An Update on Isolation of Extensively Drug Resistant
(XDR) Salmonella enterica from Blood Cultures in a
Tertiary Care Centre
Authors: Hameed Sadia 
Published: January 2021

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.