INFECTION AND IMMUNITY Flashcards
entrance and multiplication of a microorganism in or on a host
INFECTION
an infection w/ functional and structural harm to the host that is usually accompanied by signs and symptoms
INFECTIOUS DISEASE
presence and multiplication of new microorganisms that may cause an infectious disease or eliminated by host defense
COLONIZATION
a microbe capable of causing a disease
PATHOGEN
study of the structural and functional manifestations of a disease
PATHOLOGY
a physician specializing in pathology
PATHOLOGIST
the ability to cause a disease by overcoming host’s defenses
PATHOGENICITY
- steps or mechanisms involved in the development of a disease; disease process
PATHOGENESIS
- degree of pathogenicity •Quantitative measure of pathogenicity • Measured by the number of organisms required to cause disease •50% of lethal dose (LD50) •50% of infectious dose (ID50)
Virulence
number of organisms needed to kill half of the hosts/population
50% of lethal dose (LD50)
number of organisms needed to cause infection in half the hosts/population.
EX. -ID of Shigella is less than 100
- ID of Salmonella is about 100,000
50% of infectious dose (ID50)
study of the cause/s of disease
Etiology
environment or place of origin of the infecting agent
Reservoir
• Acquired in the HOSPITAL or other health care settings
• Causative agent is not present and not incubating in the patient on entry or admission into the health care facility
Examples: UTIs, Surgical wound infections; LRT infections, bacteremia
NOSOCOMIAL INFECTION
Staphylococcus aureus Escherichia coli Enterococcus faecalis Pseudomonas aeruginosa Most of these nosocomial pathogens are resistant to multiple antibiotics!
Bacteria most often associated w/ Nosocomial Infections
- Causative agent is present or incubating at the time of admission into the health care facility
- Ascariasis
COMMUNITY-ACQUIRED INFECTION
Results from organisms that are part of the patient’s normal flora
ENDOGENOUS INFECTION
microorganisms (bacteria, parasites, viruses, fungi, PRIONS) capable of causing an infectious disease
PATHOGENS
has the ability to infect a host w/ a healthy immune system as well as those in immunosuppressed state. Bacillus anthracis
TRUE PATHOGEN
attacks a debilitated host but presents no danger to a healthy individual. Candida albicans
-Infections of the immunocompromised hosts that do not cause a disease in individuals w/ a
normal immune system
-In immunosuppressive conditions, the host’s immune system is unable to effectively battle those microorganisms considered to be normal flora for the general population
OPPORTUNISTIC PATHOGEN
Opportunistic infections are increasing due to:
- Widespread use of broad-spectrum antibiotics that can alter normal flora
- Increased use of immunosuppressive drugs (in organ transplantation)
- Chemotherapeutic agents (cancer)
- Increased and prolonged use of urethral catheters
Individuals at risk for Opportunistic Pathogens include:
- Dialysis patients, Individuals on heart pumps
- Diabetics, burn victims
- Those w/ chronic medical problems; those undergoing invasive medical procedures
- Those w/ foreign body implants (heart valves, prosthetic devices, IV catheters)
- Alcoholics and IV drug users
Microorganisms normally residing in a particular body site; they do not usually cause an infection; also known as usual or indigenous flora
NORMAL FLORA
2 TYPES OF NORMAL FLORA
- Resident microbial flora
* Transient flora
colonize an anatomical area for months or years
• Resident microbial flora
– temporarily present at an anatomical site
• Transient flora
Distribution of normal flora
- Skin, Mouth and oral cavity, nasopharynx
- Stomach and upper small intestine, colon
- Urethra
There are anatomical sites considered to be STERILE (no normal flora):
- BLOOD,
- CEREBROSPINAL FLUID and
- URINARY BLADDER
Normal flora can become pathogenic if they are moved to another site. Examples
- E. coli of the colon (normal flora of the colon) is an important cause of UTI
- Viridans streptococcus of the mouth (normal flora of oral cavity) is a significant cause of bacterial endocarditis when established in the heart
The slightly acidic pH (5.5-6.0) results from the presence of acids produced by its normal flora:
SKIN
Common NF of skin:
- Staphylococcus spp.
- Propionibacterium acnes
- Micrococcus
- Candida
- Clostridium
- Diphtheroids
Less Common NF of skin:
- Streptococcus
- Enterococcus
- Acinetobacter
- Bacteroides
- Moraxella
- Gram negative rods
MOUTH & ORAL CAVITY
- Viridans streptococcus
- Staphylococcus epidermidis
- Neisseria (non-pathogenic spp.)
- Moraxella catarrhalis
- Lactobacilli
- Diphtheroids
Anaerobic NF include:
- Actinomyces
- Veilonella
- Bacteroides
-May serve as a site of asymptomatic carriage of several microorganisms
NASOPHARYNX
Common NF NASOPHARYNX
- Staphylococcus aureus
- Staphylococcus epidermidis
- Diphtheroids
- Haemophilus parainfluenzae
- Streptococcus
Less Common NF NASOPHARYNX
- Streptococcus pneumoniae
- Moraxella catarrhalis
- Haemophilus influenzae
- Neisseria meningitidis
- Other Moraxella spp.
Asymptomatic carriers maintain a reservoir for the organism but do NOT have an infectious disease BUT serve as an infectious source for others
- Staphylococcus aureus
* Neisseria meningitidis
-Are usually sterile containing less than 1000 organisms/ml
-Organisms entering the stomach are usually killed by HCl and gastric enzymes
-When organisms are passed in the small intestine, they may be destroyed by bile and pancreatic enzymes
-When the gastric pH increases to over 5.0, colonization from bacteria of oral, nasopharyngeal, or colon may occur
• Lactobacilli
• Bifidobacteria
STOMACH & UPPER SMALL INTESTINE
-Heavily colonized and serves as a reservoir for infection for numerous body sites, including the urinary tract and peritoneal cavity
COLON
Normal flora of Colon
- Bacteroides
- Lactobacillus
- Clostridium
- Eubacterium
- Coliforms such as Escherichia coli
- Aerobic and anaerobic streptococci
- Yeast
Normal flora of the distal urethra in both males and females may contain
- Diphtheroids
- Streptococci (alpha and non-hemolytic)
- Peptococcus
- Staphylococcus epidermidis
- Bacteroides
NF of the GUT
- Lactobacillus spp.
- Bacteroides spp.
- Clostridium spp.
- Peptostreptococcus
- S. aureus
- S. epidermidis
-Environment or the place of origin of an infecting agent is referred to
ROUTES OF INFECTION
Reservoirs:
- Humans, Animals
* Water, food, air, soil
when the host directly contacts the microbial reservoir or
DIRECT
when the host encounters the microorganism by an intervening agent
INDIRECT
The intervening agent can be a:
- Vector
* Vehicle/Fomite
living entity
Vector
non-living entity
Vehicle/Fomite
DIRECT TRANSMISSION
- Congenital contact
- Sexual contact
- Hand-to-hand contact
- Droplet infection
- May occur across the placenta or during passage at the birth canal
- Rubella virus and Treponema pallidum may be acquired during pregnancy
- Streptocccus agalactiae and Neisseria gonorrhoeae are examples of bacteria that may be transmitted to the infant during delivery
CONGENITAL/ VERTICAL
TRANSMISSION
- Serves as a route for many respiratory viruses and bacterial pathogens including:
- Streptococcus pyogenes
- Neisseria meningitidis
- Infectious secretions may come from coughing, sneezing, kissing and nasal drainage
- Respiratory secretions can become dried on clothing, bedding, or floors and converted to dust, which may serve as a route of indirect transmission
DROPLET INFECTION
Route of infection for many sexually transmitted infections (STIs)
Examples: Gonorrhea, SyphilisChlamydia, HIV InfectionHerpes, Hepatitis B infection
SEXUAL CONTACT
-Mode of direct contact seen w/ the
• spread of common cold due to rhinovirus
• transmission of GI infections (poor hand-washing, fecally contaminated hands)
HAND-TO-HAND CONTACT
- Fomites
- Ingestion of contaminated food and water
- Airborne routes
- Animal or arthropod vectors
INDIRECT TRANSMISSION
- Inanimate objects such as eating utensils, medical instruments, clothing, money, doorknobs, etc.
- Frequent routes of nosocomial infections
FOMITES
-Result of improper or poor sanitary measures
-Associated microorganisms include:
• Salmonella
• Shigella
• Escherichia coli
• Hepatitis A virus
CONTAMINATED FOOD & WATER
-Infections may be incidentally transmitted to humans through infected animals or insect (arthropod vectors) Examples:
• Rabies, Pasteurellosis, Tularemia
• Malaria, Lyme disease, Dengue fever
VECTORS
-Inhalation of infectious particles (aerosols) suspended in air. Examples:
• Tuberculosis
• Coccidioidomycosis
AIRBORNE
• High-grade, spiking fever
- Chills
- Vasodilation w/ flushing
- Increased pulse rate
Acute infection
- Intermittent, low-grade fever
- Weight loss
- Fatigue
Chronic or subacute infection