Staphylococcus aureus nasal carriage as a marker for subsequent staphylococcal infections in intensive care unit patients.
ABSTRACT From January to December 1994, 752 consecutive patients admitted to intensive care units (ICU) for more than two days were studied prospectively for Staphylococcus aureus colonization and infection. Nasal swabs were obtained at admission and weekly during the ICU stay. At ICU admission 166 patients (22.1%) were Staphylococcus aureus nasal carriers, while 586 were free of nasal colonization. Of the 166 nasal carriers, 163 harbored methicillin-sensitive Staphylococcus aureus (MSSA) and three methicillin-resistant Staphylococcus aureus (MRSA). During the ICU stay 24 of the 586 noncolonized patients became nasal carriers (11 MSSA and 13 MRSA), and one nasal carrier initially colonized by MSSA was reconlonized by MRSA. Staphylococcal infections were documented in 51 (6.8%) of the total 752 patients. After 14 days of ICU stay, the probability of developing staphylococcal infections was significantly higher for those patients who were nasal carriers at ICU admission than for those found to be initially negative (relative risk 59.6, 95% CI 20.37-184.32; p < 0.0001). In patients with ICU-acquired nasal colonization, most infections were documented prior to or at the time of the detection of the nasal colonization; thus, in this group of patients nasal carriage showed a lower predictive value for subsequent Staphylococcus aureus infections that that described classically. Paired isolates of nasal colonizing and clinical strains were studied by pulsed-field gel electrophoresis (PFGE) and mecA polymorphism analysis in 30 patients; identity was demonstrated in all but two patients. The results suggest that, outside the setting of an outbreak of MRSA, the detection of Staphylococcus aureus nasal carriers on admission may be particularly useful in identifying those patients who are at high risk for developing staphylococcal infections during their ICU stay.
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ABSTRACT: In apparent contrast to its invasive potential Staphylococcus aureus colonizes the anterior nares of 20-80% of the human population. The relationship between host and microbe appears particularly individualized and colonization status seems somehow predetermined. After decolonization, persistent carriers often become re-colonized with their prior S. aureus strain, whereas non-carriers resist experimental colonization. Efforts to identify factors facilitating colonization have thus far largely focused on the microorganism rather than on the human host. The host responds to S. aureus nasal colonization via local expression of anti-microbial peptides, lipids, and cytokines. Interplay with the co-existing microbiota also influences colonization and immune regulation. Transient or persistent S. aureus colonization induces specific systemic immune responses. Humoral responses are the most studied of these and little is known of cellular responses induced by colonization. Intriguingly, colonized patients who develop bacteremia may have a lower S. aureus-attributable mortality than their non-colonized counterparts. This could imply a staphylococcal-specific immune "priming" or immunomodulation occurring as a consequence of colonization and impacting on the outcome of infection. This has yet to be fully explored. An effective vaccine remains elusive. Anti-S. aureus vaccine strategies may need to drive both humoral and cellular immune responses to confer efficient protection. Understanding the influence of colonization on adaptive response is essential to intelligent vaccine design, and may determine the efficacy of vaccine-mediated immunity. Clinical trials should consider colonization status and the resulting impact of this on individual patient responses. We urgently need an increased appreciation of colonization and its modulation of host immunity.Frontiers in Immunology 01/2014; 4:507.
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ABSTRACT: Staphylococcal disease represents a universal burden including acute, life-threatening infections as well as chronic infections usually associated with foreign materials. Infections occur notably in permanent carriers of Staphylococcus aureus. To date, all the attempts to develop an efficacious vaccine against S. aureus have failed. Failures in vaccine clinical trials might be related to a focus on single targets and development of humoral-based vaccines rather than vaccines with a combination of antigens stimulating both humoral and cellular immunity. The end points of these unsuccessful trials were a reduction in mortality or bacteremia, whereas the patient's decolonization was not assessed. Adopting the latter point of view, the aim of this article is to discuss nasal mucosal decolonization as a complementary marker of vaccine efficacy for clinical research in vaccine development.Expert Review of Vaccines 10/2013; · 4.22 Impact Factor
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ABSTRACT: PURPOSES: Methicillin-resistant Staphylococcus aureus (MRSA) colonization is consistently rising. The question whether the MRSA colonization places the patients at higher risk, requiring higher levels of care when being admitted, has never been studied. We conducted this study to determine the impact of MRSA colonization status on the required level of care upon admission to hospital. BASIC PROCEDURES: We conducted a retrospective chart review in 1000 plus-bed tertiary care academic institute. Our study population composed of all the patients who were admitted from January 2011 to March 2011. We found 7413 pediatric admissions that were identified as the study subjects. We assessed and divided study subjects into 2 groups, MRSA colonized and MRSA noncolonized. Methicillin-resistant Staphylococcus aureus-colonized patients were further grouped into those admitted to either pediatric intensive care unit (PICU) or ward, and these 2 groups were analyzed using P value, Fisher exact test, relative risks, and odds ratios. MAIN FINDINGS: We found a total of 7413 admissions, 753 were admitted in PICU (average pediatric risk of mortality score 18), and 6660 were admitted in pediatric wards (average pediatric risk of mortality score, 5). We found that MRSA colonization was 20 (2.66%) of 753 in PICU admissions and 155 (2.33%) of 6660 in ward admissions. We found that rate of admissions difference between MRSA colonized and MRSA noncolonized groups was clinically insignificant (P > .05). PRINCIPAL CONCLUSIONS: We conclude that MRSA colonization does not increase the need of care in PICU upon admission to hospital from emergency department. However, these preliminary results need to be confirmed through larger, multicenter, and multicountry data analysis.The American journal of emergency medicine 02/2013; · 1.54 Impact Factor