An Update on Isolation of Extensively Drug Resistant (XDR) Salmonella enterica from Blood Cultures in a Tertiary Care Centre

Introduction: Typhoid fever is a public health issue, burdening many regions of the world with poor socioeconomic background. Management of this disease faces the major hurdle of antimicrobial resistance. The present study reveals current pattern of antimicrobial susceptibility among Salmonella enterica (Salmonella typhi & Salmonella paratyphi A) blood culture isolates from typhoid fever cases. Regular data collection about Salmonella infections and their response to antimicrobial agents, coupled with a long term commitment to providing adequate health information systems, is the key to effective planning and policy formation against typhoid fever. Aims & Objectives: To evaluate the prevalence of ceftriaxone resistant Salmonella enterica isolates from blood cultures in Shaikh Zayed Medical Complex for updating nosocomial antimicrobial resistance data. Place and duration of study: This research study was conducted at Shaikh Zayed Medical Complex, Lahore from March 2018 to May 2019. Material & Methods: Blood cultures positive for Salmonella enterica were analyzed, taking into consideration the gender & age of patients with typhoid fever. Antimicrobial susceptibility testing was carried out through disc diffusion method. The recommended antimicrobial agents for S. typhi (Salmonella typhi) & S. paratyphi A (Salmonella Parathyphi A) (as per CLSI, USA 2018/2019 guidelines; described later), were tested and analyzed during this study with the main focus on 3rd generation cephalosporin resistance pattern. Among second line treatment options, meropenem and azithromycin were selected for study. Results: Out of 899 isolates of Salmonella enterica (from 13964 samples for blood culture), 849 (94.4%) were S. typhi and 50 (5.6%) were S. paratyphi A. Of these, 57.1% isolates were from males, 42.9% from females, 81.7% from children (age less than 12 years) and 18.3% were from adults (age more than 12 years). A continuously rising resistance percentage was observed for 3rd generation cephalosporins over the span of fifteen months. It was 43.4% for ceftriaxone (CRO). No case of meropenem and azithromycin resistance was observed during study period. Conclusion: Demographic information was provided by this study regarding high level of resistance among Salmonella enterica isolates particularly S. typhi .The first line antibiotic drugs were a complete failure in ongoing outbreak of typhoid fever. The novel results of this study are the high resistance percentages for 3rd generation cehalosporins, whether oral or parenteral. This result is worrisome as it will leave us with no option but to resort to second line drugs. However, an increasing trend of blood culturing was observed in this research. Extensively drug resistant (XDR) Salmonella infection has definitely highlighted the importance of blood culture and its use as a more preferred diagnostic tool. Key words: Typhoid fever, Extensively drug resistant (XDR) Salmonella enterica, (S. typhi & S. paratyphi A), Antimicrobial Resistance, CRO (Ceftriaxone) resistance.