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Chapter 26Infectious Diseases
Pathophysiologyof Disease
An Introduction to Clinical Medicine
Seventh Edition
a LANGE medical book
CHAPTER 4
Infectious Diseases
Infection and the Body’s Defense Mechanisms
• There are several microorganisms that live on and in the human body that do not produce signs of illness
• Referred to as indigenous flora, these bacteria can also be helpful
• Pathogens are microorganisms that produce signs of illness
Infection and the Body’s Defense Mechanisms
• The innate immune system– Structural barriers
• Skin and mucous membranes– Inflammatory response
• The acquired immune system– Humoral system– Cellular immune system– Immunization
Most Frequent and Serious Problems
• Bacterial Infections– Secondary infections, sexually transmitted
infections
• Viral Infections– Upper respiratory illnesses– Gastroenteritis– Cold sores– HIV
Most Frequent and Serious Problems
• Rickettsial Infections– Rocky Mountain Spotted Fever
• Fungal Infections– Candida
Most Frequent and Serious Problems
• Protozoal Infections– Malaria
• Helminth Infections– Roundworms
Symptoms, Signs, and Tests
• Rapid onset of muscle aches, fatigue, fever, malaise
• Physical exam– Many lesions are characteristic enough to
be diagnostic
Symptoms, Signs, and Tests
• Laboratory testing– Culture: most commonly used for bacteria
• Once the bacteria is identified, it is tested for susceptibility to various antibiotics
– Gram stains• Allow for an “educated guess” about
antibiotic coverage while waiting for the organism to be identified
Specific Diseases
• Staphylococcal Infections– S. aureus can develop into Methicillin
Resistant S. aureus and cause serious illness in some patients
Specific Diseases
• Group A Streptococcal Infections– Strep A is the most virulent, and common in
upper respiratory infections– Scarlet fever– Necrotizing fascitis
Specific Diseases
• Streptococcus pneumoniae– Common cause of pneumonia
• Neisseria meningitidis– Meningococcal Menigitis
Specific Diseases
• Haemophilus influenzae– Common cause of ear infections and
sinusitis– Other serious illnesses caused by this
bacteria have been eliminated through immunization
Specific Diseases
• Legionellosis– Gram negative bacteria that thrives in water
reservoirs and cooling towers– A common cause of community acquired
pneumonia
Specific Diseases
• Nonfastidious Gram-Negative Rods– Enteric bacteria– When these bacteria cause sepsis, they
often lead to septic shock with a mortality rate of up to 50%
Specific Diseases• Anaerobic Bacteria
– Bacteria that grow with little oxygen• Sexually Transmitted Infections
Specific Diseases• Anaerobic Bacteria
– Bacteria that grow with little oxygen• Sexually Transmitted Infections
Specific Diseases
• Bacterial Infections Mediated by Exotoxins– Clostridium Family
• Tetani (tetanus)• Botulinum (botulism)• Difficile (entercolitis, not exotoxin
mediated)• Perfringens (gas gangrene)
– Diptheria
Specific Diseases
• Bordetella pertussis (whooping cough)– Not as prevalent in young children due to
immunization, though resurgence in older children and adults suggests the vaccine needs to be re-administered
Specific Diseases
• Mycoplasma Disease– Common cause of atypical pneumonia
• Lyme Disease– Tick borne disease
Specific Diseases
• Plague
• Tularemia
• Brucellosis
• Leprosy
Specific Diseases
• Viral Infections– Do not respond to antibiotic therapy and
are best treated with supportive mechanisms
– Few anti-viral medications are available to decrease the duration of illness
– Immunization has decreased the number of viral infections
Specific Diseases
• Measles, Mumps, Rubella, and Varicella– Young children are immunized against these
with one vaccine (MMRV)
• Smallpox– No longer found in the U.S. due to
successful vaccination
Specific Diseases
• Influenza A– Causes wide-spread respiratory disease
yearly
• Mononucleosis– Epstein-Barr Virus
Specific Diseases
• Herpes Simplex– Type I—mostly oral lesions “cold sores”– Type II—genital lesions
• Human Papillomavirus– Some strains associated with the
development of cervical cancer
Specific Diseases
• Cytomegalovirus
• Human Immunodeficiency Virus– Causes AIDS
• Rickettsial Infections
Specific Diseases
• Protozoal Disease– Malaria– Toxoplasmosis– Cryptosporidiosis
• Helminthic Infections– Various “worms”– Trichinosis