Seven patients with respiratory infections due to Corynebacterium pseudodiphtheriticum

Infection and colonization by Corynebacterium pseudodiphtheriticum: a 9-year observational study in a university central hospital

Despite constituting part of the human commensal flora, Corynebacterium pseudodiphtheriticum has been recognized as a potentially infectious agent, most frequently in immunocompromised patients or individuals with other morbidity factors, but significant association to comorbid states remains unproven. This study's purpose was to assess clinical significance, risk factors for infection and antimicrobial susceptibility of C. pseudodiphtheriticum isolates. A retrospective observational study was conducted. Relevance of isolation was determined by clinical, laboratory, and imaging criteria. Forty-nine isolates occurred in 47 episodes. Colonization was assumed in 12% and infection in 78%, of which 51% were nosocomial. Patients with infection were older, with male predominance; both age and gender were statistically significant (p < 0.05) between infection and colonization groups. Although dyslipidemia (58%), arterial hypertension (58%), invasive procedures (56%), and chronic lung disease (50%) were prevalent in the infection group, no comorbidity was a significant risk factor for infection compared with colonization. Charlson comorbidity index showed no statistically difference between groups. Mortality rate was 14% in infection. Respiratory samples were the main isolation product; all tested strains were susceptible to amoxicillin/clavulanate and vancomycin. Resistant strains were observed for clindamycin (77%) and erythromycin (48%). C. pseudodiphtheriticum isolation was associated with infection in most cases. Despite the high prevalence of comorbidities and invasive procedures, no factors other than age and gender were significantly associated with infection. Although C. pseudodiphtheriticum may constitute a contaminant or colonizer in clinical samples, positive cultures in patients with signs and symptoms consistent with infection should not be neglected.

Carriage of a Single Strain of Nontoxigenic Corynebacterium diphtheriae bv. Belfanti (Corynebacterium belfantii) in Four Patients with Cystic Fibrosis

Cystic fibrosis (CF) patients are commonly colonized by bacterial pathogens, which can induce persistent lung inflammation and may contribute to clinical deterioration. Colonization of CF patients and cross-transmission by Corynebacterium diphtheriae have not been reported so far. The aim of this article was to investigate the possibility of a cross-transmission of C. diphtheriae biovar Belfanti between four patients of a CF center. C. diphtheriae biovar Belfanti (now formally called C. belfantii) isolates were collected from four patients in a single CF care center over a period of 6 years and analyzed by microbiological methods and whole-genome sequencing. Epidemiological links among patients were investigated. Ten isolates were collected from 4 patients. Whole-genome sequencing of one isolate from each patient showed that a single strain was shared among them. In addition, one patient was found to have the same strain in two consecutive samplings performed 9 months apart. The strain was nontoxigenic and was susceptible to most antimicrobial agents. Ciprofloxacin resistance was observed in one patient. The idea of transmission of the strain among patients was supported by the occurrence of same-day visits to the CF center. This study demonstrated colonization of CF patients by C. diphtheriae biovar Belfanti (C. belfantii), and the data suggest persistence and transmission of a unique strain during at least 6 years in a single CF patient care center.

Two-stage arthroplasty for the treatment of chronic osteomyelitis after routine arthroscopic knee surgery

Corynebacterium pseudodiphtheriticum is a normal inhabitant of the upper respiratory tract and is rarely thought of as a true pathogen. Although this microorganism has been associated with respiratory complications, a few case reports have demonstrated its ability to cause orthopedic infections. A recent review of the literature was performed regarding this specific bacteria and its association with bone and joint infection. To the author's knowledge, the current case is the first reported case of chronic osteomyelitis from Corynebacterium pseudodiphtheriticum after arthroscopic knee surgery. Isolation of this bacterial species on routine microbial cultures has been proven to be challenging in prior studies. In the current case, difficulty isolating this bacterial species on routine cultures led to a significant delay in diagnosis, which ultimately resulted in end-stage joint destruction. Treatment of the infection was accomplished using a 2-stage total knee arthroplasty technique, with the initial placement of an articulated, antibiotic-loaded spacer followed by a subsequent conversion to total knee arthroplasty. This case serves as a useful reminder that clinically subtle infections can occur after minor orthopedic surgery. Surgeons must remain vigilant to render a timely diagnosis and avoid severe sequelae that can result from an undetected pathogen after arthroscopic surgery.

Outbreak of Corynebacterium pseudodiphtheriticum infection in cystic fibrosis patients, France

An increasing body of evidence indicates that nondiphtheria corynebacteria may be responsible for respiratory tract infections. We report an outbreak of Corynebacterium pseudodiphtheriticum infection in children with cystic fibrosis (CF). To identify 18 C. pseudodiphtheriticum strains isolated from 13 French children with CF, we used molecular methods (partial rpoB gene sequencing) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Clinical symptoms were exhibited by 10 children (76.9%), including cough, rhinitis, and lung exacerbations. The results of MALDI-TOF identification matched perfectly with those obtained from molecular identification. Retrospective analysis of sputum specimens by using specific real-time PCR showed that approximately 20% of children with CF were colonized with these bacteria, whereas children who did not have CF had negative test results. Our study reemphasizes the conclusion that correctly identifying bacteria at the species level facilitates detection of an outbreak of new or emerging infections in humans.

Macrolide, lincosamide, and streptogramin B-constitutive-type resistance in Corynebacterium pseudodiphtheriticum isolated from upper respiratory tract specimens

Corynebacterium pseudodiphtheriticum is commonly found in normal upper respiratory tract flora in humans. In certain conditions it can cause the opportunistic infections, especially in immunocompromised patients. In certain strains of Corynebacterium sp., the macrolide, lincosamide, and streptogramin B (MLSb) resistance mechanism related to the presence of the erm(X) gene was discovered; hence, the need appeared for further investigation to confirm the existence of this gene among C. pseudodiphtheriticum. About 58 strains of C. pseudodiphtheriticum were used in this study. All strains were isolated from the nasal mucous membrane of patients with upper respiratory tract infection symptoms. Among the tested strains 52 were erythromycin resistant, and only 6 were erythromycin sensitive. The tested strains showed a very high percentage (89.7%) of the phenotype MLSb-constitutive resistance mechanism. The MLSb-inducible resistance among the tested strains was not observed. Association of the MLSb mechanism with resistance to chloramphenicol, trimethoprim/sulfamethoxazole and chloramphenicol, and trimethoprim/sulfamethoxazole was observed in 12.1%, 15.5%, and 44.8% tested strains, respectively. Among all isolates with the phenotype MLSb resistance, the presence of the erm(X) gene was confirmed by the polymerase chain reaction method. The results suggest that C. pseudodiphtheriticum with the MLSb-constitutive-type resistance can play a significant role in crossing this mechanism with other Corynebacterium sp., which colonize the nasal and throat mucous membrane.

Demonstration by PCR and DNA sequencing of Corynebacterium pseudodiphtheriticum as a cause of joint infection and isolation of the same organism from a surface swab specimen from the patient

A case of infectious arthritis following arthroscopy is described. Real-time PCR, using universal bacterial primers targeting the 16S rRNA gene, and subsequent DNA sequencing of the PCR product demonstrated the presence of DNA from Corynebacterium pseudodiphtheriticum in the synovial fluid from the affected knee. Culture from a surface swab from the site of purulent discharge from the knee was initially reported as growing normal skin microbiota. Knowing the result of the DNA analysis, the specimen was re-examined and a diphtheroid bacterium was isolated. The DNA sequence of the isolated bacterium was identical to that of the DNA in the joint. The isolated bacterium was tested for susceptibility to relevant antibiotics. Demonstration and identification of bacterial DNA by PCR and gene sequencing may not by itself give information on important characteristics such as susceptibility to antibiotics of the infecting bacterium. The present case illustrates that the results obtained by the method can be used to isolate the relevant bacterium in culture from other sites and thereby characterize it. It furthermore demonstrates that C. pseudodiphtheriticum can cause severe arthritis when inoculated into joints.

Corynebacterium pseudodiphtheriticum keratitis and conjunctivitis: a case report

A case of keratitis and conjunctivitis in an 86-year-old man caused by Corynebacterium pseudodiphtheriticum is reported. Corynebacteria are uncommon causes of ocular surface infections. However, the presence of corneal and conjunctival epithelial defects in an immunocompromised patient can result in severe infection by a commensal organism such as C. pseudodiphtheriticum. The significance of a positive culture in these settings should not be overlooked.

Clinical microbiology of coryneform bacteria

Coryneform bacteria are aerobically growing, asporogenous, non-partially-acid-fast, gram-positive rods of irregular morphology. Within the last few years, there has been a massive increase in the number of publications related to all aspects of their clinical microbiology. Clinical microbiologists are often confronted with making identifications within this heterogeneous group as well as with considerations of the clinical significance of such isolates. This review provides comprehensive information on the identification of coryneform bacteria and outlines recent changes in taxonomy. The following genera are covered: Corynebacterium, Turicella, Arthrobacter, Brevibacterium, Dermabacter. Propionibacterium, Rothia, Exiguobacterium, Oerskovia, Cellulomonas, Sanguibacter, Microbacterium, Aureobacterium, "Corynebacterium aquaticum," Arcanobacterium, and Actinomyces. Case reports claiming disease associations of coryneform bacteria are critically reviewed. Minimal microbiological requirements for publications on disease associations of coryneform bacteria are proposed.

Exudative pharyngitis possibly due to Corynebacterium pseudodiphtheriticum, a new challenge in the differential diagnosis of diphtheria

Corynebacterium pseudodiphtheriticum has rarely been reported to cause disease in humans, despite its common presence in the flora of the upper respiratory tract. We report here a case of exudative pharyngitis with pseudomembrane possibly caused by C. pseudodiphtheriticum in a 4-year-old girl. The case initially triggered clinical and laboratory suspicion of diphtheria. Because C. pseudodiphtheriticum can be easily confused with Corynebacterium diphtheriae in Gram stain, clarification of its role in the pathogenesis of exudative pharyngitis in otherwise healthy persons is of public health importance. Simple and rapid screening tests to differentiate C. pseudodiphtheriticum from C. diphtheriae should be performed to prevent unnecessary concern in the community and unnecessary outbreak control measures.