Genomic characterization of cocirculating Corynebacterium diphtheriae and non-diphtheritic Corynebacterium species among forcibly displaced Myanmar nationals, 2017-2019

Respiratory diphtheria is a serious infection caused by toxigenic Corynebacterium diphtheriae, and disease transmission mainly occurs through respiratory droplets. Between 2017 and 2019, a large diphtheria outbreak among forcibly displaced Myanmar nationals densely settled in Bangladesh was investigated. Here we utilized whole-genome sequencing (WGS) to characterize recovered isolates of C. diphtheriae and two co-circulating non-diphtheritic Corynebacterium (NDC) species - C. pseudodiphtheriticum and C. propinquum. C. diphtheriae isolates recovered from all 53 positive cases in this study were identified as toxigenic biovar mitis, exhibiting intermediate resistance to penicillin, and formed four phylogenetic clusters circulating among multiple refugee camps. Additional sequenced isolates collected from two patients showed co-colonization with non-toxigenic C. diphtheriae biovar gravis, one of which exhibited decreased susceptibility to the first-line antibiotics and harboured a novel 23-kb multidrug resistance plasmid. Results of phylogenetic reconstruction and virulence-related gene contents of the recovered NDC isolates indicated they were likely commensal organisms, though 80.4 %(45/56) were not susceptible to erythromycin, and most showed high minimum inhibition concentrations against azithromycin. These results demonstrate the high resolution with which WGS can aid molecular investigation of diphtheria outbreaks, through the quantification of bacterial genetic relatedness, as well as the detection of virulence factors and antibiotic resistance markers among case isolates.

Phylogenetic analyses of antimicrobial resistant Corynebacterium striatum strains isolated from a nosocomial outbreak in a tertiary hospital in China

Corynebacterium striatum is an emerging, multidrug-resistant pathogen that frequently causes nosocomial infections worldwide. This study aimed to investigate phylogenetic relationship and presence of genes responsible for antimicrobial resistance among C. striatum strains associated with an outbreak at the Shanxi Bethune Hospital, China, in 2021. Fecal samples were collected from 65 patients with C. striatum infection at Shanxi Bethune Hospital between February 12, 2021 and April 12, 2021. C. striatum isolates were identified by 16S rRNA and rpoB gene sequencing. E-test strips were used to examine the antimicrobial susceptibility of the isolates. Whole-genome sequencing and bioinformatics analysis were employed to assess the genomic features and identify antimicrobial resistance genes of the isolates. Crystal violet staining was conducted to determine the ability of biofilm formation of each isolate. A total of 64 C. striatum isolates were identified and categorized into 4 clades based on single nucleotide polymorphisms. All isolates were resistant to penicillin, meropenem, ceftriaxone, and ciprofloxacin but susceptible to vancomycin and linezolid. Most isolates were also resistant to tetracycline, clindamycin, and erythromycin, with susceptibility rates of 10.77, 4.62, and 7.69%, respectively. Genomic analysis revealed 14 antimicrobial resistance genes in the isolates, including tetW, ermX, and sul1. Crystal violet staining showed that all isolates formed biofilms on the abiotic surface. Four clades of multidrug-resistant C. striatum spread in our hospitals possibly due to the acquisition of antimicrobial resistance genes.

Leger AJ. Genetic Manipulation of Corynebacterium mastitidis to Better Understand the Ocular Microbiome

Purpose

Corynebacterium spp. are Gram-positive bacteria commonly associated with the ocular surface. Corynebacterium mastitidis was isolated from mouse eyes and was demonstrated to induce a beneficial immune response that can protect the eye from pathogenic infection. Because eye-relevant Corynebacterium spp. are not well described, we generated a C. mast transposon (Tn) mutant library to gain a better understanding of the nature of eye-colonizing bacteria.

Methods

Tn mutagenesis was performed with a custom Tn5-based transposon that incorporated a promoterless gene for the fluorescent protein mCherry. We screened our library using flow cytometry and enzymatic assays to identify useful mutants that demonstrate the utility of our approach.

Results

Fluorescence-activated cell sorting (FACS) of mCherry+ bacteria allowed us to identify a highly fluorescent mutant that was detectable on the murine ocular surface using microscopy. We also identified a functional knockout that was unable to hydrolyze urea, UreaseKO. Although uric acid is an antimicrobial factor produced in tears, UreaseKO bacterium maintained an ability to colonize the eye, suggesting that urea hydrolysis is not required for colonization. In vitro and in vivo, both mutants maintained the potential to stimulate protective immunity as compared to wild-type C. mast.

Conclusions

In sum, we describe a method to genetically modify an eye-colonizing microbe, C. mast. Furthermore, the procedures outlined here will allow for the continued development of genetic tools for modifying ocular Corynebacterium spp., which will lead to a more complete understanding of the interactions between the microbiome and host immunity at the ocular surface.

Complete Genome Sequences of Four Macrolide-Resistant Nondiphtheritic Corynebacterium Isolates

This report describes the complete genome sequences of four isolates of the nondiphtheritic Corynebacterium (NDC) species Corynebacterium pseudodiphtheriticum and Corynebacterium propinquum, recovered during investigation of a large diphtheria outbreak in Bangladesh. These data will assist in better delineating the boundary between these related species and understanding their virulence potential.

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 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.

Corynebacterium Species of the Conjunctiva and Nose: Dominant Species and Species-Related Differences of Antibiotic Susceptibility Profiles

PURPOSE

Nondiphtherial Corynebacterium species are normal residents of human skin and mucosa, including the conjunctiva and nose, but can cause conjunctivitis and keratitis. Recently, resistance against various classes of antibiotics has been reported in Corynebacterium. The present study investigated the type of species and antibiotic susceptibilities of the conjunctival and nasal Corynebacterium species.

METHODS

This study examined 183 strains of Corynebacterium species that were isolated from patients undergoing preoperative examinations for cataract surgery. Species were identified by RNA polymerase β-subunit-encoding gene (rpoB) sequencing. Antibiotic susceptibility tests were performed by the microdilution method according to the Clinical and Laboratory Standards Institute standard method M45.

RESULTS

Corynebacterium macginleyi was the most predominant species (84%; 46 of 55) in the conjunctiva. The 2 major species in the nasal cavity were Corynebacterium accolens and Corynebacterium propinquum (44% and 31%, respectively), followed by Corynebacterium pseudodiphtheriticum (8%), Corynebacterium jeikeium (7%), and C. macginleyi (3%). In contrast to other nasal Corynebacterium species, only C. macginleyi showed a high susceptibility to macrolides. However, among nonconjunctival Corynebacterium species, C. propinquum, was unique in having a high resistance rate to levofloxacin (29%), comparable with that observed in C. macginleyi (36%). Penicillin G and tobramycin showed good susceptibility in almost all strains.

CONCLUSIONS

Drug resistance against fluoroquinolones and macrolides was observed in Corynebacterium species, with the antibiotic susceptibility profiles correlating with differences of the species and niche. Nasal and conjunctival Corynebacterium profiles of drug resistance suggest habitat segregation strictly at the species level.

Case Report: About a Case of Hyperammonemia Syndrome Following Lung Transplantation: Could Metagenomic Next-Generation Sequencing Improve the Clinical Management?

Background: Mycoplasma hominis and Ureaplasma spp. are responsible for opportunistic infections in transplant patients, sometimes causing a life-threatening hyperammonemia syndrome. Both pathogens are not identified with standard microbiology techniques, resulting in missed or delayed diagnosis. We present a clinical case that illustrates the added value that next-generation sequencing (NGS) may offer in the diagnosis of respiratory infections in immune-compromised patients. Results: A 55 years-old man with idiopathic pulmonary fibrosis underwent double lung transplantation. He received antibiotic prophylaxis with piperacillin-tazobactam and azythromycin. At day 4 post-transplantation (PTx), the patient presented an acute respiratory distress. A broncho-alveolar lavage (BAL) was performed. At day 5 PTx, the patient presented a status epilepticus due to diffuse cerebral oedema. Serum ammonia concentration was 661 μg/dL. BAL bacterial culture was negative. Because of the clinical presentation, special cultures were performed and identified 100.000 CFU/mL of M. hominis and Ureaplasma spp. and specific PCRs were positive for M. hominis and Ureaplasma parvum. Antibiotic therapy was shifted to therapeutic dose of azithromycin and doxycycline; within 48 h ammonia serum concentrations returned to normal but the coma persisted several weeks, followed by a persistent frontal lobe syndrome. A follow-up BAL was performed on day 11 Ptx. The Mycoplasma/Ureaplasma culture was negative, yet the specific PCRs remained positive. Bacterial culture found 100 CFU/mL of Staphylococcus aureus and viral culture was positive for Herpes Simplex Virus-1. These results were confirmed by metagenomic next-generation sequencing (mNGS). In the bacterial fraction, the majority of reads belonged to Corynebacterium propinquum (34.7%), S. aureus (24.1%) and Staphylococcus epidermidis (17.1%). Reads assigned to M. hominis, Ureaplasma urealyticum and parvum represented 0.71, 0.13, and 0.04% of the bacterial fraction and corresponded to 6.9 × 10³, 9.7 × 10², and 3.7 × 10² genome equivalents per mL of BAL fluid, respectively. These results are in favor of a cure of the atypical infection. Conclusions: mNGS offered added diagnostic and quantitative values compared to PCR tests, which can remain positive after resolved infections. The initiation of appropriate antibiotic therapy would have occurred earlier on, possibly resulting in a better clinical outcome if mNGS had been performed in a routine fashion.

Worldwide survey of Corynebacterium striatum increasingly associated with human invasive infections, nosocomial outbreak, and antimicrobial multidrug-resistance, 1976-2020

Corynebacterium striatum is part of microbiota of skin and nasal mucosa of humans and has been increasingly reported as the etiologic agent of community-acquired and nosocomial diseases. Antimicrobial multidrug-resistant (MDR) C. striatum strains have been increasingly related to various nosocomial diseases and/or outbreaks worldwide, including fatal invasive infections in immunosuppressed and immunocompetent patients. Although cases of infections by C. striatum still neglected in some countries, the improvement of microbiological techniques and studies led to the increase of survival of patients with C. striatum nosocomial infections at different levels of magnitude. Biofilm formation on abiotic surfaces contributes for the persistence of virulent C. striatum and dissemination of antimicrobial resistance in hospital environment. Besides that, empirical antibiotic therapy can select multi-resistant strains and transfer intra and interspecies genes horizontally. In this study, a worldwide survey of C. striatum human infections and nosocomial outbreaks was accomplished by the analysis of clinical–epidemiological and microbiological features of reported cases from varied countries, during a 44-year period (1976–2020).

Current Evidence for Corynebacterium on the Ocular Surface

Corynebacterium species are commonly found in the conjunctiva of healthy adults and are recognized as non-pathogenic bacteria. In recent years, however, Corynebacterium species have been reported to be potentially pathogenic in various tissues. We investigated Corynebacterium species on the ocular surface and reviewed various species of Corynebacterium in terms of their antimicrobial susceptibility and the underlying molecular resistance mechanisms. We identified a risk for Corynebacterium-related ocular infections in patients with poor immunity, such as patients with diabetes or long-term users of topical steroids, and in those with corneal epithelial damage due to trauma, contact lens wear, lagophthalmos, and trichiasis. The predominant strain in the conjunctiva was C. macginleyi, and the species associated with keratitis and conjunctivitis were C. macginleyi, C. propinquum, C. mastitidis, C. pseudodiphtheriticum, C. accolens, C. striatum, C. xerosis, and C. bovis. Overall, Corynebacterium species present on the ocular surface were resistant to quinolones, whereas those in the nasal cavity were more susceptible. The prevalence of fluoroquinolone-resistant Corynebacterium has not changed in the past 10 years; however, Corynebacterium species remain susceptible to third-generation cephems. In conclusion, the use of third-generation cephems should be a reasonable and pragmatic approach for treatment of ocular infections caused by Corynebacterium species.

Contact Lens-Related Infectious Keratitis with White Plaque Formation Caused by Corynebacterium propinquum

We report the first case of Corynebacterium propinquum keratitis in the compromised cornea of a diabetic patient wearing therapeutic contact lenses. The strain was identified to the species level based on sequencing of the 16S rRNA gene and RNA polymerase β-subunit-encoding gene (rpoB). Ophthalmologists should be aware of nondiphtherial corynebacterial infection of compromised corneas.