The epidemiology of ESBL infections throughout most of the world is closely linked to the presence of the “CTX-M” class of ESBL enzymes. The presence of this class of ESBL enzymes in community hospitals in the US, however, is poorly described.
We analyzed 72 isolates with verified ESBL phenotype (with disc diffusion) prospectively collected from patients admitted to 6 community hospitals in North Carolina and Virginia in the Duke Infection Control Outreach Network from 7/2010-7/2011. These isolates underwent testing to characterize genotypic mechanisms of ESBL resistance, including: CTX-M PCR, CTX-M sequencing and MLST. We also determined clonal relatedness of isolates by using endonuclease digestion and PFGE. We used descriptive statistics to analyze clinical and demographic data of patients with corresponding ESBL infections. Standard surveillance definitions were used to categorize type of infection.
Of 72 isolates studied, 46 (64%) were E. coli; the remaining 26 (36%) were Klebsiellae spp. 28 (39%) isolates came from urinary source, 16 (22%) from blood, and the remainder came from other sites. 40 (56%) isolates were categorized as community-onset healthcare-associated infections, 10 (14%) as community-acquired infections, 10 (14%) as nosocomial infections. The remaining isolates came from outpatients or were colonization without infection. 27 (36%) isolates were from patients admitted from nursing homes or chronic care facilities, 25 (35%) from patients admitted from home and 8 (11%) from patients transferred from another acute care hospital.
53 (74%) ESBL isolates tested positive for CTX-M PCR. Only 51 CTX-M PCR positive isolates were successfully characterized using sequencing; 37 (73%) sequenceable isolates were enzymes resembling CTX-M 15; 7 (10%) had CTX-M 14 characteristics and the remaining were CTX-M 9 and CTX-M 109 enzymes. PFGE showed dissemination of multiple clones of closely-related E. coli and Klebsiellae.
Group 1 CTX-M 15 enzymes were the predominant genotype of ESBL in isolates from community hospitals in North Carolina and Virginia. It is likely that CTX-M-producing ESBL strains have been endemic in this region for prolonged period of time. The true incidence of ESBL infection and colonization of patients from the community may be substantial.
L. F. Chen,
Merck: Investigator, Research grant
Cubist Pharmaceuticals: Speaker's Bureau, Speaker honorarium
Optimer Pharmaceuticals: Speaker's Bureau, Speaker honorarium
Medscape: Independent Contractor, Consulting fee
UpToDate: Independent Contractor, Royalties
S. C. Lancaster, None
A. Keiger, None
C. Woods, Roche Molecular Sciences: Investigator, Research grant
J. Freeman, None
E. Cook, None
L. Adcock, None
R. W. Moehring, None
S. Louis, None
A. L. Cromer, None
D. J. Sexton, UpToDate: Consultant and Independent Contractor, Licensing agreement or royalty
D. J. Anderson, Merck, Inc.: Grant Investigator and Speaker's Bureau, Grant recipient and Speaker honorarium
UpToDate Online: Author, Licensing agreement or royalty
Robert Wood Johnson Foundation: Grant Investigator, Grant recipient
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