🧬Microbiology Flashcards
What are the 4 main groups of microbes?
- Eukaryotes
- Parasites
- Protozoa
- Fungi - Prokaryotes (no nucleus)
(ie. bacteria) - Viruses (acellular)
- Prions (acellular)
What are the basic steps for infection to occur?
- Pathogen
- Susceptible host
- Entry of pathogen to host
- Colonization (adhere, replicate, evade)
- Damage caused
- Direct vía virulence factors
- indirect via immune system
What are the main portal of entry for pathogens?
- Mucous membranes
- Resp Tract
- GI
- GU
- Placenta - Skin
- Parenteral
- bites
- puncture
- wound
- injection
Pathogens portal of entry
- Most have preferred POE
Ex. Strep - Some cause illness from any entry
Ex. Ebola - Some cause different disease depending on POE
Ex. Bubonic/pneumonic plague.
What is the progress of infection following adherence?
- Exposure
- Colonization
- Latency period
- Incubation period
- Infection
- Period of communicability
What are examples of human barriers to infection?
- Lysozyme in tears/sweat
- HCl in stomach
- Fatty acids
- Phagocytosis WBC
- Ciliated mucosa (resp) (physical)
- Skin
What are virulence factors for colonization of the host?
- Adherence: adhesins (bacteria), attachment proteins (viruses)
- Destructive enzymes: hyaluronidase (destroy connective tissue), hemolysins
- Toxins: anthrax (bacteria)
What are virulence factors for immunoevasion?
- Prevent antibody binding: capsule (bacteria, yeasts)
2. Prevent phagocytosis: Biofilm (bacteria, yeast)
What are virulence factors for immunosuppression?
- Destructive enzymes:: immunoglobulin proteases
2. Conversion enzymes: catalase
What are virulence factors for invasion of host cells?
Destruction (lysis) of host cells
What happens during indirect damage via host immune response?
Septic shock
Endotoxins
Part of Gram-negative cell wall
(Lipopolysaccharide; LPS)
- Triggers immune cells to release cytokines in toxic concentrations
- Antibiotics can trigger release (get worse before gets better)
Exotoxins
Enzymes that are secreted by bacteria that perturb some aspect of normal host physiology
- Generally specific to genus/species
- Highly immunogenic
What does damage to the host facilitate?
- Invasion
- Dissemination
- Transmission
Ex: cholera uses toxin to cause diarrhea in order to spread to others
What are the steps in nucleic acid sequences? (PCR)
- Denaturation
- Annealing - primer binds
- Elongation - extension of primer
- Repeat
- Detection
Gram Negative
- PINK
- Outer membrane
- Periplasmic space
- Liposaccharide (LPS) endotoxin = SEPTIC SHOCK
- 10-20% of cell wall is peptidoglycan
Gram Positive
- PURPLE
- NO Outer membrane
- NO LPS
- 60-90% cell wall is peptidoglycan
What are the three shapes of bacteria?
- Spherical
- Rod-like
- Spiral
What are the different arrangements of bacteria?
- Clusters
- Chains
- Pairs
- Tetrads
Glycocalyx
Viscous, gelatinous polymer composed of polysaccharides, polypeptides, or both.
- Capsule = organized and attached to cell wall
- Slime layer = unorganized and loosely attached
- Visualized with negative stains
- Prevents antibodies recognizing bacteria
- Assists with attachment to surfaces
Tropism
The type of host cell receptors that bind bacteria (adhesins) and visuals (attachment proteins).
What are the 2 general phases of bacterial growth?
- Free-swimming (planktonic)
2. Sessile, surface associated (Biofilm)
Biofilms
Aggregated of organisms encased in a matrix consisting of proteins, carbohydrates, and nucleic acid complex structure.
- Ubiquitous
- Resistant to immune clearance, antibiotics, disinfectants
- Metabolically less active bacteria
What are the six links in The Chain if Infection?
- Pathogen
- Reservoir
- Portal of exit
- Means of transmission
- Portal of entry
- New host
Golden hour of sepsis
- Every hour treatment is delayed, chance of survival decreases by 8%
- Goal is to draw cultures and administer antibiotics within the hour sepsis is suspected
What are the 6 Domains of Quality
- Safe
- Timely
- Efficient - avoid waste
- Effective - evidence-based
- Equitable
- Patient centered
What are examples of preventable medical events?
- Patient falls
- Hospital-acquired infections
- Medication errors
Hierarchy of Effectiveness
- System-Based = Most effective, least feasible
- Person-based = Least effective, most feasible
- Low leverage, least effective:
- rules and policies
- education and information - Medium Leversge, moderately effective
- simplification and standardization
- reminders, checklists, double checks - High Leverage, most effective
- forcing functions and constraints
- automation or computerizatio
What is the primary objective of public health programs?
Preventing things BEFORE they happen
- Immunization clinics
- Sexual health education
- Prenatal classes
What is the secondary objective of public health programs?
Preventing ongoing transmission, including early case findings
- Screening TB, STIs
- Case findings (ex NG swabs)
- Outbreak investigation/contact tracing
- Notifiable Disease Reporting to MOH
What are elements of Routine practice for preventing the transmission of infection?
- Point of care risk assessment
- Hand hygiene
- Selection of appropriate PPE
- Disinfection of shared equipment
- Sharps safety
- Environmental cleaning
Point of care risk assessment
Determined which components of Routine Practices are required. Considers:
- The patient
- The healthcare worker
- The environment
- The planned clinical interaction
What are indications for Droplet Precautions?
Upper Respiratory Infections:
- Pertussis
- Diptheria
Lower Respiratory:
- Influenza
- Coronavirus
- MRSA, RSV, GAS
- Meningitis
Droplet Precautions
- Maintain 2 meters between patients with curtain drawn
- Hand hygiene use within 2 meters
- Gown
- Gloves
- Mask
- Eye protection
Airborne precautions
Droplets are small particles < 5 microns
- Hand washing
- N95 Mask
- Negative Pressure Room
What are the 3 infections that require airborne precautions?
- Tuberculosis
- Chickenpox (varicella)
- Measles virus
What is an example
Of a pre-analytical laboratory error?
Patient/specimen mis-identification or mislabeling
An organism that only grows at the bottom of the liquid broth media tube
Obligate anaerobes
Proper blood cultures collection technique includes:
- 2-3 sets per sepsis episode
- 2 bottles per set
- 8-10mL per bottle
- Peripheral blood culture preferred
What does nitrites one a urinalysis indicate
Infection. E Coli metabolizes nitrates into nitrites.
What are indications of a urinalysis contamination?
- 3 or more species of bacteria
What container is used for stool culture and sensitivity (C+S) testing?
Enteric Pathogen Transport Medium (keeps bacteria alive)
What container is used for stool ova and parasites (O+P) testing?
Acetate Formalin Fixative (kills bacteria)
What container is used for stool testing for C. difficile?
Sterile container
** diarrheal still only, not formed**
When would a swab be acceptable for specimen to diagnose a diarrheal illness?
In paediatrics
What are the 4 moments of hand hygiene?
- Before initial patient/environment contact
- Before aseptic procedure
- After body fluid exposure risk
- After patient/environment contact
Which blood drawing technique is most prone to contamination from the host’s mucroflora?
Drawing blood from a catheter
What should occur following urine collection to increase the specificity of the culture?
Place into refrigerator if not cultured within 30 minutes
Health Protection and Promotion Act (HPPA)
Specifies the organization and delivery of public health
- Gives Public Health Units oversight time provide public health services
- Gives the Medical Officer of Health (MOH) the power to act in public heal emergencies
Legislation: law voted by legislative branch
Regulation: process that defines the overall law (rules, codes, etc) - frequently updated
Mumps virus
- PATHOGEN: RNA virus
- MODE OF TRANSMISSION: Droplet, saliva
- INCUBATION PERIOD: 12-25 days
- PERIOD OF COMMUNICABILITY: 2 days before and up to 5 days after onset of symptoms
- TESTING: serology and molecular (PCR)
What is the definition of an outbreak?
The occurrence of cases of a disease in excess of what would normally be expected at particular TIME and PLACE.
What is the definition of an index case
First case to be IDENTIFIED at the start of an outbreak
What is the definition of reproductive rate (R0)?
Average number of new cases that a case generates over the course of the infection period (mumps R0 = 4.7)
Ex. An individual with measles is likely to spread the virus to ~18 people on average
What is the definition of an eliminated disease?
Reduction to zero the incidence of a specified disease in a defined geographical area as a result of deliberate efforts
What is an endemic disease?
Situation where a chain of transmission continues uninterrupted for a period greater than one year
What is the definition of an imported case?
A confirmed case that was not acquired outside of Canada
What is a case definition?
Describes criteria for: associated with particular infectious disease
- Person
- Place
- Time
- Clinical features
Hepatitis A
- Transmission = fecal-oral
- Incubation: 15-50 days
- Symptoms: fever, jaundice, dark urine, fatigue, n/v, pain
- Outbreak potential: contaminated food and high risk activities
- HBV vaccine neutralizes HBsAg preventing infection
Phylogenetics
Evolutionary relationships
What are the 4 ways to prevent needlestick/sharps injuries?
- Elimination of needles/sharps
- Engineering controls - sharps disposal containers
- Administrative controls - develop processes
- PPE
What are the pathogens of greatest concern in regards to needlestick/sharps injuries?
- HBV - 30% change of infection if source is positive
- HCV - 3% if source is positive
- HIV - 0.3%
Hepatitis B Virus (HBV)
- Transmission: blood
- Occupational disease
- Incubation: 6 wks - 6 months; avg 3 months
- Tx: antiviral management for chronic infection; no cure
Hepatitis C Virus (HCV)
Hepatitis, cirrhosis, liver failure, liver cancer
- Transmission: blood
- Occupational disease
- Incubation: 2 wks - 6 months; avg 2 months
- Tx: curative since 2014; direct acting antivirals
no vaccine
Human immunodeficiency Virus (HIV)
Acquired immunodeficiency syndrome (AIDS), opportunistic infections, cancers
- Transmission: blood
- Occupational disease
- Incubation: 1-2wks
- Patho genesis: destruction of CD4+ immune cells over ~10yrs
- Tx: highly-active antiretroviral therapy (HAART); no cures
What is the required antibody response for HBV immunization for HCPs?
10 IU/mL or more
What are the four stages in the QI Model of Improvement?
- Plan
- Do
- Study
- Act
Ishikawa (Fishbone) Diagram
Brainstorming tool used to identify potential causes of a specific quality problem
What is the definition of a “shift” in Run Charts Data collection?
6 or more consecutive points above median
What is the definition of a “trend” in Run Charts Data collection?
5 or more consecutive points in ascending or descending order
What is the definition of “too many or too few runs” in Run Charts Data collection?
How often data crosses the median
Archaea
Generally extremophiles (pH, temp, salinity)
Never been associated w/ human infection
Pathogens
A microorganism that can cause disease
Non-living microbes
- Viruses
- Prions
Infectious, misfolded proteins they self-replicate
Living microbes
- Eukaryotes (nucleus)
- fungi
- parasites
- protozoa - Prokaryotes (no nucleus)
Aerobes
Growth in ambient air, require O2 as terminal electron acceptor
Obligate aerobes
Absolute requirement of O2 to be able to grow, usually have no fermentativa pathways.
Ex. Pseudomonas, bacillus, mycobacterium
Anaerobes
- Usually cannot grow in presence of O2 (O2 is toxic).
- Use other substrates as electron acceptor.
- Metabolism is frequently fermentative -> reduce organic compounds to various end products.
- Constitute 99% of culturable flora in mucosal surfaces (ex. Oral, GI, GU)
Obligate anaerobes
O2 highly toxic, fermentative metabolism.
Ex. Actinomyces, bacteroids, clostridium
Facultative anaerobes
- Capable of growth under both aerobic and anaerobic conditions
- Preferentially use O2 as terminal electron acceptor
- Will respite aerobically until O2 exhausted, then switch to fermentation or aerobic resp
Ex. Most bacteria, Escherichia coli
Virus properties
- Absolute dependence on living host for reproduction (obligate intracellular parasite)
- Viral genome directs synthesis of new viral particles by usurping host cell components
- Viruses can bud from cells or lyse cells
What are the 3 methods of diagnostic virology?
- Viral isolation (cell culture)
- Direct detection of virus
- Serology (immunodiagnostics)
Diagnostic Viral isolation
- Not all viruses are cultureable
- Can take weeks (long TAT)
- Some viruses may lose viability in transit to lab
- Yield can be limited
Diagnostic direct detection of virus
- Electron microscope (ex. Norovirus, variola)
- Pathology specimens (light microscope) (CMV “owl eyes” in tissue specimen)
- Detection of viral antigen (influenza A of resp secretions)
- Molecular techniques (PCR) -> viral genes
Diagnostic viral serology (aka immunodiagnostics)
- Detection of antibody (host) or antigen in blood
- Profile of antibody response to infection
- Determine immunity (IgG) or recent infection (IgM/seroconversion)
- Antibodies can be cross-related
What is the appropriate mycology specimen collection?
- Aseptic technique (avoid bacterial contamination)
2. Tissue/fluids - NOT SWABS
What is the proper specimen transport for fungi?
Sterile container, transport quickly (bacteria outgrow fungi)
What are the two types of fungi?
- Single-celled (yeasts, round/oval, asexual)
2. Multi-celled (“molds”, filamentous fungi, sexual and asexual)
Mycoses (fungal infection)
- Very slow progression (molds)
- Difficult to treat -> chronic infections
- Superficial most common (ex. Tinea)
- human-human transmission
- immunocompetent - Subcutaneous: muscle, connective tissue, systemic (invasive), internal organs
- human-human transmission rare
- immunicompromised
What are the 2 methods in diagnostic mycology ?
- Direct detection
- presumptive, confirmed by culture - Culture
- grown on media usually containing antibiotics
Vector
Living organism that carries a disease-causing organism to a host
Ex. Mosquitoes + malaria
What are the different types of parasites?
All eukaryotes
- Single-cell protozoa (ex. Malaria)
- Multi-called metazoa (ex. Works and insects)
Pinworms
- Most common parasitic infection
- Children = primary host
- Eggs = sticky
- Symptoms = anal itching
What are the 3 methods in diagnostic parasitology?
- Direct detection
- protazoa and metazoa found in blood, stool, and sometimes tissues - Histopathology (tissue biopsy)
- Serology (immune response)
Malaria
- Fever from the tropics
2. Incubation period >21 days
TAT
Turn around time
What are the 3 rapid diagnostic tests?
- Nucleic acid/signal amplification testing (PCR, NAAT)
- Novel technologies (similar to MRI)
- Point of care tests (at bedside, PCR in a box)
Mycology direct detection
- Calcofluor white
- Chitin present in fungi cell wall will fluoresce
- Fungal elements (hyphae)
What are the 5 virulence factors?
- Colonization of host
- Immunoevasion
- Immunosuppression
- Invasion of host cells
- Obtain/sequester nutrients from host