Characterisation of clinical manifestations and treatment strategies for invasive beta-haemolytic streptococcal infections in a Swiss tertiary hospital.

AIMS OF THE STUDY: Invasive streptococcal infections affect more than half a million patients worldwide every year and have a high lethality. Little is known about the epidemiology and microbiological characteristics of streptococcal infections in Switzerland. This case series study aims to describe the demographics, known risk factors for streptococcal skin and soft tissue infections, clinical presentations, treatment and outcomes of patients admitted to the University Hospital Zurich between 2000 and 2014 with invasive streptococcal infections caused by Streptococcus pyogenes (group A Streptococcus), Streptococcus dysgalactiae ssp. equisimilis or the Streptococcus anginosus group, as well as the microbiological characteristics of the clinical isolates. METHODS: Data collected retrospectively from patients hospitalised between 2000 and 2014 with invasive streptococcal infections were analysed. M protein gene (emm) typing of the bacterial clinical isolates was carried out according to the Centers for Disease Control and Prevention guidelines. RESULTS: A total of 86 patients with invasive beta-haemolytic streptococcal infections were included in this study, of which 49% presented with necrotising fasciitis (NF). The median age was 44 years and half were female. The most common risk factor was acute skin lesions. C-reactive protein levels were significantly higher in patients with NF, as were acute renal failure and distributive shock. Beta-lactam antibiotics were given to most patients, and intravenous immunoglobulins were given to 18% of patients within the first 24 hours. All patients suffering from NF underwent surgery. The overall case fatality rate was 8.1% at 30 days post admission. All Group A Streptococcus strains were susceptible to penicillin and clindamycin, and we found resistance to tetracycline in 11.9% of strains. The most common emm-type isolated was emm1 (44.4%). CONCLUSIONS: Invasive beta-haemolytic streptococcal infections, the most severe presentation of which is NF, remain a serious clinical issue and require rapid diagnosis and treatment. This is the first representative analysis monitoring clinical and microbiological characteristics of patients with a severe invasive beta-haemolytic streptococcal infection and treated in Zurich, Switzerland. In addition to the detailed reporting of various clinical and microbiological characteristics, we show that C-reactive protein levels, acute renal failure and distributive shock were higher in the patients with NF. We also found a low case fatality rate compared to other reports. The detailed clinical data and microbiological characteristics depicted in this study will lead to a better understanding of regional differences in severe invasive streptococcal infections.

Immunoglobulin Attenuates Streptokinase-Mediated Virulence in Streptococcus dysgalactiae Subspecies equisimilis Necrotizing Fasciitis.

Background: Necrotizing fasciitis (NF) retains a very high mortality rate despite prompt and adequate antibiotic treatment and surgical debridement. Necrotizing fasciitis has recently been associated with Streptococcus dysgalactiae subspecies equisimilis (SDSE). Methods: We investigated the causes of a very severe clinical manifestation of SDSE-NF by assessing both host and pathogen factors. Results: We found a lack of streptokinase-function blocking antibodies in the patient resulting in increased streptokinase-mediated fibrinolysis and bacterial spread. At the same time, the clinical SDSE isolate produced very high levels of streptokinase. Exogenous immunoglobulin Gs (ex-IgGs) efficiently blocked streptokinase-mediated fibrinolysis in vitro, indicating a protective role against the action of streptokinase. In vivo, SDSE infection severity was also attenuated by ex-IgGs in a NF mouse model. Conclusions: These findings illustrate for the first time that the lack of specific antibodies against streptococcal virulence factors, such as streptokinase, may contribute to NF disease severity. This can be counteracted by ex-IgGs.

Clindamycin Affects Group A Streptococcus Virulence Factors and Improves Clinical Outcome.

Group A Streptococcus (GAS) has acquired an arsenal of virulence factors, promoting life-threatening invasive infections such as necrotizing fasciitis. Current therapeutic regimens for necrotizing fasciitis include surgical debridement and treatment with cell wall-active antibiotics. Addition of clindamycin (CLI) is recommended, although clinical evidence is lacking. Reflecting the current clinical dilemma, an observational study showed that only 63% of the patients with severe invasive GAS infection received CLI. This work thus aimed to address whether CLI improves necrotizing fasciitis outcome by modulating virulence factors of CLI-susceptible and CLI-resistant GAS in vitro and in vivo. Treatment with CLI reduced extracellular DNase Sda1 and streptolysin O (SLO) activity in vivo, whereas subinhibitory CLI concentrations induced expression and activity of SLO, DNase, and Streptococcus pyogenes cell envelope protease in vitro. Our in vivo results suggest that CLI should be administered as soon as possible to patients with necrotizing fasciitis, while our in vitro studies emphasize that a high dosage of CLI is essential.