Colonization of healthy children by Moraxella catarrhalis is characterized by genotype heterogeneity, virulence gene diversity and co-colonization with Haemophilus influenzae.

The colonization dynamics of Moraxella catarrhalis were studied in a population comprising 1079 healthy children living in Rotterdam, The Netherlands (the Generation R Focus cohort). A total of 2751 nasal swabs were obtained during four clinic visits timed to take place at 1.5, 6, 14 and 24 months of age, yielding a total of 709 M. catarrhalis and 621 Haemophilus influenzae isolates. Between January 2004 and December 2006, approximate but regular 6-monthly cycles of colonization were observed, with peak colonization incidences occurring in the autumn/winter for M. catarrhalis, and winter/spring for H. influenzae. Co-colonization was significantly more likely than single-species colonization with either M. catarrhalis or H. influenzae, with genotypic analysis revealing no clonality for co-colonizing or single colonizers of either bacterial species. This finding is especially relevant considering the recent discovery of the importance of H. influenzae-M. catarrhalis quorum sensing in biofilm formation and host clearance. Bacterial genotype heterogeneity was maintained over the 3-year period of the study, even within this relatively localized geographical region, and there was no association of genotypes with either season or year of isolation. Furthermore, chronological and genotypic diversity in three immunologically important M. catarrhalis virulence genes (uspA1, uspA2 and hag/mid) was also observed. This study indicates that genotypic variation is a key factor contributing to the success of M. catarrhalis colonization of healthy children in the first years of life. Furthermore, variation in immunologically relevant virulence genes within colonizing populations, and even within genotypically identical M. catarrhalis isolates, may be a result of immune evasion by this pathogen. Finally, the factors facilitating M. catarrhalis and H. influenzae co-colonization need to be further investigated.

Comparative activity of telavancin and other antimicrobial agents against methicillin-resistant Staphylococcus aureus isolates collected from 1991 to 2006.

BACKGROUND: Increasingly frequent reports of vancomycin treatment failures for serious methicillin-resistant Staphylococcus aureus (MRSA) infections provide impetus for comparative in vitro studies to assess the activity of newer antimicrobial agents against a range of MRSA isolates. METHODS: A sample of 168 MRSA derived from a long-term MRSA collection was subjected to susceptibility testing to telavancin, daptomycin, linezolid, tigecycline and vancomycin by broth micro-dilution. Data were reviewed for sporadic occurrence of isolates with reduced susceptibility. Analyses were performed to test for temporal trends toward decreasing susceptibility and to compare susceptibility of isolates from different infection sites. RESULTS: No MRSA isolate from any time period was resistant to test antibiotics. For daptomycin, linezolid and tigecycline, there were no susceptibility differences between the pre- and postclinical availability periods. All newer agents were active against MRSA isolates with minimum inhibitory concentrations (MICs) of vancomycin >1 mg/l, but there were significant correlations in susceptibility among several pairs of antibiotics. CONCLUSIONS: Telavancin and other newer antistaphylococcal agents were fully active against MRSA from various infection sites including isolates with vancomycin MIC >1 mg/l.

bro {beta}-lactamase and antibiotic resistances in a global cross-sectional study of Moraxella catarrhalis from children and adults.

OBJECTIVES: To compare and contrast the geographic and demographic distribution of bro beta-lactamase and antibiotic MIC(50/90) for 1440 global Moraxella catarrhalis isolates obtained from children and adults between 2001 and 2002. METHODS: One thousand four hundred and forty M. catarrhalis isolates originating from seven world regions were investigated. The isolates were recovered from 411 children <5 years of age and 1029 adults >20 years of age. PCR-restriction fragment length polymorphism (RFLP) was performed to determine bro prevalence and to distinguish between bro types. MIC values of 12 different antibiotics were determined using the CLSI (formerly NCCLS) broth microdilution method. RESULTS: Of the 1440 isolates, 1313 (91%) possessed the bro-1 gene and 64 (4%) possessed the bro-2 gene. Additionally, the prevalence of bro positivity between the child and adult age groups was significantly different (P < 0.0001), though bro-1 and bro-2 prevalences within age groups were not significantly different. Consistently higher beta-lactam MICs were observed for M. catarrhalis isolates originating in the Far East. Significant correlations in MICs were observed for several antibiotic combinations, including all five beta-lactams with each other, and among the two quinolones. CONCLUSIONS: The worldwide prevalence of bro gene carriage in clinical isolates of M. catarrhalis is now approaching 95%, with children significantly more likely to harbour bro-positive isolates than adults. Further, statistically significant differences in the distribution of beta-lactam MICs were observed between different world regions, particularly with respect to the Far East.

Modeling the spread of infectious disease using genetic information within a marked branching process.

Accurate assessment of disease dynamics requires a quantification of many unknown parameters governing disease transmission processes. While infection control strategies within hospital settings are stringent, some disease will be propagated due to human interactions (patient-to-patient or patient-to-caregiver-to-patient). In order to understand infectious transmission rates within the hospital, it is necessary to isolate the amount of disease that is endemic to the outside environment. While discerning the origins of disease is difficult when using ordinary spatio-temporal data (locations and time of disease detection), genotypes that are common to pathogens, with common sources, aid in distinguishing nosocomial infections from independent arrivals of the disease. The purpose of this study was to demonstrate a Bayesian modeling procedure for identifying nosocomial infections, and quantify the rate of these transmissions. We will demonstrate our method using a 10-year history of Morexella catarhallis. Results will show the degree to which pathogen-specific, genotypic information impacts inferences about the nosocomial rate of infection.

Blastomycosis in the mountainous region of northeast Tennessee.

BACKGROUND: In the United States, cases of human blastomycosis are largely described in defined geographic areas, with Mississippi reporting the highest prevalence of disease in the southeast region. The infection is uncommonly recognized in mountainous areas, and our previous report of blastomycosis in the southern Appalachian mountains of northeast Tennessee appeared to be an exception to the usual disease distribution. METHODS: Our current retrospective study was undertaken to determine whether blastomycosis has persisted as an endemic fungal infection in our northeast Tennessee geographic area and whether epidemiologic features have changed over a 25-year time period. RESULTS: Results show that clinical aspects of the disease have remained fairly constant with few exceptions; mass-type pulmonary lesions have become more common, and itraconazole has emerged as the therapy of choice. Most notably, however, are the observations that blastomycosis persists as a major endemic fungal infection in our mountain region, more than half of all cases occurring during the period from 1996 to 2005 were found in a core area centered on two counties, Washington and Unicoi; three of five counties surrounding the core counties experienced rate increases compared to our previous study. CONCLUSIONS: These findings suggest a further expansion of this endemic fungal disease beyond the core region.

A decline in mupirocin resistance in methicillin-resistant Staphylococcus aureus accompanied administrative control of prescriptions.

Susceptibility to mupirocin was assessed in methicillin-resistant Staphylococcus aureus isolates selected from eras corresponding to differences in usage rate and prescription policies at a Veterans Affairs medical center. The eras studied encompassed from the time of introduction of the drug to its widespread use, through recommended judicious use, and finally to subsequent stringent administrative control. Prescriptions declined from 3.0 to 0.1 per 1,000 patient days. Precipitous declines first in the numbers of isolates with high-level resistance (from 31% to 4%) and then in those with low-level resistance (from 26% to 10%) accompanied prescription control.

Responses to soils and a test for preadaptation to serpentine in Phacelia dubia (Hydrophyllaceae).

• Tests for adaptation to three different soils inhabited by subspecific taxa within Phacelia dubia and for preadaptation to a serpentine soil were conducted to examine the plausibility of an endemic-to-endemic evolutionary pathway. Each taxon performed optimally on its home soil, demonstrating edaphic specialization. None survived on the serpentine. • Hydroponic assays for tolerance to two serpentine factors, elevated magnesium: calcium and elevated nickel, were conducted on population samples and maternal half sib families. Performance was estimated by root length and rosette diameter while leaf dissection served as an indicator of developmental maturity. • Both nickel and magnesium: calcium of typical serpentine inhibited all three taxa. However, the granite outcrop endemic var. georgiana tolerated higher magnesium: calcium than other taxa, its tolerance exceeded that found on its home soil, and there was developmental variation among sibships. • The tolerance uncovered in the endemic var. georgiana suggests that a specialized endemic taxon may encompass variation that could lead to preadaptation to a novel habitat and therefore serve as the raw material for speciation rather than represent an evolutionary dead end.