Retrospective application of the HEAR score on patients evacuated for chest pain: Assessing the utility of point-of-care troponin

Introduction

The HEART scoring system codifies the clinical gestalt used by physicians with 0-2 points assigned to 5 criteria (history, electrocardiography, age, risk factors and troponin). This scoring provides a prognostic tool that assists in disposition planning. The use of a truncated HEART score, minus the troponin data (HEAR score), was used for patients presenting with chest pain at one of four outpost nursing stations served by La Ronge Health Centre in northern Saskatchewan. These nursing stations have no onsite physician and no ability to obtain any troponin data. This study set out to determine if there was any utility in conducting point-of-care (PoC) troponins in these nursing outposts.

Materials and Methods

A retrospective analysis was conducted using the La Ronge regional electronic medical record by searching for all patients for whom an outpost nurse had called a physician regarding chest pain symptoms between 01 January 2011 and 31 December 2016. The HEAR and HEART score were then calculated for each individual presentation of patients with chest pain that met inclusion and exclusion criteria.

Results

By calculating both the patient's HEART score before evacuation from the outposts and after (i.e. with the troponin data), we were able to determine that, in 89.4% of cases (110/123 events), patients would require evacuation regardless of the troponin values due to a HEART score ≥4. In 10.6% (13/124 events) of cases, the patients who were evacuated had a HEART score ≤3, and in only one case did the troponin data increase this score.

Conclusions

The majority of patients would continue to be evacuated regardless of the result of their PoC troponin due to an already elevated HEAR score. PoC troponin is unlikely to reduce the rate of evacuation of patients with chest pain from the nursing stations served by the La Ronge Health Centre.

Direct-PCR from rectal swabs and environmental reservoirs: A fast and efficient alternative to detect blaOXA-48 carbapenemase genes in an Enterobacter cloacae outbreak setting

Carbapenemase-producing bacteria are a risk factor in clinical settings worldwide. The aim of the study was to accelerate the time to results during an outbreak situation with bla_OXA-48-positive Enterobacter cloacae by using a real-time multiplex quantitative PCR (qPCR) directly on rectal swab specimens and on wastewater samples to detect carbapenemase-producing bacteria. Thus, we analyzed 681 rectal swabs and 947 environmental samples during a five-month period by qPCR and compared the results to culture screening. The qPCR showed a sensitivity of 100% by testing directly from rectal swabs and was in ten cases more sensitive than the culture-based methods. Environmental screening for bla_OXA-48-carbapenemase genes by qPCR revealed reservoirs of different carbapenemase genes that are potential sources of transmission and might lead to new outbreaks. The rapid identification of patients colonized with those isolates and screening of the hospital environment is essential for earlier patient treatment and eliminating potential sources of nosocomial infections.

A Volatile and Dynamic Longitudinal Microbiome Is Associated With Less Reduction in Lung Function in Adolescents With Cystic Fibrosis

Progressive impairment in lung function caused by chronic polymicrobial airway infection remains the major cause of death in patients with cystic fibrosis (CF). Cross-sectional studies suggest an association between lung function decline and specific lung microbiome ecotypes. However, longitudinal studies on the stability of the airway microbiome are missing for adolescents with CF constituting the age group showing the highest rate of decline in lung function. In this study, we analyzed longitudinal lung function data and sputum samples collected over a period of 3 to 5 years from 12 adolescents with CF. The sputum microbiome was analyzed using 16S rRNA gene sequencing. Our results indicate that the individual course of the lung microbiome is associated with longitudinal lung function. In our cohort, patients with a dynamic, diverse microbiome showed a slower decline of lung function measured by FEV_1% predicted, whereas a more stable and less diverse lung microbiome was related to worse outcomes. Specifically, a higher abundance of the phyla Bacteroidetes and Firmicutes was linked to a better clinical outcome, while Proteobacteria were correlated with a decline in FEV_1% predicted. Our study indicates that the stability and diversity of the lung microbiome and the abundance of Bacteroidetes and Firmicutes are associated with the lung function decline and are one of the contributing factors to the disease severity.

Genomic Investigation and Successful Containment of an Intermittent Common Source Outbreak of OXA-48-Producing Enterobacter cloacae Related to Hospital Shower Drains

The hospital environment has been reported as a source of transmission events and outbreaks of carbapenemase-producing Enterobacterales. Interconnected plumbing systems and the microbial diversity in these reservoirs pose a challenge for outbreak investigation and control. A total of 133 clinical and environmental OXA-48-producing Enterobacter cloacae isolates collected between 2015 and 2021 were characterized by whole-genome sequencing (WGS) to investigate a prolonged intermittent outbreak involving 41 patients in the hematological unit. A mock-shower experiment was performed to investigate the possible acquisition route. WGS indicated the hospital water environmental reservoir as the most likely source of the outbreak. The lack of diversity of the blaOXA-48-like harbouring plasmids was a challenge for data interpretation. The detection of blaOXA-48-like-harboring E. cloacae strains in the shower area after the mock-shower experiment provided strong evidence that showering is the most likely route of acquisition. Initially, in 20 out of 38 patient rooms, wastewater traps and drains were contaminated with OXA-48-positive E. cloacae. Continuous decontamination using 25% acetic acid three times weekly was effective in reducing the trap/drain positivity in monthly environmental screening but not in reducing new acquisitions. However, the installation of removable custom-made shower tubs did prevent new acquisitions over a subsequent 12-month observation period. In the present study, continuous decontamination was effective in reducing the bacterial burden in the nosocomial reservoirs but was not sufficient to prevent environment-to-patient transmission in the long term. Construction interventions may be necessary for successful infection prevention and control. IMPORTANCE The hospital water environment can be a reservoir for a multiward outbreak, leading to acquisitions or transmissions of multidrug-resistant organisms in a hospital setting. The majority of Gram-negative bacteria are able to build biofilms and persist in the hospital plumbing system over a long period of time. The elimination of the reservoir is essential to prevent further transmission and spread, but proposed decontamination regimens, e.g., using acetic acid, can only suppress but not fully eliminate the environmental reservoir. In this study, we demonstrated that colonization with multidrug-resistant organisms can be acquired by showering in showers with contaminated water traps and drains. A construction intervention by installing removable and autoclavable shower inserts to avoid sink contact during showering was effective in containing this outbreak and may be a viable alternative infection prevention and control measure in outbreak situations involving contaminated shower drains and water traps.

Invasiveness of Escherichia coli Is Associated with an IncFII Plasmid

Escherichia coli is one of the most prevalent pathogens, causing a variety of infections including bloodstream infections. At the same time, it can be found as a commensal, being part of the intestinal microflora. While it is widely accepted that pathogenic strains can evolve from colonizing E. coli strains, the evolutionary route facilitating the commensal-to-pathogen transition is complex and remains not fully understood. Identification of the underlying mechanisms and genetic changes remains challenging. To investigate the factors involved in the transition from intestinal commensal to invasive E. coli causing bloodstream infections, we compared E. coli isolated from blood culture to isolates from the rectal flora of the same individuals by whole genome sequencing to identify clonally related strains and potentially relevant virulence factors. in vitro invasion assays using a Caco- 2 cell intestinal epithelial barrier model and a gut organoid model were performed to compare clonally related E. coli. The experiments revealed a correlation between the presence of an IncFII plasmid carrying hha and the degree of invasiveness. In summary, we provide evidence for the role of an IncFII plasmid in the transition of colonization to invasion in clinical E. coli isolates.

The Impact of Discontinuing Contact Precautions and Enforcement of Basic Hygiene Measures on Nosocomial Vancomycin-Resistant Enterococcus faecium Transmission

OBJECTIVES

Vancomycin-resistant Enterococcus faecium (VREfm) has emerged as a pathogen of major public health concern. Although definitive evidence is lacking, contact precautions have been a crucial element in infection prevention and control (IPC) strategies designed to limit nosocomial VRE transmissions. This study investigates the effect of discontinuing contact precautions while enforcing basic hygiene measures, including hand hygiene, environmental cleaning, and antiseptic body washing, for VRE patients at ICUs on prevention of nosocomial VRE transmission causing bacteraemia.

METHODS

Contact precaution was discontinued in January 2018. A total of 96 VREfm isolates from 61 ICU patients with VREfm bacteraemia and/or colonization from 8 ICUs in 2016 and 2019 in a tertiary care hospital were characterized by whole genome sequenicng. VRE transmission was investigated using patient movement data and admission screening for reliable identification of nosocomial acquisition.

RESULTS

Discontinuation of contact precautions did not increase VREfm transmission events (8 in 2016 vs 1 in 2019). While the rate of endogenous VREfm was similar in both years (38% vs 31%), the number of non-colonized patients prior to VREfm bacteraemia was 16 (16/29; 55%) in 2019, which was significantly higher than in 2016 (8/32; 25%). The mean incidence density for VREfm bacteraemia was similar for both years; 0.26 versus 0.31 per 1000 patient days in 2016 and 2019, respectively.

CONCLUSION

Our data suggest that discontinuation of contact precaution, while enforcing the basic hygiene measures did not lead to an increase of nosocomial bloodstream infection rates due to transmissions of VREfm in hyperendemic ICU settings.

Phenotypic Detection of Hemin-Inducible Trimethoprim-Sulfamethoxazole Heteroresistance in Staphylococcus aureus

Trimethoprim-sulfamethoxazole (SXT) is a valuable second-line antimicrobial agent to treat methicillin-resistant Staphylococcus aureus infections. Discrepancies between various antibiotic susceptibility testing (AST) methods for SXT susceptibility in S. aureus have been described. Here, we describe a hemin-inducible heteroresistance phenotype in S. aureus. We compared the results of the Vitek 2 AST on a set of 95 S. aureus clinical isolates with broth microdilution, disk diffusion using standard Mueller-Hinton agar, and disk diffusion using Mueller-Hinton agar supplemented with 5% horse blood (MHF). To investigate the potential clinical relevance of SXT heteroresistance, an in vivo Galleria mellonella infection assay was performed. All Vitek 2 SXT-susceptible (n = 17) isolates were concordant with AST results by other methods applied in this study. In 32/78 (41%) of Vitek 2 SXT-resistant isolates, we observed a heteroresistant growth phenotype on MHF. The heteroresistance phenotype was associated with the presence of dfr genes, encoding trimethoprim resistance. The addition of a hemin-impregnated disk in a double disk diffusion method on standard Mueller-Hinton agar was able to induce growth in the SXT zone of inhibition. An in vivo infection assay with G. mellonella suggested that the SXT heteroresistance phenotype resulted in lethality similar to that of the SXT-resistant phenotype. In this study, we describe a novel hemin-inducible heteroresistance phenotype in S. aureus. This heteroresistance phenotype may be missed by standard AST methods but can be detected by performing disk diffusion using Mueller-Hinton agar supplemented with 5% horse blood, commonly used for AST of fastidious organisms. This phenomenon may partly explain the discrepancies of AST methods in determining SXT resistance in S. aureus. IMPORTANCE Staphylococcus aureus is one of most important pathogens in clinical medicine. Besides its virulence, the acquisition or emergence of resistance toward antibiotic agents, in particular to beta-lactam antibiotics (methicillin-resistant S. aureus [MRSA]), poses a major therapeutic challenge. Trimethoprim-sulfamethoxazole (SXT) is one of the effective antimicrobial agents of last resort to treat MRSA infections. Here, we report the detection of a SXT-heteroresistant phenotype which is inducible by hemin and can be detected using Mueller-Hinton agar supplemented with horse blood. Heteroresistance describes the presence or emergence of resistant subpopulations, which may potentially lead to inaccurate antibiotic susceptibility testing results and influence the success of antibiotic therapy.

Molecular analysis of an increase in trimethoprim/sulfamethoxazole-resistant MRSA reveals multiple introductions into a tertiary care hospital, Germany 2012-19

OBJECTIVES

Increasing spread of resistance could jeopardize the use of antifolates against MRSA infections.

METHODS

We compared the prevalence of phenotypic trimethoprim/sulfamethoxazole resistance in 20 534 clinical Staphylococcus aureus isolates (19 096 MSSA and 1438 MRSA) of non-redundant patients at Heidelberg University Hospital over 8 years and performed WGS on trimethoprim/sulfamethoxazole-resistant MRSA.

RESULTS

From 2012 to 2019, trimethoprim/sulfamethoxazole resistance in MSSA (674/19 096; 3.5%) ranged between 1.5% and 7.2% and in MRSA (135/1438; 9.4%) between 0.5% and 20.2%, reaching a peak in 2016 and 2018, respectively (Ptrend < 0.001). Trimethoprim/sulfamethoxazole resistance was more likely in outpatients than inpatients (P = 0.005), younger patients (P < 0.001), skin and soft tissue infections (SSTIs) (MRSA only, P = 0.05), submissions from pulmonology (MRSA only, P = 0.001), the upper respiratory tract (MSSA only, P < 0.001) and general surgery (MSSA only, P = 0.001). WGS of 76 trimethoprim/sulfamethoxazole-resistant MRSA revealed that 59% belonged to major pandemic CA-MRSA clones (ST22, ST8, ST398, ST772, ST30), 47% harboured Panton-Valentine leucocidin (PVL), 97% SCCmec IV/V, 71% dfrG and 28% dfrA. SNP-based phylogeny of trimethoprim/sulfamethoxazole-resistant MRSA core genomes favoured independent introduction over clonal expansion as the source, most prominently of dfrA+ trimethoprim/sulfamethoxazole-resistant ST22 MRSA from the Gaza Strip.

CONCLUSIONS

The presented results support that trimethoprim/sulfamethoxazole-resistant S. aureus, formerly associated with SSTI from outpatients and S. aureus in the (sub)tropics, is on the rise in the temperate zone, potentially due to migration. Closer monitoring of trimethoprim/sulfamethoxazole resistance in S. aureus is recommended to safeguard the effectiveness of antifolate compounds.

Surveillance for Colonization, Transmission, and Infection With Methicillin-Susceptible Staphylococcus aureus in a Neonatal Intensive Care Unit

IMPORTANCE

Staphylococcus aureus is one of the leading causes of infections in neonatal intensive care units (NICUs). Most studies in this patient group focus on methicillin-resistant S aureus or the outbreak setting, whereas data for methicillin-susceptible S aureus are limited.

OBJECTIVES

To identify risk factors for S aureus colonization and infections in hospitalized newborns and to investigate S aureus transmission and its dynamics in a nonoutbreak setting.

DESIGN, SETTING, AND PARTICIPANTS

This monocentric cohort study in a tertiary NICU in Heidelberg, Germany, enrolled all hospitalized neonates (n = 590) with at least 1 nasal screening swab positive for S aureus. Data were collected from January 1, 2018, to December 31, 2019.

EXPOSURES

Weekly screening for S aureus colonization was performed for all newborns until discharge.

MAIN OUTCOMES AND MEASURES

The primary end point was any S aureus infection until hospital discharge. Transmission of S aureus and performance of routine typing to detect transmissions were defined as the secondary outcomes of the study.

RESULTS

In total, 590 newborns were enrolled (276 [46.8%] female and 314 [53.2%] male; 220 [37.3%] with birthweight <1500 g; 477 [80.8%] preterm; 449 [76.1%] singletons; 419 [71.5%] delivered via cesarean section). The median length of stay was 26 (range, 10-62) days. Overall, 135 infants (22.9%) were colonized by S aureus at some time during their hospital stay. The median time to first detection was 17 (interquartile range, 11-37) days. The overall incidence of S aureus infection was 1.7% (10 of 590). Low birth weight (<1500 g [odds ratio, 9.3; 95% CI, 5.9-14.6; P < .001]) and longer hospital stay (odds ratio, 2.3; 95% CI, 1.9-2.7; P < .001) were associated with colonization. Nasal carriage was significantly associated with S aureus infection (odds ratio, 8.2; 95% CI, 2.1-32.3; P = .002). A total of 123 of 135 colonization isolates were sequenced. All recoverable infection isolates (4 of 7) of newborns with colonization were genetically identical to the colonizing isolate. Whole-genome sequencing indicated 23 potential transmission clusters.

CONCLUSIONS AND RELEVANCE

The findings of this cohort study suggest that nasal colonization is a relevant risk factor for S aureus infection in a nonoutbreak NICU setting. In colonized newborns, infection and colonization isolates were genetically identical, suggesting that eradication of colonization may be a useful measure to prevent infection. Further investigations are necessary to validate and assess the generalizability of our findings.

Host factors facilitating SARS-CoV-2 virus infection and replication in the lungs

SARS-CoV-2 is the virus causing the major pandemic facing the world today. Although, SARS-CoV-2 primarily causes lung infection, a variety of symptoms have proven a systemic impact on the body. SARS-CoV-2 has spread in the community quickly infecting humans from all age, ethnicities and gender. However, fatal outcomes have been linked to specific host factors and co-morbidities such as age, hypertension, immuno-deficiencies, chronic lung diseases or metabolic disorders. A major shift in the microbiome of patients suffering of the coronavirus disease 2019 (COVID-19) have also been observed and is linked to a worst outcome of the disease. As many co-morbidities are already known to be associated with a dysbiosis of the microbiome such as hypertension, diabetes and metabolic disorders. Host factors and microbiome changes are believed to be involved as a network in the acquisition of the infection and the development of the diseases. We will review in detail in this manuscript, the immune response toward SARS-CoV-2 infection as well as the host factors involved in the facilitation and worsening of the infection. We will also address the impact of COVID-19 on the host's microbiome and secondary infection which also worsen the disease.

Pitfalls in genotypic antimicrobial susceptibility testing caused by low expression of blaKPC in Escherichia coli

BACKGROUND

There is a growing interest in the rapid genotypic identification of antimicrobial resistance (AMR). In routine diagnostics, we detected multiple KPC-positive Escherichia coli (KPC-Ec) with discordant phenotypic meropenem susceptibility from a single patient's blood cultures, which prompted a more thorough investigation.

OBJECTIVES

We investigated the potential clinical relevance of, and the mechanism behind, discordant phenotypic and genotypic meropenem susceptibility in KPC-Ec.

METHODS

WGS was used to perform a comparative analysis of the isolates' genetic characteristics and their blaKPC-2 locus. Expression of blaKPC-2 was determined by quantitative PCR and the potency of meropenem hydrolysis was determined using a semi-quantitative carbapenem inactivation method. An in vivo infection assay using Galleria mellonella was performed to assess the potential clinical relevance of KPC expression in E. coli.

RESULTS

Despite the presence of blaKPC-2, three of five isolates were susceptible to meropenem (MICVITEK2 ≤ 0.25 mg/L), while two isolates were resistant (MICVITEK2 ≥ 16 mg/L). The isolates with high MICs had significantly higher blaKPC-2 expression, which corresponds to phenotypic meropenem inactivation. The genetic environment of blaKPC-2, which may impact KPC production, was identical in all isolates. In vivo infection assay with G. mellonella suggested that meropenem was effective in reducing mortality following infection with low-expressing KPC-Ec.

CONCLUSIONS

Our findings clearly highlight a limitation of genotypic AMR prediction for blaKPC. For the time being, genotypic AMR prediction requires additional analysis for accurate antibiotic therapy decision-making.

Challenges in interpretation of WGS and epidemiological data to investigate nosocomial transmission of vancomycin-resistant Enterococcus faecium in an endemic region: incorporation of patient movement network and admission screening

OBJECTIVES

VRE are listed, by the WHO, among the leading resistant pathogens causing greatest public concern; hence the spread and transmission of VRE, especially in hospitalized patients, need to be monitored. Despite the advancements in typing methods since the implementation of WGS for outbreak investigations, data interpretation, especially for vancomycin-resistant Enterococcus faecium (VREfm) in an endemic setting, remains challenging. In this study we explored the potential added benefit of incorporating patient movement data and admission screening to accurately estimate the magnitude of an outbreak.

METHODS

We sequenced 73 VREfm isolates from patients with bacteraemia (n = 43) and rectal colonization (n = 30/32). Genetic relatedness was determined by SNP distance (≤10) between isolates. Patient movements were visualized in a movement network, along with contact intensity and rectal colonization status prior to infection onset.

RESULTS

ST117, ST80 and ST203 were the predominant STs in our study population. Forty-four percent (18/41) of VREfm bacteraemia cases were of endogenous origin. SNP analysis of infection and colonization isolates revealed nine clonal groups. Eighty-six percent (37/43) of the patients were visualized in a transmission network due to spatiotemporal overlap. Nineteen out of 43 (44%) belonged to five transmission clusters. Incorporation of prior colonization status revealed that transmission was very likely in only 63% (12/19) of patients in these transmission clusters.

DISCUSSION

Although interpretation of WGS data is challenging, incorporation of patient movement data and colonization status by admission screening of high-risk patients may provide additional resolution when interpreting the magnitude of an outbreak in an endemic setting.

Molecular Detection of Carbapenemases in Enterobacterales: A Comparison of Real-Time Multiplex PCR and Whole-Genome Sequencing

Carbapenem-resistant Enterobacterales are a growing problem in healthcare systems worldwide. While whole-genome sequencing (WGS) has become a powerful tool for analyzing transmission and possible outbreaks, it remains laborious, and the limitations in diagnostic workflows are not well studied. The aim of this study was to compare the performance of WGS and real-time multiplex PCR (RT-qPCR) for diagnosing carbapenem-resistant Enterobacterales. In this study, we analyzed 92 phenotypically carbapenem-resistant Enterobacterales, sent to the University Hospital Heidelberg in 2019, by the carbapenem inactivation method (CIM) and compared WGS and RT-qPCR as genotypic carbapenemase detection methods. In total, 80.4% of the collected isolates were identified as carbapenemase producers. For six isolates, discordant results were recorded for WGS, PCR and CIM, as the carbapenemase genes were initially not detected by WGS. A reanalysis using raw reads, rather than assembly, highlighted a coverage issue with failure to detect carbapenemases located in contigs with a coverage lower than 10×, which were then discarded. Our study shows that multiplex RT-qPCR and CIM can be a simple alternative to WGS for basic surveillance of carbapenemase-producing Enterobacterales. Using WGS in clinical workflow has some limitations, especially regarding coverage and sensitivity. We demonstrate that antimicrobial resistance gene detection should be performed on the raw reads or non-curated draft genome to increase sensitivity.

Acquisition and Transmission of Carbapenemase-Producing (blaKPC-2) Enterobacter cloacae in a Highly Frequented Outpatient Clinic

The role of outpatient clinics as a potential transmission ground for multidrug-resistant organisms has not been adequately investigated. Here, we report a transmission cluster of blaKPC-2-positive Enterobacter cloacae among patients treated in a highly frequented outpatient department.

Fast and automated detection of common carbapenemase genes using multiplex real-time PCR on the BD MAX™ system

Fast detection of carbapenemases in Gram-negative bacilli is necessary for accurate antibiotic treatment, prevention of further spreading and surveillance purposes. We analyzed the current occurrence of gene variants and designed two multiplex PCRs with hydrolysis probes. The assay was developed for the BD MAX™ system that combines DNA extraction and PCR in a fully automated procedure providing results within 3 h and was evaluated for detection of carbapenemases from bacterial isolates and directly from rectal swabs. The assay has a theoretic coverage of 97.1% for carbapenemases detected during the last years by the German National Reference Laboratory (NRL). A collection of 151 isolates from the NRL was used and all carbapenemase-positive bacteria (58/58) were identified correctly. The direct-PCR on rectal swabs revealed additional carbapenemase genes in 7 samples that were not identified by the culture-based method used as reference method. The assay allows detection of carbapenemases from clinical isolates and might also help in rapid detection directly from rectal samples.

Changes in the Cystic Fibrosis Airway Microbiome in Response to CFTR Modulator Therapy

The development of CFTR modulator therapies significantly changed the treatment scheme of people with cystic fibrosis. However, CFTR modulator therapy is still a life-long treatment, which is not able to correct the genetic defect and cure the disease. Therefore, it becomes crucial to understand the effects of such modulation of CFTR function on the airway physiology, especially on airway infections and inflammation that are currently the major life-limiting factors in people with cystic fibrosis. In this context, understanding the dynamics of airway microbiome changes in response to modulator therapy plays an essential role in developing strategies for managing airway infections. Whether and how the newly available therapies affect the airway microbiome is still at the beginning of being deciphered. We present here a brief review summarizing the latest information about microbiome alterations in light of modern cystic fibrosis modulator therapy.

Emergence of carbapenem-resistant ST131 Escherichia coli carrying bla OXA-244 in Germany, 2019 to 2020

The dissemination of carbapenem-producing Gram-negative bacteria is a major public health concern. We report the first detection of OXA-244-producing ST131 O16:H5 Escherichia coli in three patients from two tertiary hospitals in the south-west of Germany. OXA-244 is emerging in Europe. Because of detection challenges, OXA-244-producing E. coli may be under-reported. The emergence of carbapenem resistance in a globally circulating high-risk clone, such as ST131 E. coli is of clinical relevance and should be monitored closely.

Genomic structure of ST8-t008 USA300 and USA300-LV MRSA in the Rhine-Neckar Region, Germany, 2012-2018

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) ST8-t008 of the pulsotype USA300 and the Latin American variant (USA300-LV) are the predominant virulent MRSA clonal lineages on the American continent. In Europe, the occurrence of USA300 or USA300-LV has often been related to international travel or outbreaks in hospitals. The replacement of local epidemic MRSA clones by these hypervirulent clones has not yet been demonstrated in Europe. This study aimed to gain insight into the genetic relatedness of ST8-t008 MRSA encountered in previous studies in the Rhine-Neckar Region, Germany, and ST8-t008 MRSA from other geographic regions.

METHODS

Nineteen ST8-t008 MRSA isolated between 2012 and 2018 were compared with publicly available sequences of ST8-t008 MRSA from travellers returning from the tropics, and USA300 and USA300-LV that were previously encountered in Europe.

RESULTS

We identified 14 of 19 (73.7%) of the local ST8-t008 MRSA being related to USA300 and five of 19 (26.3%) belonging to the USA300-LV cluster. Four suspected transmission clusters were identified without any evidence of in-hospital transmission.

CONCLUSION

The genetic relatedness of these local strains to publicly available sequences of ST8-t008 MRSA from other parts of Europe and to MRSA of travellers returning from the tropics pointed to multiple introductions into Germany. However, four suspected transmission clusters may be an indication of transmission within the community.

Integrative Analysis of Whole Genome Sequencing and Phenotypic Resistance Toward Prediction of Trimethoprim-Sulfamethoxazole Resistance in Staphylococcus aureus

As whole genome sequencing is becoming more accessible and affordable for clinical microbiological diagnostics, the reliability of genotypic antimicrobial resistance (AMR) prediction from sequencing data is an important issue to address. Computational AMR prediction can be performed at multiple levels. The first-level approach, such as simple AMR search relies heavily on the quality of the information fed into the database. However, AMR due to mutations are often undetected, since this is not included in the database or poorly documented. Using co-trimoxazole (trimethoprim-sulfamethoxazole) resistance in Staphylococcus aureus, we compared single-level and multi-level analysis to investigate the strengths and weaknesses of both approaches. The results revealed that a single mutation in the AMR gene on the nucleotide level may produce false positive results, which could have been detected if protein sequence analysis would have been performed. For AMR predictions based on chromosomal mutations, such as the folP gene of S. aureus, natural genetic variations should be taken into account to differentiate between variants linked to genetic lineage (MLST) and not over-estimate the potential resistant variants. Our study showed that careful analysis of the whole genome data and additional criterion such as lineage-independent mutations may be useful for identification of mutations leading to phenotypic resistance. Furthermore, the creation of reliable database for point mutations is needed to fully automatized AMR prediction.

Relationship between airway dysbiosis, inflammation and lung function in adults with cystic fibrosis

Airway dysbiosis has been associated with lung disease severity in patients with cystic fibrosis (CF). However, the relationship between dysbiosis, airway inflammation and lung function impairement remains poorly understood. The aim of this study was therefore to determine how the structure of the sputum microbiota, airway inflammation markers and spirometry are related in patients with CF. Sputum samples were collected from 106 CF patients between 12 and 72 years. These were analyzed by 16S rRNA gene amplicon sequencing. Moreover, levels of pro-inflammatory cytokines (IL-1β, IL-8, IL-6 and TNF-α) and Neutrophil elastase (NE) were determined. The relationship between the microbiota, inflammation markers and forced expiratory volume in one second percent predicted (FEV₁% predicted) was evaluated by multi-parameter analysis. The microbiota α-diversity correlated inverse with inflammation markers IL-1β, IL-8, TNF-α, NE and positively with FEV₁% predicted. Patients could be divided into 7 clusters based on their microbiota structure. The most diverse cluster was defined by oropharyngeal-like flora (OF) while the others were characterized by the dominance of a single pathogen. Patients with the diverse OF microbiota cluster had lower sputum inflammatory markers and higher FEV₁% predicted compared to patients with a pathogen-dominated microbiota including Pseudomonas aeruginosa. Our results suggest that the diversity of the airway microbiota is an important biomarker of the severity of airway inflammation linking dysbiosis to lung function decline in patients with CF.

Comparative evaluation of the effect of different growth media on in vitro sensitivity to azithromycin in multi-drug resistant Pseudomonas aeruginosa isolated from cystic fibrosis patients

Long-term treatment with azithromycin is a therapeutic option in Cystic Fibrosis (CF) patients chronically infected with P. aeruginosa. It was recently shown that azithromycin has direct antimicrobial activity when P. aeruginosa isolates are tested in Roswell Park Memorial Institute medium supplemented with fetal calf serum (RPMI 1640/FCS) by broth microdilution. We now investigated whether (i) azithromycin might also be active against multidrug resistant (MDR) P. aeruginosa isolated from CF patients and (ii) how in vitro sensitivity assays perform in synthetic cystic fibrosis sputum medium (SCFM), a medium that mimics the particular CF airway environment. In 17 (59%) out of 29 MDR P. aeruginosa CF isolates MICs for azithromycin ranged between 0.25 and 8 μg/ml and 12 isolates (41%) showed a MIC ≥512 μg/ml when measured in RPMI/FCS. In contrast, MICs were ≥ 256 μg/ml for all P. aeruginosa MDR isolates when tested in either SCFM or in conventional cation-adjusted Mueller Hinton Broth. High MIC values observed in CF adapted medium SCFM for both PAO1 and MDR P. aeruginosa CF isolates, as opposed to findings in RPMI, argue against routine azithromycin MIC testing of CF isolates.

Comparison of pre-fire and post-fire space use reveals varied responses by woodland caribou (Rangifer tarandus caribou) in the Boreal Shield

By regulating successional dynamics in Canada’s boreal forest, fires can affect the distribution of the Threatened woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)). Caribou tend to avoid areas burned within the last 40 years; however, few studies have compared pre-fire and post-fire caribou observations. In this study, we used caribou GPS locations from the Boreal Shield of Saskatchewan, Canada, to assess the short-term response of caribou to areas that burned while they were collared (hereafter recent burns). We used a “before–after, control–impact” design to compare the overlap of pre-fire and post-fire seasonal home ranges to the overlap of year-to-year seasonal home ranges. Caribou rarely encountered recent burns and when they did, they adjusted their space use in variable and complex ways that were largely indistinguishable from regular, interannual variation. Caribou tended to reduce use of recent burns in summer–autumn and winter, but not during the calving season, in some cases shifting their home range to incorporate more burned habitat. We conclude that recently burned areas (<5 years) may provide habitat value to woodland caribou, particularly during the calving season, requiring a more flexible approach to interpret fire in habitat management strategies.

Early Cytokine Induction Upon Pseudomonas aeruginosa Infection in Murine Precision Cut Lung Slices Depends on Sensing of Bacterial Viability

Breathing allows a multitude of airborne microbes and microbial compounds to access the lung. Constant exposure of the pulmonary microenvironment to immunogenic particles illustrates the need for proper control mechanisms ensuring the differentiation between threatening and harmless encounters. Discrimination between live and dead bacteria has been suggested to be such a mechanism. In this study, we performed infection studies of murine precision cut lung slices (PCLS) with live or heat-killed P. aeruginosa, in order to investigate the role of viability for induction of an innate immune response. We demonstrate that PCLS induce a robust transcriptomic rewiring upon infection with live but not heat-killed P. aeruginosa. Using mutants of the P. aeruginosa clinical isolate CHA, we show that the viability status of P. aeruginosa is assessed in PCLS by TLR5-independent sensing of flagellin and recognition of the type three secretion system. We further demonstrate that enhanced cytokine expression towards live P. aeruginosa is mediated by uptake of viable but not heat-killed bacteria. Finally, by using a combined approach of receptor blockage and genetically modified PCLS we report a redundant involvement of MARCO and CD200R1 in the uptake of live P. aeruginosa in PCLS. Altogether, our results show that PCLS adapt the extent of cytokine expression to the viability status of P. aeruginosa by specifically internalizing live bacteria.