🧬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