a range of 9.1-100% [12,13] in Acinetobacter spp. has been reported in various patient
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
