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

Stefan E Richter; Loren Miller; Daniel Z Uslan; Douglas Bell; Karol Watson; Romney Humphries; James A McKinnell

doi:10.1128/JCM.00149-18

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

J Clin Microbiol. 2018 Aug 27;56(9):e00149-18. doi: 10.1128/JCM.00149-18. Print 2018 Sep.

Authors

Stefan E Richter^{1

2}, Loren Miller³, Daniel Z Uslan⁴, Douglas Bell⁵, Karol Watson^{2

6}, Romney Humphries⁷, James A McKinnell³

Affiliations

¹ Department of Pulmonology and Critical Care Medicine, University of California, Los Angeles, Los Angeles, California, USA richtermdphd@gmail.com.
² NIH BD2K Center of Excellence at UCLA, University of California, Los Angeles, Los Angeles, California, USA.
³ Infectious Disease Clinical Outcome Research Unit, Los Angeles Biomedical Research Institute at Harbor-UCLA, Los Angeles, California, USA.
⁴ Department of Infectious Disease, University of California, Los Angeles, Los Angeles, California, USA.
⁵ Department of Internal Medicine, University of California, Los Angeles, Los Angeles, California, USA.
⁶ Department of Cardiology, University of California, Los Angeles, Los Angeles, California, USA.
⁷ Department of Pathology & Laboratory Medicine, University of California, Los Angeles, Los Angeles, California, USA.

Abstract

Infections due to colistin-resistant (Col^r) Gram-negative rods (GNRs) and colistin-resistant Klebsiella pneumoniae isolates in particular result in high associated mortality and poor treatment options. To determine the risk factors for recovery on culture of Col^r GNRs and Col^rK. pneumoniae, 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^r GNR model) and the second when organism identification is performed but prior to reporting of antimicrobial susceptibility testing results (corresponding to the Col^rK. pneumoniae 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 K. pneumoniae isolates) were analyzed, 128 of which were Col^r (i.e., MIC > 2 μg/ml), including 68 of which that were Col^rK. pneumoniae In multivariate analysis, risk factors for Col^r 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 (c-statistic = 0.81). Risk factors for Col^rK. pneumoniae 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 Staphylococcus aureus antimicrobial in the last 90 days, and prior infection with a carbapenem-resistant organism (c-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^r GNR and Col^rK. pneumoniae isolates.

Keywords: Gram-negative bacteria; Gram-negative rods; antibiotic resistance; antibiotic stewardship; antimicrobial agents; antimicrobial testing; clinical decision making; colistin.

MeSH terms

Anti-Bacterial Agents / pharmacology*
Anti-Bacterial Agents / therapeutic use
Clinical Decision-Making
Colistin / pharmacology*
Drug Resistance, Bacterial*
Gram-Negative Bacteria / drug effects
Gram-Negative Bacteria / isolation & purification*
Gram-Negative Bacterial Infections / drug therapy
Gram-Negative Bacterial Infections / epidemiology*
Gram-Negative Bacterial Infections / microbiology
Humans
Klebsiella Infections / drug therapy
Klebsiella Infections / epidemiology*
Klebsiella Infections / microbiology
Klebsiella pneumoniae / drug effects
Klebsiella pneumoniae / isolation & purification*
Microbial Sensitivity Tests
Retrospective Studies
Risk Factors

Substances

Anti-Bacterial Agents
Colistin

Abstract

MeSH terms

Substances

Grants and funding