Microbiology: Microbial Diseases of the Respiratory System PDF

Microbiology an Introduction Thirteenth Edition, Global Edition Chapter 24 Microbial Diseases of the Respiratory System Copyright © 2021 Pear...

Microbiology an Introduction Thirteenth Edition, Global Edition Chapter 24 Microbial Diseases of the Respiratory System Copyright © 2021 Pearson Education Ltd. All Rights Reserved Normal Microbiota of the Respiratory System (2 of 2) Normal microbiota suppress pathogens by competing for nutrients and producing inhibitory substances. Lower respiratory system is nearly sterile Copyright © 2021 Pearson Education Ltd. All Rights Reserved Microbial Diseases of the Upper Respiratory System Pharyngitis – Sore throat Laryngitis Tonsillitis Sinusitis – Usually self-limiting Epiglottitis – Most life-threatening disease of the upper respiratory system Copyright © 2021 Pearson Education Ltd. All Rights Reserved Bacterial Diseases of the Upper Respiratory System (2 of 2) Streptococcal pharyngitis (strep throat) – Caused by group A streptococci (GAS)  Streptococcus pyogenes – Resistant phagocytosis – Streptokinases lyse clots – Streptolysins are cytotoxic – Local inflammation, fever, tonsillitis, enlarged lymph nodes – Diagnosis by rapid antigen detection tests Scarlet fever – Erythrogenic toxin produced by lysogenized S. pyogenes Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.3 Streptococcal Pharyngitis Copyright © 2021 Pearson Education Ltd. All Rights Reserved Diphtheria Caused by Corynebacterium diphtheriae – Gram-positive rod; pleomorphic Forms a tough grayish membrane in the throat – Fibrin and dead tissue – Blocks passage of air to the lungs Exotoxin produced by lysogenized bacteria – Circulates in the blood; damages the heart and kidneys Cutaneous diphtheria – Transmission through direct contact and Forms skin ulcer Prevented by DTaP vaccine (Diphtheria and tetanus toxoids and acellular pertussis) – Diphtheria toxoid Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.4 Corynebacterium Diphtheriae, the Cause of Diphtheria Clubbed cells Palisade arrangement Copyright © 2021 Pearson Education Ltd. All Rights Reserved Otitis Media Infection of the middle ear – Formation of pus puts pressure on the eardrum Causes – Streptococcus pneumoniae – Nonencapsulated Haemophilus influenzae – Moraxella catarrhalis – S. pyogenes – respiratory syncytial viruses Common in childhood due to smaller auditory tube Treated with broad-spectrum penicillins Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.5 Acute Otitis Media, with Bulging Eardrum Bulging eardrum Copyright © 2021 Pearson Education Ltd. All Rights Reserved Viral Disease of the Upper Respiratory System The Common Cold Over 200 different viruses – Rhinoviruses (30–50%)  Thrive in temperatures lower than body temperature – Coronaviruses (10–15%) – Enterovirus D68 (EV-D68) Sneezing, nasal secretion, congestion – Can lead to laryngitis and otitis media – Not accompanied by fever Antibiotics are of no use. – Relief via cough suppressants and antihistamines Copyright © 2021 Pearson Education Ltd. All Rights Reserved Microbial Diseases of the Lower Respiratory System Caused by many of the same bacteria and viruses as the upper respiratory system – Bronchitis – Bronchiolitis – Pneumonia  Pulmonary alveoli are involved Copyright © 2021 Pearson Education Ltd. All Rights Reserved Bacterial Diseases of the Lower Respiratory System Pertussis (Whooping Cough) (1 of 2) Caused by Bordetella pertussis – Gram-negative coccobacillus Produces a capsule – Allows attachment to ciliated cells in the trachea  Destroys ciliated cells and shuts down the ciliary escalator Tracheal cytotoxin of cell wall damages ciliated cells. Pertussis toxin enters the bloodstream. Copyright © 2021 Pearson Education Ltd. All Rights Reserved  B. pertussis Cilium Figure 24.6 Ciliated Cells of the Respiratory System Infected with Bordetella Pertussis Copyright © 2021 Pearson Education Ltd. All Rights Reserved Pertussis (Whooping Cough) (2 of 2) Stage 1: catarrhal stage, like the common cold Stage 2: paroxysmal stage, violent coughing, gasping for air Stage 3: convalescence stage, may last for months Prevented by DTaP vaccine Treated with antibiotics (e.g. erythromycin or other macrolides) Copyright © 2021 Pearson Education Ltd. All Rights Reserved Tuberculosis (1 of 2) Caused by Mycobacterium tuberculosis – Acid-fast rod; obligate aerobe – 20-hour generation time – Lipids in the cell wall make it resistant to drying and antimicrobials. Other causes – Mycobacterium bovis  Bovine tuberculosis; < 1% of U.S. cases – Mycobacterium avium-intracellulare complex  Infects people with late-stage HIV infection Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.7 Mycobacterium Tuberculosis Corded growth Copyright © 2021 Pearson Education Ltd. All Rights Reserved Pathogenesis of Tuberculosis Inhaled organisms are phagocytized by alveolar macrophages. Mycolic acids in the cell wall stimulate an inflammatory response. Organisms are isolated in the walled-off tubercle. Tubercles heal and become calcified (Ghon's complexes) – Latent TB (tubercle bacilli remain dormant). Tubercle breaks down, releasing bacteria into the lungs and cardiovascular and lymphatic systems – Miliary tuberculosis: disseminated infection Copyright © 2021 Pearson Education Ltd. All Rights Reserved Diagnosis of Tuberculosis Tuberculin skin test – Positive reaction means a current or previous infection. – T cells react with purified protein derivative from the TB bacterium.  Delayed hypersensitivity induration Followed by an X-ray or CT exam, acid-fast staining of sputum, and culturing of bacteria Rapid blood test for IFN-γ and PCR – Higher specificity and less cross-reactivity Blood tests measure release of IFN-γ from white blood cells after exposure to mycobacterial antigen in a test tube. They are the preferred tests for a person who has received BCG vaccinations. Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.9 A Positive Tuberculin Skin Test on an Arm (≥ 15 mm) Copyright © 2021 Pearson Education Ltd. All Rights Reserved Treatment of Tuberculosis Minimum of 6 months of drug therapy due to slow growth and dormancy First-line drugs: isoniazid, rifampin, ethambutol, pyrazinamide Second-line drugs: aminoglycosides, fluoroquinolones, streptomycin, para-aminoslicyclic acid (PAS) Multi-drug-resistant (MDR) strains: resistant to first- line drugs Extensively drug-resistant (XDR) strains: resistant to second-line drugs Copyright © 2021 Pearson Education Ltd. All Rights Reserved Tuberculosis (2 of 2) 10 million develop TB annually; 2 million die ⅓ of the world's population has latent TB. Leading cause of death for those with HIV BCG vaccine: live culture of avirulent M. bovis – Not widely used in the United States due to questionable effectiveness BCG:Bacillus Calmette-Guérin Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.10a Distribution of Tuberculosis Copyright © 2021 Pearson Education Ltd. All Rights Reserved Bacterial Pneumonias Typical pneumonia – Caused by S. pneumoniae Atypical pneumonia – Caused by other microorganisms Lobar pneumonia – Infects the lobes of the lungs Bronchopneumonia – Infects the alveoli adjacent to the bronchi Pleurisy – Pleural membranes inflamed Copyright © 2021 Pearson Education Ltd. All Rights Reserved Pneumococcal Pneumonia Caused by S. pneumoniae – Gram-positive; encapsulated diplococci – 90 serotypes Infected alveoli of the lung fill with fluids and RBCs; interferes with oxygen uptake Diagnosis: optochin-inhibition test, bile solubility test, or presence of capsular antigen in urine Treated with macrolides Prevented with conjugated pneumococcal vaccine Copyright © 2021 Pearson Education Ltd. All Rights Reserved  Capsules Figure 24.11 Streptococcus Pneumoniae, the Cause of Pneumococcal Pneumonia Copyright © 2021 Pearson Education Ltd. All Rights Reserved Haemophilus Influenzae Pneumonia Gram-negative coccobacillus Symptoms resemble those of pneumococcal pneumonia Risk group: Children under 5 and adults over 65 – The Hib vaccine reduced the incidence in children by 99% Diagnosis: isolation on special media for nutritional requirements (X and V factors) Treated with antibiotics (e.g. cephalosporins) Copyright © 2021 Pearson Education Ltd. All Rights Reserved Mycoplasmal Pneumonia Also called primary atypical pneumonia or walking pneumonia Caused by Mycoplasma pneumoniae – No cell wall Mild but persistent respiratory symptoms; low fever, cough, headache – Common in children and young adults “Fried-egg” appearance on media Diagnosis: PCR Treated with antibiotics (e.g. tetracyclines) Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.12 Colonies of Mycoplasma Pneumoniae, the Cause of Mycoplasmal Pneumonia Copyright © 2021 Pearson Education Ltd. All Rights Reserved  Legionellosis Also called Legionnaires’ disease Caused by Legionella pneumophila – Aerobic, gram-negative rod – Grows in water and air conditioning, biofilms, and waterborne amebae Transmitted by inhaling aerosols; not transmitted person to person Symptoms: high fever and cough – Similar to symptoms of Pontiac fever Treated with antibiotics (e.g.azithromycin and macrolides) Pontiac fever is a mild flu-like illness caused by legionella bacteria. Symptoms can include fever, headaches and muscle aches but, unlike Legionnaires' disease, Pontiac fever does not include pneumonia. Copyright © 2021 Pearson Education Ltd. All Rights Reserved Psittacosis (Ornithosis) Caused by Chlamydophila psittaci – Gram-negative intracellular bacterium Transmitted to humans by elementary bodies from bird droppings transmitted through air Fever, headache, chills, disorientation Diagnosis: growth of bacteria in eggs, cell culture or PCR Treated with antibiotics (e.g.tetracyclines) Copyright © 2021 Pearson Education Ltd. All Rights Reserved Chlamydial Pneumonia Caused by Chlamydophila pneumoniae Transmitted person to person Mild respiratory illness common in young people; resembles mycoplasmal pneumonia Possible association with artherosclerosis Diagnosis: PCR Treated with antibiotics (e.g. azithromycin) Copyright © 2021 Pearson Education Ltd. All Rights Reserved Q Fever Caused by Coxiella burnetii – Obligately parasitic, intracellular gammaproteobacteria Acute Q fever – High fever, muscle aches, headache, coughing Chronic Q fever – Endocarditis (may occur years after infection) Transmitted to farm animals from tick bites – Transmitted to humans from the inhalation of aerosols from animals and unpasteurized milk Treated with antibiotics (e.g. doxycycline and chloroquine for chronic infections) Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.13 Coxiella Burnetii, the Cause of Q Fever Copyright © 2021 Pearson Education Ltd. All Rights Reserved Viral Diseases of the Lower Respiratory System Viral Pneumonia Viral pneumonia occurs as a complication of influenza, measles, or chickenpox Few labs are equipped to test clinical samples properly for viruses SARS-associated coronavirus (SARS) – Emerged in Asia in 2003 Middle East respiratory syndrome coronavirus (MERS-CoV) – Reported in Saudi Arabia in 2012 Copyright © 2021 Pearson Education Ltd. All Rights Reserved Respiratory Syncytial Virus (RSV) Most common viral respiratory disease in infants and life-threatening pneumonia in older adults – Almost all children are infected by age 2 – 14,000 deaths annually, mostly in older adults Causes cell fusion (syncytium) in cell culture Coughing and wheezing for more than a week Diagnosis: serological test for viruses and antibodies Treated with palivizumab Copyright © 2021 Pearson Education Ltd. All Rights Reserved Influenza (Flu) (1 of 3) Influenzavirus – Contains eight RNA segments and an outer lipid bilayer Chills, fever, headache, and muscle aches – No intestinal symptoms – 3,000 to 50,000 deaths in the United States annually Avian, swine, and mammalian strains – Swine serve as “mixing vessels” for new strains Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.14 Detailed Structure of the Influenza Virus 2 of 8 RNA segments in NA spike genome Capsid layer HA spike Envelope Copyright © 2021 Pearson Education Ltd. All Rights Reserved Influenza (Flu) (2 of 3) Hemagglutinin (HA) spikes – Recognize and attach to host cells Neuraminidase (NA) spikes – Help the virus separate from the infected cell Antigenic drift – Minor antigenic changes in HA and NA – Allow the virus to elude some host immunity Antigenic shifts – Changes great enough to evade most immunity – Lead to pandemics – Involve the reassortment of the eight RNA segments Copyright © 2021 Pearson Education Ltd. All Rights Reserved Influenza (Flu) (3 of 3) 1% mortality; usually the very young and very old Multivalent vaccine for the most important strains – Composition of the vaccine determined annually by the identification of circulating viruses  Labor-intensive to produce  Does not provide long-term immunity Difficult to diagnose from clinical symptoms Treated with zanamivir (Relenza) and oseltamivir (Tamiflu) – Inhibits neuraminidase A multivalent or polyvalent vaccine is designed to immunizeCopyright ©more against two or 2021 Pearson strains Education of the same Ltd. All microorganism, or Rights Reserved against two or more microorganisms. Fungal Diseases of the Lower Respiratory System Histoplasmosis Caused by Histoplasma capsulatum – Dimorphic fungus – Yeast-form grows intracellularly in macrophages Forms lung lesions; 0.1% of cases become a severe, generalized disease Acquired from airborne conidia in areas with bird or bat droppings – Limited geographical range in the United States Treated with itraconazole Copyright © 2021 Pearson Education Ltd. All Rights Reserved Figure 24.15 Histoplasma Capsulatum, a Dimorphic Fungus That Causes Histoplasmosis Microconidia Macroconidia The macroconidia of Histoplasma capsulatum are especially useful for diagnostic purposes. Microconidia bud off from hyphae and are the infectious form. At 37°Cin tissues, the organism converts to a yeast phase composed of oval, budding yeasts. Copyright © 2021 Pearson Education Ltd. All Rights Reserved Coccidioidomycosis Also known as Valley fever or San Joaquin fever Caused by Coccidioides immitis – Dimorphic fungus Form a spherule filled with endospores in tissues Most infections are not apparent; fever, coughing, weight loss – < 1% of cases resemble tuberculosis Treated with fluconazole or itraconazole Copyright © 2021 Pearson Education Ltd. All Rights Reserved Blastomycosis (North American Blastomycosis) Caused by Blastomyces dermatitidis – Dimorphic fungus – Grows in soil Symptoms resemble bacterial pneumonia; cutaneous abscesses; extensive tissue damage Reported ~100 cases annually Treated with itraconazole and amphotericin B Copyright © 2021 Pearson Education Ltd. All Rights Reserved Other Fungi Involved in Respiratory Disease Aspergillus fumigatus – Causes aspergillosis – Airborne conidia; grows in compost piles Rhizopus and Mucor – Mold spores Predisposing factors: – Immunocompromised state – Cancer – Diabetes Copyright © 2021 Pearson Education Ltd. 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