A biotyping Scheme for Salmonella typhi

Abstract

Thirty-nine isolates of Salmonella typhi ( S. typhi ) were studied using biotyping and antibiogram typing. Biotyping divided the isolates into six distinct biotypes on the basis of three biochemical tests, which included fermentation of bitter sugars: xylose and rhamnose; and reaction in Stern’s glycerol. Biotype 1 (28.2%) strains were the most wwprevalent, and did not utilize any of the three substrates. They were followed by biotype 2 (23.3%) strains that utilized all the three substrates and biotype 5 (23.3%) strains utilizing only bitter xylose, and biotype 6 (15.3%) strains utilizing bitter xylose and Stern’s glycerol. Biotypes 3 (7.67%) and 4 (2.3%) strains were less prevalent and utilized only Stern’s glycerol or both xylose and rhamnose, respectively. Antibiogram typing of S. typhi revealed the existence of multiple drug resistance to most of the 13 drugs used in the study. All isolates were resistant to oxacillin (1 μg), cephtazidine, 30 μg), erythromycin, 15 μg), vancomycin, 30 μg) and amoxyclaw (30 μ). 92.3% of the isolates were resistant to tetracycline (25 μg), streptomycin (19 μg/ml), and cotrimoxazole (25 μg), whereas 89.7% were resistant to chlorampenicol (30 μg), doxycycline (30 μg) and ampicillin (25 μg), respectively. About 2.6% of the isolates were resistant to gentamicin, whereas none was resistant to kanamycin. There was no correlation between biotype and antibiogram profile. In conclusion, this study has shown that most S. typhi strains in Kenya are multidrug resistant to the conventional drugs used in the treatment of typhoid fever. A reconsideration or temporary withdrawal of these drugs and their substitution with other drugs is highly recommended.