Chlamydophila psittaci

A Microbial Biorealm page on the genus Chlamydophila psittaci

Classification

Higher order taxa

Superkingdom: Bacteria, Superphylum: Chlamydiae/Verrucomicrobia group, Phylum: Chlamydiae, Class: Chlamydiae, Order: Chlamydiales, Family: Chlamydiaceae, Genus: Chlamydophila; Species: Chlamydophila psittaci

Species

Chlamydophila psittaci

previously known as Chlamydia psittaci

Description and significance

Chlamydophila psittaci is an obligate, intracellular, gram negative bacteria that occur as a parasite in eukaryotic cells. These cells are coccoid and non-motile, with sizes ranging from 0.2-1.5 m. The cylamydial cell envelope lacks peptidoglycan, but instead has an outer membrane containing lipopolysaccharide and a cytoplasmic membrane bilayer. (1,6,7)

Chlamydophila psittaci causes a systemic infectious disease, psittacosis, in the parrot family and other avian species. Chlamydophila psittaci is present in feces, nasal secretions, and feathers of infected birds and the bacterium may be transmitted to humans through inhalation of dust from the contaminated bird. In 1930, the largest epidemic of psittacosis affected 750-800 individuals leading to the isolation of C psittaci in Europe and the United States. A total of 923 human cases of psittacosis have been reported to the US Centers for Disease Control and Prevention from 1988 through 2003. (2,6,7)

Chlamydophila psittaci, for many years, was confirmed through isolating the organism through cell culture and required scraping of cells from the site of infection of patients. New techniques of polymerase chain reaction and ligase chain reaction has improved detection of these specimens. Diagnostic techniques involved fluorescence microscopy and enzyme-linked immunoassays. (6)

Chlamydophila psittaci infection may be treated through antimicrobial therapy such as tetracycline, doxycycline, erythromycin, and sulfonamides. (6)

Genome structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?

Cell structure and metabolism

Chlamydophila psittaci has a major outer membrane protein (MOMP), consisting of predominately Beta-sheet content, similar to the biochemical properties of porin protein. These channels are permeable to ATP and may be the route in which the bacterium takes advantage of nucleoside triphosphates. It is known that Chlamydophila psittaci obtain ATP and essential amino acids from the host cell. (6,8)

Ecology

Chlamydophila psittaci is a pathogen which interacts with the parrot family and other avian species. The bacterium may be transmitted to humans through handling of sick birds. Certain breeds of Chlamydophila psittaci may infect sheep, goats, and cows. Chlamydophila psittaci does not have any direct contribution to the environment because it cannot live outside its host.

Pathology

Chlamydophila psittaci causes an infection through the respiratory system by using chlamydial elementary bodies to attach to the respiratory epithelial cells of the host and is engulfed through phagocytosis. Elementary bodies spread via the blood steam to the reticuloendothelial system and become reticulate bodies which depend on host cell ATP to grow. Within the inclusion of the host cell, reticular bodies under binary fission for 8-10 hours after infection and continue to divide for 20 hours. Reticular bodies give rise to elementary bodies after 20 hours of infection. After 48-72 hours, the cycle is completed and the infected host cell’s inclusion becomes filled with 10-1000 elementary bodies. Elementary bodies are released after lysis of cell and may infect fresh host cells. (3,6,7)

Chlamydophila psittaci affects the parrot family and other avian species. Once infected, these species will be susceptible to symptoms such as appetite and weight loss, diarrhea, sinusitis, and respiratory distress. Humans contract the disease through handling sick birds. Symptoms in humans include fever, cough, dyspnea, mild phryngitis, epistaxis, severe headache, and pneumonia. Certain breeds of Chlamydophila psittaci may also infect sheep, goats, and cows. (3,6)

Application to Biotechnology

Chlamydophila psittaci is not known to produce any useful compounds or enzymes. Due to its harmful pathogenic nature, studies have been developed to find vaccinations against this bacterium. Current research has found that the major outer membrane protein gene of Chlamydophila psittaci may serve as a target for vaccination. (10)

Current Research

The first study involves the study of the major outer membrane protein encoded by the outer membrane protein 1 (omp1) gene as a candidate for a vaccine against avian chlamydiosis. Pathogen free chicks were inoculated. Detection through an indirect hemagglutination test showed that these chicks generated antibodies against the major outer membrane protein of Chlamydophila psittaci. 9 out of 10 vaccinated chicks were protected from the disease when challenged, whereas the control groups showed clinical signs of the disease when challenged. This study shows that the major outer membrane protein gene of Chlamydophila psittaci may serve as a candidate vaccine against avian chlamydiosis (10)

The second study examines whether Atherosclerosis, a common disease in birds, is caused by the pathogen Chlamydophila psittaci. Out of 103 cases of advanced stages of atherosclerosis, only 4 (3.9%) were positive of chlamydiae in atherosclerotic tissue. Sequential analysis revealed high correlation (94%-100%) with Chlamydophila psittaci in three of the cases. Because of the low occurrence (3.9%) in advanced stages of Atherosclerosis, a relationship between chlamydiae and atherosclerosis in pet birds is improbable. (11)

The third study explores Chlamydophila psittaci genotype E/B transmission from parrots to humans. The presence of Chlamydophila psittaci was examined in a parrot relief and breeding center. 5 of 20 African grey parrots showed depression, ruffled feathers, loss of weight and mild dyspnoea. The manager also showed signs of shortness of breath. Chlamydophila psittaci genotype E/B was identified as the transmitted strain and it is believed that this is the first genotype E/B strain transmitted from parrot to human. Studies reveal that this genotype E/B strain shows no severe clinical symptoms in both parrots and humans. (12)

References

1. Everett, K., Hatch, T. “Architecture of the Cell Envelope of Chlamydia psittaci 6BC” Journal of Bacteriology 1995 Feb. p. 877-82.

2. Vanrompay, D., Harkinezhad, T., Walle M., Beeckman D., Droogenbroeck, C., Verminnen, K., Leten, R., Martel, A., Cauwerts K. “Chlamydophila psittaci Transmission from Pet Birds to Humans” Emerging Infectious Diseases. 2007 July. Volume 13.

3. Lessnau, K., Arjomand F., “Psittacosis” 2006 May

4.

5. Chlamydophila psittaci plasmid pCpA1, complete sequence

6. Lederberg, J., “Encyclopedia of Microbiology Second Edition Volume 1 A-C.” 2000. p. 781-787

7. Singleton, P., Saisbury, D. “Dictionary of Microbiology and Molecular Biology 3rd Edition.” 2001. p154.

8. Wyllie, S., Asley, R., Longbottom, D., Herring, A., “The Major Outer Membrane Protein of Chlamydophila psittaci Functions as a Porin-like Ion Channel.” 1998.

9. Tanzer, R., Longbottom, D., Hatch, T., “Identification of Polymorphic Outer Membrane Proteins of Chlamydia psittaci 6BC

10. Zhou, J., Qiu., C., Cao, XA, Lin G., “Construction and immunogenicity of recombinant adenovirus expressing the major outer membrane protein (MOMP) of Chlamydophila psittaci in chicks.” 2007

11. Schenker, OA, Hoop, RK. “Chlamydiae and atherosclerosis: can psittacine cases support the link? 2007

12. Harkinezhad, T., Verminnen, K., Droogenbroeck, C., Vanrompay, D., “Chlamydophila psittaci genotype E/B transmission from African grey parrots to humans.” 2007

Edited by Coleman Ho, student of Rachel Larsen