Healthcare Infection Prevention-Will community MRSA emerge as threat in day-care centers?

Canadian case raises questions, but CDC not calling for additional measures

A recent report of apparent transmission of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) in a Canadian day care center raises concerns that the traditional nosocomial pathogen may pose an increasing threat in such settings if it continues to emerge beyond the hospital.

A 2-year-old boy with chronic dermatitis likely acquired MRSA in a day-care center after exposure to another child with a suspected community-acquired strain of MRSA, investigators in Toronto, Ontario, report.¹ The authors theorized that the 2-year-old contact case was exposed to a 2½-year-old index case, who was diagnosed with community-acquired MRSA ear infection. In addition, the 7-year-old sibling of the 2-year-old contact case was culture-positive for MRSA. All three children had a matching strain but were subsequently decolonized or cleared of infection. (See case summary, p. 2.)

As a result of the case, the authors recommend excluding children with chronic dermatitis from day care. In addition, when a child is identified with MRSA in a child care center, at a minimum, parents ought to be informed of its presence, the authors concluded. In the event that another child becomes ill, a physician can obtain appropriate cultures earlier than usual, avoiding protracted use of ineffective antibiotics, they noted. Beyond that, the case also raises concerns about the limited options to control transmission in day-care settings should MRSA emerge in the community.

"Now that we have seen it in the community and in children, you have to ask yourself, where it is likely to be a problem?" says Allison McGeer, MD, director of infection control at Mount Sinai and Princess Margaret Hospitals in Toronto and one of the authors of the study.

"The answer, of course, is day-care centers. It doesn't take a Nobel laureate to be able to say that. Kids spend a lot of time in day care. I don't know that there is very much preventive you can do at the moment, but it makes me very nervous about the possibility of MRSA being in day care centers."

CDC: No special MRSA measures needed

Indeed, the investigation comes on the heels of reports of emerging community-acquired MRSA strains in the Upper Midwest of the United States.² (See Hospital Infection Control, October 1999, pp. 125-133.) In the U.S. cases, investigators concluded that rather than moving out from the hospital, the community strains of MRSA are likely linked to prescribing trends among pediatric outpatients. The Centers for Disease Control and Prevention has not currently made any new day-care recommendations — such as alerting parents of possible cases in classrooms — based on the U.S. cases. Rather, the CDC is re-emphasizing existing guidelines for frequent hand washing, basic infection control measures, and standard exclusion policies.³

"We are not recommending that anything special be done for kids in day care [for MRSA]," says Timothy Naimi, MD, CDC epidemic intelligence service officer at the Minnesota Department of Health and the principal investigator in the U.S. MRSA cases. "We don't have any reason to suspect yet that these strains are any more virulent than regular staph strains that are carried by a quarter or a fifth of healthy children. And even though [the U.S. community MRSA strains] are resistant to all the beta-lactams and cephalospor ins, should someone get an infection, they are still eminently treatable with other outpatient antibiotics."

In addition, the CDC is wary of giving any encouragement to physicians to treat MRSA colonization overly aggressively with antibiotics because that could exacerbate growing problems with drug resistance. However, Naimi, who was familiar with the Canadian report, adds that the current policy is still subject to review and change.

"This situation is not set in stone," he adds. "We want to pull together a working group in the future to discuss these issues. But basically, in day-care settings, kids are going to pass around their flora to each other. Of course, we encourage proper hygiene in day care, but realistically we know that is not too easy."

But the MRSA mindset is somewhat different in Canada, where some hospital clinicians have generally taken a more aggressive approach (i.e., patient screening) to try to stave off the kind of MRSA endemicity that has become commonplace in some U.S. hospitals. (See HIC, August 1999, pp. 109-110.) The day care investigators, while noting that, concluded "we are less optimistic about the control of this organism in the child care setting than we had been before this study. There is not the same control in the real world of child care, despite extraordinary [cooperation] of a highly interested and competent staff."

Of the 164 children in the entire day-care center, the rate of MRSA recovery (including the index case) was 1.2% (2/164). The classroom attack rate was 17% (2/12). None of 38 staff members screened were colonized. In addition, the Canadian authors cited a previous report of MRSA in two U.S. child care settings where prevalence of colonization was 24% and 3%.⁴

"We had no idea how much spread we were going to see," McGeer says. "Most people who are colonized with MRSA don't shed a lot, and you don't get much trouble with them. Then, every once in a while, you get somebody that everyone who comes into contact with gets colonized. It's unpredictable. We were certainly braced for larger numbers, and I think most of us suspected that we were going to get larger numbers."

Index case could have been a secondary case

The direction of the transmission in the center is ultimately unclear, the authors noted. The source of the MRSA in the classmate with dermatitis also could have been any one of a variety of his ambulatory care providers, his sister, or the index case. "Dermatitis in the classroom contact actually preceded the acute ear disease in the index case by about three months, raising the possibility that the index case was actually a secondary case," the authors noted.

Likewise, the index case had bilateral ear tubes placed in the hospital approximately six months earlier, and the authors conceded that contact at that time with colonized personnel or the health care environment could certainly have exposed him to MRSA. However, the MRSA strain appeared to be community-acquired because it was not one of those circulating in health care institutions in Toronto, the authors added. In Canadian surveillance at sentinel hospitals, 68% of MRSA is one of four distinct strains, McGeer notes.

"In our screening programs for MRSA in Canada, we see occasional people who appear to be community-acquired," McGeer says. "In general, those people do not have multiresistant strains of Staph aureus. They are more likely to have simple methicillin resistance. They are usually susceptible to other antibiotics."

It is not known whether the MRSA strain was the same as those seen in the community strains found in the United States. In general, however, the strains have a similar resistance/susceptibility pattern in terms of resistance to beta-lactams and susceptibility to such drugs as tetracycline, vancomycin, and gentamicin. In that regard, the authors recommended informing parents after a case appears in day care so physicians can administer effective antibiotics should another case appear, McGeer notes.

"If you don't know somebody has it, then the odds are good that you will use the wrong drug for empiric therapy of skin and soft-tissue infection," McGeer says. "Most kids in day care are healthy, and they are not likely to get into trouble, but people should be aware. Because normally if you get a skin or soft-tissue infection, your doctor won't culture it. They will just put you on antibiotics. And you don't want people getting worse after six days of antibiotics, coming back, and then you culture them."

References

1. Shahin R, Johnson IL, Jamieson F, et al. Methicillin-resistant Staphylococcus aureus carriage in a child care center following a case of disease. Arch Pediatr Adolesc Med 1999; 153:864-868.

2. Centers for Disease Control and Prevention. Four pediatric deaths from community-acquired methicillin-resistant Staphylococcus aureus — Minnesota and North Dakota, 1997-1999. MMWR 1999; 48:707-710.

3. Centers for Disease Control and Prevention. The ABCs of Safe and Healthy Child Care: A Handbook for Child Care Providers. Atlanta; 1996.

4. Adcock PM, Pastor P, Medley F, et al. Methicillin-resistant Staphylococcus aureus in two child care centers. J Infect Dis 1998; 178:577-580.