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Year : 2014  |  Volume : 32  |  Issue : 4  |  Page : 465--466

Azithromycin zone interpretation for Salmonella: Time to Adopt BSAC's zone diameters?

S Rai 
 Department of Microbiology, University College of Medical Sciences and Guru Teg Bahadur Hospital, Delhi, India

Correspondence Address:
S Rai
Department of Microbiology, University College of Medical Sciences and Guru Teg Bahadur Hospital, Delhi
India

How to cite this article:
Rai S. Azithromycin zone interpretation for Salmonella: Time to Adopt BSAC's zone diameters? .Indian J Med Microbiol 2014;32:465-466

How to cite this URL:
Rai S. Azithromycin zone interpretation for Salmonella: Time to Adopt BSAC's zone diameters? . Indian J Med Microbiol [serial online] 2014 [cited 2020 Nov 26 ];32:465-466
Available from: https://www.ijmm.org/text.asp?2014/32/4/465/142240

Full Text

Dear Editor,

Clinical and Laboratory Standards Institutes (CLSI) does not mention breakpoint zone diameters or minimum inhibitory concentration (MIC) values for drugs like azithromycin and tigecycline against any member of family Enterobacteriaceae, therefore it is not possible to use M-100 S-22 document for zone interpretation for these antibiotics as used in the article published by Garg et al. [1],[2] The  British Society for Antimicrobial Chemotherapy (BSAC's) 2012 document nevertheless provides a zone diameter of ≤18 mm as resistant and ≥19 mm as resistant for a 15-μg azithromycin disc. [3] Even though, MIC breakpoints for azithromycin are not mentioned in this document, it has been stated that azithromycin has been used in the treatment of infections with Salmonella Typhi (MIC ≤16 mg/L for wild-type isolates) and some enteric infections. These breakpoints were unavailable before 2012, and therefore it was difficult for bacteriology laboratories to interpret results for azithromycin. With reference to the study published by Garg et al., in the previous issue, the MIC 90 value for azithromycin is not clear. [1] Among the 42 Salmonella isolates in their study, the MIC 90 would be that of the 38 th isolate in increasing order of MIC's, that is, 12 μg/mL, as per Garg et al., [Table 2]. [1] The MIC 90 in the study cited by them was twice the value (24 μg/mL) than their study. [4] However, the present authors have also augmented antibiotic recycling practices for treatment of enteric fever. Corroboration between both studies justifies cautious use of azithromycin for enteric fever in India and not to blindly follow its Western prescribing practices. With cautious use of azithromycin in S. Typhi in India and emergence of carbapenem-resistant Enterobacteriaceae, for which tigecycline is an effective drug, is it time to adopt BSAC zones for these two drugs?

References

1Garg A, Verma S, Kanga A, Singh D, Singh B. Antimicrobial resistance pattern and in vivo activity of azithromycin in Salmonella isolates. Indian J Med Microbiol 2013;31:287-9.
2Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing, 22 nd Informational Supplement. Approved Standard. 22 nd ed. CLSI Document M 100-S22. Wayne: CLSI; 2012.
3British Standards for antimicrobial Chemotherapy. BSAC Methods for Antimicrobial Susceptibility Testing. Version 11.1. Approved Standard. Version 11.1 BSAC Document;  2012.
4Rai 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.