Review article Corynebacterium pseudotuberculosis
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- Corynebacterium pseudotuberculosis / caseous lymphadenitis / pathogenesis / virulence / vaccine Table of contents
- 1. INTRODUCTION
- 2. MICROBIOLOGICAL, BIOCHEMICAL AND TAXONOMIC FEATURES OF C. PSEUDOTUBERCULOSIS 2.1. Microbiological aspects
- 2.2. Biochemical properties
- 2.3. Antimicrobial susceptibility
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201 Vet. Res. 37 (2006) 201–218 © INRA, EDP Sciences, 2006 DOI: 10.1051/vetres:2005056 Review article Corynebacterium pseudotuberculosis: microbiology, biochemical properties, pathogenesis and molecular studies of virulence Fernanda Alves D ORELLAa , Luis Gustavo Carvalho P ACHECOa , Sergio Costa O LIVEIRAb , Anderson M IYOSHIa , Vasco A ZEVEDOa * a Laboratório de Genética Celular e Molecular, Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, CP 486, CEP 31270-901, Belo Horizonte, MG, Brazil b Laboratório de Imunologia de Doenças Infecciosas, Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, CP 486, CEP 31270-901, Belo Horizonte, MG, Brazil (Received 2 February 2005; accepted 4 November 2005)
(CLA), a common disease in small ruminant populations throughout the world. Once established, this disease is difficult to eradicate because drug therapy is not effective and because the clinical detection of infected animals is of limited efficiency. We reviewed the microbiological, biochemical and taxonomic features of C. pseudotuberculosis, general aspects of infection, the main virulence determinants and currently available commercial vaccines. We also examined the current molecular strategies for the study of virulence in C. pseudotuberculosis, including the latest research on the identification of novel virulence factors and genes, which will help us to better understand the biology of this microorganism. This knowledge may also contribute to the development of improved CLA vaccines, including subunit and DNA-based types, as well as to improve the diagnosis, treatment and control of this disease.
1. Introduction ..................................................................................................................................... 202 2. Microbiological, biochemical and taxonomic features of C. pseudotuberculosis ........................... 202 2.1. Microbiological aspects .......................................................................................................... 202 2.2. Biochemical properties............................................................................................................ 203 2.3. Antimicrobial susceptibility .................................................................................................... 203 2.4. Taxonomy ............................................................................................................................... 206 3. General aspects of C. pseudotuberculosis infection ........................................................................ 207 3.1. Transmission ........................................................................................................................... 207 3.2. Human cases............................................................................................................................ 207 3.3. Caseous lymphadenitis............................................................................................................ 207 * Corresponding author: vasco@icb.ufmg.br Article published by EDP Sciences and available at http://www.edpsciences.org/vetres or http://dx.doi.org/10.1051/vetres:2005056 202 F.A. Dorella et al. 3.4. Epidemiology of CLA .............................................................................................................208 3.5. Diagnosis and control of CLA .................................................................................................208 4. From proteins to DNA: Commercial and experimental vaccines ....................................................208 4.1. Commercial vaccines ...............................................................................................................208 4.2. Experimental vaccines .............................................................................................................210 5. Determinants of virulence ...............................................................................................................210 5.1. Phospholipase D ......................................................................................................................210 5.2. Toxic cell-wall lipids ...............................................................................................................211 5.3. New candidates ........................................................................................................................211 6. Molecular strategies for the study of virulence in C. pseudotuberculosis .......................................211 6.1. Identification of immunodominant peptides............................................................................211 6.2. Generation of mutants..............................................................................................................212 7. Future directions ...............................................................................................................................212
The genus Corynebacterium belongs to a suprageneric group of actinomycetes that also includes the genera Mycobacterium, Nocardia and Rhodococcus [46, 87, 100, 102]. These gram-positive bacteria (Corynebac- terium, Mycobacterium, Nocardia and Rhodococcus species), termed the CMN group, constitute a very heterogeneous group; however, most of the species share partic- ular characteristics, such as: (i) a specific cell wall organization, mainly character- ized by the presence of a huge polymer complex composed of peptidoglycan, ara- binogalactan and mycolic acids [5, 26–28, 39, 45, 48] and (ii) high G+C content (47– 74%) [39, 40, 43, 80]. The genomes of sev- eral species of this group have already been completely sequenced; this fact reflects the considerable medical, veterinary and bio- technological importance of these organ- isms (Tab. I).
an important animal pathogen. It is the eti- ological agent of a disease that is commonly called caseous lymphadenitis (CLA) or cheesy gland [114]. This disease is found in all the world’s major sheep and goat pro- duction areas, causing significant eco- nomic losses [85, 114]. In this review, we present the main microbiological characteristics of C. pseu- dotuberculosis. Bacterial virulence deter- minants, including previously reported vir- ulence factors and recently identified molecules, are discussed, with emphasis on the molecular strategies that have been used to identify and study such determinants. The aspects regarding CLA are also cov- ered, focusing on the currently-available commercial and experimental vaccines.
bovine farcy in 1888 by Nocard. Preisz, in 1894, was the first to completely describe this microorganism and to observe its resemblance to the diphtheria bacillus. Synonyms for C. pseudotuberculosis were Bacillus pseudotuberculosis ovis, Bacillus pseudotuberculosis, Corynebacterium ovis and Preisz-Nocard bacillus [59, 72]. This microorganism is a facultative intracellular pathogen that exhibits pleo- morphic forms, such as coccoids and fila- mentous rods, ranging in size from 0.5 μm to 0.6
μm by 1.0 μm to 3.0 μm [17, 28, 72, 97]. It is a non-sporulating, non-capsulated and non-motile bacterium; however, it has fimbriae [17, 46, 72]. This bacterium is a facultative anaerobe and grows best at
The role of C. pseudotuberculosis in pathogenesis 203
37 °C, at a pH of 7.0 to 7.2 [17, 72, 97]. It grows sparse initially on the agar surface and then becomes organized in clumps or in palisades, taking on a cream to orange col- oration; colonies are dry, opaque and con- centrically ringed. Growth in fluid medium develops as a granular deposit with a sur- face pellicle [17, 72, 77]. Haemolysis on blood agar is variable, but large zones develop in the presence of Rhodococcus equi [17]. C. pseudotuberculosis toxin inhibits the action of staphylococcal β-lysin [59].
C. pseudotuberculosis stains Gram- positive and when stained by Albert’s or Neisser’s method, volutin granules can be visualized. These metachromatic granules are clearly observed in the bacillary form, but are absent from coccoid cells; they con- tain high-energy phosphate reserves [46, 72].
2.2. Biochemical properties Cell wall peptidoglycan is based on meso-diaminopimelic acid (meso-DAP). Arabinose and galactose are major cell wall sugars. Short-chain mycolic acids (coryno- mycolic acids, 22–36 carbon atoms) are present [59, 94, 97]. Biochemical reactions of C. pseudotuberculosis isolates vary con- siderably, mainly in their fermenting ability [72, 100, 105]. All strains produce acid, but not gas, from many carbon sources, includ- ing glucose, fructose, maltose, mannose, and sucrose [17, 53, 59, 72]. This bacterium is phospholipase D and catalase positive, oxidase negative, and it is beta-hemolytic [59, 77, 100]. Strains isolated from small ruminants generally do not reduce nitrate [17, 72, 100, 114]. A well-established biochemical test for coryneform bacteria identification is the API Coryne system (API-bioMérieux, Inc., La Balme les Grottes, France). This method consists of 21 biochemical tests; it can be performed in 24–48 h. The test contains 20 tubes containing substrates that allow for 11 enzyme tests (pyrazinamidase, pyrrolidonyl arylamidase, β-galactosidase, alkaline phosphatase, α-glucosidase, N- acetylglucosaminidase, β-glucuronidase, and nitrate reduction and gelatin, urea and escu- lin hydrolysis) and eight carbohydrate fer- mentation tests (glucose, ribose, D-xylose, mannitol, maltose, lactose, sucrose and gly- cogen). This system is more reliable and rapid when it is compared with standard identification methods (API-bioMérieux, Inc.). A summary of general biochemical properties of C. pseudotuberculosis is pre- sented in Table II. 2.3. Antimicrobial susceptibility The susceptibility pattern of C. pseudo- tuberculosis to antimicrobial agents varies among isolates obtained from various sources [28, 37, 66]. Muckle and Gyles [77], in a study of 26 strains isolated from lesions of caseous lymphadenitis in goats, reported that all strains were susceptible to the antibiotics ampicillin, chlorampheni- col, lincomycin, gentamicin, tetracycline, penicillin G and sulfamethoxazole-trimeth- oprim. Only three isolates were susceptible to neomycin, and all strains were resistant to streptomycin. Garg et al. [40] reported strains of C. pseudotuberculosis that were strongly resistant to penicillin but suscepti- ble to neomycin. A strain highly resistant to streptomycin (500 μg/mL) was observed in a study of 22 isolates of C. pseudotubercu- losis from sheep and goat abscesses [90]. Minimal inhibitory concentration (MIC) values for all isolates were similar for the various antimicrobial agents. Later studies also indicated a similarity of MIC values among strains [1, 29, 60]. However, Fern- ández et al. [35] found higher MIC values for several antimicrobial agents, in an anal- ysis of corynebacteria isolated from ewe mastitis. Olson et al. [82] grew C. pseudotuber-
duce the environment of a natural infection. They observed that this bacterium was highly resistant to all the drugs that they tested under such growth conditions.
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The role of C. pseudotuberculosis in pathogenesis 205
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