To the Editor: In cases of ty-phoid and paratyphoid fever, it is of-ten necessary to commence treatment before the results of laboratory sensi-tivity tests are available. It is therefore important to be aware of optional drug therapies available because some or-ganisms may be resistant to key anti-microbial drugs. For typhoid and para-typhoid, cipro. oxacin has become the fi rst-line drug of choice since the widespread emergence and spread of strains resistant to chloramphenicol, ampicillin, and trimethoprim (1).The Laboratory of Enteric Patho-gens (LEP) of the Health Protection Agency of England and Wales is the reference center for Salmonella enter-ica serovars Typhi and Paratyphi A for the United Kingdom; as such, this lab-oratory receives isolates from all cases of infection. Isolates are screened by breakpoint for resistance to antimi-crobial drugs at the following levels: chloramphenicol, 8 mg/L; ampicillin, 8 mg/L; trimethoprim, 2 mg/L; cipro-. oxacin, 0.125 mg/L (decreased sus-ceptibility); and 1.0 mg/L (high-level resistance), ceftriaxone, 1 mg/L, and cefotaxime, 1 mg/L. The levels for testing for resistance to chlorampheni-col, ampicillin, trimethoprim, ceftri-axone, and cefotaxime correspond to internationally accepted therapeutic levels for these antimicrobial agents. In contrast, the levels for cipro. oxa-cin (0.125 and 1.0 mg/L) have been chosen after observations of treatment failures at levels when used at below the expected recommended serum concentrations (2,3). Since 2005, a proportion of isolates exhibiting de-creased susceptibility and high-level resistance to cipro. oxacin have been tested for resistance to azithromycin by Etest (AB Biodisk, Solna, Swe-den), using drug-sensitive strains of S. Typhi and S. Paratyphi A as controls. From January 2001 through De-cember 2006, LEP reported 1,215 cases of S. Typhi infection and 1,274 cases of S. Paratyphi A infection. Of these, ≈60% (1,493) reported recent travel abroad; India and Pakistan were the most frequently visited countries (4). Other cases were associated with persons who had a history of such trav-el, but the numbers involved were dif-fi cult to document accurately because of underreporting of foreign travel and other communication problems
展开▼
