Brachyspira

Brachyspira
Scientific classification
Kingdom:	Bacteria
Phylum:	Spirochaetes
Class:	Spirochaetes Cavalier-Smith 2002
Order:	Spirochaetales Buchanan 1917
Family:	Spirochaetaceae Swellengrebel 1907
Genus:	Brachyspira Hovind-Hougen et al. 1983
Species
Brachyspira aalborgi Hovind-Hougen et al. 1983 Brachyspira alvinipulli Stanton et al. 1998 Brachyspira canis ♠ Oxberry and Hamspon 2003 Brachyspira corvi ♠ Jansson et al. 2008 Brachyspira hampsonii ♠ Chander et al. 2012 Brachyspira hyodysenteriae (Harris et al. 1972) Ochiai et al. 1998 Brachyspira ibaraki ♠ Tachibana et al. 2003 Brachyspira innocens (Kinyon and Harris 1979) Ochiai et al. 1998 Brachyspira intermedia (Stanton et al. 1997) Hampson and La 2006 Brachyspira murdochii (Stanton et al. 1997) Hampson and La 2006 Brachyspira pilosicoli (Trott et al. 1996) Ochiai et al. 1998 Brachyspira muridarum ♠ Backhans et al. 2010 Brachyspira muris ♠ Backhans et al. 2010 Brachyspira pulli ♠ Stephens and Hampson 2001 Brachyspira rattus ♠ Backhans et al. 2010 Brachyspira suanatina ♠ Rasback et al. 2007

Brachyspira is a genus of bacteria classified within the phylum Spirochaetes.^{[1] [2]}

Significance

Brachyspira species include known pathogens in animals, mostly pigs but also birds, dogs, and humans while some species like B. innocens or B. intermedia are considered harmless commensals in animals.

B. hyodysenteriae and B. pilosicoli are the classic Brachyspira gastrointestinal pathogens leading to diarrheal disease in growing pigs worldwide, causing the so-called swine dysentery, typhlocolitis or porcine intestinal spirochaetosis, which contributes to major "production losses" in agrobusiness.

B. intermedia and B. pilosicoli can cause disease in poultry.

B. pilosicoli can infect humans leading to human intestinal spirochaetosis, however most cases of HIS are caused by B. aalborgi, so its clinical relevance remains unclear.

Change in ecology

In the U.S.A. Brachyspira-associated pig disease and isolation of Brachyspira species from swine with diarrheal disease largely disappeared from swine herds in the late 1990s and early 2000s, but returned in the mid-2000s for unknown reasons.

A 2011 study of isolates from Midwestern swine herds described major changes in Brachyspira spp frequency and hemolysis, i.e. pathogenicity: the majority of isolated Brachyspira species were previously considered minimally pathogenic or commensal, like Brachyspira murdochi (27%)or novel/unclassifiable Brachyspira species (25%), while only 40.5% of 79 isolates from diseased pigs could be confirmed as the classic pathogens B. hyodysenteriae or Brachyspira pilosicoli by PCR.^[3] Brachyspira species previously capable of weak hemolysis only, like B. intermedia and B. pilosicoli were found to produce strong hemolysis. They were also frequently identified from diseased swine which suggests they are emerging pathogens.

A compelling explanation for this change in epidemiology and ecology is selection by the increasing use of antibiotics in pigs (e.g. as growth promoters), since B. murdochii and unclassifiable Brachyspira spp. are less susceptible to antimicrobials than the previously established Brachyspira pathogens.

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)^[4] and National Center for Biotechnology Information (NCBI),^[5] and the phylogeny is based on 16S rRNA-based LTP release 111 by The All-Species Living Tree Project.^[6]

?B. canis ♠ Oxberry and Hamspon 2003 ?B. corvi ♠ Jansson et al. 2008 ?B. ibaraki (presumably an 16S-rDNA variant of B. aalborgi)[7] ♠ Tachibana et al. 2003 ?B. hampsonii ♠ Chander et al. 2012 ?B. muridarum ♠ Backhans et al. 2010 ?B. muris ♠ Backhans et al. 2010 ?B. pulli Stephens and Hampson 2001 ?B. rattus ♠ Backhans et al. 2010 ?B. suanatina ♠ Rasback et al. 2007 B. aalborgi Hovind-Hougen et al. 1983 (type sp.) B. hyodysenteriae (Harris et al. 1972) Ochiai et al. 1998 B. innocens (Kinyon and Harris 1979) Ochiai et al. 1998 B. murdochii (Stanton et al. 1997) Hampson and La 2006 B. intermedia (Stanton et al. 1997) Hampson and La 2006 B. alvinipulli Stanton et al. 1998 B. pilosicoli (Trott et al. 1996) Ochiai et al. 1998

♠ Strains found at the National Center for Biotechnology Information (NCBI) but not listed in the List of Prokaryotic names with Standing in Nomenclature (LSPN).

Microbiologic identification

Brachyspira are capable of hemolysis, the degree of which has been used to characterize them, with B. hyodysenteriae showing strong beta hemolysis while B. pilosicoli, B. intermedia, B. murdochii, and B. innocens have been described as weakly hemolytic.^[8] However in a recent study from Iowa State University, all (10/10) B. intermedia isolates, 91% (9/11) of Brachyspira spp. isolates, and 20% (2/6) of B. pilosicoli isolates from farms in North Carolina (36), Iowa (23), Minnesota (9), Nebraska (3), Michigan (2), Illinois (2), Missouri (1), North Dakota (1), South Dakota (1), and Ohio (1), demonstrated strong beta-hemolysis.^[9]

Antibiotic treatment

Veterinary antibiotics used to treat pigs with dysentery due to Brachyspira species include the lincosamide lincomycin, the ionophore salinomycin, the quinoxaline carbadox, the pleuromodulins tiamulin and valnemulin, as well as the aminoglycoside gentamicin, an important antibiotic used in humans.

Antibiotic resistance

Brachyspira resistance to the above antibiotics has been increasingly reported. While no Clinical and Laboratory Standards Institute (CLSI) antimicrobial breakpoints for Brachyspira have been established, resistance to the pleuromutilins tiamulin and valnemulin is considered at MIC ≥ 2 µg/ml.^[10] Resistance to pleuromutilins is important, because they are antibiotics of "last resort"; as of 2001, they were the only antibiotics with sufficient minimum inhibitory concentration (MIC) values left to treat swine dysentery in Sweden, per the National Veterinary Institute in Uppsala.^[11]

Antibiotic resistance varies by geographic region and is not developing as rapidly in U.S. isolates as has been seen in isolates from other countries.^[9] Tiamulin resistance was first described in 1996 in Hungary,^[12] and subsequently reported from other countries in Europe and Asia,.^{[13][14][15][16][17][18]} In Spain, 7.4% of Brachyspira isolates were reported to be venamulin resistant and 17.6% were tiamulin resistant in 2009.^[19] In Sweden, 10-15% of B. pilosicoli isolates between 2002 and 2010 were resistant to tiamulin (MICs >4 μg/ml), and a gradual increase in tiamulin MICs was seen in B. hyodysenteriae between 1990 and 2003, which has since plateaued.^[20]

Decreased susceptibility to lincomycin, but not to tiamulin was found among Polish isolates.^[21]

In the USA, resistance of Brachyspira species collected 2008-2010 was common only against lincomycin (80% had MIC of 32 or 64), MIC's were moderatetly high against gentamicin, while resistance to valnemulin(4.7%) and tiamulin (3.2% of isolates) was yet uncommon, as reported in the only U.S. study to date, from Iowa.^[9]

The use of pleuromutilins in U.S. food animals is unfortunately not separately reported in the U.S. Food and Drug Administration's annual Animal Drug User Fee Act (ADUFA) report, "Antimicrobials Sold or Distributed for Use in Food-Producing Animals".^[22] However, the amount of 190 t of lincosamides used is substantial per ADUFA; Antibiotics used in the U.S. in food animals in 2011 was Ionophores 4,123,259 kg, Aminoglycosides 214,895 kg, and Lincosamides 190,101 kg.

References

1. See the List of Prokaryotic names with Standing in Nomenclature. Data extracted from J.P. Euzéby. "Spirochaetes". Retrieved 2011-11-17.
2. See the NCBI webpage on Spirochaetes Data extracted from Sayers; et al. "NCBI Taxonomy Browser". National Center for Biotechnology Information. Retrieved 2011-06-05.
3. Clothier KA, Kinyon JM, Frana TS, Naberhaus N, Bower L, Strait EL, Schwartz K.Species characterization and minimum inhibitory concentration patterns of Brachyspira species isolates from swine with clinical disease.J Vet Diagn Invest. 2011 Nov;23(6):1140-5.
4. J.P. Euzéby. "Brachyspira". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2013-03-30.
5. Sayers; et al. "Brachyspira". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2013-03-30.
6. All-Species Living Tree Project."16S rRNA-based LTP release 111 (full tree)" (PDF). Silva Comprehensive Ribosomal RNA Database. Retrieved 2013-03-30.
7. Westerman, L. J. (2013). Human Intestinal Spirochaetosis (PhD thesis).
8. Komarek V,Maderner A,Spergser J,Weissenböck H. Infections with weakly haemolytic Brachyspira species in pigs with miscellaneous chronic diseases. Vet Microbiol 134: 311–317.
9. Clothier KA, Kinyon JM, Frana TS, Naberhaus N, Bower L, Strait EL, Schwartz K.Species characterization and minimum inhibitory concentration patterns of Brachyspira species isolates from swine with clinical disease.J Vet Diagn Invest. 2011 Nov;23(6):1140-5.
10. Karlsson M,Fellström C, Johansson KE,Franklin A. Antimicrobial resistance in Brachyspira pilosicoli with special reference to point mutations in the 23S rRNA gene associated with macrolide and lincosamide resistance. Microb Drug Resist 2004. 10:204–208
11. Karlsson M, Gunnarsson A, Franklin A. Susceptibility to pleuromutilins in Brachyspira (Serpulina) hyodysenteriae. Anim Health Res Rev. 2001 Jun;2(1):59-65.
12. Molnàr, L. (1996). Vet. Rec. 138:158-160.
13. Gresham AC, Hunt BW, Dalziel RW.Treatment of swine dysentery--problems of antibiotic resistance and concurrent salmonellosis. Vet Rec. 1998 Nov 28;143(22):619.
14. Italy http://www.ivis.org/proceedings/ipvs/2006/TREATMENT/P_31-22.pdf?LA=1
15. Germany: Rohde J,Kessler M,Baums CG, Amtsberg G.Comparison of methods for antimicrobial susceptibility testing and MIC values for pleuromutilin drugs for Brachyspira hyodysenteriae isolated in Germany. Vet Microbiol 2004. 102:25–32.
16. Pringle M,Landén A,Franklin A. Tiamulin resistance in porcine Brachyspira pilosicoli isolates. Res Vet Sci 2006. 80:1–4.
17. Czech Republic: Lobová D, Smola J, Cizek A. Decreased susceptibility to tiamulin and valnemulin among Czech isolates of Brachyspira hyodysenteriae. J Med Microbiol 2004. 53:287–291.
18. Karlsson M. et al (2002). Proc. 17th IPVS Congr, p.189
19. Hidalgo A,Carvajal A, García-Feliz C,et al. Antimicrobial susceptibility testing of Spanish field isolates of Brachyspira hyodysenteriae. Res Vet Sci 2009. 87:7–12.
20. Pringle M, Landén A, Unnerstad HE, Molander B, Bengtsson B. Antimicrobial susceptibility of porcine Brachyspira hyodysenteriae and Brachyspira pilosicoli isolated in Sweden between 1990 and 2010.Acta Vet Scand. 2012 Sep 21;54:54.
21. Zmudzki J, Szczotka A, Nowak A, Strzelecka H, Grzesiak A, Pejsak Z.Antimicrobial susceptibility of Brachyspira hyodysenteriae isolated from 21 Polish farms.Pol J Vet Sci. 2012;15(2):259-65.
22. "Antimicrobials Sold or Distributed for Use in Food-Producing Animals" http://www.fda.gov/AnimalVeterinary/NewsEvents/CVMUpdates/ucm338178.htm accessdate 3-17-13