In 2012, blood, skin and
soft tissue infections caused by
clindamycin resistant Streptococcus pyogenes (group A streptococcus; GAS) appeared to be increasing in the Helsinki metropolitan area. We compared monthly percentages of
clindamycin resistant isolates in the area between 2012 and 2013, with those in 2010 and 2011. Resistance frequency in terms of patient age was also studied. We reviewed the medical records of bacteraemic cases in 2012 and 2013 and linked the data to emm types. To inform on the emm distribution among GAS isolated from skin and
soft tissue infections during the epidemic, GAS isolates of one month (March 2013) were emm typed. For GAS blood, skin, and soft tissue isolates taken together, the proportions of
clindamycin resistant isolates were significantly higher in 2012 and 2013 (23% and 17%, respectively) compared with the two previous years (3%, p<0,001). The
erythromycin resistance percentages were almost equal to
clindamycin (22% and 17%) in 2012 and 2013, respectively.
Clindamycin resistance was most frequent in GAS isolates of 40 to 60 year-old patients (148/417; 36%). Among
clindamycin resistant isolates, 12 of 14 blood isolates from 2012 to 2013, and 11 of 13 skin and soft tissue isolates from March 2013, were emm33. Emm33 GAS bacteraemia was associated with
clindamycin and
erythromycin resistance (odds ratio (OR): 7.0; 95% confidence interval (CI): 1.9-25.3).
Infection focus was mainly the skin; either
cellulitis (7/12) or necrotising
fasciitis (3/12). All emm33 GAS isolates harboured the ermTR resistance gene with constitutive
macrolides,
lincosamides and streptogramines B (MLS(B)) phenotype. Emm33 GAS was responsible for the higher proportion of
clindamycin resistance in skin, soft tissue, and blood isolates locally in 2012 and 2013.