Prospective comparison of methicillin-susceptible and methicillin-resistant community-associated Staphylococcus aureus infections in hospitalized patients.
BACKGROUND
We sought to determine the proportion of community-associated Staphylococcus aureus infections due to methicillin-resistant S. aureus (CA-MRSA) at a large county hospital. In addition, we sought to identify the demographic and clinical risk factors associated with CA-MRSA infection.


METHODS
Patients were prospectively enrolled if they were admitted to Parkland Hospital and had a positive culture for S. aureus isolated within 72 h of admission. The patients were interviewed using a standardized data questionnaire. Data collected included patient demographics, clinical history, as well as health care and non-health care associated MRSA risk factors. Bacterial susceptibilities were verified through review of microbiology laboratory and pharmacy records. Isolates were tested for Panton-Valentine leukocidin (PVL) gene, SCCmec type, and for inducible clindamycin resistance.


RESULTS
One hundred and ninety-eight patients were interviewed prospectively, of which eight had colonization without active infection. One hundred and nineteen patients were infected with MRSA and 71 patients were infected with methicillin-susceptible S. aureus (MSSA). Patients with MRSA were more likely to be African-American and unemployed. Patients with MRSA most commonly presented with a skin or soft tissue infection (SSTI): 69% versus 45%, p=0.0012, while patients with MSSA were more likely to have infection of the respiratory tract: 11% versus 3%, p=0.02. Patients with MRSA were more likely to have used antibiotics in the past six months, been homeless, have a history of incarceration, have abused alcohol and have a history of infection with MRSA. In multivariate analysis, African-American race, antibiotics in the past six months, and a history of being homeless were associated with MRSA infection. Only 11 of 119 (9%) MRSA patients did not have at least one of these risk factors. PVL gene was present in 72 of 74 (97%) MRSA isolates and SCCmec type IV was present in 63 of 75 (84%) MRSA isolates.


CONCLUSIONS
The majority of patients hospitalized with community-associated S. aureus infections were due to MRSA, most of which involved an SSTI. African-American race, recent antibiotics and past homeless status predicted infection with MRSA; however, no clinical profile could reliably exclude MRSA. Clinicians should be aware of the increasing prevalence of CA-MRSA.
Skiest
Daniel J
DJ
The University of Texas Southwestern Medical Center, Dallas, TX, USA. daniel.skiest@bhs.org
Brown
Katia
K
Cooper
Travis W
TW
Hoffman-Roberts
Holly
H
Mussa
Huda R
HR
Elliott
Alan C
AC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001427:Bacterial Toxins / Q000235:genetics; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology; D005098:Exotoxins / Q000235:genetics; D005260:Female; D006760:Hospitalization; D006766:Hospitals, County; D006801:Humans; D007956:Leukocidins / Q000235:genetics; D008297:Male; D008712:Methicillin / Q000494:pharmacology*; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000382:microbiology; D012307:Risk Factors; D018461:Soft Tissue Infections / Q000453:epidemiology / Q000382:microbiology; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology; D013207:Staphylococcal Skin Infections / Q000453:epidemiology / Q000382:microbiology; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D011795:Surveys and Questionnaires; D013781:Texas
D000900:Anti-Bacterial Agents; D001427:Bacterial Toxins; D005098:Exotoxins; D007956:Leukocidins; C078284:Panton-Valentine leukocidin; D008712:Methicillin