Bacteraemia caused by beta-haemolytic streptococci in North Queensland: changing trends over a 14-year period

Abstract

Group A streptococci (GAS) are usually the predominant species in cases of bacteraemia caused by β haemolytic streptococci (BHS). An increasing worldwide incidence of invasive disease from non-group A BHS has been reported. Little is known about the changing trends in invasive disease caused by BHS in Australia. North Queensland has a relatively large indigenous population, who experience significantly higher rates of group A-related disease than the non-indigenous population. This prospective study examined changing trends of disease from large colony BHS that group with A, B, C and G antisera over a 14-year period at the single large tertiary referral hospital in the area. We identified 392 bacteraemic episodes caused by BHS. GAS were most commonly isolated (49%), with adjusted rates remaining stable over the period. There was a significant increase in the incidence of non-neonatal bacteraemia caused by group B streptococci (GBS) over the study period (r = 0.58; p 0.030), largely driven by infection in older, non-indigenous women. Rates of bacteraemia caused by group C streptococci also experienced a modest, but significant, increase over time (r = 0.67; p 0.009). GAS, which had no predominant emm type, were seen most commonly in indigenous subjects (52%). Mortality rates ranged from 3.2% (group G) to 10.3% (group C), with a rate of 7.9% associated with group A disease. The marked rise in GBS disease has been noted worldwide, but the relatively low incidence in indigenous Australian patients has not been described before, despite the burden of wellrecognized risk factors for GBS disease within this group.