Spirochaetes
spirochetesSpirochaetes are helical Spirochaetes are a diverse group of spiral, motile organisms comprising two families: Spirochetaeceae Treponemataceae
Treponemataceae have three genera
Treponema causes syphilis, bejel yaws, pinta (spotting & discoloration of skin)and, oral treponema causes acute necrotizing ulcerative gingivitis (in the oral cavity together with fusobacteria) Borrelia causes relapsing fever and Lyme disease Leptospira causes leptospirosis. البريمياتCell wall of spirochete
the cell wall run three to five axial filaments that are fixed to the extremities of the organism. Contractions of these filaments distort the bacterial cell body to give it its helical shape. The organism moves either by rotation along the long axis or by flexion of cells.Identefication
The cell wall is similar to Gram-negative bacteria but stains poorly with the Gram stain Because of their weak refractile nature dark-ground microscopy is used to visualize these organisms in the laboratory although immunofluorescence is more useful for identification purposes. All spirochaetes are strictly anaerobic or microaerophilic.Treponema Spp.
Treponema pallidum(pathogenic) Sub species of Treponema pallidum Pallidum( syphilis) Pertenue(yaws) carateum(pinta) Endemicum(bejel) Oral treponemes( non pathogenic) like : Treponema denticolaOral treponemes
All oral spirochaetes are classified in the genus Treponema. Although many species have been described, only four have been cultivated and maintained reliably : Treponema denticola, Treponema vincentii, Treponema pectinovarum Treponema socranskiiAntibiotic sensitivity and control
Sensitive to penicillin and metronidazole. Prevention of infection is achieved by good oral hygiene practices.Habitat and transmission of oral Trponema
Predominantly, the oral cavity of humans and primates, at the gingival margin and crevice in particular. Transmission routes are unknown. Infections are endogenousPathogenicity
These organisms are a component of the fusospirochaetal complex of acute necrotizing ulcerative gingivitis Vincent’s anginaNoma( Cancrum oris)a coagent of advanced periodontal disease.Pathogenicity
Virulence factors are little known; endotoxin is possibly contributory to disease. T. denticola is more proteolytic than other species and degrades collagen and dentine. The ability to travel through viscous environments enables oral spirochaetes to migrate within the gingival crevicular fluid and to penetrate sulcular epithelial linings as well as gingival connective tissue.Chlamydia, Mycoplasma Rickettsiae
chlamydiaeThe chlamydiae are a group of microorganisms related to Gram-negative high lipid))bacteria. However, unlike bacteria, they are unable to grow on inanimate culture media. They are therefore obligatory intracellular parasites.
Their main characteristics include the following
• larger than most viruses and hence visible by light microscopy • both DNA and RNA are present • obligate intracellular parasites with a complex growth cycle • sensitive to tetracycline, erythromycin, sulphonamides.
There are three species in the genus Chlamydia
Chlamydia trachomatis is an agent of many diseases (trachoma) 2. Chlamydia pneumoniae causes acute respiratory tract infection, 3. Chlamydia psittaci primarily causes disease (psittacosis) in birds such as pet parrotsChlamydia Characteristics
Unique growth cycle because they are deficient in independent energy metabolism; therefore they are obligate intracellular parasites Replication involves elementary body (EB) and reticulate body (RB)Life Cycle of Chlamydia
EB infects host cell by inducing energy-requiring active phagocytosisEB organize into large, reticulating initial bodies, which divert the cells’ synthesizing functions to their own needs and begin to multiply by binary fissionOrganisms begin reorganizing into infective EBs.Disrupted host cell dies, releasing new EBsLife Cycle of Chlamydia
Chlamydia pneumoniaeMost recognized species of Chlamydia Important respiratory pathogen (acute respiratory disease, pneumonia, and pharyngitis)
Chlamydia pneumoniae
Common (50% of adults have antibodies) College age students most susceptible Reinfection common Prolonged sore throat and hoarseness, followed by flu-like lower respiratory symptoms Can be followed by pneumonia and bronchitis Third most common respiratory infection
Chlamydia pneumoniae
If cultured, must be in cells (obligate intracellular pathogen) and then visualized with fluorescein-conjugated antibodies Serologic tests are method of choice for detection (Four-fold rise in titer)Chlamydia trachomatis
Most commonly sexually transmitted bacterial pathogen In Adult males Epididymitis and prostatitis Non-gonococcal urethritis (NGU) Adult females Urethritis, follicular cervicitis, endometritis,, salpingitis, Major cause of sterility May be transmitted to newborns during ) (pneumonia)deliveryChlamydia trachomatis
Other sites of infectionTrachoma – infection of the conjunctiva, resulting in scarring and blindness (Mostly in India and Egypt)Mycoplasmas
are the smallest prokaryotes capable of binary fission, grow, albeit slowly, on inanimate media. Mycoplasmas are indeed wall-less bacteria, without the peptidoglycan cell wall but bound by a plasma membrane consisting of lipids and sterols (including cholesterol). Hence, they are highly pleomorphicMycoplasma and Ureaplasma Species
General Characteristics Once thought to be viruses because of size Mycoplasmas are the smallest free-living organism in nature Three human pathogens Mycoplasma pneumoniae - respiratory Mycoplasma hominis - urogenital Ureaplasma urealyticum - urogenitalThe most important species of the genus Mycoplasma is
Mycoplasma pneumoniae, which causes: • a common pneumonia, atypical pneumonia • mucocutaneous eruptions, including the oral mucosa • haemolytic anaemia.Clinical Infections Mycoplasma pneumoniae causes Primary atypical pneumonia
Primary atypical pneumonia takes the form of fever, non- productive cough, severe headache, weakness and tiredness. The acute illness lasts for about 2 weeks, but in a majority, the symptoms last longer.
Mucocutaneous eruptions
skin rashes and ulcerations of both the oral and vaginal mucosa. These appear as maculopapular, vesicular or erythematous eruptions. The skin lesions, which often affect the extremities, have a target or iris appear- ance (target lesions). When the oral ulceration is associated with the skin rash and conjunctivitis, it is called Stevens–Johnson syndromeM. hominis & U. urealyticum
Most often associated with urogenital tract infections May be isolated from asymptomatic individuals Can be transmitted to the fetus at deliveryRX
Antibiotic sensitivity Tetracycline for adults and erythromycin for children
Rickettsiae
Rickettsiae are pleomorphic organisms, smaller than bacteria but resembling them structurally and metabolically, including cell wall formation. They, like Chlamydia and viruses, are obligate intracellular parasites. The best-known human rickettsial disease is typhus, which spreads wildly in condi- tions of malnutrition and poverty.Characteristics of Rickettsiae
• coccobacilli, with a multilayered outer cell wall resembling that of Gram-negative bacteria • obligate intracellular parasites that replicate by binary fission • visible by light microscope when special stains are used (e.g. Giemsa) • able to infect many species, including arthropods, birds and mammals; transmitted to humans via bites of infected arthropods • sensitive to tetracycline and chloramphenicol.