Methicillin-resistant Staphylococcus aureus (MRSA) carriage in a dermatology unit.

OBJECTIVE: The aim of this study was to characterize Staphylococcus aureus (MRSA) carriage in a dermatology unit. METHODS: This was a prospective and descriptive study. Over the course of 26 weeks, surveillance cultures were collected weekly from the anterior nares and skin of all patients hospitalized in a 20-bed dermatology unit of a tertiary-care hospital. Samples from healthcare workers (HCWS) were cultured at the beginning and end of the study. Colonized patients were put under contact precautions, and basic infection control measures were enforced. Staphylococcus aureus colonization pressure was determined monthly. Colonized and non-colonized patients were compared, and isolates were evaluated for antimicrobial susceptibility, SCCmec type, virulence factors, and type. RESULTS: Of the 142 patients evaluated, 64 (45%) were colonized by MRSA (39% hospital acquired; 25% community acquired; 36% indeterminate). Despite isolation precautions, hospital-acquired Staphylococcus aureus occurred in addition to the continuous entry of Staphylococcus aureus from the community. Colonization pressure increased from 13% to 59%, and pemphigus and other bullous diseases were associated with MRSA colonization. Eleven out of 71 HCWs (15%) were Staphylococcus aureus carriers, although only one worker carried a persistent clone. Of the hospital-acquired MRSA cases, 14/28 (50%) were SCCmec type IV (3 PFGE types), 13 were SCCmec type III (46%), and one had an indeterminate type. These types were also present among the community-acquired Staphylococcus aureus isolates. SSCmec type IV isolates were shown to be more susceptible than type III isolates. There were two cases of bloodstream infection, and the pvl and tst virulence genes were absent from all isolates. CONCLUSIONS: Dermatology patients were colonized by community- and hospital-acquired Staphylococcus aureus. Half of the nosocomial Staphylococcus aureus isolates were SCCmec type IV. Despite the identification of colonized patients and the subsequent contact precautions and room placement, Staphylococcus aureus colonization continued to occur, and colonization pressure increased. Pemphigus and other bullous diseases were associated with Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) carriage in a dermatology unit

OBJECTIVE: The aim of this study was to characterize Staphylococcus aureus (MRSA) carriage in a dermatology unit. METHODS: This was a prospective and descriptive study. Over the course of 26 weeks, surveillance cultures were collected weekly from the anterior nares and skin of all patients hospitalized in a 20-bed dermatology unit of a tertiary-care hospital. Samples from healthcare workers (HCWS) were cultured at the beginning and end of the study. Colonized patients were put under contact precautions, and basic infection control measures were enforced. Staphylococcus aureus colonization pressure was determined monthly. Colonized and non-colonized patients were compared, and isolates were evaluated for antimicrobial susceptibility, SCCmec type, virulence factors, and type. RESULTS: Of the 142 patients evaluated, 64 (45 percent) were colonized by MRSA (39 percent hospital acquired; 25 percent community acquired; 36 percent indeterminate). Despite isolation precautions, hospital-acquired Staphylococcus aureus occurred in addition to the continuous entry of Staphylococcus aureus from the community. Colonization pressure increased from 13 percent to 59 percent, and pemphigus and other bullous diseases were associated with MRSA colonization. Eleven out of 71 HCWs (15 percent) were Staphylococcus aureus carriers, although only one worker carried a persistent clone. Of the hospital-acquired MRSA cases, 14/28 (50 percent) were SCCmec type IV (3 PFGE types), 13 were SCCmec type III (46 percent), and one had an indeterminate type. These types were also present among the community-acquired Staphylococcus aureus isolates. SSCmec type IV isolates were shown to be more susceptible than type III isolates. There were two cases of bloodstream infection, and the pvl and tst virulence genes were absent from all isolates. CONCLUSIONS: Dermatology patients were colonized by community- and hospital-acquired Staphylococcus aureus. Half of the nosocomial Staphylococcus aureus isolates were SCCmec type IV. Despite the identification of colonized patients and the subsequent contact precautions and room placement, Staphylococcus aureus colonization continued to occur, and colonization pressure increased. Pemphigus and other bullous diseases were associated with Staphylococcus aureus.

Differences between "classical" risk factors for infections caused by methicillin-resistant Staphylococcus aureus (MRSA) and risk factors for nosocomial bloodstream infections caused by multiple clones of the staphylococcal cassette chromosome mec type IV MRSA strain.

OBJECTIVE: To identify risk factors associated with nosocomial bloodstream infections caused by multiple clones of the staphylococcal cassette chromosome mec (SCCmec) type IV strain of methicillin-resistant Staphylococcus aureus (MRSA). DESIGN: An unmatched case-control study (at a ratio of 1:2) performed during the period from October 2002 through September 2003. SETTING: A 2,000-bed tertiary care teaching hospital affiliated with the University of São Paulo in São Paulo, Brazil. METHODS: Case patients (n=30) were defined either as patients who had a bloodstream infection due to SCCmec type IV MRSA diagnosed at least 48 hours after hospital admission or as neonates with the infection who were born in the hospital. Control patients (n=60) were defined as patients with SCCmec type III MRSA infection diagnosed at least 48 hours after hospital admission. Genes encoding virulence factors were studied in the isolates recovered from case patients, and molecular typing of the SCCmec type IV MRSA isolates was also done by pulsed-field gel electrophoresis and multilocus sequence typing. RESULTS: In multivariate analysis, the following 3 variables were significantly associated with having a nosocomial bloodstream infection caused by SCCmec type IV strains of MRSA: an age of less than 1 year, less frequent use of a central venous catheter (odds ratio [OR], 0.07 [95% confidence interval {CI}, 0.02-0.28]; p= .025), and female sex. A second analysis was performed that excluded the case and control patients from the neonatal unit, and, in multivariate analysis, the following variables were significantly associated with having a nosocomial bloodstream infection caused by SCCmec type IV strains of MRSA: less frequent use of a central venous catheter (OR, 0.12 [95% CI, 0.03-0.55]; p= .007), lower Acute Physiology and Chronic Health Evaluation II score on admission (OR, 0.14 [95% CI, 0.03-0.61]; p= .009), less frequent surgery (OR, 0.21 [95% CI, 0.06-0.83]; p= .025), and female sex (OR, 5.70 [95% CI, 1.32-24.66]; p= .020). Of the 29 SCCmec type IV MRSA isolates recovered from case patients, none contained the Panton-Valentine leukocidin, gamma-hemolysin, enterotoxin B or C, or toxic shock syndrome toxin-1. All of the isolates contained genes for the LukE-LukD leukocidin and alpha-hemolysin. Genes for enterotoxin A were present in 1 isolate, and genes for beta-hemolysin were present in 3 isolates. CONCLUSIONS: "Classical" risk factors do not apply to patients infected with the SCCmec type IV strain of MRSA, which is an important cause of nosocomial bacteremia. This strain infects a patient population that is less ill and has had less frequent invasive procedures than a patient population infected with the multidrug-resistant strain of SCCmec type III MRSA. We found that virulence factors were rare and that Panton-Valentine leukocidin was absent. There were multiple clones of the SCCmec type IV strain in our hospital. Children under 1 year of age were at a higher risk. There was a predominant clone (sequence type 5) in this patient population.

Prevalence of SCCmec type IV in nosocomial bloodstream isolates of methicillin-resistant Staphylococcus aureus.

Over a period of 7 months, 151 consecutive methicillin-resistant Staphylococcus aureus blood isolates were evaluated. None was community acquired. Twenty (13%) were susceptible to four or more antimicrobials, and 95% of these isolates were identified as SCCmec type IV. Molecular typing demonstrated four patterns, with one predominant pattern. Although usually community acquired, SCCmec type IV in our setting is clearly nosocomial.