2012 Los Angeles Outbreak Featured Drug-Resistant Shigella

The May 2012 Shigella outbreak traced to a private bridge club in California’s Los Angeles county was found to be the first involving Shigella bacteria with a decreased susceptibility to azithromycin, an antibiotic that is usually effective against multi-drug-resistant Shigella, the U.S. Centers for Disease Control and Prevention reported last week.

Cases of shigellosis with lowered susceptibility to azithromycin have appeared sporadically in the U.S., but this was the first documented outbreak. Outbreak samples submitted to the CDC also showed resistance to streptomycin, sulfisoxazole, tetracycline and trimethoprim-sulfamethoxazole.

Patients were found to have visited or worked at the bridge club between May 22 and 26, 2012, with ages ranging from 54 to 98 years old.

County health investigators ultimately found 39 shigellosis cases among visitors, along with two workers who experienced symptoms such as diarrhea, and an additional two infected workers who did not show symptoms. Thirty-one sought medical care and 10 were hospitalized.

Investigators did not find a specific outbreak source. PulseNet, a nationwide epidemiology network, identified two additional Shigella isolates genetically indistinguishable from the outbreak strain: one from a Pennsylvania man who visited L.A. in April, and another from a Hawaii man who visited L.A. during April and May. Neither of these patients had a connection to the bridge club.

ScottHurd

Note,

this antibiotic is NEVER used in livestock production.

Scott DVM
Mike_Mychajlonka_PhD

The meat industry is just going to have to come to grips with the fact that the co-selection of antibiotic resistance, even across very different antibiotic families, is a reality. In this case, it is quite correct to say that that azithromycin is never given to livestock production. However, it is also true that azithromycin is a macrolide and other members of that antibiotic family (e.g., erythromycinm tylosin, tilmicosan and gamithromycin) are indeed used in livestock production. In fact, the last of these, gamithromycin, is very similar indeed to azithromycin, having the same 15-member lactone ring. Therefore, I would expect one bio-similar to select for resistance to another. The meat industry is under a real challenge right now with the disturbing rise in antibiotic resistance. To overcome that challenge the meat industry will have to, I think, adopt a leadership position in this are. That leadership position will remain out of reach for so long as the first response is denial.