Microbiology Lesson 20: Other Bacteria & Organisms of Interest PDF

Lesson 20 Other bacteria and other organisms bacteria-like of interest Microbiology PhD. Ana Isabel García Guillén Bachelor in Dentistry CONTENT The genus Mycobacterium M. tuberculosis M. bovis M. leprae Mycobacteria other than tuberculosis (MOTT) The genus Legionella L. pneumophila Other organis...

Lesson 20 Other bacteria and other organisms bacteria-like of interest Microbiology PhD. Ana Isabel García Guillén Bachelor in Dentistry CONTENT The genus Mycobacterium M. tuberculosis M. bovis M. leprae Mycobacteria other than tuberculosis (MOTT) The genus Legionella L. pneumophila Other organisms Chlamydiae Rickettsiae Rickettsia Coxiella Mycoplasmas Mycoplasma pneumoniae Oral Mycoplasmas The genus Mycobacterium Generalities • Nearly 2 billion people, 1/3 world’s population (according to WHO) • Widespread both in the environment and in animals • Aerobic, acid-fast bacilli • Not stained by Gram because of the high lipid component of the cell wall (mycolic acid) • Ziehl–Neelsen stain Mycobacterium cells 3 M. tuberculosis Habitat and transmission • In infected humans, mainly in the lungs • In the body, primarily in reticuloendothelial system • Transmission by coughing (droplet spread) Mycobacterium cells • Slender, beaded bacilli; non-sporing 4 M. tuberculosis Pathogenicity • • • • • Tuberculosis Chronic, granulomatous, slowly progressive infection, usually of the lungs Eventually, many other organs and tissues Pandemic disease Common in developing world and immunosuppressed patients (15-20% prevalence) • Oral cavity is secondary affected 5 M. tuberculosis Antibiotic sensitivity and control • Long-term therapy (6-9 months) • Drug resistance is growing The most common treatment for active TB • Combination therapy should be given is isoniazid INH in combination with three other • Multidrug-resistant tuberculosis (MDR-TB) : drugs—rifampin (rifampicin), pyrazinamide and ethambutol. • Prevention: • • • Bacille Calmette-Guérin (BCG) vaccination containing live attenuated organisms, in childhood Pasteurization of milk General improvement of living standards 6 M. bovis Generalities • Cattle • Transmission ingesting contaminated milk • Eradication of the disease in cattle in West • Childhood disease scrofuloderma, enlarged, caseous cervical lymph nodes Mycobacterium bovis Scrofuloderma 7 M. leprae Generalities and Pathogenicity • Humans are the only known hosts • Transmission by prolonged direct contact • Slow, progressive, chronic disease that mainly affects the skin and the nerves • Predominantly in the cooler parts of the body Mycobacterium leprae 8 M. leprae Pathogenicity A. Lepromatous leprosy Cell-mediated immune response is depressed or absent Large number of rods in the lesions and in blood It affects mainly the mucosa, especially the nose facies leonina 10 M. leprae Pathogenicity B. Tuberculoid leprosy Intense cell-mediated immune response Involves the nerves (anaesthesia and paraesthesia) Damage to extremities with resultant loss of fingers and toes Oral lesion involving the tongue in tuberculoid leprosy. 11 Mycobacteria other than tuberculosis (MOTT) Generalities • Collective name given to a group of mycobacteria of low human pathogenicity • M. avium, M. intracellulare, M. kansasii, M. fortuitum • Isolated from soil, water, birds and other animals • Pathogenicity: Pulmonary infections in compromised patients • M. marinum: can produce skin ulcers, related to the keeping of tropical fishesaquariums! 12 The genus Legionella L. pneumophila • Ubiquitous in soil and water (air-conditioning units, domestic and hospital water supplies, and sometimes in dental unit water systems) • Transmission by contaminated aerosols • Gram-negative slender rods 13 L. pneumophila Pathogenicity • Portal of entry: respiratory tract • Pontiac Fever: an influenza-like illness • “Legionnaires” disease: severe form of pneumonia • Older men who smoke and drink alcohol in excess are typically affected • Risk factors: cancer and immunosuppression • Concern on legionella in stagnant dental unit water lines (lack of evidences) • Protective measures: chlorine concentration and temperature of hospital water supplies 14 Chlamydiae, Rickettsiae and Mycoplasmas Generalities Miscellaneous group of organisms Properties common to both bacteria and viruses Divergent human diseases 15 Chlamydiae Generalities • • • • • • • • Related to Gram-negative bacteria Unable to grow on inanimate culture media Obligatory intracellular parasites Larger than most viruses (visible by light microscopy) Both DNA and RNA are present Complex growth cycle Sensitive to tetracycline, erythromycin, sulphonamides Main species: C. trachomatis, many diseases C. pneumoniae, acute respiratory tract infection C. psittaci, psittacosis, atypical pneumonia 16 C. trachomatis Pathogenicity Ocular infections Neonatal blenorrhoea, keratoconjunctivitis Major cause of blindness in the developing world Genital infections Non-specific urethritis The most common sexually transmitted disease in the UK Pneumonia Neonatal pneumonia 17 Rickettsiae Generalities • • • • • • • • Coccobacilli Smaller than bacteria, Gram negative cell wall formation Obligate intracellular parasites Replicate by binary fission Visible by light microscope (e.g., Giemsa) Infect arthropods, birds and mammals Transmitted via bites Two main genae: Rickettsia and Coxiella 18 Rickettsiae Rickettsia Typhus Acute febrile illness Maculopapular rash Transmitted by the rat flea Mortality is high as a result of haemorrhagic complications Spotted fevers Rocky Mountain spotted fever Other tick-borne fevers 19 Rickettsiae Coxiella • C. burnetii • Organism closely resembling rickettsiae • Q fever, a typhus-like illness • Transmission: aerosols from products of the delivery of infected animals or contaminated milk • • • • ’Non-bacterial’ or atypical pneumonia Proliferate in the respiratory tract and then disseminate to other organs Lesions in brain Infective endocarditis FIG. (A) TEM image showing a typical vacuole in J774A.1 cells infected with C. burnetii at 2 h postinfection. (B) J774A.1 cells infected with C. burnetii, in the same experiment as panel A, at 6 h postinfection. Bar, 100 nm. 20 Mycoplasmas Generalities • Smallest prokaryotes capable of binary fission • Slow growth on inanimate media • No cell wall • Tri-layered plasma membrane consisting of lipids and sterols • Highly pleomorphic A scanning electron micrograph (SEM) of Mycoplasma pneumoniae cells, grown on a glass coverslip, with fixation organelles indicated by the black arrows. 21 Mycoplasmas M. pneumoniae Primary atypical pneumonia Fever, non-productive cough, severe headache, weakness and tiredness The acute illness lasts for about 2 weeks, but symptoms last longer 22 Mycoplasmas M. pneumoniae Mucocutaneous eruptions • Skin rashes and ulcerations • Oral and vaginal mucosa • Maculopapular, vesicular or erythematous eruptions • Skin lesions on extremities (target lesions). • In the oral mucosa, erythematous • Labial lesions • When the oral ulceration is associated with the skin rash and conjunctivitis, it is called Stevens–Johnson syndrome. 23 Mycoplasmas Oral Mycoplasmas Mucocutaneous eruptions Isolated from mouth (6% to 32%) M. buccale, saliva, oral mucosa and dental plaque M. orale and M. salivarium Salivary glands Role in salivary gland hypofunction 24 REFERENCIAS BIBLIOGRÁFICAS Kumar , S. (2016). Essentials of Microbiology. Jaypee Brothers Medical Publishers (P) Ltd. Samaranayake, L. (2012)Essential Microbiology for dentistry .Fourth Edition. Elsevier Ltd. 25 Ana Isabel García Guillén [email protected] UCAM Universidad Católica de Murcia © UCAM © UCAM