Bacterial Lower Respiratory Tract Infection Lecture PDF

Faculty of Medicine Bacterial Lower Respiratory tract Infection Ass.Prof. :Raghda Hussein Date : 13 / 2 /2024  INTENDED LEARNING OBJECTIVES : List the common causative agents of Lower respiratory tract infections. Recognize clinical manifestations of Lower respiratory...

Faculty of Medicine Bacterial Lower Respiratory tract Infection Ass.Prof. :Raghda Hussein Date : 13 / 2 /2024  INTENDED LEARNING OBJECTIVES : List the common causative agents of Lower respiratory tract infections. Recognize clinical manifestations of Lower respiratory tract infections. Outline the laboratory diagnostic approach in different respiratory tract infections. List treatment and specific preventive measures available for infectious diseases of the respiratory tract. LOWER RESPIRATORY TRACT INFECTIONS  Type Infection Most Common Causal Agents Bronchitis -Respiratory viruses: most common primary pathogen. -Secondary bacterial infection: H.influenzae, M.catarrhalis, S. pneumoniae, Bordetella pertussis (acute tracheobronchitis) (Whooping cough) Mycoplasma pneumoniae  BRONCHITIS Clinical manifestations: 1-Cough is the most prominent symptom 2-other symptoms of upper respiratory infection: nasal congestion, sore throat, and a low-grade fever. 3-Physical examination reveals expiratory wheezes  WHOOPING COUGH (PERTUSSIS) Causative agent Bordetella pertussis Characteristics: Gram negative capsulated coccobacilli Transmission: It is a pathogen only for humans; occurs primarily in infants and young children. It is transmitted by droplets produced during the severe coughing episodes. PATHOGENESIS  VIRULENCE FACTORS The organisms attach to the ciliated epithelium of the upper respiratory tract but do not invade the underlying tissue. Decreased cilia activity and subsequent death of the ciliated epithelial cells are important aspects of pathogenesis. 1. Pili: help attachment of the organism to the cilia of the epithelial cells. 1. Pertussis toxin (A-B subunit toxin): causes prolonged stimulation of adenyl cyclase →increase in cAMP→ increased mucus production → severe cough. (Note that pertussis toxin is both an adhesin and a toxin.). 2. Adenylate cyclase toxin : increased mucus production and inhibits leukocyte movement to lymphoid tissues ( lymphocytosis ), inhibits phagocytosis, and killing. 4. Tracheal cytotoxin: kills ciliated epithelial cells. 5. Capsule. 6. Endotoxin.  CLINICAL FINDINGS I.P 7–10 days Whooping cough is an acute tracho bronchitis that begins with catarrhal phase with mild upper respiratory tract symptoms e.g. running nose ,malaise, low grade fever. followed by a severe paroxysmal cough, which lasts from 1 to 4 weeks. The paroxysmal pattern is characterized by fits of many , rapid coughs followed by a high –pitched ‘’ whoop’’ sound as air rushes past the narrowed glottis It is accompanied by production of copious amounts of mucus. Vomiting during or after coughing fits, exhaustion ( very tired) after coughing fits. Treatment: Azithromycin especially during the catarrhal stage. Symptomatic treatment: O2 inhalation, sedatives, bronchodilators. Prevention And Control Acellular pertussis vaccine: containing purified antigens from B. pertussis. (The main immunogen is pertussis toxoid); It is given usually with diphtheria and tetanus toxoids (DTaP vaccine) at 2, 4, 6 month after birth. I.M. Booster doses are given at 1.5 year, and at school age. Chemoprophylaxis: Azithromycin (for 5 days): for contacts.  BACTERIAL & FUNGAL PNEUMONIAS According Clinical presentation: According Source of infection Typical Community-acquired Atypical pneumonia: Hospital acquired pneumonia  ACCORDING CLINICAL PRESENTATION Typical Atypical Sudden onset ,chills, malaise Gradual onset High fever low grade fever, Productive cough. dry non- productive cough, Lobar infiltrate on chest X-ray. headache, sore throat, diffuse lung infiltrates  ACCORDING SOURCE OF INFECTION Community-acquired pneumonia: (hospital acquired) pneumonia The most common cause is Strept It occurs 48 hours or more after admission pneumoniae and respiratory viruses to hospital and wasn’t present during admission. Other common bacterial pathogens include Klebsiella pneumoniae and Haemophilus Common causes: influenzae. Gram-negative bacilli: E. coli, K. Mycoplasma pneumoniae, Legionella species, pneumoniae, P. aeruginosa, and Chlamydia pneumoniae are other Gram-positive cocci especially S. aureus. pathogens reported. (Hospital-acquired pneumonia is mostly caused by antimicrobial resistant organisms) Typical Streptococcus pneumoniae Pneumonia Pseudomonas: Occurs primarily in neutropenic pts, burn pts, chronic granulomatous disease, cystic fibrosis. Source: environmental water or plant sources and respirators ( most common cause of ventilator associated pneumonia)( see skin infections) Klebsiella pneumoniae -Common cause of ventilator-associated pneumonia and is also associated with alcoholism and aspiration. - Lobar pneumonia with a high incidence of abscesses Staphylococcus aureus Causes: - Ventilator or post-influenza pneumonias or pneumonias in people with cystic fibrosis or chronic granulomatous disease. -Lung abscess formation. ( see skin infections) TYPICAL PNEUMONIA STREPTOCOCCUS PNEUMONIAE KLEBSIELLA PNEUMONIAE PSEUDOMONAS S.AUREUS  PNEUMOCOCCAL PNEUMONIA Causative organism: S. pneumoniae are Gram positive cocci, lanceolate in shape, arranged in pairs or short chains, virulent strains are capsulate. Pneumococci are more than 85 types according capsular antigen  TRANSMISSION: 5%–50% of the healthy population harbors virulent organisms in the nasopharynx. Pneumococcal infections is mainly endogenous occurs by aspiration of pneumococci residing in the nasopharynx; Most often when predisposing factors are present e.g. virus infection of respiratory tract , heavy smoking, alcohol intoxication , abnormal circulatory dynamics (e.g., pulmonary congestion and heart failure), or splenectomy. VIRULENCE FACTORS: Polysaccharide capsule: anti-phagocytic. IgA protease: enhances the organism’s ability to colonize the mucosa of the upper respiratory tract. Pneumolysin (hemolysin/cytolysin): damages respiratory epithelium.  DISEASES Otitis media and sinusitis in children most common cause. Typical pneumonia: most common cause Adult meningitis. Symptoms of pneumococcal meningitis, an infection of the lining of the brain and spinal cord, include: Stiff neck Fever Headache Photophobia (eyes being more sensitive to light) Confusion In babies, meningitis may cause poor eating and drinking, low alertness, and vomiting. About 1 in 12 children and 1 in 6 older adults who get pneumococcal meningitis dies of the infection. Those who survive may have long-term problems, such as hearing loss or developmental delay.  COMPLICATIONS OF PNEUMOCOCCAL PNEUMONIA INCLUDE: Empyema (infection around the lungs and in the chest cavity) Pericarditis (inflammation of the outer lining of the heart) Endobronchial obstruction (blockage of the airway that allows air into the lungs), with atelectasis (collapse within the lungs) and abscess (collection of pus) in the lungs TREATMENT: About a third of pneumococcal isolates are now penicillin resistant. Several other drugs, especially macrolides and fluoroquinolones are effective alternative treatments.  PREVENTION Pneumococcal vaccination is recommended for: All children younger than age 2 years All adults age 65 years and older Individuals age 2 to 64 years with certain medical conditions or other risk factors Pneumococcal conjugate vaccine (PCV): (PCV13, 13 of most common serotypes; conjugated to diphtheria toxoid; prevents invasive disease. for all children younger than 5 years old and children 5 through 18 years old with certain medical conditions that increase their risk of pneumococcal disease. Pneumococcal polysaccharide vaccine (PPSV23)): 23 of most common capsular serotypes; recommended for all adults age ≥65 and at-risk individuals.  KLEBSIELLA PNEUMONIAE DISEASES Community-acquired pneumonia (Fried-Lander pneumonia): most often older age; those with chronic lung disease, alcoholism, or diabetes. Health care associated infections (majority of Klebsiella infections) e.g. Ventilator associated pneumonia (VAP) Urinary tract infection. Surgical site infection (SSI). Intravascular device related infections (IVDRIs). Bacteremia and Septicemia: in immunocompromised patients.  LABORATORY DIAGNOSIS OF K. PNEUMONIA Culture of sputum on Blood MacConkey agar; lactose fermenter, further identification by B.R, slide agglutination test Because the antibiotic resistance of these organisms can vary greatly, the choice of drug depends on the results of sensitivity testing. An aminoglycoside (e.g., gentamicin) and third general cephalosporin (e.g., cefotaxime) are used empirically until the results of testing are known.