Inter-laboratory variability of caspofungin MICs for Nakaseomyces glabrata isolates - an Irish tertiary hospital experience.

Background: Nakaseomyces glabrata, formerly Candida glabrata, is an opportunistic yeast and emerging cause of human infections. The use of broth microdilution (BMD) methodologies for caspofungin (CSP) antifungal susceptibility testing (AFST) against N. glabrata is reported to be prone to high inter-laboratory variation. We aimed to compare CSP MICs of N. glabrata isolates from our institution with those obtained by the Reference Laboratory for the same isolates. Methods: All clinically significant N. glabrata isolates from 2019 to 2021 inclusive were reviewed. AFST was performed locally using the VITEK2 system with the AST-YS08 card, while E-tests were performed at the Mycology Reference Laboratory (MRL), and agreement between these two methods was evaluated - categorical and essential. Results: Forty-one isolates were reviewed during the study period - 30 from blood cultures, seven from intra-operative theatre specimens and four from sterile site drain fluids. Despite an essential agreement of 100 % within ±2 log2 dilutions, marked discrepancies were noted in interpretative breakpoints between assays with 17 Minor and 16 Major category errors. Categorical agreement was 19.5 %, with the VITEK2 over-estimating resistance. A Mann-Whitney U-test assessed the relationship of MICs across the AFST modalities, and a statistically significant difference was noted, P<0.01, with a higher mean rank for VITKEK2 outputs. Conclusion: While the VITEK2 system is highly applicable, its performance for CSP AFST is unreliable and potentially results in the mis-classification of susceptible isolates as highlighted in our study. The use of VITEK2 AST-YS08 micafungin as a sentinel echinocandin should be explored and/or the evaluation of CSP-specific E-tests as utilized by the MRL. These methods appear more consistent and less prone to the variation seen with BMD for CSP.

Impact of the COVID-19 pandemic on the incidence of healthcare-associated Clostridioides difficile infection in a tertiary healthcare facility in the Republic of Ireland.

Background: Clostridioides difficile is the foremost cause of nosocomial infectious diarrhoea and one of the most prevalent healthcare associated infections (HAIs). Aims: To investigate the impact of the coronavirus disease 2019 (COVID-19) pandemic on the incidence of healthcare associated C. difficile infection (HA-CDI). Methods: A retrospective study was conducted from January 2019-December 2022 inclusive at a tertiary University Hospital in Dublin, Ireland. The study period was divided into COVID-19 and non-COVID-19 periods determined in tangent with the then national incidences of COVID-19 and number of hospitalized patients with COVID-19. Analyses looked at quantity of testing performed, incidence rates and antimicrobial consumption. An independent samples t-test was used to determine significance between groups. Results: Between COVID-19 and non-COVID-19 periods, no statistically significant difference was observed among HA-CDI rates per 10,000 bed-days (2.1 cases vs 1.76 cases; P=0.34), consumption of defined daily doses per 100 bed-days of antimicrobials - all antimicrobials (83.36 vs 89.5; P=0.091), fluoroquinolones only (3.71 vs 4.46; P=0.067), third-generation cephalosporins only (4.17 vs 4.43; P=0.449), carbapenems only (3.28 vs 3.26; P=0.944) - or the number of C. difficile tests performed per 10,000 bed-days (321.81 tests vs 326.63 tests; P=0.696). Conclusions: There was no difference in the incidence rates of HA-CDI between COVID-19 and non-COVID-19 periods at our institution.

Establishing severe acute respiratory infection (SARI) surveillance in a sentinel hospital, Ireland, 2021 to 2022.

BackgroundIn 2020, due to the COVID-19 pandemic, the European Centre for Disease Prevention and Control (ECDC) accelerated development of European-level severe acute respiratory infection (SARI) surveillance.AimWe aimed to establish SARI surveillance in one Irish hospital as part of a European network E-SARI-NET.MethodsWe used routine emergency department records to identify cases in one adult acute hospital. The SARI case definition was adapted from the ECDC clinical criteria for a possible COVID-19 case. Clinical data were collected using an online questionnaire. Cases were tested for SARS-CoV-2, influenza and respiratory syncytial virus (RSV), including whole genome sequencing (WGS) on SARS-CoV-2 RNA-positive samples and viral characterisation/sequencing on influenza RNA-positive samples. Descriptive analysis was conducted for SARI cases hospitalised between July 2021 and April 2022.ResultsOverall, we identified 437 SARI cases, the incidence ranged from two to 28 cases per week (0.7-9.2/100,000 hospital catchment population). Of 431 cases tested for SARS-CoV-2 RNA, 226 (52%) were positive. Of 349 (80%) cases tested for influenza and RSV RNA, 15 (4.3%) were positive for influenza and eight (2.3%) for RSV. Using WGS, we identified Delta- and Omicron-dominant periods. The resource-intensive nature of manual clinical data collection, specimen management and laboratory supply shortages for influenza and RSV testing were challenging.ConclusionWe successfully established SARI surveillance as part of E-SARI-NET. Expansion to additional sentinel sites is planned following formal evaluation of the existing system. SARI surveillance requires multidisciplinary collaboration, automated data collection where possible, and dedicated personnel resources, including for specimen management.

PCR-ribotype distribution of Clostridium difficile in Irish pigs.

Clostridium difficile is an important enteric pathogen in humans causing infections in the healthcare environment and the community. Carriage of C. difficile and C. difficile-related enterocolitis has been reported in piglets worldwide. The aim of this study was to investigate the rates of C. difficile isolation from pigs in Ireland. Faecal samples from piglet litters and sows were collected from six farms in 2015. The sows were non-diarrhoeal at the time of sampling. The diarrhoeal status of the piglets was unknown. C. difficile was isolated from 34/44 (77%) of piglet litter samples and from 33/156 (21%) of sow samples. The isolation rate in sows varied from 3 to 39% and in piglet litters from 72 to 86% depending on farm location. Toxin A and toxin B were present in 99% (66/67) of isolates; and binary toxin in 85% (57/67). Only PCR-ribotypes 078 (88%) and 193 (12%) were identified in piglets. Seven PCR-ribotypes were detected in sow C. difficile isolates: PCR-ribotypes 078 (67%), 050 (12%), 014/020 (6%), 015 (6%), 029 (3%), 035 (3%) and 193 (3%). This study shows that toxigenic C. difficile strains such as PCR-ribotype 078 can be commonly isolated from pigs at different geographical locations in Ireland. Since PCR-ribotype 078 is frequently found in humans in Ireland, this highlights the potential for interspecies transmission.

PCR ribotype prevalence and molecular basis of macrolide-lincosamide-streptogramin B (MLSB) and fluoroquinolone resistance in Irish clinical Clostridium difficile isolates.

BACKGROUND: Antimicrobial use is recognized as a risk factor for Clostridium difficile infection (CDI) and outbreaks. We studied the relationship between PCR ribotype, antimicrobial susceptibility and the genetic basis of resistance in response to exposure to antimicrobial agents. METHODS: C. difficile isolates were cultured from 133 CDI patients for whom recent antimicrobial drug exposure had been recorded. Isolates were ribotyped by PCR and assessed for their susceptibility to the macrolide-lincosamide-streptogramin B (MLS(B)) group of compounds (erythromycin and clindamycin) and fluoroquinolone antimicrobials (ciprofloxacin, levofloxacin and moxifloxacin). Where relevant, the genetic basis of resistance was determined. RESULTS: Prevalent ribotypes (including 027, 001 and 106) exhibited significantly greater antimicrobial resistance compared with ribotypes 078 and 014, among others. Clindamycin-resistant ribotype 078 was detected for the first time. Ribotypes 027 and 001 were more likely to exhibit MLS(B) resistance, a feature that was associated with the erm(B) gene. Exposure to MLS(B) or fluoroquinolone antimicrobial compounds in the 8 weeks prior to the onset of infection was not associated with specific genetic markers of resistance. Single amino acid substitutions in the A and B subunits of DNA gyrase were noted and were ribotype specific and linked to resistance to moxifloxacin. CONCLUSIONS: Resistance to MLS(B) and fluoroquinolone antimicrobial compounds is common among prevalent ribotypes of C. difficile. The genetic basis for antimicrobial resistance appears to be ribotype specific and conserved in the absence of recent antimicrobial selection pressure.