Results of a 5-year prospective surveillance study of antibiotic resistance among Salmonella enterica isolates and ceftriaxone therapy among children hospitalized for acute diarrhea.

BACKGROUND

The spread of resistant Salmonella strains continues to increase worldwide. It is necessary to establish epidemiologic information to determine an appropriate empiric antibiotic regimen (when indicated) in infants and children with suspected Salmonella infections for whom the results of susceptibility tests are not yet available.

OBJECTIVES

The aim of the present study was to investigate resistance rates and their modifications among Salmonella enterica strains isolated from Italian children hospitalized for acute diarrhea over 5 years. In addition, when antibiotic treatment was indicated, we assessed the in vivo success of parenteral ceftriaxone therapy.

METHODS

This study included children admitted consecutively for acute diarrhea to the Division of Pediatrics and Infectious Diseases, Department of Pediatrics, University of Florence, Italy, from January 1, 1997, to December 31, 2001. S enterica strains were isolated from stool cultures, biochemically identified, and serotyped. These isolates were tested by disk-diffusion assay, using the Kirby-Bauer method, for susceptibilities to ampicillin, ceftriaxone, ciprofloxacin, chloramphenicol, neomycin, tetracycline, and trimethoprim/sulfamethoxazole. The limits used for definition of resistance were those established by the guidelines of the National Committee for Clinical Laboratory Standards.

RESULTS

A total of 2003 children (1051 boys, 952 girls; median age, 10.3 years; age range, 1 month-16.8 years) with acute diarrhea were admitted to the study. S enterica strains were isolated using stool cultures from 218 (10.9%) children (108 boys, 110 girls; median age, 3.3 years; age range, 2 months-15.8 years). A total of 148 (67.9%) isolates were resistant to at least 1 antibiotic and 57 (26.1%) were multiresistant. The highest rates of resistance were those to tetracycline (132/218 [60.6%]), ampicillin (102/218 [46.8%]), and chloramphenicol (47/218 [21.6%]). The lowest rate of resistance was to ceftriaxone (4/218 [1.8%]). Overall, the rate of resistance to ciprofloxacin (19/218 [8.7%]) was significantly higher than that for ceftriaxone (P = 0.003). Salmonella typhimurium (119/218 [54.6%]) and Salmonella enteritidis (62/218 [28.4%]) were the most frequently identified serotypes. Ceftriaxone was effective in vivo in all 56 children who required antibiotic therapy.

CONCLUSIONS

There was a high prevalence of resistant S enterica strains. Ceftriaxone was used effectively in the treatment of S enterica infection in the population studied.