Resistant Patterns and Minimal Inhibitory Concentration of Antimicrobial Agent Against of Shigella spp. in Thailand

Abstract

In-vitro drug resistant patterns and minimal inhibitory concentration 9 antimicrobial agents against of 4 serovars of Shigella spp. were determined. Two hundred strains obtained from WHO National Salmonella and Shigella Center consisting of Shigella dysenteriae (21 strains), Shigella flexneri (83 strains), Shigella boydii (20 strains) and Shigella sonnei (76 strains) were used. The tested drugs were Ampicillin (AM), Cefazolin (CZ), Trimethoprim-Sulfamethoxazole (TMP-SMX), Chloramphenicol (C) Tetracycline (TC), Ofloxacin (OFX), Nalidixic acid (NA), Streptomycin (SM) and kanamycin (K). All isolated tested were 100, 100, 98.5 and 97.5% sensitive to OFX, CZ, K and NA respectively. Resistance to AM, C, TC, TMP-SMX and SM were in the range of 9.2 – 90.5%. Most of the strains except 11 strains of Shigella sonnei, 7 Strains of Shigella boydii and 4 strain of Shigella flexneri were resistant to at least 1 drug. Muiltiple drug resistance was more common than single resistance. MIC of OFX and CZ were in the ranges of 0.03-0.125 µg/ml and 1-4 µg/ml while MIC₅₀ and MIC₉₀ were 0.06, 0.125 µg/ml and 2, 2 µg/ml respectively. MIC for SM, TC, C and AM were in the range of 1-64 µg/ml MIC₅₀ and MIC₉₀ for the most of 4 drug resistant strains were 64 and 64 µg/ml. However MIC₅₀ and MIC₉₀ for TMP-SMX were 16 and 16 µg/ml.