Principles of Infection
Can be bacterial
Lyme disease: tick bites Rocky Mountain spotted fever: tick bites Typhus: lice bites Bubonic plaque: flea bites
Can be Protozoan
Malaria: bite of Anopheles mosquito Toxoplasmosis: ingestion of contaminated meat, inhalation of pathogen, and direct contact
Candida infections such as those seen in vaginal yeast infections in women after prolonged antibiotic therapy are due to which scenario?
Mutations, or changes, of normal flora
Neisseria gonorrhoeae
N-Methylphenyl-alanine pili, Gonorrhea
Organism
Adhesion factor, disease
Increased Microbial Virulence
Adhesion:presence of bacterial capsule and pili Colonization: spore formation, reproduction/replication of microbes Invasion: entry of large number of organisms into body Evasion of host defenses: viral mutation and replication Toxogenesis: production of exotoxins, endotoxins, and destructive enzymes
Direct contact
Human:touching, kissing, sexual intercourse, fecal-oral route (poor hygeine) Zoonoses: touching, biting, scratching
Which statement best explains the transmission of infectious disease from one host to another?
a chain of events leading with the reservoir and ending in the susceptible host occurs via different modalities
symbiosis
a close relationship between two different types of organisms that live together in a community: mutualism, commensalism, parasitism, or amensalism
immunocompromised system
any factors that suppress or weaken the immune system can enable opportunistic pathogens to cause infections and disease: acute and chronic diseases, malnutrition, stress, age, radiation and chemotherapy, immunosuppressive drugs
hyaluronidase
attacks connective tissue structure through breaking down hyaluronic acid
Electrostatic attraction
attractive or repulsive interaction between organisms with an electric charge; adhesion increases through attraction
Infectants survive by
avoiding contact with cells defenses, inhibiting engulfment by phagocytes, surviving inside phagocytes, producing toxins to damage defenses
Which is a method of transmitting pathogens from one host to another by carrying microorganisms inside the body and hosting their survival until transmission has occurred?
biologic vector
fleas
bubonic plague, endemic typhus
Transient flora
can be found in the same locations as the resident flora but only for a few hours, days, or months Bacillus latersorus-found in the intestines-regulate fungal populations streptococcal pneumoniae-can be seen on the skin
oppurtunistic pathogens
capable of causing infection and disease in vulnerable population
endotoxins (lipopolysaccharides)
carry their toxicity on the lipid tail of the chain, released when bacteria is damaged or destroyed
houseflies, face-flies, blow-flies
cause foodborne illness, dysentery, intestinal worms
cockroaches
cause foodborne illness, typhoid fever, viral diseases, human enteric protozoa
dung beetles
cause toxoplama gondii (toxoplasmosis)
Streptococcus pneumoniae
cell-bound protein, pneumonia
blood-sucking bugs
chagus disease
A 37-year-old diabetic patient who has recently lost his job has now been diagnosed with Epstein-Barr virus. Which could be the reason why his resistance is decreased to allow for invasion of the virus?
chronic disease, severe emotional stress
Which form of symbiosis is beneficial to one organism and neither harms nor benefits the other?
commensalism
Droplet transmission infections
common cold, influenza, pneumonia, pertussis
phospholipsases
destroys phospholipids of the plasma membrane
host resistance
determinant on the health of the individual and is a primary factor in determining risk of infection after exposure as seen in some infections
zoonoses
diseases that are primarily seen in animal but can be transmitted to humans by; contact with infected animal or animal waste, dust from contaminated hides, fur, feathers, ingestion of infected animal products, or insect vectors
Which is the most effective mode of transmission that is responsible for the spread of the common cold and influenza?
droplet transmission
lice
epidemic typhus
invasion
extracellular proteins or enzymes that have the ability to damage or destroy host cells they disrupt the host cell membrane and break down primary and secondary defense barriers facilitating growth and proliferation of the pathogen
Which are considered specific adhesion virulence factors?
fimbriae, cell-bound proteins
Bordetella pertussis
fimbriae, whooping cough
Which are considered vehicles for transmission of diseases that affect the gastrointestinal tract?
foodborne, waterborne
Non-Specific Adhesion
forces or interactions the microorganism uses to move toward the eukaryotic host include:
Reasons for nosocomial infections
happens to 10-15% of patients in hospital setting, reasons: presence of varying types of microorganisms, patients considered to be "contagious", overcrowding, use of contaminated instruments, immunocompromised and weakened patients, chain of transmission through staff, diagnostic procedures and equipment, therapeutic aids, and food trays, growing number of micropes resistant to multiple drugs
toxins
have the ability to cause sepsis, necrosis, and cell death
Which are examples of invasins that work to disrupt the host cell membrane?
hemolysin, stretolysin, hyaluronidase
hydrophobic interactions(water repelling)
increases propensity of adhesion; the more hydrophobic, the stronger the surface is to adhesion
A co-worker cannot determine how she contracted MRSA. The only thing she can think of is washing her son's wrestling uniform and towels after his practice. Which is the most likely mode of transmission?
indirect contact
Staphylococcus aureus (MRSA)
infections that are difficult to treat due to growing resistance to multiple antibiotic medications
Transmission
infectious organisms from one individual to another: reservoir has no obvious active infection in the acute stage or is asymptomatic, infectious agent is transferred directly or indirectly
Host resistance examples
intact skin and mucous membrane, body secretions--stomach acid, tears, nonspecific phagocytosis, effective inflammatory response, absence of disease, interferon production(virus)
Which is a group of signaling proteins produced by human host cells in an effort to boost immunity during a pathogenic invasion?
interferons
C. difficile
interrupts the distribution of normal flora allowing the bacteria to multiply causing severe diarrhea and ultimately death in some cases
Foodborne transmission
involves pathogens in or on foods that are improperly prepared: can occur due to parasitic worms, viruses hep A are also transmitted this way
Airborne Transmission
involves the spread of pathogens by droplet nuclei, and dust from reservoir to host: aerosols-coughing, sneezing, air conditioner, other cooling systems, pathogens attached to dust particles being stirred when cleaning
vectors
living organisms that carry disease in or on their bodies for transmission from one host to another
ticks
lyme disease, Rocky Mountain spotted fever
mosquitoes
malaria, yellow fever, elephantiasis, dengue, viral encephalitis, west nile virus
Which are considered factors that decrease host resistance?
malnutrition, immune senescene, severe emotional stress
Which concept describes how normal flora acts to protect the body against pathogens, because it occupies the same space, utilizes the same nutrients, and releases toxic waste products?
microbial antagonism
Recruitment and trapping by biofilms
microbial biofilms are complex bacterial communities often seen on implanted medical devices; they attract or recruit organisms for proliferation by altering the texture of the surface to meet the needs of the pathogen
Adhesion
most crucial virulence factor: bacterial occurs via pili, fimbriae, or specific membrane receptor sites----Viral occurs by using capsid or envelope proteins
colonization is caused by
motility ability as well as other means of contact with the host cell, adherence capability to host cell with resistance to physical removal, ability to invade the host cell and survive, ability to compete for iron and nutrients
Which factors affect pathogens' ability to colonize?
motility, adherence, ability to invade
chemotaxis
movement toward or away from a chemical stimulus
microbiota
normal flora intended to be there and are mostly beneficial to the body
Hospital-acquired infections (HAIs) or nosocomial infections
occur in health care facilities and are direct contact
Bodily Fluid Transmission
occur when contaminated bodily fluids are handled (mostly in health care setting): blood, urine, saliva
waterborne transmission
occurs due to untreated or poorly treated sewage: GI diseases--giardiases, amebic dysenter, cholera, shigellosis, leptospirosis, Fecal-oral infections--"Schistosoma" worms and enteroviruses
Colonization
occurs in human tissue that is exposed to the environment, such as the digestive, respiratory, and genitourinary tracts, as well as the conjunctiva of the eye
invasion into non-microbiota areas
often injury or displacement of normal flora into other areas of the body present vulnerability for opportunistic pathogens to cause infection or disease
Parasitism
one organism benefits and the other is harmed, either slightly or to such an extreme that the host is killed tuberculosis bacterium tapeworms
Which term describes an organism that causes disease or destruction of cells when the immune system is compromised?
opportunistic
Mechanical vectors
passively carry pathogens on their body (typically feet/legs) from one host to another
Which statement best explains why someone would be considered a germaphobe and not want to shake hands with others?
pathogens can be transmitted directly through handshaking
hemolysins
phospholipases destroy erythrocytes and other cells by lysis
E. coli, uropathogenic
pili, pyelonephritis
Brownian movement
random movement of microscopic particles suspended in a liquid or gas aids adhesion
Mutualism
relationship between two organisms in which both members benefit from the interaction Escherichia coli in human large intestine Probiotics
streptolysin
repels phagocytes while altering the membrane causing release of lysosomal granules
mites
scrub typhus
exotoxins
secreted by living bacteria act to damage cell membranes, inhibit protein synthesis, interfere with cell signaling, inhibit neurotransmitters, and alter immune response are secreted either directly through the cell membrane or with the help of an autotransporter
nonliving reservoirs
soil: provides optimal environment for survival and growth of pathogens such as fungi, helminths, and bacteria; due to fecal material can contain Clostridium botulinum, and C. tetani Water: can be contaminated with feces and urine may contain worm eggs, pathogenic protozoans, bacteria, and viruses Food: due to improper preparing and storing of foods
Which statement best defines virulence?
the ability of a microorganism to cause disease
pathogenicity
the ability of a microorganism to cause disease directly related to the number of infecting organisms, the portal of entry, host resistance, and the intrinsic characteristics along with their virulence factors
antigenicity
the ability to cause the production of antibodies
An older adult has recently been discharged from the hospital and has developed pneumonia, which has been attributed to her stay as an inpatient. Which statement would explain this?
the infection is a hospital-acquired infection
An article reads "tetanus due to injury involving soil infected with Clostridium tetani." Which statement about transmission of this pathogen can be considered to be true?
the pathogen was residing in a non-living reservoir
"case fatality rate"
the proportion of deaths in designated population of cases
human carriers
there are obvious infectious diseases that are easily identified and precaustions are put in place others are simply carriers and are asymptomatic but never become sick infect others without knowing they carry an infectious disease because they are immune to it
Atomic and molecular vibrations
this creates a force of attraction for pathogens
Indirect Contact
tissues and handkerchiefs, towels and linens, wrestling mats, toys, clothes, diapers, money, eating utensils and drinkware, medical equipment and devices, contaminated needles (HIV, Hep B and C)
Which type of virulence factor is secreted by living bacteria and acts to damage cell membranes and prevent protein synthesis?
toxin
Which are accurate statements regarding toxogenic virulence factors?
toxins can be secreted either directly or through the cell membrane, endotoxins carry toxicity on a lipid tail released when bacteria is damaged
An individual is experiencing issues related to a candida infection. Which describes the bacteria Bacillus laterosporus that can be given to this person to regulate the fungal population?
transient flora
Biological vectors
transmit pathogens but also serve as a host for part of the pathogens life cycle
common nosocomial infections include
urinary tract infections(most common), pneumonia, diarrhea, surgical wound infection
biologic therapy
used in cancer treatment the immune system is stimulated by interferons
Which are the correct modes of transmission for airborne, foodborne, and waterborne transmission?
vehicle
Droplet transmission
when infectious agents are transmitted through respiratory droplets released into the air traveling less than 1 meter: normal exhaling, laughing, coughing, sneezing (most common)
fomites
an inanimate object that came in contact with a pathogen that then infected a person/animal
Amensalism
an interaction between two species in which one organism can hamper to prevent the growth and/or survival of another, without being positively or negatively affected by the other organism penicillium
Which are considered reservoirs for zoonoses?
animals
Foodborne transmitted infections
Cholera: transmitted via ingestion of contaminated water, raw or partially cooked fish, or shellfish Gastroenteritis(Norwalk virus): transmits via ingestion of contaminated seafood and handling of contaminated food Salmonella: transmits via contaminated poultry, eggs, and meat
Specific water-borne infections
E. Coli: transmit via uncooked meat, food contaminated by fecal material; swimming in contaminated water Hepatitis A: transmit via contaminated food, water contaminated with human feces Samonellosis: transmit via contaminated poultry, eggs, and meat; fecal-oral route
Streptococcus mutans
Glycosyltransferase, Dental caries
Bodily Fluid transmitted infections
HIV/AIDS, hepatitis, and herpes
Treponema pallidum
Peptide in outer membrane, syphilis
Streptococcus pyogenes
Protein F, sore throat
These can be viral
Rabies:direct contact, bite, scratch Hantavirus pulmonary syndrome: inhalation of viruses from dried feces and urine or direct contact with rodent saliva, feces, or urine yellow fever: bite of Aedes mosquito
Can be Fungal
Ringworm: direct contact
Can be helminthic
Tapeworm infestation: ingestion of larvae transmitted in dog saliva Trichinellosis: ingestion of undercooked contaminated pork meat
interferons
a group of signaling proteins produced by human host cells in an effort to boost immunity in response to pathogenic invasion
specific adhesion
a lock-and-key interaction between complementary molecules on each cell surface is permanent and irreversible
reservoir
a place for a causative agent of infection to survive, can be animal, human, or nonliving agent
resident flora
a resident flora lives symbiotically in the body throughout the life of a person Staphylococcus epidermidis-resident of the skin E.coli--resident intestinal flora
Commensalism
a term used for a symbiotic relationship in which one of the organisms benefits and the other is neither harmed nor helped Saprophytic and mycobacteria Staphylococcus aureus
changes in normal flora
act to protect the body against pathogens as it occupies the same space, utilizes the same nutrients, and releases toxic waste products in "microbial antagonism": mutation of normal flora, hormonal changes, stress, changes in the diet, exposure to an excessive number of pathogenic organsims
Also relates to the ability of the microorganism to
adhere to host cells or tissues, colonize host cells, invade host cells, evade host defenses, produce toxins
Bordetella pertussis uses fimbriae in which type of virulence factor?
adhesion
Which virulence factor involves hydrophobic interactions and atomic and molecular vibrations?
adhesion
blood-sucking flies
african sleeping sickness, river blindness
Factors decrease host resistance
age, genetic susceptibility, immunodeficiency of any type, malnutrition, chronic disease, stress, compromised skin integrity, impaired inflammatory response, severe or multiple infections
Direct contact infections
agents causing respiratory tract infections, staphylococcal infections, measles, scarlet fever, sexually transmitted diseases