microbial disease of the respiratory system

cutaneous diphtheria

Corynebacterium diphtheria infect skin through a wound and causes slow healing ulcerations, that are covered by a gray membrane. minimal circulation of toxin

diphtheria (2)

DTaP - a triple vaccine, a part of the normal immunization program: protect against diphtheria, tetanus and pertussis D in the vaccine represent Diphtheria taxied vaccine which is made of inactivated diphtheria toxin. provide protection against diphtheria toxin when we formed antibodies against the vaccine

diphtheria

-etiological agent: Corynebacterium diphtheria gram positive rod, pleomorphic (variable morphology, most club-shaped bacteria) -signs and symptoms: sore throat, fever, malaise, swelling of the neck. A tough grayish membrane forms at the back of the throat (characteristic of diphtheria) that can complete block the passage of air to the lungs -pathogenesis and virulence factors: the bacterium is not invasive but the toxin is highly virulent and can be fatal when heart and kidneys are affected by the toxin (exotoxin circulating in blood interferes with protein synthesis) only the lysogeizd strain of the bacterium (carrying lysogenic phage DNA in bacterial chromosome) can produce the toxin

Streptococcal Pharyngitis (Strep Throat)

-etiological agent: Streptococcus pyogenes, a type of Group A streptococci, gram-positive bacteria -signs and symptoms: local inflammation, fever, tonsillitis, enlarged lymph nodes in the neck -pathogenesis and virulence factors: 1. resistant to phagocytosis 2. streptokinase enzyme lyses clots 3. streptolysisns (toxin) are cytotoxic to tissue cells, RBC's and leukocytes some infections of sore throat can also be caused by viruses. Therefore, a rapid diagnostics test is necessary before prescribing antibiotics

scarlet fever

-etiological agent: when streptococcus pyogenes strain, (producing streptococcal pharyngitis/strep throat), produced an erythrogenic (reddening) toxin, scarlet fever results -signs and symptoms: red skin rash due to circulating toxin, fever, and red, enlarged tongue with spotted, strawberry like appearance -pathogenesis and virulence factors: only the strain lysogemzed by a bacteriophage (carrying a lysogenic phage DNA in its own chromosome) is able to produce the toxin usually mild but need antibiotic treatment to avoid further complication of rheumatic fever

structures of the lower respiratory system

-larynx -trachea -bronchial tubes -alveoli -pleura

how do we prevent microorganisms from entering the respiratory system?

1. hair and nasal passages work as filters, sweeping particles away 2. IgA antibodies in nasal secretions or mucus 3. Normal microbiota provides competitive exclusion 4. ciliary escalator moves inhaled particles towards throat, away from lower respiratory tract 5. alveolar macrophages capture microorganisms in lung tissue (usually, the lower respiratory tract is nearly sterile)