The most common cause of travelers' diarrhea, usually a self-limited illness without fever lasting several days, is infection with noninvasive enterotoxigenic (ETEC) or enteroaggregative (EAEC) strains of Escherichia coli. Campylobacter, Shigella, Salmonella, Aeromonas, viruses and parasites are less common.

A study now available on the web site of The New England Journal of Medicine (LY Park-Wyllie et al. Outpatient gatifloxacin therapy and dysglycemia in older adults. www.nejm.org, published online March 1, 2006) reports an increased risk of hypoglycemia (RR 4.3) and hyperglycemia (RR 16.7) with use of gatifloxacin (Tequin), a fluoroquinolone antibiotic. The Medical Letter published an article on this risk in 2003 (vol. 45, page 64); at that time the extent to which other fluoroquinolones carried the same risk was unclear. The recent report indicates that, except for a slightly increased relative risk of hypoglycemia (RR 1.5) with levofloxacin (Levaquin), they do not. Gatifloxacin, levofloxacin, moxifloxacin (Avelox) and gemifloxacin (Factive) are more active than other quinolones against gram-positive organisms such as Streptococcus pneumoniae, including strains highly resistant to penicillin; they are sometimes called "the respiratory quinolones." Given the availability of other drugs with similar in vitro and clinical activity, there is no good reason to continue to use gatifloxacin.