Infectious Diseases of the Respiratory Tract PDF

INFECTIOUS DISEASES OF THE RESPIRATORY SYSTEM  LEARNING OUTCOMES At the end of the lesson, the student can: Define the terms related to the infections of the respiratory system; and Explain the pathogen, reservoir, portal of exit, mode of transmission, portal of entry, a...

INFECTIOUS DISEASES OF THE RESPIRATORY SYSTEM  LEARNING OUTCOMES At the end of the lesson, the student can: Define the terms related to the infections of the respiratory system; and Explain the pathogen, reservoir, portal of exit, mode of transmission, portal of entry, and susceptible hosts of the common infectious disease of the respiratory system Demonstrate critical thinking in analyzing given cases or situations RESPIRATORY TRACT UPPER RESPIRATORY TRACT Nose down to larynx including sinuses LOWER RESPIRATORY TRACT bronchial tree and lungs DISEASES OF THE UPPER RESPIRATORY TRACT COMMON COLDS ❖ “Acute rhinitis” ❖ considered as a common illness in both children and adult ❖ “rhinovirus”- most common cause a. RHINOVIRUSES ✓ main cause of the common colds ✓ non-enveloped RNA virus ✓ primarily affect the nose and conjunctiva b. CORONAVIRUS ✓ second most common cause of common cold ✓ enveloped RNA virus ✓ transmitted by respiratory aerosol ❖SARS ( Severe Acute Respiratory Syndrome) severe form of atypical pneumonia characterized by fever, non-productive cough, dyspnea, and hypoxia incubation period ranges from 2-10 days ❖ COVID-19 ▪ highly infectious disease caused by SARS-Coronavirus-2 (SARS-CoV-2) ▪ it is believed to have originated from bats ▪ Structural protein ( S protein or Spike protein) found on the surface of the virus ▪ Great Britain- where the Alpha Variant (B.1.1.7) initially emerged ▪ South Africa- where the Beta Variant emerged (B.1.351) emerged ▪ India – where Delta variant emerged (B.1.617.2) ▪ transmitted through inhalation of respiratory droplets from the nose or mouth, airborne transmission or through a person’s contact with objects or surfaces where the virus landed ❖ COVID-19 ▪ symptoms include flu-like symptoms of fever, dry cough, tiredness, body aches and pain, nasal congestion, headache, conjunctivitis, sore throat, diarrhea, loss of taste or smell. ▪ Diagnostic test: reverse transcriptase polymerase chain reaction (RT- PCR) ▪ Drugs used in the treatment of COVID-19 (US FDA APPROVED) ✓ Remdesivir – antiviral drug that is given IV ✓ Baricitinib and Tocilizumab – immune modulators ✓ Nirmatrevil and Ritonavir – oral antiviral ❖ COVID-19 how to prevent COVID-19 infection? ✓ frequent handwashing with soap or use of alcohol as hand sanitizers ✓Wearing of close-fitting face masks ✓ vaccination 1. vector vaccines ( AstraZeneca, Janssen and Gamaleya) 2. mRNA vaccines ( Pfizer and Moderna) 3. Inactivated vaccines ( Sinovac, Sinopharm and Bharat Biotech) c. ADENOVIRUS ✓ Non-enveloped DNA virus that causes pharyngitis, conjunctivitis, common cold, and pneumonia ✓ Mode of Transmission: ▪ aerosol droplets ▪ fecal-oral ▪ direct inoculation of conjuctivae by fingers ✓ Treatment and Prevention ▪ Live, non attenuated adenovirus vaccine for serotypes 4, 7 and 21 have been developed but was used only by the military PHARYNGITIS ❖ Inflammation of the mucous membranes of the pharynx NASOPHARYNGITIS ❖ Common illness of childhood, occurring more commonly during the cold weather months ❖ common caused by ADENOVIRUS TONSILLOPHARYNGITIS ❖ inflammation involving the both the pharynx and the tonsils ❖ common caused by Streptococcus pyogenes ❖ Mode of transmission: direct contact with large droplets or respiratory secretions ❖ the dx manifests with sudden onset of fever, sore throat, headache, nausea, malaise and pain ❖ gold standard for diagnosis is culture of specimen obtained by swab of the posterior pharyngeal and tonsillar region SCARLET FEVER ❖ Caused by S. pyogenes strains producing streptococcal pyrogenic exotoxin or erythrogenic toxin ❖ “ pinkish rash on the skin” ❖ strawberry-like appearance of the tongue ❖ DOC: Penicillin G. INFLUENZA ❖ An acute viral respiratory infection with fever, chills, headache, pains throughout the body, sore throat, cough, nasal drainage ❖ commonly known as “flu” ❖ caused by influenza viruses which are members of the family Orthomyxoviridae ❖ there are 3 immunologic types of influenza viruses: 1. Influenza A – responsible for the most cases of epidemics and pandemics. It is also the cause of influenza in birds (avian flu), pigs, horses. 2. Influenza B – mainly causes epidemics and infection is restricted to humans 3. Influenza c - INFLUENZA Two types of antigenic variation 1. Hemagglutinin (HA) / antigenic drift – is a minor change and is due to accumulation of point mutations in the gene resulting in amino acid changes involving the H antigen. This is seen in both influenza A and B. 2. Neuraminidase (NA) / antigenic shift – is a major change that involves rearrangement of the gene segments involving the H or N antigen, resulting in the development of new strain. It is responsible for pandemics and occurs only in influenza A. H5N1 – cause of the avian flu and is currently being closely monitored for fear that it can lead to the development of a pandemic “SPANISH FLU” – caused by influenza A(H1N1) “MEXICAN SWINE FLU” – A(H1N1) is a quadruple re-assortant virus resulting from the recombination of two strains from birds, one from swine and one from human “ASIAN FLU” and “ HONGKONG FLU” – caused by influenza A(H2N2) ❖Mode of transmission: ✓airborne respiratory droplets ❖ treatment and prevention: ✓Amantadine - treatment for influenza A Zanamivir (Relenza) ✓ Oseltamivir (Tamiflu) – treatment of both influenza A and B DIPHTHERIA ❖ caused by corynebacterium diptheriae ❖ gram-positive, non-spore-forming rods that are club-shaped and arranged in V- or L- shaped forms, giving rise to a “Chinese character” MOT: airborne droplets LABORATORY DIAGNOSIS: swabs from the nose, throat or other suspected lesions. Treatment and prevention: PEN G or ERYTHROMYCIN, Diphtheria toxoid is given in combination with tetanus toxoid and acellular pertussis (DTaP) DISEASES OF THE LOWER RESPIRATORY TRACT CHRONIC BRONCHITIS ❖ Inflammatory condition involving the brochi ❖ caused by S. pneumoniae and H influenzae. Other agents include adenovirus, Bordetella pertussis and parainfluenza virus BRONCHIOLITIS ❖ severe inflammatory condition involving the bronchioles caused by the Respiratory syncytial virus (RSV) ❖ RESPIRATORY SYNCYTIAL VIRUS (RSV) - RNA virus that belongs to the family Paramyxoviridae MOT: droplets and direct contact Clinical finding: bronchiolitis, common cold, influenza-like illness, pneumonia and otitis media Laboratory diagnosis: RT-PCR Treatment and Prevention: antiviral drug Ribavirin PNEUMONIA - Is an infection involving the lung parenchyma ACUTE BACTERIAL PNEUMONIA - Typically presents with abrupt onset of fever and chills, cough productive of purulent sputum and pleuritic chest pain COMMUNITY ACQUIRED PNEUMONIA - Caused by Streptococcus pneumoniae (most common), Mycoplasma pneumoniae and Legionella pneumophila NOSOCOMIAL PNEUMONIA - Most often caused by Escherichia coli, Pseudomonas aeruginosa and S. aureus VIRAL PNEUMONIA - Characterized by inflammation of the interstitial spaces - Commonly caused by RSV, parainfluenza virus, influenza virus, adenovirus, measles virus and varicella-zoster virus DIAGNOSIS: - can be made by Gram stain and microscopic examination of sputum specimen. - gold standard is through culture of the blood and sputum STREPTOCOCCUS PNEUMONIA - Also called pneumococci - a gram positive, encapsulated, lancet- shaped diplococci - They are alpha hemolytic and are normal inhabitants of the upper respiratory tract of 5-40% of humans and are transient flora of the nasopharynx MOT: - droplet of respiratory secretions LABORATORY DIAGNOSIS: - gram staining and microscopic examination of sputum - blood and sputum culture - capsular swelling test (Quellung reaction) - opthocin sensitivity TREATMENT AND PEVENTION: - PEN G, alternative drugs are ceftizoxime and vancomycin - primary prevention consists of administration of vaccine HAEMOPHILUS INFLUENZAE - Found on the mucous membranes of the upper respiratory tract in humans - most infection occur in children between the ages of 6 months to 6 years MOT: The organism enters the body through the upper respiratory tract CLINICAL FINDING: Sinusitis and otitis media Epiglotitis Meningitis Bronchitis and pneumonia LABORATORY DIAGNOSIS: - Microscopic examination of gram-stained specimen of pus, blood and spinal fluid TREATMENT AND PREVENTION - DOC is Ampicillin - Primary prevention is through vaccination of Hib vaccine to children MYCOPLASMA PNEUMONIAE - Smallest free-living organisms that can self-replicate in laboratory media MOT: - Transmission may be done person-to-person by means of infected respiratory secretions LABORTORY DIAGNOSIS: - Serologic testing and PCR TREATMENT AND PREVENTION: - DOC is either macrolide or a tetracycline antibiotics KLEBSIELLA PNEUMONIAE - Causes community-acquired and nosocomial infection CLINICAL FINDING: - Produces a primary lobar pneumonia that is characterized by production of thick, bloody sputum (current jelly sputum) LEGIONELLA PNEUMOPHILA - Legionellae are gram-negative rods that stain poorly with the standard gram stain - Causes diseases both in the community and hospitalized immunocompromised patients - major virulent factor is lipopolysaccharide (LPS) MOT: - Infected water source PERTUSSIS (WHOOPING COUGH) - Caused by Bordetella pertussis - is a small, encapsulated, gram negative rod MOT: - Airborne droplets during severe coughing episodes  3 STAGES OF PERTUSSIS 1. Catarrhal stage – most contagious stage and lasts 1-2 weeks 2. Paroxysmal stage – this stage is characterized by a series of 5- 20 forceful, hacking coughs accompanied by production of copious amount of mucus that ends in high pitched indrawn breath that makes the “whoop” noise. This may last for 2-10 weeks 3. Convalescent stage- this stage is characterized by a reduction in the symptoms of the patient leading to recovery. The patient is no longer contagious LABORATORY DIAGNOSIS: - It is done through the culture of specimens from nasopharyngeal swabs taken during the paroxysmal stage TREATMENT AND PREVENTION - DOC are macrolide antibiotics  TUBERCOLOSIS Caused by Mycobacterium tuberculosis - is an acid-fast, obligately aerobic bacillus that is stained poorly by dyes used in gram stain MOT: - Person-to-person spread through respiratory aerosols generated through coughing by infected individuals. CLINICAL FINDING: 1. Primary infection (Primary Complex) – represents initial infection in childhood. 2. Secondary or Reactive Pulmonary Tuberculosis – usually caused by tubercle bacilli that have survived in the primary lesion 3. Disseminated Tuberculosis – also called extrapulmonary tuberculosis. It is characterized by multiple disseminated lesions. LABORATORY DIAGNOSIS: 1. Acid-fast staining of sputum 2. Chest x-ray 3. Skin test TREATMENT AND PREVENTION: WHO recommend DOTS program (RIPES) Improvement of housing conditions and nutritional status of the population Careful follow-up of contacts of patients with active TB Use of mask and other respiratory isolation procedures Immunization with BCG vaccine