Bordetella avium

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Bordetella avium
Systematics
Department : Proteobacteria
Class : Betaproteobacteria
Order : Burkholderiales
Family : Alcaligenaceae
Genre : Bordetella
Type : Bordetella avium
Scientific name
Bordetella avium
Kersters et al., 1984

Bordetella avium is a gram-negative , rod-shaped, obligate aerobic bacterium from the genus Bordetella . It is of veterinary importance as an infectious agent in poultry , hence the species name avium ( genitive plural from Latin avis "bird"). The disease primarily affects turkeys and is known as turkey flu . Bordetella avium is characterized by a lack of urea cleavage and nitrate reduction , which distinguishes it from Bordetella bronchiseptica . The genome of the Bordetella avium 197N bacterial strain was completely sequenced in 2006.

features

Appearance

The cells of Bordetella avium are short rods . They are gram negative . The cells are 1.0–2.0 µm long and 0.4–0.5 µm wide. The species is - like Bordetella bronchiseptica - motile , it can move independently with the help of five to eight peritrichally arranged flagella . The formation of the flagella depends on the growth temperature; cultures incubated at 20 ° C contain more flagellated cells than cultures grown at 35 ° C. This effect does not occur with B. bronchiseptica . Endospores are not formed. The cells have pili (fimbriae) on their surface and are surrounded by a capsule . In the light microscope image, they appear individually or in pairs.

On solid culture media , the cells grow into very small colonies , these are transparent. Their diameter is less than 1.0 mm. Unlike the classic Bordetella species, there is no hemolysis on blood agar . Colonies of B. avium can form brown pigments on peptone- containing culture media that do not contain blood , but the pigmentation occurs less frequently than in B. parapertussis , so that the characteristic for the species is stated as variable. Similar to B. bronchiseptica , colonies of B. avium also have SR modulation. The abbreviations S and R stand for the appearance of the colonies, English smooth , "smooth" and English rough , "rough" (compare Griffith's experiment ). This behavior is most likely to occur on blood agar, where the rough colonies are larger. A change from the S to the R form can occur spontaneously, but this was only observed in three strains when investigating 28 bacterial strains.

Growth and metabolism

The metabolism of Bordetella avium is based on breathing , the species is strictly aerobic , so it needs oxygen to grow. The catalase test and the oxidase test are positive. Furthermore, the metabolism can be characterized as chemoorganotrophic and heterotrophic , B. avium uses organic compounds as an energy source and also to build up the cells' own substances. It is asaccharolytic, i.e. H. it cannot utilize sugar (e.g. glucose ); instead, amino acids are among the substrates that are broken down. This must be taken into account when choosing the right nutrient medium for cultivation , whereby B. avium is not as demanding as B. pertussis .

The optimal temperature for growth is 37 ° C. The Bordet Gengou blood agar , which is also used for B. parapertussis (see there), is suitable for cultivation . Simple nutrient media are also suitable if they contain amino acids or peptones . Furthermore, the cultivation is successful on MacConkey agar and Salmonella Shigella agar. Colonies can be seen after incubation for 1-2 days at 37 ° C. The bacterial culture grown on the nutrient media can then be examined biochemically in order to distinguish it from the related Bordetella species.

Biochemical features, such as the enzymes present and the resulting metabolic properties, can be used in a colorful series to identify B. avium . In addition to the positive catalase and oxidase test, the following features can be used: It does not reduce nitrate , i. H. Nitrate is not reduced to nitrite . The urease test turns out negative, the species is not able to break down urea . Gelatin cannot be broken down by hydrolysis either, nor does aesculin hydrolysis take place. The indole test is negative. Since no carbohydrates are broken down, there is no acid formation either, so the methyl red test is also negative. It can break down the amino acids L - aspartic acid , L - glutamic acid and L - proline . Other organic compounds that can be used as an energy source and to build up the cells' own substances are citrate , pyruvate , succinate , fumarate and glutarate . B. avium can be distinguished from the other species on the basis of some characteristics (see overview ).

genetics

The genome of the Bordetella avium 197N bacterial strain (also known as ATCC BAA-1003) was completely sequenced in 2006 . This is a strain that was isolated from a diseased turkey from a poultry farm in Ohio , USA , in the early 1980s . The genome has a size of 3732 kilobase pairs (kb), which is about 80% of the genome size of Escherichia coli . It exists as a circular bacterial chromosome . There are 3381 proteins annotated . The GC content (the proportion of the nucleobases guanine and cytosine ) in the bacterial DNA is around 62 mol percent, while the GC content of the classic Bordetella species is slightly higher at 68 mol percent.

A comparison with the genome sizes of B. bronchiseptica (5339 kb), B. parapertussis (4774 kb) and B. pertussis (4086 kb) determined in 2003 shows that the genome of B. avium is the smallest. One possible explanation is adaptation to a host , in this case poultry , while B. bronchiseptica can infect numerous mammals as a host. Due to the host restriction, genes that are no longer “required” have been lost. More than 1100 genes have been identified in the genome that are not found in B. bronchiseptica and that are associated with host adaptation. These are predominantly genes that code for proteins that are suitable as surface proteins or secretory proteins for adaptation to the respiratory tract of birds and not of mammals.

Pathogenicity

Although opportunistic infections occur applies Bordetella avium generally considered non-pathogenic (not "pathogenic") for the people . The Biological Agents Ordinance in conjunction with the TRBA ( Technical Rules for Biological Agents) 466 assigns it to risk group 2, so that it is established that it can cause illness in humans. However, this is further explained by a note: It is pathogenic for vertebrates, humans are not attacked under natural conditions. According to the protection concept of the Biological Agents Ordinance for employees who work with biological agents , this takes into account that there is a risk of infection when handling high concentrations of pathogens.

The genetic investigation (2006) aimed to learn more about the virulence factors of B. avium . The best-studied species, Bordetella pertussis (pathogen that causes whooping cough ), has numerous virulence factors, such as filamentous hemagglutinin (FHA) and pertussis toxin (PT), a protein that acts as an exotoxin and adhesin . Compared to the classic brothel, B. avium only features a few of these factors. These include filamentous hemagglutinin (FHA), the fimbriae that act as antigens , tracheal cytotoxin (TCT) and the heat-labile toxin. The latter is said to have a skin-necrotizing effect, which is why it is also referred to as dermanecrotic toxin (English dermonecrotic toxin , DNT). On the other hand, the pertussis toxin and the hemolysin (CyaA) formed by adenylate cyclase can not be found in B. avium ; they do not seem to play a role in the infection of birds, so that the genes coding for them have been lost.

Occurrence

The studies that led to the discovery of Bordetella avium included 28 bacterial strains. These were mostly isolated from turkeys. The turkey is also called the house turkey, it is the domesticated form of the turkey . In addition, strains of a chicken , a duck , a goose and a bronze male (a genus from the finch family ) were isolated. The isolates come from different geographic areas such as the USA , Spain , France , the United Kingdom (UK), Germany , Israel and Japan . In serological tests on various birds over the period from 1998 to 2000, B. avium was found in 41 of the 61 species examined, including the mallard , the Canada goose and the wild turkey. Similar to B. bronchiseptica , B. avium can also survive in the environment for a long time and was also found in water.

Systematics

External system

Bordetella avium is one of several species from the genus Bordetella in the family of the Alcaligenaceae , this is placed in the order of the Burkholderiales in the class of the Betaproteobacteria . One of the bacterial strains that were assigned to the species in the first description was previously included in the species Alcaligenes faecalis ( type species of the genus Alcaligenes ). In fact, the phylogenetic studies by Kersters et al. a. a close relationship of B. avium with Alcaligenes denitrificans (meanwhile called Achromobacter denitrificans ) and Achromobacter xylosoxidans (meanwhile regarded as a subspecies of Achromobacter denitrificans ).

Internal system

The species B. bronchiseptica , B. pertussis and B. parapertussis of the genus Bordetella have been known since the first half of the 20th century. They are also referred to as “classic” Bordetella species and are strikingly similar, so that classification as subspecies is also being discussed. Bordetella avium was developed in 1984 by Karel Kersters et al. discovered and first described as the fourth Bordetella species. As mentioned, a bacterial strain previously assigned to the species Alcaligenes faecalis was also identified as B. avium . However, this is based on the earlier, incorrect assignment of the strain, so Alcaligenes faecalis is not a synonym .

In addition to the phylogenetic investigations (especially on the 16S rRNA, a typical representative of ribosomal RNA for prokaryotes ), phenotypic characteristics were also compared and polyacrylamide gel electrophoresis of the bacterial proteins was carried out. This showed that B. avium belongs to the genus Bordetella , since there are more similarities with the species known at the time than with the representatives of the related genera Alcaligenes or Achromobacter . Further genetic studies from 2006 confirm, however, that B. avium phylogenetically is relatively far from the classic brothel. The B. avium ATCC 35086 strain is the type strain of the species. So far (as of 2014) only the genome of the B. avium 197N strain has been fully investigated. Several bacterial strains are deposited in different collections of microorganisms .

etymology

The generic name was chosen in honor of the Belgian microbiologist Jules Bordet . The specific epithet refers to the occurrence and meaning as an infectious agent in poultry, avium ( genitive plural from Latin avis , "bird") means "the birds" (genitive).

Veterinary importance

Bordetella avium is of veterinary importance as a causative agent of an infectious disease in poultry. An infection with B. avium - just like an infection with B. bronchiseptica in mammals - is referred to in veterinary medicine as bordetellosis ( English bordetellosis ). The term avian Bordetellose is also used. The common in turkeys infectious disease is then turkey coryza ( English turkey coryza called), with coryza synonymous with rhinitis is ( "runny nose"). It cannot be distinguished from turkey rhinotracheitis (caused by a pneumovirus) based on its symptoms .

Similar to the classic species B. pertussis and B. parapertussis in humans and B. bronchiseptica in a large number of mammals, the ciliated epithelial cells of the respiratory tract are the target of the pathogen. In B. avium , the upper respiratory tract (respiratory tract) is primarily affected; according to the medical terms for diseases of the nose and trachea , this is known as rhinotracheitis. The disease is similar in poultry to the corresponding infections in other hosts from the related species. Since B. avium can survive in the environment for a long time, for example in water and dilute saline solutions, it is assumed that a smear infection is a possible route of infection . It is common for the pathogen to be transmitted by droplets ( droplet infection ), which sick animals give off by sneezing.

B. avium infects numerous domesticated poultry species, as well as their relatives living as wild animals . Turkeys (domestic turkeys) in poultry farms are particularly sensitive, but the wild form of the turkey ( Meleagris gallopavo ) is also affected. The infection is highly contagious and occurs not only in turkeys but also in chickens , geese and ducks . Especially in turkey chicks in the first month of life there is a complex of nasal mucous membrane inflammation , sinusitis , conjunctivitis , inflammation of the trachea and sometimes even bronchial and pneumonia . The incubation period is 7-11 days. In an affected herd, the morbidity can be 80–100%. Avian brothel lots are an economic problem in turkey fattening in the USA. B. avium infection is often made worse by secondary infection with other bacteria or viruses. The sick birds do not gain enough weight, and deaths also occur.

Live vaccines have already been tested for prevention, but no approved preparation is yet available in Germany. Various antibiotics can be used for therapy , for example from the group of tetracyclines . A 2013 study published in the US in more than 20 isolates were obtained over an extended period of sick turkeys, shows a resistance of B. avium to multiple antibiotics, even to tetracyclines. Most isolates are resistant to erythromycin , several to ampicillin . All isolates examined are resistant to aztreonam , so this antibiotic is recommended as an additive in the nutrient medium in order to cultivate B. avium selectively. The microbiological examinations by means of an antibiogram or the determination of the minimum inhibitory concentration , however , showed the sensitivity of B. avium to aminoglycoside antibiotics ( amikacin , gentamicin ), cephalosporins such as cefoperazone , ceftazidime and cefepime as well as piperacillin .

swell

literature

  • Karel Kersters, Karl-Heinz Hinz a. a .: Bordetella avium sp. nov., Isolated from the Respiratory Tracts of Turkeys and Other Birds . In: International Journal of Systematic Bacteriology . tape 34 , no. 1 , 1984, p. 56–70 , doi : 10.1099 / 00207713-34-1-56 ( PDF, 3.7 MB [accessed on March 2, 2014]).
  • Hans-Joachim Selbitz, Uwe Truyen, Peter Valentin-Weigand: Veterinary microbiology, infection and disease theory . 8th edition. Enke Verlag, Stuttgart 2010, ISBN 978-3-8304-1080-5 , p. 169-172 .

Individual evidence

  1. ↑ a b c d e f g h i j k l K. Kersters, K.-H. Hinz u. a .: Bordetella avium sp. nov., Isolated from the Respiratory Tracts of Turkeys and Other Birds. In: International Journal of Systematic Bacteriology. Volume 34, No. 1, January 1984, pp. 56-70, ISSN  0020-7713 . doi: 10.1099 / 00207713-34-1-56 .
  2. ↑ a b F. von Wintzingerode, A. Schattke u. a .: Bordetella petrii sp. nov., isolated from an anaerobic bioreactor, and emended description of the genus Bordetella. In: International journal of systematic and evolutionary microbiology. Volume 51, No. 4, July 2001, pp. 1257-1265, ISSN  1466-5026 . doi: 10.1099 / 00207713-51-4-1257 . PMID 11491321 .
  3. ↑ a b c d e f g h i j M. Sebaihia, A. Preston u. a .: Comparison of the genome sequence of the poultry pathogen Bordetella avium with those of B. bronchiseptica, B. pertussis, and B. parapertussis reveals extensive diversity in surface structures associated with host interaction. In: Journal of bacteriology. Volume 188, No. 16, August 2006, pp. 6002-6015, ISSN  0021-9193 . doi: 10.1128 / JB.01927-05 . PMID 16885469 . PMC 1540077 (free full text).
  4. ↑ a b Bordetella avium 197N. In: Website Genomes Online Database (GOLD). Retrieved March 3, 2014 .
  5. ^ Bordetella avium. In: National Center for Biotechnology Information (NCBI) Genome website . Retrieved March 3, 2014 .
  6. ↑ J. Parkhill, M. Sebaihia et al. a .: Comparative analysis of the genome sequences of Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica. In: Nature genetics. Volume 35, No. 1, September 2003, pp. 32-40, ISSN  1061-4036 . doi: 10.1038 / ng1227 . PMID 12910271 .
  7. ↑ AT Harrington, JA Castellanos u. a .: Isolation of Bordetella avium and novel Bordetella strain from patients with respiratory disease. In: Emerging infectious diseases. Volume 15, No. 1, January 2009, pp. 72-74, ISSN  1080-6059 . doi: 10.3201 / eid1501.071677 . PMID 19116056 . PMC 2660683 (free full text).
  8. ↑ TRBA (Technical Rules for Biological Agents) 466: Classification of prokaryotes (Bacteria and Archaea) into risk groups. In: Website of the Federal Institute for Occupational Safety and Health (BAuA). April 25, 2012, p. 42 , accessed January 7, 2014 .
  9. ↑ TR Raffel, KB Register u. a .: Prevalence of Bordetella avium infection in selected wild and domesticated birds in the eastern USA. In: Journal of wildlife diseases. Volume 38, No. 1, January 2002, pp. 40-46, ISSN  0090-3558 . doi: 10.7589 / 0090-3558-38.1.40 . PMID 11838227 .
  10. ↑ a b c d Jean Euzéby, Aidan C. Parte: Genus Bordetella. In: List of Prokaryotic names with Standing in Nomenclature ( LPSN ). Retrieved March 2, 2014 .
  11. ^ Jean Euzéby, Aidan C. Parte: Phylum "Proteobacteria". In: List of Prokaryotic names with Standing in Nomenclature Systematics of Bacteria (LPSN). Retrieved March 2, 2014 .
  12. ↑ J. Park, Y. Zhang and a .: Comparative genomics of the classical Bordetella subspecies: the evolution and exchange of virulence-associated diversity amongst closely related pathogens. In: BMC genomics. Volume 13, October 2012, p. 545, ISSN  1471-2164 . doi: 10.1186 / 1471-2164-13-545 . PMID 23051057 . PMC 3533505 (free full text).
  13. ↑ Taxonomy Browser Bordetella avium. In: National Center for Biotechnology Information (NCBI) website. Retrieved March 4, 2014 .
  14. ^ Strain Passport Bordetella avium. In: StrainInfo website (information collected about bacterial strains in over 60 biological resource centers (BRCs)). Retrieved March 4, 2014 .
  15. ↑ a b c d e Hans-Joachim Selbitz, Uwe Truyen, Peter Valentin-Weigand: Veterinary microbiology, infection and disease theory . 8th edition. Enke Verlag, Stuttgart 2010, ISBN 978-3-8304-1080-5 , p. 169-172 .
  16. ↑ a b c d N. M. Beach, S. Thompson et al. a .: Bordetella avium antibiotic resistance, novel enrichment culture, and antigenic characterization. In: Veterinary microbiology. Volume 160, No. 1-2, November 2012, pp. 189-196, ISSN  1873-2542 . doi: 10.1016 / j.vetmic.2012.05.026 . PMID 22721730 . PMC 3469198 (free full text).
  17. ↑ BA Hopkins, JK Skeeles et al. a .: A survey of infectious diseases in wild turkeys (Meleagridis gallopavo silvestris) from Arkansas. In: Journal of wildlife diseases. Volume 26, No. 4, October 1990, pp. 468-472, ISSN  0090-3558 . doi: 10.7589 / 0090-3558-26.4.468 . PMID 2250323 .