Reclassification of Corynebacterium pyogenes (Glage) in the genus Actinomyces, as Actinomyces pyogenes comb.nov

Corynebacterium pyogenes (Glage) differs to such an extent from the type species of Corynebacterium, Corynebacterium diphtheriae (Lehmann and Neumann), that it cannot be retained in this genus. Numerical phenetic and chemical data indicate a close relationship between Corynebacterium pyogenes and the species Actinomyces bovis (Harz). It is proposed that Corynebacterium pyogenes be reclassified in the genus Actinomyces, as Actinomyces pyogenes (Glage) comb.nov.     

Antimicrobial Susceptibility of Corynebacterium bovis Isolates from Immunodeficient Rodents

Corynebacterium bovis, the causative agent of hyperkeratotic dermatitis in immunodeficient mice, is a significant problem in preclinical oncology research. Infection results in lifelong skin colonization and a decrease in successful engraftment of patient-derived xenograft tumor models. The use of antimicrobial agents for C. bovis is controversial in light of reports of poor efficacy and the possibility of selection for resistant strains. The purpose of this study was to describe the antimicrobial susceptibilities of C. bovis isolates obtained exclusively from immunodeficient rodents in order to aid in antimicrobial dose determination. Between 1995 and 2018, 15 isolates were collected from 11 research institutions across the United States. Antimicrobial susceptibility testing was performed for 24 antimicrobials commonly used against gram-positive bacteria. Our results provide an updated understanding of the susceptibility profiles of rodent C. bovis isolates, indicating little variability between geographically and temporally distant isolates. These results will facilitate appropriate antimicrobial use to prevent and treat C. bovis infections in immunodeficient rodents.

Corynebacterium bovis is a gram-positive, facultatively anaerobic pleomorphic bacillus that infrequently causes infections in humans⁵ but is more clinically relevant in veterinary medicine. Veterinary interest in this bacterium originated in the dairy industry, where it causes subclinical mastitis in infected animals and is the most common Corynebacterium spp. isolated from infected udders. When present as a primary infection, C. bovis can cause decreases in milk quality with no significant decrease in milk yield.^9,12 Despite being considered a minor pathogen, the impact of C. bovis on milk quality remains economically important to the dairy industry.C. bovis was first recognized in the mid1970s in athymic nude mice with hyperkeratotic dermatitis, a condition that would later be termed ‘scaly skin disease.’⁶ Once genetically characterized in the mid1990s and confirmed to have an association with clinical disease, C. bovis emerged as an important pathogen of immunodeficient mice in the laboratory animals.⁷ Historically, C. bovis infections of research mice primarily occurred in athymic nude mice. However, as the number of transgenic immunodeficient strains has expanded, C. bovis is no longer considered an infection exclusively of athymic nude mice, as infections have been reported in immunodeficient and ‘immune-vague’ research rodents around the world.^{3,10,11,15,21}Antimicrobial susceptibility testing is used to identify the minimum inhibitory concentration (MIC) of specific antimicrobials that prevents the growth of an individual bacterial isolate in vitro. By including many isolates of the same organism into a test population, the MIC can be calculated that inhibits the growth of 50% (MIC₅₀) or 90% (MIC₉₀) of the isolates.²² MIC have been published for C. bovis isolates obtained from dairy cows.²⁵ In the dairy industry, dry cow therapy (the administration of antibiotics at the end of lactation) is highly effective at eliminating subclinical mastitis caused by Corynebacterium spp.¹ However, elimination of C. bovis from immunodeficient mouse populations is much more challenging.^15,17 To date, the dose of amoxicillin used to treat C. bovis-infected immunodeficient mice has been informed by MIC data from dairy cows isolates²⁵ and in vivo pharmacokinetic data in the form of blood plasma concentrations of amoxicillin administered in the drinking water.¹⁶ However, our group and others have demonstrated the reemergence of infection in immunodeficient mice after the discontinuation of antibiotic administration in a C. bovis-free environment. These findings suggest that the MIC for C. bovis isolates from mice may differ from that of cows.²Recently, the genomes of C. bovis isolates obtained from humans, cows, mice, and rats were sequenced. Subsequent genomic comparisons assessing the average nucleotide identity between isolates identified sequence divergence obtained from humans and cows as compared with isolates from rodents.⁴ In particular, the number of genomic islands and virulence factors were significantly higher in the rodent isolates than in the human and cow isolates. However, whether phenotypic changes in antimicrobial susceptibility accompany this genetic divergence is unknown. Considering the prior observations and new developments in our understanding of C. bovis across multiple species, the purpose of this study is to describe antimicrobial susceptibility profiles of C. bovis isolates obtained exclusively from immunodeficient rats and mice.     

The Nutritional Requirements and Biochemical Reactions of Corynebacterium bovis

S ummary . The cultural characteristics and biochemical reactions of 142 isolates of Corynebacterium bovis were examined and found to include the production of acid from glucose, fructose and glycerol, and the hydrolysis of urea. The reactions on lipolysis test media were equivocal, in part due to the inability of the organism to grow on some media, and also due to the doubtful validity of using Tween agar to test for lipase production. C. bovis demonstrated a requirement for serum, Tween 20 or 80, or egg yolk. In experiments carried out with fully defined liquid media this nutritional requirement was fulfilled by synthetic lecithin or Tween 80, or a mixture of both compounds.     

Cell wall composition in Corynebacterium bovis and some other corynebacteria

The cell wall compositions of two strains of Corynebacterium bovis were found to differ: one contained lysine, rhamnose, mannose, and glucose, the other meso-alpha, epsilon, diaminopimelic acid (DAP), arabinose, galactose, and mannose. The walls of a strain of C. nephridii were characterized by l-DAP and galactose. Those of a strain of C. paurometabolum and of two strains of "lipophilic diphtheroids" contained meso-DAP, arabinose, galactose, and mannose as did walls of a reference strain of C. xerosis. The results are discussed in relation to the taxonomy of the organisms examined.     

Draft Genome Sequence of Corynebacterium bovis DSM 20582, Which Causes Clinical Mastitis in Dairy Cows

Bovine mastitis represents the most economically important disease in dairy cows and can be caused by Corynebacterium bovis, a commensal in the bovine udder. The draft genome sequence provides insights into the adaptation of this bacterium to the bovine habitat and its lipolytic capabilities to utilize components of cow's milk.     

Experimental inoculation of meadow voles (Microtus pennsylvanicus), house mice (Mus musculus), and Norway rats (Rattus norvegicus) with Mycobacterium bovis

Mycobacterium bovis has a wide host range that includes several wildlife species, and this can hamper attempts to eradicate bovine tuberculosis from livestock. The purpose of this study was to determine if common rodent species, namely meadow voles (Microtus pennsylvanicus), house mice (Mus musculus), and Norway rats (Rattus norvegicus), that inhabit the bovine tuberculosis endemic area of Michigan, can be experimentally infected with M. bovis. The objectives of the study were: 1) to determine if these rodent species can be infected, and if so, to document attendant pathologic processes/pathogenesis; 2) to detect any fecal shedding of M. bovis; and 3) to evaluate the relative susceptibility of the three species to M. bovis infection. For each species (n=36) there were two treatment (n=12/group) and one or two control groups depending on species (n=6-12/group); the maximum study duration was 60 days. The meadow vole treatments consisted of high dose inocula that were given by oral or intranasal routes, whereas the house mice and Norway rats were given only oral inocula at either a high or low dose. Of the three species, meadow voles were most susceptible to M. bovis infection. Upon intranasal inoculation, all 12 voles were infected as determined by gross and microscopic lesions and culture of M. bovis from tissue and feces. Seven of the 12 meadow voles inoculated orally were infected. House mice also were susceptible; M. bovis was isolated from 14 of 24 animals. Only one Norway rat in the high dose treatment group was positive by culture and this was the only animal from which minimal attendant lesions were observed. Results of this study indicate that meadow voles and house mice can be infected with M. bovis and might serve as spillover hosts. Concerted efforts should, therefore, be made to reduce or eliminate these rodents on premises where M. bovis-infected livestock are present.     

DNA homology study of Corynebacterium diphtheriae v. gravis groups I, II and III, Corynebacterium ulcerans and Corynebacterium pseudotuberculosis (ovis)

The homology of genomes within Krylova 's groups I, II and III of C. diphtheriae, including toxigenic C. diphtheriae and their nontoxigenic precursors within the same group, was confirmed by the method of DNA/DNA molecular hybridization; the homology of DNA within the groups was 89-103%, the thermostability of heteroduplexes being high (on the level of homoduplexes ). The heterogeneity of genomes within these 3 groups of cultivar gravis was confirmed, which made it possible to consider C. diphtheriae, groups I, II and III, to belong to different, though closely related species; in intergroup hybridization the homology of DNA varied, as a rule, between 66% and 73%, while the thermostability of heteroduplexes was low: delta T50 was -3 degrees C to -6 degrees C. The differences in genomes (on the level of different species) between 3 groups of C. diptheriae v. gravis on one hand and C. diphtheriae v. mitis C7 (-) tox- and its convertant C7 (beta) tox+ of phage tox+ on the other hand (DNA homology being 56-62%), as well as between C. diphtheriae v. intermedius No. 328 tox+ on one hand and the representatives of 3 groups of C. diphtheriae v. gravis and C. diphtheriae v. mitis, strain C7 (beta) tox+, on the other hand (DNA homology being 42-43%) were revealed. The heterogeneity of genomes (on the level of different genera) was revealed between C. diphtheriae strains, cultivars gravis (groups I, II and III), mitis (C7(-) tox- and C7 (beta) tox+) and intermedius (No. 328 tox+) on one hand and C. ulcerans and C. pseudotuberculosis (ovis) strains on the other hand; DNA homology was 11-17% for C. ulcerans and 22-26% for C. pseudotuberculosis (ovis), the thermostability of heteroduplexes being at the lowest level (delta T50 was -11 degrees C to -13 degrees C). As a result, C. diphtheriae, classified by Bergey as a single species, was found to comprise 5 species detected by means of marking in accordance with their phenotypical features and genome structure, carried out by the method of DNA/DNA molecular hybridization; among these species were group I, II and III strains of cultivar gravis, strain C7 of cultivar mitis and strain No. 328 of cultivar intermedius. C. ulcerans and C. pseudotuberculosis (ovis) strains investigated in this study can possibly be placed outside the genus including 5 C. diphtheriae species.     

Purification and characterization of Mycobacterium tuberculosis KatG, KatG(S315T), and Mycobacterium bovis KatG(R463L)

Isoniazid, a first-line antibiotic used for the treatment of tuberculosis, is a prodrug that requires activation by the Mycobacterium tuberculosis enzyme KatG. The KatG(S315T) mutation causes isoniazid resistance while the KatG(R463L) variation is thought to be a polymorphism. Much of the work to date focused on isoniazid activation by KatG has utilized recombinant enzyme overexpressed in Escherichia coli. In this work, native KatG and KatG(S315T) were purified from M. tuberculosis, and KatG(R463L) was purified from Mycobacterium bovis. The native molecular weight, enzymatic activity, optical, resonance Raman, and EPR spectra, K(D) for isoniazid binding, and isoniazid oxidation rates were measured and compared for each native enzyme. Further, the properties of the native enzymes were compared and contrasted with those reported for recombinant KatG, KatG(S315T), and KatG(R463L) in order to assess the ability of the recombinant enzymes to act as good models for the native enzymes.     

Moxidectin evaluation against Solenoptes capillatus (Anoplura: Linognathidae), Bovicola bovis (Mallophaga: trichodectidae), and Musca autumnalis (Diptera: Muscidae) on cattle.

Slow release formulations of 375, 750, and 1,125 mg (AI) in 50-g boluses and a subcutaneous injectable formulation (0.2 mg AI/kg body wt) of moxidectin (CL301423) were tested for the control of the little blue cattle louse, Solenoptes capillatus (Enderlein), and the cattle biting louse, Bovicola bovis (L). S. capillatus populations were reduced 4 wk after treatment and complete control was observed 6 wk after treatment in groups treated with boluses, B. bovis were first observed at 3 wk and continued to increase throughout the 14-wk test period. These were experimental boluses and future boluses may perform differently. Subcutaneous injections of moxidectin gave complete control of S. capillatus for a 27-d test period. Feces from animals treated with boluses were tested with face fly larvae, Musca autumnalis De Geer, to demonstrate fecal activity of moxidectin. Larval mortality in these groups ranged from 90 to 30% from 2 d to 10 wk after treatment.     

Assignment of Actinomyces pyogenes-like (CDC coryneform group E) bacteria to the genus Actinomyces as Actinomyces radingae sp. nov. and Actinomyces turicensis sp. nov.

In a previous study the authors reported the characterization of some facultatively anaerobic, Gram-positive, non-sporeforming rods which were found in mixed cultures from various infectious processes, including patients with otitis, empyema, perianal abscesses and decubitus ulcers. Phenotypically these organisms closely resembled Actinomyces pyogenes although their precise taxonomic position remained unknown. In the present investigation the authors have determined the 16S rRNA gene sequences of some representative strains of the Actinomyces pyogenes -like bacteria and report the results of a comparative sequence analysis. On the basis of the results of the present and earlier findings two new Actinomyces species, Actinomyces radingae sp. nov. and Actinomyces turicensis sp. nov. are proposed. The type strains are DSM 9169^T and DSM 9168^T, respectively.