respiratory infections - microbiology

Dr. Ashish V. Jawarkar

Diseases of the Respiratory System


The Upper Respiratory System

Consists of:NosePharynx (throat)

Middle earEustachian tubes


The Lower Respiratory System

Consists of:LarynxTracheaBronchial tubes

AlveoliPleura


Upper Respiratory System defense

•Coarse hairs in the nose filter large particles from air entering the respiratory tract.•The ciliated mucous membranes of the nose and throat trap airborne particles and remove them from the body.•Lymphoid tissue, tonsils, and adenoids provide immunity to certain infections.



Lower respiratory tract defense

The lower respiratory system is usually sterile because of the action of the ciliary escalator.

Microorganisms hoping to infect the respiratory tract are caught in the sticky mucus and moved up by the mucociliary escalator.


Upper Respiratory System Diseases

Most respiratory tract infections are self-limiting.

Often caused by bacteria & viruses in combination


Upper Respiratory System Diseases

Pharyngitis: inflammation of the pharynx

Laryngitis: swelling and irritation (inflammation) of the voice box (larynx)

Tonsillitis: inflammation of the tonsils

Sinusitis: inflammation of the sinuses


Agents of URTi

S. pneumonia – pharyngitis/tonsillitisS. Pyogenes – pharyngitis / tonsillitisC. diphtheria - diptheriaB. pertussis – whooping coughCommon cold – rhino virus


Streptococcal Pharyngitis

Also called strep throat

Streptococcus pyogenes / strep. pneumoniae

Gram positive cocci chains


Corynebacterium Diphtheriae

Gram positive club shaped rod




Diphtheria

Diphtheria membrane: Fibrin, tissue, bacterial cells

•Leading infectious killer of children in U.S. in 1935•Leading infectious killer of children in U.S. in 1935


Diphtheria

Still common in developing countries where immunizations aren't given routinely.

Up to 40% to 50% of those who don't get treated can die.

The exotoxin inhibits protein synthesis, and heart, kidney, or nerve damage may result.

Prevented by DTP vaccine


Lab diagnosis

Microscopy – Gram’s , Albert’sCulture – selective media containing tellurite,

Loeffler’s serum slope


Pertussis / whooping cough

Causes whooping cough

Mostly in childrenCoughing thru

strained vocal cords produces sound


diagnosis

Mostly clinicalBacteria does not grow on ordinary mediaPrevented by vaccination – DPT


Bacteria, viruses, and fungi causeBronchitis – S. pneumoniaePneumonia – S. pneumoniae,

Klebsiella, MycoplasmaTuberculosis - M. tuberculosis

Lower Respiratory System Diseases


Mycoplasma

Bacteria with no cell wallsGram negative, better stained with Giemsa

stain


Grow on media enriched with serumColonies give fried egg appearance


Mycoplasmal Pneumonia

Primary atypical pneumonia; walking pneumonia No physical signs/symptoms X ray shows lower lobe pneumonia

Genitourinary infections



Viral Pneumonia

Viral pneumonia occurs as a complication of influenza, measles, or chickenpox

Viral etiology suspected if no other cause is determined


Respiratory Syncytial Virus (RSV)

The most common viral respiratory disease in infants; 4500 deaths annually

Causes cell fusion (syncytium) in cell cultureSymptoms: Pneumonia in infantsDiagnosis: Serological test for viruses and

antibodiesTreatment: Ribavirin, palivizumab


Influenza (Flu)

Symptoms: Chills, fever, headache, and muscle aches No intestinal symptoms

1% mortality, very young and very oldTreatment: Zanamivir and oseltamivir inhibit

neuraminidaseProphylaxis: Multivalent vaccine (currently

grown in Embryonated egg cultures


The Influenza Virus

Hemagglutinin (HA) spikes used for attachment to host cells

Neuraminidase (NA) spikes used to release virus from cell


Fungal Infections

Fungal spores are easily inhaled; they may germinate in the lower respiratory tract.

The incidence of fungal diseases has been increasing in recent years.

The mycoses can be treated with amphotericin B.


Health & Medicine

respiratory infections - microbiology