Clinical relevance and impact of Corynebacterium isolation in lower respiratory tract of critically ill patients requiring mechanical ventilation

Incidence, etiology, and outcome of hospital-acquired pneumonia in patients with acute exacerbation of fibrotic idiopathic interstitial pneumonia

BACKGROUND

Acute exacerbations (AEs) of fibrotic idiopathic interstitial pneumonia (fIIP) that require hospitalization occur in some patients. During hospitalization, these patients can develop hospital-acquired pneumonia (HAP), a common hospital-acquired infection with a high mortality rate. However, the characteristics of HAP in AE-fIIP remain unknown. The purpose of this study was to determine the incidence, causative pathogens, and outcomes of HAP in patients with AE-fIIP.

METHODS

The medical records of consecutive patients who were hospitalized with AE-fIIP from January 2008 to December 2019 were analyzed for the incidence, causative pathogen, and survival of HAP. The records of patients with an obvious infection-triggered AE were excluded from analysis.

RESULTS

There were 128 patients with AE-fIIP (89 with idiopathic pulmonary fibrosis [IPF] and 39 with non-IPF fIIP) who were hospitalized a total of 155 times (111 with IPF and 44 with non-IPF fIIP). HAP occurred in 49 patients (40 with IPF and 9 with non-IPF fIIP). The incidence and the in-hospital mortality rates of HAP in patients with AE-fIIP were high, at 32.2% and 48.9%, respectively. Corynebacterium spp. was the most common causative pathogen, which was followed by human cytomegalovirus (HCMV).

CONCLUSIONS

The incidence and the in-hospital mortality rates of HAP in patients with AE-fIIP are high. To improve their survival, patients with fIIP who had AEs and HAP should receive prompt empirical treatment for possible infections with Corynebacterium spp. and testing for HCMV.

Corynebacterium spp.: relationship of pathogenic properties and antimicrobial resistance

Corynebacterium spp. are part of the human microbiome, but can cause the development of inflammatory diseases of various localization. Purpose - to evaluate the relationship between pathogenic properties and resistance to antimicrobial drugs (AMD) of Corynebacterium spp. from patients with inflammatory diseases of the respiratory tract. Strains of Corynebacterium spp. isolated from patients with inflammatory diseases of the respiratory tract (99 pcs.) and practically healthy individuals (33 pcs.). Isolates were identified by mass spectrometric method (MALDI-ToFMS), their adhesive and invasive activity on Hep-2 cells, cytopathic effect (CPE) in CHO-K1 cell culture, and resistance to antimicrobial drugs (AMD) were determined. Indicators of adhesion (3.65±0.679(CFU±m)x102/ml), invasion (1.72±0.230 (CFU±m)x102/ml), cytotoxicity (69.1±3.8% of dead CHO-K1 cells ) Corynebasterium spp. strains isolated from patients are higher (p≤0.05) than similar indicators in practically healthy people. 90.9% of isolates from patients had resistance to AMD, in most cases (57.6±4.9%) resistance to only one AMP was noted, less often to two (25.2±4.3%), three or more (8.08±2.7%). According to the results of correlation-regression analysis, pathogenic properties (adhesiveness, invasiveness, cytotoxicity) of Corynebacterium spp. strains isolated from patients are in close direct relationship with resistance to AMD. This indicates the importance of identifying strains of non-diphtheria corynebacteria resistant to AMDs, which, under the influence of developing resistance to AMDs, can increase their pathogenic potential, moving from commensalism to parasitism.

Etiological significance of Corynebacterium spp. in the development of diseases of the respiratory tract

Corynebacterium spp. It is associated with inflammatory diseases of the respiratory tract (tracheitis, pharyngitis, rhinosinusitis, bronchitis, pneumonia, etc.). C. pseudodiphtheriticum can be the causative agent of bacterial coinfection in patients with a new coronavirus infection (COVID-19). The aim is to determine the pathogenic properties and resistance to antimicrobial drugs of Corynebacterium spp. strains to establish their etiological significance in the development of inflammatory diseases of the respiratory tract. Strains of Corynebacterium spp. isolated from patients with inflammatory diseases of the respiratory tract (43 pcs.) and practically healthy individuals (29 pcs.). Isolates were identified by mass spectrometric method (MALDI-TOF MS), their cytopathic effect in CHO-K1 cell culture, hemolytic, urease activity, antimicrobial drug resistance were determined. Strains of Corynebacterium spp. isolated from patients in the amount of 105 CFU/ml or more, practically healthy - 104 CFU/ml or less. Isolates of Corynebacterium spp. patients had a more pronounced cytopathic effect (83.7±11.1%) and were more often resistant to antimicrobial drugs than those isolated from practically healthy. To establish the etiological significance of Corynebacterium spp. isolates. in the development of inflammatory diseases of the respiratory tract, it is advisable to determine their amount in biological material (105 CFU/ml or more), the cytopathic effect on CHO-K1 cell culture, as well as the presence of multiple resistance to antimicrobial drugs. Differences in the characteristics of Corynebacterium spp. isolates. from patients with respiratory tract pathology and practically healthy individuals are associated with the strain, not the species, of corynebacteria.

Corynebacterium pseudodiphtheriticum as a pathogen in bacterial co-infection in COVID-19 patients with mechanical ventilation

Many studies have been conducted on ventilator-associated complications (VACs) in COVID-19 patients. However, in these studies, the causative organisms were similar, and there are no reports on VAC corresponding with Corynebacteria. Coryneforms are frequently cultured in polymicrobial infections and are usually considered contaminants in respiratory specimens. However today, Corynebacterium pseudodiphtheriticum or striatum is known to be a pathogen in lower respiratory tract infection. We report three cases of VAC probably due to Corynebacterium pseudodiphtheriticum in COVID-19 patients. If purulent lower respiratory specimens showed coryneform predominantly via Gram staining, empirical therapy should be started. Furthermore, species identification and drug susceptibility testing should be performed.

Corynebacterium spp. - problematic pathogens of the human respiratory tract (review of literature)

Corynebacterium spp. - representatives of the normal microflora of the human body, but their role in the development of diseases in both immunocompromised and immunocompetent patients is known. Corynebacterim spp. (C. pseudodiphtheriticum, C. striatum, C. amycolatum, C. accolens, C. argentoratense, etc.) is associated with diseases of the respiratory tract: tracheitis, pharyngitis, rhinosinusitis, bronchitis, etc. They can be transmitted by airborne droplets, household contact, and possibly by hematogenic pathways. Corynebacterim spp. toxins do not produce, but are capable of adhesion and invasion, biofilm formation, production of neuraminidase, hyaluronidase, and hemolysin. It is necessary to take into account not so much the species, but the strain affiliation of isolates of Corynebacterium spp., since among the representatives of one species of non-diphtheria corynebacteria (for example, C. pseudodiphtheriticum), colonizing the respiratory tract, there may be strains that can exhibit not only pathogenic properties, but also probiotic activity. Microbiological diagnostics is based on their quantitative determination in biological material, phenotypic (culture study, test systems for biochemical identification, Vitek 2 automated systems) and genotypic (16SpRNA gene sequencing and rpoB) methods. It is possible to use mass spectrometric analysis (MALDI-ToF-MS). The greatest activity against Corynebacterium spp. in vitro studies preserve vancomycin, teicoplanin, and linezolid. Successful therapy with at least two of the following antimicrobial agents (AMP) has been reported: vancomycin, rifampicin, linezolid, and daptomycin. The sensitivity of isolates of Corynebacterium spp. to AMP is not related to the species, but is due to strain differences, and therefore it is necessary to test each isolated strain. Continuous monitoring of the sensitivity of Corynebacterium spp. strains to AMP is necessary due to the observed variability of these traits. Of particular importance is the identification of multidrug-resistant isolates that are currently considered highly pathogenic. When compiling the review, the databases Scopus, Web of Science, The Cochrane Library, CyberLeninka, RSCI were used.

Respiratory microbiome profiles differ by recent hospitalization and nursing home residence in patients on mechanical ventilation

Background

Healthcare-associated pneumonia (HCAP) is a heterogeneous disease. We redefined nursing-home- and hospital-associated infections (NHAI) group by revising existing HCAP risk factors. The NHAI group comprised nursing home residents with a poor functional status, or recent (past 90 days) hospitalization or recent (past 180 days) antibiotic therapy. Our aim was to determine whether respiratory microbiota profiles are related to newly defined NHAI group in critically ill patients on mechanical ventilation.

Methods

The 180 endotracheal aspirates (ETAs) from 60 mechanically ventilated ICU patients (NHAI group, n = 24; non-NHAI group, n = 36) were prospectively collected on days 1, 3 and 7 in a university hospital. The bacterial community profiles of the ETAs were explored by 16S rRNA gene sequencing. A phylogenetic-tree-based microbiome association test (TMAT), generalized linear mixed models (GLMMs), the Wilcoxon test and the reference frame method were used to analyze the association between microbiome abundance and disease phenotype.

Results

The relative abundance of the genus Corynebacterium was significantly higher in the pneumonia than in the non-pneumonia group. The microbiome analysis revealed significantly lower α-diversity in the NHAI group than in the non-NHAI group. In the analysis of β-diversity, the structure of the microbiome also differed significantly between the two groups (weighted UniFrac distance, Adonis, p < 0.001). The abundance of Corynebacterium was significantly higher, and the relative abundances of Granulicatella, Staphylococcus, Streptococcus and Veillonella were significantly lower, in the NHAI group than in the non-NHAI group.

Conclusions

The microbiota signature of the ETAs distinguished between patients with and without risk factors for NHAI. The lung microbiome may serve as a therapeutic target for NHAI group.

An autopsy case of ventilator-associated tracheobronchitis caused by Corynebacterium species complicated with diffuse alveolar damage

Ventilator-associated tracheobronchitis (VAT) has been reported to occur in 11% of intubated patients. Corynebacterium spp. can cause lower respiratory infections; however, to our knowledge, there have been no reported cases of VAT caused by Corynebacterium spp. A 55-year-old man was hospitalized with acute respiratory failure after autologous peripheral blood stem cell transplantation for Hodgkin lymphoma. Chest computed tomography showed diffuse ground-glass opacities in both lung fields. A few days after tracheal intubation, steroid pulse, and antibacterial drugs, the patient's pulmonary involvement temporarily improved. However, these opacities rapidly deteriorated, leading to death about 2 weeks after hospitalization. No significant bacteria other than Corynebacterium spp. were detected in sputum cultures during treatment and in blood culture at autopsy. Histological findings revealed tracheitis and diffuse alveolar damage. According to these findings, we diagnosed the patient as having VAT caused by Corynebacterium spp. This report suggests that Corynebacterium spp. might be an important causative pathogen of VAT in immunodeficient patients who undergo tracheal intubation. Additionally, optimal treatment for Corynebacterium spp. must be determined.