Characterization of Virulence Plasmids and Serotyping of Rhodococcus equi Isolates from Submaxillary Lymph Nodes of Pigs in Hungary

Abstract

The plasmid types and serotypes of 164 Rhodococcus equi strains obtained from submaxillary lymph nodes of swine from different piggeries in 28 villages and towns located throughout the country were examined. The strains were tested by PCR for the presence of 15-to 17-kDa virulence-associated protein antigen (VapA) and 20-kDa virulence-associated protein antigen (VapB) genes. R. equi is an aerobic, gram-positive coccobacillus which frequently causes chronic suppurative bronchopneumonia with abscesses, lymphadenitis, and ulcerative enteritis in foals less than 6 months old (3,14). In addition to its virulence for foals, R. equi seems also to be an important pathogen to immunocompromised humans, such as organ transplant and AIDS patients (21). R. equi is also common in the submaxillary lymph nodes of pigs (2,8,15,25,27). Katsumi and others (8) isolated R. equi from 45.6% of the submaxillary lymph nodes of swine with lesions and from 9.4% of lymph nodes of swine without lesions. Takai and colleagues (19) described a 3.1% isolation rate on the basis of examination of 1,832 submaxillary lymph nodes collected from swine.Recently, the discovery of virulence-associated antigens and virulence plasmids has allowed classification of the virulence of More recently, we demonstrated that five of the seven clinical isolates of R. equi from immunocompromised patients expressed VapB and that they were of intermediate virulence and revealed that these human isolates contained a 95-kb type 5 plasmid which was also seen in the pig isolates in Hungary (10). The route of infection in human cases is not clear. The purpose of this study was to isolate virulent R. equi strains from submaxillary lymph nodes of swine in Hungary, to determine the genotypic diversity of virulence-associated plasmids found in them, and to examine the serotypes of the isolates with the aim of finding additional data to characterize the epidemiological relationship between human R. equi infections and pigs carrying R. equi in the submaxillary lymph nodes.Serotyping is a reliable method for examining R. equi strains. There are two systems for serotyping R. equi. Prescott de-* Corresponding author. Mailing address:

Intermediately virulent Rhodococcus equi isolates from pigs in Slovenia: discovery of new plasmid types and assessment of genetic diversity by pulsed-field gel electrophoresis

“…The studies on this topic report conflicting results: some authors recovered R. equi from the lymph nodes of healthy pigs (Takai et al, 1996;Madarame et al, 1998;Dvorska et al, 1999;Makrai et al, 2005) while others reported the isolation of R. equi almost exclusively from lymph nodes with granulomatous lesions, identifying it as the causative agent of lymphadenitis in pigs (Komijn et al, 2007). In the scope of one study, R. equi was found in pigs with and without caseous lymphadenitis, but the isolation rate was reported to be five times higher in the lymph nodes with lesions (Katsumi et al, 1991).…”

“…Takai and Tsubaki (1985) and Takai et al (1996) found R. equi in 21.7% and 3.1% of investigated submaxillary lymph nodes of apparently healthy pigs, respectively. Recently, an isolation rate of 14.0% was reported from swine submaxillary lymph nodes without macroscopic lesions in Hungary (Makrai et al, 2005).…”

“…However, the organism can be isolated with similar frequency from the lymph nodes and tonsils of otherwise healthy pigs (Karlson et al, 1940;Barton and Hughes, 1980;Takai et al, 1996;Makrai et al, 2005). The causative role of R. equi in granulomatous lymphadenitis in swine is unclear.…”

“…Infection can also occur in a wide variety of other mammals, usually due to immunosuppression (Prescott, 1991). R. equi is frequently isolated from the lymph nodes of pigs (Barton and Hughes, 1980;Katsumi et al, 1991;Prescott, 1991;Takai et al, 1996;Pate et al, 2004;Makrai et al, 2005;Shitaye et al, 2006;Komijn et al, 2007); it also seems to be gaining importance in human health (Jones et al, 1989;Kedlaya et al, 2001;Weinstock and Brown, 2002;Torres-Tortosa et al, 2003;Ulivieri and Oliveri, 2006). Increased numbers of human R. equi infections might be a consequence of the AIDS epidemic but may also reflect the increasing awareness of this opportunistic pathogen (Prescott, 1991).…”

Isolation of Rhodococcus equi from Wild Boars (Sus scrofa) in Japan

“…We isolated R. equi from the lymph nodes with NANAT agar plates as described (Takai et al, 1996). Strain ATCC 33701 and 27 representative strains of intermediate virulence were used as reference strains because their plasmid characteristics and virulence levels have been described (Takai et al, 1996(Takai et al, , 2003Fukunaga et al, 1999;Makrai et al, 2005Makrai et al, , 2008. Plasmid profiles and the presence of vapA and vapB genes were determined by PCR as described (Makrai et al, 2008), and serum samples of wild boars were analyzed for anti-R. equi-specific antibodies by western blotting (Takai et al, 1991) with anti-pig immunoglobulin antibodies conjugated to horseradish peroxidase (Cappel Laboratories, Richmond, California, USA).…”