Beta-hemolytic Strep Osteoarticular Infections Increasing

Incidence of osteoarticular infections caused by group C and G streptococci (GCGS) are on the rise in patients 67 years of age or older, according to research published in BMC Infectious Diseases.

Oddvar Oppegaard, MD, of the department of medicine at Haukeland University Hospital and the department of clinical science at the University of Bergen in Bergen, Norway, and colleagues conducted a retrospective study of microbiologically verified cases of β-hemolytic streptococcal osteoarticular infections. Cases were identified between 1999 and 2003 at Health Region Bergen, Western Norway, consisting of a tertiary care hospital and 2 secondary care hospitals.

Osteoarticular infections included native joint infections (NJI), prosthetic joint infections (PJI), and acute osteomyelitis (AOM). Patients who presented with chronic osteomyelitis or concurrent endocarditis were excluded from the review.

Over a 15-year survey period, researchers identified 24 group A streptococci (GAS), 45 group B streptococci (GBS), and 42 group C and G streptococci (GCGS) acute osteoarticular infections—representing 8%, 13%, and 20% of all invasive episodes. 

Cumulative incidence of GCGS osteoarticular infections increased significantly from the first to last 5-year period (incidence rate ratio [IRR] 5.7, P =.0003); annual incidence peaked at 1.9/100,000 during 2013. 

GAS and GBS osteoarticluar infections did not create any significant trends, but remained stable at 0.5/100,000 (IRR 1.27, P =.63) and 0.8/100,000 (IRR 1.77, P =.14), respectively.

Seasonal variation was noted in all 3 groups; GAS peaked between December and February (38% of cases), while GBS and GCGS typically presented during the summer months (31% of cases).

Most patients with GAS, GBS, and GCGS were treated with a combination of surgery and antibiotics; 90% of cases were treated with penicillin, while the remaining cases were treated with clindamycin or cephalosporins. 

Between 10% and 20% of patients experienced a recurring infection—defined as clinical deterioration after cessation of antibiotic treatment, resulting in  new medical or surgical intervention—within 3 months.

The researchers found that both GBS and GCGS were “significantly associated with the presence of comorbidity and risk factors,” with GBS linked to systemic comorbidities (diabetes, chronic organ failure, active malignancy, immunosuppressants, or active intravenous drug use) and GCGS linked to factors of local origin (rheumatic joint disease, prior septic arthritis, prosthesis, or surgical joint procedure <4 weeks prior).

“We found a significantly increasing incidence of GCGS [osteoarticular infections], likely related to the presence of host susceptibility factors, including prosthetic material and pre-existing joint disease,” Dr Oppegaard and colleagues concluded. “With an increasing application of therapeutic and diagnostic bone and joint procedures, the rising trend of [osteoarticular infections] caused by GCGS is likely to continue.”

Limitations and Disclosures

• The retrospective design increases the risk of diagnostic misclassification
• Total incidence and characteristics of osteoarticular infections in the region were not available; a more comprehensive comparison of clinical features of streptococcal osteoarticular infection and osteoarticular infection caused by other bacteria was not feasible.
• The study applied to former definition of sepsis, rather than the current redefined definition, to allow for better comparison with existing literature.

The authors declare no competing interests.

Reference

1. Oppegaard O, Skrede S, Mylvaganam H, Kittang BR. Temporal trends of β-haemolytic streptococcal osteoarticular infections in western Norway. BMC Infect Dis. 2016;16:535. doi: 10.1186/s12879-016-0874-7

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