Respiratory Infectious Diseases

Streptococcus pneumoniae- (G+ cocci)

Normal flora of nasopharynx

Disease: pneumococcal pneumonia- typical wet pneumonia (cough, chest pain, fever)

~1 million cases, 400,000 hospitalizations per year in U.S.

Large capsule layer produced as virulence factor (avoid phagocytosis)

Bacterium can cause bacteremia, meningitis (~4,000 deaths per year U.S.)

Transmission: Opportunistic when large quantity is inhaled into lungs, inflammatory response causes fluid build-up

Poor nutrition, smoking, viral infections contribute to virulence

Treatment and prevention: typical antibiotics, vaccine

Mycoplasma pneumoniae- (bacteria without cell wall)

Pleomorphic, fragile bacteria

Disease: primary atypical (walking) pneumonia

Mild fever, fatigue, dry and unproductive cough, sore throat (chest cold)

Transmission: respiratory droplets person to person (causing as much as 1 in 5 cases of pneumonia)

Treatment: typical antibiotics (but not those that inhibit cell wall synthesis)

Mycobacterium tuberculosis- (AF+, waxy bacillus)

Kills 1-2 million people annually worldwide, 1/3 world population infected (Q of I may be just one bacterium)

Disease: Tuberculosis (TB) in 30% infected (70% asymptomatic)

90%- mild fever, flu-like, acute (bacteria become captured by macrophages in lungs, but not digested)

10%- severe cough, chest pain, high fever, bloody sputum due to ruptured/perforated lungs (50% mortality if untreated)

(can spread from lungs to other organs like kidneys, liver, bone, etc.)

Transmission- direct respiratory droplets and infected sputum

Streptococcus agalactiae- (known as Group B Strep)

Disease: most prevalent cause of neonatal pneumonia and meningitis in U.S. (50%)

Adults – pneumonia, skin infections, sepsis

Transmission: normal flora of vagina, pharynx, large intestine

Pregnant women screened for vaginal colonization in 3rd trimester (25% carriers)

5% mortality in infants, deafness, developmental disabilities

Treatment: antibiotics and immunotherapy

Streptococcus pyogenes- (Group A Strep)

Normal flora of throat, nasopharynx, sometimes skin

Virulence: release of toxins, harmful enzymes, damage from strong immune response

Transmission: 5-15% population carriers…direct respiratory droplets, food

Disease: pharyngitis and tonsillitis (strep throat)- red, enlarged, tender throat, fever, headache, nausea, white pus nodules

strep throat can lead to:

Scarlet fever- red rash of skin, strawberry tongue (~10%)

Rheumatic fever- delayed inflammation of joints, subQ tissue, kidneys, heart causing endocarditis and heart valve damage (antibodies cross-reactive to muscle protein)

Bordetella pertussis- (small G- bacilli)

Disease: pertussis (whooping cough), “100-day cough”

7-10 day incubation, 1-2 weeks non-specific resp symptoms, 2-4 week whooping cough with long, slow recovery

Caused by- attachment to cilia of upper resp. tract, produce 5 toxins which increase mucus secretions, inhibit phagocytosis, paralyze cilia

Transmission: respiratory droplets (human only known reservoir) (Ro = 5-6)

Treatment and prevention: macrolides (reduce duration, does not eliminate symptoms), vaccine

Mumps Virus- (a Paramyxovirus)

Disease: mumps (12-25 day onset)- infected salivary glands, swollen cheeks, fever, muscle aches, malaise

Complications can be encephalitis, meningitis, swelling of testes or ovaries, permanent deafness, spontaneous abortion

Transmission: (Human only host) saliva and resp droplet direct or by fomite into lungs (Ro = 4-7)

Last two years over 5,000 cases per year U.S., mainly college campuses

Prevention: vaccine (in MMR vaccine)

Influenza virus- (enveloped RNA)

Rapidly mutated virus, many known strains

Disease: Flu- rapid onset of fever, fatigue, headache, muscle pain

(often complicated by secondary infection)

Transmission: respiratory droplets into lungs (humans, pigs, avian all known reservoirs)

Treatment and Prevention: Tamaflu™ and vaccine available

Respiratory Syncytial Virus- (enveloped RNA)

Disease: RSV (viral pneumonia)

Most common lower resp infection in children under 2 (40% show symptoms, 2% hospitalized)

Causes respiratory cells to fuse (syncytium formation) and lose function

Flu-like symptoms in adults

Transmission: resp droplets…for 1-4 weeks following recovery

Rhinovirus, Echovirus, Coronavirus, Human Metapneumovirus, Parainfluenza virus, Adenovirus, etc.

Disease: Common Cold- runny nose, cough, mild fever

Transmission: resp droplets