ABSTRACT
INTRODUCTION: MBL containing genes have been reported in all GNBs including Acinetobacter spp since 1990s which are worrisome as they are transmitted by mobile genetic elements. Thus, early detection of MBL encoding organisms is necessary. The current study was designed to identify the most sensitive cost-effective test which could be used as a screening test for detection of cabapenamase producing Acinetobacter isolates. METHODOLOGY: All consecutive strains of Acinetobacter spp isolated from various clinical samples were included. All isolates found resistant to any of the carbapenems were tested for MBL production using MHT (on MacConkey Agar and Mueller Hinton Agar), Etest (using Imipenem/Meropenem-EDTA) and Combined Disc Test (using EDTA and 2 MPA as inhibitors and Ceftazidime/Imipenem/Meropenem as substrate discs). PCR was performed for representative strains for IMP, VIM, KPC, OXA and NDM-1 gene. RESULTS: Total of 154 non-duplicate strains of Acinetobacter spp were isolated and identified, of which, 134 (88%) and 126 (82%) were resistant to meropenem and imipenem respectively. All 134 meropenem resistant strains were tested for MBL production and PCR was performed on 100 strains. 3(3%), 5(5%), 7(7%), 26(26%), and 51(51%) strains had IMP gene, VIM gene, KPC gene, OXA gene and NDM-1 gene. MHT on MAC had better performance than on MHA and dilution to 0.05 McFarland was not required. CONCLUSION: MHT on MAC had best sensitivity when compared with gold standard PCR and was also cost effective. With ROC curve, we found that 2MPA was not a good MBL inhibitor when compared with EDTA..
ABSTRACT
INTRODUCTION: The purpose of this study was to investigate the prevalence of Postoperative central nervous system infections (PCNSIs) and antibiotic resistance profiles of causative organisms in trauma patients following neuroinvasive procedures. MATERIALS AND METHODS: This was a retrospective study conducted over a period of 4 years (2013-2017). All in-patients admitted under a neurotrauma unit meeting the inclusion criteria of PCNSIs were included in the study. Surgical site infections (SSIs) were defined according to the Centers for Disease Control and Prevention 2018 (CDC) criteria. We retrospectively examined the demographic characteristics, type of neurosurgery performed, laboratory data, causative organisms, and antimicrobial susceptibility testing results of patients who had positive cerebrospinal fluid cultures following craniotomy between January 2013 and December 2017. RESULTS: Of total 2500 patients operated during the study, 961 patients were screened for PCNSIs. The estimated prevalence (95% confidence interval) of PCNSIs which is a type of organ/space SSI was 7.2% (6.3-8.3). Males were predominantly affected (85.0%). The mean age (standard deviation) of patients was 31.9 (16.5) years. Of all the cultures sent for microbiological examination, 18.6% were positive. The proportion of Gram-negative bacteria causing PCNSIs was 91.6%. Multidrug-resistant (MDR) Acinetobacter baumannii (41%) was the most common organism isolated. Among Gram-positive bacteria, the most common organism was Staphylococcus aureus (5.5%). All the Gram-positive isolates were susceptible to vancomycin, teicoplanin, and linezolid. CONCLUSION: There is a high burden of PCNSI caused by MDR Acinetobacter baumannii can pose a major clinical challenge with only few antimicrobials left in the pipeline.
ABSTRACT
INTRODUCTION: Acinetobacter baumannii has now emerged as a significant nosocomial pathogen in health-care setting ESP in intensive care units. Rapidly growing resistance among clinical isolates suggests a need to detect resistance mechanisms in this organism. The present study was designed to compare the various phenotypic tests available with the gold standard of genotype. METHODOLOGY: The present study was conducted to include all isolates of Acinetobacter spp. isolated over 3 years. Their resistance to various antibiotics was determined and extended spectrum beta-lactamases (ESBL) and AmpC production in the isolates showing resistance to ceftazidime/ceftriaxone/cefotaxime (CAZ/CTR/CTX) was determined. ESBL and AmpC production was confirmed using polymerase chain reaction (PCR). RESULTS: A total of 154 strains were isolated, and all the strains were tested for ESBL and AmpC detection. Of the strains tested, 15 (9.7%), 17 (11%), 24 (15.6%), 27 (17.5%), 54 (35%), 67 (43.5%), and 72 (46.7%) strains showed ESBL production using CTX/CTX-clavulanate double-disc synergy test (DDST), CTX/CTX-clavulanate E-test, CAZ/CAZ-clavulanate DDST, CAZ/CAZ-clavulanate E-test, Piperacillin/Piperacillin-tazobactam (TZ) DDST, CTR/CTR-Sulbactum DDST, and Piperacillin/Piperacillin-TZ E-test, respectively. 20 (12.9%) and 19 (12.3%) of strains were positive for AmpC production using AmpC disc test and Boronic acid inhibition test, respectively. Genotype analysis using PCR for TEM, SHV, CTXM, PER, and VEB genes was done and 69 (51.5%) strains were positive for TEM gene. DISCUSSION: ESBL detection in Acinetobacter spp. is difficult as standard guidelines for the same are not available unlike in enterobacteriaceae, and there are no zone diameter breakpoints for aztreonam and cefpodoxime. In comparison, piperacillin/piperacillin-TZ E-test had the best sensitivity and specificity for ESBL detection. CONCLUSION: Standard guidelines for ESBL detection in nil fermeners like Acinetobacter spp. must be laid down for ease of detection. Use of piperacillin/piperacillin-tazobactam E-test could be used as one of the standard methods.
