Prevalence, Treatment, and Outcome of Infection Due to Extended-Spectrumβ-Lactamase–Producing Microorganisms

Clinical and Molecular Epidemiology of Healthcare-Associated Infections Due to Extended-Spectrumβ-Lactamase (ESBL)–Producing Strains ofEscherichia coliandKlebsiella pneumoniaeThat Harbor Multiple ESBL Genes

Objectives.

To characterize healthcare-associated infections due to extended-spectrumβ-lactamase (ESBL)-producing strains ofEscherichia coliandKlebsiella pneumoniaethat harbor multiple ESBL genes, as opposed to a single ESBL gene.

Methods.

All patients with a confirmed healthcare-associated infection due to an ESBL-producing strain ofE. coliorK. pneumoniaewere enrolled in the study. Molecular typing of isolates was performed, and the comparative risks and outcomes of patients were analyzed.

Results.

Among 71 patients with healthcare-associated infection due to an ESBL-producing strain ofE. coliorK. pneumoniae, the gene for CTX-M, with or without other ESBL genes, was identified in all 51 (100%) of the patients infected with anE. colistrain and in 18 (90%) of the 20 patients infected with aK. pneumoniaestrain. Of these 71 patients, 17 (24%) met the definition of healthcare-associated infection due to an ESBL-producing strain that harbored multiple genes; in multivariate analysis, previous exposure to 3 or more classes of antibiotics (adjusted odds ratio, 4.5 [95% confidence interval, 1.7-75.2]) was the sole risk factor for healthcare-associated infection due to an ESBL-producing strain that harbored multiple ESBL genes. Isolates recovered from patients with healthcare-associated infection due to an ESBL-producing strain that harbored multiple ESBL genes were more resistant to various antibiotic classes, and, compared with patients with healthcare-associated infection due to an ESBL-producing strain that harbored a single ESBL gene, they were more likely to have ineffective initial empirical antimicrobial therapy (52% vs 94%; odds ratio, 5.1 [95% confidence interval, 1.04-14.5]).

Conclusions.

CTX-M ESBL is highly prevalent in Thailand. Patients with healthcare-associated infection due to an ESBL-producing strain that harbored multiple ESBL genes were more likely to have had ineffective initial empirical antimicrobial therapy, and, given that antibiotic selection pressure was the only associated risk, we suggest focused antimicrobial stewardship programs to limit the emergence and spread of healthcare-associated infection due to ESBL-producing strains in this middle-income country.

Molecular and descriptive epidemiologyof multidrug-resistant Enterobacteriaceae in hospitalized infants

OBJECTIVE

To investigate the epidemiology of multidrug-resistant Enterobacteriaceae (MDRE) in hospitalized infants.

METHODS

From 2000 through 2005, active surveillance cultures for MDRE were performed for patients admitted to a 40-bed neonatal intensive care unit (NICU) that provides care for critically ill infants 6 months of age or younger. MDRE epidemiology and the genetic relatedness of MDRE strains determined by repetitive-sequence polymerase chain reaction were analyzed.

RESULTS

Active surveillance cultures revealed that 759 (23%) of 3,370 NICU infants (or approximately 1 in 5) developed MDRE colonization or infection and that 613 (72%) of the 853 isolates with epidemiologic data available were healthcare acquired. MDRE colonization occurred more frequently (in 653 infants [86%]) than did MDRE infection (in 106 [14%]). Of the 653 infants with MDRE colonization, 119 (18%) eventually became infected, with 29 (4%) acquiring sterile site infections. The most commonly isolated organisms were the Enterobacter species, accounting for 612 (71%) of the 862 isolates. Molecular epidemiologic analysis revealed that genetic-relatedness clustering (related clusters defined as having a genetic similarity coefficient greater than 95%) varied depending on microbial species. Clustering was detected for 36 (78%) of the 46 Enterobacter aerogenes isolates, 22 (45%) of the 49 Enterobacter cloacae isolates, and 13 (59%) of the 22 Klebsiella pneumoniae isolates.

CONCLUSION

Hospitalized infants are at significant risk of acquiring MDRE, specifically Enterobacter species, at the study institution. Active surveillance cultures identified colonized patients who likely contributed to the institutional reservoir of MDRE. Molecular epidemiologic studies suggest that both patient-to-patient transmission and de novo acquisition of resistance play a role in the acquisition of these organisms, and that the clinical significance of such acquisition varies by species. The high percentage of E. aerogenes isolates that demonstrated genetic clustering suggests that monitoring the prevalence of this organism could serve as a useful measure of compliance with infection control procedures.

Inappropriate antibiotic use in a tertiary care center in Thailand: an incidence study and review of experience in Thailand

The incidence and patterns of and factors associated with inappropriate antibiotic use were studied in a tertiary care center in Thailand. The incidence of inappropriate antibiotic use was 25%. Admission to the surgical department (adjusted odds ratio, 2.0; P=.02) and to the obstetrics and gynecology department (adjusted odds ratio, 2.0; P=.03) were associated with inappropriate antibiotic use, whereas consultation with an infectious diseases specialist was protective against inappropriate antibiotic use (adjusted odds ratio, 0.15; P=.01).