Intestinal carriage of Staphylococcus aureus: How does its frequency compare with that of nasal carriage and what is its clinical impact?

The bacterial species Staphylococcus aureus, including its methicillin-resistant variant (MRSA), finds its primary ecological niche in the human nose, but is also able to colonize the intestines and the perineal region. Intestinal carriage has not been widely investigated despite its potential clinical impact. This review summarizes literature on the topic and sketches the current state of affairs from a microbiological and infectious diseases' perspective. Major findings are that the average reported detection rate of intestinal carriage in healthy individuals and patients is 20% for S. aureus and 9% for MRSA, which is approximately half of that for nasal carriage. Nasal carriage seems to predispose to intestinal carriage, but sole intestinal carriage occurs relatively frequently and is observed in 1 out of 3 intestinal carriers, which provides a rationale to include intestinal screening for surveillance or in outbreak settings. Colonization of the intestinal tract with S. aureus at a young age occurs at a high frequency and may affect the host's immune system. The frequency of intestinal carriage is generally underestimated and may significantly contribute to bacterial dissemination and subsequent risk of infections. Whether intestinal rather than nasal S. aureus carriage is a primary predictor for infections is still ill-defined

Methicillin-Resistant Staphylococcus aureus Infection and Hospitalization in High-Risk Patients in the Year following Detection

Many studies have evaluated methicillin-resistant Staphylococcus aureus (MRSA) infections during single hospitalizations and subsequent readmissions to the same institution. None have assessed the comprehensive burden of MRSA infection in the period after hospital discharge while accounting for healthcare utilization across institutions.We conducted a retrospective cohort study of adult patients insured by Harvard Pilgrim Health Care who were newly-detected to harbor MRSA between January 1991 and December 2003 at a tertiary care medical center. We evaluated all MRSA-attributable infections associated with hospitalization in the year following new detection, regardless of hospital location. Data were collected on comorbidities, healthcare utilization, mortality and MRSA outcomes. Of 591 newly-detected MRSA carriers, 23% were colonized and 77% were infected upon detection. In the year following detection, 196 (33%) patients developed 317 discrete and unrelated MRSA infections. The most common infections were pneumonia (34%), soft tissue (27%), and primary bloodstream (18%) infections. Infections occurred a median of 56 days post-detection. Of all infections, 26% involved bacteremia, and 17% caused MRSA-attributable death. During the admission where MRSA was newly-detected, 14% (82/576) developed subsequent infection. Of those surviving to discharge, 24% (114/482) developed post-discharge infections in the year following detection. Half (99/185, 54%) of post-discharge infections caused readmission, and most (104/185, 55%) occurred over 90 days post-discharge.In high-risk tertiary care patients, newly-detected MRSA carriage confers large risks of infection and substantial attributable mortality in the year following acquisition. Most infections occur post-discharge, and 18% of infections associated with readmission occurred in hospitals other than the one where MRSA was newly-detected. Despite gains in reducing MRSA infections during hospitalization, the risk of MRSA infection among critically and chronically ill carriers persists after discharge and warrants targeted prevention strategies

Persistent Staphylococcus aureus Colonization Is Not a Strongly Heritable Trait in Amish Families

About 20% of adults are persistently colonized with S. aureus in the anterior nares. Host genetic factors could contribute susceptibility to this phenotype. The objective of this study was to determine whether the phenotype of persistent S. aureus colonization aggregates in family members who live in different households. Healthy adults and their eligible same sex siblings who lived in different households were recruited from the Old Order Amish of Lancaster, Pennsylvania. All participants had two cultures of the anterior nares to determine if they were persistently colonized with S. aureus. Three hundred and ninety eight participants finished the study, of whom 166 were index cases and 232 were siblings of index cases. Eighteen per cent (71/398) of all participants and 17% (29/166) of index cases were persistently colonized with S. aureus. Twenty two per cent (8/36) of siblings of persistently colonized index cases were persistently colonized with S. aureus compared to 17% (34/196) of siblings of non-persistently colonized index cases, yielding a prevalence rate ratio of 1.28 (95% CI: 0.65–2.54, p = 0.64) and sibling relative risk of 1.25 (95% CI: 0.65–2.38, p = 0.51). The heritability of persistent colonization was 0.19±0.21 (p = 0.31). Persistent S. aureus colonization does not strongly aggregate in Amish family members in different households and heritability is low, suggesting that environmental factors or acquired host factors are more important than host genetic factors in determining persistent S. aureus colonization in this community

Human Rhinovirus Infections in Rural Thailand: Epidemiological Evidence for Rhinovirus as Both Pathogen and Bystander

BACKGROUND: We describe human rhinovirus (HRV) detections in SaKaeo province, Thailand. METHODS: From September 1, 2003-August 31, 2005, we tested hospitalized patients with acute lower respiratory illness and outpatient controls without fever or respiratory symptoms for HRVs with polymerase chain reaction and molecularly-typed select HRVs. We compared HRV detection among hospitalized patients and controls and estimated enrollment adjusted incidence. RESULTS: HRVs were detected in 315 (16%) of 1919 hospitalized patients and 27 (9.6%) of 280 controls. Children had the highest frequency of HRV detections (hospitalized: <1 year: 29%, 1-4 year: 29%, ≥ 65 years: 9%; controls: <1 year: 24%, 1-4 year: 14%, ≥ 65 years: 2.8%). Enrollment adjusted hospitalized HRV detection rates were highest among persons aged <1 year (1038/100,000 persons/year), 1-4 years (457), and ≥ 65 years (71). All three HRV species were identified, HRV-A was the most common species in most age groups including children aged <1 year (61%) and all adult age groups. HRV-C was the most common species in the 1-4 year (51%) and 5-19 year age groups (54%). Compared to controls, hospitalized adults (≥ 19 years) and children were more likely to have HRV detections (odds ratio [OR]: 4.8, 95% confidence interval [CI]: 1.5, 15.8; OR: 2.0, CI: 1.2, 3.3, respectively) and hospitalized children were more likely to have HRV-A (OR 1.7, CI: 0.8, 3.5) or HVR-C (OR 2.7, CI: 1.2, 5.9) detection. CONCLUSIONS: HRV rates were high among hospitalized children and the elderly but asymptomatic children also had substantial HRV detection. HRV (all species), and HRV-A and HRV-C detections were epidemiologically-associated with hospitalized illness. Treatment or prevention modalities effective against HRV could reduce hospitalizations due to HRV in Thailand

Toxoplasmosis-Related Knowledge and Practices Among Pregnant Women in the United States

Background: Infection with Toxoplasma gondii during pregnancy can lead to severe illness in the fetus. Many T. gondii infections are preventable by simple hygienic measures. Methods: We surveyed pregnant women in the US to determine their knowledge about toxoplasmosis and their practices to prevent infection. Volunteer obstetricians selected to be demographically representative of the American College of Obstetricians and Gynecologists recruited the participants. Results: Of 403 women responding to the survey, 48% indicated that they had heard or seen information about toxoplasmosis; however, only 7% were aware of being tested for the disease. Forty percent of responding women knew that toxoplasmosis is caused by an infection, but 21% thought that a poison causes it. The highest level of knowledge was about cats and T. gondii ; 61% responded that the organism is shed in the feces of infected cats and 60% responded that people could acquire toxoplasmosis by changing cat litter. There was a low level of knowledge about other risk factors; only 30% of the women were aware that T. gondii may be found in raw or undercooked meat. Nevertheless, a high percentage of women indicated that they do not eat undercooked meat during pregnancy and that they practice good hygienic measures such as washing their hands after handling raw meat, gardening or changing cat litter. Conclusion: Except for the risk of transmission from cats, knowledge among pregnant women about toxoplasmosis is low. However, toxoplasmosis-preventive practices are generally good, suggesting that providers should continue to offer education about practices that help prevent foodborne diseases in general as well as information about preventing toxoplasmosis specifically

Case-case-control study on factors associated with vanB vancomycin-resistant and vancomycin-susceptible enterococcal bacteraemia

BACKGROUND: Enterococci are a major cause of healthcare-associated infection. In Australia, vanB vancomycin-resistant enterococci (VRE) is the predominant genotype. There are limited data on the factors linked to vanB VRE bacteraemia. This study aimed to identify factors associated with vanB VRE bacteraemia, and compare them with those for vancomycin-susceptible enterococci (VSE) bacteraemia. METHODS: A case-case-control study was performed in two tertiary public hospitals in Victoria, Australia. VRE and VSE bacteraemia cases were compared with controls without evidence of enterococcal bacteraemia, but may have had infections due to other pathogens. RESULTS: All VRE isolates had vanB genotype. Factors associated with vanB VRE bacteraemia were urinary catheter use within the last 30 days (OR 2.86, 95% CI 1.09-7.53), an increase in duration of metronidazole therapy (OR 1.65, 95% CI 1.17-2.33), and a higher Chronic Disease Score specific for VRE (OR 1.70, 95% CI 1.05-2.77). Factors linked to VSE bacteraemia were a history of gastrointestinal disease (OR 2.29, 95% CI 1.05-4.99) and an increase in duration of metronidazole therapy (OR 1.23, 95% CI 1.02-1.48). Admission into the haematology/oncology unit was associated with lower odds of VSE bacteraemia (OR 0.08, 95% CI 0.01-0.74). CONCLUSIONS: This is the largest case-case-control study involving vanB VRE bacteraemia. Factors associated with the development of vanB VRE bacteraemia were different to those of VSE bacteraemia

Empiric Antibiotic Therapy for Staphylococcus aureus Bacteremia May Not Reduce In-Hospital Mortality: A Retrospective Cohort Study

Appropriate empiric therapy, antibiotic therapy with in vitro activity to the infecting organism given prior to confirmed culture results, may improve Staphylococcus aureus outcomes. We aimed to measure the clinical impact of appropriate empiric antibiotic therapy on mortality, while statistically adjusting for comorbidities, severity of illness and presence of virulence factors in the infecting strain.We conducted a retrospective cohort study of adult patients admitted to a tertiary-care facility from January 1, 2003 to June 30, 2007, who had S. aureus bacteremia. Time to appropriate therapy was measured from blood culture collection to the receipt of antibiotics with in vitro activity to the infecting organism. Cox proportional hazard models were used to measure the association between receipt of appropriate empiric therapy and in-hospital mortality, statistically adjusting for patient and pathogen characteristics.Among 814 admissions, 537 (66%) received appropriate empiric therapy. Those who received appropriate empiric therapy had a higher hazard of 30-day in-hospital mortality (Hazard Ratio (HR): 1.52; 95% confidence interval (CI): 0.99, 2.34). A longer time to appropriate therapy was protective against mortality (HR: 0.79; 95% CI: 0.60, 1.03) except among the healthiest quartile of patients (HR: 1.44; 95% CI: 0.66, 3.15).Appropriate empiric therapy was not associated with decreased mortality in patients with S. aureus bacteremia except in the least ill patients. Initial broad antibiotic selection may not be widely beneficial