Presumptive identification of nocardias in a clinical laboratory

STUDIES OF NOCARDIOSIS IN CATTLE 1 - ISOLATION OF NORCARIDA ASTEROIDES FROML MASTITIS IN CATTLE

A six months survey (2-8/1994) was canied out to determine norcaiidal mastitis in cattle in certain dairy herds. A total 126 milk samples collected from mastitic‘ cows and milk tank. Of which 10 from Al-Khalis station, 15 from A1-Wahda station, 6 from White Good village, 90 from Al-Dejaila station and 5 fromMilktauk. Examination of the samples result in isolation of Norcaitlia asteroides from Al-Dejaila station. The results explained that 25 animals were positive for norcaridal infection with prevalence of 20.8 % of these 25 cases, 5 cases, in pure cultural and 20 cases, mixed with other organisms. Bacteriological examination of mill: tank also resulted in positive for norcaridial isolates. Metastasis to the lung and supramammary lymph node was demonstrated. The results also explained that norcardial isolates from mastitic cows were more virulent to guinea pigs, andthis study revealed that norcardial infection are not rare in cattle.

Primary cutaneous nocardiosis in a husband and wife

A 62-year-old woman suffered from acute purulent skin disease with multiple subcutaneous abscesses. At the same time, her 65-year-old husband presented with multiple subcutaneous nodules along the lymphatic vessels of his right arm. Both had a history of a minor scratch by a thorn of a bush at the site of infection. Nocardia was identified as causative bacterium from the woman's lesions. Therefore the rare phenomenon of 2 different forms of acute primary cutaneous nocardiosis after simultaneous infection, lymphocutaneous infection, and superficial skin infection was diagnosed.

Failure to recognize rapidly growing mycobacteria in a proficiency testing sample without specific request--a wider diagnostic problem?

Fifty participants in the Swiss External Quality Control Program in Bacteriology/Mycology received a diagnostic sample containing Mycobacterium fortuitum. Only 31 used some sort of acid-fast stains, and 13 reported the diagnosis of M. fortuitum or rapidly growing mycobacteria. We conclude that the presence of 'rapid growers' in routine bacteriology samples is underestimated, and that acid-fast stains should be performed on suspicious Gram-positive rods.

Clinical application of PCR-restriction enzyme pattern analysis for rapid identification of aerobic actinomycete isolates

The accuracy and practicality of PCR-restriction enzyme pattern analysis (PRA) for routine identification of aerobic actinomycete clinical isolates were evaluated for 299 cultures submitted to the Mycobacteria/Nocardia Laboratory at the University of Texas Health Center at Tyler. PRA identification using an amplified 439-bp segment (amplicon) of the 65-kDa heat shock protein gene was compared to identification by traditional methods, including growth characteristics, susceptibility patterns, biochemical testing, and high-performance liquid chromatography analysis. Microbiological examination of six cultures ruled out aerobic actinomycetes, and they were omitted from the study. Amplicons were analyzed with BstEII, HaeIII, MspI, HinfI, and BsaHI. When necessary, AciI, HhaI, and NarI were also used. From March 1995 through May 1997 (27 months), 274 of the remaining 293 (93.5%) isolates were accurately identified by PRA. Major diagnostic groups included 170 mycobacteria, 93 nocardiae, and 30 other aerobic actinomycetes. Mixed cultures were readily recognized by PRA, including a wound culture that contained two Nocardia taxa that were indistinguishable morphologically. Mycobacterium mucogenicum was identified in three cultures heavily contaminated with gram-positive cocci. The 19 isolates that produced PRA patterns that did not match those in the current PRA database were differentiated into 8 Mycobacterium species and 11 other aerobic actinomycetes by the presence or absence of BstEII recognition sites. Identification of 15 of these 19 isolates was also equivocal by traditional methods. PRA results were reportable within 2 to 5 working days and were as accurate as and faster and less expensive to obtain than those of traditional methods.

Recognition of a Nocardia transvalensis complex by resistance to aminoglycosides, including amikacin, and PCR-restriction fragment length polymorphism analysis

Amikacin resistance, rare among nocardiae, was observed in 58 clinical isolates of nocardiae. All of these isolates hydrolyzed hypoxanthine, and 75 to 100% utilized citrate, D-galactose, and D-trehalose as sole carbon sources. Based on utilization of I-erythritol, D-glucitol, i-myo-inositol, D-mannitol, and ribitol and susceptibility to amoxicillin-clavulanic acid, the 58 isolates were separable into four groups. One group was negative for I-erythritol and ribitol and included all the isolates belonging to Nocardia asteroides complex antibiogram type IV. The remaining three groups were positive for I-erythritol and ribitol and were grouped within Nocardia transvalensis. The group that included the type strain was designated N. transvalensis sensu stricto, and the other two groups were designated new taxons 1 and 2. PCR-restriction fragment length polymorphism (RFLP) analysis of a 439-bp segment of the 65-kDa heat shock protein gene with XhoI and HinfI produced identical patterns for 53 (91%) and 58 (100%) isolates, respectively, and differentiated them from all other Nocardia taxa. NarI- and HaeIII-derived RFLP patterns clearly differentiated each of the four biochemically defined taxa. These four groups were also distinguishable by using the chromogenic substrates in Dade MicroScan test panels. By high-performance liquid chromatography, these isolates exhibited the same unique mycolic acid-ester elution patterns that differed from those of all other clinically significant nocardiae. Gas-liquid chromatographic analysis of fatty acids also produced similar patterns for all isolates that distinguished them from all other Nocardia taxa, but did not differentiate the four taxa within the complex. We propose the designation N. transvalensis complex for these four groups of nocardiae, pending further genetic evaluation.

A rapid and gentle method for isolation of genomic DNA from pathogenic Nocardia spp

The lack of simple and efficient methods for extraction of DNA from Nocardia spp. has hampered molecular manipulation of the DNA for diagnostic purposes. In the present study, a method for the rapid extraction of undegraded genomic nocardial DNA was established. Briefly, 14 pathogenic Nocardia strains were grown at 37 degrees C for 3 to 5 days in Sauton broth containing 0.05% Tween 80. Subsequently, the cultures were treated for 48 h with 1.2 mg of cycloserine per ml (final concentration). Cells were then harvested by centrifugation and treated with a lysis solution containing 3 mg of lysozyme per ml. This was followed by the addition of proteinase K and sodium dodecyl sulfate to final concentrations of 0.2 mg/ml and 0.5%, respectively, and incubation for 1 h at 50 degrees C. DNA was precipitated with isopropanol after phenol-chloroform-isoamyl alcohol extractions and RNase treated before being quantitated and analyzed by agarose gel electrophoresis. The average undegraded DNA yields obtained were 101 micrograms for Nocardia brasiliensis and 121 micrograms for N. asteroides. This DNA was suitable for restriction endonuclease digestion and PCR amplification, which are methods being applied to the characterization and diagnosis of slowly growing organisms such as Nocardia spp.

Nocardia species: host-parasite relationships

The nocardiae are bacteria belonging to the aerobic actinomycetes. They are an important part of the normal soil microflora worldwide. The type species, Nocardia asteroides, and N. brasiliensis, N. farcinica, N. otitidiscaviarum, N. nova, and N. transvalensis cause a variety of diseases in both normal and immunocompromised humans and animals. The mechanisms of pathogenesis are complex, not fully understood, and include the capacity to evade or neutralize the myriad microbicidal activities of the host. The relative virulence of N. asteroides correlates with the ability to inhibit phagosome-lysosome fusion in phagocytes; to neutralize phagosomal acidification; to detoxify the microbicidal products of oxidative metabolism; to modify phagocyte function; to grow within phagocytic cells; and to attach to, penetrate, and grow within host cells. Both activated macrophages and immunologically specific T lymphocytes constitute the major mechanisms for host resistance to nocardial infection, whereas B lymphocytes and humoral immunity do not appear to be as important in protecting the host. Thus, the nocardiae are facultative intracellular pathogens that can persist within the host, probably in a cryptic form (L-form), for life. Silent invasion of brain cells by some Nocardia strains can induce neurodegeneration in experimental animals; however, the role of nocardiae in neurodegenerative diseases in humans needs to be investigated.

Use of a siderophore detection medium, ethylene glycol degradation, and beta-galactosidase activity in the early presumptive differentiation of Nocardia, Rhodococcus, Streptomyces, and rapidly growing Mycobacterium species

A simplified scheme for the presumptive early identification of Nocardia, Rhodococcus, rapidly growing Mycobacterium, and Streptomyces species is presented. The Nocardia and Streptomyces spp. and the Mycobacterium spp. were positive. The spp. were positive for siderophore activity, but only 25% of the Rhodococcus spp. were positive. The Rhodococcus and Mycobacterium spp. were negative for beta-galactosidase, while the Nocardia and Streptomyces spp. were positive. The Nocardia and Streptomyces spp. and the Mycobacterium spp. were negative for ethylene glycol degradation, while 75% of the Rhodococcus spp. were positive. In combination, these tests were useful for differentiating Mycobacterium, Rhodococcus, and Nocardia species but did not differentiate Nocardia from Streptomyces species.