Group A strep cluster hits maternity unit in New York
Patient dies of necrotizing fasciitis after giving birth
A cluster of Group A streptococcus infections recently struck an obstetrical unit of a Rochester, NY, hospital, resulting in one patient death from necrotizing fasciitis 18 days after she gave birth by cesarean section. Two other patients were infected, and two health care workers in the unit were colonized with the same strep strain.
Though the strains matched by DNA typing in all five cases, it is not clear whether transmission occurred from health care workers to patients or vice versa, says Paul S. Graman, MD, hospital epidemiologist at Strong Memorial Hospital and associate professor of medicine at the University of Rochester Medical Center.
"We are concerned that the health care workers could be the source to one or more of the patients, and it is certainly possible," Graman tells Hospital Infection Control. "But it is equally plausible that health care workers could have been infected by contact with patients."
The three cases of Group A strep occurred among female patients who delivered babies at Strong Memorial between Feb. 16 and 20. One of the patients a 39-year-old who delivered by cesarean section on Feb. 17 developed a surgical wound infection and died of necrotizing fasciitis March 7 without leaving the hospital. The other two patients including a postpartum Group A strep bacteremia without necrotizing fasciitis and a wound infection that was not invasive recovered and were discharged from the hospital. None of the newborns were infected.
An investigation by state public health officials did not identify any evidence of a community outbreak involving a common source of infection, or a significantly higher-than-expected number of cases occurring in the region for the period. From the beginning of the year to March 14, 1997, 22 people acquired invasive Group A strep in the Rochester area and five died both morbidity and mortality levels that fell within the expected rate for the disease.
Hospital established hotline
Review of all 1997 case reports did not reveal any common link among the individuals, with the exception of the three cases that occurred among patients on the obstetrical unit at the hospital, health officials concluded. Virtually all other cases occurred in the community, in 15 different cities, and were not linked with the maternity cases at Strong Memorial. The case caused heightened concern in the community, and the hospital established an informational hotline and distributed a staff handout on strep developed by the health department. (See handout, p. 69.)
"It is an extremely difficult situation because the media tends to emphasize the sensationalistic aspects and to fuel alarm among the public," Graman says. "Infection control nurses and hospital administration were involved in educating and reassuring staff."
While noting she could not comment on the Strong Memorial cluster because she was not directly involved in the case, a leading Group A streptococcus researcher says postpartum outbreaks of the pathogen are well-described in the literature.
"Postpartum Group A strep is a sentinel event, because you need to know that they didn’t acquire it in your hospital and some of them clearly don’t," says Allison McGeer, MD, director of infection control at Mount Sinai and Princess Margaret Hospitals in Toronto.
A review of 323 patients with Group A strep by McGeer and other members of the Ontario Group A Streptococcal Group found that 44 (14%) of the cases were nosocomial.1 Of those, 16 occurred in women postpartum, including two surgical-site infections after cesarean section and 14 cases of endometritis after vaginal delivery. The rate of infection in the postpartum group was 0.5 per 10,000 deliveries. Even the occurrence of two cases in close proximity should prompt an epidemiologic investigation, McGeer recommends.
Two in a row is serious
"One in every 20,000 deliveries you would expect to be complicated by Group A strep," she says. "So two of them in a row is a serious coincidence. They may not be related, but you need to assume they are. Similarly, if you look at adult health care workers, the carriage rate is somewhere around 1%. So if you swab 50 people and you find two that are positive it might occur, but the probability is fairly low."
Overall, 40 to 50 health care workers were cultured at the hospital, and five had Group A strep pharyngitis, including two health care workers who participated in the three deliveries. One health care worker who cared for two of the three infected patients had a positive throat culture for Group A strep infection, but showed no symptoms of strep throat while caring for the patients. Another worker, who cared for the third infected patient and also had no symptoms at the time of providing patient care, was subsequently diagnosed with Group A streptococcus on Feb. 22, according to the state health department.
Streptococcal cultures from the infected maternity patients and health care workers in the maternity unit were tested using pulsed-field gel electrophoresis. Results showed that the Group A streptococcus strains from the three patients and two maternity unit health care workers were identical, and were different from strains obtained from patients admitted to other parts of the hospital, the health department reported.
"Based on previous testing of streptococcal cultures statewide and from the Rochester area, the identified strain appears to be an uncommon one," the health department reported.
The colonized health care workers were treated for 10 days with penicillin, Graman notes. The two health care workers who had direct contact with the case patients were also given rifampin to improve the eradication rate for the final four days of the treatment course. All of the treated workers were recultured five days after completion of the course and were permitted to return to work when they were asymptomatic and had received at least 24 to 48 hours of antibiotic therapy.
"I think the crucial thing is to move quickly and decisively in identifying the health care workers who are directly involved in the deliveries and immediate postpartum care," Graman advises. "Identify them to determine if any have symptoms and obtain the appropriate cultures throat, rectal, and vaginal. Of course, remove anyone with symptomatic illness from patient contact or work."
Infection control measures included re-emphasizing strict adherence to aseptic technique, and placing case patients or suspected case patients on contact isolation until at least 24 hours of antibiotic therapy had been completed. Isolation measures included private rooms and gloves for contact with patients, Graman says, adding that the newborns of the infected patients were placed in isolation and were cultured.
"We also instituted a restricted visitation policy, which is no visitors under the age of 12 and all visitors screened for any symptoms of sore throat, fever, or skin infections by one of the nursing staff at the time of visiting," he says.
The Centers for Disease Control and Prevention estimates that 10,000 to 15,000 cases of Group A strep infection occur in the U.S. each year due to the bacterium Streptococcus pyogenes. The vast majority are mild, and present as strep throat or skin infections. Necrotizing fasciitis, which results in progressive destruction of fat and muscle, accounts for 5% to 10% of all strep infections.
"The incidence of disease doesn’t seem to have changed in the past few years, and in some areas the proportion of M Type 1 infection which are the ones that have been most associated with severe disease seems to have decreased," says Benjamin Schwartz, MD, medical epidemiologist in the CDC childhood and respiratory diseases branch. "But we know that severe disease is still occurring, and it frequently seems to occur in clusters. When a virulent strain passes through a community, there are several cases that occur."
Reference
1. Davies HD, McGeer A, Schwartz B, et al. Invasive Group A Streptococcal infections in Ontario, Canada. N Engl J Med 1996; 335:547-554.
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