Agents of newly recognized or infrequently encountered mycobacterial diseases

This paper reviews recent information on the systematics and clinical significance of potentially pathogenic environmental mycobacteria. A short history of these mycobacteria is given. Information on species for which clinical and systematic aspects have already been well documented, i.e., Mycobacterium kansasii, M. marinum, M. scrofulaceum, M. simiae, M. szulgai, M. ulcerans, M. xenopi, and members of the M. fortuitum complex, is updated. Although the M. avium complex was extensively reviewed in earlier literature, major new systematic and clinical information is presented in some detail. Species that have received very limited prior coverage, i.e., M. asiaticum, M. haemophilum, M. malmoense, and M. shimoidei, are the main subjects of this review and are discussed in detail. The rare infections attributed to species that are normally considered nonpathogenic, i.e., M. gastri, M. gordonae, the M. terrae complex, and most of the rapidly growing mycobacteria outside of the M. fortuitum complex, are critically reviewed. Finally, suggestions are offered for practical measures that can minimize the risk of failing to isolate or misidentifying some of the more obscure potentially pathogenic environmental mycobacteria that are only infrequently recognized.

Sequence-based identification of Mycobacterium species using the MicroSeq 500 16S rDNA bacterial identification system

We evaluated the MicroSeq 500 16S rDNA Bacterial Sequencing Kit (PE Applied Biosystems), a 500-bp sequence-based identification system, for its ability to identify clinical Mycobacterium isolates. The organism identity was determined by comparing the 16S rDNA sequence to the MicroSeq database, which consists primarily of type strain sequences. A total of 113 isolates (18 different species), previously recovered and identified by routine methods from two clinical laboratories, were analyzed by the MicroSeq method. Isolates with discordant results were analyzed by hsp65 gene sequence analysis and in some cases repeat phenotypic identification, AccuProbe rRNA hybridization (Gen-Probe, Inc., San Diego, Calif.), or high-performance liquid chromatography of mycolic acids. For 93 (82%) isolates, the MicroSeq identity was concordant with the previously reported identity. For 18 (16%) isolates, the original identification was discordant with the MicroSeq identification. Of the 18 discrepant isolates, 7 (six unique sequences) were originally misidentified by phenotypic analysis or the AccuProbe assay but were correctly identified by the MicroSeq assay. Of the 18 discrepant isolates, 11 (seven unique sequences) were unusual species that were difficult to identify by phenotypic methods and, in all but one case, by molecular methods. The remaining two isolates (2%) failed definitive phenotypic identification, but the MicroSeq assay was able to definitively identify one of these isolates. The MicroSeq identification system is an accurate and rapid method for the identification of Mycobacterium spp.

CHANGES IN NERVE CONDUCTION IN EXPERIMENTAL ALLERGIC NEURITIS

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EFFECT OF ENVIRONMENTAL TEMPERATURES ON INFECTION WITH MYCOBACTERIUM MARINUM (BALNEI) OF MICE AND A NUMBER OF POIKILOTHERMIC SPECIES

Clark, H Fred (Communicable Disease Center, Atlanta, Ga.), and Charles C. Shepard. Effect of environmental temperatures on infection with Mycobacterium marinum (Balnei) of mice and a number of poikilothermic species. J. Bacteriol. 86:1057-1069. 1963.-An exploration was made of the effect of environmental temperature on infections with Mycobacterium marinum of mice, young opossums, and bats, and of 50 species of poikilothermic animals. In artificial medium (7H9 broth) M. marinum grew most rapidly from 25 to 35 C, with generation times of 4 to 6 hr. At 37 C, the generation time was 14 hr; at 20 C, 20 hr; and, at 15 C and lower, little growth was observed. In mice, deep body temperatures were found to be 36.5 to 37.3 C at environmental temperatures of 4 to 30 C. At an environmental temperature of 34 C, they averaged 39.1 C; at 37 C they averaged 40.2 C. Foot-pad temperatures were within a few degrees of ambient temperatures from 10 to 34 C. In mouse foot-pad infections, the optimal environmental temperature for infection was 20 C, and the generation time of the infecting bacilli at this environmental temperature was about 15 hr. Intravenously inoculated mice developed peripheral infections of nose, feet, and tail at environmental temperatures of 4 to 30 C. At these temperatures, they had severe pneumonic involvement, and the mice at lower temperatures tended to succumb most rapidly to systemic infection. At 34 C, the intravenously infected mice did not develop peripheral infections and there was no pulmonary involvement. Young opossums, whose deep body temperatures are only 34 to 36 C, were inoculated in the foot-pad and intravenously. Foot-pad infection developed without systemic involvement. Bats, which assume environmental temperature when at rest, were inoculated in the foot-pad. Foot-pad infections were observed but no systemic disease. The bats could be maintained for only short periods, however. Poikilothermic animals were studied. Deep body temperatures were found to be nearly identical with ambient temperature. A total of 50 species of reptiles, amphibians, and fish were infected intraperitoneally in a number of experiments, as animals were available. Susceptibility to M. marinum was found throughout these species. There was no tendency to peripheral involvement. In experiments to determine the optimal environmental temperature for infection, cricket frogs (Acris), American chameleons (Anolis), young garter snakes (Thamnophis), and the young of three species of turtles were inoculated intraperitoneally. The optimal temperature for infection was found to be 30 C in each case, and infections at 20 C were definitely slower. The generation time of M. marinum in American chameleons at 30 C was about 19 hr; at 20 C, it was about 46 hr; and, at 10 C, the bacilli did not apparently multiply. Transmission studies revealed instances where infected animals shed M. marinum into the waters in which they were kept, and where animals became infected from water containing M. marinum.

Identification of a major epitope by anti-interferon-γ autoantibodies in patients with mycobacterial disease

The binding of autoantibodies (autoAbs) to interferon (IFN)-γ in people with mycobacterial diseases has become an emerging medical concern. Many patients display specific human leukocyte antigen (HLA) class II haplotypes, which suggests that a common T cell-dependent and B cell-dependent mechanism might underlie the production of specific anti-IFN-γ autoAbs. We show here that these autoAbs target a major epitope (amino acids 121-131, designated position (P)121-131) in a region crucial for IFN-γ receptor (IFN-γR) activation to impair IFN-γ-mediated activities. The amino acid sequence of this epitope is highly homologous to a stretch in the Noc2 protein of Aspergillus spp., which was cross-reactive with autoAbs from patients. Rats immunized with Aspergillus Noc2 developed antibodies that reacted with human IFN-γ. We generated an epitope-erased variant of IFN-γ (EE-IFN-γ), in which the major neutralizing epitope region was altered. The binding affinity of anti-IFN-γ autoAbs for EE-IFN-γ was reduced by about 40%, as compared to that for IFN-γ1-131. Moreover, EE-IFN-γ activated the IFN-γR downstream signaling pathway ex vivo, irrespectively of anti-IFN-γ autoAbs. In conclusion, we identified a common, crucial B cell epitope that bound to anti-IFN-γ autoAbs in patients, and we propose a molecular-mimicry model for autoAb development. In addition, treatment with EE-IFN-γ might be worth investigating in patients producing anti-IFN-γ autoAbs.

Report on the Fourth International Workshop on Reactive Arthritis

There are large differences in the antigenicity and biology of the ReA-associated bacteria. For induction of arthritis, the relevance seems to be only that antigenic material reaches the joint, alive or dead. If there is a common antigen, it has to be a highly conserved one. Bacterial hsp60 seems to be an immunodominant T cell antigen in ReA, but there must be other relevant antigens shared by these different bacteria. An ineffective immune response (for example, low production of TNFalpha) seems to contribute to the manifestations and course of ReA. Although arthritis can also occur in its absence, HLA-B27 plays an important role in the pathogenesis of ReA and the other SpA. Current data suggest that B27 probably acts as an antigen-presenting molecule for a still-unknown arthritogenic molecule. Comparison of ReA with IBD-associated arthritis suggests that there might indeed be a common antigen shared by ReA-associated bacteria and bacteria of the gut flora. CD8+ T cells seem to be important in ReA and other SpA. In some parts of the world, such as in Mexico, ReA could be a major predisposing cause of the development of AS. Antibiotic treatment is not effective, probably because the triggering bacteria are already dead or in a partly latent state at the time arthritis occurs. Based on this knowledge and on new technologies, it should be possible in future years to derive answers to the questions about ReA and the other SpA and, as a consequence, to find a cure.

Mycobacterium arupense sp. nov., a non-chromogenic bacterium isolated from clinical specimens

SeveralMycobacterium-like organisms related to theMycobacterium terraecomplex have been isolated from clinical samples. In the clinical microbiology laboratory, partial 16S rRNA gene sequencing (approximately the first 500 bp) rather than full 16S rRNA gene sequencing is often used to identifyMycobacteriumspecies. Partial 16S rRNA gene sequence analysis revealed 100 % similarity between 65 clinical isolates andMycobacteriumsp. MCRO 6 (GenBank accession no. X93032). Even after sequencing the nearly full-length 16S rRNA gene, closest similarity was only 99.6 % toMycobacterium nonchromogenicumATCC 19530T. Sequencing of the nearly full-length 16S rRNA gene, the 16S–23S internal transcribed spacer region and thehsp65gene did not reveal genotypic identity with the type strains ofM. nonchromogenicum,M. terraeorMycobacterium triviale. Although sequence analysis suggested that these clinical isolates represented a novel species, mycolic acid analysis by HPLC failed to distinguish them fromM. nonchromogenicum. Therefore, phenotypic analysis including growth characterization, antibiotic susceptibility testing and biochemical testing was performed. These strains from clinical samples should be recognized as representing a novel species of the genusMycobacterium, for which the nameMycobacterium arupensesp. nov. is proposed. The type strain is AR30097T(=ATCC BAA-1242T=DSM 44942T).

Fungi, mycobacteria, zoonotic and other organisms in prosthetic joint infection

A systematic review of the presentation and management of prosthetic joint infection (PJI) due to zoonotic microorganisms, fungi, mycobacteria and other unusual microorganisms is not available. We therefore sought to provide a resource for the practicing orthopaedic surgeon which will serve as a guide for making appropriate decisions in managing such rare, but potentially problematic conditions. We conducted a Medline search of all case reports of PJI due to these unusual microorganisms. Our review of the current literature showed the diagnosis of PJI due to zoonotic microorganisms, fungi, mycobacteria and other unusual microorganisms typically necessitates specialized diagnostic tests. Maintaining a high index of suspicion in diagnosis of such unusual microorganisms and requesting the appropriate laboratory tests at the time of surgical débridement is crucial for determining the microbiologic etiology of these infections. The appropriate medical and surgical management of such infections is complex and often requires the use of special antimicrobials with which the orthopaedist may not be familiar. Collaboration with an infectious disease specialist is advisable when treating these infections.

Pediatric head and neck lesions

Commonly encountered head and neck lesions in children are described with an emphasis on evaluation, diagnosis, and treatment. Congenital lesions typically require excision, although hemangiomas usually resolve spontaneously. Acute suppurative lymphadenitis is common and readily diagnosed. Chronic lymphardenitis remains a diagnostic challenge and must be differentiated from malignancy. Lesions that do not respond to antibiotics should be biopsied to exclude neoplasms.

Nontuberculous mycobacterial peritonitis associated with continuous ambulatory peritoneal dialysis

We report two patients undergoing continuous ambulatory peritoneal dialysis (CAPD) in whom peritonitis developed and nontuberculous mycobacteria were isolated from peritoneal fluid. In one, Mycobacterium avium-intracellularis was the only organism isolated. Despite a three-month course of antibiotics to which the organism showed in vitro sensitivity, there was no apparent response. The patient died, and an autopsy showed disseminated mycobacterial disease. In the second case, Mycobacterium fortuitum and diphtheroids were isolated from the peritoneal fluid. Although it was not clear that the mycobacterium was solely responsible for the peritonitis in the second case, the infection failed to resolve with antibiotic therapy appropriate for diphtheroids. This patient also died. Both patients had indolent, chronic infections, although there was granulocyte predominance in the peritoneal fluid. Both had involvement of the catheter exit site. To our knowledge, these are the first reported cases of nontuberculous mycobacterial peritonitis in CAPD patients. We recommend evaluation for mycobacteria, including cultures and stains of dialysate specimens, in all cases of CAPD-associated peritonitis where no organism is identified, or where no improvement is noted after 48 hours of therapy. Repeated cultures for mycobacteria are appropriate for suggestive cases. Since these infections are difficult to treat, it may be prudent to remove the dialysis catheter if they are isolated.

Mycobacterium marinum infection of the hand involving deep structures

Five patients with Mycobacterium marinum infection of the hand involving deep structures were seen recently. Four of them were fishermen. Hydrocortisone injection or simple incision and drainage led to worsening of the infection. The clinical presentation, operative finding, and histopathologic and microbiologic features were quite similar in all five patients. Extensive debridement and therapy with ethambutol and rifampin led to satisfactory results in four patients while biopsy and therapy in the fifth patient seemed to offer another form of acceptable treatment.

Temperature optimum of Mycobacterium leprae in mice

Shepard, Charles C. (Communicable Disease Center, Atlanta, Ga.). Temperature optimum of Mycobacterium leprae in mice. J. Bacteriol. 90:1271-1275. 1965.-Mycobacterium leprae multiplied most rapidly in foot pads of mice kept at an air temperature of 20 C. At air temperatures of 15 and 25 C, bacillary multiplication was slightly slower; at 10 and 30 C, distinctly slower; and at 4 and 35 C, no bacillary multiplication was detected. The temperature of the foot pad tissues of mice kept at an air temperature of 20 C averaged 27 to 30 C and that of mice kept at 10 and 30 C averaged about 25 and 36 C, respectively. These measurements indicate that the optimal temperature for the growth of M. leprae in mice is in the range several degrees above and below 30 C. The comparative effect of different air temperatures on the growth of M. leprae in foot pads was very similar to that found earlier for M. marinum in this site, thus indicating that the potential growth of M. leprae in vitro might have a similar optimum to M. marinum in vitro, i.e., 25 to 35 C. The optimal temperature for the growth of M. leprae appears to be the same in mice as in humans. It is pointed out that the temperature optimum of M. leprae may be a reflection of the fact that most of the bacilli being excreted into the environment, where they may reach new hosts, have multiplied in the nasal mucosa, a cool tissue.

Mycobacterium fortuitum keratitis

Two of four cases of Mycobacterium fortuitum keratitis occurred after corneal surgery with contact lens wear, one was associated with extended contact lens wear alone, and one occurred after a foreign body injury. All cases were characterized by pain, conjunctival hyperemia, stromal inflammation, and ulceration. Diagnosis was made by culture and acid-fast staining of corneal scrapings. On the basis of published experience with amikacin for the treatment of nonocular M. fortuitum infections, three patients were treated with topical amikacin. Two patients responded clinically, but histopathologic examination of a penetrating keratoplasty specimen in one of the two disclosed persistent infection. One patient was cured of early disease by debridement alone. Rapid diagnosis and absence of corticosteroid use were the two most important determinants of successful therapy. In advanced cases, infection may be cured and useful vision restored by penetrating keratoplasty.