7th joint conference "Joint Microbiology & Infection Conference 2024" of the DGHM and VAAM

PD Dr. med. habil.

Chair

Prof. Dr.

Healthcare-associated infections and pathogens: Prevention, surveillance, outbreaks und antibiotic stewardship 3

Dr. med.

It is time for genome-oriented management of outbreaks involving vancomycin-resistant enterococci – the different stories told by different levels of characterization

Healthcare-associated infections and pathogens: Prevention, surveillance, outbreaks und antibiotic stewardship

BackgroundGenome-oriented outbreak management (OM) is still uncommon in routine infection control. The strain dynamics of vancomycin-resistant Enterococcus faecium (VRE), however, often complicate the distinction between real- and pseudo-outbreaks. This project analyzes how the same outbreak situations unravel, and how high the efficiency of OM is, when using strain-typing methods with increasing resolution of genetic data.MethodsIn 2022, prolonged VRE outbreaks affected 47 patients at our oncology department. OM interventions were done twice (June and October), dividing the events into three phases. 47 isolates from 44 patients (including two isolates with different van-genotypes for three patients) were collected during January 2022-February 2023, and characterized using MALDI-ToF, in-house vanAB-PCR, and short-read whole-genome sequencing (WGS). Subsequently, the different levels of characterization were used to evaluate the outbreak dynamics and OM efficiency.ResultsEpidemiological data suggests that the VRE outbreak during Phase 1 was terminated by OM, whereas it did not affect Phase 2. While WGS confirmed a monoclonal outbreak of ST1299/CT1903/vanA during Phase 1, Phase 2 was caused by a polyclonal outbreak. ST1299/CT1903/vanA was also most common among VRE/vanA during Phase 2, and two isolates were closely related to isolates from Phase 1. The prolonged hospitalization of patients from Phase 1 appears to be the most probable reason. The remaining ST1299/CT1903/vanA isolates are split in two clusters, suggesting VRE introduction on two further occasions. Although clusters of VRE/vanB were also identified during Phase 2, these were small-sized. The spread of both VRE/vanA and VRE/vanB outbreak strains in Phase 2 was also promptly interrupted by OM according to WGS data and cgMLST. The outbreak suspicion in Phase 3 was not confirmed.ConclusionsOur genome-oriented approach to infection control clearly demonstrates that the success of OM for VRE is feasible, but can only be evaluated using WGS. Without this, the extent of clinical outbreaks can be grossly overestimated during routine investigations, whereas OM efficiency is falsely questioned.

Oral Presentation

PD. Dr.

Competition between vancomycin-resistant enterococci of different sequence types

IntroductionVancomycin-resistant enterococci (VRE) are multi-drug-resistant organisms that cause severe nosocomial infections. VRE of sequence types (ST) ST80 and ST117 experience an upcoming prevalence in screening and clinical isolates in Germany. Since this national increase cannot be explained by transmission events, we hypothesize that VRE of these STs either have selective advantages or harbor an increased virulence potential resulting in enhanced numbers of infections. This study aims at identifying ST-specific phenotypic differences of VRE and to investigate whether ST117 and ST80 VRE dominate VRE of other ST in vitro.Materials &amp; MethodsVRE isolated from patients of a tertiary care hospital in 2021-2023 were subjected to whole genome sequencing and compared using a core genome Multilocus Sequencing Typing (cgMLST) approach. Biofilm production was investigated by crystal violet assay. Competition of VRE with different STs was analyzed in a Spot Killing Assay.ResultsMost frequently, VRE of ST117 and ST80 but also rarer ST2032, ST2481 and ST18 were identified. VRE of ST117 and ST80 showed a significant higher biofilm production compared to ST2481 and ST18 (ST2481: p = 0.006; p = 0.0002; ST18: p = 0.001, p = 2.9x10-7, respectively). Only one of two ST2032 produced biofilm. Spot Killing Assays resulted in inhibited growth of ST2481 and ST18 VRE after spotting ST117 and ST80 VRE or their respective supernatants. SummaryIn this study, we identified two explanations for the current trend of increasing VRE STs 117 and 80 in Germany. ST117 and ST80 VRE strains and their supernatants lyse VRE of other STs in vitro, indicating a possible intra-host selective advantage. Additionally, biofilm production of these predominant STs is enhanced compared to others, probably facilitating survival of these strains in the patient environment.

PD. Dr. med.

Professor

Our first-time infection prevention and control experience with Candia auris at a burn intensive care unit

IntroductionCandida auris (Ca) is an increasing infectious disease and infection prevention and control (IPC) challenge in recent years [1]. Its potential to spread in hospitals is feared. We present the IPC management of a Ca positive patient in a burn intensive care unit (BICU).MaterialsWe describe the IPC measures which were inspired by existing recommendations [2]. We also highlight open aspects of IPC management that have arisen for us in practice.ResultsThe pre-hospitalised patient was transferred from Ukraine and admitted to the BICU. In accordance with internal IPC standards, the patient was pre-emptively isolated and a screening for multidrug-resistant bacteria took place. This revealed several carbapenem-resistant Gram-negative bacteria, VRE and MRSA. The patient was cared for under strict IPC standards including PPE for staff and 1:1 care whenever possible. On day 13 of the stay, Ca was detected in a wound material. Immediately, the patient and all other patients on the BICU were screened for Ca (nose/throat, axillae, groin, rectal, respiratory secretions, catheter urine, wounds; initially with regular malt extract agar). CHROMagar™ Candida Plus was introduced ad hoc in the microbiological laboratory. The ward contact patients were screened every 3 days initially and then once a week. Ward disinfection was enhanced and repeated on-site audits took place. After the Ca patient was not more on the ward long term follow-up screening was implemented. SummaryFor the first time, a patient with Ca was treated in our BICU. Due to close co-operation between the clinic, IPC and microbiology, comprehensive screening was quickly established. To date, no transmission has been detected, to which the pre-emptive isolation and the high IPC standards of the BICU have contributed. An important aspect is to clarify which groups should be screened for Ca on admission.References[1] Aldejohann AM et al. Rise in Candida Auris Cases and First Nosocomial Transmissions in Germany. doi: 10.3238/arztebl.m2023.0047[2] Aldejohann AM et al. Expert recommendations for prevention and management of Candida auris transmission. doi: 10.1111/myc.13445

Dr.med.

Prof. Dr.med.

Molecular typing of methicillin resistant Staphylococcus aureus (MRSA) in patients with mutual exposure reveals low proportion of transmission events.

Question: If patients with newly detected MRSA during their hospital stay had epidemiological exposure in the same room or on the same ward to other patients with hitherto unknown MRSA colonization, it is tempting to assume a transmission event. However, a previous unknown MRSA colonization could as well explain the above constellation, especially in a setting without universal screening on admission. Methods: Data on patient admission, transfer and discharge were linked with microbiological lab data in a Jupyter Notebook using common Python packages to determine pairs of patients with MRSA colonization that could possibly be explained by mutual exposure either in the same patient room or on the same ward. Molecular typing by whole genome sequencing and cgMLST analysis was used to determine clonal relatedness. Results: Between 2017 and 2020 five pairs of MRSA patients with first detection later than two days after admission and overlapping stay in the same room were evaluable, of whom two had the same clone according to cgMLST typing. The respective numbers for patient pairs with overlapping stay on the same ward and available isolates were six out of 47 pairs. Of the latter patients, 2.1% had a negative MRSA screening within the previous 14 days. Complex types accounting for transmissions were CT1426, CT1422, CT32066, CT30303, CT31532. Conclusion: Even in MRSA patient pairs with a plausible epidemiological link the majority was not due to a transmission event between them in a setting without universal screening on admission. Our results help to estimate the pretest probability for transmission events, which might be useful when typing results are lacking or not yet available.

Dr. Med

Genomic reconstruction of an azole-resistant Candida parapsilosis outbreak and the creation of a multilocus sequence typing scheme

BackgroundFluconazole-resistant Candida parapsilosis has emerged as a significant healthcare-associated pathogen with a propensity to spread patient-to-patient and cause nosocomial outbreaks, similar to Candida auris. This study investigates a prolonged outbreak of fluconazole-resistant C. parapsilosis across multiple years and healthcare centers in Germany.MethodsWe employed whole-genome sequencing of isolates from the outbreak, other regions within Germany, and compared them with isolates from a global distribution to understand the molecular epidemiology of this outbreak. Additionally, we used the genomic dataset of 258 samples to identify loci with high discriminatory power to establish the first multi-locus sequence typing (MLST) strategy for C. parapsilosis.ResultsA clonal, azole-resistant strain of C. parapsilosis was observed causing invasive infections over multiple years and in multiple hospitals within the outbreak city. Including this outbreak clone, we identified three distinct ERG11 Y132F azole-resistant lineages in Germany, marking the first description of this azole-resistance in the country and its endemic status. Using the novel MLST strategy, isolates were categorized into 31 sequence types, proving the utility of the typing scheme for genetic epidemiology and outbreak investigations as a rapid alternative to whole genome sequencing. Temporal and genomic reconstruction of the outbreak indicated that transfer of patients between healthcare facilities was likely responsible for the persistent reimportation of the drug-resistant clone and subsequent person-to-person transmission.ConclusionsThis research underscores the importance of monitoring of C. parapsilosis epidemiology, not only in Germany but globally. The emergence of azole-resistant lineages necessitates continuous surveillance and rigorous infection control measures. By combining large-scale genomic epidemiology and introducing a novel typing method, our study offers valuable insights into the management of emerging healthcare-associated pathogens, with direct implications for public health and clinical practice.

Raum 10-11

FG Infektionsprävention und Antibiotikaresistenz in der Krankenhaushygiene & StAG Allgemeine und Krankenhaushygiene (FG PR HY / StAG Hyg)

Oral Session

Nosocomial Pathogens: Gram-Positives and Candida

Technical hygiene, environmental sustainability regarding the climate change

Oral Sessions

Oral Session
Nosocomial Pathogens: Gram-Positives and Candida

Appointment

Chair

Topics

Description

Programme

Oral SessionNosocomial Pathogens: Gram-Positives and Candida

Appointment

Chair

Topics

Description

Programme

Oral Session
Nosocomial Pathogens: Gram-Positives and Candida