A Clinico-Microbiological Study of Blood Stream Infections in a Tertiary Referral Hospital: Colistin Resistance & Challenges

Abstract

Carbapenems, frequently used for the treatment of infections caused by Multidrug-resistant (MDR) Gram-negative bacteria (GNB) are being reported with increased resistance rate. Colistin with other antibiotics has emerged as a saviour but inappropriate reporting of colistin susceptibility is a serious clinical concern. To detect the antimicrobial resistance of GNB isolates obtained from blood samples, further, colistin Minimum Inhibitory Concentration (MIC) testing of carbapenem-resistant isolates was done by the Broth Micro-dilution Method (BMD). This prospective study was done in the Department of Microbiology from January 2020 to December 2020. The GNB isolated from blood samples were identified & antimicrobial-susceptibility testing was performed by the Vitek 2 system. Colistin MIC of carbapenem-resistant isolates was done by the BMD method. The data were statistically analysed using SPSS 21. Growth was obtained in 5% of blood samples and 546 (75.8%) of these were GNB including predominantly E.coli, Klebsiella spp & Acinetobacter spp. Carbapenem-resistant infections 246 (48.5%) showed significant association with ICU admission, resistance to other classes of antibiotics & mortality. Among the carbapenem-resistant isolates, only seven (2.9%) were found resistant to colistin by the BMD test. Most of these were Klebsiella spp. (71.4%) & obtained predominantly from ICU patients (85.7%). All the carbapenem-resistant isolates were found intermediate sensitive to colistin by the VITEK-2 system. The isolates of GNB were characterized as MDR 323 (59.2%), XDR 164 (30%) and PDR 2 (0.4%). Use of, colistin, should be guided by BMD, the reference method for MIC testing to avoid erroneous reporting of colistin resistance.

Molecular epidemiology of carbapenem and colistin resistant Acinetobacter baumanii

“…Over all colistin resistance in a study in northern India was 1.7% in AB. [22] while in a study from South India ABCoR was noted in 8-11% between 2016-2019. [23] The prevalence of ABCoR is estimated to be around 5.3% in USA.…”