Spread of a methicillin-resistant Staphylococcus aureus ST80 strain in the community of the northern Netherlands

Infections caused by community-acquired methicillin-resistant Staphylococcus aureus (MRSA) are emerging as a major public health problem. In this study, we describe the distribution of 54 Panton-Valentine leucocidin (PVL)-carrying MRSA isolates in the northern Netherlands between 1998 and 2005, of which 43 (80%) consisted of the European PVL-positive strain multi locus sequence type 80 with staphylococcal cassette chromosome mec type IVc (ST80). Individual cases and small clusters of ST80 predominated in the community (74%), but ST80 was also found in nursing homes (16%) and hospitals (9%). Long-term carriership (months to years) and reinfection of patients with ST80 has probably led to the strain spreading in the community and subsequently to further migration to health care environments

Persistence survey of Toxic Shock Syndrome toxin-1 producing Staphylococcus aureus and serum antibodies to this superantigen in five groups of menstruating women

Background: Menstrual Toxic Shock Syndrome (mTSS) is thought to be associated with the vaginal colonization with specific strains of Staphylococcus aureus TSST-1 in women who lack sufficient antibody titers to this toxin. There are no published studies that examine the seroconversion in women with various colonization patterns of this organism. Thus, the aim of this study was to evaluate the persistence of Staphylococcus aureus colonization at three body sites (vagina, nares, and anus) and serum antibody to toxic shock syndrome toxin-producing Staphylococcus aureus among a small group of healthy, menstruating women evaluated previously in a larger study. Methods: One year after the completion of that study, 311 subjects were recalled into 5 groups. Four samples were obtained from each participant at several visits over an additional 6-11 month period: 1) an anterior nares swab; 2) an anal swab; 3) a vagina swab; and 4) a blood sample. Gram stain, a catalase test, and a rapid S. aureus-specific latex agglutination test were performed to phenotypically identify S. aureus from sample swabs. A competitive ELISA was used to quantify TSST-1 production. Human TSST-1 IgG antibodies were determined from the blood samples using a sandwich ELISA method. Results: We found only 41% of toxigenic S. aureus and 35.5% of non-toxigenic nasal carriage could be classified as persistent. None of the toxigenic S. aureus vaginal or anal carriage could be classified as persistent. Despite the low persistence of S. aureus colonization, subjects colonized with a toxigenic strain were found to display distributions of antibody titers skewed toward higher titers than other subjects. Seven percent (5/75) of subjects became seropositive during recall, but none experienced toxic shock syndrome-like symptoms. Conclusions: Nasal carriage of S. aureus appears to be persistent and the best predicator of subsequent colonization, whereas vaginal and anal carriage appear to be more transient. From these findings, it appears that antibody titers in women found to be colonized with toxigenic S. aureus remained skewed toward higher titers whether or not the colonies were found to be persistent or transient in nature. This suggests that colonization at some point in time is sufficient to elevate antibody titer levels and those levels appear to be persistent. Results also indicate that women can become seropositive without experiencing signs or symptoms of toxic shock syndrome

Within-host evolution of Staphylococcus aureus during asymptomatic carriage

Background Staphylococcus aureus is a major cause of healthcare associated mortality, but like many important bacterial pathogens, it is a common constituent of the normal human body flora. Around a third of healthy adults are carriers. Recent evidence suggests that evolution of S. aureus during nasal carriage may be associated with progression to invasive disease. However, a more detailed understanding of within-host evolution under natural conditions is required to appreciate the evolutionary and mechanistic reasons why commensal bacteria such as S. aureus cause disease. Therefore we examined in detail the evolutionary dynamics of normal, asymptomatic carriage. Sequencing a total of 131 genomes across 13 singly colonized hosts using the Illumina platform, we investigated diversity, selection, population dynamics and transmission during the short-term evolution of S. aureus. Principal Findings We characterized the processes by which the raw material for evolution is generated: micro-mutation (point mutation and small insertions/deletions), macro-mutation (large insertions/deletions) and the loss or acquisition of mobile elements (plasmids and bacteriophages). Through an analysis of synonymous, non-synonymous and intergenic mutations we discovered a fitness landscape dominated by purifying selection, with rare examples of adaptive change in genes encoding surface-anchored proteins and an enterotoxin. We found evidence for dramatic, hundred-fold fluctuations in the size of the within-host population over time, which we related to the cycle of colonization and clearance. Using a newly-developed population genetics approach to detect recent transmission among hosts, we revealed evidence for recent transmission between some of our subjects, including a husband and wife both carrying populations of methicillin-resistant S. aureus (MRSA). Significance This investigation begins to paint a picture of the within-host evolution of an important bacterial pathogen during its prevailing natural state, asymptomatic carriage. These results also have wider significance as a benchmark for future systematic studies of evolution during invasive S. aureus disease

Estudo comparativo da prevalência de Staphylococcus aureus importado para as unidades de terapia intensiva de hospital universitário, Pernambuco, Brasil Comparative study on the prevalence of Staphylococcus aureus imported to intensive care units of a university hospital, Pernambuco, Brazil

O Staphylococcus aureus é um dos principais patógenos que coloniza indivíduos saudáveis na comunidade e responde por infecções em pacientes hospitalizados. Um estudo transversal foi realizado para determinar a prevalência de S. aureus meticilina-resistente e sensível entre 231 pacientes, internados entre janeiro e abril de 2003, nas unidades de terapia intensiva (UTIs) do Hospital Universitário Oswaldo Cruz, assim como os possíveis fatores associados à colonização. Foram coletadas secreções de narinas, axilas, região perineal e dermatoses com soluções de continuidade, de todos os pacientes, nas primeiras 48 horas de internamento nas UTIs. O material foi semeado em meios de cultura adequados. A prevalência de S. aureus igualou-se a 37,7% (87/231), sendo 13% (30/231) meticilina-resistente e 24,8% (57/231) meticilina-sensível. Idade, sexo, uso de antibioticoterapia, corticoterapia, motivo e local do internamento não se associaram à presença do S. aureus ou do meticilina-resistente. Houve associação significante entre procedência hospitalar e colonização por S. aureus, independente da cepa, e entre internamento anterior e presença do S. aureus meticilina-resistente. As narinas foram o sítio de colonização mais significante, por S. aureus meticilina-resistente (47/57=82,4%) e sensível (23/30=76,7%). Foi alta a prevalência do S. aureus (meticilina resistente ou sensível), assim como do meticilina-resistente entre os pacientes das UTIs deste hospital. Estudos futuros poderão comprovar se os resultados aqui descritos e medidas de rastreamento para S. aureus poderiam ser adotadas, de forma prospectiva, para se avaliar o risco, assim como a magnitude do efeito, no controle de infecções hospitalares provocadas por estes patógenos.<br>Staphylococcus aureus is the most important pathogen that colonizes healthy individuals in the community and is responsible for infections in hospitalized patients. A cross-sectional study was carried out to determine the prevalence of methicillin-resistant and sensitive S. aureus, in 231 patients, hospitalized from January to April 2003, in the Intensive Care Units (ICU) of Hospital Universitário Oswaldo Cruz, as well as possible factors associated with colonization. Secretions, from the anterior nostrils, armpits, perineum and dermatosis with continuity solutions, were collected from all patients, within the first 48 h of admission at the ICU. These samples were spread on appropriate media. The prevalence of S. aureus was 37.7% (87/231), of which 13% (30/231) methicillin-resistant and 24.8% (57/231) methicillin-sensitive. Age, gender, antibiotic therapy, corticoid therapy and cause and place of hospitalization were not associated to colonization by S. aureus or methicillin-resistance. There was a significant association between hospital of origin and S. aureus colonization, regardless of strain, as well as between previous hospitalization and the presence of methicillin-resistant S. aureus. Regardless of strain, nostrils were the most significant colonization site for methicillin-resistant (47/57=82.4%) and methicillin-sensitive S. aureus (23/30=76.7%). There was a high prevalence of S aureus, (methicillin resistant or sensitive), as well as of methicillin resistance among ICU patients in this hospital. Future studies may prove the results reported here and screening routines for S. aureus should be adopted, prospectively, to evaluate risk, as well as the magnitude of the effect, on the control of hospital infections caused by these pathogens