Is 'flesh-eating' strep moving from A to B?
December 1, 1997 3 minutes read
Is flesh-eating’ strep moving from A to B?
Is unusual blip’ an emerging syndrome?
Three documented cases of necrotizing fasciitis caused by Group B streptococcus infections in less than a year have Canadian researchers wondering if they have uncovered an emerging syndrome.
"We found three cases over a period of 10 months when there had previously been only four cases described [in the medical literature] over 40 years," says Michael Gardam, MD, chief resident in infectious diseases and medical microbiology at McGill University in Montreal. "On first glance it certainly looks like there may be something new going on." Almost all previous reports of the tabloid-celebrated "flesh eating bacteria" have been caused by Group A streptococcus, which has caused both community and nosocomial outbreaks.
The researchers found three unrelated group B strep infections in Southern Ontario and Quebec. All three patients presented with severe pain and rapidly progressive infections requiring emergency surgery. Two of the patients suffered from long-standing diabetes, while one had a history of leukemia. One of the patients died. All of the cases were in the community, but there has been at least one prior case of a probable hospital-acquired group B necrotizing fasciitis in the United States, he says. The infections are thought to have arisen within the patients after prolonged colonization rather than transmission occurring in the community.
"Person-to-person transmission is always possible, but it seems more likely knowing the epidemiology of this disease that they actually were [colonized] for a long period of time," he says.
Group B strep necrotizing fasciitis is not a reportable disease, but the cases were connected through discussions among clinical colleagues. The cases were reported recently in Toronto at the meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), where Gardam was advised by a participant that another case may have occurred recently in the Seattle area.
"We have a feeling that things are probably increasing because Group A strep has actually increased five-fold in Canada over the last four years," he tells Hospital Infection Control. "You get the sense that invasive streptococcal disease is on the increase; we just don’t have enough data to say for sure yet. Whether this is a blip and we will go back to seeing one every 10 years, or whether this is something real, we should know over the next year or two."
Group B streptococcus is found in vaginal secretions in 10% to 30% of women, and is the most common cause of serious infectious disease in newborns. It has also been recognized to cause a variety of infections in adults with diabetes, cancer, and other serious diseases. The ability of group B streptococci to cause necrotizing fasciitis with such frequency, however, would represent a new emerging clinical syndrome, Gardam notes.
"Group B in and of itself is not something from a infection control standpoint that we usually worry about," he says. "But we know now that if you are in close contact with someone with a Group A necrotizing fasciitis strain, it can be spread."
The strains are being examined to try to determine whether virulence factors from Group A strep have been genetically transferred to Group B. That has not been previously identified, but there has been documentation of transfer of genetic materials between different strains of Group A, he notes.
"We do have the precedent that genes are being shared between different streptococci, so it is certainly reasonable to think that could be happening between Group B and Group A," he says.
Interestingly, the research might actually help determine the specific virulence factors in Group A strep that enable it to cause necrotizing fasciitis by revealing what genetic elements were transferred to the Group B pathogens.
"That would be quite helpful, because we are not sure which virulence factor for group A causes necrotizing fasciitis," Gardam says. "So if you can show that a particular virulence factor [moved] from A to B and both strains cause necrotizing fasciitis, we may have found the actual cause of this."
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