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Community-Associated Methicillin-Resistant Staphylococcus aureus Infections in Pacific Islanders --- Hawaii, 2001--2003
Methicillin-resistant Staphylococcus aureus (MRSA) is emerging as a cause of skin and soft-tissue infections in persons who have little or no contact with health-care settings. The majority of these infections are mild, involving skin and soft tissue; however, certain cases can progress to invasive tissue infections, bacteremia, and death (1). Transmission of MRSA has been reported most frequently in certain populations (e.g., children, sports participants, or jail inmates) (2,3). Persons in the American Indian or Alaska Native population in the United States and aboriginals and Pacific Islanders (PIs) in Australia have high rates of MRSA colonization and infection (4,5). In 2003, clinicians reported an increased number of skin abscesses caused by MRSA among patients examined in ambulatory care settings. This report summarizes the findings of a retrospective study of community-associated MRSA (CA-MRSA) infections in Hawaii that identified a higher proportion of cases among PIs than were identified among Asians, compared with their respective proportions in the Hawaii population. Efforts to prevent CA-MRSA in Hawaii should focus on identifying factors causing the disproportionate number of infections among PIs.
Four health-care facilities in Hawaii were selected for the study: a pediatric and women's center, a private urban clinic, a county urban hospital, and a rural community hospital. Patients with MRSA isolated during the study period were identified, and chart abstraction was performed for those patients who had illness consistent with the CA-MRSA case definition*. Chart information on race was self-reported. Race categories included white, black, Asian, multiracial non-PI, and PI (i.e., Native Hawaiians and persons of Polynesian, Micronesian, and Melanesian ancestry). The category PI also was used for persons who were PI in addition to another race. Data from the 2001 Hawaii Health Survey, Hawaii State Department of Health (6), and 2002 hospital data from the pediatric and women's center were used for population comparisons.
During July 2001--June 2003, MRSA was recovered from 1,389 patients in the four study facilities, of whom 389 (28%) had illness consistent with the case definition for CA-MRSA infection; 346 (89%) of these patients had racial/ethnic data recorded on their charts. PIs accounted for 51% (178 of 346) of the CA-MRSA patients, compared with 24% (278,607 of 1,175,595) of the total population of Hawaii in 2001 (p<0.01) (6). In the pediatric and women's center alone, PIs accounted for 76% (90 of 118) of CA-MRSA patients, compared with 35% (17,088 of 48,912) of the patients served in this facility in 2002 (p<0.01). In contrast, Asians accounted for 16% (54 of 346) of all patients with CA-MRSA, compared with 32% (374,776 of 1,175,595) of the 2001 Hawaii population (p<0.01). In the pediatric and women's center alone, Asians constituted 10% (12 of 118) of CA-MRSA patients, compared with 36% (17,648 of 48,912) of the patients examined in 2002 (p<0.01). Among all CA-MRSA patients, 211 (61%) were male; median age was 18.5 years (range: 0--87 years) for PIs and 32 years (range: 0--93 years) for other races (p<0.01). Of 321 patients who received antimicrobial therapy, 215 (67%) were treated with an antimicrobial agent to which S. aureus was resistant. Adult PIs (i.e., aged >19 years) had diabetes mellitus more often than adults of other races (27% versus 12%; p<0.05) and reported intravenous drug use less often (1% versus 8%; p<0.05).
Among patients with CA-MRSA, adult PIs had skin and soft tissue infections more often than adults of other races (98% [87 of 89] versus 85% [119 of 140]; p<0.05). The majority of skin infections in PIs consisted of abscesses (71% [126 of 178]) and/or cellulitis (41% [73 of 178]). Other skin infections were wounds/ulcers (six), impetigo (four), and folliculitis (three). Of the PIs with skin infections, 11 had concurrent illnesses (e.g., deep soft-tissue infections, bacteremia, bursitis, osteomyelitis, and pneumonia). Among the 28 patients who did not have skin infections, pneumonia was the most frequent presentation (five PIs and seven others).
Despite differences in clinical presentation, the proportion of patients hospitalized and the types of therapies received were similar for PIs and patients of other races when stratified by age group. The majority of patients received antimicrobials to treat MRSA infection (98% [174 of 177] among PIs and 96% [156 of 163] among other races). Among adults, surgery, mostly incision and drainage of abscesses, was performed on 62% (54 of 87) of PIs and 57% (73 of 129) of patients of other races. Among persons aged <19 years, surgery was performed on 64% (56 of 88) of PIs and 72% (18 of 25) of patients of other races.
Reported by: M Melish, MD, R Arpon, P Coon, M Kim, MSPH, S Slavish, MPH, participating Hawaii health-care facilities; P Effler, MD, J Chang, Hawaii State Dept of Health. Div of Healthcare Quality Promotion, National Center for Infectious Diseases; CF Estivariz, MD, SY Park, MD, EIS officers, CDC.
In 2000, PIs, alone or in combination with other races, made up only 0.3% (874,000) of the total U.S. population. However, in Hawaii, the state with the largest PI population, 23% of the population was PI in 2001 and 32% was Asian (6). Historically, PIs have been grouped with persons of Asian origin for demographic purposes; however, these two populations might differ in health status and risk factors for infectious and noninfectious diseases. This report documents that the number of CA-MRSA infections in Hawaii is disproportionately greater among PIs than among Asians. Clinical presentation as skin and soft-tissue infection also was more frequent among PIs than among patients of other races.
Several factors might contribute to higher rates of CA-MRSA among PIs. In Australia, Hawaii, and New Zealand, PIs have higher reported rates of infections by S. aureus, group A streptococcus, and Neisseria meningitidis than persons of other races (5,7). Geographic isolation might have facilitated transmission of genetic traits conferring differences in immune function; however, little has been reported on specific immunologic differences among PIs (5,7). Alternatively, environmental factors such as home overcrowding, inadequate access to appropriate sanitation, and limited access to health care also might contribute to a higher rate of bacterial infections, especially skin infections (2,3,7). Because of the limited information recorded in medical charts, presence of these risk factors could not be assessed in this study. However, in the 1990 Census, persons who self-identified as PIs had larger families, a lower proportion of college graduates, and higher poverty rates, compared with persons who self-identified as Asian/PIs and the overall national average (8). Cultural and language barriers, limited access to health care, and lack of prevention and education programs also are known to contribute to poorer health among PIs (9).
In this study, investigators also observed a higher proportion of diabetes mellitus among PIs with CA-MRSA infections. Persons with diabetes and obesity are at risk for skin and soft-tissue infections, which can require multiple and/or prolonged courses of antibiotics, making them more susceptible to infections with antimicrobial-resistant strains (10).
The findings in this report are subject to at least one limitation. The PIs identified as CA-MRSA patients from the four facilities in this study might not be representative of the total PI population in Hawaii in terms of health-risk factors. This might have widened the disparity between the percentage of CA-MRSA cases accounted for by PIs and the percentage of PIs in the general state population. However, PI patients at the pediatric women's center also were compared with the center's patient census. This comparison revealed similar disproportionate prevalence of CA-MRSA infections in PIs, compared with Asians and the total patient census.
Prospective studies are needed to identify specific risk factors for, and targeting measures to prevent, MRSA acquisition and transmission among PIs. General strategies to prevent and control CA-MRSA infections include 1) encouraging clinicians to culture suspect lesions and provide targeted antimicrobial and surgical therapy, 2) maintaining appropriate infection-control precautions during wound care of patients with skin infections at outpatient health-care facilities, and 3) providing patients and families with simple instructions to prevent transmission of skin infections to family members and other contacts, such as education on appropriate wound management, hand and body hygiene, and limiting sharing of potentially contaminated items. Additional information about CA-MRSA is available at http://www.cdc.gov/ncidod/hip/aresist/mrsa_comm_faq.htm.
* A case of CA-MRSA was defined as illness compatible with staphylococcal disease, in which MRSA was cultured from the site of infection during July 2001--June 2003 in an outpatient setting or <48 hours after hospital admission, and with none of the following health-care risk factors: hospitalization, surgery, dialysis, or residence in a long-term--care facility <1 year before the onset of illness; permanent indwelling catheter or percutaneous medical device; or a previous positive MRSA culture.
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