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  Table of Contents  
Year : 2016  |  Volume : 34  |  Issue : 3  |  Page : 397-398

Azithromycin susceptibility among clinical isolates of Salmonella: Interfacing guidelines with routine practices

1 Department of Microbiology, Kasturba Medical College, Manipal University, Manipal, Karnataka, India
2 Directorate of Research - Health Sciences, Manipal University, Manipal, Karnataka, India

Date of Submission02-Jun-2015
Date of Acceptance29-Sep-2015
Date of Web Publication12-Aug-2016

Correspondence Address:
V K Eshwara
Department of Microbiology, Kasturba Medical College, Manipal University, Manipal, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0255-0857.188376

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How to cite this article:
Chatterjee S, Eshwara V K, Tellapragada C, Mukhopadhyay C. Azithromycin susceptibility among clinical isolates of Salmonella: Interfacing guidelines with routine practices. Indian J Med Microbiol 2016;34:397-8

How to cite this URL:
Chatterjee S, Eshwara V K, Tellapragada C, Mukhopadhyay C. Azithromycin susceptibility among clinical isolates of Salmonella: Interfacing guidelines with routine practices. Indian J Med Microbiol [serial online] 2016 [cited 2021 Jan 15];34:397-8. Available from:

Dear Editor,

Increasing resistance to fluoroquinolone among Salmonellae has promoted the use of the third generation cephalosporins for treatment of enteric fever. Further, due to the availability of oral formulation, azithromycin has been a popular therapy for enteric fever in all age groups. [1] Until recently, no accepted breakpoints and disc diffusion zone interpretative criteria for azithromycin among Salmonellae were available although several clinical trials have stated good efficacy of azithromycin in treatment of enteric fever. [1] We present here the data on in-vitro activity of azithromycin on the clinical isolates of Salmonella Typhi and Salmonella Paratyphi-A based on updated breakpoints from a tertiary care hospital.

We tested 148 isolates of S. Typhi and S. Paratyphi-A for their susceptibility to ciprofloxacin and azithromycin by E-test (AB bioMérieux, Marcy l'Étoile, France) on BD Mueller-Hinton agar and results were interpreted, according to the new breakpoints established by Clinical and Laboratory Standards Institute. [2] Study isolates comprised of S. Typhi (95, 64%) and S. Paratyphi-A (53, 36%). The majority of isolates (97% S. Typhi and 98% S. Paratyphi-A) showed reduced susceptibility to ciprofloxacin. Resistance rates were higher among S. Paratyphi-A compared to S. Typhi (P < 0.001). All isolates were susceptible to azithromycin and similar to results of ciprofloxacin susceptibility, mean geometric minimum inhibitory concentration (MIC) was higher among S. Paratyphi-A as compared to S. Typhi. No multidrug-resistant (MDR) isolates were detected during the study period. All isolates were uniformly susceptible to ampicillin, ceftriaxone and trimethoprim/sulphamethoxazole and resistant to nalidixic acid by Kirby-Bauer disc diffusion method. Details of susceptibility are denoted in [Table 1].
Table 1: Details of susceptibility of S. Typhi and S. Paratyphi-A to ciprofloxacin and azithromycin

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current guidelines on the treatment of enteric fever in India are limited due to varying rates of resistance across the country. While resistance to fluoroquinolones is steeply increased, reduction in MDR rates apparently encourages the use of old drugs in treatment of Salmonella infections. [3] Besides ceftriaxone, azithromycin is the recent addition to armamentarium against enteric fever. Lack of standards for in-vitro susceptibility tests did not deter the therapeutic use of azithromycin owing to its clinical success. Several pharmacological properties of azithromycin including its ability to reach very high levels at intracellular spaces where Salmonella commonly resides despite its low serum levels and high MIC values have contributed to the good clinical response. However, an important concern is its prolonged sub-inhibitory concentrations at tissue might favour emergence of bacterial resistance highlighting the need to monitor MIC of Salmonellae against azithromycin. [1] Our results differ from other Indian reports of slightly higher azithromycin MICs while it is agreeable with data from other developing nations. [3],[4] In our study, S. Paratyphi-A seems to be relatively more resistant compared to S. Typhi, a fact that is supported by earlier report from Nepal that state the MICs of several antimicrobial agents were higher among isolates of S. Paratyphi-A.[5] Recently, increase in the occurrence of S. Paratyphi-A infections and non-availability of vaccine raises public health concern over this pathogen. Higher MICs of fluoroquinolones and azithromycin in the current study supports the upcoming resistance threat among S. Paratyphi-A.

Financial support and sponsorship

MD/MS/DM/MCH Thesis financial assistance programme of ICMR .

Conflicts of interest

There are no conflicts of interest.

 ~ References Top

Butler T. Treatment of typhoid fever in the 21 st century: Promises and shortcomings. Clin Microbiol Infect 2011;17:959-63.  Back to cited text no. 1
Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing, 25 th Informational Supplement. Approved Standard. CLSI Document M100-S25. 19 th ed. Wayne, PA: CLSI; 2015.  Back to cited text no. 2
Rai S, Jain S, Prasad KN, Ghoshal U, Dhole TN. Rationale of azithromycin prescribing practices for enteric fever in India. Indian J Med Microbiol 2012;30:30-3.  Back to cited text no. 3
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Parry CM, Thieu NT, Dolecek C, Karkey A, Gupta R, Turner P, et al. Clinically and microbiologically derived azithromycin susceptibility breakpoints for Salmonella enterica serovars Typhi and Paratyphi A. Antimicrob Agents Chemother 2015;59:2756-64.  Back to cited text no. 4
Maskey AP, Day JN, Phung QT, Thwaites GE, Campbell JI, Zimmerman M, et al. Salmonella enterica serovar Paratyphi A and S. enterica serovar Typhi cause indistinguishable clinical syndromes in Kathmandu, Nepal. Clin Infect Dis 2006;42:1247-53.  Back to cited text no. 5


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