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Bacteriological diagnosis of β-hemolytic streptococci of the upper respiratory tract


Beta-hemolytic streptococci are major human pathogens associated with local or systemic invasion and post-streptococcal immune disorders. We performed a comparison between bacitracin and latex agglutination test for the identification of beta-hemolytic streptococci. We assessed resistance patterns to erythromycin/clindamycin.


Between January 1 2014 – July 15 2014, 5038 throat swabs were sampled from patients hospitalized in INBI Matei Balş according to standard methods. All beta-hemolytic streptococci suspected colonies were tested with bacitracin (0.04%) disks and we used the latex agglutination kit Omega Latex Diagnostic Avipath Strep. Erythromycin resistance testing was performed by disc 2μg Oxoid and clindamycin 2μg Oxoid on the blood M-H medium.


There were 460 isolates of beta-hemolytic streptococci, bacitracin test was positive for 373 (92.75%). From 87 negative bacitracin test left streptococci, with latex agglutination test, 18 (20.68%) were identified as Streptococcus pyogenes (group A) and 69 (79.32%) were group C, G, B, F. Streptococcus pyogenes had 8.95% resistance to erythromycin, group C streptococci had 2.12%, and group G 45.45. From strains with resistance to erythromycin 75.6% were with inducible resistance to clindamycin and 17.07% had a constitutive one.


Latex agglutination is a preferable alternative to bacitracin testing, providing a definite grouping result.

Resistance of Streptococcus pyogenes to erythromycin was 8.95% compared with group G which had a resistance of 45.45%.

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Correspondence to Alina Borcan.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Borcan, A., Dorobăț, O., Bădicuț, I. et al. Bacteriological diagnosis of β-hemolytic streptococci of the upper respiratory tract. BMC Infect Dis 14 (Suppl 7), P9 (2014).

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