BACTERIAL INFECTIONS OF THE RESPIRATORY TRACT A Presentation By Ms R.Venkatajothi, MSc., MPhil, PhD Senior Lecturer Department of Microbiology Faculty of Medicine AIMST UNIVERSITY

OBJECTIVES The objectives of this lecture are to Discuss the common bacterial causes of respiratory infections. Host factors predisposing to infections; pathogenesis; laboratory diagnosis.

INTRODUCTION  Respiratory tract infection is define as any infectious diseases involving in the respirator tract.  Respiratory tract infections (RTIs) can be caused by viruses, bacteria, fungi and parasites.  Most common respiratory tract infections such as colds, sore throats, sinusitis, pneumonia, and Bronchitis are caused by bacteria.  Antibiotics are useful for the treatment and they are given according to their antibiotic sensitivity test result.

COMMON BACTERIAL CAUSES OF RESPIRATORY INFECTIONS GRAM POSITIVE BACTERIA  Group A beta-hemolytic streptococcus pyogenes.  Streptococcus pneumoniae.  Staphylococcus aureus.  Coagulase -negative staphylococci.  Mycobacterium tuberculosis.  Mycoplasma pneumoniae.  Corynebacterium diphtheriae.

Common bacterial causes of Respiratory infections continued….. GRAM NEGATIVE BACTERIA  Haemophilus influenzae.  Other Haemophilus species.  Chlamydophila pneumoniae (Taiwan acute respiratory agent (TWAR).  Klebsiella pneumoniae.  Neisseria meningitidis.  Pseudomonas aeruginosa.

HOST FACTORS PREDISPOSING TO INFECTIONS  Close contact with individual who have infected with respiratory infection.  Most URIs occur more frequently during the cold winter months, because of overcrowding.  Children younger than 5 years old.  In particular, closed settings such as home, school, college, traveling and tours etc., have higher attack rates.

Host factors predisposing to infections continued……  Poor hand washing after contact with an individual with upper respiratory infection.  Cigarette smoking or inhalation of Cigarette smoking.  Health care facilities, lab, hospitals and nursing homes etc.  People with weakened immune systems (e.g. due to HIV, cancer and some medicines).

GENERAL PATHOGENESIS OF RTI  The Respiratory tract is the most common site of infection by pathogens.  It can be spreads from person to person by airborne droplets or by contact with contaminated hands or surfaces.  Respiratory tract infection (RTI) classified into upper respiratory tract infection (URI) and lower respiratory tract infection (LRI).

GENERAL PATHOGENESIS OF RTI Respiratory tract infection

General pathogenesis of RTI continued…. The principal function of the respiratory tract is gas exchange. It is therefore constantly exposed to the gaseous environment such as bacteria, viruses, fungi and spores etc. Transmission of organisms occurs by aerosol, droplet, or direct hand-to-hand contact with infected secretions etc.

General pathogenesis of RTI continued…. The defenses of the respiratory tract are a reflection of its susceptibility to microbial attack. Direct invasion of the respiratory epithelium results in symptoms corresponding to the area (s) involved. Organisms reach the trachea and bronchi stick to the respiratory mucus lining their walls

General pathogenesis of RTI continued…. Sinusitis and acute bronchitis are frequently preceded by a common cold. Human behavior can also increase the risk of respiratory infection. Tobacco smoking has this effect by reducing the efficiency of cilial function and by causing the production of more viscous respiratory secretions.

COMMON RESPIRATORY TRACT INFECTIONS AND INFECTIOUS ORGANISMS

COMMON RESPIRATORY TRACT INFECTIONS UPPER RESPIRATORY TRACT INFECTION  An upper respiratory tract infection is an infectious process of any of the components of the upper airway.  Upper respiratory tract comprises nose, sinuses, pharynx and larynx.  The common URI are rhinitis, tonsillitis, pharyngitis, sinusitis, otitis media and common cold.  Symptoms of URI's commonly include cough, sore throat, runny nose, nasal congestion, headache, low grade fever, facial pressure and sneezing etc.

Upper respiratory tract infection continued…….  Onset of symptoms usually begins 1–3 days after exposure and the illness usually lasts 7–10 days.  Group A beta hemolytic streptococcal pharyngitis/tonsillitis (Strep throat) typically presents with a sudden onset of sore throat, pain with swallowing and fever.  Strep throat does not usually cause runny nose, voice changes or cough.  Pain and pressure of the ear caused by a middle ear infection (Otitis media).

Upper respiratory tract infection continued…….  Some of the common pathogens for URI infection are following;  group A beta-hemolytic Streptococcus pyogenes.  Haemophilus influenzae.  Neisseria gonorrhoeae.  Pseudomonas aeruginosa.  Bordetella pertussis (whooping cough).  Chlamydia pneumoniae.  Mycoplasma pneumoniae.  Corynebacterium diphtheriae.

LOWER RESPIRATORY TRACT INFECTION  Lower respiratory tract infections are generally more serious than URI.  The most common two infections involve in lower respiratory tract are bronchitis and pneumonia.  Pneumonia is classified as either community or hospital acquired depending on where the patient contracted the infection.  Symptoms include shortness of breath, weakness, high fever, coughing and fatigue.

LOWER RESPIRATORY TRACT INFECTION Pneumonia Bronchitis

Lower respiratory tract infection continued…. Pneumonia  Pneumonia is a condition in which there is an infection of the lung. Pneumonia is also the leading cause of death in children less than five years of age.  It is life-threatening in the elderly or those who are immunocompromised.  The most common cause of pneumonia is pneumococcal bacteria, Streptococcus pneumoniae accounts for 2/3 of bacteremic pneumonias.

Pneumonia continued….  Alcoholism predisposes to aspiration, but cigarette smoking is the main avoidable risk factor for community-acquired pneumonia in adults.  Pneumonia is the third most common hospital acquired (nosocomial) infection but the most common one to cause death.  Nosocomial pneumonia is most often caused by P.aeruginosa, S. aureus and Enterobacteriaceae.  Chronic pneumonia has a most dangerous and prolonged course than acute pneumonia.

Pneumonia continued….  There is no single symptom complex, so the diagnosis is often based on radiological findings.  Features of chronic sepsis such as weight loss and anorexia may also be present. Cough may be productive of purulent sputum, occasionally bloodstained.  The most common infective cause is pulmonary tuberculosis. Other infective causes include atypical mycobacteria, other bacteria and fungi.  Atypical pneumonia refers to pneumonia caused by Legionella pneumophila, Mycoplasma pneumoniae, and Chlamydia pneumoniae.

Lower respiratory tract infection continued…. Bronchitis  Bronchitis is inflammation of the mucous membranes of the bronchi, the airways that carry airflow from the trachea into the lungs.  Bronchitis can be divided into two categories, acute and chronic.  Acute bronchitis (“Chest Cold”) is characterized by the development of a cough, with or without the production of sputum, mucus.

Bronchitis continued….  Acute bronchitis often occurs during the course of an acute viral illness such as the common cold or influenza.  Viruses cause about 90% of cases of acute bronchitis, whereas bacteria account for fewer than 10%.  Acute bronchitis can caused by Mycoplasma pneumoniae, Haemophilus influenzae, Streptococcus pneumoniae and Chlamydophila pneumoniae etc.

Bronchitis continued….  Chronic bronchitis is caused by recurring injury or irritation to the respiratory epithelium of the bronchi, resulting in chronic inflammation, edema (swelling), and increased production of mucus.  Chronic bronchitis, a type of chronic obstructive pulmonary disease (COPD), is characterized by the presence of a productive cough that lasts for three months or more years.  Chronic bronchitis most often develops due to recurrent injury to the airways caused by inhaled irritants, Cigarette smoking or other forms of tobacco is the most common cause, followed by air pollution, heredity, frequent LRI and immunodeficiency disorders etc.

Bronchitis continued….  The cough is worse soon after awakening, the sputum produced yellow or greenish color and may be streaked with blood.  Cultures of sputum often shows strains of H.influenzae, S.pneumoniae, S.aureus, M.pneumoniae and L. pneumophila etc.  Chlamydia pneumoniae is more strongly associated with chronic bronchitis than acute bronchitis. PREVENTION OF RTI Maintain personal hygienic and keep the living environment hygienic.

GENERAL LABORATORY DIAGNOSIS OF RTI GRAM POSITIVE BACTERIAL INFECTIONS  Specimen – Sputum, Pus, Ear swab, Nasal or Throat swab, Eye swab. Gram staining, Colony count. Culture media – Nutrient agar media, Blood agar media and other suitable selective media.

Gram Positive Bacterial Infections continued…  BIOCHEMICAL TEST:- Catalase test, Oxidase test, Coagulase, Sugar fermentation test and other suitable biochemical test etc. Serological diagnosis and Molecular test. Antibiotic sensitivity test.

Gram Positive Bacteria S.aureus Streptococcus pyogenes

GRAM NEGATIVE BACTERIAL INFECTIONS  Specimen – Sputum, Pus, Throat swab, Ear swab, Eye swab. Gram staining Culture media – Nutrient agar media, Blood agar media, MacConkey agar media and other suitable selective media.

Gram Negative bacterial infections continued.  BIOCHEMICAL TEST:- IMViC Test, Sugar fermentation test and other suitable biochemical test etc. Serological diagnosis and Molecular test. Antibiotic sensitivity test.  Other lab diagnosis such as chest X-ray, CT scan and MRI etc., are very useful for the confirmation of RTI infections.

Gram Negative bacteria  Haemophilus influenzae Pseudomonas aeruginosa

LEARNING OUTCOMES At the end of the lecture, students should be able to  List the bacterial pathogens that can cause common respiratory infections and pneumonia.  Relate and match the various types of bacterial respiratory tract infections with the common aetiological agents.  Construct a flowchart of the steps involved in the laboratory diagnosis of the causative agents of bacterial respiratory tract infections.

LIST OF REFERENCE BOOKS The objectives of this lecture are to  Text book of Microbiology for Dental students by D.R. Arora and Hina Arora.  Microbiology by Lansing M. Prescott, John P. Harley and Donald A. Klein.  Text book of Microbiology by Ananthanarayan and Paniker’s.  Medical Microbiology by Patrick R. Murray, Ken S. Rosenthal and Michael A. Pfaller.