Corynebacterium pseudodiphtheriticum pulmonary infection in AIDS patients

Investigation of a Large Diphtheria Outbreak and Cocirculation of Corynebacterium pseudodiphtheriticum Among Forcibly Displaced Myanmar Nationals, 2017-2019

BACKGROUND

Diphtheria, a life-threatening respiratory disease, is caused mainly by toxin-producing strains of Corynebacterium diphtheriae, while nontoxigenic corynebacteria (eg, Corynebacterium pseudodiphtheriticum) rarely causes diphtheria-like illness. Recently, global diphtheria outbreaks have resulted from breakdown of health care infrastructures, particularly in countries experiencing political conflict. This report summarizes a laboratory and epidemiological investigation of a diphtheria outbreak among forcibly displaced Myanmar nationals in Bangladesh.

METHODS

Specimens and clinical information were collected from patients presenting at diphtheria treatment centers. Swabs were tested for toxin gene (tox)-bearing C. diphtheriae by real-time polymerase chain reaction (RT-PCR) and culture. The isolation of another Corynebacterium species prompted further laboratory investigation.

RESULTS

Among 382 patients, 153 (40%) tested tox positive for C. diphtheriae by RT-PCR; 31 (20%) PCR-positive swabs were culture confirmed. RT-PCR revealed 78% (298/382) of patients tested positive for C. pseudodiphtheriticum. Of patients positive for only C. diphtheriae, 63% (17/27) had severe disease compared to 55% (69/126) positive for both Corynebacterium species, and 38% (66/172) for only C. pseudodiphtheriticum.

CONCLUSIONS

We report confirmation of a diphtheria outbreak and identification of a cocirculating Corynebacterium species. The high proportion of C. pseudodiphtheriticum codetection may explain why many suspected patients testing negative for C. diphtheriae presented with diphtheria-like symptoms.

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.

Corynebacteria as a cause of pulmonary infection: a case series and literature review

Background

In most cases of community-acquired pneumonia (CAP), an etiologic agent is not determined; the most common report from the microbiological evaluation of sputum cites “normal respiratory flora.” Non-diphtheria Corynebacterium spp., a component of this flora, is commonly viewed as a contaminant, but it may be the cause of pneumonia and the frequency with which it causes CAP may be underestimated.

Case presentations

This report present 3 cases of CAP in which Corynebacterium spp. was clearly the predominant isolate; identification was confirmed by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. Two cases were caused by C. propinquum and one by C. striatum. Two patients had a tracheostomy and one was on hemodialysis. Patients who received an appropriate antibiotic responded well.

Conclusion

When identified as the predominant isolate in sputum from a patient with CAP, Corynebacterium spp. should be considered as a potential cause of the infection. In cases with patients who have compromised airway clearance or who are immunocompromised, microaspiration may be responsible. While some Corynebacterium spp. are suspectible to antibiotics usually prescribed for CAP, others are susceptible only to vancomycin or aminoglycosides. Vancomycin is thus the appropriate empiric antibiotic, pending speciation and susceptibility test results. The number of reported cases with result of antibiotic susceptibility testing, however, remains limited, and further investigation is needed. Non-diphtheria Corynebacterium spp. represent a noteworthy clinical cause of pneumonia. Identification by Gram stain and as a predominant organism on culture demands careful consideration for management.

Draft Genome Sequence of Corynebacterium pseudodiphtheriticum Strain 090104 "Sokolov"

This report describes the first draft genome sequence of a Corynebacterium pseudodiphtheriticum strain. The information on the genome organization and putative gene products will assist in better understanding of the molecular mechanisms involved in the beneficial probiotic effects of this bacterium.

Corynebacterium pseudodiphtheriticum: an easily missed respiratory pathogen in HIV-infected patients

Despite being a well-known respiratory pathogen for immunocompromised patients, Corynebacterium pseudodiphtheriticum has uncommonly been reported to occur in persons with infection attributable to HIV virus. We report three cases of respiratory tract infection attributable to C. pseudodiphtheriticum in HIV-infected patients and review the four previous cases from the medical literature. All of them were male with a median CD4 lymphocyte count of 110 cells/mm3 (range, 18-198/mm3); five of the seven cases occurred in persons for whom AIDS was diagnosed previously. The onset of symptomatology was usually acute and the most common radiographic appearance was alveolar infiltrate (six patients) with cavitation (two patients) and pleural effusion (two patients). In five of the seven cases, C. pseudodiphtheriticum was isolated from bronchoscopic samples and in the remaining two cases was recovered from lung biopsy (one patient) and sputum (one patient). In the three patients reported herein and in one previous case from the medical literature, quantitative culturing of bronchoscopic samples obtained through either bronchoalveolar lavage or protected brush catheter procedures yielded more than 10(3) CFU/mL. All the strains tested were susceptible to penicillin and vancomycin. Resistance to macrolides was common. Recovery was observed in six of the seven patients. C. pseudodiphtheriticum should be regarded as a potential respiratory pathogen in HIV-infected patients. This infection presents late in the course of HIV disease and it seems to respond well to appropriate antibiotic treatment in most of the cases. This easily overlooked pathogen should be added to the list of organisms implicated in respiratory tract infections in this population.

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.