Phenotypic characterization and colistin susceptibilities of carbapenem-resistant of Pseudomonas aeruginosa and Acinetobacter spp.

Abstract

Introduction: 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 invitro activity of colistin. Methodology: 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. Results: 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. MIC 50 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. Conclusion: 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.

High incidence of MBL-mediated imipenem resistance among Pseudomonas aeruginosa from surgical site infections in Egypt

“…This result is similar to that of Ali and Abdel-Razik, where imipenem resistance was detected in 28.6 % of their P. aeruginosa isolates [24]. Although relatively high, this incidence of imipenem resistance was lower than that reported by other studies carried in Egypt (72%) [25] and in other countries like India (40% in one study [26] and 57.8% in another study [27]) and Brazil (34.5%) [28].…”

“…A remarkably higher prevalence of MBL is detected in this study with 85% of the IRPA producing MBLs, which is comparable to few studies done in Egypt and India [25,26,35]. This could be attributed to the regional difference in MBL distribution among IRPA worldwide [36].…”

In vitro activity of hybrid lavender essential oils against multidrug resistant strains of Pseudomonas aeruginosa

“…Antibacterial and cytotoxic activities of Eos can be attributed to their different constituents. EOs contain complex mixtures including monoterpenes and sesquiterpenes: some of them have been shown to have antimicrobial activity against bacteria and fungi [8,[9][10][11]. It is believed that EOs antimicrobial activity is not related to one specific mechanism, because they have different compositions and, therefore, may damage microbial cells in different ways.…”

“…Inc., Brea, USA) MIC/Combo Panel was used. The Breakpoint Combo Panels use concentrations equivalent to the Breakpoint of Clinical and Laboratory Standards Institute (CLSI) following the European Committee on Antimicrobial Susceptibility Testing (EUCAST) interpretive criteria [8][9].…”

Antibiotic Resistance Patterns and a Survey of Metallo-β-Lactamase Genes Including <b><i>bla-</i></b>_<i>IMP</i> and <b><i>bla-</i></b>_<i>VIM</i> Types in <b><i>Acinetobacter baumannii</i></b> Isolated from Hospital Patients in Tehran

“…In our study, which was conducted from September 2011 to January 2012, we noted that the resistance rate to imipenem has substantially increased (97%) compared to those reported previously. Since MBL genes are carried on plasmids, this may explain the higher prevalence of resistance to many antibiotics in MBL-positive isolates [24]. In strains which were resistant to imipenem but were MBL negative, resistance to imipenem may be due to other mechanisms, such as the production of oxacillinase, deficiency in porin or reduced expression of outer membrane proteins [7].…”