PersonPerson Diseases Chapter 26

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Person-Person DiseasesChapter 26
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Mode of Transmission

• Airborne
• Direct contact
• Sexual contact

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Airborne Transmission

• Aerosols
• Respiratory diseases ex. M.tuberculosis
• Indoor vs. outdoor
• Air not a suitable growth media, survival in air
  is limited exceptions include Staphylococcus and
  Streptococcus
• Gram-positive more resistant to drying out due to
  hardy structure

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Bacterial Respiratory Pathogens

• Humans are primary reservoir
• Gram-positive
• Respond readily to antibiotics vaccinations
• Streptococci non-sporulating, anaerobic
  gram-positive cocci
• Streptococcus pyogenes respiratory route
  elongated chains found in normal flora in small
  numbers
• Streptococcus pneumoniae normal flora of 40
  grow in pairs or short chains and produce a
  polysaccharide capsule

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Bacterial Respiratory Pathogens (Contd.)

• S.pyogenes
• streptococcal pharyngitis i.e. strep throat
• beta-hemolysis
• Symptoms fever, malaise, sore throat, enlarged
  tonsils
• Rapid treatment recommended, as can lead to TSS,
  scarlet fever, rheumatic fever etc. (Exotoxin A,
  a super antigen-massive inflammation)
• Systemic infection necrotizing fasciitis
• Extensive destruction of subcutaneous tissue i.e.
  flesh-eating bacteria
• Rheumatic fever delayed sequelae
• Cell-surface antigens similar to human
  cell-surface antigens causing antibodies to
  self-destruct (autoimmune disease)
• Acute glomerulonephritis painful kidney disease
• Antigen-antibody complexes accumulate in blood
  and kidney causing inflammation
• Treatable
• 60 strains multiple infection is possible
  vaccine unavailable
• Rapid antigen detection systems (RAD) surface
  antigens extracted from swab of patients throat
  throat culture done on blood agar antibody titer
  indicative of a recent infection

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Bacterial Respiratory Pathogens (Contd.)
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Bacterial Respiratory Pathogens (Contd.)

• S.pneumoniae
• Lung infections
• Encapsulated strains particularly invasive
• Reduced lung function due to accumulation of
  phagocytic cells
• Bacteremia can result in serious infections
• 90 strains
• Multivalent vaccine available for protection
  against several strains
• Penicillin and erythromycin

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Corynebacterium diptheriae

• Causative agent of diptheriae
• Gram-positive, non-motile, aerobic, irregular
  rods (club)
• Cells lodge in throat and tonsils
• Inflammation results in formation of a
  characteristic lesion pseudomembrane
• Diptheriae toxin induces host cell lysis
• Suffocation and tissue destruction can be lethal
• Vaccine (DTP)
• Treatment antitoxin and antibiotics

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Corynebacterium diptheriae
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Bordetella Pertussis

• B.pertussis gram-negative, aerobic coccobacillus
• Highly infectious disease of childhood (under 5
  yrs.)
• Exotoxins and endotoxins cause tissue damage
• Vaccine (DTP)

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Mycobacterium leprae

• Leprosy
• Folded, bulb-like lesions on the face and
  extremities
• Destruction of peripheral nerves and loss of
  motor function
• Incubation time varies weeks-years-decades

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Mycobacterium leprae
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Viral Respiratory Infections

• Measles
• Paramyxovirus
• Systemic viremia
• MMR vaccine
• Mumps
• Paramyxovirus
• Inflammation of salivary glands swelling of jaw
  and neck
• MMR Vaccine
• Rubella
• Togavirus
• Milder symptoms than measles
• MMR vaccine

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MMR
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• Chickenpox
• Varicella zoster virus
• Virus can remain dormant in nerve cells without
  overt symptoms Shingles
• Common cold
• Rhinovirus
• Nasal discharge, cough, chills and sore throat
• Influenza
• Orthomyxovirus
• Fever, headache, malaise, vomiting and diarrhea
  

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Direct Contact

• Contact with infected individual or blood/excreta
  
• Staphylococci gram cocci that form irregular
  clumps, resident skin flora, cause infections is
  susceptible individuals
• S.epidermis non-pigmented skin or mucous
  membranes
• S.aureus yellow-pigmented pathogenic
• Acne, boils, impetigo, meningitis, arthritis
• S.aureus leukocidin and coagulase toxins
• Differentiated from streptococci by catalase test
  
• TSS super antigen toxin, massive T-cell reaction
  
• Nosocomial infections prevalent due to antibiotic
  resistance

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Hepatitis Viruses

• Cirrhosis destruction of liver cells
• Hepatitis A
• person-person or contaminated food or water
  (shellfish due to waters polluted by fecal
  material) i.e. infectious hepatitis
• 30 of individuals have Abs to HAV
• Hepatitis B
• HBV is referred to as serum hepatitis
• Blood transfusion or needle sharing
• Vaccines

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Sexually Transmitted Infections

• STD/STI/Venereal diseases
• Found primarily in bodily fluids i.e. sensitive
  to drying out, heat and light thereby colonize
  the genitourinary tract
• Challenging to treat
• Asymptomatic
• Source is hard to find
• Social stigma prevents rapid intervention
• Treatable conditions when ignored can lead to
  long-term damage such as infertility, cancer etc.
  
• Gonorrhea is asymptomatic in women can lead to
  PID contributing to sterility
• Acquired immunity does not exist
• Use of oral contraceptives alters environment in
  favor of pathogen

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Sexually Transmitted Infections

• Syphilis spirochete T.pallidum
• Transmitted to fetus congenital syphilis
• Primary syphilis chancre appears at site of
  entry in 2 weeks- 2 months
• Secondary syphilis generalized skin rash due to
  spread of organisms from initial site of entry
• Tertiary syphilis severity is variable can lead
  to paralysis or neurological damage
• Low incidence in U.S

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Sexually Transmitted Infections

• Herpes
• HSV-1
• Epithelial cells around mouth and lips can
  infect other sites
• Virus persists in nerve tissue latent infections
• HSV-2
• blisters primarily on genitals