Virulence potential of the first Corynebacterium mycetoides strain isolated from human urine: a rare species of Corynebacterium.

For many years, the potential pathogenic of non-diphtheriae corynebacteria were underestimated. Nowadays, a growing number of Corynebacterium species are recognized as opportunistic agents of human infections, mainly in hospital settings. In addition, multidrug-resistant Corynebacterium isolates from clinical specimens, have been reported and the role of Corynebacterium spp. in urinary tract infections (UTIs) has been highlighted. Several studies have reported Corynebacterium species as the agent of UTIs especially in patients with risk factors. Thus, the present work aimed to report the first isolation of Corynebacterium mycetoides from human urine and an initial study on its virulence properties. The isolate, initially characterized by phenotypical tests as a multidrug-resistant Corynebacterium sp., was recovered from the urine of a female transplant patient. Mass spectrometry and 16S rRNA and rpoB genes sequencing identified the isolate as C. mycetoides. The isolate was found able to adhere to and survive into epithelial cells (Vero cells), and its pathogenic potential was confirmed when tested against Caenorhabditis elegans nematode. The results obtained suggest that C. mycetoides is a potential pathogen for the urinary tract in humans and for a better understanding of the multifactorial mechanisms of virulence, studies about this species should be continued.

Insights of OxyR role in mechanisms of host-pathogen interaction of Corynebacterium diphtheriae.

Corynebacterium diphtheriae, the leading causing agent of diphtheria, has been increasingly related to invasive diseases, including sepsis, endocarditis, pneumonia, and osteomyelitis. Oxidative stress defense is required not only for successful growth and survival under environmental conditions but also in the regulation of virulence mechanisms of human pathogenic species, by promoting mucosal colonization, survival, dissemination, and defense against the innate immune system. OxyR, functioning as a negative and/or positive transcriptional regulator, has been included among the major bacterial coordinators of antioxidant response. OxyR was first reported as a repressor of catalase expression in C. diphtheriae. However, the involvement of OxyR in C. diphtheriae pathogenesis remains unclear. Accordingly, this work aimed to investigate the role of OxyR in mechanisms of host-pathogen interaction of C. diphtheriae through the disruption of the OxyR of the diphtheria toxin (DT)-producing C. diphtheriae CDC-E8392 strain. The effects of OxyR gene disruption were analyzed through interaction assays with human epithelial cell lines (HEp-2 and pneumocytes A549) and by the induction of experimental infections in Caenorhabditis elegans nematodes and Swiss Webster mice. The OxyR disruption exerted influence on NO production and mechanism accountable for the expression of the aggregative-adherence pattern (AA) expressed by CDC-E8392 strain on human epithelial HEp-2 cells. Moreover, invasive potential and intracytoplasmic survival within HEp-2 cells, as well as the arthritogenic potential in mice, were found affected by the OxyR disruption. In conclusion, data suggest that OxyR is implicated in mechanisms of host-pathogen interaction of C. diphtheriae.

Virulence potential of Corynebacterium striatum towards Caenorhabditis elegans.

Corynebacterium striatum strains have been increasingly reported as etiological agents of nosocomial infections and outbreaks in industrialized and developing countries. However, there are few studies focused on the virulence potential of C. striatum. A growing body of research supports the use of Caenorhabditis elegans as a model host for investigating the virulence potential of pathogenic bacteria, including corynebacteria. In the present study, chemotaxis behaviour, mortality, and morphological changes were investigated in nematodes infected by four C. striatum strains isolated from different clinical sites, and with different MDR profiles and PFGE types. The results showed chemotaxis of nematodes towards C. striatum. Nematode death (> 60%) was detected from the first day post-infection with all strains tested, but at different levels, independent of biofilm formation on catheter surfaces and differences in growth temperature between nematodes (20 °C) and mammals (37 °C). C. striatum 2369/II multidrug-resistant (MDR; from tracheal aspirate of a patient undergoing endotracheal intubation) and 1961/III multidrug-sensitive (MDS; urine) strains led to 100% mortality in worms. Survival of nematodes was observed until 4 days post-infection with the C. striatum 1954/IV MDS strain isolated from a surgical wound (13%) and 1987/I MDR strain isolated from a patient with a lower respiratory tract infection (39%). The Dar phenotype was observed post-infection with all MDS and MDR strains except 1954/IV. All strains showed the capacity for bagging formation. Star formation was observed only with strains that led to 100% nematode mortality. In conclusion, C. striatum was found to exert virulence for C. elegans. Variations in nematode morphological changes and levels of mortality indicate differences in the virulence potential of C. striatum independent of clinical isolation site, capacity for biofilm formation, and MDR and PFGE profiles.

Detection and virulence potential of a phospholipase D-negative Corynebacterium ulcerans from a concurrent diphtheria and infectious mononucleosis case.

Diphtheria by Corynebacterium ulcerans is increasingly occurring in children, adolescents and adults. In addition to diphtheria toxin (DT), phospholipase D (PLD) is considered a virulence factor of C. ulcerans. In the present study, a first case of concurrent diphtheria by a PLD-negative C. ulcerans and infectious mononucleosis (IM) was verified. Clinical and microbiological profiles and binding properties to human Fibrinogen (Fbg), Fibronectin (Fn) and type I collagen (col I) biotinylated proteins and virulence to Caenorhabditis elegans were investigated for C. ulcerans strain 2590 (clinical isolate) and two control strains, including PLD-positive BR-AD22 wild type and PLD-negative ELHA-1 PLD mutant strains. MALDI-TOF assays and a multiplex PCR of genes coding for potentially toxigenic corynebacteria identified strain 2590 as non-DT producing. Interestingly, strain 2590 did not express PLD activity in the CAMP test although the presence of the pld gene was verified. PLD-negative 2590 and a PLD-positive 210932 strains showed similar affinity to Fbg, Fn and type I collagen. C. elegans were able to escape from C. ulcerans strains, independent of PLD and DT production. Higher mortality of nematodes was verified for PLD-negative strains. Additional studies concerning multifactorial virulence potential of C. ulcerans, including environmental conditions remain necessary.

Caenorhabditis elegans star formation and negative chemotaxis induced by infection with corynebacteria.

Caenorhabditis elegans is one of the major model systems in biology based on advantageous properties such as short life span, transparency, genetic tractability and ease of culture using an Escherichia coli diet. In its natural habitat, compost and rotting plant material, this nematode lives on bacteria. However, C. elegans is a predator of bacteria, but can also be infected by nematopathogenic coryneform bacteria such Microbacterium and Leucobacter species, which display intriguing and diverse modes of pathogenicity. Depending on the nematode pathogen, aggregates of worms, termed worm-stars, can be formed, or severe rectal swelling, so-called Dar formation, can be induced. Using the human and animal pathogens Corynebacterium diphtheriae and Corynebacterium ulcerans as well as the non-pathogenic species Corynebacterium glutamicum, we show that these coryneform bacteria can also induce star formation slowly in worms, as well as a severe tail-swelling phenotype. While C. glutamicum had a significant, but minor influence on survival of C. elegans, nematodes were killed after infection with C. diphtheriae and C. ulcerans. The two pathogenic species were avoided by the nematodes and induced aversive learning in C. elegans.

Cutaneous abscess caused by Corynebacterium lactis in a companion dog.

Many new, emerging and re-emerging diseases of humans are caused by pathogens which originate from animals or products of animal origin. Corynebacterium lactis, a recently described species of the genus Corynebacterium, was first isolated from milk of asymptomatic cows. In the present study a cutaneous abscess caused by C. lactis in a dog was recognized by cytologic and histologic examination in addition to 16S rRNA gene analysis of the microorganism. Therefore, C. lactis should be included among other bacterial species recognized as emerging pathogens for companion animals.

Corynebacterium ulcerans isolates from humans and dogs: fibrinogen, fibronectin and collagen-binding, antimicrobial and PFGE profiles.

Corynebacterium ulcerans has been increasingly isolated as an emerging zoonotic agent of diphtheria and other infections from companion animals. Since pets are able to act as symptomless carriers, it is also essential to identify virulence potential for humans of these isolates. In this work the ability of C. ulcerans to bind to fibrinogen (Fbg), fibronectin (Fn) and Type I collagen as well the genetic relationship among strains isolated from human and asymptomatic dogs in Rio de Janeiro (Brazil) were analyzed. Five pulsed-field gel electrophoresis (PFGE) profiles were demonstrated (I, II, III, IV and V). In addition, the IV and V profiles exhibiting ≥85 % similarity were expressed by the BR-AD41 and BR-AD61 strains from companion dogs living in the same neighborhood. Independent of the PFGE-types, human and dog isolates showed affinity to Fbg, Fn and collagen. Heterogeneity of PFGE profiles indicated endemicity of C. ulcerans in the Rio de Janeiro metropolitan area. Differences in the expression of adhesins to the human extracellular matrix may contribute to variations in the virulence and zoonotic potential of C. ulcerans strains.