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Azithromycin may be an adequate agent for treating drug-resistant shigellosis, but physicians need to be aware that interpreting susceptibility of Shigella sonnei to it using standard in vitro susceptibility testing is difficult, investigators at Johns Hopkins University have reported.
Antimicrobial-resistant S. sonnei—the most common serogroup in the United States—is a growing problem in the United States, and azithromycin is recommended by the American Academy of Pediatrics and the Infectious Diseases Society of America as an oral agent for the treatment of shigellosis that can be used as an alternative to ampicillin or trimethoprim/sulfamethoxazole (TS).
There are no guidelines for in vitro azithromycin susceptibility testing for Shigella, however, and there is a lack of adequate data correlating the drug's minimal inhibitory concentration—a key component of what's measured during susceptibility testing—with clinical efficacy for the treatment of shigellosis.
In their own testing of azithromycin susceptibility, the investigators found that there were two zones of inhibition of growth for S. sonnei isolates, and that interpretations of susceptibility for a particular isolate can vary by which zone is used.
“Because azithromycin … is being increasingly used in the United States, there is an urgent need for development of validated in vitro antimicrobial breakpoints,” reported Sanjay K. Jain, M.D., and colleagues at Johns Hopkins (Pediatr. Infect. Dis. J. 2005;24:494–7).
Many pediatricians prescribe antimicrobials for children with shigellosis because they shorten the duration of illness and hasten bacteriologic cure, they said.
The investigators reviewed all Shigella isolates submitted to the Johns Hopkins microbiology laboratory during 1996–2000 and 2002—the year in which an outbreak of Shigella was observed at Johns Hopkins and nationally.
Of the 111 isolates submitted during the 1996–2000 period, 63% were resistant to ampicillin, 12% were resistant to TS, and 7% were multiresistant (resistant to both drugs).
In 2002, among 205 isolates submitted, 91% were resistant to ampicillin, 67% were resistant to TS, and 65% were multiresistant, the investigators reported.
Azithromycin may be an adequate agent for treating drug-resistant shigellosis, but physicians need to be aware that interpreting susceptibility of Shigella sonnei to it using standard in vitro susceptibility testing is difficult, investigators at Johns Hopkins University have reported.
Antimicrobial-resistant S. sonnei—the most common serogroup in the United States—is a growing problem in the United States, and azithromycin is recommended by the American Academy of Pediatrics and the Infectious Diseases Society of America as an oral agent for the treatment of shigellosis that can be used as an alternative to ampicillin or trimethoprim/sulfamethoxazole (TS).
There are no guidelines for in vitro azithromycin susceptibility testing for Shigella, however, and there is a lack of adequate data correlating the drug's minimal inhibitory concentration—a key component of what's measured during susceptibility testing—with clinical efficacy for the treatment of shigellosis.
In their own testing of azithromycin susceptibility, the investigators found that there were two zones of inhibition of growth for S. sonnei isolates, and that interpretations of susceptibility for a particular isolate can vary by which zone is used.
“Because azithromycin … is being increasingly used in the United States, there is an urgent need for development of validated in vitro antimicrobial breakpoints,” reported Sanjay K. Jain, M.D., and colleagues at Johns Hopkins (Pediatr. Infect. Dis. J. 2005;24:494–7).
Many pediatricians prescribe antimicrobials for children with shigellosis because they shorten the duration of illness and hasten bacteriologic cure, they said.
The investigators reviewed all Shigella isolates submitted to the Johns Hopkins microbiology laboratory during 1996–2000 and 2002—the year in which an outbreak of Shigella was observed at Johns Hopkins and nationally.
Of the 111 isolates submitted during the 1996–2000 period, 63% were resistant to ampicillin, 12% were resistant to TS, and 7% were multiresistant (resistant to both drugs).
In 2002, among 205 isolates submitted, 91% were resistant to ampicillin, 67% were resistant to TS, and 65% were multiresistant, the investigators reported.
Azithromycin may be an adequate agent for treating drug-resistant shigellosis, but physicians need to be aware that interpreting susceptibility of Shigella sonnei to it using standard in vitro susceptibility testing is difficult, investigators at Johns Hopkins University have reported.
Antimicrobial-resistant S. sonnei—the most common serogroup in the United States—is a growing problem in the United States, and azithromycin is recommended by the American Academy of Pediatrics and the Infectious Diseases Society of America as an oral agent for the treatment of shigellosis that can be used as an alternative to ampicillin or trimethoprim/sulfamethoxazole (TS).
There are no guidelines for in vitro azithromycin susceptibility testing for Shigella, however, and there is a lack of adequate data correlating the drug's minimal inhibitory concentration—a key component of what's measured during susceptibility testing—with clinical efficacy for the treatment of shigellosis.
In their own testing of azithromycin susceptibility, the investigators found that there were two zones of inhibition of growth for S. sonnei isolates, and that interpretations of susceptibility for a particular isolate can vary by which zone is used.
“Because azithromycin … is being increasingly used in the United States, there is an urgent need for development of validated in vitro antimicrobial breakpoints,” reported Sanjay K. Jain, M.D., and colleagues at Johns Hopkins (Pediatr. Infect. Dis. J. 2005;24:494–7).
Many pediatricians prescribe antimicrobials for children with shigellosis because they shorten the duration of illness and hasten bacteriologic cure, they said.
The investigators reviewed all Shigella isolates submitted to the Johns Hopkins microbiology laboratory during 1996–2000 and 2002—the year in which an outbreak of Shigella was observed at Johns Hopkins and nationally.
Of the 111 isolates submitted during the 1996–2000 period, 63% were resistant to ampicillin, 12% were resistant to TS, and 7% were multiresistant (resistant to both drugs).
In 2002, among 205 isolates submitted, 91% were resistant to ampicillin, 67% were resistant to TS, and 65% were multiresistant, the investigators reported.