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Is your practice safe? Emerging community staph causes fatal infection
CA-MRSA threat puts new emphasis on infection prevention
Signaling an increasing risk to staff in physician offices, public health investigators suspect that a fatal infection with community-associated, methicillin-resistant Staphylococcus aureus (CA-MRSA) in a pediatric clinic worker in Nashville, TN, was occupationally acquired, Infection Control for Physician Practices has learned.
Though the case still is under investigation by the Centers for Disease Control and Prevention, interviews with CDC and state investigators reveal that a previously healthy 57-year-old worker at a pediatric clinic contracted CA-MRSA in October 2006 and died of septicemia after a weeklong hospitalization. One theory is that the worker contracted CA-MRSA from a clinic patient, some of whom were subsequently found to carry CA-MRSA USA300 strains like the one that killed her. In the aftermath of the worker's death, other staff members in the same clinic reported they previously had skin and soft-tissue infections that may have been acquired occupationally.
"Health care workers in outpatient settings are at risk because they are being exposed to these patients — even if it is only a relatively small proportion of them that have CA-MRSA — day in and day out," says Rand Carpenter, DVM, the CDC Epidemic Intelligence Service officer who is investigating the case. "There are risks. Some of the people working in this clinic had skin and soft-tissue infections that were likely from exposure in the clinic."
With molecular strain typing and other aspects of the investigation still in progress, investigators emphasize that there remains the possibility the worker acquired CA-MRSA in the community rather than occupationally. "There were other people who worked in this pediatric outpatient clinic who had complained or who had reported skin infections," says William Schaffner, MD, chairman of the department of preventive medicine at Vanderbilt University School of Medicine in Nashville, and a consultant to the CDC investigation. "That triggered the whole investigation, and they could be tied together. But I don't think we will be able to link this particular fatal infection irrevocably to her work exposure. Serious infections occur in people who do not work in health care facilities also."
The CDC is trying to review the worker's medical history and assess the risk of patient contact, since she was not officially assigned to direct patient care duties. "The hospitalized worker was normally involved in administrative office duties, but communication about her duties and health history has been a little difficult and emotional with the staff there," Carpenter says. According to the CDC, the primary mode of transmission is typically via hands that may become contaminated by contact with colonized or infected individuals or devices, items, or environmental surfaces contaminated with body fluids containing CA-MRSA.
In any case, the fatal infection in the pediatric clinic worker underscores the rapid and wide-spread emergence of CA-MRSA, which is capable of causing severe infections in otherwise healthy people. "We see it coming in all the time," says Judie Bringhurst, RN, BSN, CIC, an infection control professional responsible for oversight and education in physician offices and clinics affiliated with Duke University Medical Center in Durham, NC. "Honestly, there are days when I think CA-MRSA is going to take over the world. We are seeing it in the clinics, especially urgent care clinics where people come in with boils and 'spider bites.'"
USA300 in 40 states
The hardy and easily transmitted predominant U.S. strain of CA-MRSA has been detected in some 40 states. Of course, completely drug-susceptible staph strains can cause serious infections, but the emerging picture suggests that CA-MRSA is causing more severe disease than typical MRSA that has plagued hospitals for decades. "Infections with these strains have most commonly presented as skin disease in community settings," the CDC states in its most recent guidelines on the issue.1 "However, intrinsic virulence characteristics of the organisms can result in clinical manifestations similar to or potentially more severe than traditional health care-associated MRSA infections among hospitalized patients."
Indeed, CA-MRSA has resulted in reports of such severe infections as necrotizing pneumonia, necrotizing fasciitis, and toxic shock syndrome.2 More physician offices and clinics can expect to see incoming cases if CA-MRSA — particularly the USA300 strain — continues to establish a strong community presence. The fatal case in the Nashville clinic may one day be viewed as the occupational equivalent of a prior sentinel event: The deaths of four children in 1999 that heralded he independent emergence of resistant staph strains in the community.3
"I think these circumstances — that is the concern about CA-MRSA infections being acquired in the outpatient setting — are indeed a harbinger of more of these kinds of reports that will occur," Schaffner says.
The occurrence of the Nashville case in a pediatric practice is consistent with national trends. For example, a recent study of 10 North Carolina hospitals found that pediatric patients were at nearly six times greater risk of CA-MRSA infections than adult patients.4 The study showed an age-related variability in the prevalence of community MRSA infections, finding that 74% of cases in children under 18 were due to CA-MRSA. In addition, a study published last year found a 10-fold increase in nasal colonization of healthy children since 2001.5 "As colonization typically precedes infection, this increase may be a major factor in the emergence of community-associated MRSA as a pathogen of healthy children," the authors concluded.
Though pediatric physicians may be facing the vanguard of CA-MRSA emergence, that trend is subject to change. Currently, it appears more adult patients with CA-MRSA seek care in emergency rooms rather than physician offices. That was the conclusion of CDC investigators who recently estimated that there were 11.6 million ambulatory health care visits for skin and soft-tissue infections possibly due to S. aureus in the United States each year from 2001 through 2003.6 "These data indicate that the number of S. aureus skin and soft tissue infections is substantial and that the emergence of CA-MRSA may affect ambulatory health care in the United States," they concluded. "[The] rapid progression of lesions, frequently described as spider bites, may lead persons to seek care in emergency departments rather than physician offices."
In addition, CA-MRSA might disproportionately affect particular socioeconomic groups who are more likely to seek care in emergency settings rather than physician offices, they surmised. "However, this finding does not mean that visit rates to other ambulatory care settings will not increase as CA-MRSA continues to emerge," they warned.
A new emphasis on infection control
Given such trends, physician offices and clinics need to emphasize infection control precautions and environmental cleaning measures to ensure CA-MRSA does not infect staff members or other patients, investigators emphasize. Though specific breeches have not yet been identified, Carpenter said staff at the clinic were "inconsistently applying" recommended infection control guidelines. In general, the most recent CDC guidelines recommend that ambulatory settings use standard precautions for patients known to be infected or colonized with drug-resistant organisms such as CA-MRSA, making sure that gloves and gowns are used for contact with uncontrolled secretions, pressure ulcers, draining wounds, stool incontinence, and ostomy tubes and bags. With CA-MRSA emerging in communities, infection control professionals and consultants are trying to educate clinic staff — many of whom may not have extensive medical training — about the infection control basics.
"Not really to our surprise, when one goes into an outpatient setting you frequently find infection control issues that can be improved," Schaffner says. "They may think they are doing things appropriately, it's just that they haven't had their practices reviewed by a knowledgeable infection control practitioner in some time. I think we will see increasing attention devoted to enhancing infection control practices in the outpatient setting stimulated by the concern of CA-MRSA."
Concern about CA-MRSA was palpable in the Nashville clinic staff after seeing their co-worker's infection take a disastrous course. Again, the workers immediately suspected the case was of occupational origin because they too had incurred skin and soft-tissue infections that possibly were work-related.
"When this person was hospitalized with septicemia, it worried many of the staff there," Carpenter reports. "They began to talk amongst themselves and realized that there had been several skin and soft-tissue infections among them in the proceeding months. They were worried about a problem."
The CDC began an investigation of the clinic that included doing nasal swabs on staff and patients to detect colonization with CA-MRSA. "We did a nasal swab survey of the workers there, as well as a sample of the patients coming into the clinic just to see how much CA-MRSA and susceptible S. aureus were in those two populations," he explains. "We did a swipe survey of the environment of the clinic, the exam rooms, and public areas."
Though the numbers were still being crunched as this issue went to press, Carpenter confirmed that some of the patients were colonized with the USA300 CA-MRSA strain that infected the clinic worker. "We did find it in a few of the patients," he says. "We didn't get much of a medical history on these patients. We just grabbed everybody that came into the clinic for a couple of days and swabbed them."
Overall, 245 patients and 45 staff members were cultured. Though CA-MRSA was not found in other staff, 12 were positive for susceptible staph strains and two had MRSA strains typically seen in a hospital. Drug-susceptible staph strains also were found in a "limited" number of environmental samples, he adds.
The antibiotic susceptibility profile of the infecting USA300 isolate in the Nashville case has not been reported, but many community-acquired MRSA strains tend to be susceptible to tetracycline, clindamycin, and trimethoprim/sulfamethoxazole (TMP/SMX). However, resistance patterns in CA-MRSA strains in general are changing and becoming a matter of increasing concern, epidemiologists report. In any case, antibiotic susceptibility patterns are distinctly different from hospital strains, and initial empiric therapy often is inappropriate because physicians do not suspect resistant staph in the community. CDC guidelines emphasize that ambulatory settings that outsource microbiology laboratory services should "specify by contract that the laboratory provide either facility-specific susceptibility data or local or regional aggregate susceptibility data in order to identify prevalent MDROs and trends in the geographic area served."1