Enteric Fever in a 6-Year-Old Traveler Caused by Salmonella enterica Serotypes Typhi and Paratyphi A: Laboratory Detection Strategies and Treatment Options

Abstract

We report the first pediatric case of enteric fever caused by Salmonella enterica serotypes Typhi and Paratyphi A. Mixed infections are infrequently reported, potentially because detection of two different Salmonella serotypes in blood cultures is technically challenging. We suggest laboratory strategies to aid in the recognition of mixed infections. CASE REPORTA previously healthy 6-year-old boy was admitted with a history of intermittent fever and constipation for 7 days which progressed to vomiting, neck pain, myalgias, and headache for 2 days. Three weeks prior to admission, the patient had returned from a vacation to Pakistan with his family, at which point the patient had had 5 days of loose green stools which seemed to resolve. Two days prior to admission, the patient was given two doses of azithromycin by his family doctor. Of note, the patient had several sick contacts in Pakistan, including two cousins who had similar symptoms of vomiting and diarrhea, who were diagnosed with typhoid fever. Upon returning from Pakistan, the patient's father also had symptoms of nausea, indigestion, and low-grade fevers, but the father's urine, blood, and stool cultures were all negative for Salmonella. The patient's mother and 3-year-old brother were asymptomatic. Negative stool and urine cultures were obtained from the brother; the mother was not tested.Blood cultures obtained upon admission turned positive for Gram-negative bacilli after 12 h of incubation in the BacT/ Alert system (bioMerieux, Durham, NC). According to our laboratory's standard protocol, broth taken directly from the blood culture bottle was inoculated to a triple sugar iron (TSI) slant and MacConkey and 5% sheep blood agar plates. When the patient's physician phoned the laboratory to indicate a high suspicion of enteric fever in this patient, a drop of broth from the patient's blood culture bottle was inoculated into 3 ml of Mueller-Hinton broth and incubated at 37°C until the culture reached a turbidity equivalent to that of a 0.5 McFarland standard. This was then streaked onto a Mueller-Hinton agar plate, and a preliminary disk diffusion antibiotic susceptibility test was performed (32). An acid-over-alkaline reaction with weak H 2 S production was noted on the TSI slant, and the disk diffusion susceptibility test results appeared mixed, with growth inside the zone of inhibition for both the ampicillin and trimethoprim-sulfamethoxazole (SXT) disks. No obvious differences in colony morphology were noted on the blood or MacConkey agar subculture plates. A single colony from the blood agar was identified by API 20E (bioMerieux, Marcy l'Etoile, France) as Salmonella enterica serotype Paratyphi A, an organism that does not usually produce H 2 S. No H 2 S production was similarly noted on the API 20E performed on this colony; the organism was also negative for citrate and lysine decarboxylase, both indicative of S. enterica serotype Paratyphi A (17). The identification was further supported by serogrouping, using Wellcolex latex agglutination reagents ...

Paratyphoid Fever: Splicing the Global Analyses

“…Disease transmission can occur during this period if such infected individuals are involved in food handling or lack of personal hygiene 4 . Sometimes, a patient could be infected by both S. Typhi and S. Paratyphi A 68 , 69 .…”