Molecular epidemiology of colonizing and disease-causing Klebsiella pneumoniae in paediatric patients.

Klebsiella pneumoniae causes a range of clinical disease in paediatric patients and is of increasing concern due to growing antibiotic resistance, yet little is known about the relative distribution of commensal and pathogens throughout the population structure of K. pneumoniae. We conducted a prospective, observational study of 92 isolates from Seattle Children's Hospital, including 49 disease isolates from blood and urine (13 and 36 isolates, respectively) and 43 colonization isolates from stool. Susceptibility to 20 antimicrobials was evaluated using disc diffusion, VITEK 2 and Etest. Strain relatedness was investigated using multilocus sequence typing (MLST). Demographic and clinical characteristics were largely similar between disease and colonization cohorts, with 85.7 and 74.4 % of disease and colonization cohort patients, respectively, having an underlying medical condition; the sole exception was a relative abundance of patients with urologic or renal abnormalities in the disease cohort, consistent with the predominance of urine specimens among the disease isolates. With regard to antibiotic susceptibility properties, no significant differences were noted between the disease and colonization cohorts. Using molecular analysis, 71 unique sequence types (STs) were distinguished, with novel MLST findings evident in both cohorts; 43 (46.7 %) isolates represented novel STs, including 22 with a novel allele sequence. Thirteen STs contained multiple isolates and all seven isolates with resistance to three or more antibiotic classes were within one of four multirepresentative STs. This study demonstrates that nearly half of paediatric Klebsiella isolates represent novel STs, with clustering of multidrug resistance within specific STs. These findings expand our understanding of the intersection of bacterial population structure, human colonization ecology and multidrug resistance in K. pneumoniae.

Molecular diversity in mechanisms of carbapenem resistance in paediatric Enterobacteriaceae.

Development of carbapenem resistance in Enterobacteriaceae has impacted Clinical and Laboratory Standards Institute (CLSI) guidelines, infection control approaches and treatment strategies. The clinical, phenotypic and genotypic characteristics of carbapenem-resistant Enterobacteriaceae (CRE) infections at paediatric referral centres are not well described. CRE were identified through the clinical microbiology laboratory at Seattle Children's Hospital (Seattle, WA). Clinical data were retrieved from medical records. Resistance testing, polymerase chain reaction (PCR) for resistance determinants, and Escherichia coli transformation were carried out for each isolate. Multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were used to characterise strain relatedness. PCR amplification and sequencing as well as sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) were used to investigate porin alterations. Six CRE isolates were identified between 2002 and 2010. Significant molecular diversity was documented in their mechanisms of resistance, including plasmid-mediated serine carbapenemase (KPC) and metallo-ß-lactamase (IMP), chromosomally encoded ß-lactamase (SME) and porin alterations with extended-spectrum ß-lactamases. Patients had underlying health conditions and were from geographically diverse regions. In one case, PFGE of serial isolates documented the development of resistance in a previously susceptible strain. Molecular investigation of this strain identified insertion of the genetic mobile element insertion sequence ISEcp1 in the ompK36 gene, conferring a functional porin alteration as demonstrated by SDS-PAGE. This is the first description of porin disruption by ISEcp1 in a CTX-M-15-positive isolate. This is the largest report of paediatric CRE to date. This diverse description of demographic, phenotypic and molecular characteristics highlights the challenge of CRE infections in high-risk paediatric patients and that attention to emerging resistance mechanisms (including membrane alteration) at paediatric referral centres is essential.

Chlamydia screening of youth and young adults in non-clinical settings throughout California.

BACKGROUND: Urine-based chlamydia tests enable screening in non-clinical settings. GOAL: The goal of this study was to determine the prevalence of chlamydia infection among high-risk youth and young adults in non-clinical settings. DESIGN: County sexually transmitted disease (STD) programs implemented chlamydia screening projects in non-clinical settings using nucleic acid amplification tests. Demographic and access to care data were collected. RESULTS: Overall, 16,279 female and male youth were screened for chlamydia in 24 counties throughout California. The 158 screening venues included 32 educational, 32 correctional, and 94 community-based settings. Chlamydia infection rates varied significantly by gender, age, and venue type. Among females, the highest prevalence was found in jail settings (14.6%), juvenile detention (13.0%), and alternative schools (10.0%). Among males, the highest prevalence was found in jail (7.9%) and juvenile detention (5.8%). Venue types that serve populations with poor access to care and high rates of infection were identified. CONCLUSIONS: Screening projects in non-clinical settings identify high-risk youth in need of STD care, improve access to STD screening and education, and foster local collaborations.