Harsha Virendra Patil1, Shivaji T Mohite1, Virendra Chandrashekhar Patil2
1 Department of Microbiology, Krishna Institute of Medical Sciences Deemed to be University, Satara, Maharashtra, India
2 Department of Medicine, Krishna Institute of Medical Sciences Deemed to be University, Satara, Maharashtra, India
Background: Acinetobacter, a nonfermenting Gram-negative coccobacilli, have emerged as significant pathogens causing multidrug-resistant (MDR) ventilator-associated pneumonia (VAP). Metallo-beta-lactamase (MBL)-producing Acinetobacter spp. have become an emerging therapeutic concern worldwide due to the MDR isolates. Aim and Objectives: Phenotypic detection of MBL producing MDR Acinetobacter isolates in patients with VAP and to study the antibiotic susceptibility pattern of MBL-producing isolates. Materials and Methods: This was a prospective observational and noninterventional study conducted on patients with VAP over a period of 2 years. This study was conducted at a tertiary care teaching hospital in the intensive care unit. A total of 164 MBL-producing MDR AB isolates were included in the study. MBL was detected by imipenem-EDTA double-disc synergy test (DDST), imipenem-EDTA combined disc synergy test (CDST-IPM), and MBL-E test. Results: A total of 188 samples were enrolled for the study, fulfilling the inclusion criteria of VAP. Total MDR Acinetobacter spp. isolates were 188 (76.42%) of them, 164 (87.23%) were MBL producing and 24 (12.76%) were nonMBL (P < 0.002). Total 11.17% and 88.83% MDR VAP due to Acinetobacter spp. were early-onset VAP and Late-onset VAP, respectively (P < 0.001). Late-onset VAP due to MDR Acinetobacter spp. was predominant in the present study caused by Acinetobacter spp. Of total 188 MDR Acinetobacter isolates, 156 (82.98%) were Acinetobacter baumannii, 15 (7.98%) were Acinetobacter iwoffii, 9 (4.79%) were Acinetobacter calcoacetiucs, 5 (2.66%) were Acinetobacter hemotyticus, and 3 (1.59%) were ABC complex, predominated by A. baumannii (P < 0.001). Of total 188 MDR Acinetobacter spp. 164 (87.23%) were putative MBL producing and 24 (12.67%) were nonMBL Acinetobacter spp. Of 164 MBL-producing isolates, 141 (85.98%) were detected by the DDST method, and 23 (14.02%) were DDST negative. Total 146 (89.02%) MDR Acinetobacter spp. were detected by a combined disc test-IMP test. A total of 152 (92%) MDR Acinetobacter spp. were detected by MBLe-Test. All MBL-producing MDR Acinetobacter spp. isolates (164) were resistant to piperacillin (PI), piperacillin + tazobactam (PIT), ciprofloxacin (CIP), ceftazidime (CAZ), cefepime (CPM), imipenem (IMP), and meropenem (MRP). The tigecycline (21.34%) resistance was significantly less compared to all other antibiotics. Conclusions: The present study highlighted the burden of MDR MBL producing Acinetobacter spp. in patients with VAP. About three-fourth of patients with VAP had MDR Acinetobacter spp. Eighty percent were MDR Acinetobacter spp. were MBL producers. MDR Acinetobacter isolates, including MBL producer, were significantly higher in late-onset VAP. The ability of phenotypic identification of Acinetobacter spp. for MBL producer among imipenem-EDTA double-disc synergy test (DDST), CDST-IPM and MBL-E Test were comparable. All MBL-producing MDR Acinetobacter spp. isolates were resistant to PI, Ciprofloxacin, CAZ, CPM, IMP, and MRP. The tigecycline resistance was significantly less (1/5th). The study of antibiotic sensitivity patterns and screening for MBL production among A. baumannii isolates is essential for controlling Acinetobacter infections. The judicious use of antimicrobial therapy and combined approaches of rotational antibiotic therapy is strongly suggested.
Keywords: Acinetobacter species, metallo-beta-lactamase, multi-drug resistant, ventilator-associated pneumonia