CHAPTER 16 Infection, Protective Mechanisms, and Asepsis

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CHAPTER 16 Infection, Protective Mechanisms, and
Asepsis
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Infection

• Infection entry of an infectious agent into the
  body a microorganism
• The agent multiplies and causes tissue damage.
• Some microorganisms produce toxins.
• Microorganisms are classified by morphology
  (shape).
• Infection may result in illness and disease.
• Microorganisms capable of causing disease are
  called pathogens.
• Mircroorganisms may be aerobic or anaerobic.

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Organisms Causing Pathology

• Bacteria
• Prions
• Viruses
• Protozoa
• Rickettsias
• Fungi
• Helminths
• Othersmycoplasmas, Chlamydia

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Bacteria

• Bacteria are single-cell microorganisms with no
  nucleus.
• They reproduce approximately every 20 minutes.
• They are classified according to shape and Gram
  staining.
• Those retaining stain on slides are
  gram-positive.
• Those taking up a counterstain are gram-negative
• Many gram-negative bacteria produce endotoxins.

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Bacterial Morphology

• Cocci are bacteria that are round, such as
  streptococci (grow in chains)
• Round bacteria that occur in pairs are called
  diplococci.
• Round bacteria in clusters are called
  staphylococci.
• Spiral or corkscrew-shaped bacteria are called
  spirochetes.
• Rod-shaped bacteria are called bacilli.

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Bacteria

• Aerobic bacteria need oxygen to grow.
• Anaerobic bacteria can grow only when oxygen is
  not present
• Bacteria are identified by chemical testing and
  growing cultures.
• Sensitivity testing determines which antibiotic
  can kill the organism.
• Some bacteria are drug resistant.

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Drug-Resistant Bacteria

• Currently, there are four agency-prevalent
  resistant organisms
• Aminoglycoside resistantPseudomonas
• Methicillin resistantStaphylococcus aureus
• Penicillin resistantNeisseria gonorrhoeae
• Vancomycin resistantEnterococcus species

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Prions

• Prions are protein particles that cause
  degenerative neurologic disease such as new
  variant Creutzfeldt-Jakob disease (mad cow
  disease).
• They lack nucleic acids and are not inactivated
  by the usual procedures to destroy viruses.
• They do not trigger an immune response.

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Viruses

• Extremely small, seen only with an electron
  microscope
• Composed of particles of nucleic acids, either
  DNA or RNA, with a protein coat
• Grow and replicate only within a living cell
  survival and replication depend on host tissue

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Protozoa

• Protozoa are one-cell microscopic organisms
  belonging to the animal kingdom.
• They include the Plasmodium species which causes
  malaria (Plasmodium malariae)
• Entamoeba histolytica causes amebic dysentery.

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Rickettsia

• Small round or rod-shaped organisms that are
  transmitted by the bites of fleas, lice, mites,
  and ticks
• Multiply only in host cells
• Cause Rocky Mountain spotted fever and typhus

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Fungi

• Tiny primitive organisms of the plant kingdom
  that contain no chlorophyll
• Includes yeast and mold
• Feed off living animals and decaying organic
  matter
• Reproduce by use of spores.
• Cause candidiasis and tinea pedis (athletes foot)

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Helminths

• Helminths are parasitic worms.
• Pin wormsmostly affect children
• Round worms
• Tapeworms
• Other infectious agents
• Mycoplasmas
• Chlamydia

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Process of Infection

• Causative agent (Link One)
• Reservoir (Link Two)
• Portal of exit (Link Three)
• Mode of transmission (Link Four)
• Portal of entry (Link Five)
• Susceptible host (Link Six)

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Portals of Entry of Selected Pathogenic Organisms

• Respiratory tract
• Neisseria meningitidis
• Mycobacterium tuberculosis
• Influenza A
• Streptococcus pneumoniae
• Measles virus
• Legionella pneumophilia
• Varicella-zoster virus
• (Contd)

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Portals of Entry of Selected Pathogenic Organisms

• (Contd)
• Gastrointestinal tract
• Salmonella enteritidis
• Salmonella typhi
• Clostridium botulinum
• Poliovirus
• Hepatitis A
• Escherichia coli
• (Contd)

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Portals of Entry of Selected Pathogenic Organisms

• (Contd)
• Genitourinary tract
• Neisseria gonorrhoeae
• Chlamydia trachomatis
• Enterobacteriaceae
• Intact skin or mucous membranes
• Rhinovirus
• Respiratory syncytial virus
• Schitstosoma sp.
• Herpes simplex virus
• (Contd)

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Portals of Entry of Selected Pathogenic Organisms

• (Contd)
• Blood stream
• Hepatitis B or C viruses
• Plasmodium sp.
• Clostridium tetani
• Human immunodeficiency virus (HIV)

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Susceptibility of the Elderly

• Factors placing the elderly at risk for infection
• Poor nutrition
• Immobility
• Poor hygiene
• Chronic illness
• Physiologic factors of aging such as thinner skin

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Body Defenses Against Infection

• Intact skin is the first line of defense against
  infection.
• Secretions (lysozyme) from mucous membranes
  lining the respiratory, gastrointestinal, and
  reproductive tracts
• Cilia in the respiratory tract
• Kupffers cells in the liver
• Gastric secretions

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Portals of Entry of Selected Pathogenic Organisms

• Fever
• Leukocytosis
• Phagocytosis
• Inflammation
• Interferon
• Immune response

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Types of Immunity

• Passive acquired immunityoccurs when a person is
  given an antitoxin or antiserum containing
  antibodies or antitoxins
• Naturally acquired passive immunityfetus
  receives antibodies from the mother
• Artificially acquired immunityimmunizations or
  vaccines
• Passive artificially acquired immunity injection
  of antibodies derived from serum of infected
  people or animals

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Asepsis

• Asepsisthe practice of making the environment
  and objects free of microorganisms
• Medical asepsisreducing the number of organisms
  present or reducing the risk of transmission of
  organisms prevents the spread of infection from
  person to person or reinfection of the same
  person
• (Contd)

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Asepsis

• (Contd)
• Surgical asepsispreparing and handling
  instruments and materials in a way that prevents
  the patients exposure to living microorganisms.
• Involves sterilization of all surgical
  instruments used in surgery and of supplies used
  to invade the body such as catheters or needles

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Control of Microorganisms

• Standard Precautions
• Handwashing (the most effective way to reduce
  microorganisms)
• Gloves, mask, eye protection
• Gown, patient care equipment
• Environmental control, linens
• Occupational health and blood-borne pathogens
• Patient placement

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Cleaning

• Pathogens can be killed or inactivated by
  disinfection, sterilization, or use of
  anti-infective drugs.
• Clean and remove debris in cold water.
• Wash and scrub in hot water use a
  stiff-bristled brush.
• Rinse with hot water dry.
• Object is now clean.

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Disinfection

• Used to eliminate some types of organisms after
  cleaning
• Uses compounds such as phenol, alcohol, or
  chlorine
• Recommended disinfectant 1 part chlorine bleach
  to 10 parts water
• Uses bacteriostatic or bactericidal agents

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Sterilization

• Best method for eliminating microorganisms
• Four methods
• Moist heat
• Gas
• Boiling water
• Radiation
• Asepsis in the home environment