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Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes

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Risk factors and outcomes associated with the isolation of polymyxin B and carbapenem-resistant Enterobacteriaceae

Jocelyn Qi-Min Teo¹, Cassandra Wee-Ting Chang², Hui Leck³

¹Department of Pharmacy, Singapore General Hospital, Outram Road, Singapore 169608, Singapore; Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, #10-01, Singapore 117549, Singapore.

International Journal of Antimicrobial Agents

|March 19, 2019

Abstract:

Increasing resistance to polymyxin, a last-line antibiotic, is a growing public health concern worldwide. The primary objective of this study was to identify predictors for the isolation of polymyxin-resistant (PR) carbapenem-resistant Enterobacteriaceae (CRE) among hospitalized patients. The secondary objective was to describe the clinical outcomes of patients with PR-CRE infections. A retrospective case-control study including patients admitted to Singapore General Hospital between June 2012 and June 2016 was conducted. Cases were defined as patients who had clinical cultures from which a PR-CRE was isolated. Controls were randomly selected from patients with polymyxin-susceptible (PS) CRE admitted during the same period, and frequency-matched to site of isolation. We included 37 PR cases and 111 PS controls. Polymyxin resistance was detected predominantly in Enterobacter spp. (54.1%) and Klebsiella pneumoniae (43.2%). Multilocus sequence typing showed little clonal relatedness among the isolates. mcr-1 was detected in two PR-CRE isolates. Multivariable analyses showed that PR-CRE isolation was associated with prior polymyxins (adjusted odds ratio (OR), 21.31; 95% confidence interval (CI), 3.04-150.96) and carbapenem exposures (OR 3.74; CI 1.13-12.44), when adjusted for time at risk and bacteria species. In PR-CRE patients with infections, the 30-day all-cause in-hospital mortality was 50.0% as compared to 38.1% in patients with PS-CRE (P = 0.346). Prior polymyxin and carbapenem exposures were independent risk factors for isolation of PR-CRE. Outcomes of PR-CRE and PS-CRE infections were similar in this study.

Insights

Prior exposure to polymyxins and carbapenems predicts the isolation of polymyxin-resistant carbapenem-resistant Enterobacteriaceae (PR-CRE). Outcomes for PR-CRE and polymyxin-susceptible CRE infections were similar in hospitalized patients.

Area of Science:

Infectious Diseases
Microbiology
Public Health

Background:

Rising global concern over polymyxin resistance, a critical last-line antibiotic.
Carbapenem-resistant Enterobacteriaceae (CRE) pose a significant threat, compounded by emerging polymyxin resistance.
Understanding drivers of polymyxin-resistant CRE (PR-CRE) is crucial for infection control.

Purpose of the Study:

Identify predictors for PR-CRE isolation in hospitalized patients.
Describe clinical outcomes associated with PR-CRE infections.
Inform strategies to combat antimicrobial resistance.

Main Methods:

Retrospective case-control study at Singapore General Hospital (June 2012-June 2016).
Cases: Patients with PR-CRE isolates; Controls: Patients with polymyxin-susceptible CRE isolates.
Multivariable analysis to determine risk factors for PR-CRE isolation.

Main Results:

Polymyxin resistance primarily observed in Enterobacter spp. and Klebsiella pneumoniae.
Prior exposure to polymyxins (aOR 21.31) and carbapenems (aOR 3.74) were independent predictors of PR-CRE isolation.
The presence of mcr-1 gene was detected in two PR-CRE isolates.
No significant difference in 30-day mortality between PR-CRE (50.0%) and polymyxin-susceptible CRE (PS-CRE) (38.1%) infections.

Conclusions:

Prior antibiotic exposure, particularly to polymyxins and carbapenems, significantly increases the risk of PR-CRE isolation.
Clinical outcomes for PR-CRE and PS-CRE infections appear comparable in this cohort.
Findings highlight the importance of antibiotic stewardship to mitigate the spread of resistant pathogens.

Read full analysis

Keywords:

Colistin Enterobacteriaceae Polymyxin Predictors Resistance

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