Pseudoepidemic of Nocardia asteroides associated with a mycobacterial culture system

Evaluation of BACTEC MGIT 960 system for recovery of Nocardia from clinical specimens

Nocardia spp. is an aerobic Gram-positive bacillus responsible for nocardiosis. Herein, we performed a retrospective study to evaluate the performance of BACTEC MGIT 960 system, in comparison with smear microscopy and blood agar plate (BAP) culture, to recover Nocardia from different clinical specimens. Furthermore, the inhibitory effect of antibiotics contained in MGIT 960 tube on Nocardia was also evaluated. The sensitivities for Nocardia recovery using smear microscopy, BAP culture, and MGIT 960 were 39.4% (54/137), 46.1% (99/215), and 81.3% (156/192), respectively. N. farcinica was the most detected species (60.4%, 136/225). In MGIT 960-recovered Nocardia strains, N. farcinica accounted for 76.9%. Furthermore, trimethoprim in MGIT 960 tube inhibited less N. farcinica growth than that of other Nocardia species, partially explaining why MGIT 960 recovered more N. farcinica from sputa. The current study demonstrated that MGIT 960 could recover Nocardia strains from heavily-contaminated samples if its components and antibiotics are redesigned.

The hsp65 gene patterns of less common Mycobacterium and Nocardia spp. by polymerase chain reaction-restriction fragment length polymorphism analysis with capillary electrophoresis

To rapidly identify Mycobacterium and Nocardia spp. without costly probes, we had implemented capillary electrophoresis (CE) in polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analysis to analyze their 65-kDa heat shock protein (hsp65) gene. The PCR-RFLP analysis with CE (PRACE) involved only one restriction enzyme, HaeIII, and a single electrophoretic separation less than 10 min. Full-range (10-200 bp) RFLP patterns of 12 less common Mycobacterium and 7 Nocardia spp. were investigated. A good agreement was observed between the sizes of restriction fragments resolved by CE and the real sizes deduced from sequence analysis. Including hsp65 gene patterns of 12 Mycobacterium spp. published earlier, differentiation was distinct among 24 Mycobacterium and 7 Nocardia spp. Some closely related species exhibiting similar biochemical characteristics could be well discriminated by an extra HaeIII digestion site. Thus, PRACE offers a nonprobe alternative for rapid identification of various cultured Mycobacterium and Nocardia to the species level.

Clinical and laboratory features of the Nocardia spp. based on current molecular taxonomy

The recent explosion of newly described species of Nocardia results from the impact in the last decade of newer molecular technology, including PCR restriction enzyme analysis and 16S rRNA sequencing. These molecular techniques have revolutionized the identification of the nocardiae by providing rapid and accurate identification of recognized nocardiae and, at the same time, revealing new species and a number of yet-to-be-described species. There are currently more than 30 species of nocardiae of human clinical significance, with the majority of isolates being N. nova complex, N. abscessus, N. transvalensis complex, N. farcinica, N. asteroides type VI (N. cyriacigeorgica), and N. brasiliensis. These species cause a wide variety of diseases and have variable drug susceptibilities. Accurate identification often requires referral to a reference laboratory with molecular capabilities, as many newer species are genetically distinct from established species yet have few or no distinguishing phenotypic characteristics. Correct identification is important in deciding the clinical relevance of a species and in the clinical management and treatment of patients with nocardial disease. This review characterizes the currently known pathogenic species of Nocardia, including clinical disease, drug susceptibility, and methods of identification.

Biochemical Identification and Molecular Characterization (PCR-RFLP) of Nocardia Isolates from Sputum

BACKGROUND

Nocardia identification has been based on biochemical and morphological characteristics. However, molecular biology techniques allow a better characterization of species and biotypes that are related to invasive diseases.

METHODS

Twelve isolates of Nocardia spp. were obtained from sputum of patients with tuberculosis under retreatment. Identification was done based on morphological characteristics, biochemical tests (casein, tyrosine, xanthine, gelatin, and urea) and molecular biology techniques (PCR-RFLP) using restriction enzymes MspI, HinfI, BsaHI, HaeIII and BstEII.

RESULTS

Biochemical tests identified the 12 isolates as Nocardia asteroides. PCR-RFLP technique identified nine isolates to species and biotype level: five as N. asteroides type II, two as N. asteroides type VI, and two as N. asteroides type I. The remaining three isolates were identified as follows: one to species level as N. farcinica and two at genus level as Nocardia sp.

CONCLUSIONS

Significant statistical differences between the use of traditional techniques and PCR-RFLP were not found at genus level, but there were important differences at species and biotype level. Biochemical tests identified correctly the actinomycete isolates as belonging to Nocardia genus, but at N. asteroides complex level were not able to discern among their different species. PCR-RFLP is a rapid, non-expensive, and reliable method that allows to discriminate the N. asteroides complex species, identifying biotypes related to invasive disease. Our results suggest that the hospital environment was not a contamination source.

A case series and focused review of nocardiosis: clinical and microbiologic aspects

Nocardia species are ubiquitous soil organisms that often infect patients with underlying immune compromise, pulmonary disease, or a history of surgery or trauma. We report 5 cases of nocardiosis representing various aspects of this "great imitator": 1) pneumonia in the setting of underlying malignancy, 2) chronic pneumonia with drug-resistant organism, 3) bacteremia and empyema with chronic hematologic malignancy, 4) primary cutaneous disease, and 5) sternal wound infection. We present a summary of the English literature from 1966 to 2003 with a focus on the teaching points of each of our 5 cases as well as the background epidemiology and microbiology of the Nocardia genus. Isolation of the organism may be achieved with routine media but longer incubation times may be necessary, delaying diagnosis and appropriate therapy. Treatment with a sulfa-containing regimen is standard of care, but resistance testing is warranted given emerging drug resistance, high rates of discontinuation due to adverse reactions, and the potential for nephrotoxicity in transplant recipients on cyclosporine.

A pseudoepidemic of postoperative scleritis due to misdiagnosis

OBJECTIVE

To describe a pseudoepidemic of infectious scleritis following eye surgery.

METHODS

Retrospective cohort study with selected procedural and laboratory investigations.

RESULTS

Twenty-one patients with postoperative scleritis were identified during a 2-month outbreak. Neither an infectious etiology nor a causative pre-, intra-, or postoperative exposure was found. The clinical findings, when carefully reviewed, were consistent with poor surgical-wound closure.

CONCLUSIONS

The art of clinical diagnosis involves the subjective interpretation of clinical history, physical findings, and laboratory results. A repeated error in the interpretation of clinical findings can simulate an outbreak of disease. Clinicians may be reluctant to concede misdiagnosis.

Vancomycin-Resistant Enterococcus: Infectious Endocarditis Treatment

Vancomycin-resistant Enterococcus species represent serious gram-positive pathogens for which there is currently no recommended therapy. There are a number of new antibiotics with activity against these pathogens in development. Although there is a great deal of experience with some of these agents for skin and soft tissue infections, bacteremia, pneumonia, and intra-abdominal infections, there is currently little information available for the treatment of endocarditis. Animal and limited human data thus far suggest that new agents such as quinuprisitin-dalfopristin, LY333328 (a new glycopeptide antibiotic), and daptomycin (a lipopeptide antibiotic) may prove useful for this indication. Additional information, and especially combination treatment, are warranted to improve success and limit the emergence of resistance to these new antibiotics.

Nocardia bacteremia. Report of 4 cases and review of the literature

Bacteremic nocardiosis is reported rarely. We discuss 4 recent cases seen at our institution and 32 other cases described in the English literature. We found that patients with bacteremic nocardiosis were similar in presentation, risk factors, course, and therapeutic outcome to nonbacteremic patients with nocardiosis. The presence of endovascular foreign bodies appeared to be the only unique risk factor associated with bacteremic illness. Seeding of the central nervous system appeared to be relatively uncommon. Thirty percent of patients with nocardemia had concomitant bacteremia with other pathogens, mostly Gram-negative organisms. Nocardia grew in a variety of growth media, and the median incubation time to detection was 4 days. Fifty percent of patients with Nocardia bacteremia died. Positive blood cultures were a preterminal finding in the fatal, acute cases and occurred relatively early in the subacute, nonfatal cases. Poor outcome seemed to correlate with acute onset of nocardiosis (duration less than 1 month), late identification of nocardemia, involvement of more than 2 sites, and the lack of treatment with a sulfonamide-containing regimen.

Investigation of a pseudo-outbreak of Nocardia asteroides infection by pulsed-field gel electrophoresis and randomly amplified polymorphic DNA PCR

Molecular strain typing by pulsed-field gel electrophoresis and by randomly amplified polymorphic DNA analysis was used to investigate a cluster of four Nocardia asteroides isolates associated with the BACTEC 460 TB system. An instrument motor drive misalignment resulted in inadequate needle sterilization and cross-contamination of BACTEC vials. This pseudo-outbreak illustrates the importance of proper BACTEC 460 needle sterilization and maintenance and confirms the usefulness of molecular typing methods for epidemiologic investigations.

Transmission of nocardiosis and molecular typing of Nocardia species: a short review

Nocardia species are ubiquitous in the environment and may be found in the soil. They are generally responsible for sporadic pulmonary diseases acquired by inhalation of spores, with secondary localizations in the central nervous system and subcutaneous tissues. There is no absolute evidence for person to person transmission. Presumptive outbreaks of nocardiosis were observed in immunocompromised patients, more frequently in kidney transplant patients than in cardiac transplant patients. Nocardia spp., being present in dust particles, closure and disinfection of the transplantation unit with formaldehyde arrested the sequence of cases of nocardiosis. The original sources of the Nocardia sp. remain doubtful. Other possible sources of contamination are other patients, medical staff and the hospital environment. The first studies of Nocardia spp. typing were based on the detection of extracellular antigens, on the susceptibility of actinomycete strains to killer yeasts, and on the biochemical profiles with fluorogenic substrate. The use of molecular typing techniques have given very promising results. Analysis of plasmid profiles is an interesting way to compare the identity of isolates, although the reliability of this method depends of the presence of plasmids in the isolates. Other typing methods, including analysis of restriction length fragment polymorphism of total DNA, ribosomal DNA fingerprinting, require further investigations to evaluate their discriminating power or to be easily interpretable, whereas a random amplified polymorphic DNA (RAPD) assay was successful for epidemiological purposes. Progress in epidemiological analysis of cases of nocardiosis will be consistent when an improved diagnosis of this infection (molecular and serological diagnosis) will be available, when the genetic diversity of Nocardia spp. isolates will be better known, and when molecular typing, that hold promise in complementing investigations of outbreak of these infections, will be systematically performed when an abnormal increase of cases of nocardiosis in a population with risk factors is observed.

Molecular study of nosocomial nocardiosis outbreak involving heart transplant recipients

Randomly amplified polymorphic DNA analysis and rRNA gene restriction patterns (ribotyping) were compared as methods of investigating a nosocomial outbreak of nocardiosis involving three heart transplant recipients. No clear distinctions between three clinically related isolates and four unrelated strains were obtained by ribotyping. On the contrary, randomly amplified polymorphic DNA analysis with two selected primers, primers 2650 and DKU49, showed one pattern for the three related isolates and four patterns for the unrelated strains.

Investigation of a pseudo-outbreak of orthopedic infections caused by Pseudomonas aeruginosa

OBJECTIVE

To report a pseudoepidemic of Pseudomonas aeruginosa infections discovered during an investigation of postoperative joint infections.

DESIGN

A retrospective review of case patients' hospital charts, operative reports, and laboratory data, as well as environmental culturing, polymerase chain reaction (PCR) ribotyping of outbreak isolates, and in vitro analysis of P aeruginosa growth characteristics.

SETTING

A 510-bed, university-affiliated adult tertiary care hospital.

RESULTS

Between October 1 and December 1, 1992, seven postsurgical joint infections were diagnosed, including four caused by P aeruginosa. A bottle of "sterile" saline used to process tissue specimens was found to be contaminated with P aeruginosa. Further investigation revealed that P aeruginosa had grown from seven additional tissue cultures, all of which had been processed with the contaminated saline. PCR ribotypes of the contaminant matched those of the clinical isolates. In vitro, P aeruginosa strains were viable in commercial nonbacteriostatic saline, but never caused visible turbidity. Six patients received antibiotics for their presumed infections; four patients had peripherally inserted central catheters placed, and one experienced severe anaphylactic reactions to several antibiotics.

CONCLUSIONS

Pseudoepidemics due to common organisms are often difficult to detect, and delayed recognition can result in substantial morbidity. This outbreak investigation illustrates the potential for contamination of diluents in the microbiology laboratory and emphasizes the need for meticulous quality control.

The medically important aerobic actinomycetes: epidemiology and microbiology

The aerobic actinomycetes are soil-inhabiting microorganisms that occur worldwide. In 1888, Nocard first recognized the pathogenic potential of this group of microorganisms. Since then, several aerobic actinomycetes have been a major source of interest for the commercial drug industry and have proved to be extremely useful microorganisms for producing novel antimicrobial agents. They have also been well known as potential veterinary pathogens affecting many different animal species. The medically important aerobic actinomycetes may cause significant morbidity and mortality, in particular in highly susceptible severely immunocompromised patients, including transplant recipients and patients infected with human immunodeficiency virus. However, the diagnosis of these infections may be difficult, and effective antimicrobial therapy may be complicated by antimicrobial resistance. The taxonomy of these microorganisms has been problematic. In recent revisions of their classification, new pathogenic species have been recognized. The development of additional and more reliable diagnostic tests and of a standardized method for antimicrobial susceptibility testing and the application of molecular techniques for the diagnosis and subtyping of these microorganisms are needed to better diagnose and treat infected patients and to identify effective control measures for these unusual pathogens. We review the epidemiology and microbiology of the major medically important aerobic actinomycetes.