TKANSACTIONS OF THE ROYAL SOCIETY OF TROPICAI. MEDICINE: AND HYGIIXE (1985) 79, 719-721 719 Salmonella and Shigella in adult diarrhoea in Addis Ababa- prevalence and antibiograms M. ASHENAFI’ AND M. GEDEBOU’ ‘Dept. of Basic Sciences, Awassa Junior College of Agriculture and 2Dept. of Medical Microbiology and Parasitology, Faculty of Medicine, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia Abstract Ninety Shigella and 45 Salmonella strains were isolated from 1000 adult diarrhoeal out-patients from various hospitals and clinics in Addis Ababa. The Shigella species were isolated in the order of frequency of S. jkxneri, S. dysenteriae, S. boydii and S. sonnei and the Salmonella in the order of Group C, Group B, S. typhi, other Group D and Groups A and E. Almost all Shigella isolates were sensitive to cephalothin, gentamicin, kanamycin, polymyxin B and trimethoprim-sulphamethoxazole. About 17% were sensitive to the 11 drugs tested. Muhiole resistance was detected in 62%. the most common to six drugs (27%). All Sal&nella isolates ‘were sensitive to gentamicin, ~&lymyxin B and trimethoprim-sulphamethoxazole. About 69% were sensitive to all drugs tested. 22% were multiply resistant and the most common was to eight drugs (18%). Introduction The aetiology of adult diarrhoea in Ethiopia has not heen fully defined despite some reports on some aetiological agents (WALLACE, 1977; GEDEBOU & TASSEW, 1981, 1982; GEBREYOHANNES & LIM- MENEH, 1980). Information on the frequency of isolation of Salmonella and Shigella from adult diar- rhoea in this country is also lacking or incomplete (GEBREYOHANNES & LIMENEH, 1980; GEDEBOU & TASSEW,1982). The purpose of this study was to determine the frequency of Salmonella and Shigella in the aetiology of diarrhoea in adult out-patients in Addis Ababa and the drug sensitivity of the isolates. Materials and Methods Collection of specimens Stool specimensfrom diarrhoeal out-patients from various hospitals and clinics (Table I) in Addis Ababa were collected, between November 1982 and March 1983, on buffer-treated swabs and kept in tubes of “Gary and Blair” transport menstrum (EDWARDS & EWING, 1972). Isolation and identijicatim The swabs were inoculated on to MacConkey, SS and brilliant green agar plates and into a tube of selenite enrichment broth (OXOID) and incubated at 35 to 37°C for 18 to 24 hours. The selenite broth cultures were plated on the same type of agar media and incubated at 35 to 37°C for 18 to 24 hours. Colonies typical of Salmonella and Shigella were picked from each plate, characterized biochemically followine standard methods (EDWARDS & EWING. 1972) and co&n&d by serogrouping ‘with slide agglutination using Difco antisera. Drug sensitivity testing Sensitivity testing was done on Mueller-Hinton agar plates following the standardized disk diffusion technique (BAUER et al., 1966)with BBL drug disks: ampicillin (Amp), 10 pg; carbenicillin (Car), 100 pg; cephalothin (Cep), 30 pg; chlor- amphenicol (Chl), 30 pg; gentamicin (Gen), 10 ug; kanamy- tin (Kan), 10 pg; polymyxin B (PO]), 300 units; streptomy- cin (Str), 30 pg; sulphadiazine (Sul), 1 mg; tetracycline (Tet), 30 pg; trimethoprim-sulphamethoxazole (Tri-sul), 25 pg. The reference strain Escherichiacoli (ATCC 25922), sensitive to all the drugs used in this study, was routinely tested. Interoretation of readings as sensitive. intermediate or resistant ‘was made accord&g to a chart (MATSEN& BARRY, 1974).Intermediate readings were few and therefore considered as sensitive for the purpose of assessing the data. Results Isolation The frequency of Salmonella and Shigella is shown in Table I. The Salmorzlla were isolated in the order of Groups C and B, S. typhi, other Group D and Groups A and E. Of the Shigella species, S. fEexneri was most common followed by S. dysenteriae, S. boydii and S. sonnei. Sensitivity to drugs All the Salmonella isolates were sensitive to genta- micin, polymyxin B and trimethoprim-sulphamethox- azole. Sensitivity to the remaining eight drugs varied between 73% and 82%. The single isolates of Groups A and E, all S. typhi, almost all the other Group D and most Group B isolates were sensitive to all 11 drugs. Group C strains were sensitive only to gentamicin, polymyxin B and trimethoprim-sulphamethoxazole. About 69% of all isolates were sensitive to the 11 drugs. Multiple drug resistance (resistance to three or more drugs) wasdetectedin 22.2%. all in GrouD C. Of the seven-d’ifferent resistancepatterns noted, the most common was AmplCar/CeplChl/KanlStr/Sul/Tet (18%). All or nearly all the Shigella specieswere sensitive to cephalothin, kanamycin, gentamicin, polymyxin B or trimethoprim-sulphamethoxazole. Sensitivity to the other agents varied between 31% and 58%. About 17%were sensitive to all 11 drugs. Multiple resistance was detected in 62% with 18 Gfferent patterns. The most common was Amn/Car/Chl/Str/Tet (26.7%). detected in all the species except in S. so&ei. ” Discussion Our isolation rate of Salmonella (4.5%) was higher than that (1%) previously reported from Ethiopia * Address for correspondence: Prof. Messele Gedebou, P.O. Box 6667, Addis Ababa, Ethiopia.