Journal Article

<i>Salmonella enterica</i> Serovar Paratyphi A and <i>S. enterica</i> Serovar Typhi Cause Indistinguishable Clinical Syndromes in Kathmandu, Nepal

Ashish P. Maskey, Jeremy N. Day, Phung Quoc Tuan, Guy E. Thwaites, James I. Campbell, Mark Zimmerman, Jeremy J. Farrar and Buddha Basnyat

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 42, issue 9, pages 1247-1253
Published in print May 2006 | ISSN: 1058-4838
Published online May 2006 | e-ISSN: 1537-6591 | DOI: http://dx.doi.org/10.1086/503033
Salmonella enterica Serovar Paratyphi A and S. enterica Serovar Typhi Cause Indistinguishable Clinical Syndromes in Kathmandu, Nepal

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Background. Enteric fever is a major global problem. Emergence of antibacterial resistance threatens to render current treatments ineffective. There is little research or public health effort directed toward Salmonella enterica serovar Paratyphi A, because it is assumed to cause less severe enteric fever than does S. enterica serovar Typhi. There are few data on which to base this assumption, little is known of the serovar's antibacterial susceptibilities, and there is no readily available tolerable vaccination.

Methods. A prospective study was conducted of 609 consecutive cases of enteric fever (confirmed by blood culture) to compare the clinical phenotypes and antibacterial susceptibilities in S. Typhi and S. Paratyphi A infections. Variables independently associated with either infection were identified to develop a diagnostic rule to distinguish the infections. All isolates were tested for susceptibility to antibacterials.

Results. Six hundred nine patients (409 with S. Typhi infection and 200 with S. Paratyphi A infection) presented during the study period. The infections were clinically indistinguishable and had equal severity. Nalidixic acid resistance, which predicts a poor response to fluoroquinolone treatment, was extremely common (75.25% of S. Paratyphi A isolates and 50.5% of S. Typhi isolates; P < .001). S. Paratyphi A was more likely to be resistant to ofloxacin (3.6% vs. 0.5%; P = .007) or to have intermediate susceptibility to ofloxacin (28.7% vs. 1.8%; P < .001) or ciprofloxacin (39.4% vs. 8.2%; P < .001). MICs for S. Paratyphi A were higher than for S. Typhi (MIC of ciprofloxacin, 0.75 vs. 0.38 µg/mL [P < .001]; MIC of ofloxacin, 2.0 vs. 0.75 µg/mL [P < .001]).

Conclusions. The importance of S. Paratyphi A has been underestimated. Infection is common, the agent causes disease as severe as that caused by S. Typhi and is highly likely to be drug resistant. Drug resistance and lack of effective vaccination suggest that S. Paratyphi A infection may become a major world health problem.

Journal Article.  4073 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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