Antimicrobial Sensitivity Pattern of Salmonella Typhi: Emergence of Resistant Strains

Background Typhoid fever is still an important public health problem in developing countries. Increasing resistance of Salmonella Typhi to antibiotics is alarming. New extensively drug-resistant strains of Salmonella reported first time in Pakistan, resistant not only to first-line drugs and ciprofloxacin but also resistant to ceftriaxone, had spread globally, including the USA. Due to this continuously changing pattern of antimicrobial resistance in typhoid fever due to Salmonella Typhi, there is a substantial need to study the resistance pattern of Salmonella Typhi frequently in different areas to detect the new resistant strains timely. The objective of this study was to evaluate the current trends in the resistance pattern of Salmonella Typhi in a tertiary care hospital in Northern Punjab. Methods This cross-sectional study was conducted at the Department of Medicine, Pakistan Ordnance Factories (POF) Hospital Wah Cant in collaboration with the Department of Pathology, from 1^st January 2019 to 30^th September 2019. Culture-positive patients of typhoid fever age more than 12 years, either male or female, were included in the study. The antimicrobial susceptibility of the isolates was determined by the disc diffusion method of Kirby Bauer on Mueller-Hinton agar using Clinical Laboratory Standards Institute (CLSI) guidelines. The antimicrobial agents tested were ampicillin (10 μg), chloramphenicol (30 μg), trimethoprim/sulfamethoxazole (1.25/23.75 μg), ciprofloxacin (5 μg), ceftriaxone (30μg), azithromycin (15μg), imipenem (10μg) and meropenem (10μg). Results A total of 81 culture-positive patients were included in the study. Out of these, 59% were male, and 41 % were female. Mean age was 23.8±19.1 years ranging from 12 to 91 years. Salmonella Typhi showed the highest sensitivity to imipenem 100% and azithromycin 95%; the lowest sensitivity was to ciprofloxacin 3.7%. Almost 50% of patients were resistant to ceftriaxone, and 48% were resistant to meropenem. The number of multidrug-resistant cases reported was 20%, whereas 47% of strains were extensively drug-resistant. Conclusion Resistance to antimicrobial agents is increasing in patients with typhoid fever due to Salmonella Typhi; especially the extensively drug-resistant strains of Salmonella Typhi are increasing rapidly. New emerging strains resistant to carbapenems found in our study are a big threat. Prescription of antibiotics according to culture and sensitivity for sufficient duration in patients of typhoid fever due to Salmonella Typhi is necessary to prevent the emergence of new resistant strains.