One Day in Denmark: Comparison of Phenotypic and Genotypic Antimicrobial Susceptibility Testing in Bacterial Isolates From Clinical Settings.

Antimicrobial susceptibility testing (AST) should be fast and accurate, leading to proper interventions and therapeutic success. Clinical microbiology laboratories rely on phenotypic methods, but the continuous improvement and decrease in the cost of whole-genome sequencing (WGS) technologies make them an attractive alternative. Studies evaluating the performance of WGS-based prediction of antimicrobial resistance (AMR) for selected bacterial species have shown promising results. There are, however, significant gaps in the literature evaluating the applicability of WGS as a diagnostics method in real-life clinical settings against the range of bacterial pathogens experienced there. Thus, we compared standard phenotypic AST results with WGS-based predictions of AMR profiles in bacterial isolates without preselection of defined species, to evaluate the applicability of WGS as a diagnostics method in clinical settings. We collected all bacterial isolates processed by all Danish Clinical Microbiology Laboratories in 1 day. We randomly selected 500 isolates without any preselection of species. We performed AST through standard broth microdilution (BMD) for 488 isolates (n = 6,487 phenotypic AST results) and compared results with in silico antibiograms obtained through WGS (Illumina NextSeq) followed by bioinformatics analyses using ResFinder 4.0 (n = 5,229 comparisons). A higher proportion of AMR was observed for Gram-negative bacteria (10.9%) than for Gram-positive bacteria (6.1%). Comparison of BMD with WGS data yielded a concordance of 91.7%, with discordant results mainly due to phenotypically susceptible isolates harboring genetic AMR determinants. These cases correspond to 6.2% of all isolate-antimicrobial combinations analyzed and to 6.8% of all phenotypically susceptible combinations. We detected fewer cases of phenotypically resistant isolates without any known genetic resistance mechanism, particularly 2.1% of all combinations analyzed, which corresponded to 26.4% of all detected phenotypic resistances. Most discordances were observed for specific combinations of species-antimicrobial: macrolides and tetracycline in streptococci, ciprofloxacin and ß-lactams in combination with ß-lactamase inhibitors in Enterobacterales, and most antimicrobials in Pseudomonas aeruginosa. WGS has the potential to be used for surveillance and routine clinical microbiology. However, in clinical microbiology settings and especially for certain species and antimicrobial agent combinations, further developments in AMR gene databases are needed to ensure higher concordance between in silico predictions and expected phenotypic AMR profiles.

One Day in Denmark: Nationwide point-prevalence survey of human bacterial isolates and comparison of classical and whole-genome sequence-based species identification methods.

OBJECTIVES: Implementing whole-genome sequencing (WGS) technologies in clinical microbiology laboratories can increase the amount and quality of information available for healthcare practitioners. In this study, we analysed the applicability of this method and determined the distribution of bacterial species processed in clinical settings in Denmark. METHODS: We performed a point-prevalence study of all bacterial isolates (n = 2,009) processed and reported in the Clinical Microbiology Laboratories in Denmark in one day in January 2018. We compared species identification as performed by classical methods (MALDI-TOF) and by bioinformatics analysis (KmerFinder and rMLST) of WGS (Illumina NextSeq) data. We compared the national point-prevalence of bacterial isolates observed in clinical settings with the research attention given to those same genera in scientific literature. RESULTS: The most prevalent bacterium was Escherichia coli isolated from urine (n = 646), followed by Staphylococcus spp. from skin or soft tissues (n = 197). The distribution of bacterial species throughout the country was not homogeneous. We observed concordance of species identification for all methods in 95.7% (n = 1,919) of isolates, furthermore obtaining concordance for 99.7% (n = 1,999) at genus level. The number of scientific publications in the country did not correlate with the number of bacterial isolates of each genera analysed in this study. CONCLUSIONS: WGS technologies have the potential to be applied in clinical settings for routine diagnostics purposes. This study also showed that bioinformatics databases should be continuously improved and results from local point-prevalence surveys should not be applied at national levels without previously determining possible regional variations.

Azole resistance in Aspergillus fumigatus. The first 2-year's Data from the Danish National Surveillance Study, 2018-2020.

BACKGROUND: Azole resistance complicates treatment of patients with invasive aspergillosis with an increased mortality. Azole resistance in Aspergillus fumigatus is a growing problem and associated with human and environmental azole use. Denmark has a considerable and highly efficient agricultural sector. Following reports on environmental azole resistance in A. fumigatus from Danish patients, the ministry of health requested a prospective national surveillance of azole-resistant A. fumigatus and particularly that of environmental origin. OBJECTIVES: To present the data from the first 2 years of the surveillance programme. METHODS: Unique isolates regarded as clinically relevant and any A. fumigatus isolated on a preferred weekday (background samples) were included. EUCAST susceptibility testing was performed and azole-resistant isolates underwent cyp51A gene sequencing. RESULTS: The azole resistance prevalence was 6.1% (66/1083) at patient level. The TR34 /L98H prevalence was 3.6% (39/1083) and included the variants TR34 /L98H, TR34 3 /L98H and TR34 /L98H/S297T/F495I. Resistance caused by other Cyp51A variants accounted for 1.3% (14/1083) and included G54R, P216S, F219L, G54W, M220I, M220K, M220R, G432S, G448S and Y121F alterations. Non-Cyp51A-mediated resistance accounted for 1.2% (13/1083). Proportionally, TR34 /L98H, other Cyp51A variants and non-Cyp51A-mediated resistance accounted for 59.1% (39/66), 21.2% (14/66) and 19.7% (13/66), respectively, of all resistance. Azole resistance was detected in all five regions in Denmark, and TR34 /L98H specifically, in four of five regions during the surveillance period. CONCLUSION: The azole resistance prevalence does not lead to a change in the initial treatment of aspergillosis at this point, but causes concern and leads to therapeutic challenges in the affected patients.

Danish Whole-Genome-Sequenced Candida albicans and Candida glabrata Samples Fit into Globally Prevalent Clades.

Candida albicans and Candida glabrata are opportunistic fungal pathogens with increasing incidence worldwide and higher-than-expected prevalence in Denmark. We whole-genome sequenced yeast isolates collected from Danish Clinical Microbiology Laboratories to obtain an overview of the Candida population in the country. The majority of the 30 C. albicans isolates were found to belong to three globally prevalent clades, and, with one exception, the remaining isolates were also predicted to cluster with samples from other geographical locations. Similarly, most of the eight C. glabrata isolates were predicted to be prevalent subtypes. Antifungal susceptibility testing proved all C. albicans isolates to be susceptible to both azoles and echinocandins. Two C. glabrata isolates presented azole-resistant phenotypes, yet all were susceptible to echinocandins. There is no indication of causality between population structure and resistance phenotypes for either species.

Update 2016-2018 of the Nationwide Danish Fungaemia Surveillance Study: Epidemiologic Changes in a 15-Year Perspective.

As part of a national surveillance programme initiated in 2004, fungal blood isolates from 2016-2018 underwent species identification and EUCAST susceptibility testing. The epidemiology was described and compared to data from previous years. In 2016-2018, 1454 unique isolates were included. The fungaemia rate was 8.13/100,000 inhabitants compared to 8.64, 9.03, and 8.38 in 2004-2007, 2008-2011, and 2012-2015, respectively. Half of the cases (52.8%) involved patients 60-79 years old and the incidence was highest in males ≥70 years old. Candida albicans accounted for 42.1% of all isolates and Candida glabrata for 32.1%. C. albicans was more frequent in males (p = 0.03) and C. glabrata in females (p = 0.03). During the four periods, the proportion of C. albicans decreased (p < 0.001), and C. glabrata increased (p < 0.001). Consequently, fluconazole susceptibility gradually decreased from 68.5% to 59.0% (p < 0.001). Acquired fluconazole resistance was found in 4.6% Candida isolates in 2016-2018. Acquired echinocandin resistance increased during the four periods 0.0%, 0.6%, 1.7% to 1.5% (p < 0.0001). Sixteen echinocandin-resistant isolates from 2016-2018 harboured well-known FKS resistance-mutations and one echinocandin-resistant C. albicans had an FKS mutation outside the hotspot (P1354P/S) of unknown importance. In C. glabrata specifically, echinocandin resistance was detected in 12/460 (2.6%) in 2016-2018 whereas multidrug-class resistance was rare (1/460 isolates (0.2%)). Since the increase in incidence during 2004-2011, the incidence has stabilised. In contrast, the species distribution has changed gradually over the 15 years, with increased C. glabrata at the expense of C. albicans. The consequent decreased fluconazole susceptibility and the emergence of acquired echinocandin resistance complicates the management of fungaemia and calls for antifungal drug development.

Treatment of candidemia in a nationwide setting: increased survival with primary echinocandin treatment.

BACKGROUND: In accordance with international guidelines, primary antifungal treatment (AFT) of candidemia with echinocandins has been nationally recommended in Denmark since 2009. Our nationwide cohort study describes the management of candidemia treatment focusing on the impact of prophylactic AFT on species distribution, the rate of adherence to the recommended national guidelines for AFT, and the effect of AFT on patient outcomes. MATERIALS AND METHODS: Incident candidemia cases from a 2-year period, 2010-2011, were included. Information on AFT was retrospectively collected from patient charts. Vital status was obtained from the Danish Civil Registration System. HRs of mortality were reported with 95% CIs using Cox regression. RESULTS: A total of 841 candidemia patients was identified. Prior to candidemia diagnosis, 19.3% of patients received AFT (162/841). The risk of non-albicans candidemia increased after prior AFT (59.3% vs 45.5% among nontreated). Echinocandins as primary AFT were given for 44.2% (302/683) of patients. Primary treatment with echinocandins resulted in adequate treatment in a higher proportion of patients (97.7% vs 72.1%) and was associated with lower 0- to 14-day mortality compared with azole treatment (adj. HR 0.76, 95% CI: 0.55-1.06). Significantly lower 0- to 14-day mortality was observed for patients with Candida glabrata and Candida krusei with echinocandin treatment compared with azole treatment (adj. HR 0.50, 95% CI: 0.28-0.89), but not for patients with Candida albicans or Candida tropicalis. CONCLUSION: The association shown between prior AFT and non-albicans species underlines the importance of treatment history when selecting treatment for candidemia. Compliance with national recommendations was low, but similar to previously reported international rates. Primary treatment of candidemia with echinocandins compared with azoles yielded both a higher proportion of adequately treated patients and improved mortality rates. This real-life setting supports guidelines recommendation, and further focus on compliance with these seems warranted.