Indian Journal of Pathology and Microbiology

: 2015  |  Volume : 58  |  Issue : 1  |  Page : 129--130

Distribution of Salmonella Typhi phage types from Pondicherry, India

Sreenivasan Srirangaraj, Arunava Kali, Marie Victor Pravin Charles 
 Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Puducherry, India

Correspondence Address:
Dr. Sreenivasan Srirangaraj
Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Pondicherry - 607 402

How to cite this article:
Srirangaraj S, Kali A, Pravin Charles MV. Distribution of Salmonella Typhi phage types from Pondicherry, India.Indian J Pathol Microbiol 2015;58:129-130

How to cite this URL:
Srirangaraj S, Kali A, Pravin Charles MV. Distribution of Salmonella Typhi phage types from Pondicherry, India. Indian J Pathol Microbiol [serial online] 2015 [cited 2020 May 25 ];58:129-130
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Typhoid fever is an important health problem in tropical countries with India contributing to a large portion of the annual disease burden. Phage typing is a good epidemiological marker for use in laboratories in developing countries, where infrastructure for molecular typing does not exist. The present communication reports the distribution of biotype and phage types of Salmonella enterica serotype Typhi (S. Typhi) strains and looks for correlation between antibiotic resistance and phage types.

A total of 16 S. Typhi strains was isolated from blood samples received at our laboratory over a period of 1½ years from January 2012 to June 2013. Standard methods were used to identify the S. Typhi isolates by biochemical tests and specific antisera (Central Research Institute, Kasauli, India). [1] Susceptibility testing was done using ampicillin (10 μg), co-trimoxazole (1.25/23.75 μg), ceftriaxone (30 μg), chloramphenicol (30 μg), nalidixic acid (30 μg), ciprofloxacin (5 μg), and azithromycin (15 μg) (Hi-Media, Mumbai, India), by Kirby-Bauer's disc diffusion method. Escherichia coli ATCC 25922 was used as control for the disc diffusion testing. [2]

Thirteen of these 16 isolates (three were lost on subculture) were sent to the National Salmonella Phage Typing Centre at Lady Hardinge Medical College, New Delhi for phage typing and biotyping. Biotyping was done by xylose fermentation. Xylose positive strains were grouped as the biotype I and negative ones as biotype II. Data analysis was done using Statistical Package for Social Sciences version 16 (SPSS Inc., Chicago, USA) and included calculation of percentages and determining correlation between antibiotic susceptibility and phage type.

All the S. Typhi isolates identified (n = 13, 100%) belonged to biotype I. Eight (61.54%) of these isolates from our study belonged to E1 phage type and the rest (n = 5, 38.46%) to untypable Vi strains (UVS).

We have already published the antibiogram of these isolates. [2] [Table 1] shows the resistance pattern of S. Typhi isolates along with phage types. There were no correlations observed between antimicrobial resistance patterns and phage types in the tested S. Typhi strains in our study (two-tailed significance for ampicillin, ciprofloxacin, and azithromycin were 0.423, 0.213, and 0.619, respectively, not significant).{Table 1}

In a study from eastern India (Kolkata), phage type E1 (60.3%) and biotype I (95%) was found to be the most common phage type. [3] In an earlier study from Pondicherry, S. Typhi phage typing was done for 123 isolates and 115 (93.5%) were found to be of phage type E1, biotype I. [4] A recent study from Chennai also showed E1 phage type (n = 17, 81%) and biotype I to be most prevalent. [5]

However, the interesting feature in our study was the identification of a significant percentage of UVS strains (38.46%). A study from Vietnam had identified UVS (54.1%) to be the predominant circulating phage type. [6] In contrast, earlier studies from Pondicherry (0.81%) and Kolkata (7.8%) demonstrated a small percentage of UVS isolates. [3],[4] However, in a more recent study from Chennai, UVS accounted for 19.1% of S. Typhi isolates. [5]

No correlation was found in our study correlating phage type and antimicrobial resistance. This could be due to the smaller sample size in our study. However, similar findings were reported from larger studies from Vietnam (n = 111). [6] In contrast, a study from Kolkata concurred most of the multidrug-resistant S. Typhi isolates belonged to the phage type E1 and biotype I. [3] But, this needs to be further probed through multicentric studies.

In conclusion, S. Typhi E1 phage type and biotype I continue to be the predominant circulating phage type from Pondicherry, though there is a significant increase in the isolation of non-typable UVS strains. There is no correlation between antimicrobial resistance patterns and phage types in the tested strains from our study.


The authors thank Dr. V. S. Randhawa, Director Prof. and Head, Department of Microbiology, Lady Hardinge Medical College, National Salmonella Phage Typing Centre, New Delhi, for performing phage typing of our S. Typhi isolates.


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