Frequency of colistin and fosfomycin resistance in carbapenem-resistant Enterobacteriaceae from a tertiary care hospital in Karachi

Abstract

IntroductionManagement of infections with carbapenem-resistant Enterobacteriaceae (CRE) is challenging. In recent times, agents such as colistin and fosfomycin have been used in combination with other antibiotics to treat such infections. In this study, we aim to seek frequency of colistin and fosfomycin resistance in CRE from Pakistan.MethodsThis study was conducted at clinical laboratories, Aga Khan University Hospital. In total, 251 CRE were included in the study. Colistin minimum inhibitory concentrations (MICs) were performed using broth microdilution (BMD) method and VITEK® 2 system, whereas fosfomycin susceptibility was performed using Kirby–Bauer method. MIC50 and MIC90 were calculated for colistin and agreement between VITEK and BMD was also calculated.ResultsOut of 251 strains colistin MIC of ≥4 µg/mL was seen in 40 (15.9%). Of these strains 20 (50%) were Klebsiella pneumoniae. Colistin MIC50 and MIC90 were found to be 0.5 and 16 µg/mL, respectively. BMD and VITEK 2 showed 100% categorical agreement. Essential agreement was 88.5% with kappa score 0.733 indicating strong agreement between VITEK and BMD. 31 out of 251 (12.3%) CREs were resistant to fosfomycin.ConclusionStudy shows frequency of colistin and fosfomycin resistance to be 15.9% and 12.3%, respectively. In countries where rate of CREs is high, emerging resistance against these last resort antibiotics is alarming as it leaves clinicians with almost no options to manage such multidrug resistant and extensively drug resistant infections.

Susceptibility profile, resistance mechanisms & efficacy ratios of fosfomycin, nitrofurantoin & colistin for carbapenem-resistant Enterobacteriaceae causing urinary tract infections

“…Overall, 90.7 per cent of the isolates were susceptible to colistin. Süzük et al 24 from Turkey reported 96.8 per cent colistin susceptibility among CRE, while a study from Pakistan25 found 84.1 per cent colistin susceptibility among CRE.…”

High rate of colistin and fosfomycin resistance among carbapenemase-producing Enterobacteriaceae in Turkey

“…In a study conducted in a tertiary hospital in Pakistan, the rates of resistance to colistin and fosfomycin among the strains of CRE were found to be 15.9% and 12.3%, respectively. In this study, the colistin susceptibility test was performed by the broth microdilution technique and the fosfomycin susceptibility test was performed by the disk diffusion method, using fosfomycin trometamol disks [23]. EUCAST does not suggest using fosfomycin trometamol disks for the strains of Enterobacteriaceae except for the urinary E. coli strains [9].…”

Risk factors for colistin-resistant Enterobacteriaceae in a low-endemicity setting for carbapenem resistance – a matched case–control study

“…Colistin resistance was associated with higher resistance rates to quinolones, fosfomycin and tobramycin, but not carbapenem resistance. Carbapenem-resistant Enterobacteriaceae are known to have concurrent resistance to colistin, fosfomycin and quinolones [ 16 - 18 ], but resistance clusters without concomitant carbapenem resistance have not been described so far and its role and aetiology remains unclear. High rates of colistin resistance in human samples have mainly been reported in countries with high proportions of carbapenem-resistant Gram-negative bacteria and subsequent widespread use of colistin in healthcare settings.…”