Pathology: infectious disease

Question 0

Sources of infection (general)

Answer 0

Viruses - a pathogen made of nucleic acid inside a protein shell
Bacteria - a unicellular organism without a true nucleus or organelles
Protozoa - a unicellular, animal-like microorganism, not usually harmful to humans
Fungi - yeasts and molds
Helminthes - worms
Mycobacteria - type of bacteria with fungal-like properties
Prions -small proteinaceous infectious particle

Question 1

Infectious diseases (general)

Answer 1

infection: disease caused by microorganisms, especially those that release toxins or invade body tissues
- infection differs from colonization of the body by micro-organisims in that during colonization, microbes reside harmlessly in the body or perform useful functions
- in contrast, infectious illness typically cause harm, hospital admission and death (intoxication is defined as poisoning by a drug or toxic substance)

Question 2

Clinical manifestation of infectious disease (general)

Answer 2

Fever, chills, malaise, enlarged lymph nodes
Integumentary - pus, open wound, rash red streaks, bleeding
Cardiovascular - tachycardia, hypotension, change in pulse rate
CNS- altered level of consciousness, confusions, convulsions, headache, memory loss, photophobia, stiff neck,
GI-nausea, vomiting, diarrhea
GU (genital urinary) - dysuria, flank pain, hematuria, oliguria, urgency, frequency, nocturia (need to pee at night)
Respiratory - tachypnea, cough, dyspnea, hoarseness, sore throat, nasal drainage, decreased exercise tolerance

Question 3

Classification of infection (general)

Answer 3

Endogenous - from within, a microorganism that was previously not pathogenic is now pathogenic. E.g. yeast
Exogenous - not from within, from a source outside the body e.g. influenza virus
Nosocomial - acquired in a health care setting e.g. staphylococcus

Question 4

Transmission from the source (general)

Answer 4

• For infection to be transmitted, the invading organism must be transported from the infected source to a susceptible host
  Portal of exit from the host include feces, urine, vomit, tears, semen, open lesions, blood

Question 5

Transmission of infection pathways (general)

Answer 5

Microorganisms are transmitted by several possible routes
Contact - direct or indirect
Airborne - float on air currents and remain suspended for hours, small particles.
Droplet - fall out within 3 ft of source, large particles
Vehicle - through a common source such as food or water
Vector - carried by an intermediate source, usually an insect

Question 6

Transmission of infection pathogen entrance (general)

Answer 6

ingestion
Inhalation
bites
contact with mucosa
transplacentally 
injections
Skin to skin contact
contact with blood or bodily fluids
contact with contaminated articles

Infectious diseases vary as to the number or organisms and the duration of exposure required to start the infectious process in a new host (pathogenicity)

Question 7

Susceptibility (general)

Answer 7

Can vary from person to person and depend on many factors including 
Age
Nutritional status
Hormonal balance
Concurrent disease
Drug use
Hygiene

Question 8

Chain of transmission (general)

Answer 8

Pathogen or agent: virus, mycobacteria, bacteria, fungi, prions
Reservoir human
Portal of exit: GU, GI, oral cavity, open lesion, semen, tears, blood, feces, urine
Transmission: contact (direct or indirect) airborne, droplet, vehicle, vector
Modes of entry: ingestion, inhalation, injection, transplacental
Susceptible host

Question 9

Defense of infection (general)

Answer 9

1. First line - mechanical barriers
2. Second line - inflammation
3. Third line - acquired immune response

Question 10

First line of Defence

Answer 10

Intact skin and mucous membranes
Oil and perspiration of skin
Cilia in respiratory tracts
Gag and coughing reflexes
Peristalsis in the GI tract
Flushing action of tears, saliva and mucus
The presence of normal flora

Question 11

2nd and 3rd line of defence

Answer 11

2nd - inflammatory  process
3rd - immune process
Include 
Lymphatic system
Leukocytes
Chemical proteins, enzymes

Question 12

Defence mechanism of infection (general)

Answer 12

relies on mechanical integrity of epithelial surfaces as well as decontamination - removal of the pathogen

Question 13

pattern of infections (general)

Answer 13

the invasive organism products local damage (e.g. warts)
The invasive organism is toxic (poisonous) to the host (e.g.botulism)
The invasive organism produces little local damage but has widespread effects (e.g. HIV)

Question 14

Spread of infection within a host (general)

Answer 14

Directly - some pathogens produce enzymes that damage cell membranes, enabling them to move rapidly from cell to cell

Via natural channels such as membranes (meninges, pleura, peritoneum) and vessels (lymphatic, blood)

Through nerves or through phagocytes (e.g. herpes virus)

Question 15

Mode of action (general)

Answer 15

Mode of action of a pathogen refers to how the organism produces a pathologic process. Great variation exists. Some intracellular pathogens, like viruses, invade cells and interfere with cellular metabolism, growth and replication. Other organisms cause cell death.

Question 16

Factors affecting occurrence and spread of infection (general)

Answer 16

pathogenic factors

Host factors

Question 17

Pathogen factors of infection (general)

Answer 17

virulence - the relative power and degree of pathogenicity
Dose - increased numbers are more effective
site of infection - some sites are more easily infected
Synergism between different pathogens (i.e. one organism can impair external defenses and permit another to enter)

Question 18

Host factors (general)

Answer 18

Resistance to infection
Immune competency
Leukocyte count
Necrosis and ischemia of a tissue (e.g. anaerobic bacteria)

Question 19

Diagnosis of infection (general)

Answer 19

1. Direct visualization of organism
2. Detection of microbial antigen
3. Search for clues produced by the host immune response to specific micro-organisms
4. Isolation of organism in culture
5. Detection of specific microbial nucleotide sequences

Question 20

Opportunistic infections (general)

Answer 20

• an opportunistic infection is any infection that results from a defective immune system that cannot defend against pathogens normally found in the environment. these infections are usually seen in patients with impaired defenses against disease.
• Life threatening infectious disease occurs when immunity is weak or suppressed (e.g. transplant patients, AIDS patients, old age, new borns, malnourished, burn victims, etc)

Question 21

Bacterial infections

Answer 21

Staphylococci (cocci means round, ball)
Streptococci
Pneumococci
Meningococci

Question 22

Staphylococcal infections

Answer 22

Reference: Goodman page 316
“Staph”
Among the most common bacteria normally residing on the skin
over 30 subtypes
Cause a multitude of disease ranging from mild/asymptomatic to severe/fatal
Leading cause of nosocomial and community acquired infections
Most common - staphylococcus aureus (S.aureus)

Question 23

S. aureus

Answer 23

Staphylococcal aureus
Extremely virulent (powerful)
Nonmotile (doesn’t move) and anaerobic
Hardy, able to survive on inanimate objects for an extended period
Can infect the blood, skin, lungs, soft tissue, joints, bones

Question 24

S. aureus risk factors

Answer 24

``` Staphylococcal aureus Diabetes, chronic illness HIV positive Elderly, newborns, malnourished Surgical/burn patients prosthetics ```

Question 25

S. aureus causes infectious diseases include

Answer 25

``` Staphylococcus causes: Osteomyelitis Respiratory tract infections Infectious arthritis Septicemia Endocarditis Toxic shock syndrome Food poisoning Skin infections (cellulitis, mastitis) ```

Question 26

Management of infections of Staphylococcus aureus

Answer 26

Diagnosis - culture Treatment - antibiotics Prognosis is generally good although some strains of S. aureus are particularly difficult to treat E.g. MRSA (Methicillin-resistant staphylococcus aureus, resistant to antibiotic) Also antibiotic resistant strains are increasing

Question 27

Streptococcal infections

Answer 27

Reference: goodman page 319 Include: Group A - Streptococcus pyogenes (s.pyogenes) Group B - S. agalactiae

Question 28

S. pyogenes

Answer 28

Streptococcal pyogenes One of the most common bacterial pathogens of human or any age Causes many diverse disease of many diverse organs and systems Can cause suppurative (pus making) and non-suppurative disease Transmission - contact, droplets, foodborne

Question 29

S. pyogenes causes

Answer 29

Streptococcal pyogenes causes Streptococcal pharyngitis (strep throat) very common cause of sore throat occurring mostly in children Scarlet fever - usually follows untreated strep throat and but more severe Impetigo - skin infection that occurs in children, particularly in hot weather Cellulitis - acute skin infection Necrotizing fasciitis - very serious and potentially fatal infection that spreads quickly along fascial planes

Question 30

S. agalactiae

Answer 30

Streptococcal agalactiae Leading cause of neonatal pneumonia (vaginal, not common in adults), meningitis, sepsis Infrequent cause of pyogenic (containing pus) disease in adults Rapid administration of antibiotics is essential Pregnant women are routinely screened

Question 31

Pneumococcal infections

Answer 31

Pneumococcus or streptococcus pneumonia (S. pneumonia) Can cause pneumonia, sepsis, otitis media, meningitis Most common cause of community acquired pneumonia Very young and very old particularly susceptible

Question 32

Pneumococcus risk factors

Answer 32

Often follows influenza, viral respiratory infections Risk factors include chronic disease and alcohol abuse, immunosuppression, etc Most common cause of "bacterial" meningitis in adults, infants and toddlers

Question 33

Meningococcal infections

Answer 33

Meningococci cause meningitis and septicemia Symptoms are usually severe and can include headache, nausea, vomiting, photophobia, lethargy, rash, multiple organ failure, shock, and disseminated intravascular coagulation (DIC)

Question 34

Anaerobic bacterial infections

Answer 34

Anaerobic bacteria are intolerant of oxygen, replicating at sites of potentially low oxygen such as necrotic, devascularized tissues. These infections are usually suppurative, causing abscess formation and tissue necrosis

Question 35

Anaerobic infections cause

Answer 35

Diphtheria Plague (www.merck.com/mmpe) Botulism (www.merck.com/mmpe) Cholera

Question 36

Diphtheria

Answer 36

An acute pharyngeal or cutaneous infection caused by Corynebacterium diphtheria (C. diphteria) Children are routinely vaccinated The disease spreads by contact and secretions of nose, mouth and skin lesions

Question 37

Diphtheria Symptoms

Answer 37

Symptoms include nonspecific skin infections (inflammation and necrosis of local tissues) or pseudomembranous pharyngitis followed by myocardial and neural tissue (heart, nerve, kidney) damage Tx. antibiotics, prognosis good

Question 38

Plague

Answer 38

Aka Bubonic plague or Black Death Caused by Yersinia pestis (Y. pestis) Symptoms are either severe pneumonia or massive lymphadenopathy with high fever often progressing to septicemia Enlarged lymph nodes called buboes

Question 39

Plague transmission

Answer 39

Wild rodents carry disease Transmitted from rodents to human by the bite of a flea vector Human to human transmission occurs by inhaling droplets from infected humans Highly contagious Massive human pandemics rare today due to antibiotics

Question 40

Botulism

Answer 40

Neuromuscular poisoning caused by Clostridium botulinum Botulism can be food-borne or wound-borne Most frequently manifests as a severe form of food poisoning Common sources include home-canned foods, vegetable, fish, fruits, condiments, meat, dairy

Question 41

Botulism Etiology and symptoms

Answer 41

Bacteria produces toxin that can interfere with release of acetylcholine at peripheral nerve endings (NMJ) Symptoms include nausea, vomiting, abdominal cramps and diarrhea followed by weakness and paralysis Spores are common in the environment Although the spores are heat resistant, cooking kills the toxins A spore is a cell produced by spore-forming bacteria (bacillus) to withstand extreme conditions It can remain viable for decades

Question 42

Cholera

Answer 42

Acute infection of the small bowel by Vibrio cholerae Secretes a toxin that produces copious watery diarrhea Leads to dehydration, oliguria, and collapse (shock) Infection is typically through water or seafood that is contaminated with the excrement of infected people Treatment - rehydration with water and electrolytes; antibiotics

Question 43

Spirochete infections

Answer 43

A spirochete is a slender, spiral motile bacteria that lives off dead and decaying matter in soil and water E.g. Lyme disease, syphillis

Question 44

Lyme disease

Answer 44

An infectious multi-systemic disorder Caused by Borrelia burgdorferi Vector-borne disease carried by a deer tick Ticks carrying the bacteria can transmit to mammals by injecting saliva into the host Symptoms include skin lesions and a "bull's eye" rash (erythema migrans). The bacteria reach other organs through the blood and cause nausea, vomiting, neurological and arthritis-like symptoms This disease is very common in the spring and summer in the Pacific Northwest and is the most common tick-borne disease in the states. Treatment- antibiotics

Question 45

a pathogen made of nucleic acid inside a protein shell

Answer 45

Virus

Question 46

A unicellular organism without a true nucleus or organelles

Answer 46

Bacteria

Question 47

A unicellular, animal like microorganism, not usually harmful to humans

Answer 47

Protozoa

Question 48

yeasts and molds

Answer 48

Fungi

Question 49

Worms

Answer 49

Helminthes

Question 50

A type of bacteria with fungal-like properties

Answer 50

Mycobacteria

Question 51

A small proteinaceous infectious particle

Answer 51

Prions