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Methicillin-resistant Staphylococcus aureus (MRSA) is rampant in the nation’s nursing homes, and 4% of MRSA isolates in long-term care facilities (LTCF) are the emerging community associated strains (CA-MRSA), an epidemiologist reports.

Healthcare Infection Prevention: CA-MRSA gets a foot in the nursing home door

Healthcare Infection Prevention

CA-MRSA gets a foot in the nursing home door

Coming in from community or hospitals?

Methicillin-resistant Staphylococcus aureus (MRSA) is rampant in the nation’s nursing homes, and 4% of MRSA isolates in long-term care facilities (LTCF) are the emerging community associated strains (CA-MRSA), an epidemiologist reports.

"[CA-MRSA] is there, but we don’t have a whole lot of demographics or background data on these patients," says Susan Beekman, RN, nurse epidemiologist at the University of Iowa in Iowa City. "The little data that we do have suggest that some of these patients may have come from the community. I think CA-MRSA is certainly present in nursing homes, but the data that we have suggest that it is still at a very low level."

Could it become endemic?

Still, the findings raise the question of whether CA-MRSA could become endemic in nursing homes. "I think it could," she adds. "There is some evidence that suggest that certain strains of MRSA that appear to be community associated may have better fitness’ than some of the traditional [nosocomial] MRSA. I suspect it could become more common."

Beekman recently presented the findings in Washington, DC, at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). "There was a lot of evidence presented at ICAAC that suggest that these co-called community-acquired strains really are becoming endemic in certain areas," she says.

With reports of nosocomial outbreaks due to CA-MRSA becoming more common, it appears hospitals will be more vulnerable if nursing homes become reservoirs for the pathogen. The situation reinvigorates the old debate between hospitals and nursing homes of "who gave MRSA to whom." Beekman is suspicious that some of the CA-MRSA in nursing homes came from area hospitals rather than straight out of the community. Indeed, some researchers at ICAAC reported that CA-MRSA isolates are becoming the predominant strains associated with nosocomial MRSA infections in their hospitals.

"Although community associated MRSA is still pretty uncommon, there are some hospitals where it is far more common," she says. "I suspect we may [find] community-associated MRSA that may actually be [coming from] hospitals."

Why it matters

One may ask why all this matters since there is no shortage of MRSA of all stripes in hospitals and nursing homes. However, the community strains have different antibiograms than their nosocomial cousins, potentially confounding empiric treatment. The CA-MRSA strains have also shown some nasty hints of heightened virulence, including reported cases of necrotizing fasciitis.

"We don’t have any outcome data on these patients," Beekman says. "The data that we have suggest that it is quite uncommon for patients to be cultured at more invasive sites at nursing homes. Generally, if [clinicians] are going to draw blood cultures or get more invasive respiratory specimens they are done in the hospital. Most of the culturing that is done in nursing homes is from urine and swabs of skin and soft tissue because those are cultures that are easier to obtain."

Trends over time

In the study, Beekman and colleagues assessed trends over time in antimicrobial resistance in MRSA and vancomycin-resistant enterococci (VRE) recovered from LTCF residents across the United States.1 Bacterial isolates recovered from LTCF residents were sent to a central lab for susceptibility testing during three one-year periods from 1999 through 2004.

The number of participating LTCFs ranged from 97 to 175 over the three study periods. A total of 1,060 S. aureus isolates (325 skin/soft tissue, 489 urine, 246 other specimens) and 1,979 enterococcal isolates (81 skin/soft tissue, 1,835 urine, 63 other specimens) were submitted over the three study periods.

The proportion of MRSA causing staph infections was 67% over the course of the study. That means MRSA rates in LTCFs are extraordinarily high when compared with those documented from national surveys of acute care hospitals, Beekman concluded.

"I think it is pretty clear that the MRSA rates in long-term care facilities are higher than has been reported on a routine basis from almost any hospital in the country," she says. "If you admit a patient to a hospital from a nursing home, I think you need to assume unless you prove [otherwise] that they are least colonized with MRSA."

VRE rate much lower

In contrast to that striking level, the overall VRE rate was 5.1% in the study. Rates of resistance did not vary consistently over time by specimen type for either organism, although no VRE was detected in any skin/soft-tissue isolate. Five MRSA isolates (0.7%) had no co-resistances, while 22 (3.1%) had one co-resistance (all to ciprofloxacin) and were clindamycin-susceptible. Linezolid resistance was rare with enterococci (eight intermediate, two resistant) and absent in staph isolates, the researchers reported.

Residents like neonates

Though antibiotic resistance typically increases in the face of high levels of drug utilization, the answer to the problem is not as easy as simply cutting back prescriptions.

"It’s my personal opinion that the more effort that could be focused on limiting antimicrobial use in long-term care would be a wise thing to do," Beekman says. "The problem is that diagnosing infections in these patients is often very difficult. They are kind of like neonates in some ways. Some elderly patients are known not to mount fevers for serious infections. The signs and symptoms of infection in this population are different, so the use of antibiotics tends to be quite widespread and tends to be completely empiric. It is fairly uncommon for cultures even to be done."

Reference

  1. Beekman SE, Rice C, Heilmann KP, et al. MRSA and VRE Rates in long-term care facilities: Results of a multicenter longitudinal surveillance study. Abstract K-1755. Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC). Washington, DC; Dec. 16-19, 2005.