Microbiology of major bacterial infections of lower resp tract.pptx

Microbiology of major bacterial infections of lower respiratory tract BMS 250 Dr. Albert Iarz, ND, RMT Learning Objectives Gram-positive Bacteria Staphylococci (focus: S. aureus) Streptococci (focus: S. pyogenes, S. pneumoniae) Gram-negative Bacteria Haemophilus influenzae Bordetella pertussis & par...

Microbiology of major bacterial infections of lower respiratory tract BMS 250 Dr. Albert Iarz, ND, RMT Learning Objectives Gram-positive Bacteria Staphylococci (focus: S. aureus) Streptococci (focus: S. pyogenes, S. pneumoniae) Gram-negative Bacteria Haemophilus influenzae Bordetella pertussis & parapertussis Klebsiella pneumoniae Pseudomonas aeruginosa Bacteria causing “Atypical Pneumonia” Legionella Mycoplasma pneumoniae Chlamydia trachomatis Learning Objectives Community-acquired pneumonia (CAP) Typical CAP (S. pneumoniae) Atypical CAP (Mycoplasma, Chlamydia, Legionella) Nosocomial pneumonia (gram-negative pathogens) Hospital-acquired pneumonia (HAP) Ventilator-acquired pneumonia (VAP) Pulmonary abscess & Anaerobic infections Tuberculosis Classification of Bacteria Staining: Gram-positive versus Gram-negative Hans Christian Gram developed the staining method using crystal violet dye (1884) - bacteria are classified by the color they turn in the staining method Gram-positive: stain BLUE - the dye is retained by the thick peptidoglycan cell wall Gram-negative: stain RED Gram-negative and gram-positive bacteria stain differently because their cell walls are different They also cause different types of infections, and different types of antibiotics are effective Classification of Bacteria II: Oxygen: Aerobic versus Anaerobic Aerobic – Aerobes: Need oxygen for growth Anaerobic – Anaerobes: Difficulties to grow when oxygen is present A large part of the normal resident flora on mucous membranes: mouth, lower gastrointestinal tract, and vagina. Can cause disease when mucous membranes are disrupted. Anaerobes from outside the body sometimes cause disease when they enter breaks in the skin or are consumed. Classification of Bacteria III: Morphology Spherical (cocci) Cylindric (bacilli) Spiral (spirochetes) Gram-Positive Cocci Two of the most important human pathogens: Staphylococcus aureus and Streptococcus pyogenes Nonmotile and do not form spores They are differentiated by two main criteria: Microscopically: staphylococci appear in grapelike clusters, whereas streptococci are in chains. Biochemically: staphylococci produce catalase (i.e., they degrade hydrogen peroxide), whereas streptococci do not. Staphylococci and Streptococci Both staphylococci and streptococci are gram-positive cocci, but they are differentiated by two main criteria: Microscopically, staphylococci appear in grapelike clusters, whereas streptococci are in chains. Biochemically, staphylococci produce catalase (i.e., they degrade hydrogen peroxide), whereas streptococci do not. Staphylococcus aureus: Microbiologic Properties spherical grampositive cocci arranged in irregular grapelike clusters produce catalase, whereas no streptococci do (catalase degrades H2O2 into O2 and H2O). Catalase is an important virulence factor Citation: Chapter 15 Gram-Positive Cocci, Chin-Hong P, Joyce EA, Karandikar M, Matloubian M, Rubio L, Schwartz BS, Levinson W. Levinson's Review of Medical Microbiology & Immunology, A Guide to Clinical Infectious Diseases, 18th Edition; 2024. Available at: https://login.ccnm.idm.oclc.org/ Accessed: January 20, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved Staphylococcus: Three Species S. aureus S. epidermidis S. saprophyticus S. aureus is distinguished from the others primarily by coagulase product ion Citation: Chapter 15 Gram-Positive Cocci, Chin-Hong P, Joyce EA, Karandikar M, Matloubian M, Rubio L, Schwartz BS, Levinson W. Levinson's Review of Medical Microbiology & Immunology, A Guide to Clinical Infectious Diseases, 18th Edition; 2024. Available at: https://login.ccnm.idm.oclc.org/ Accessed: January 20, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved Staphylococcus aureus: β-lactamase Enzyme that degrades many, but not all, penicillins β-Lactamase–resistant penicillins are used (methicillin & nafcillin) Many strains of S. aureus are resistant to the βlactamase–resistant penicillins aureus methicillin-resistant Staphylococcus MRSA MRSA accounts for more than 50% of S. aureus strains isolated from hospital patients and is also very commonly seen in the community but at a slightly lower frequency. Transmission Humans are the reservoir for staphylococci. The nose is the main site of colonization of S. aureus, and approximately 30% of people are colonized at any one time. People who are chronic carriers of S. aureus in their nose have an increased risk of skin infections caused by S. aureus. The skin, especially of hospital personnel and patients, is also a common site of S. aureus colonization. Hand contact is an important mode of transmission, and handwashing decreases transmission. Pathogenesis of S. aureus: Toxigenic 3 EXOTOXINS Enterotoxin: food poisoning Toxic Shock Syndrome Toxin: toxic shock - in tampon-using menstruating women; in individuals with wound infections; in patients with nasal packing used to stop bleeding from the nose Exfoliatin: causes “scaldedskin” syndrome in young children. Localized production of exfoliatin by S. aureus results in bullous impetigo. Pathogenesis of S. aureus: Toxigenic Pathogenesis of S. aureus: Pyogenic S. aureus causes disease both by producing toxins and by inducing pyogenic (pusproducing) inflammation. Typical lesions: abscess, folliculitis, impetigo may disseminate via the bloodstream Foreign bodies (sutures and intravenous catheters) predisposing factors Pathogenesis of S. aureus: Pyogenic Other forms of disseminated diseases caused by S. aureus: osteomyelitis, arthritis S. Aureus: Pneumonia Hospital-acquired pneumonia S. epidermidis S. saprophyticus Streptococci: Important Properties Spherical grampositive cocci arranged in chains or pairs All streptococci are catalase negative Classification of Streptococci: Groups These are arranged into groups A–U (known as Lancefield groups) based on antigenic differences in C carbohydrate Group A streptococci (S. pyogenes): one of the most important human pathogens. They are the most frequent bacterial cause of pharyngitis and a very common cause of skin infections. The growth of S. pyogenes on agar plates in the laboratory is inhibited by the antibiotic bacitracin - an important diagnostic criterion Classification of Streptococci: Type of Hemolysis α- Hemolytic streptococc i: A green zone around their colonies as a result of incomplete lysis of red blood cells in the agar. β- Hemolytic streptococc i: A clear zone around their colonies because complete lysis of the red cells occurs. βHemolysis is due to the Transmission Most streptococci are part of the normal flora of the human throat, skin, and intestines Produce disease when they gain access to tissues or blood Viridans streptococci and S. pneumoniae are found chiefly in the oropharynx S. pyogenes is found on the skin and in the oropharynx in small numbers S. agalactiae occurs in the vagina and colon The enterococci and anaerobic streptococci are located in the colon. Streptococci of Medical Importance S. pyogenes (group A Streptococcus) The leading bacterial cause of pharyngitis Cellulitis Impetigo, erysipelas, necrotizing fasciitis, scarlet fever, and streptococcal toxic shock syndrome. The inciting factor of two important immunologic diseases: rheumatic fever acute glomerulonephritis S. pyogenes (group A Streptococcus) Three types of diseases: (1) pyogenic diseases such as pharyngitis and cellulitis, Induced locally at the site of the organisms in tissue (2) toxigenic diseases such as scarlet fever and toxic shock syndrome - widespread systemic symptoms in areas of the body where there are no organisms (3) immunologic diseases such as rheumatic fever and acute glomerulonephritis (AGN). Antibody against a component of the organism cross-reacts with normal tissue or forms immune complexes that damage Pathogenesis Group A (Pyogenes) Streptococci S. viridans Part of the normal flora of the human pharynx The most common cause of subacute bacterial endocarditis S. agalactiae S. agalactiae (group B Streptococcus) - the leading cause of neonatal sepsis and meningitis Pathogenesis - Groups B & D, and S. pneumoniae & Viridans Streptococcus pneumoniae Pneumonia, bacteremia, meningitis, and infections of the upper respiratory tract such as otitis media, mastoiditis, and sinusitis. Pneumococci are the most common cause of community-acquired pneumonia Arrows point to typical grampositive diplococci. The clear area around the organism is the capsule. Streptococcus Pneumoniae Pneumococci are spherical gram-positive bacteria of the genus Streptococcus Bacteria grow in chains or pairs The name Streptococcus, from the Greek Streptos = “twisted,” and kokkos = “berry” Citation: 9-12 Pneumonia, Papadakis MA, McPhee SJ, Rabow MW, McQuaid KR, Gandhi M. Current Medical Diagnosis & Treatment 2024; 2024. Available at: https://accessmedicine.mhmedical.com/content.aspx? sectionid=279902610&bookid=3343&Resultclick=2 Accessed: January 16, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved Streptococcus Pneumoniae α-hemolytic group that characteristically produces a greenish color on blood agar because of the reduction of iron in hemoglobin Citation: Chapter 146 Pneumococcal Infections, Loscalzo J, Fauci A, Kasper D, Hauser S, Longo D, Jameson J. Harrison's Principles of Internal Medicine, 21e; 2022. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=263548594&bookid=3095 Accessed: January 16, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved Pneumococcal Cell Surface Within the cytoplasm, cell membrane, and cell wall, many molecules that may play a role in pneumococcal pathogenesis and virulence have been identified key antigens and their roles Citation: Chapter 146 Pneumococcal Infections, Loscalzo J, Fauci A, Kasper D, Hauser S, Longo D, Jameson J. Harrison's Principles of Internal Medicine, 21e; 2022. Available at: https://accessmedicine.mhmedical.com/content.aspx?sectionid=263548594&bookid=3095 Accessed: January 16, 2024 Copyright © 2024 McGraw-Hill Education. All rights reserved S. Pneumoniae: Pathogenesis Polysaccharide capsules (interfere with phagocytosis) C-substance (C-polysaccharide) - reacts with a normal serum protein made by the liver called Creactive protein (CRP) C-reactive protein (CRP): - an “acute-phase” protein that is elevated as much as 1000-fold in acute inflammation - not an antibody (which are γ-globulins) but rather a β-globulin - A nonspecific indicator of inflammation and is elevated in response to the presence of many organisms, not just S. pneumoniae. - Clinically, CRP in human serum is measured in the laboratory by its reaction with the carbohydrate of S. pneumoniae S. Pneumoniae: Pathogenesis Pneumolysin, the hemolysin that causes αhemolysis, may also contribute to pathogenesis. IgA protease that enhances the organism’s ability to colonize the mucosa of the upper respiratory tract by cleaving IgA. Pneumococci multiply in tissues and cause inflammation. When they reach alveoli, there is outpouring of fluid and red and white blood cells, resulting in consolidation of the lung. During recovery, pneumococci are phagocytized, mononuclear cells ingest debris, and the consolidation resolves. Transmission of Pnemococci Humans are the natural hosts for pneumococci (no animal reservoir): 5%–50% of the healthy population (in the oropharynx) Resistance is high in healthy young people, and disease results most often when predisposing factors are present: 1) alcohol or drug intoxication or other cerebral impairment that can depress the cough reflex and increase aspiration of secretions (2) abnormality of the respiratory tract (e.g., viral infections), pooling of mucus, bronchial obstruction, and respiratory tract injury caused by irritants) (3) abnormal circulatory dynamics (e.g., pulmonary congestion and heart failure) (4) splenectomy Gram-Negative Bacteria Gram-negative Bacteria Haemophilus influenzae Bordetella pertussis & parapertussis Klebsiella pneumoniae Pseudomonas aeruginosa Gram-Negative Bacteria Haemophilus Influenzae Normal component of the upper respiratory tract flora Infections caused by Haemophilus Influenzae Pneumonia in immunocompromise d and HIVpositive persons Bordetella pertussis & parapertussis small, encapsulated coccobacilli pertussis (also known as whooping cough), and the latter causes a mild pertussis-like illness an important cause of morbidity and mortality worldwide (2.4 million cases and 160,000 deaths each year) Pertussis vaccines are available and have had significant effects on lowering the incidence of Pseudomonas aeruginosa Localized and systemic illness; virtually any tissue or organ eye (keratitis and endophthalmitis following trauma), ear (external otitis, or swimmer's ear, and invasive and necrotizing otitis externa), Skin; urinary tract; CNS respiratory tract (pneumonia in individuals with chronic lung disease, congestive heart failure, or cystic fibrosis, particularly in patients who have been intubated or are on ventilators for longer than a few days) gastrointestinal (GI) tract (mild diarrheal illness in children to severe, necrotizing enterocolitis in infants and neutropenic cancer patients) Individuals most at risk include those with impaired immune defenses. Klebsiella Pneumoniae large, nonmotile bacilli that produce an abundant capsule necrotizing lobar pneumonia in individuals compromised by alcoholism, diabetes, or chronic obstructive pulmonary disease. K. pneumoniae also causes UTI and bacteremia, particularly in hospitalized patients. Bacteria causing “Atypical Pneumonia” Legionella Mycoplasma pneumoniae Chlamydia trachomatis Mycoplasma Pneumoniae Structural features Chlamydia Legionella Aspiration of water containing the organism or by inhalation of a contaminated aerosol. Legionnaires disease - an atypical, acute lobar pneumonia with multisystem symptoms. It may occur sporadically or in outbreaks (eg, nosocomial outbreaks have Bacterial Pneumonia Community-acquired pneumonia (CAP) Typical CAP (S. pneumoniae) Atypical CAP (Mycoplasma, Chlamydia, Legionella) Pneumonia Centers for Disease Control and Prevention National Healthcare Safety Network Pneumonia Definitions Classification of Pneumonia 1. Community-acquired pneumonia (CAP) 2. Nosocomial pneumonia: 2a) hospital-acquired pneumonia (HAP) 2b) ventilator-associated pneumonia (VAP) These categories are based on differing settings and infectious agents and require different diagnostic and therapeutic intervention. Anaerobic pneumonia and lung abscess can occur in both hospital and community settings. 1. Typical 2. Atypical These categories are based on differing clinical presentation Host Defense Mechanisms: Innate Immunity First line od defense: 1. Intact respiratory epithelium; cough reflex 2. Nonspecific or innate immune factors: Mucus & mucociliary clearens Immunoglobulin A, cytokines Splenic function Complement Neutrophils Macrophages Host Defense Mechanisms: Acquired Immunity Induced following colonization or through exposure to cross-reactive antigens Development of serum IgG antibody specific for the pneumococcal capsular polysaccharide (or other antigens) High Risk in Infants & Agammaglobulinemia In children 38°C) Leukopenia (