Prevalence of nasal colonization and strain concordance in patients with community-associated Staphylococcus aureus skin and soft-tissue infections.
ABSTRACT: Determine the prevalence and relatedness of Staphylococcus aureus anterior nares colonization in individuals with community-associated staphylococcal skin and soft-tissue infection (SSTI).Observational cohort.US Army soldiers undergoing infantry training.Trainees who developed SSTI from May 2010 to January 2012.Participants underwent anterior nares culture at the time of presentation for purulent SSTI. We determined the prevalence of S. aureus nasal colonization and strain relatedness between colonizing and clinical isolates with pulsed-field gel electrophoresis (PFGE).We enrolled 1,203 SSTI participants, of whom 508 had culture-confirmed S. aureus SSTI. Overall, 70% (357/508) were colonized with S. aureus. Phenotypically, concordant colonization was more common with methicillin-susceptible S. aureus (MSSA; 56%; 122/218) than methicillin-resistant S. aureus (MRSA) SSTI (41%; 118/290; P < .01). With PFGE, 48% (121 of 254) of clinical-colonizing pairs were indistinguishable, and concordant colonization was more common with MRSA (53%; 92/173) than MSSA SSTI (36%; 29/81; P < .01). Restricting analysis to concomitant MRSA-MRSA or MSSA-MSSA pairs, 92% (92/100) of MRSA SSTI were indistinguishable, and 40% (29/72) MSSA SSTI were indistinguishable (P < .01). All 92 MRSA pairs were USA300.On the phenotypic level, concordant anterior nares colonization with incident staphylococcal SSTI is more common in MSSA than MRSA; however, the opposite is observed when accounting for molecular typing, and MRSA SSTI displays greater concordance. USA300 was responsible for strain concordance with MRSA SSTI. Studies are needed to examine the roles of nasal and extra-nasal carriage, colonization preceding infection, and increased virulence in the pathogenesis of MRSA SSTI.ClinicalTrials.gov identifier: NCT01105767.
Project description:In a field-based trial among military trainees, personal hygiene measures, including chlorhexidine (CHG) body wash, did not prevent overall and methicillin-resistant Staphylococcus aureus (MRSA) skin and soft-tissue infections (SSTI). We conducted a secondary analysis of anterior nares cultures obtained during the trial to evaluate the impact of hygiene measures on Staphylococcus aureus colonization. A cluster-randomized trial for SSTI prevention was conducted among U.S. Army infantry trainees from May 2010 to January 2012. There were three study groups with incrementally increasing education- and hygiene-based components: standard (S), enhanced standard (ES), and CHG. Anterior nares cultures were obtained from participants to determine the prevalence of S. aureus colonization. A total of 1,706 participants (469 S, 597 ES, and 640 CHG) without SSTI were included in the colonization analysis. Of those randomized to the CHG group, 360 (56.3%) reported frequent use of body wash. Frequent use of body wash had no effect on overall S. aureus colonization (53.3% versus 56.8% among infrequent/nonusers; P=0.25). MRSA colonization prevalence was marginally lower among frequent users (2.5% versus 4.7%; P=0.07). In multivariable analysis, the odds of MRSA colonization were lower among frequent users (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.16 to 0.77). This CHG-associated reduction was not observed when comparing colonization with USA300 to that with non-USA300 types (OR, 0.59; 95% CI, 0.06 to 5.76). Frequent use of CHG body wash was associated with a reduction in MRSA nasal colonization among high-risk military trainees. Topical chlorhexidine may contribute to MRSA SSTI prevention by reducing colonization. However, further studies evaluating the pathogenesis of SSTI are needed. (This study has been registered at ClinicalTrials.gov under registration no. NCT01105767).
Project description:Staphylococcus aureus is an important cause of infection, and brings additional concern with methicillin resistance. In addition, nasal methicillin-resistant Staphylococcus aureus (MRSA) colonization rates among health care workers are higher than that for general population. To determine the prevalence rate and risk factors for the colonization of S. aureus, including MRSA, among janitors working in hospitals in northern Taiwan, we conducted this study.Between June and August, 2014, a total of 186 janitors, 111 working in hospitals and 75 working in non-medical institutions, were recruited. Specimens were obtained from the nares of the subjects for the detection of S. aureus, with a questionnaire completed for each subject. All the S. aureus isolates, including MRSA and methicillin-susceptible S. aureus (MSSA), were further molecularly characterized.The nasal carriage rate of S. aureus was 15.3% for hospital janitors and 13.3% for non-medical janitors. The carriage rate of MRSA was 3.6% for hospital janitors and 1.3% for non-medical janitors. No statistically significant difference was found in the nasal carriage rate of S. aureus (p = 0.707) and MRSA (p = 0.65) between hospital janitors and non-medical janitors. Hospital janitors working in hospital more than 6 years and cleaning microbiologic laboratories were significantly associated with nasal S. aureus colonization. All 5 MRSA isolates carried either staphylococcal cassette chromosome type IV or V and three of them belonged to sequence type (ST) 59, the community clone prevailing in Taiwan. Of the 22 MSSA isolates, six pulsotypes were identified, with one major type for 14 isolates (shared by five STs) and another type for 4 isolates (all belonged to ST 188).Exposure to the hospital environment may not increase the nasal carriage rate of S. aureus, including MRSA, among janitors in hospitals in Taiwan. However, for janitors in the hospital setting, working for more than six years in hospital and cleaning laboratories may be risks factors for carrying S. aureus.
Project description:PURPOSE:Little is known about the molecular epidemiology of Staphylococcus aureus in Chinese neonatal intensive care units (NICUs). We describe the molecular epidemiology of S. aureus isolated from neonates on admission to Beijing Children's Hospital. METHODS:From May 2015-March 2016, nasal swabs were obtained on admission from 536 neonates. Cultures were also obtained from body sites with suspected infections. S. aureus isolates were characterized by staphylococcal chromosomal cassette (SCCmec) type, staphylococcal protein A (spa) type, multilocus sequence type (MLST), sasX gene, antimicrobial susceptibility and cytotoxicity. Logistic regression assessed risk factors for colonization. RESULTS:Overall, 92 (17%) infants were colonized with S. aureus and 20 (3.7%) were diagnosed with culture-positive S. aureus infection. Of the colonized infants, 70% (64/92) harbored methicillin-susceptible S. aureus (MSSA), 30% (28/92) harbored methicillin-resistant S. aureus (MRSA) while 70% (14/20) of infected infants were culture-positive for MRSA, 30% (6/20) were culture-positive for MSSA. Risk factors for colonization included female sex, age 7-28 days, higher birthweight (3270 IQR [2020-3655] grams) and vaginal delivery (p<0.05). The most common MRSA and MSSA clones were community-associated ST59-SCCmecIVa-t437 (60%) and ST188-t189 (15%), respectively. The sasX gene was not detected. Some MSSA isolates (16%) were penicillin-susceptible and some MRSA isolates (18%) were oxacillin-susceptible. MRSA and MSSA had similar cytotoxicity, but colonizing strains were less cytotoxic than strains associated with infections. CONCLUSIONS:S. aureus colonization was common in infants admitted to our NICU and two community-associated clones predominated. Several non-modifiable risk factors for S. aureus colonization were identified. These results suggest that screening infants for S. aureus upon admission and targeting decolonization of high-risk infants and/or those colonized with high-risk clones could be useful to prevent transmission.
Project description:Staphylococcus aureus colonization and infection occur more commonly among persons living or working in crowded conditions, but characterization of S. aureus colonization within medical communities in China is lacking. A total of 144 (15.4%, 144/935) S. aureus isolates, including 28 (3.0%, 28/935) MRSA isolates, were recovered from the nares of 935 healthy human volunteers residing on a Chinese medical college campus. All S. aureus isolates were susceptible to vancomycin, quinupristin/dalfopristin and linezolid but the majority were resistant to penicillin (96.5%), ampicillin/sulbactam (83.3%) and trimethoprim/sulfamethoxazole (93.1%). 82%, (23/28) of the MRSA isolates and 66% (77/116) of the MSSA isolates were resistant to multiple antibiotics, and 3 MRSA isolates were resistant to mupirocin--an agent commonly used for nasal decolonization. 16 different sequence types (STs), as well as SCCmec genes II, III, IVd, and V, were represented among MRSA isolates. We also identified, for the first time, two novel STs (ST1778 and ST1779) and 5 novel spa types for MRSA. MRSA isolates were distributed in different sporadic clones, and ST59-MRSA-VId- t437 was found within 3 MRSA isolates. Moreover, one isolate with multidrug resistance belonging to ST398-MRSA-V- t571 associated with animal infections was identified, and 3 isolates distributed in three different clones harbored PVL genes. Collectively, these data indicate a high prevalence of nasal MRSA carriage and molecular heterogeneity of S. aureus isolates among persons residing on a Chinese medical college campus. Identification of epidemic MRSA clones associated with community infection supports the need for more effective infection control measures to reduce nasal carriage and prevent dissemination of MRSA to hospitalized patients and health care workers in this community.
Project description:Staphylococcus aureus nasal carriage is a risk factor for subsequent infection. Estimates of colonization duration vary widely among studies, and factors influencing the time to loss of colonization, especially the impact of antibiotics, remain unclear. We conducted a prospective study on patients naive for S. aureus colonization in 4 French long-term-care facilities. Data on nasal colonization status and potential factors for loss of colonization were collected weekly. We estimated methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) colonization durations using the Kaplan-Meier method and investigated factors for loss of colonization using shared-frailty Cox proportional hazards models. A total of 285 S. aureus colonization episodes were identified in 149 patients. The median time to loss of MRSA or MSSA colonization was 3 weeks (95% confidence interval, 2 to 8 weeks) or 2 weeks (95% confidence interval, 2 to 3 weeks), respectively. In multivariable analyses, the methicillin resistance phenotype was not associated with S. aureus colonization duration (P = 0.21); the use of fluoroquinolones (hazard ratio, 3.37; 95% confidence interval, 1.31 to 8.71) and having a wound positive for a nonnasal strain (hazard ratio, 2.17; 95% confidence interval, 1.15 to 4.07) were associated with earlier loss of MSSA colonization, while no factor was associated with loss of MRSA colonization. These results suggest that the methicillin resistance phenotype does not influence the S. aureus colonization duration and that fluoroquinolones are associated with loss of MSSA colonization but not with loss of MRSA colonization.
Project description:Adult community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and methicillin-susceptible S. aureus (CA-MSSA) skin and soft tissue infection (SSTI) in China is not well described. A prospective cohort of adults with SSTI was established between January 2009 and August 2010 at 4 hospitals in Beijing. Susceptibility testing and molecular typing, including multilocus sequence typing, spa, agr typing, and toxin detection were assessed for all S. aureus isolates. Overall, 501 SSTI patients were enrolled. Cutaneous abscess (40.7%) was the most common infection, followed by impetigo (6.8%) and cellulitis (4.8%). S. aureus accounted for 32.7% (164/501) of SSTIs. Five isolates (5/164, 3.0%) were CA-MRSA. The most dominant ST in CA-MSSA was ST398 (17.6%). The prevalence of Panton-Valentine Leukocidin (pvl) gene was 41.5% (66/159) in MSSA. Female, younger patients and infections requiring incision or drainage were more commonly associated with pvl-positive S. aureus (P<0.03); sec gene was more often identified in CC5 (P<0.03); seh gene was more prevalent in CC1 (P = 0.001). Importantly, ST59 isolates showed more resistance to erythromycin, clindamycin and tetracycline, and needed more surgical intervention. In conclusion, CA-MRSA infections were rare among adult SSTI patients in Beijing. Six major MSSA clones were identified and associated with unique antimicrobial susceptibility, toxin profiles, and agr types. A high prevalence of livestock ST398 clone (17.1% of all S. aureus infections) was found with no apparent association to animal contact.
Project description:Nasal colonization by the human pathogen Staphylococcus aureus is a major risk factor for hospital- and community-acquired infections. A key factor required for nasal colonization is a cell surface-exposed zwitterionic glycopolymer, termed wall teichoic acid (WTA). However, the precise mechanisms that govern WTA-mediated nasal colonization have remained elusive. Here, we report that WTA GlcNAcylation is a pivotal requirement for WTA-dependent attachment of community-acquired methicillin-resistant S. aureus (MRSA) and emerging livestock-associated MRSA to human nasal epithelial cells, even under conditions simulating the nutrient composition and dynamic flow of nasal secretions. Depending on the S. aureus strain, WTA O-GlcNAcylation occurs in either ? or ? configuration, which have similar capacities to mediate attachment to human nasal epithelial cells, suggesting that many S. aureus strains maintain redundant pathways to ensure appropriate WTA glycosylation. Strikingly, a lack of WTA glycosylation significantly abrogated the ability of MRSA to colonize cotton rat nares in vivo. These results indicate that WTA glycosylation modulates S. aureus nasal colonization and may help to develop new strategies for eradicating S. aureus nasal colonization in the future.Nasal colonization by the major human pathogen Staphylococcus aureus is a risk factor for severe endogenous infections and contributes to the spread of this microbe in hospitals and the community. Here, we show that wall teichoic acid (WTA) O-GlcNAcylation is a key factor required for S. aureus nasal colonization. These data provide a mechanistic explanation for the capacity of WTA to modulate S. aureus nasal colonization and may stimulate research activities to establish valuable strategies to eradicate S. aureus nasal colonization in high-risk hospitalized patients and in the general community.
Project description:Nursing homes might create an environment favorable for the transmission of Staphylococcus aureus because of the presence of hospitalized elderly, overcrowding and close contacts among people. We aimed at identifying risk factors for S. aureus colonization and determining the genetic relatedness of isolates demonstrating transmission among people. We investigated 736 swab samples from 92 residents and personnel for the presence of S. aureus. Swabs from anterior nares and throat were collected quarterly (2018) in a nursing home located in Poland. Genotyping was conducted using the multi-locus variable number of tandem repeats fingerprinting (MLVF) method. We observed high seasonal variation in the proportion of participants colonized with methicillin-resistant Staphylococcus aureus (MRSA) strains (0% to 13.5%). A multivariate analysis revealed that residents aged more than 85 years old are at risk for becoming intermittent S. aureus carriers (p = 0.013). The MLVF analysis revealed a high genetic diversity among methicillin-sensitive S. aureus (MSSA) strains and close genetic relatedness between MRSA strains. We proved the advanced aged were predisposed to intermittent S. aureus carriage. Genotyping revealed the transmission of S. aureus among the participants living in a closed environment. A high genetic relatedness among isolated MRSA suggests its clonal spread in the nursing home.
Project description:OBJECTIVE:The purpose of this study is to investigate the prevalence of MRSA among people living with HIV/AIDS (PLHA) being monitored in a tertiary outpatient hospital in the state of Pernambuco, in the Brazilian Northeast. RESULTS:Staphylococcus aureus was isolated from a nasal swab and found in 31.4% of the individuals (95% CI 27.3-35.5), of whom 4.4% (95% CI 8.5-19.5) were MRSA, as confirmed by the presence of the mecA gene. For individuals whose S. aureus was recovered, the mean age was 41.5 years; 93.6% were on antiretroviral treatment. This group had CD4 cell counts?>?200 (92%) and viral load???100 copies (79.1%). Use of antimicrobial agents in the past 12 months was found among 21% of the individuals, and 24.2% reported use of illicit drugs at lease once in their lifetime. Prevalence of nasal colonization by MSSA (26.7%) and MRSA (4.4%) was higher in comparison to other studies of this population; nevertheless, we were unable to establish factors associated with risk.
Project description:Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as an important cause of skin and soft-tissue infections (SSTI). The understanding of the molecular epidemiology and virulence of MRSA continues to expand. From January 2005 to December 2005, we screened soldiers for MRSA nasal colonization, administered a demographic questionnaire, and monitored them prospectively for SSTI. All MRSA isolates underwent molecular analysis, which included pulsed-filed gel electrophoresis (PFGE) and PCR for Panton-Valentine leukocidin (PVL), the arginine catabolic mobile element (ACME), and the staphylococcal cassette chromosome mec (SCCmec). Of the 3,447 soldiers screened, 134 (3.9%) had MRSA colonization. Of the 3,066 (89%) who completed the study, 39 developed culture-confirmed MRSA abscesses. Clone USA300 represented 53% of colonizing isolates but was responsible for 97% of the abscesses (P < 0.001). Unlike colonizing isolates, isolates positive for USA300, PVL, ACME, and type IV SCCmec were significantly associated with MRSA abscess isolates. As determined by multivariate analysis, risk factors for MRSA colonization were a history of SSTI and a history of hospitalization. Although various MRSA strains may colonize soldiers, USA300 is the most virulent when evaluated prospectively, and PVL, ACME, and type IV SCCmec are associated with these abscesses.