MRSA continues to emerge in communities
May 1, 2000 6 minutes read
MRSA continues to emerge in communities
14 more pediatric infections without risk factors
Methicillin-resistant Staphylococcus aureus (MRSA) continues to emerge as a community-acquired infection in children without traditional risk factors, raising critical questions about antibiotic selection for empiric therapy. Fourteen cases — including four children who required surgical treatment — occurred in Corpus Christi, TX, over a three-year period from 1997 to 1999, reports Jaime Fergie, MD, hospital epidemiologist at Driscoll Children’s Hospital in the south Texas city.
The children were identified in reviewing records and case findings of 34 hospitalized MRSA patients over the period. (See cases, p. 65.) The 14 patients had no identified risk factors for MRSA (recent hospitalization, residence in a long-term-care facility or underlying chronic illnesses). In addition, the annual rate of MRSA at the pediatric hospital increased from a range of 2.9% to 6.7% per year of all S. aureus isolates for 1990-96 to a range of 8.3% to 11.4% for the three-year period from 1997-1999.
"Children are coming into the hospital with MRSA," Fergie tells Hospital Infection Control. "These are basically previously healthy children. We looked for risk factors. There were no risk factors."
The findings were presented at the Centers for Disease Control and Prevention’s 4th Decennial International Conference on Nosocomial and Healthcare-Associated Infections, held in Atlanta in March.1 The cases follow CDC reports last year of four fatal community-acquired infections that occurred in the Upper Midwest in otherwise healthy children with no traditional risk factors for MRSA.2 (See HIC, October 1999, pp. 125-133.) The general consensus is that the new community strains of MRSA are not nosocomial in origin, but are spreading in communities after genetically acquiring resistance due to increasing antibiotic use among pediatric outpatients.
"The use of antibiotics in children, in pediatrics in general, is staggering," Fergie says. "For the common otitis media or upper respiratory infection, [some] children get six to seven courses of antibiotics in a year. Many are overtreated with antibiotics."
A forced change
The cases have major implications for empiric therapy, as clinicians may prescribe an ineffective antibiotic unless they suspect MRSA in the community. "It is important, because in pediatrics, we have not been thinking of treating these children with different antibiotics," he says. "We are accustomed to using the cephalosporins . . . and we are accustomed to seeing improvement. This is going to force us to change the way we treat these children empirically."
Appropriate antibiotic therapy with vancomycin, trimethoprim/sulfamethoxazole, clindamycin, erythromycin, tetracycline, or ciprofloxacin was administered to seven of the 14 children with community-acquired MRSA. The other children recovered despite receiving inadequate antimicrobial therapy, but four of those seven required surgical treatment involving incision and drainage. Indeed, as with the previously reported cases, some of the infections in Texas became perilous due to ineffective antibiotic therapy.
"The worse case we had was a child that came in with severe pneumonia, went to the intensive care unit, and was treated with cephalosporin," Fergie says. "It was not until we did thoracentesis — the patient actually required thoracoscopic debridement — that we found out that it was MRSA. After many days of therapy with cephalosporin, the organism was [still] there, and the patient was not recovering. We switched to vancomycin. It was clindamycin-susceptible, so we later on switched to clindamycin."
As in other cases, the community MRSA strains had different antibiotic susceptibility patterns from those found in the hospital. Of the community-acquired MRSA isolates, 100% were susceptible to clindamycin, which was ineffective against 53% of comparative nosocomial strains. In the Corpus Christi area, clindamycin is among the drugs of choice for empiric treatment of children with suspected or confirmed community-acquired MRSA infections on an outpatient basis while awaiting culture and/or sensitivity results, Fergie reports. Vancomycin may be considered for use as a single agent or in combination with clindamycin or other drugs in severely ill children hospitalized with community-acquired MRSA infections, he adds.
Watch for nonresponsive infections
As a result of the cases, Fergie and colleagues recommend that MRSA should be considered when children with skin and soft-tissue infections — or more serious infections like pneumonia — do not respond to outpatient therapy with standard anti-staphylococcal oral antibiotics (e.g., cephalexin). Soft-tissue infections (cellulitis or abscess) accounted for 12 of the 14 cases. The other two children included one with toxic shock syndrome and another with pneumonia.
While cases in pediatrics are being increasingly reported, another study presented at the CDC conference indicates that low levels of community-acquired MRSA may be circulating among adults as well.3 Aware that other investigators are finding that the community strains are susceptible to clindamycin, researchers in Chicago hypothesized that screening for MRSA isolates susceptible to the drug may be a good marker to detect community-acquired infections.
I think it is probably going to increase’
Overall, they reviewed 2,817 staph isolates from 1998-1999, identifying 20 cases that appeared to be community-acquired MRSA. Though estimating that the level of community-acquired MRSA in adults was only in the 1% range, one of the researchers says the pathogen may be on the rise in the adult population. "I think it is probably going to increase, just as it is increasing everywhere else," says Nila Suntharam, MD, second-year fellow in infectious disease at Northwestern Memorial Hospital in Chicago. "As a next step in the study, we are thinking about going out in the community to satellite clinics and looking at the adult population there."
The researchers retrospectively reviewed the MRSA isolates from a 20-month study period ending in September 1999. Patients were not considered to have community-acquired MRSA if they had been admitted to the hospital within the preceding two years or if their isolate had been obtained more than 72 hours after admission. If there was no indication of a prior admission to the hospital, the chart was reviewed to determine if there had been an admission to an outside facility within the prior two years.
In 1998, there were a total of 1,658 S. aureus isolates, including 616 that were MRSA. Of those, 80 were clindamycin-susceptible. Those were recovered from 47 patients, 14 of whom appeared to have community-acquired infections. Through September of the following year, another 1,159 S. aureus isolates were reviewed, and 455 were found to be MRSA. Of the 445 isolates, 81 were clindamycin-susceptible. They were recovered from 34 patients, six of whom appeared to have community-acquired infections. The majority of the cases were skin/soft-tissue infections, the researchers reported.
While the two aforementioned studies reported community-acquired MRSA in the absence of obvious risk factors, other research presented at the CDC conference showed that MRSA — regardless of origin — continues to move between hospitals and nursing homes.4
Investigators at Prince George’s Hospital Center in Cheverly, MD, retrospectively reviewed medical records and identified 746 MRSA patients. Overall, 54% of the infections were considered nosocomial, occurring 48 to 78 hours after admission. The remaining 46% came in with MRSA, reported Abdul Zafar, MBBS, MPH, director of infection control at the hospital. Of the incoming MRSA patients, 29% were admitted directly from nursing homes, In addition, 71% of the incoming cases had a history of prior antibiotic use, and nearly 80% had a history of previous hospital admission. The findings may be the result of both transmission between facilities via transferring patients and prolonged colonization of individuals, he says. "My feeling is, once Staph aureus becomes MRSA, it stays with you for the rest of your life," he tells HIC.
References
1. Fergie J, Purcell K, Wright, et al. Community-acquired methicillin resistant Staphylococcus aureus in hospitalized children in South Texas. Abstract P-T2-02. Presented at the Centers for Disease Control and Prevention 4th Decennial International Conference on Nosocomial and Healthcare-Associated Infections. Atlanta; March 5-9, 2000.
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. Suntharam N, Hacek DM, Peterson LR, et al. Community versus nosocomial acquired methicillin-resistant Staphylococcus aureus at a university hospital in the central U.S. Abstract P-T2-03. Presented at the Centers for Disease Control and Prevention 4th Decennial International Conference on Nosocomial and Healthcare-Associated Infections. Atlanta; March 5-9, 2000.
4. Zafar AB, Beidas SO, Sylvester SK, et al. Prevalence of MRSA in [the] community. Abstract P-T2-01. Presented at the Centers for Disease Control and Prevention 4th Decennial International Conference on Nosocomial and Healthcare-Associated Infections. Atlanta; March 5-9, 2000.
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