Epidemiology and genetic diversity of linezolid-resistant Enterococcus clinical isolates in Belgium from 2013 to 2021.

OBJECTIVES: Linezolid-resistant opportunistic human pathogens Enterococcus faecalis and Enterococcus faecium are emerging health threats as limited therapeutic options remain. The aim of this study was to investigate the epidemiology, resistance mechanisms, and genetic diversity of linezolid-resistant enterococci (LRE) isolated between 2013 and 2021 and received at the Belgian National Reference Centre (NRC) for Enterococci. METHODS: Linezolid susceptibility testing was performed upon request on 2458 submitted enterococci strains. Whole-genome sequencing was performed on all LRE strains. RESULTS: Seventy-eight LRE human isolates, of which 63 (81%) E. faecalis and 15 (19%) E. faecium strains, were submitted to the Belgian NRC for Enterococci. Of the linezolid-resistant E. faecalis strains, 97% harboured the optrA gene (56% wild-type pE349) and 3% the poxtA gene. Of the linezolid-resistant E. faecium strains, 54% harboured the G2576T point mutation in the V domain of the 23S rRNA genes, 23% the poxtA, and 23% the optrA gene. Furthermore, two E. faecium strains were identified with a combination of two resistance mechanisms ([i] optrA and poxtA, and [ii] cfr(B) and G2576T point mutation, respectively). Vancomycin resistance was observed in 15% (n = 12) of the LRE. ST480 (n = 42/63 typed strains, 67%) was the most frequently detected sequence type (ST) in linezolid-resistant E. faecalis strains, while ST203 (n = 5/15 typed strains, 33%) was the most frequently detected ST in linezolid-resistant E. faecium strains. CONCLUSIONS: E. faecalis isolates harbouring optrA were the predominant LRE in Belgium, with ST480 as the most prominent multilocus sequence typing. Linezolid resistance in E. faecium could be attributed to either chromosomal mutations or transferable resistance determinants.

One Health surveillance of colistin-resistant Enterobacterales in Belgium and the Netherlands between 2017 and 2019.

BACKGROUND: Colistin serves as the last line of defense against multidrug resistant Gram-negative bacterial infections in both human and veterinary medicine. This study aimed to investigate the occurrence and spread of colistin-resistant Enterobacterales (ColR-E) using a One Health approach in Belgium and in the Netherlands. METHODS: In a transnational research project, a total of 998 hospitalized patients, 1430 long-term care facility (LTCF) residents, 947 children attending day care centres, 1597 pigs and 1691 broilers were sampled for the presence of ColR-E in 2017 and 2018, followed by a second round twelve months later for hospitalized patients and animals. Colistin treatment incidence in livestock farms was used to determine the association between colistin use and resistance. Selective cultures and colistin minimum inhibitory concentrations (MIC) were employed to identify ColR-E. A combination of short-read and long-read sequencing was utilized to investigate the molecular characteristics of 562 colistin-resistant isolates. Core genome multi-locus sequence typing (cgMLST) was applied to examine potential transmission events. RESULTS: The presence of ColR-E was observed in all One Health sectors. In Dutch hospitalized patients, ColR-E proportions (11.3 and 11.8% in both measurements) were higher than in Belgian patients (4.4 and 7.9% in both measurements), while the occurrence of ColR-E in Belgian LTCF residents (10.2%) and children in day care centres (17.6%) was higher than in their Dutch counterparts (5.6% and 12.8%, respectively). Colistin use in pig farms was associated with the occurrence of colistin resistance. The percentage of pigs carrying ColR-E was 21.8 and 23.3% in Belgium and 14.6% and 8.9% in the Netherlands during both measurements. The proportion of broilers carrying ColR-E in the Netherlands (5.3 and 1.5%) was higher compared to Belgium (1.5 and 0.7%) in both measurements. mcr-harboring E. coli were detected in 17.4% (31/178) of the screened pigs from 7 Belgian pig farms. Concurrently, four human-related Enterobacter spp. isolates harbored mcr-9.1 and mcr-10 genes. The majority of colistin-resistant isolates (419/473, 88.6% E. coli; 126/166, 75.9% Klebsiella spp.; 50/75, 66.7% Enterobacter spp.) were susceptible to the critically important antibiotics (extended-spectrum cephalosporins, fluoroquinolones, carbapenems and aminoglycosides). Chromosomal colistin resistance mutations have been identified in globally prevalent high-risk clonal lineages, including E. coli ST131 (n = 17) and ST1193 (n = 4). Clonally related isolates were detected in different patients, healthy individuals and livestock animals of the same site suggesting local transmission. Clonal clustering of E. coli ST10 and K. pneumoniae ST45 was identified in different sites from both countries suggesting that these clones have the potential to spread colistin resistance through the human population or were acquired by exposure to a common (food) source. In pig farms, the continuous circulation of related isolates was observed over time. Inter-host transmission between humans and livestock animals was not detected. CONCLUSIONS: The findings of this study contribute to a broader understanding of ColR-E prevalence and the possible pathways of transmission, offering insights valuable to both academic research and public health policy development.

Clinical and molecular epidemiological features of critically ill patients with invasive group A Streptococcus infections: a Belgian multicenter case-series.

BACKGROUND: Recent alerts have highlighted an increase in group A streptococcal (GAS) infections since 2022 in Europe and the United States. Streptococcus pyogenes can cause limited skin or mucosal disease, but can also present as severe invasive disease necessitating critical care. We performed a multicenter retrospective study of patients with GAS infections recently admitted to Belgian intensive care units (ICUs) since January 2022. We describe patient characteristics and investigate the molecular epidemiology of the S. pyogenes strains involved. RESULTS: Between January 2022 and May 2023, a total of 86 cases (56 adults, 30 children) with GAS disease were admitted to critical care in the university hospitals of Leuven, Antwerp and Liège. We noted a strikingly high incidence of severe community-acquired pneumonia (sCAP) (45% of adults, 77% of children) complicated with empyema in 45% and 83% of adult and pediatric cases, respectively. Two-thirds of patients with S. pyogenes pneumonia had viral co-infection, with influenza (13 adults, 5 children) predominating. Other disease presentations included necrotizing fasciitis (23% of adults), other severe skin/soft tissue infections (16% of adults, 13% of children) and ear/nose/throat infections (13% of adults, 13% of children). Cardiogenic shock was frequent (36% of adults, 20% of children). Fifty-six patients (65%) had toxic shock syndrome. Organ support requirements were high and included invasive mechanical ventilation (77% of adults, 50% of children), renal replacement therapy (29% of adults, 3% of children) and extracorporeal membrane oxygenation (20% of adults, 7% of children). Mortality was 21% in adults and 3% in children. Genomic analysis of S. pyogenes strains from 55 out of 86 patients showed a predominance of emm1 strains (73%), with a replacement of the M1global lineage by the toxigenic M1UK lineage (83% of emm1 strains were M1UK). CONCLUSIONS: The recent rise of severe GAS infections (2022-23) is associated with introduction of the M1UK lineage in Belgium, but other factors may be at play-including intense circulation of respiratory viruses and potentially an immune debt after the COVID pandemic. Importantly, critical care physicians should include S. pyogenes as causative pathogen in the differential diagnosis of sCAP.