Bacteria Causing Respiratory tract infection



BACTERIAL DISEASES OF THE RESPIRATORY TRACT (As per Rajasthan Pharmacist syllabus)


Causative Pathogen

Signs and Symptoms


Diagnostic Tests


Acute otitis media (AOM)

Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis, others

Earache, possible effusion; may cause fever, nausea, vomiting, diarrhea

Often a secondary infection; bacteria from respiratory tract become trapped in eustachian tube, cause infection




Corynebacterium diphtheria (gram +)

Pseudomembrane on throat, possibly leading to suffocation and death

Inhalation of respiratory droplets or aerosols from infected person

Identification of bacteria in throat swabs; PCR to detect diphtheria toxin in vitro

DtaP, Tdap, DT, Td, DTP

Legionnaires disease

Legionella pneumophila(gram )

Cough, fever, muscle aches, headaches, nausea, vomiting, confusion; sometimes fatal

Inhalation of aerosols from contaminated water reservoirs

Isolation, using Warthin-Starry procedure, of bacteria in sputum


Pertussis (whooping cough)

Bordetella pertussis(gram )

Severe coughing with “whoop sound; chronic cough lasting several months; can be fatal in infants

Inhalation of respiratory droplets from infected person

Direct culture of throat swab, PCR, ELISA

DTaP, Tdap

Q fever

Coxiella burnetii

High fever, coughing, pneumonia, malaise; in chronic cases, potentially fatal endocarditis

Inhalation of aerosols of urine, feces, milk, or amniotic fluid of infected cattle, sheep, goats



URI/Streptococcal pharyngitis, scarlet fever

Streptococcus pyogenes(gram +)

Fever, sore throat, inflammation of pharynx and tonsils (mucosal membranes of the pharynx are damaged by the release of a variety of exoenzymes and exotoxins by this pathogen), petechiae, swollen lymph nodes; skin rash (scarlet fever), strawberry tongue

Direct contact, inhalation of respiratory droplets or aerosols from infected person

Direct culture of throat swab, rapid enzyme immunoassay



Mycobacterium tuberculosis(acid-fast, high G + C, gram+, nonspore-forming rod)

Formation of tubercles in lungs; rupture of tubercles, leading to chronic, bloody cough; healed tubercles (Ghon complexes) visible in radiographs; can be fatal

Inhalation of respiratory droplets or aerosols from infected person

Mantoux tuberculin skin test with chest radiograph to identify Ghon complexes





  • Acute otitis media is an infection of the middle ear, caused by several bacteria, including Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The infection can block the eustachian tubes, leading to otitis media with effusion.
  • Bacterial pneumonia results from infections that cause inflammation and fluid accumulation in the alveoli,  caused by S. pneumoniae or H. influenzae. 
  • Mycoplasma pneumonia results from infection by Mycoplasma pneumoniae
  • Chlamydial pneumonia can be caused by three pathogens that are obligate intracellular parasites. Chlamydophila pneumoniae is typically transmitted from an infected person, whereas C. psittaci is typically transmitted from an infected bird. Chlamydia trachomatis, may cause pneumonia in infants.
  • Tuberculosis infection leads to the production of protective tubercles in the alveoli and calcified Ghon complexes that can harbor the bacteria for a long time.
  • In Tuerculosis, bacteria infects the alveolis & phagocytized by macrophages.     but M. tuberculosis can survive and multiply within these phagocytes due to presence of the waxy mycolic acid in their cell walls which protect them &  not eliminated by macrophages. the infection result into an inflammatory response and an accumulation of neutrophils and macrophages in the infected area of alveloi. In the alveoli  small round lesions called tubercles. Bacteria continue to be grow into the the tubercles and results in tissue damage and induction of apoptosis (programmed host-cell death) in a process called liquefaction. This creates air pocket, where the aerobic M. tuberculosis can grow and multiply. Tubercles may eventually rupture and bacterial cells can invade pulmonary capillaries; from there, bacteria can spread through the bloodstream to other organs, a condition known as miliary tuberculosis. The rupture of tubercles also facilitates transmission of the bacteria to other individuals via droplet aerosols that exit the body in coughs.
  • Eventually, most lesions heal to form calcified Ghon complexes. These structures are visible on chest radiographs and are a useful diagnostic feature. But even after the disease has apparently ended, viable bacteria remain sequestered in these locations. Release of these organisms at a later time can produce reactivation tuberculosis or secondary TB.
  • Q fever is caused by Coxiella burnetii bacteria, whose primary hosts are domesticated mammals (zoonotic disease).
  • Sequelae of S. pyogenes Infections (aggressively treated with antibiotics), Leads to acute rheumatic fever and acute glomerulonephritis.
  • Rheumatic fever is damage to and inflammation of the heart (carditis)
  • Glomerulonephritis: an immune response to streptococcal antigens following pharyngitis and cutaneous infections.
  • Health Care-Associated Pneumonia: Klebsiella pneumoniae, Staphylococcus aureus
  • A pertussis infection :three distinct stages. The initial infection catarrhal stage, is relatively mild and unremarkable. The signs and symptoms may include nasal congestion, a runny nose, sneezing, and a low-grade fever. This stage is most infectious. Sec stage, paroxysmal stage, mucus accumulation leads to uncontrollable coughing spasms that can last for several minutes; whooping sound made is made during the paroxysmal stage. The paroxysmal stage can last for several weeks. A long 3rd stage convalescence stage, during which time patients experience a chronic cough that can last for up to several months.

PNEUMONIA:-  Itis a term for infections of the lungs that lead to inflammation and accumulation of fluids and WBC in the alveoli. Pneumonia can be caused by bacteria, viruses, fungi, and other organisms, but most of the majority of pneumonias are bacterial in origin.



Signs and Symptoms


Diagnostic Tests


Chlamydial pneumonia

Chlamydophila pneumoniae, C. psittaci, Chlamydia trachomatis

Bronchitis; mild to severe respiratory distress

Inhalation of respiratory droplets or aerosols from infected person (C. pneumoniae); exposure to infected bird (C. psittaci); exposure in the birth canal (Chlamydia trachomatis)

Tissue culture, PCR


Haemophilus pneumonia

Haemophilus influenza(gram )

Cough, fever or low body temperature, chills, chest pain, headache, fatigue

Inhalation of respiratory droplets or aerosols from infected person or asymptomatic carrier

Culture on chocolate agar, serotyping of blood or cerebrospinal fluid samples


Klebsiella pneumonia

Klebsiella pneumoniae, others

Lung necrosis, “currant jelly” sputum; often fatal

Health care associated; bacteria introduced via contaminated ventilators, intubation, or other medical equipment

Culture, PCR


Mycoplasma pneumonia (walking pneumonia)

Mycoplasma pneumoniae

Low fever, persistent cough

Inhalation of respiratory droplets or aerosols from infected person

Culture with penicillin, thallium acetate


Pneumococcal pneumonia

Streptococcus pneumoniae(gram +)

Productive cough, bloody sputum, fever, chills, chest pain, respiratory distress

Direct contact with respiratory secretions

Gram stain, blood agar culture with optichin and sodium deoxycholate, quellung reaction

Pneumococcal conjugate vaccine (PCV13), pneumococcal polysaccharide vaccine (PPSV23)

Pseudomonas pneumonia

Pseudomonas aeruginosa

Viscous fluid and chronic inflammation of lungs; often fatal

Health care associated; bacteria introduced via contaminated ventilators; also frequently affects patients with cystic fibrosis

Culture from sputum or other body fluid


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