A sudden increase in occurrence of Salmonella Paratyphi A infection in Rourkela,western Odisha

Dear Editor,

To date, enteric fever is prevalent worldwide and manifests itself as a major public health problem in low- and middle-income countries including India. ¹ Enteric fever, though classically caused by Salmonella enterica serotype Typhi, a causative aetiology by Salmonella enterica serotype Paratyphi A, has also been reported. ² Since 1996, there has been an increasing trend in isolation of the latter from north India. ³ An unusually high occurrence was reported from Chandigarh. ⁴ In 2004, between March and August, a sudden and unusual rise was reported from Rourkela, ⁵ and again in 2018, between May and October, a similar sudden rise among patients suspected of having enteric fever and subsequently treated in Ispat General Hospital, Rourkela. These were studied: blood culture was carried in 708 patients. Salmonella isolates were obtained in 36 (5.08%), of which 31 (4.38%) were S. Paratyphi A and 5 (0.7%) were S. Typhi. The former was sensitive to ceftriaxone. Sensitivity to amoxycillin and cotrimoxazole was 96.77%, to chloramphenicol 93.54%, to ciprofloxacin 90.32%, and to both gentamicin and amikacin only 80.64%. Only two isolates of S. Paratyphi A were multi-drug resistant.

In our previous study from 2004, all S. Paratyphi A isolates were susceptible to ciprofloxacin, ceftriaxone and cephotaxime. ⁵ Resistance to ciprofloxacin has been known to be rising steadily in the last decade. ¹ As in our previous study, ⁵ ceftriaxone has shown 100% sensitivity in our current study, as corroborated elsewhere. ¹ Chloramphenicol sensitivity of 89.5% in 2004 has increased to 93.5%, as is also found in another study, ¹ and a similar trend has been found for amoxicillin sensitivity. ¹ On account of increasing resistance to ciprofloxacin, third-generation cephalosporins such as ceftriaxone and cefixime have become the drugs of choice today. ¹ However, amoxicillin and chloramphenicol, owing to their high sensitivity against S. Paratyphi A, should be considered as the first-line antibiotics in order to reduce the use of ciprofloxacin and thereby diminish resistance to this drug.

Continuous monitoring of susceptibility patterns is needed to avoid the risk of multi-resistant strains of S. Typhi emerging as happened in an outbreak in Pakistan. ⁶ Typbar TCV (Bharat Biotech product) is the world’s first clinically proven conjugate typhoid vaccine and is the only approved vaccine for children and infants aged <2 years. A single dose elicited fourfold seroconversion rates of 98.05%, 99.17% and 92.13% in individuals aged ≥6 months–2 years, >2–15 years and >15–45 years, respectively, in a phase 3 clinical study. ⁷ This vaccine has already been recommended by the World Health Organization (WHO) Strategic Advisory Group for routine immunisations and is WHO-prequalified. If vaccinated at the proper age, Typbar TCV will most likely be able to protect individuals from suffering the effects of S. Typhi or S. Paratyphi A and B infection. Thus, in the future, the threat of S. Paratyphi as a global pathogen will be substantially decreased.