Risk Factors for Colistin Resistance among Gram-Negative Rods and Klebsiella pneumoniae Isolates

Abstract

Infections due to colistin-resistant (Col) Gram-negative rods (GNRs) and colistin-resistant isolates in particular result in high associated mortality and poor treatment options. To determine the risk factors for recovery on culture of Col GNRs and Col, analyses were chosen to aid decisions at two separate time points: the first when only Gram stain results are available without any bacterial species information (corresponding to the Col GNR model) and the second when organism identification is performed but prior to reporting of antimicrobial susceptibility testing results (corresponding to the Col model). Cases were retrospectively analyzed at a major academic hospital system from 2011 to 2016. After excluding bacteria that were intrinsically resistant to colistin, a total of 28,512 GNR isolates (4,557 isolates) were analyzed, 128 of which were Col (i.e., MIC > 2 μg/ml), including 68 of which that were Col In multivariate analysis, risk factors for Col GNRs were neurologic disease, residence in a skilled nursing facility prior to admission, receipt of carbapenems in the last 90 days, prior infection with a carbapenem-resistant organism, and receipt of ventilatory support (-statistic = 0.81). Risk factors for Col specifically were neurologic disease, residence in a skilled nursing facility prior to admission, receipt of carbapenems in the last 90 days, receipt of an anti-methicillin-resistant antimicrobial in the last 90 days, and prior infection with a carbapenem-resistant organism (-statistic = 0.89). A scoring system derived from these models can be applied by providers to guide empirical antimicrobial therapy in patients with infections with suspected Col GNR and Col isolates.

Evaluation of the MicroScan Colistin Well and Gradient Diffusion Strips for Colistin Susceptibility Testing in Enterobacteriaceae

“…Previous estimates for colistin resistance prevalence have varied. In one study from a single academic medical center over a 6-year period using BMD, 0.45% of all Gram-negative rods (excluding isolates with intrinsic colistin resistance) showed a colistin MIC of Ն4 g/ml, and 1.5% of all K. pneumoniae had an MIC of Ն4 g/ml (36). In another study evaluating carbapenemresistant K. pneumoniae (CRKP) using broth macrodilution, 13% of CRKP had an MIC of Ն4 g/ml (37).…”

“…Gradient diffusion strips for colistin testing should not be used because of their high rates of very major errors. Reference BMD remains the gold standard, and some laboratories do use this method (36). Others have evaluated Sensititre Research Use Only GNX2F plates (Thermo Fisher, Waltham, MA) (41).…”

Investigation of carbapenemase and mcr-1 genes in carbapenem-resistant Klebsiella pneumoniae isolates

“…In addition to these mechanisms, the first plasmid-mediated colistin resistance gene, mcr-1, was identified on an IncI2 plasmid from Escherichia coli and K. pneumoniae in China [5]. Another plasmidmediated colistin resistance gene mcr-2 was found in 2016 [6]. It was suggested that dissemination of the mcr genes can lead to a serious escalation of the current antibiotic resistance crisis in the World [6].…”

Practices About Antibiotic Use Among Urban Residents: A Cross-Sectional Survey in Rufisque, Senegal

“…It is serious as it concerns today antibiotics of last resort like colistin and carbapenems. This situation raises fears of reaching the tipping point, that is, a return to the preantibiotic era [11,12]. Senegal is not immune to this scourge in view of the results of the WHO JEE [18].…”

“…In the WHO African region, this resistance is detected in 57% of cases while in the WHO region of the Americas it is 100% [10]. Recently cases of colistin resistance have been reported in the United States [11] and China [12].…”