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66 Cards in this Set
- Front
- Back
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What is a host?
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A living organism that harbors another living organism
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What are some examples of microorganisms?
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Bacteria, fungi, protozoa, viruses
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What are pathogens?
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Microorganisms that cause infectious disease
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What is bacteremia?
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When bacteria is present in the blood, but not actively dividing - can be transient
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What is a focal infection?
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An infection where a microorganism is limited to a certain location in the body while its byproducts (such as toxins) spread throughout the body
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What is an example of gram positive stain?
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Streptococcus
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What is an example of gram negative stain?
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Escherichia
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What is a secondary infection?
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When a primary infeciton lowers the host's resistance to infection and enables a secondary infection to occur
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What is toxemia?
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The presence of toxins in the blood but no microorganisms
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What are the five conditions for proper growth of microorganisms?
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- Moisture
- Temperature - pH - Oxygen supply - Nutrients |
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What are transient flora?
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Microorganisms that are found periodically on or in the body; not as well adapted to the human body as resident flora
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What are some ways to remove transient flora?
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- Excretion or secretion (perspiration, urine, feces, tears)
- Acidic or alkaline environment - Mechanical or chemical debridement - Inability to compete with resident flora |
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What are some examples of opportunistic pathogens?
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Escherichia coli, candida albicans
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What is a symbiont?
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An organism that lives closely together with another organism
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What is mutualism?
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Both organism and host benefit from the relationship
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What is commensalism?
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When an organism exists without rendering harm or benefit to the host
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What is virulence?
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The ability of a pathogen to cause disease (ie number of microorganisms or micrograms of toxin required to kill a host)
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What is an example of low and high virulence?
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Measles = low virulence
Rabies = high virulence |
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What is resistance?
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The host's body defenses against pathogens
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What are some risk factors for transmission of infection?
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Age, nutritional status, chronic illness, immunosuppression
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What are the five portals of entry?
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Ingestion, inhalation, contact with mucous membranes, percutaneously, transplacentally
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What is a reservoir?
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An area for which the pathogen can multiply in adequate numbers in order for it to infect another host
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What are some examples of reservoirs?
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Fomites, zoonoses, places
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What are some examples of zoonotic diseases?
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Rabies, lyme disease, malaria, cat-scratch disease
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What are the five modes of transmission?
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Contact, droplet, airborne, common vehicle, vector
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What is the chain of infection?
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Resevoir -> infectious agent -> susceptible host -> portal of entry -> mode of transmission -> portal of exit
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What is an endotoxin?
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A toxin that is released during cell lysis (usually with a gram negative bacterial infection)
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What are exotoxins?
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Proteins released outside of the bacteria during bacterial growth
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What are the four characteristics of a pathogen that effect its ability to cause disease?
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- Toxins
- Adhesion factors - Evasive factors - Invasive factors |
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What are the five stages of an infectious disease?
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- Incubation period
- Prodromal stage - Acute stage - Convalescent period |
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What are stages of infection?
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- Colonization
- Invasion - Multiplication - Spread |
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What are common nosocomial infections?
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Staphylococcus aureus, staphylococcus epidermis, pseudomonas aeruginosa, escherichia coli, klebsiella, enterococcus species, candida albicans
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What is incidence?
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The number of new cases of an infectious disease that occurs within a defined population over an estimated period of time
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What is prevalence?
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The number of active cases at any given time
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What is an endemic? Give an example.
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A disease that is present in low incidence all the itme with a particular group of peole with a certain location (eg gonorrhea)
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What is an epidemic? Give an example.
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High incidence of a specific disease in community, usually over a short time span (eg cholera)
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What is a pandemic?
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An endemic that has spread over a wide geographical location
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What are five factors that contribute to antimicrobial resistant organisms?
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- Medications
- Type of infection - Place - Type of bacteria - Condition of the host |
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What are two examples of how medications can contribute to antibiotic resistant organisms?
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- Antibiotic treatment is interrupted or inadequate (eg. stop taking medication when feeling better)
- Extensive use of antibiotics (eg. antibiotic does not work for infection, normal flora is disrupted and infection takes over) |
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What type of bacteria (gram +ve or gram -ve) develops antibiotic resistance more easily and why?
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Gram negative due to it's bacterial cell wall structure is more difficult to penetrate
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How can a bacteria acquire antibiotic resistance?
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- Plasmid transfer of one or more genes from another bacterium
- Transport of resistant bacteria to other bacteria by a virus - Scavenging from dead cells in the vicinity |
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What methods can a bacteria use to resist antibiotics?
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- Produce antibiotic-metabolizing enzymes
- Inhibit antibiotic uptake - Reduce antibiotic binding and action at receptor sites - Synthesize compounds that antagonize antibiotic actions |
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What are examples of antibiotic-metabolizing enzymes produced by bacteria?
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Penicillinase, cephalosporinase
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What is an example of a drug that microorganisms have been able to reduce the uptake (and thus reduce it's effectiveness)?
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Tetracycline
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What are examples of drugs that microorganisms have been able to reduce the binding and action at receptor sites?
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Streptomycin, vancomycin
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What is an example of microorganisms synthesizing compounds that antagonize antibiotic action?
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Para-amino benzoic acid (PABA) -> resistance to sulfonamides
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Who discovered penicillin?
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Alexander Fleming in the 1940's
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What does MRSA stand for?
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Methicillin-resistant Staphylococcus aureus
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What is a name for a penicillinase-resistant penicillin?
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Methicillin (developed in 1960)
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What are the risk factors for hospital acquired MRSA?
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- Recent hospitalization or surgery
- Residence in a long-term care facility - Any type of indwelling catheter - Prior antibiotic usage - Immunocompromised state - IV drug use |
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What are the risk factors for community acquired MRSA?
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- Person to person via contaminated hands
- Sharing towels/clothing - Personal hygiene products - Sports equipment - Food borne outbreaks - Contact sports - IV syringes - Pacific islanders, Alaskan natives, native Americans, prisoners, men who have sex with other men, homeless, marginalized populations |
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What are the four criteria to determine if MRSA is community acquired?
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- Diagnosis made by a positive culture within 48 hours after hospital admission or outpatient setting
- No medical history of MRSA infection or colonization - No medical history within last year of hospitalization, admission to an institutional setting (nursing home, hospice) dialysis, or surgery - No breaks in the skin's line of defense by a medical device or permanent indwelling catheter |
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What are some examples of drugs used for hospital acquired MRSA?
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Vancomycin, linezolid, gentamycin
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What are some examples of medications for community acquired MRSA?
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Tetracycline, clindamycin, trimethoprim-sulfamethoxazole (TMP-SMZ), vancomycin, linezolid
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What makes enterococci so resilient?
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- Can survive in environments that many other species cannot
- Can survive in a broad range of environments (temperature variations, hypotonic/hypertonic, acidic/alkaline, aerobic/anaerobic) - Can colonize for long periods of time - Growth not inhibited by concentrated bile salts - Survives long periods of time on inanimate objects - Intrinsic resistance to antibiotics |
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Where is VRE found?
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- Outdoor vegetation or surface water that is contaminated with animal excrement or untreated sewage
- GI tract in humans |
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What are the risk factors for the development of vancomcin resistance
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- Hospitalization > 7 days
- Interhospital transfer (between floors) - Use of antibiotics - Vancomycin use > 7 days - Use of instruments or prosthetic devices during hospitalization |
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How is VRE transmitted?
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- Direct contact (hospital personnel hands, body fluids)
- Environment and inanimate objects - Interhospital transfer of colonized or infected clients |
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How can enterococci be resistant to vancomycin?
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VRE changed it's peptide chain sequencing so that vancomycin cannot recognize and bind to the enterococci
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What are some treatments for VRE?
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- Quinupristin-dalforpristin, linezolid (thrombocytopenia may occur)
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What distinguishes VISA from VRSA?
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Minimum inhibitory concentration
- VISA requires 8-16 micrograms/ml - VRSA requires >32 micrograms/ml |
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What does ESBL stand for? What are some examples of an ESBL?
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- Extended spectrum beta-lactamase producing organism
- Salmonella, serratia, pseudopneumonia, e-coli |
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What is the pathogenesis for Clostridium difficile?
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Uncolonized client -> antibiotic exposure -> disruption of normal flora -> c-difficile ingestion and colonization -> (Good IgG response -> Asymptomatic carrier state) or (Poor/Partial IgG response -> Production of c-difficile toxins A and B -> Activation of macrophages and mast cells, upregulation of cytokines and other inflammatory mediators -> clinical disease)
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What microorganism is not affected by alcohol handwashing?
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Clostridium difficile
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What would indicate that a stool sample is truly a loose/watery stool?
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If it takes the shape of the container it is poured into
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What populations are at risk for clostridium difficile associated diarrhea (CDAD)?
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- History of antibiotic use
- Bowel surgery - Chemotherapy - Prolonged hospitalization ****** - Increased age - Serious underlying illness or debilitation |
