Background

Linezolid is one of the last lines of defence for Gram-positive bacteria, and the increasing emergence of linezolid-resistant enterococci (LRE) has become an important problem in nosocomial infections.

Objectives

This study aimed to explore the mechanisms of linezolid resistance and analyse risk factors for the infection with LRE.

Methods

The known resistance mechanisms of linezolid were detected by polymerase chain reaction (PCR). Clinical data of patients with LRE infection were collected from the electronic medical record system. Risk factors associated with LRE were determined by comparing two case groups (LRE group and linezolid-susceptible enterococci [LSE] group) with the control group (without enterococci infection) at a ratio of 1:1:2. Multivariate logistic regression models were used to evaluate independent risk factors for acquiring LRE and LSE.

Results

A total of 85 (4.5%) LRE isolates were detected during a 5-year period. The main resistance mechanism was acquisition of the transferable gene optrA (98.8%), followed by the L4 protein mutation (37.7%) and L3 protein mutation (4.7%). In our study, 85 LRE cases, 85 LSE cases, and 170 controls were then enrolled; multivariable analyses indicated that transfer from another hospital (odds ratio [OR], 3.2; 95% confidence interval [CI], 1.5–7.3; P = 0.004), malignant tumour (OR, 3.7; 95% CI, 1.6–8.8; P = 0.003), polymicrobial infection (OR, 12.2; 95% CI, 1.4–106.2; P = 0.023), and urinary tract infections (OR, 42.7; 95% CI, 11.4–159.3; P = 0.000) were independent predictors for acquiring LRE. In addition, polymicrobial infections (OR, 43.3; 95% CI, 14.1–132.8; P = 0.000), total length of hospital stay (≥30 days) (OR, 5.7; 95% CI, 1.9–17.3; P = 0.002) and exposure to glycopeptide (OR, 6.6; 95% CI, 1.1–38.8; P = 0.035) were independently associated with LSE infections.

Conclusions

Proper antibiotic management programs and monitoring of patient risk factors are necessary to control LRE infections.