The EC-COMPASS: Long-term, multi-centre surveillance of Enterobacter cloacae complex - a clinical perspective

BACKGROUND

Enterobacter cloacae complex (ECCO) comprises closely related Enterobacterales, causing a variety of infections ranging from mild urinary tract infections to severe bloodstream infections. ECCO has emerged as a significant cause of healthcare-associated infections, particularly in neonatal and adult intensive care.

AIM

The Enterobacter Cloacae COMplex PASsive Surveillance (EC-COMPASS) aims to provide a detailed multi-centre overview of ECCO epidemiology and resistance patterns detected in routine microbiological diagnostics in four German tertiary-care hospitals.

METHODS

In a sentinel cluster of four German tertiary-care hospitals, all culture-positive ECCO results between 1st January 2020 and 31st December 2022, were analysed based on Hybase® laboratory data.

FINDINGS

Analysis of 31,193 ECCO datasets from 14,311 patients revealed a higher incidence in male patients (P<0.05), although no significant differences were observed in ECCO infection phenotypes. The most common sources of ECCO were swabs (42.7%), urine (17.5%), respiratory secretions (16.1%), blood cultures (8.9%) and tissue samples (5.6%). The annual bacteraemia rate remained steady at approximately 33 cases per hospital. Invasive ECCO infections were predominantly found in oncology and intensive care units. Incidences of nosocomial outbreaks were infrequent and limited in scope. Notably, resistance to carbapenems was consistently low.

CONCLUSION

EC-COMPASS offers a profound clinical perspective on ECCO infections in German tertiary-healthcare settings, highlighting elderly men in oncology and intensive care units as especially vulnerable to ECCO infections. Early detection strategies targeting at-risk patients could improve ECCO infection management.

Cross-contamination of carbapenem-resistant Gram-negative bacteria between patients and the hospital environment in the first year of a newly built surgical ward

BACKGROUND

Transmission and outbreaks of carbapenem-resistant Gram-negative bacteria (CRGN) in hospitals are often associated with contamination of the wastewater environment. We performed a prospective observational study to investigate the colonization of the hospital wastewater environment during the first year of occupancy of the surgical intermediate and intensive care units of a newly constructed building at the University Hospital of Heidelberg, Germany.

METHODS

We performed monthly screening of the wastewater system (toilets and sinks) for 12 months, starting 1 month before opening (1st October 2020 to 30th October 2021). Admission and weekly rectal screening of patients for CRGN were also performed in parallel. Bacterial isolates were characterized by whole-genome sequencing.

RESULTS

Twenty-seven of 1978 (1.4%) admitted patients were colonized/infected with CRGN. A total of 29 CRGN isolates from 24 patients and 52 isolates were available for sequencing. Within the first month of occupancy, we identified seven patients colonized/infected with CRGN, while none were found in the environmental reservoirs. The first detection of CRGN isolates in the sewage system started five months after the first occupancy. Two previously non-colonized patients were colonized/infected with Pseudomonas aeruginosa strains colonizing the sewage system. The significant identity of plasmids carrying the carbapenemase gene suggests that long-term colonization of the sewage system facilitates the emergence of new carbapenem-resistant clones.

CONCLUSION

Cross-contamination between patients and the hospital environment is bidirectional. Our study demonstrated that contamination of the hospital wastewater environment may lead to persistent colonization and may serve as a reservoir for nosocomial acquisition of CRGN.

Whole-genome sequencing disproves two suspected transmission events of blaNDM between Pseudomonas aeruginosa and Enterobacterales in hospitalized patients

New Delhi metallo-β-lactamase (bla_NDM) acquisition by Gram-negative bacteria is a primary concern due to its broad-host-range distribution. This study investigated two potential in-vivo horizontal gene transfers (HGTs) of bla_NDM between Enterobacterales and Pseudomonas aeruginosa, initially indicated by polymerase chain reaction. Whole-genome sequencing showed independent parallel acquisition of two different bla_NDM variants (NDM-1 and NDM-5) in P. aeruginosa and Enterobacterales, respectively. The data show that short-read sequencing provides the necessary resolution to confirm or dispute HGT by the comparison of genetic elements surrounding the gene of interest, and thus provide a timely response to potential outbreaks.

Comparative genomic analysis reveals a high prevalence of inter-species in vivo transfer of carbapenem-resistance plasmids in patients with haematological malignancies

OBJECTIVES

Conjugative gene transfer has been considered as one of the driving factors in the transmission and dissemination of multidrug resistance in bacteria. The abundance of antimicrobial resistance genes and bacteria in the gut microbiome may provide the ideal platform for plasmid exchange. Systematic data on in vivo horizontal gene transfer (HGT) and its frequency are scarce.

MATERIALS AND METHODS

One hundred and ninety-six carbapenem-resistant gram-negative bacilli (CRGNBs) from 179 patients (158 inpatients and 21 outpatients) between January 2016 and April 2017 were analysed retrospectively. Alignment of plasmid content for 32 isolates from 16 patients with multiple CRGNB species was performed from whole-genome sequencing (WGS) data.

RESULTS

Sixteen of the 179 patients (8.9%) were colonized and/or infected with more than one CRGNB species; 11/179 (6.1%) were colonized by multiple carbapenem-resistant Enterobacteriaceae (CREs) and 5/179 (2.8%) by carbapenem-resistant non-fermenters (CRNFs) and CREs. WGS suggested interspecies transfer as the predominant mechanism rather than independent acquisition in 8/10 patients (80%, one non-recoverable isolate) with multiple CREs but not in CRNF-CRE combinations; 30/158 inpatients (20%) had underlying haematological malignancies, and they are more likely to exhibit multiple CRGNB strains (OR 3.0, 95%CI 0.98-8.89, p 0.05) and CRE strains (OR 3.9, 95%CI 1.02-14.58, p 0.04) during hospital stay compared to other patient groups.

CONCLUSION

Our data give insight into the occurrence of natural in vivo HGT in a clinical setting. Better understanding of HGT will help optimize containment measures and may guide antibiotic stewardship programmes.

Alteration of antibiotic regimen as an additional control measure in suspected multi-drug-resistant Enterobacter cloacae outbreak in a neonatal intensive care unit

BACKGROUND

Increased occurrence of a particular species of Gram-negative bacteria (GNB), especially when multi-drug-resistant (MDR), in routine screening surveillance in neonatal intensive care units (NICUs) can be evoked by selection pressure.

AIM

To evaluate adaptation of the empiric antibiotic regimen for its usefulness as a control measure in suspected outbreaks in the NICU.

METHODS

In a retrospective outbreak analysis, cases between 1^st December 2017 and 31^st March 2018 were identified through microbiology and hygiene surveillance records. Furthermore, risk factors for MDR-GNB colonization were collected. Whole-genome sequencing (WGS) was performed on all isolates. Control measure documentations and interviews were employed to define interventions. As well as infection control measures, administration of third-generation cephalosporins was avoided and replaced whenever clinically acceptable as part of the intervention bundle.

FINDINGS

In total, nine patients were found to have rectal colonization with third-generation cephalosporin-resistant Enterobacter cloacae in routine screening surveillance in the pre-intervention period. After implementation of an infection control bundle, the incidence declined rapidly. WGS analysis revealed that two MDR E. cloacae were transmitted, and the majority were new cases. The incidence density of MDR-GNB colonization was 7.94/1000 patient-days (PD) before the intervention and 1.68/1000 PD during the altered antibiotic regimen. No infections with MDR-GNB occurred during the study.

CONCLUSIONS

Altering the antibiotic regimen with regard to selection pressure may be considered as part of an intervention bundle to rapidly control the emergence of MDR-GNB in suspected outbreak situations in the NICU.

Import of community-associated, methicillin-resistant Staphylococcus aureus to Europe through skin and soft-tissue infection in intercontinental travellers, 2011-2016

OBJECTIVES

Recently, following import by travel and migration, epidemic community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has caused nosocomial outbreaks in Europe, sometimes with a fatal outcome. We describe clinico-epidemiological characteristics of CA-MRSA detected by the European Network for the Surveillance of imported S. aureus (www.staphtrav.eu) from May 2011 to November 2016.

METHODS

Sentinel surveillance at 13 travel clinics enrolling patients with travel-associated skin and soft-tissue infection (SSTI) and analysing lesion and nose swabs at one central laboratory.

RESULTS

A total of 564 independent case-patients with SSTI were enrolled and had 374 (67%) S. aureus-positive lesions, of which 14% (51/374) were MRSA. The majority of CA-MRSA isolates from SSTI were Panton-Valentine leucocidin (PVL) -positive (43/51, 84%). The risk of methicillin-resistance in imported S. aureus varied by travel region (p <0.001) and was highest in Latin America (16/57, 28%, 95% CI 17.0-41.5) and lowest in Sub-Saharan Africa (4/121, 3%, 95% CI 0.9-8.3). Major epidemic clones (USA300 / USA300 Latin-American Variant, Bengal Bay, South Pacific) accounted for more than one-third (19/51, 37%) of CA-MRSA imports. CA-MRSA SSTI in returnees was complicated (31/51 multiple lesions, 61%; 22/50 recurrences, 44%), led to health-care contact (22/51 surgical drainage, 43%; 7/50 hospitalization, 14%), was transmissible (13/47 reported similar SSTI in non-travelling contacts, 28%), and associated with S. aureus nasal colonization (28 of 51 CA-MRSA cases, 55%; 24 of 28 colonized with identical spa-type in nose and lesion, 85%).

CONCLUSIONS

Travel-associated CA-MRSA SSTI is a transmissible condition that leads to medical consultations and colonization of the infected host.

Toll-like receptor 9 (TLR-9) promotor polymorphisms and gene expression are associated with persistent Staphylococcus aureus nasal carriage

OBJECTIVES

Toll-like receptor (TLR) 9 could have importance in human Staphylococcus aureus immunity, but population-level evidence for this hypothesis is missing.

METHODS

We phenotyped S. aureus nasal carriage of 603 volunteers using four consecutive swabs, genotyped TLR9 promotor variants in 106 persistent carriers and 219 noncarriers, measured TLR9-mRNA expression in whole blood after stimulation with viable S. aureus and studied mutual associations of carriage, transcriptional activity and single nucleotide polymorphisms while accounting for sex and hormone contraceptive use (HCU).

RESULTS

The -1486 (rs187084) and -1237 (rs5743836) CT haplotype was more common in noncarriers (185/438, 42%) than in carriers (63/212, 30%), with the TT haplotype showing a reverse association (noncarriers, 180/438, 41%; carriers 117/212, 55%) (χ² p 0.001). Mean TLR9 mRNA expression in whole blood was higher in noncarriers (ratio_{carriers/noncarriers} 0.63; 95% confidence interval, 0.43-0.92; p 0.017). A duplication of TLR9 transcriptional activity lowered the odds of persistent S. aureus carriage by 37% in the overall group (odds ratio = 0.63; 95% confidence interval, 0.42-0.94; p 0.022) and by 54% in women (odds ratio = 0.46; 95% confidence interval, 0.23-0.90; p 0.023). Promotor haplotype and HCU had a combined effect on TLR9 transcription (interaction model): women in the TT (risk) haplotype/HCU^- stratum (baseline) had lower mRNA levels than women in the CT (protective) haplotype/HCU^- (ratio 1.92; p 0.055), the CT haplotype/HCU⁺ (ratio 2.02; p 0.032) and the TT haplotype/HCU⁺ (ratio 2.59; p < 0.004) strata. No such associations were observed in men.

CONCLUSIONS

We provide evidence that TLR9 affects human S. aureus immunity and present potential explanations for differences according to sex in S. aureus colonization and infection.

Predominance of dfrG as determinant of trimethoprim resistance in imported Staphylococcus aureus

To investigate the global occurrence of trimethoprim-sulfamethoxazole resistance and the genetic mechanisms of trimethoprim resistance, we analysed Staphylococcus aureus from travel-associated skin and soft-tissue infections treated at 13 travel clinics in Europe. Thirty-eight per cent (75/196) were trimethoprim-resistant and 21% (41/196) were resistant to trimethoprim-sulfamethoxazole. Among methicillin-resistant S. aureus, these proportions were 30% (7/23) and 17% (4/23), respectively. DfrG explained 92% (69/75) of all trimethoprim resistance in S. aureus. Travel to South Asia was associated with the highest risk of acquiring trimethoprim-sulfamethoxazole-resistant S. aureus. We conclude that globally dfrG is the predominant determinant of trimethoprim resistance in human S. aureus infection.

Skin and soft tissue infections in intercontinental travellers and the import of multi-resistant Staphylococcus aureus to Europe

Staphylococcus aureus is emerging globally. Treatment of infections is complicated by increasing antibiotic resistance. We collected clinical data and swabs of returnees with skin and soft tissue infections (SSTI) at 13 travel-clinics in Europe (www.staphtrav.eu). Sixty-two percent (196/318) SSTI patients had S. aureus-positive lesions, of which almost two-thirds (122/196) were Panton-Valentine leukocidin (PVL) positive. PVL was associated with disease severity, including hospitalization for SSTI (OR 5.2, 95% CI 1.5-18.2). In returnees with SSTI, longer travel and more intense population contact were risk factors for nasal colonization with PVL-positive S. aureus. Imported S. aureus frequently proved resistant to trimethoprim-sulfamethoxazole (21%), erythromycin (21%), tetracycline (20%), ciprofloxacin (13%), methicillin (12%) and clindamycin (8%). Place of exposure was significantly (p < 0.05) associated with predominant resistance phenotypes and spa genotypes: Latin America (methicillin; t008/CC24/304), Africa (tetracycline, trimethoprim-sulfamethoxazole; t084/CC84, t314/singleton, t355/CC355), South Asia (trimethoprim-sulfamethoxazole, ciprofloxacin; t021/CC21/318), South-East Asia (clindamycin; t159/CC272). USA300-like isolates accounted for 30% of all methicillin-resistant S. aureus imported to Europe and were predominantly (71%) acquired in Latin America. Multi-resistance to non-β-lactams were present in 24% of imports and associated with travel to South Asia (ORcrude 5.3, 95% CI 2.4-11.8), even after adjusting for confounding by genotype (ORadjusted 3.8, 95% 1.5-9.5). Choosing randomly from compounds recommended for the empiric treatment of severe S. aureus SSTI, 15% of cases would have received ineffective antimicrobial therapy. These findings call for the development of regionally stratified guidance on the antibiotic management of severe imported S. aureus disease and put the infected and colonized traveller at the centre of interventions against the global spread of multi-resistant S. aureus.