Indian Journal of Pathology and Microbiology

: 2013  |  Volume : 56  |  Issue : 4  |  Page : 484--485

Antibiogram of Salmonella typhi and Salmonella paratyphi A in a tertiary care hospital in 2012

Bhavana Malavalli Venkatesh, Sangeeta Joshi, Ranjeeta Adhikary, Beena Hosdurg Bhaskar 
 Department of Microbiology, Manipal Hospital, Hal Airport Road, Bangalore, Karnataka, India

Correspondence Address:
Bhavana Malavalli Venkatesh
Department of Microbiology, Manipal Hospital, # 98, Rustom Bagh, Hal Airport Road, Bangalore - 560 017, Karnataka

How to cite this article:
Venkatesh BM, Joshi S, Adhikary R, Bhaskar BH. Antibiogram of Salmonella typhi and Salmonella paratyphi A in a tertiary care hospital in 2012.Indian J Pathol Microbiol 2013;56:484-485

How to cite this URL:
Venkatesh BM, Joshi S, Adhikary R, Bhaskar BH. Antibiogram of Salmonella typhi and Salmonella paratyphi A in a tertiary care hospital in 2012. Indian J Pathol Microbiol [serial online] 2013 [cited 2020 Aug 9 ];56:484-485
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Enteric fever continues to be a major public health problem in our country. The susceptibility pattern of Salmonella serotypes is subject to periodic changes and hence regular analysis of antibiograms is essential. The CLSI 2012 guidelines recommended new ciprofloxacin disk diffusion (sensitive: ≥31 mm, resistant: ≤20 mm) and minimum inhibitory concentration (MIC) interpretive criteria (sensitive: ≤0.06 μg/ml, resistant: ≥1 μg/ml) for Salmonella typhi and Salmonella paratyphi A. [1]

We analyzed the antibiogram of our hospital for the year 2012. There were 343 isolates of Salmonella enterica serovar Typhi and Salmonella enterica serovar Paratyphi A. Blood culture was done using BacT/ALERT 3D system (Biomerieux, France). Identification of the organism was done by standard biochemical and slide agglutination tests. [2] Antibiotic susceptibility testing for cotrimoxazole, chloramphenicol, ceftriaxone, nalidixic acid, and ciprofloxacin using disks (Himedia, India) was done by Kirby Bauer disk diffusion method and MIC determination for ciprofloxacin and azithromycin was done using the E-test (Biomerieux, France). Interpretation for ciprofloxacin was done using CLSI 2012 guidelines. Azithromycin MIC's were reported.

We had 251 S.typhi and 92 S.paratyphi A isolates. Both the serotypes had 100% susceptibility to chloramphenicol, cotrimoxazole, and ceftriaxone. A high rate of nalidixic acid resistance was seen, 94% for S. typhi and 96% for S .paratyphi A. Susceptibility pattern of ciprofloxacin revealed that 85% of S. typhi and 73% of S. paratyphi A were in the intermediate or resistant category [Figure 1].

There were two isolates which were sensitive to nalidixic acid but moderately sensitive to ciprofloxacin as per the MIC's. Though nalidixic acid is a reliable surrogate marker of fluoroquinolone resistance, it may not detect all mechanisms of resistance; MIC testing is also necessary.

Currently, azithromycin is increasingly being used for the management of enteric fever. However, there are no CLSI guidelines for azithromycin; clinical breakpoints are yet to be defined. It is recommended that MIC of ≤16 μg/ml is to be taken as the epidemiological cut off for wild type Salmonella. [3] In our isolates, azithromycin MIC's ranged from 0.125 to 6 μg/ml [Figure 2].{Figure 1}{Figure 2}

We did not have any multidrug resistant isolates. Fluoroquinolones are no longer useful for the treatment of enteric fever. Third generation cephalosporins continue to be an effective therapeutic option. Azithromycin also looks promising. The recent reports of emergence of ceftriaxone and azithromycin resistance are a serious concern. [4],[5] Studies investigating azithromycin resistance mechanisms in Salmonella are scarce. Moreover, as azithromycin use increases for the management of Salmonellosis, it is necessary to analyze the MIC distribution and appropriately formulate treatment strategies.


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3Sjölund-Karlsson M, Joyce K, Blickenstaff K, Ball T, Haro J, Medalla FM, et al. Antimicrobial Susceptibility to azithromycin among Salmonella enterica isolates from the United States. Antimicrob Agents Chemother 2011;55:3985-9.
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