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Bacterial Systemic Infection R elevant to Dentistry. Tuberculosis: Mycobacterium spp. Legionellosis : Legionella spp. Air-borne Bacterial infections. Tuberculosis. Tuberculosis (TB). Is a chronic pulmonary disease. The major causative agent is Mycobacterium tuberculosis ( Mtb ).
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Tuberculosis: Mycobacterium spp. Legionellosis: Legionella spp. Air-borne Bacterial infections
Tuberculosis (TB) • Is a chronic pulmonary disease. • The major causative agent is Mycobacterium tuberculosis (Mtb). • Other Mycobacterium spp. such as M. bovis, are also capable of causing the disease. • TB continues to be a major health burden worldwide in the twenty-first century.
TB Transmission • Transmission of M. tuberculosis occurs through aerosols generated by coughing, sneezing and speaking. • M. tuberculosis can remain airborne within small droplets for several hours and susceptible individuals can still become infected. • It is thought that as few as 1–5 bacilli are required to initiate infection.
Mycobacterium tuberculosis • Slender, beaded, straight or slightly curved rod of about 3µm x 0.3µm, occurs either in pairs or small clumps. • Acid-fast, aerobic, non-motile, non-capsulated and non-sporing • Can survive in the phagosomes and prevent normal phagosome maturation. • Block accumulation of ATPases and GTPases in the phagosomes which interferes with phagosomal acidification.
Life cycle of M. tuberculosis (Mtb) • Is inhaled by aerosols and transmitted to the lungs • Is phagocytized by alveolar macrophages • Eliminated via various mechanisms including apoptosis and autophagy. • If not eradicated, in early stage of infection, then the disease is preserved in latent condition without symptoms of tuberculosis (TB) in 90-95% of individuals.
Progression of TB • 90-95% of cases, wherein the tubercle bacilli are inhaled, a primary infection is established. • This is either cleared by the surge of the cell-mediated immunity or contained inside the granuloma in the form of latent TB. • The progress of TB can be stalled at this stage in some cases by isoniazid preventive therapy.
Pathogenesis of Primary Latent TB • Produces only slight abnormalities, including malaise and mild fever. • Produces a single lesion-Ghon complex-in the pulmonary parenchyma, and the hilar lymph node. • Cell-mediated immunity develops over a period of 3-6 weeks.
Progression of TB Progress to active TB by reactivation of the existing latent infection, with a lifetime risk of 5–10%, exacerbated by immune-compromising factors such as HIV-AIDS, diabetes, indoor air pollution and tobacco smoke.
Progression of TB • Reactivation of TB is shown to occur at the upper and more oxygenated lobe of the lung, which can be cured by compliance with drug therapy. • However, untreated or poorly treated TB might lead to the formation of tuberculous lesions in the lung. • The development of cavities close to airway spaces allows shedding (e.g. coughing) of the bacilli through the airway, a stage of transmission.
Secondary or Cavitary TB • Reactivation of dormant, endogeneous tubercle bacilli in a sensitized patient who has previous contact with the tubercle bacillus. • The lesions are spherical and cavitary. • The symptoms begin with cough with discharge the bacilli-hemoptysis, low grade fever, malaise, fatigue, anorexia, weight loss, night sweats, pain in the chest, and fibrosis of lung.
Miliary TB • The disseminated form of TB • Caused by seeding of the bacilli through lymphatics or blood vessels. • Produce minute, yellow-white lesions in several visceral organs. • Progress to granuloma lesions
Diagnosis of TB • Clinical symptoms • Mantoux skin test • Chest x-ray • Detection of tubercle bacilli in clinical samples
Mantoux skin test(Tuberculin test) • Measure the delayed cell mediated immunity to tubercle bacilli • Using “purified protein derivative (PPD)” from media in which tubercle bacilli have grown • Positive = an area of induration >10 mm in diam. Develops within 48 h after the intradermal injection of the antigen • Can detect after 2-4 wk after infection • Positive in vaccinated with Bacilli Calmette-Guerin (BCG)
Detection of tubercle bacilli • Sample: sputum • collect 3 early morning specimens on three successive days is required. • obtained by having the patient cough deeply, so that a specimen can be obtained from deep inside the lungs • saliva is not acceptable. • Specimens from lung tissue, Gastric Washings, Bronchial Washings, Pleural Fluid, Lymph node tissue, bone marrow, Cerebrospinal fluid.
Detection of tubercle bacilli • Microscopic detection • Acid fast staining • Auramine-Rhodamine fluorescence staining • Culturing • PCR
Mycobacterium spp. • The acid fast bacilli • Have high molecular weight fatty acids called Mycolic acids which are attached to branched chain polysaccharide called arabinogalactan • This mycolic acid-arabionogalactanmoiety resists to decolorization by acid-alcohol.
Auramine fluorescence staining • A sputum smear stained with auramine. • Using fluorescence microscope, observe glowing white, rice-like, bacteria in the smear.
Mycobacterium tuberculosis • They are strict, obligateaerobes. • Doubling time is approx. 15-20 h. • Require > 3 weeks to develop colonies. • Colony appears dry, rough raised irregular, wrinkled,creamy white
Prophylaxis • Immunoprophylaxis - By Intradermal Injections of live attenuated vaccine from M. bovis (developed by Calmette and Guerin in 1921) called BCG-BacilleCalmette Guerin. - In TB endemic countries, such as India, BCG vaccines are administered to babies by intradermal injections immediately after birth or as early as possible after that, but before age of 12 months.
Treatment • Antibiotics • The most effective and had the lowest toxicity: Izoniazidand Rifampin • Multidrug resistant TB • The emergence of multi-drug resistant strains of M. tuberculosis (MDR-TB) is a major problem in the successful treatment and control of TB.
Resistance of M. tuberculosis • Heat Labile : Killed at 60ºC in 15 – 20 minutes. • Cultures are killed by exposure to sunlight for 2 hours . • Cultures remain viable at RT for 6 – 8 months and can stored up to 2 years at -20ºC. • Bacilli in sputum remain alive for 20 to 30 hours, in droplet nuclei are viable for 8 to 10 days. • Bacilli are resistant to • Chemical disinfectants, 5% phenols, 15% Sulphuric acid, 3% nitric acid, 5% Oxalic acid. • But they are very sensitive to formaldehyde and gluteraldehyde, tincture of Iodine in 5 minutes, 80% ethanol in 2 to 10 minutes.
Relevant in Dentistry • Transmission of TB remains possible primarily through patients from high risk areas in the world. • Despite the putative low risk, evidence for the transmission of TB in dental practice is present. • Hospital dental staff may be at increased risk of exposure to TB. • The possibility of M. tuberculosis transmission within dental settings has been subject to risk assessments by the CDC.
Relevant to Dentistry • Dental team-to-dental team and possibly patient-to dental team TB infection was documented. • In the UK a report documented cases of intraoral and pulmonary TB in patients that had been infected by their dental surgeon. All of the patients had tooth extraction performed by the dental surgeon who had active pulmonary TB.
Oral lesions of TB • Rare, secondary to pulmonary TB • Ulcer: multiple, painful, undermined border, granulating floor, usually covered by a gray-yellowish exudate, inflamed and indurate surrounding tissue • Bony involvement of maxilla and mandible may produce tuberculosis osteomyelitis.
Legionellosis • Legionnaires’ disease, a severe-fetal-form of pneumonia in humans • 2 weeks incubation period • Symptoms include fever, chills, loss of appetite, headache, lethargy, dry cough • Aless severe flu-like disease: Pontiac fever • The most common etiological agent (80-90%)is Legionella pneumophila, particularly serogroup 1 (65-70%).
Transmission of Legionella • Legionellais common in many environments, including soil and aquatic systems. • Inhalationof aerosols contaminated with Legionella spp. • Is not transmissible from person to person. • Most people exposed to the bacteria do not ill, only in immuno-compromised host and elderly.
Transmission of Legionella • One of the top three causes of community-acquired pneumonia. • Legionnaires’ disease outbreaks have frequently been associated with contaminated aerosol-producing water systems.
Transmission of Legionella • Legionnaires’ disease is also considered to be an important nosocomial infection, a fetal rate of 20-30%. • Outbreaks of Legionnaires’ disease in hospitals have been predominantly associated with contaminated potable water supplies.
Legionella spp. • Gram-negative bacilli, pleomorphic • Strict aerobe • Non-sporing • Motile by polar flagella • Grow in biofilms, sheltered from the disinfectant.
Legionella spp. • Facultative intracellular pathogens; mammalian host and free-living amoeba • In the natural environment, legionella lives within amoeba such as Acanthamoeba spp., Naegleria spp., Tetrahymenapyriformis, and Vermamoebavermiformis.
Intracellular life cycle of L. pneumophila: 1) coiling phagocytosis 2) Legionella-containing vacuole (LCV) 3) interacts with mitochondria and recruiting ER-derived vesicles 4) A rough ER-like replicative vacuole 5) bacteria undergo several rounds of replication, become flagellated 6) escape the host and start a new cycle.
Pathogenesis • The infective dose of Legionella spp. is thought to be greater than 105 CFU/ml. • Legionella damage lung tissue by producing exotoxins and enzymes, which facilitate coagulative necrosis, congestion, hemorrhage, and abscess formation. • Legionellapneumophilawhich have been proliferated in amoeba are more virulent.
Diagnosis • Culturing • A fourfold increase in antibody titer • Positive legionella urinary antigen test • Detects a part of the Legionella bacteria in urine. • Immunological techniques • PCR
Biofilm growth of legionella Live in amoeba, sheltered from the disinfectant.
Culturing • Culture on buffered charcoal yeast extract (BCYE) agar containing antibiotics (e.g. glycine, vancomycin, polymixin, cyclohexamide, GVPC) to suppress other flora in the sample. • Requires the presence of cysteine and iron to grow • Incubation for up to 10 days • Legionella-like amoebal pathogens (LLAP)-cocultivation with their protozoa
Treatment • Antibiotics; macrolides, fluoroquinolones, tetracyclines, rifampins • No vaccine is currently available
Prevention and Control • Design and maintenance guidelines for controlling the growth of Legionella in cooling towers. • Thermal methods • Temp. <25C, >50C • Hyperchlorination • Chlorine 0.5 ppm • Ultraviolet light
Relevant in Dentistry • A potential risk in the dental clinic where contaminated dental unit waterlines (DUWLs) could act as a source of infection to both dental staff and patients. • DUWLs harbor microbial biofilms that can provide a suitable environment for the multiplication of Legionella spp. within protozoa. • In particular, prevalence rates vary with differing geographic location.
Relevant in Dentistry • Dental staff have higher serum levels of antibodies specific to Legionella spp. than members of the general population. • This is indicative of an increased occupational exposure to Legionella spp. through contaminated aerosols. • The mild form of legionellosis is underdiagnosed and the link between the DUWLs and the disease is underestimated.
Relevant in Dentistry • The recommendations and guidelines from dental associations • Total viable bacteria count in water of DUWLs 100-500 CFU/ml • For legionella spp. <100 CFU/ml • The detection of Legionella in water concentrate the bacteria by centrifugation and/or filtration through 0.2-μm filters before culturing. • Lawsuits against dentists if a patient is infected by Legionella from DUWLs.
Pseudomonas spp. • Opportunistic pathogen • Is associated with many types of infection, including hospital-acquired pneumonia, skin infections, urinary tract infections, burns, eye infections, and blood stream infections. • Pseudomonas spp. may pose an important health hazard, particularly for immune-compromised patients. • is frequently recovered from DUWLs where it can form biofilms in the tubing.
Pseudomonas aeruginosa • Aerobic • Non-fermenter • Monotrichous flagellum • Enterotoxins: exotoxin A • Nosocomial infection