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Transmission of extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae in households outweighs nosocomial dissemination in the non-outbreak setting. Importation of ESBL producers into the hospitals is as frequent as transmission during hospital stay. ESBL– Klebsiella pneumoniae might be more efficiently transmitted within the hospital than ESBL– Escherichia coli .

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Strain-specific SNP genotyping allowed rapid and inexpensive identification of M. tuberculosis outbreak isolates in a population-based strain collection. Subsequent targeted WGS provided detailed insights into transmission dynamics. This combined approach could be applied to track bacterial pathogens in real time and at high resolution.

During a 3-month period, small-colony variant phenotypes of both Staphylococcus aureus and Pseudomonas aeruginosa were isolated from respiratory secretions of 8.2% and 9.2%, respectively, of 98 patients with cystic fibrosis, particularly those with advanced pulmonary disease and prolonged antibiotic exposure. Infection of the respiratory tract with Staphylococcus aureusand Pseudomonas aeruginosa plays an important role in the pathogenesis of cystic fibrosis (CF) (7). Recently, subtypes of S. aureus and P. aeruginosa termed small-colony variants (SCV) have been isolated from the respiratory secretions of CF patients (3,5,12). S. aureus SCV have been associated with persistent infections, and they are more resistant to many antibiotics than normal S. aureus strains (9, 11, 13). The small, nonpigmented, nonhemolytic colonies, which may not be recovered in the routine clinical microbiology laboratory (10), were found in the respiratory secretions of 26 (33%) of 78 CF patients followed for 3 years (5). Characteristics of P. aeruginosa SVC (14, 16) include hyperadherence, enhanced biofilm formation, and increased antibiotic resistance (1, 2, 4, 6). These colonies were recovered from respiratory samples of 33 (38%) of 86 CF patients followed for 2 years (3). We wanted to prospectively assess the presence of SCV of both S. aureus and P. aeruginosa in respiratory secretions collected from CF patients during a 3-month period and to correlate microbiology findings with important clinical and laboratory parameters.From 26 July to 29 October, 2000, conventional bacteriologic examinations of all respiratory specimens from our CF patients were complemented by a prospective screen for SCV of both S. aureus and P. aeruginosa. We examined 148 respiratory samples from 106 patients. Seven patients were excluded from analysis because of incomplete medical records, and one patient whose sputum grew SCV of both species was excluded for statistical reasons. Of the remaining 98 patients, 20 contributed more than one sample (two to six samples). For statistical reasons, we studied one sample per patient: either the first sample obtained or, for patients harboring SCV, the first sample that contained SCV. Clinical data and laboratory results were extracted from patients' charts using a standardized questionnaire. For parameters relating to weight (i.e., weight of an underweight patient as a percentage of predicted weight; the body mass index) and pulmonary function (percentage of predicted forced expiratory volume in 1 s [FEV 1 ] and partial pressure of arterial oxygen [PaO 2 ]), the highest value in the year preceding or following sample collection was evaluated. Antibiotic treatment for the preceding 36 months was studied. Patients without SCV served as controls. The study conformed to the policies outlined by the institutional review board of the University Hospital, Inselspital of Bern.Specimens were cultured on Schädler agar under anaerobic conditions and on mannitol salt agar under aerobic conditions for 48 h at 35°C (5). All visibl...

; 95% CI, 13 to 28%) and 14% (17/119; 95% CI, 9 to 22%), respectively, among Swiss-born patients. Using weighted logistic regression, we found weak evidence of an association between birth origin and transmission (adjusted odds ratio of 2.2 and 95% CI of 0.9 to 5.5 comparing Swiss-born patients to others). In conclusion, standard genotyping overestimated recent TB transmission in Switzerland compared to WGS, particularly among immigrants from regions with a high TB incidence, where genetically closely related strains often predominate. We recommend the use of WGS to identify transmission clusters in settings with a low incidence of TB.

To describe the serotype-specific epidemiology of colonizing and invasive Streptococcus pneumoniae isolates, which is important for vaccination strategies, we analyzed a total of 2,388 invasive and 1,540 colonizing S. pneumoniae isolates collected between January 2001 and December 2004 within two nationwide surveillance programs. We found that the relative rank orders of the most frequent serotypes (serotypes 1, 3, 4, 6B, 7F, 14, 19F, and 23F) differed among invasive and colonizing isolates. Serotypes 1, 4, 5, 7F, 8, 9V, and 14 had increased invasive potential, and serotypes/serogroups 3, 6A, 7, 10, 11, 19F, and 23F were associated with colonization. The proportion of pediatric serotypes was higher among children <5 years old (48.5%) and persons >64 years old (34.1%) than among other age groups (29.1%); it was also higher in West Switzerland (40.2%) than in other geographic regions (34.7%). Likewise, serotype-specific proportions of penicillin-resistant isolates for types 6B, 9V, 14, and 19F were significantly higher in West Switzerland. The relative frequency of pediatric serotypes corresponded with antibiotic consumption patterns. We conclude that the epidemiology of invasive and colonizing S. pneumoniae isolates is influenced by the serotype-specific potential for invasiveness, and therefore, surveillance programs should include colonizing and invasive S. pneumoniae isolates. Antibiotic selection pressure determines the serotype distribution in different age groups and geographic regions and therefore the expected direct and indirect effects of the 7-valent conjugate vaccine.

Gram-positive bacteria predominated in this study. We showed that the use of prophylactic antibiotics in pediatric cancer patients was associated with increased resistance rates, which needs further study. The strategy for empiric antimicrobial therapy for febrile neutropenia should be adapted to local antibiotic resistance patterns.