Microbial Infections of the Respiratory System PDF

MICROBIAL INFECTIONS OF THE RESPIRATORY SYSTEM Presented by: Christine Marie S. Terrado, RPh Objectives: Illustrate the basic anatomical structure of the respiratory system. Determine the etiological agents affecting the respiratory system. Explain the laboratory diagnose...

MICROBIAL INFECTIONS OF THE RESPIRATORY SYSTEM Presented by: Christine Marie S. Terrado, RPh Objectives: Illustrate the basic anatomical structure of the respiratory system. Determine the etiological agents affecting the respiratory system. Explain the laboratory diagnoses, drug of choice and prevention for the specific diseases. Anatomy of the Respiratory System The respiratory system (also respiratory apparatus, ventilatory system) is a biological system, consisting of specific organs and structures used for gas exchange in human. Organs of Respiratory System: Nose and nasal cavity Pharynx Larynx Trachea Two bronchi Bronchioles Two Lungs Infections of the Respiratory System: Upper Respiratory Infections: Common Cold, Sinusitis, Pharyngitis, Epiglottitis Lower Respiratory Infections: Bronchitis, Bronchiolitis, Pneumonia, Tuberculosis Upper Respiratory Infection – Common Cold Etiology of Common Cold Rhinoviruses Coronaviruses Parainfluenza viruses Respiratory syncytial virus Adenoviruses Influenza viruses Rhinoviruses Rhinoviruses are the common cold viruses. They are the most commonly recovered agents from people with mild upper respiratory illnesses. They are usually isolated from nasal secretions but may also be found in throat and oral secretions. Coronaviruses Coronaviruses are large, enveloped RNA viruses. A novel coronavirus was identified as the cause of a worldwide outbreak of a severe acute respiratory syndrome (SARS) in 2003. Its envelope contains large, widely spaced, club- or petal-shaped spikes It has a helical nucleopcapsid Parainfluenza Virus They are major pathogens of severe respiratory tract disease in infants and young children. Reinfections with parainfluenza viruses are common. Respiratory Syncytial Virus It lacks both Neuraminidase Activity and Hemagglutinin Activity It contains F protein that causes infected cells to fuse together into multinucleated giant cells (syncytial cells). Adenoviruses Adenoviruses are 70–90 nm in diameter and display icosahedral symmetry, with capsids composed of 252 capsomeres. There is no envelope. Influenza Viruses It belongs to family Orthomyxoviridae Types of Influenza Virus Type A – infects humans, other mammals like swine and birds Type B – isolated only from humans Type C – isolated only from humans Global Pandemics: The new HA and NA antigens are given number subscripts to differentiate them. H2 – pandemic of 1989 H3 – pandemic of 1900 H1N1 – a swine flu virus transferred its HA to a human flu virus; pandemic of 1918 H5N1 – in 1997; a new strain of avian influenza (transferred from infected poultry to humans in Hong Kong. Clinical Manifestation of Common Cold After an incubation period of 48–72 hours, classic symptoms of nasal discharge and obstruction, sneezing, sore throat and cough occur in both adults and children. Myalgia and headache may also be present. Fever is rare. The duration of symptoms and of viral shedding varies with the pathogen and the age of the patient. Complications are usually rare, but sinusitis and otitis media may follow. Laboratory Diagnosis of Common Cold Examination of nasal secretions. Unlike allergic rhinitis, eosinophils are absent in nasal secretions. Prevention and Treatment of Common Cold Decongestants, antipyretics, fluids and bed rest usually suffice. Restriction of activities to avoid infecting others, along with good hand washing, are the best measures to prevent spread of the disease. No vaccine is commercially available for cold prophylaxis. Upper Respiratory Infection - Sinusitis Sinusitis Sinusitis is an acute inflammatory condition of one or more of the paranasal sinuses. Etiology of Sinusitis Often follows a common cold which is usually of viral etiology. Common bacterial agents responsible for acute sinusitis are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Streptococcus pneumoniae It is Gram positive. Under the microscope, they appear as lancet-shaped gram positive diplococci. The major virulence factor of pneumococcus is its polysaccharide capsule. Optochin sensitivity test can be done to identify Streptococcus pneumoniae Haemophilus influenza It is a Gram negative rod It is blood loving. It often attacks the lungs of persons debilitated by viral influenza infection. It has polysaccharide capsule that confers virulence. Moraxella catarrhalis It is nonmotile, Gram-negative, aerobic, oxidase- positive diplococcus Clinical Manifestation of Sinusitis The maxillary and ethmoid sinuses are most commonly involved in sinusitis. The frontal sinuses are less often involved and the sphenoid sinuses are rarely affected. Pain, sensation of pressure and tenderness over the affected sinus are present. Malaise and low grade fever may also occur. Laboratory Diagnosis of Sinusitis Sinus x-rays may be required. An antral puncture to obtain sinusal specimens for bacterial culture is needed to establish a specific microbiologic diagnosis. Prevention and Treatment of Sinusitis Symptomatic treatment with analgesics and moist heat over the affected sinus pain and a decongestant to promote sinus drainage may suffice. Antimicrobial therapy - beta-lactamase resistant antibiotic such as amoxicillin-clavulanate or cephalosporin may be used For chronic sinusitis, when conservative treatment does not lead to a cure, irrigation of the affected sinus may be necessary. Upper Respiratory Infection - Pharyngitis Pharyngitis Pharyngitis is an inflammation of the pharynx involving lymphoid tissues of the posterior pharynx and lateral pharyngeal bands. Etiology of Pharyngitis Bacteria - Group A beta-hemolytic streptococcus or Streptococcus pyogenes, Corynebacterium diphtheriae, Chlamydia pneumoniae (TWAR agent), Mycoplasma pneumoniae Fungi - Candida albicans Streptococcus pyogenes Possess Lancefield group antigen A Beta hemolytic on BAP M protein (major virulence factor for group A streptococcus) It causes Streptococcal pharyngitis or “Strep throat” with red swollen tonsils and pharynx, purulent exudate on the tonsils, high temperature and swollen lymph nodes. Corynebcaterium diphtheriae They possess irregular swellings at one end that give them the “club-shaped” appearance. Irregularly distributed within the rod (often near the poles) are granules staining deeply with aniline dyes (metachromatic granules) that give the rod a beaded appearance. Corynebacterium diphtheriae It produces diphtheria toxin It forms a grayish “pseudomembrane” commonly over the tonsils, pharynx, or larynx. Any attempt to remove the pseudomembrane exposes and tears the capillaries and thus results in bleeding. Chlamydia pneumoniae (TWAR agent) TWAR is an acronym for its original isolation in Taiwan and Acute Respiratory. Outbreaks of Chlamydia pneumoniae (TWAR agent) causing pharyngitis or pneumonitis have occurred in military recruits. Mycoplasma pneumoniae Infected patients will have a gradual onset of fever, sore throat, malaise and a persistent dry hacking cough. It causes what we usually refer to as walking pneumonia, because clinically these patients do not feel very sick. Mycoplasma pneumoniae can be identified in the laboratory through the cold agglutinins test and sputum culture. Mycoplasma pneumoniae Cold agglutinins Antibodies to these M. pneumoniae antigens cross react with human red blood cell antigens and agglutinate the rbc at 4 degrees Celsius. Mycoplasma pneumoniae Sputum culture It can be grown on artificial media. The artificial media should be rich in cholesterol and contain nucleic acids (purines and pyrimidines). After 2-3 weeks, a tiny-dome shaped colony of M. plasma will assume a “fried-egg” appearance. Candida albicans It causes oral thrush Patches of creamy white exudate with a reddish base cover the mucous membranes of the mouth. Clinical Manifestations of Pharyngitis Red, sore, or “scratchy” throat Inflammatory exudate or membranes may cover the tonsils and tonsillar pillars Vesicles or ulcers may also be seen on the pharyngeal walls Depending on the pathogen, fever and systemic manifestations such as malaise, myalgia, or headache may be present Anterior cervical lymphadenopathy is common in bacterial pharyngitis and difficulty in swallowing may be present. Laboratory Diagnosis of Pharyngitis The various forms of pharyngitis cannot be distinguished on clinical grounds. Routine throat cultures for bacteria are inoculated onto sheep blood and chocolate agar plates. Thayer-Martin medium is used if N gonorrhoeae is suspected. Serologic studies may be used to confirm the diagnosis of pharyngitis due to mycoplasmal or chlamydial pathogens. Prevention and Treatment of Pharyngitis Penicillin G is the therapy of choice for streptococcal pharyngitis Mycoplasma and chlamydial infections respond to erythromycin, tetracyclines and the new macrolides Upper Respiratory Infection - Epiglottitis Epiglottitis Inflammation of the epiglottis Etiology of Epiglottitis Haemophilus influenzae type b is the most common cause of epiglottitis, particularly in children age 2 to 5 years. Because they lack antibodies to the capsule. Epiglottitis is less common in adults. Clinical Manifestation of Epiglottitis Begins with the acute onset of fever, sore throat, hoarseness, drooling, dysphagia and progresses within a few hours to severe respiratory distress and prostration. The clinical course can be fulminant and fatal. The pharynx may be inflamed, but the diagnostic finding is a “cherry-red” epiglottis. Laboratory Diagnosis of Epiglottitis Blood culture should be performed Prevention and Treatment of Epiglottitis All children with this diagnosis should be observed carefully and be intubated to maintain an open airway as soon as the first sign of respiratory distress is detected. Cefotaxime or Ceftriaxone (for serious infections) Ampicillin or Amoxicillin (less serious infections) Hib capsule vaccine has dramatically reduced the incidence of H. influenza infection Immunizing women in the eighth month of pregnancy results in an increases antibody secretion in milk (passive immunization). Lower Respiratory Infection – Bronchitis and Bronchiolitis Etiology of Bronchitis and Bronchiolitis Bronchitis and bronchiolitis involve inflammation of the bronchial tree. Bronchitis is usually preceded by an upper respiratory tract infection or forms part of a clinical syndrome in diseases such as influenza, rubeolla, rubella, pertussis, scarlet fever and typhoid fever. Etiology of Bronchitis and Bronchiolitis Chronic bronchitis with a persistent cough and sputum production appears to be caused by a combination of environmental factors, such as smoking, and bacterial infection with pathogens such as H. influenzae and S. pneumoniae Bronchiolitis is a viral respiratory disease of infants and is caused primarily by respiratory syncytial virus and other viruses including parainfluenza viruses, influenza viruses and adenoviruses Clinical Manifestation of Bronchitis and Bronchiolitis Fever is common Chronic bronchitis - incessant cough and production of large amounts of sputum, particularly in the morning Chronic bronchiolitis - deepening cough, increased respiratory rate, and restlessness follow. Retractions of the chest wall, nasal flaring, and grunting are prominent findings. Wheezing or an actual lack of breath sounds may be noted. Respiratory failure and death may result. Laboratory Diagnosis of Bronchitis and Bronchiolitis Sputum culture for bacteria Serologic tests for virus Prevention and Treatment of Bronchitis and Bronchiolitis Respiratory syncytial virus infections in infants may be treated with ribavirin Amantadine and rimantadine are available for chemoprophylaxis or treatment of influenza type A viruses Selected groups of patients with chronic bronchitis may receive benefit from use of corticosteroids, bronchodilators, or prophylactic antibiotics. Lower Respiratory Infection - Pneumonia Pneumonia Pneumonia is an inflammation of the lung parenchyma Pneumonias occurring in usually healthy persons not confined to an institution are classified as community- acquired pneumonias. Infections arise while a patient is hospitalized or living in an institution such as a nursing home are called hospital-acquired or nosocomial pneumonias. Etiology of Pneumonia Bacterial pneumonias: Streptococcus pneumoniae is the most common agent of community-acquired acute bacterial pneumonia Staphylococcus aureus are also uncommon and usually occur after influenza or from staphylococcal bacteremia. Infections due to Haemophilus influenzae and Klebsiella pneumoniae are more common among patients over 50 years old who have chronic obstructive lung disease or alcoholism. Etiology of Pneumonia Nosocomial pneumonias: Commonly caused by aerobic gram-negative bacilli that rarely cause pneumonia in healthy individuals like Pseudomonas aeruginosa, Escherichia coli, Enterobacter, Proteus, and Klebsiella Less common agents causing pneumonias include Francisella tularensis, the agent of tularemia; Yersinia pestis, the agent of plague; and Neisseria meningitidis, which usually causes meningitis but can be associated with pneumonia Xanthomonas pseudomallei causes melioidosis, a chronic pneumonia in Southeast Asia. Atypical pneumonias: Mycoplasma pneumoniae produces pneumonia most commonly in young people between 5 and 19 years of age. Legionella species, including L pneumophila, can cause a wide range of clinical manifestations. The 1976 outbreak in Philadelphia was manifested as a typical serious pneumonia in affected individuals, with a mortality of 17%. These organisms can survive in water and cause pneumonia by inhalation from aerosolized tap water, respiratory devices, air conditioners and showers.  Chlamydia trachomatis causes pneumonia in neonates and young infants. C. psittaci is a known cause for occupational pneumonitis in bird handlers such as turkey farmers. Chlamydia pneumoniae has been associated with outbreaks of pneumonia in military recruits and on college campuses. Coxiella burnetii the rickettsia responsible for Q fever, is acquired by inhalation of spores from infected animal placentas and feces. Pneumonitis is one of the major manifestations of this systemic infection. Measles pneumonia may occur in adults. Other pneumonias: Cytomegalovirus can cause fatal pneumonitis in immunocompromised individuals Among the fungi, Cryptococcus neoformans and Sporothrix schenckii are found worldwide Pneumocystis carinii produces a life-threatening pneumonia among patients immunosuppressed by acquired immune deficiency syndrome (AIDS), hematologic cancers, or medical therapy. It is the most common cause of pneumonia among patients with AIDS when the CD4 cell counts drop below 200 Clinical Manifestation of Pneumonia The major symptoms or pneumonia are cough, chest pain, fever, shortness of breath and sputum production Patients are tachycardic Headache, confusion, abdominal pain, nausea, vomiting and diarrhea may be present, depending on the age of the patient and the organisms involved Laboratory Diagnosis of Pneumonia Sputum test for bacterial pneumonia Most fungal pneumonias are diagnosed on the basis of culture of sputum or lung tissue. Serologic test for pneumonia caused by viruses Bronchoscopy for pneumonia caused by Pneumocystis carinii Prevention and Treatment of Pneumonia Pneumococcal vaccine should be given to patients at high risk for developing pneumococcal infections, including the elderly and any patients immunocompromised through disease or medical therapy In AIDS patients, trimethoprim/sulfamethoxazole, aerosolized pentamidine or other antimicrobials can be given for prophylaxis of Pneumocystis carinii infections. Lower Respiratory Infection – Pulmonary Tuberculosis Etiology of Pulmonary Tuberculosis It is caused by Mycobacterium tuberculosis Mycobacterium tuberculosis It is obligate aerobic acid-fast bacillus. Virulence Factors: Mycolic acid – a large fatty acid Mycoside – a glycolipid (mycolic acid bounded to a carbohydrate) Clinical Manifestation of Pulmonary Tuberculosis Primary Tuberculosis Secondary or Reactivation Tuberculosis Primary Tuberculosis: It is usually asymptomatic Bacteria enter macrophages (M. tuberculosis is a facultative intracellular organism), multiply and spread via the lymphatics and blood stream to the regional lymph nodes, other areas of the lungs, and distant organs. Secondary or Reactivation Tuberculosis: Most adult cases of TB occur after the bacteria have been dormant for some time. It is presumed that temporary weakening of the immune system may precipitate the reactivation. Pulmonary tuberculosis – most common site; patients usually present with a chronic low grade fever, night sweats, weight loss, and a productive cough that may have blood in it Laboratory Diagnosis of Pulmonary Tuberculosis PPD Skin Test Chest X-ray Sputum and culture test (Purified Protein Derivative) PPD Skin Test It can reveal whether a person has been infected with M. tuberculosis. Intradermal injection of PPD will result to localized swelling and redness. A positive test is an area of induration (hardness) that is bigger than 10 mm after 48 hours. The test is positive at 5 mm induration in patients who are immunocompromised. Chest X-ray It will reveal scarring in the upper lobes of the lungs or presence of Ghon focus or Ghon complex. Sputum acid-fast stain and culture Prevention and Treatment of Tuberculosis Always cover your mouth when you cough or sneeze Wash your hands after coughing or sneezing Stay home from work, school, or other public places. Use a fan or open windows to move around fresh air. Don’t use public transportation INH, Rifampin, PZA, Ethambutol, Streptomycin