Journal of Clinical Microbiology, October 1999, p. 3113-3117, Vol. 37, No. 10
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Departament de Microbiologia,1 Malaties Infeccioses (Unitat de Medicina Tropical),4 and Unitat de Epidemiologia i Bioestadistica (Fundació Clinic),3 Hospital Clinic, Institut d'Investigacions Biomèdiques August Pí i Sunyer, Villarroel 170, Barcelona 08036, Spain, and Ifakara Health Research and Development Centre, National Institute for Medical Research, Ifakara, Tanzania2
Received 19 March 1999/Returned for modification 29 April 1999/Accepted 29 June 1999
Eighty-six strains of Shigella spp. were isolated
during the dry season from stool samples of children under 5 years of
age in Ifakara, Tanzania. The epidemiological relationship as well as
the antimicrobial susceptibility and mechanisms of resistance to
ampicillin, chloramphenicol, and co-trimoxazole were investigated. Four
different epidemiological tools, pulsed-field gel electrophoresis (PFGE), repetitive extragenic palindromic (REP)-PCR, plasmid analysis, and antibiogram, were compared for typing Shigella strains.
Seventy-eight (90%) strains were Shigella flexneri and
were distributed into four groups, by either PFGE or REP-PCR, with 51, 17, 7, and 3 strains. The four strains of Shigella
dysenteriae belonged to the same group, and the four strains of
Shigella sonnei were distributed in two groups with three
and one strain each. Plasmid analysis showed a high level of
heterogeneity among strains belonging to the same PFGE group, while the
antibiogram was less discriminative. REP-PCR provided an alternative,
rapid, powerful genotyping method for Shigella spp.
Overall, antimicrobial susceptibility testing showed a high level of
resistance to ampicillin (81.8%), chloramphenicol (72.7%),
tetracycline (96.9%), and co-trimoxazole (87.9%). Ampicillin resistance was related to an integron-borne OXA-1-type
-lactamase in 85.1% of the cases and to a TEM-1-type
-lactamase in the remaining 14.8%. Resistance to
co-trimoxazole was due to the presence of a dhfr Ia gene in
all groups except one of S. flexneri, where a dhfr
VII gene was found within an integron. Chloramphenicol resistance
was associated in every case with positive chloramphenicol acetyltransferase activity. All strains were susceptible to nalidixic acid, ciprofloxacin, ceftazidime, cefotaxime, and cefoxitin. Therefore, these antimicrobial agents may be good alternatives for the treatment of diarrhea caused by Shigella in Tanzania.
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