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

Exudative pharyngitis and Corynebacterium pseudodiphtheriticum: A case report and review of the literature

Corynebacterium pseudodiphtheriticum is an established member of the normal flora of the respiratory tract. This organism is an emerging cause of respiratory tract infection, as well as infection of the skin and skin structures, urinary tract and other sterile sites. The syndrome of C. pseudodiphtheriticum exudative pharyngitis is a diagnostic challenge of particular relevance in recent times as this organism can be confused with Corynebacterium diphtheriae in the clinical setting and in the laboratory. We report a case of exudative pharyngitis, possibly due to C. pseudodiphtheriticum, in a 14-month old, incompletely vaccinated, human immunodeficiency virus (HIV)-positive infant and review the role of this organism in terms of its microbiological profile and identification, disease spectrum and antimicrobial susceptibility pattern.

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.

Emendation of the description of the species Corynebacterium propinquum to include strains which produce urease

Corynebacterium propinquum is a Gram-positive rod occasionally recovered from clinical infections which, according to 16S rRNA gene sequencing, is most closely related (>99 % sequence similarity) to Corynebacterium pseudodiphtheriticum . The two species are very similar biochemically, commonly differentiated by a single test, the detection of urease, where strains of C. propinquum are described as being urease-non-producing and strains of C. pseudodiphtheriticum are described as urease-producing. In this study, historical and contemporary strains of C. propinquum and C. pseudodiphtheriticum from this laboratory were definitively characterized, which included use of rpoB sequencing. Urease-producing strains of C. propinquum as well as typical urease-non-producing isolates were identified after rpoB sequencing, with six of these being originally identified as C. pseudodiphtheriticum . Based on these observations, we propose emendation of the description of C. propinquum to include strains which produce urease. MALDI-TOF analysis may be a useful tool to differentiate these taxa. Existing commercial databases should be updated to include urease-positive strains of C. propinquum .

Aggregative adherent strains of Corynebacterium pseudodiphtheriticum enter and survive within HEp-2 epithelial cells

Corynebacterium pseudodiphtheriticum is a well-known human pathogen that mainly causes respiratory disease and is associated with high mortality in compromised hosts. Little is known about the virulence factors and pathogenesis of C. pseudodiphtheriticum. In this study, cultured human epithelial (HEp-2) cells were used to analyse the adherence pattern, internalisation and intracellular survival of the ATCC 10700 type strain and two additional clinical isolates. These microorganisms exhibited an aggregative adherence-like pattern to HEp-2 cells characterised by clumps of bacteria with a "stacked-brick" appearance. The differences in the ability of these microorganisms to invade and survive within HEp-2 cells and replicate in the extracellular environment up to 24 h post infection were evaluated. The fluorescent actin staining test demonstrated that actin polymerisation is involved in the internalisation of the C. pseudodiphtheriticum strains. The depolymerisation of microfilaments by cytochalasin E significantly reduced the internalisation of C. pseudodiphtheriticum by HEp-2 cells. Bacterial internalisation and cytoskeletal rearrangement seemed to be partially triggered by the activation of tyrosine kinase activity. Although C. pseudodiphtheriticum strains did not demonstrate an ability to replicate intracellularly, HEp-2 cells were unable to fully clear the pathogen within 24 h. These characteristics may explain how some C. pseudodiphtheriticum strains cause severe infection in human patients.

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.

A program against bacterial bioterrorism: improved patient management and acquisition of new knowledge on infectious diseases

In 2002 it was decided to establish laboratory facilities in Denmark for diagnosing agents associated with bioterrorism in order to make an immediate appropriate response to the release of such agents possible. Molecular assays for detection of specific agents and molecular and proteomic techniques for identification of bacteria were introduced as part of the program. All assays and techniques were made accessible for use in diagnosing patients, even when an intentional release was not suspected. Medical expertise on different diseases was established at the department as an integrated part of the program. The analyses included PCR assays for specific bacteria, identification of isolated bacteria by DNA sequencing, detection and identification of bacteria in clinical sample material by universal bacterial PCR and DNA sequencing, and identification of bacteria by mass spectrometry. The established analyses formed a basis on which a series of further developments was built. In addition to reducing the time for obtaining diagnoses and improving the accuracy of diagnosis of individual infected patients, the analyses provided new knowledge on the frequency and distribution of some bacterial infections, including Q fever, tularemia, trench fever, brucellosis, and melioidosis. The implementation of an antibioterrorism program in a clinical diagnostic setting improved the diagnostic possibilities for patients in Denmark and provided new epidemiologic information. It also introduced a number of diagnostic assays for bacterial infections not associated with bioterrorism that are difficult to culture or identify.

Evaluation of DNA extraction methods and their clinical application for direct detection of causative bacteria in continuous ambulatory peritoneal dialysis culture fluids from patients with peritonitis by using broad-range PCR

Background

The aims of this study were to compare several DNA extraction methods and 16S rDNA primers and to evaluate the clinical utility of broad-range PCR in continuous ambulatory peritoneal dialysis (CAPD) culture fluids.

Methods

Six type strains were used as model organisms in dilutions from 10⁸ to 10⁰ colony-forming units (CFU)/mL for the evaluation of 5 DNA extraction methods and 5 PCR primer pairs. Broad-range PCR was applied to 100 CAPD culture fluids, and the results were compared with conventional culture results.

Results

There were some differences between the various DNA extraction methods and primer sets with regard to the detection limits. The InstaGene Matrix (Bio-Rad Laboratories, USA) and Exgene Clinic SV kits (GeneAll Biotechnology Co. Ltd, Korea) seem to have higher sensitivities than the others. The results of broad-range PCR were concordant with the results from culture in 97% of all cases (97/100). Two culture-positive cases that were broad-range PCR-negative were identified as Candida albicans, and 1 PCR-positive but culture-negative sample was identified as Bacillus circulans by sequencing. Two samples among 54 broad-range PCR-positive products could not be sequenced.

Conclusions

There were differences in the analytical sensitivity of various DNA extraction methods and primers for broad-range PCR. The broad-range PCR assay can be used to detect bacterial pathogens in CAPD culture fluid as a supplement to culture methods.

Routine ribosomal PCR and DNA sequencing for detection and identification of bacteria

Detection and identification of bacteria by PCR and DNA sequencing from clinical sample material has been introduced as a diagnostic routine analysis during the last 5–10 years. Assays analyzing ribosomal genes have been found to be particularly useful. The technique has identified unusual bacteria as well as well-known bacteria in unusual infectious foci. Thereby, it has proven its value both in diagnosing infections in individual patients and as a tool to establish the pathogenic potential of bacteria not previously associated with disease. To be of clinical relevance, results from ribosomal PCR and DNA sequencing must be obtained fast and at acceptable costs. Processing of a high number of samples by individual laboratories can ensure both speed and low price. By continued technical development and further investigations of its usefulness in various clinical settings ribosomal DNA sequencing will most probably become as common a part of clinical bacteriology as culture is today.

Usefulness of broad-range PCR for the diagnosis of osteoarticular infections

PURPOSE OF REVIEW

Conventional methods such as microbiological cultures may lack the sensitivity and specificity to establish definitive diagnosis of osteoarticular infections. Herein, we review the general principles and the usefulness of broad-range PCR to improve the etiological diagnosis of osteoarticular infections.

RECENT FINDINGS

Broad-range PCR followed by sequencing has been successfully developed to identify microorganisms involved in infections when patients have previously received antibiotics or in the presence of slow-growing or intracellular microorganisms. For osteoarticular infections, the studies have shown that the use of this molecular tool increased mainly the identification of Kingella kingae, anaerobic bacteria, and Streptococcus spp. However, it is very important to underline that the interpretation of this molecular tool is critical because of several pitfalls, including contamination causing false-positive results.

SUMMARY

Broad-range PCR followed by sequencing offers several advantages when used to complement culture results for the diagnosis of fastidious bacteria and for patients taking antibiotics. However, its use should be restricted mainly for culture-negative cases when infection is suspected on the basis of clinical signs and symptoms or inflammatory syndrome. Future developments will include the use of real-time PCR in a closed system and pathogen-specific PCR for the molecular diagnosis of osteoarticular infections.

Inhibitor-free DNA for real-time PCR analysis of synovial fluid from horses, cattle and pigs

The potential of five different commercial DNA isolation methods to remove real-time PCR inhibitors from the synovial fluid of horses, cattle and pigs was investigated. All kits with the exception of one included a silica column-based purification of the DNA. With the fifth kit, DNA purification is achieved by removing contaminating macromolecules by a desalting process. We used a recently developed method based on comparison of the real-time PCR signal of an artificial target incorporated into each PCR reaction in the presence of the isolated DNA from the sample, and in control samples containing water instead of isolated DNA. This was followed by statistical analysis of the data. Inhibition and subsequent reduction of the endpoint fluorescence in the real-time PCR reaction was encountered in many cases. Less frequently, the target copy number in the samples was underestimated. However, we found no experimental evidence of a negative influence of the reduced endpoint fluorescence signal on the detection limit of the real-time PCR assay. All kits tested were useful for analyzing pelleted synovial fluid from horses, cattle and pigs. When analyzing non-pelleted synovial fluid, three kits - two based on silica columns and one employing a desalting process - yielded inhibitor-free DNA for real-time PCR analysis.