Community Associated MRSA On The Rise In Chicago

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Main Category: MRSA / Drug Resistance
Also Included In: Infectious Diseases / Bacteria / Viruses;  Public Health
Article Date: 30 May 2007 - 0:00 PDT

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Cases of antibiotic resistant staph infections acquired in the community as opposed to hospitals, more accurately known as community associated methicillin resistant Staphylococcus aureus (CA-MRSA), have risen sharply among Chicago's urban poor and prison populations.

These are the findings of a study published in the Archives of Internal Medicine.

The researchers found that the incidence of MRSA in Chicago's Cook County Hospital system among patients who acquired the infection in the community as opposed to a healthcare setting went up seven-fold between 2000 and 2005.

MRSA is an antibiotic resistant staph infection more typically associated with hospitals and other healthcare settings. However, in 1998, a form of MRSA began to emerge that was acquired in community settings all over the world, said the authors in the background section of their article. The risk factors for CA-MRSA typically include being or having been in jail, playing certain sports, using drugs intravenously, overcrowded housing, poor hygiene, and tattooing.

In this particular study the authors investigated what may lie behind the apparent rise in cases of CA-MRSA at Chicago's Cook County Hospital system so that prevention programmes can be developed.

Dr Bala Hota and colleagues at Rush University Medical Center and John H. Stroger Jr. Hospital of Cook County, Chicago looked at tissue, abscess fluid, joint fluid, and bone cultures from patients at the 464-bed public hospital and its associated clinics who were seen between 2000 and 2005 and acquired MRSA in the community and not a hospital.

They found 518 cases of community onset MRSA that occurred between 2001 and 2004, and compared them to 704 controls who had community associated methicillin susceptible Staphylococcus aureus (CA-MSSA), which unlike MRSA does respond to antibiotics like methicillin. They estimated rates of infection and geographic and other risks.

The results showed that:

• Incidence of CA-MRSA skin and soft tissue infections between 2000 and 2005 went up nearly seven-fold.
• The increase was 24 cases per 100,000 people in 2000 to 164.2 cases per 100,000 people in 2005.
• The number of cases of antibiotic susceptible infections remained stable over the same period.
• This indicates that MRSA occurred in addition to, and not in place of, MSSA.
• The risk factors for CA-MRSA were incarceration, African-American race/ethnicity and residence at a group of geographically proximate public housing complexes.
• Older age was inversely related to CA-MRSA risk.

Hota and colleagues concluded that:

"Clonal CA-MRSA infection has emerged among Chicago's urban poor. It has occurred in addition to, not in place of, methicillin-susceptible S aureus infection. Epidemiological analysis suggests that control measures could focus initially on core groups that have contributed disproportionately to risk, although CA-MRSA becomes endemic as it disseminates within communities."

"Why CA-MRSA has emerged at such a rapid rate remains unclear," they added.

Hospitals and other facilities where people with and without infection are housed at the same location for long periods have long been regarded as "epicenters" for antimicrobial resistance. This study suggests that public housing, prisons and other community settings may also give the bacteria similar opportunities to develop antibiotic resistance because a sufficiently high number of at risk people are close together for long periods of time.

"Community-Associated Methicillin-Resistant Staphylococcus aureus Skin and Soft Tissue Infections at a Public Hospital: Do Public Housing and Incarceration Amplify Transmission?"
Bala Hota, Charlotte Ellenbogen, Mary K Hayden, Alla Aroutcheva, Thomas W Rice, and Robert A Weinstein.
Arch Intern Med. 2007;167:1026-1033.
Vol. 167 No. 10, May 28, 2007

Click here for Abstract.

Click here for Community-Associated MRSA Information for the Public (from the US Centers for Disease Control and Prevention, CDC).

Written by: Catharine Paddock
Writer: Medical News Today
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today