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Indian Journal of Microbiology Research

Short term conservation of human pathogenic Escherichia coli isolates in Phosphate Buffer Saline (PBS): An effective & economical method

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Research Article

Author Details : Riyaz Sheriff*, Lakshmi Sarayu, Prasobh K K, Neena A, Simi N

Volume : 6, Issue : 4, Year : 2019

Article Page : 308-312

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Introduction: Many different methods of bacterial conservation techniques have been used. Most of them
require technical excellence andare costly. Thus a simpler cost effective technique has been evaluated using
phosphate buffer saline (PBS).
Materials and Methods: 135 isolates were collected during the study period. The isolates were
subcultured on 5% sheep blood agar and incubated at 37?C for 18-24 hours. After incubation, isolates
were inoculated into autoclaved Phosphate Buffered Saline (PBS) in a Labelled screw capped vial. The
vials were incubated at 37?C overnight. Standardized protocols were followed for antibiotic sensitivity
testing. The isolates were analyzed for their sensitivity to Ampicillin, Gentamicin, Tobramycin, Amikacin,
Ciprofloxacin, Levofloxacin, Cotrimoxazole, Amox-Clavulanate, Piperacillin Tazobactum, Norfloxacin,
Amikacin, Ceftriaxone, Ceftazidime, Ceftazidime-Clavulanic Acid, Cefotaxime, Imipenam, Tetracycline
& Nitrofurantoin. Baseline Minimum Inhibitory Concentration (MIC) of Ceftazidime was done using
the Epsilometer test (E-test). The vials were stored at room temperature inside a thermocol box to avoid
exposure to sunlight. Subcultures from distilled water were done to look for ability to grow, reduction
in colony counts and for checking the purity of the isolate. Six monthly MIC using E-test was done and
compared with baseline values.
Results: Out of the 135 samples, 6 isolates did not grow on subcultures. 10 isolates were contaminated.
119 isolates showed good growth till the end of 12 months study period. The Minimum Inhibitory
Concentration (MIC) did not alter from the baseline MIC.
Conclusion: This method is inexpensive, technically simple method of bacterial conservation and is ideal
for short term storage. This method will prove to be useful for young researchers, Post graduate students
and even in Microbiology labs with minimal facilities.

Keywords: Antibiogram, Bacterial preservation, Escherichia coli, Minimum inhibitory Concentration, Phosphate buffer saline, Water conservation.

Doi : 10.18231/j.ijmr.2019.066

How to cite : Sheriff R, Sarayu L, Prasobh K K, Neena A, Simi N, Short term conservation of human pathogenic Escherichia coli isolates in Phosphate Buffer Saline (PBS): An effective & economical method. Indian J Microbiol Res 2019;6(4):308-312

Copyright © 2019 by author(s) and Indian J Microbiol Res. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (CC-BY-NC 4.0) (