Circulating sex-steroids and Staphylococcus aureus nasal carriage in a general female population

Objective Staphylococcus aureus is a major human pathogen, and nasal carriers have an increased risk for infection and disease. The exploration of host determinants for nasal carriage is relevant to decrease infection burden. Former studies demonstrate lower carriage prevalence in women and among users of progestin-only contraceptives. The aim of this study was to investigate the possible associations between circulating sex-steroid hormones and nasal carriage of Staphylococcus aureus in a general population. Methods In the population-based sixth Tromsø study (2007-2008) nurses collected nasal swab samples from 724 women aged 30-87 not using any exogenous hormones, and 700 of the women had a repeated nasal swab taken (median interval 28 days). We analysed a panel of serum sex-steroids by Liquid Chromatography tandem Mass Spectrometry, and collected information about lifestyle, health and anthropometric measures. Multivariable logistic regression was used to study the association between circulating sex-steroids and Staphylococcus aureus carriage (one swab) and persistent carriage (two swabs), while adjusting for potential confounding factors. Women in luteal phase were excluded in the analysis of androgens. Results Staphylococcus aureus persistent nasal carriage prevalence was 22%. One standard deviation increase in testosterone and bioavailable testosterone was associated with lower odds of persistent nasal carriage, (OR=0.57; 95% CI=0.35-0.92 and OR=0.52, 95%CI=0.30-0.92), respectively. Analysis stratified by menopause gave similar findings. Persistent carriers had lower average levels of androstenedione and dehydroepiandrosterone, however not statistically significant. Conclusion This large population-based study supports that women with lower levels of circulating testosterone may have increased probability of Staphylococcus aureus persistent carriage.

Accessory genome dynamics and structural variation of Shigella from persistent infections

Shigellosis is a diarrhoeal disease caused mainly by Shigella flexneri and Shigella sonnei. Infection from Shigella is thought to be largely self-limiting, with short- to medium- term and serotype-specific immunity provided following clearance. However, cases of men who have sex with men (MSM) associated shigellosis have been reported where Shigella of the same serotype were serially sampled from individuals between 1 to 1862 days apart, possibly due to persistent carriage or reinfection with the same serotype. Here, we investigate the accessory genome dynamics of MSM associated S. flexneri and S. sonnei isolates serially sampled from individual patients at various days apart. We find that pairs likely associated with persistent carriage infection and with smaller single nucleotide polymorphism (SNP) distance, demonstrated significantly less variation in accessory genome content than pairs likely associated with reinfection and with greater SNP-distance. We also observed evidence of antimicrobial resistance (AMR) acquisition during persistent Shigella infection, specifically the gain of extended spectrum beta-lactamase genes in two pairs associated with persistent carriage. Finally, we explored chromosomal structural variations and rearrangements in seven (5 chronic and 2 reinfection associated) pairs of S. flexneri 3a isolates from a MSM-associated epidemic sublineage, which revealed variations at several common regions across pairs. These variations were mediated by insertion sequence (IS) elements which facilitated plasticity of genetic material with a distinct predicted functional profile. This study provides insight on the variation of accessory genome dynamics and large structural genomic changes in Shigella during persistent infection.ImportanceShigella spp are Gram-negative bacteria that are the etiological agent of shigellosis, the second most common cause of diarrhoeal illness globally, particularly among children under the age of 5 in low-income countries. In high-income countries, an alternative transmission pathway of sexually transmissible disease among men who have sex with men (MSM) is emerging as the dominant presentation of the disease. Within MSM we have captured prolonged infection and/or recurrent infection with shigellae of the same serotype, challenging the belief that Shigella infection is short-lived, and confers homologous serotypic immunity. Using this recently-emerged transmission scenario we comprehensively characterise the genomic changes that occur over the course of individual infection with Shigella and uncover a distinct functional profile of variable genome regions in these globally important pathogens.

Likelihood of persistent carriage of carbapenem-resistant Acinetobacter baumannii on readmission in previously identified carriers

Patients with carbapenem-resistant Acinetobacter baumannii-positive clinical cultures during a prior hospitalization were screened using high sensitivity methods upon first readmission. Of 38 patients, 31.6% screened positive; 42% screened positive within 2 months from discharge, and 14% screened positive more than 5 months from discharge. Carriage was persistent up to 285 days.

Patterns and predictors ofStaphylococcus aureuscarriage during the first year of life; a longitudinal study

Objectives’To determine the patterns ofS. aureuscarriage in the first year of life, its determinants and dynamics of transmission between mothers and infants.MethodsProspective longitudinal cohort study ofS. aureuscarriage among mothers and their infants. Monthly screenings from pregnancy/birth through the first year of the infant’s life. Medical and lifestyle data was collected. InfantS. aureuscarriage was detected by rectal and nasal swabs and maternal carriage by nasal swabs. Multivariate analysis and an NLMixed model were used to determine predictors of carriage andS. aureuspersistence.Results130S. aureuscarrier women and their 132 infants were included in the study. 93% of the infants acquiredS. aureussometime during the first year of life, 64% of them acquired the maternal strain, mostly (66%) during the first month of life. 70 women (52.50%) and 17 infants (14%) carriedS. aureuspersistently. Early acquisition ofS. aureuscarriage was associated with longer duration of initial carriage and was the most significant predictor ofS. aureuspersistence, while day-care center attendance was negatively associated with persistent carriage.ConclusionsEarly acquisition ofS. aureus, mostly from the mother, is an important determinant of carriage persistence in infancy.

Evolution of Nasal Carriage of Methicillin-Resistant Coagulase-Negative Staphylococci in a Remote Population

ABSTRACTNasal carriage of methicillin-resistant coagulase-negative staphylococci (MR-CoNS) is highly prevalent in community subjects, but its dynamic has been little investigated. Nasal swabbing was performed in 2006 and 2008 in 154 Amerindians living isolated in French Guiana. MR-CoNS strains were identified and characterized by non-β-lactam susceptibility testing and staphylococcal cassette chromosomemecelement (SCCmec) typing, characterizing the associations ofccrandmecgene complex allotypes, and for MRStaphylococcus epidermidis(MRSE), multilocus variable number of tandem repeats analysis (MLVA) was used. The impact of sociodemographic and medical characteristics on the persistence of MR-CoNS carriage was assessed by bivariate analysis. Prevalence of MR-CoNS carriage was 50.6% in 2006 and 46.8% in 2008. The 274 MR-CoNS isolates, includingS. epidermidis(n= 89, 62 MLVA patterns),Staphylococcus haemolyticus(n= 78), andStaphylococcus hominis(n= 72), exhibited 41 distinctccrandmecgene complex associations. Persistent carriage (in 2006 and 2008), intermittent carriage (either in 2006 or 2008), and noncarriage were documented in 25.3, 47.4, and 27.3% of the participants, respectively. Persistent carriage of a given MRSE isolate was rarely observed (n= 8 isolates). Furthermore, no epidemiological factor, including antibiotic exposure, was associated with persistent carriage. The high diversity of MRSE clones and theirccrandmecgene complex associations contrasted with the high carriage rates in this isolated community, which might reflect the occurrence of SCCmecrearrangement and the generation of new MR-CoNS strains.

Outbreak of equine endometritis caused by a genotypically identical strain of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen that has been recognized as a cause of endometritis in mares. Pulsed field gel electrophoresis was used to characterize and compare isolates of P. aeruginosa from an outbreak of endometritis and unrelated isolates collected at the same time as the outbreak. The restriction endonuclease digestion patterns and antimicrobial resistance profiles of all outbreak isolates were identical. Therefore, a single strain of P. aeruginosa was responsible for the cases of endometritis. The unrelated isolates could be distinguished from the outbreak strain using the techniques outlined in the present study. The results establish that this pathogen was not venereally transmitted between all the horses from which it was isolated, but rather must have been disseminated, at least initially, from a contaminated water source. Once the water used to clean the mares and stallions was replaced, there were no further reports of endometritis caused by this organism on the affected stud. Furthermore, the fertility of the stallions was not affected, in spite of persistent carriage for 1 to 2 months. The current study has shown that the use of pulsed field gel electrophoresis has considerable value in epidemiological investigations of equine urogenital tract infections with P. aeruginosa.