Population of invasive group A streptococci isolates from a German tertiary care center is dominated by the hypertoxigenic virulent M1UK genotype.

PURPOSE: Hypertoxigenic Streptococcus pyogenes emm1 lineage M1UK has recently been associated with upsurges of invasive infections and scarlet fever in several countries, but whole-genome sequencing surveillance data of lineages circulating in Germany is lacking. In this study, we investigated recent iGAS isolates from our laboratory at a German tertiary care center for the presence of the M1UK lineage. METHODS: Whole-genome sequencing was employed to characterize a collection of 47 consecutive non-copy isolates recovered from blood cultures (21) and tissue samples (26) in our laboratory between October 2022 and April 2023. RESULTS: M protein gene (emm) typing distinguished 14 different emm types, with emm1 (17) being the dominant type. Single-nucleotide polymorphism (SNP) analysis confirmed the presence of all 27 SNPs characteristic for the M1UK lineage in 14 of 17 emm1 isolates. CONCLUSION: This study has shown for the first time that M1UK is present in Germany and might constitute a driving force in the observed surge of GAS infections. This observation mirrors developments in the UK and other countries and underscores the importance of WGS surveillance to understand the epidemiology of GAS.

Evaluation of a rapid combination disc test (RCDT) for direct phenotypic detection of extended-spectrum ß-lactamase production in E. coli from positive blood culture bottles.

BACKGROUND: The spread of multi-resistant bacteria endangers the effectiveness of empirical antimicrobial treatment, particularly in Gram-negative bloodstream infections. Thus, rapid and reliable susceptibility testing has become a key challenge of modern microbiology. Here, we evaluated a combination disc test for rapid detection of ESBL production in Escherichia coli (rapid combination disc test, RCDT) directly from blood cultures. METHODS: RCDT with discs containing cefotaxime and ceftazidime alone or in combination with clavulanic acid was validated using a cryo-collection of 96 third-generation cephalosporin-resistant (3GCR), whole-genome sequenced E. coli isolates spiked into blood culture bottles. All isolates were subjected to RCDT and rapid antibiotic susceptibility testing (RAST). Zone diameters were assessed after 4, 6 and 8 h of incubation. All isolates also underwent conventional combination disc testing. The real-life performance of RCDT was assessed by analysis of 306 blood cultures growing E. coli. RESULTS: Eighty of 90 (88.9%) ESBL-positive E. coli validation isolates were correctly identified by RCDT after 4 h of incubation. The detection rate increased to 100% after 6 and 8 h. RCDT was negative in six 3GCR E. coli isolates expressing class B or C ß-lactamases. RCDT from routine blood cultures correctly classified all 56 ESBL producers and 245/250 ESBL-negative isolates after 4 h, resulting in 100% sensitivity and 98.8% specificity. CONCLUSIONS: RCDT is a reliable method for rapid ESBL detection in E. coli directly from positive blood cultures. RCDT might complement RAST to support antibiotic stewardship interventions and treatment decisions.

EUCAST rapid antimicrobial susceptibility testing (RAST): analytical performance and impact on patient management.

BACKGROUND: The emergence of antibiotic-resistant species calls for fast and reliable phenotypic susceptibility testing to adapt clinical management as fast as possible. OBJECTIVES: We assessed the real-life performance of EUCAST rapid antimicrobial susceptibility testing (RAST) and analysed its impact on patient management. METHODS: RAST was performed on clinical blood cultures containing Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa or Acinetobacter baumannii complex. Categorical agreement with VITEK2 was analysed. A pre-post quasi-experimental observational study was designed to compare antibiotic treatment in sepsis patients in the RAST patient group (n = 51) and a historical control cohort (n = 54). RESULTS: In total, 436 isolates, corresponding to 2314 disc diameters, were measured; 18.4% of these measurements were in the area of technical uncertainty. For the 81.6% categorical results, which could be compared, 94.7% were in agreement, whereas 5.3% of the results were not. In the RAST group, optimal therapy was initiated on the same day as blood culture positivity, while this was the case in the historical group after 24 h. In six cases, RAST allowed for rapid antibiotic escalation. The 30 day mortality rate was lower in the RAST group, although this was not statistically significant. CONCLUSIONS: RAST provides a reliable tool to improve clinical management of sepsis patients by providing rapid phenotypic susceptibility data. While not necessarily being an instrument for de-escalation, especially in areas of low prevalence, early detection allows for timely coverage of resistant isolates. Thus, RAST significantly adds to successful antibiotic stewardship programmes.