MicroBio Mod 13

Upper Respiratory System

Harbors pathogens suppressed by normal microbiota

Site of pharyngitis, sinusitis, tonsilitis

Most life threatening: inflammation of epiglottis

• hemophiles influenzae

• prevented by HiB vaccine

Lower Respiratory System

Nearly Sterile because of the ciliary escalator found lining bronchial tubes.

Organisms from upper can infect the lower.

Consists of larynx and everything below it.

Strep throat

Streptococcus pyogenes

Resistant to phagocytes

Streptokinase lyse clots

Streptolysins are cytotoxic

• kill WBCs and tissue cells

• erythrogenic toxin, if produced, makes it scarlet fever.

• presence of this gene in the bacteria is a result of an infection with a bacteriophage and incorporation of viral DNA into the bacterial host cell.

Diagnosis by agglutination (rapid strep test); swab throat and react with anti-strep Ab.

Diphtheria

Corynebacterium diphtheriae

Gram-positive bacillus, non spore-forming

Pleomorphic

Fatal in kids

Diphtheria membrane of fibrin, dead tissue, and bacteria in the back of the throat.

Toxin produced by lysogenized C. diphtheriae

• can cause organ failure

Cutaneous diphtheria: infected skin wound can lead to slow healing ulcer

Otitis

S. pneumoniae (35%)

H. influenzae (20-30%)

• both are the more frequent causes of ear infections

M. catarrhalis (10-15%)

S. pyogenes (8-10%)

S. aureus (1-2%)

Ear infection:

• kids more susceptible because ear tubes are smaller and can get clogged easier.

• pain from the build-up of pus and fluid behind the eardrum causing it to bulge out.

Common cold

Rhinovirus (50%)

Coronavirus (15-20%)

Spread by droplet transmission

Sinusitis often follows

Symptoms:

• nasal congestion, pressure above the nose or in the forehead, headache or toothache, facial swelling and tenderness.

• discharge appears opaque with a green or yellow color in the case of bacterial infection

• discharge caused by allergy is clear and may be accompanied by itchy, watery eyes.

Bacterial pneumonia

Streptococcus pneumoniae

Gram-positive encapsulated diplococci

Main cause of pneumonia (any other cause is atypical)

Symptoms:

• high fever

• chest pain

• difficulty breathing

• rust-colored sputum

Diagnosis by culturing bacteria (slimy appearance on plate: capsule)

Haemophilus influenzae pneumonia

Gram-neg coccobacillus

Can also cause epiglottitis, ear infections, meningitis

Pre-disposing factors: alcoholism, poor nutrition, cancer, or diabetes.

Mycoplasmal pneumonia (most common after pneumonococcal)

20% of cases

mycoplasma pneumoniae

• pleomorphic, wall-less bacteria

• aka walking pneumonia

Not easily cultured

• looks like a fried-egg in shape when successfully cultured on a horse serum and yeast extract medium.

• can take 3 weeks to see growth

Clinically resembles chlamydia

Tetracycline as treatment

Tuberculosis

Mycobacterium tuberculosis

• acid-fast bacilli containing lipid-rich cell wall

• transmitted human to human

M. bovis

• associate with cattle

• <1% US. cases

• not transmitted human to human

M, avian-intracellular

• affects immunocompromised

• complex infects people with late stage HIV infections

Pathogenesis:

• Bacteria inhaled and become phagocytized

• get walled off by body in tubercules (lumps)

• calcify and become visible by x-rays

Diagnosis: tuberculin skin test screening

Prolonged treatment with multiple antibiotics

Whooping cough

Bordetella pertussis

• gram-neg coccobacillus

Capsule to evade phagocytes

Produce toxins

• tracheal cytotoxin of cell wall damaged ciliated cells

• pertussis toxin (responsible for systematic symptoms like fever and inflammation)

Prevented by DTaP vaccine

Stage 1: Catarrhal stage, like common cold

Stage 2: Paroxysmal stage: violent coughing

• can cause broke ribs in young children and obstruct airways in infants

• can last 8-10 weeks

Stage 3: Convalescence

• can take months to years

Legionellosis

Legionella pneumophila

Gram-neg bacillus

Reproduce in macrophages

Opportunistic

Pneumonia-like: high fever, cough

L. pneumophila found in water

Transmitted by inhaling aerosols

Q fever

Caused by Coxiella burnetti

• obligately parasitic, intracellular bacteria

Can replicate in cells and are transmitted through the air

Acute Q fever:

• fever, aches, coughing

Chronic Q fever:

• endocarditis

Transmitted to farm animals from tick bites

Pathogenicity from endospore-like structure

Meliodosis

Caused by burkholderia pseudomallei

Gram-neg rod

Occurs in moist soil

Se Asia and Australia

Affects those with lowered immune systems

Transmission by inhalation, puncture wounds, ingestion

Long-term treatment

Viral pneumonia

Complication of influenza, measles, chickenpox

Respiratory Syncytial Virus (RSV):

• common in infants; 4500 deaths annually

• coughing, wheezing (no fever)

Coronaviruses:

• SARS

• MERS (camel reservoir)

• SARS-CoV2

Flu

Influenza

Symptoms:

• fever, headache, chills, muscle aches

30-50k deaths annually

Composition of vaccine determined annually by the identification of circulating viruses.

• does not provide long-term immunity

Flu Serotypes

A: causes most epidemics

B: moderate, local outbreaks

C: mild disease

Hemagglutinin (HA) spikes

• recognize and attach to host cells

• 18 subtypes

Neuraminidase (NA) spikes

• help virus separate from infected cell

• 11 subtypes

Genome contains 8 RNA segments

Flu epidemics increasing in frequency

Antigenic shifts creates new viruses

Antigenic drift

• minor antigenic changes in HA and NA

• allows virus to elude some host immunity

Antigenic shifts

• changes great enough to evade most immunity

• lead to pandemics

• involve the reassortment of the eight RNA segments

Avian, Swine, and Mammalian strains

• swine serve as “mixing vessels” for new strains

Fungal pneumonia

Dimorphic fungi

• Histoplasma capsulatum

• Blastomyces dermatidis

• Coccidiodes immitis

Transmitted by airborne conidia from soil

Pneumocystis pneumonia

Pneumocysts jirovecii found in healthy, human lungs (yeast-like infection)

Occurs in newly infected infants and immunosuppressed individuals

• marker for AIDS