Rapid intercontinental spread of antibiotic-resistant Shigella flexneri has been associated with international travel by homosexual males (men who have sex with men, or MSM).
Bacteria: Shigella flexneri serotype 3a with multi-drug resistance including resistance to azithormycin
Risk factors for MSM spread:
(1) high numbers of sexual partners
(2) oro-anal contact
(3) no or rare condom use
(4) co-infection with other sexually-transmitted disease
(5) substance abuse
Factors favoring spread:
(1) low numbers of shigella bacteria required for disease transmission
(2) travel hubs (London, New York, etc)
(3) “recirculation” of pathogen among MSM population (suggested by atypical infections)
Normally a person develops serotype-specific immunity after an episode of shigellosis. With serotype 3a there are “atypical” infections with:
(1) chronic infection
(2) relapsing infection
(3) reinfection
(4) poor response to standard antibiotic therapy
Some patients with atypical infection may have impaired immune systems from HIV or other cause.
