Epidemiology of vancomycin-resistant Enterococcus faecalis: a case-case-control study.

Although much is known about vancomycin-resistant (VR) Enterococcus faecium, little is known about the epidemiology of VR Enterococcus faecalis. The predilection of VR E. faecalis to transfer the vancomycin resistance determinant to Staphylococcus aureus is much greater than that of VR E. faecium. The epidemiology of VR E. faecalis has important implications regarding the emergence of vancomycin-resistant S. aureus (VRSA); 8 of 13 reported VRSA cases have been from Michigan. A retrospective case-case-control study was conducted at the Detroit Medical Center, located in southeastern Michigan. Unique patients with VR E. faecalis infection were matched to patients with strains of vancomycin-susceptible (VS) E. faecalis and to uninfected controls at a 1:1:1 ratio. Five hundred thirty-two VR E. faecalis cases were identified and were matched to 532 VS E. faecalis cases and 532 uninfected controls. The overall mean age of the study cohort (n = 1,596) was 63.0 ± 17.4 years, and 747 (46.8%) individuals were male. Independent predictors for the isolation of VR E. faecalis (but not VS E. faecalis) compared to uninfected controls were an age of ≥65 years, nonhome residence, diabetes mellitus, peripheral vascular disease, exposure to cephalosporins and fluoroquinolones in the prior 3 months, and immunosuppressive status. Invasive procedures and/or surgery, chronic skin ulcers, and indwelling devices were risk factors for both VR E. faecalis and VS E. faecalis isolation. Cephalosporin and fluoroquinolone exposures were unique, independent predictors for isolation of VR E. faecalis. A majority of case patients had VR E. faecalis present at the time of admission. Control of VR E. faecalis, and ultimately VRSA, will likely require regional efforts focusing on infection prevention and antimicrobial stewardship.

Epidemiology and risk factors for isolation of Escherichia coli producing CTX-M-type extended-spectrum ß-lactamase in a large U.S. Medical Center.

A case-case-control study was conducted to identify independent risk factors for recovery of Escherichia coli strains producing CTX-M-type extended-spectrum ß-lactamases (CTX-M E. coli) within a large Southeastern Michigan medical center. Unique cases with isolation of ESBL-producing E. coli from February 2010 through July 2011 were analyzed by PCR for blaCTX-M, blaTEM, and blaSHV genes. Patients with CTX-M E. coli were compared to patients with E. coli strains not producing CTX-M-type ESBLs (non-CTX-M E. coli) and uninfected controls. Of 575 patients with ESBL-producing E. coli, 491 (85.4%) isolates contained a CTX-M ESBL gene. A total of 319 (84.6%) patients with CTX-M E. coli (282 [74.8%] CTX-M-15 type) were compared to 58 (15.4%) non-CTX-M E. coli patients and to uninfected controls. Independent risk factors for CTX-M E. coli isolation compared to non-CTX-M E. coli included male gender, impaired consciousness, H2 blocker use, immunosuppression, and exposure to penicillins and/or trimethoprim-sulfamethoxazole. Compared to uninfected controls, independent risk factors for isolation of CTX-M E. coli included presence of a urinary catheter, previous urinary tract infection, exposure to oxyimino-cephalosporins, dependent functional status, non-home residence, and multiple comorbid conditions. Within 48 h of admission, community-acquired CTX-M E. coli (n = 51 [16%]) and non-CTX-M E coli (n = 11 [19%]) strains were isolated from patients with no recent health care contacts. CTX-M E. coli strains were more resistant to multiple antibiotics than non-CTX-M E. coli strains. CTX-M-encoding genes, especially bla(CTX-M-15) type, represented the most common ESBL determinants from ESBL-producing E. coli, the majority of which were present upon admission. Septic patients with risk factors for isolation of CTX-M E. coli should be empirically treated with appropriate agents. Regional infection control efforts and judicious antibiotic use are needed to control the spread of these organisms.