A Newer in Vitro Model for the Study of Development of in vitro resistance to penicillin in a novel isolate of Streptococcus tigurinus

Year 2017, Volume: 07 Issue: 04, 194 - 197, 01.12.2017

Shree Dhotre Basavraj Nagoba Milind Davane Mahesh Dharne Namdev Suryawanshi

https://doi.org/10.5799/jmid.368890

Abstract

Objectives: Streptococcus tigurinus is a new member of the Streptococcus mitis group. It
causes various invasive infections. Its isolation from the oral cavity has been
reported recently for the first time in our previous study. An attempt has been
made to develop a novel in vitro model for the study of development of
resistance to penicillin and to find out its effect on susceptibility pattern
of other antimicrobial agents in an isolate of S. tigurinus.

Materials and Methods: An in vitro model mimicking in vivo conditions was
developed to induce resistance in S.
tigurinus with MIC value of 0.12 µg/ml to penicillin by 10 serial passages
by sequential exposure to increasing concentration of penicillin.

Results: The
in vitro manipulation of original strain of S.
tigurinus resulted in an increase in MIC value to 8 µg/ml indicating
development of resistance to penicillin and a major increase in MIC value of
ampicillin from 0.25 to 16 µg/ml, and increase in MIC values of cefepime (0.12
to 0.25 µg/ml), erythromycin (0.12 to 0.25 µg/ml), azithromycin (0.5 to 1
µg/ml) and clarithromycin (0.25 to 0.5 µg/ml) indicating development of
cross-resistance to these antimicrobial agents.

Conclusion: Results indicate that
exposure to increasing concentrations of penicillin can induce the development
of resistance to penicillin and cross-resistance to other antimicrobial agents.
As in vitro conditions are quite similar to in vivo situation, the results
obtained are more appreciable than routine methods using artificial media. 

Keywords

Streptococcus tigurinus, in vitro resistance, cross-resistance, penicillin

References

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