Microorganisms: Infectious Disease Chapter 5 Quiz

Universal Precautions and Infection Control

• Universal precautions provide guidelines for infected fluids and waste
• Sterilization: killing all forms of life; autoclaving (steam under pressure) is very effective at sterilizing and killing endospores
• Disinfectants are used on non-living surfaces
• Glutaraldehyde is a very effective disinfectant and is considered a true sterilizing agent
• Antiseptics are used on living tissue (e.g. isopropyl alcohol is used on tissue before giving IV or injection and is also used in hand sanitizer)

Physiology of Infection

• Infectious agents can be present long before clinical signs or symptoms appear
• Incubation period: the time between exposure to an agent and the onset of symptoms (e.g. 14 days for measles and chickenpox)
• Prodromal period: early symptoms (e.g. fever, achy muscles)
• Acute stage: full-blown symptoms
• Period of convalescence: recovery and return to previous state of good health

Patterns of Infection

• Local: confined to one area (e.g. mosquito bite or pimple)
• Focal: once local, but spreads to surrounding areas
• Systemic: enters the bloodstream
• Septicemia: bacteria or other pathogens multiply in the bloodstream
• Bacteremia: bacteria in the blood
• Toxemia: toxins in the blood
• Fungemia: fungus in the blood
• Viremia: virus in the blood
• Mixed infection: more than one pathogen
• Acute infection: symptoms and signs appear quickly and are short-lived
• Chronic infection: symptoms and signs are slow to appear and last longer
• Primary infection: initial or first exposure
• Secondary infection: follows primary infection, usually with another organism (e.g. opportunistic infection)
• Subclinical infection: no apparent signs or symptoms, can persist for a long time, may be a carrier

Signs and Symptoms

• Signs: visible (e.g. fever, rash)
• Symptoms: only noticed by the patient (e.g. stomachache, pain)

Methods of Diagnosis

• Culture and stain organisms from blood or fluid sample
• Kirby-Bauer (antibiotic sensitivity) to determine if antibiotic will be effective
• MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration)
• Blood tests (e.g. leukocytosis, elevated WBC count; leukopenia, lowered WBC count)
• Neutrophils increase with acute infections, lymphocytes and monocytes increase with chronic infections
• C-reactive protein and erythrocyte sedimentation rate (ESR) are elevated in inflammation
• Rapid tests to identify Strep and MRSA
• Radiologic examination to assist diagnosis (e.g. lung congestion in one lobe indicates pneumococcal pneumonia)

Treatment and Antimicrobial Drugs

• Increasing use of antibiotics has led to increased resistance
• Take medicine as directed and complete the full course
• Antibiotics are not effective against viral infections, with few exceptions

Example of Infection: Influenza

• Viral infection that can affect upper and lower respiratory systems
• Can be complicated by secondary bacterial infections like pneumonia
• Mortality rate higher with secondary infection, especially in the elderly and those with chronic cardiovascular and respiratory diseases
• RNA viruses; classified into three groups: A, B, and C
• Mutate frequently, making it hard to find a vaccine that works consistently

Microorganisms

• Bacteria: prokaryotic (no true nucleus); pathogenic bacteria cause disease
• Viruses: obligate intracellular parasites; need a host to multiply; have a protein coat called a capsid
• Chlamydiae, Rickettsiae, and Mycoplasmas: replicate by binary fission, but require a host for reproduction
• Fungi: eukaryotic organisms that can cause infections (mycoses)
• Protozoa: more complex eukaryotic organisms that are usually parasites
• Helminths (worms): often seen in stool samples; can be spread through fecal-oral route

Normal Flora

• Normal colonies of bacteria found on and in the body
• Microbes like E. coli in the gut help provide vitamin K
• Normal flora helps keep pathogens away due to competition
• Resistant or normal flora help keep pathogens away due to competition

Principles of Infection

• Infection: microbe reproduces in host
• Infectious disease is not the same as genetic disease, geriatric disease, etc.
• Endemic disease occurs consistently in an area
• Epidemic: disease occurs outside normal area (spreads rapidly)
• Pandemic: disease spreads worldwide (e.g. flu, COVID-19)

Transmission of Infectious Agents

• Reservoir: harbors disease in environment (e.g. movie "Contagion" with flying fruit bat as reservoir)
• Carrier: harbors the disease (may or may not get sick)
• Subclinical: mild infection with few to no symptoms or signs
• Reservoir may be food, water, soil, animal, person
• Direct contact: touching; indirect contact: uses an intermediary like a door knob or tissue
• Droplet transmission: oral or respiratory droplets travel less than 1 meter from host
• Airborne transmission: droplets travel more than 1 meter
• Vector-borne: insect or animal is intermediary host (e.g. mosquito with malaria)

Handwashing Helps Prevent Spread of Infection

• Especially with direct and indirect contact
• Nosocomial infections are hospital-acquired
• Clostridium difficile (C-diff) infections are common in ICUs where patients are taking antibiotics
• MRSA is also becoming a problem in hospitals

Host Resistance

• Factors that decrease host resistance: age, genetic susceptibility, immunosuppression, malnutrition, chronic diseases, physical or emotional stress, inflammation or trauma
• Impaired inflammatory response
• Virulence and pathogenicity: ability to cause disease
• Mutation is a change in genetic composition of an organism

New Issues Affecting Infection

• Superbugs and emerging infectious diseases (EIDs) are monitored by the CDC and WHO
• CDC publishes MMWR (Morbidity and Mortality Weekly Report)
• Guidelines for healthcare facilities to manage, screen, and treat serious infections that may lead to a pandemic