Microbiology Flashcards
How are infectious diseases influenced by genetic changes in mircroorganisms? (3)
Virulence, Host Range, Drug Resistance
What are public health measures that have decreased infectious diseases? (3)
Clean Water, Clean Air, Vaccines
What is an example of change in Host Range?
AIDs, SARS
What are the 3 processes of the evolution of microorganisms?
- Development of increasing genome complexity
- Minor genetic changes resulting in changing pathogenicity, host range, drug resistance
- Natural selection
What are some organisms that spontaneously lost their pathogenicity?
Syphilis, Scarlet Fever
Cholera prevention is associated with what public health measure?
Clean Water
What are some childhood diseases that are prevented from vaccines?
Smallpox, Polio, Diptheria, Measles, Mumps, Rubella
What public health measure prevents respiratory infections like Tuberculosis?
Clean Air
What well-known medical conditions have become recognized as infectious etiology?
Stomach ulcers- from H. pylori
Cervical cancer- Human papillomaviruses
Why are these medical conditions important in understanding of microorganisms? Alzheimers, MS, Type 2 diabetes, Obesity. Heart attacks and stroke
Because they might be caused by infection
Which one of the following infections has declined in severity because of improved hygeine?
cholera
Development of a novel human infections can be caused by:
Changes in host range
Drug resistant strains of mircoorganims can arise from?
Minor genetic changes such as point mutations
What type of genetic material do bacteria have?
DNA with NO INTRONS
What makes bacterias’ chromosomes different from eukaryotes?
Single, circular chromosome
What is the nucleoid?
Non-membrane bound compartment of bacteria composed of the DNA that concentrates in one intracellular postion
What makes bacterial ribosomes a good drug target?
They are 70S “Svedburg Units”, not 80S
How do bacteria reproduce?
Binary Fission
Four major common appearances of bacteria under light mircroscopy
Cocci(round), Bacilli (rods, vibrios-curved rods), Siprochetes (chains)
Procedure for Gram Staining (5 steps)
- Fixation
- Stain (crystal violet)
- Iodine Treatment
- Decolorization with EtOH
- Counterstain with Safranin
What is the basis for gram staining?
Cell walls between gram- and + significantly different, can narrow options FASTLY and CHEAPLY, seldom makes diagnosis
Which gram stain has LPS?
Gram -
What is different about Gram+ cell wall?
3X thicker layer of peptidoglycan, No exterior membrane
What is different about Gram- cell wall?
Thinner layer of peptidoglycan, Exterior membrane
What other test is further for Gram- bacteria?
Acid Fast- do not stain gram+ but different from gram-
What 3 structural elements of bacteria have pathogenic significance?
LPS, Glycocalyx, Pilli/Fimbrae
What structural element found in gram- cell walls can cause septic shocK?
LPS
What structural element is a firm enclosure that resists phagocytosis and is a vaccine target?
Capsule
What are diverse mircobial communities that may host many organmisms and are more resistant than pure colonies?
Biofilms
What are slime layers?
Loose coating of polysaccharide the helps bacteria attach to host cells and form biofilms
What are slime layers and capsule made of?
Glycocalyx
What structural element is used for attachment and is often a virulence factor?
Pili/Fimbrae
What do flagella do?
rotate by a molecular motor to propel a bacteriium forward
Why are flagella a good immune target?
The polymers of flagellin aren’t found in eukaryotes
What do about 50% of all antibiotics target?
70S bacterial ribosomes
3 drugs that target bacterial ribosomes
Aminoglycosides, Tetracyclines, Macrolides
How is spore formation triggered?
nutrient depletion
Why do we have to autoclave?
Because spores survive high temperatures, dehydration, anti-septics, antibiotics
When do spores unpack into normal bacterial form?
When water and nutrients are plentiful again
Modified form of binary fission, 2 unequal copies, one daughter cell dies and other receives double cell wall and macromolecules that enable progeny to be thick and rugged
Spores
Significance of exponential growth to pathogenesis
low number of bacteria can produce very large numbers in very short time, generation time is limited by available nutrients
Describe bacterial growth in a test tube
Lag, Log, Stationary, Death
Why does bacterial growth help with diagnostic testing?
Short generation time
2 Benefits of Fermentation pathway
Don’t have to completely break down glucose
Different waste products–identification in lab testing
What are the usual waste products of Fermentation pathway
Organic acids and alcohols
What ability do Oxygen based ATP metabolism bacteria have to have?
An ability to detoxify reactive oxygen radicals
What are the waste products of Oxygen-ATP metabolism?
CO2, Water
Describe Quorum Sensing
Ability of some bacteria to sense their population density and alter their genetic expression accordingly
What is the process of bacteria altering their genetic expression to secrete virulence factors in high population density?
Quorum Sensing
What 3 things quorum sensing bacteria require?
Secreted Inducer
Receptor for Inducer
Transcription Activator that responds to levels of inducer
Why is quorum sensing beneficial to bacteria?
Conserve Energy, Coordinate their attack
3 common ways HAIs are transmitted
Direct Contact with individual
Indirect contact with equipment/inaminate objects
Respiratory transmission
Seven Strategies for Prevention of Transmission
Hand hygeine
Use of PPE
Isolation of infected individuals
Sterilization of patient care equipment
Clean environment
Room ventilation if expect respiratory infection
Proper disposal of sharps, infectious waste
What is the goal of Infection control?
To break the chain of infection
6 parts of the chain of infection
Infectious agent Reservoir Portal of exit from reservoir Vehicle (means of transmission) Portal of Entry Susceptible Host
4 CDC Standard Precautions for exposure from blood or bodily fluids
Clean hands entering/leaving room
Cover mouth/nose with arm when coughing/sneezing
Gowns/gloves if soiling likely
mask/eye potection if body fluids likely
Airborne (respiratory) Precautions
N95 mask/gown, isolation room at negative pressure
Droplet precautions
mask and gown when entering the room
Contact precautions
gowns entering room, alcohol based products OK
Contact PLUS precautions
Room bleached, hand hygeine soap and water ONLY
Reverse (protective) Isolation
Used for immunocompromised patients
People entering room wear surgical mask, gloves, gown
Sterilzation
Complete destruction of all forms of microbial life
Disinfection
Destruction of specific microorganims, does not kill spores
Antisepsis
Reduction of disease causing germs on body, surfaces
Examples of Critical devices
Enter the body
Surgical equipment, implants, invasive devices
Semicritical items
contact mucous membranes and non intact skin
High level disinfectant
Respiratory therapy items, endoscopes, laryngoscope
Noncritical items
come in contact with intact skin, or non contact
bedpans, BP cuffs, crutches, computers
6 techniques used for sterlization
Steam sterilization, Dry heat sterilization, Irradiation, Filtration, Gas, Plasma
Steam sterilization
autoclaving
Dry heat sterilzation
petroleum based liquids
Irradiation
damage to Nucleic acid, implants
Filtration
liquids that contain protein delicate compounds
Gas sterilization
sterilize surface of porous items
**FLAMMABLE
Plasma sterilization
H2O2 to form free radicals, for resuable medical equipment
Bacterial genotypes (3) for identification
- Biosynthetic genes
- Catabolic genes
- Drug resistance genes
Differences between eukaryotic and bacterial gene expression
Operators/Repressors, no enhancers, no RNA splicing, no post TRXN modification
RNA Polymerase
Binds to the promoter and intiates gene transcription, leads to production of mRNA
Promoter
Regulates when, where, and what level a gene is expressed
Describe Bacteria Genetic Material
Circular Chromosomal DNA
Plasmids that contain 2-3 genes
bacteriophages
What are bacteriophages?
Not essential viruses that infect bacteria
contain small number of genes
can encode virulence factors*
Operon
Cluster of genes whose expression is controlled by one promoter
Ways that transcription is regulated in bacteria
By metabolic products or defiencies directly
Two types of transcriptional regulation
Positive or Negative Regulation
Inducible/Positive Expression
When lactose is present the genes to metabolize lactose are induced by lactose
Repression/Negative Regulation
if trp is present, trp repressor binds to trp operator so that trp trxn is repressed
Ames Test
Tests possible mutagens to see if things are carcinogenic
Quick and Cheap, 85% accurate
3 mechanisms for Gene Exchange
Transformation, Conjugation, Transduction
How was gene exchange in bacteria discovered?
In a classical experiment using mice and viral and nonviral bacteria
Transformation
Cell lysis, neighboring bacteria picks up DNA fragments and incorporates through recombination
When is transformation used in medicine?
Hep B vaccine, insulin production, virus vectors in gene therapy
Conjugation
transfer of F-factor plasmid via a sex pillus. Plasmos can seperate from chromosome and be incorporated into some host genes.
Transducion
Virus mediated transmission of DNA between bacteria
Generalized Transduction
Phage lyses bacteria and releases all its DNA
Specialized Transduction
Phage inserts itself into chromosome and acquires regional DNA from bacteria
Transposons
Can insert themselves and relocate into different sites, pick up different bits of DNA as they move around, move drug resistance genes around together?
How can drug resistance come about so quickly?
Through a combo of gene exchange mechanisms plus point mutations in the host bacteria, a very drug resistant strain of bacteria like MRSA can come about.
Mutualism
Symbiosis, Organism 1 benefits, Organism 2 benefits
Commenalism
organism 1 benefits, organism 2 neither benefits not is harmed
Parasitism
organism 1 benefits, organism 2 is HARMED
Name 3 cases where commensalism can cause disease?
- Injury or poor hygeine carries bacteria somewhere is doesn’t belong
- Immunosuppresion
- Commensal in mother infects neonate during birth
Normal Flora
Commensal and beneficial to healthy individuals from colonization resistance
Some gut bacteria are beneficial
Colonization resistance
A form of symbiosis that even commensals participate in. Prevents pathogen from successfully colonizing the body. Function of innate immunity.
S. epidermis, C. albicans, S. aureus
Commensals found on skin
Streptococci, Staphylococci, Neissera
Commensals found in nose and throat
S. mutans
Commensal found in mouth, will cause cavities and endocarditis with poor dental hygeine
Strep, lactobacilli, yeasts
Commensals in the small intestine
baceteriods, eubacterium, coliform, clostridium
Commensals in the large intestine
pH maitenance in the Vagina
lactobacilli maintains low pH in Vagina, Candida overgrowth follows rising pH
group B strep
Commensal in vagina that can cause sepsis and meningitis in newborns if vaginal delivery without antibiotics
Asymptomatic infections
host defenses clear pathogen before any symptoms of disease are noted
communicable
Infection passed from host to host
Noncommunicable infection
comes from the environment, not a previous host (Think botulism)
latent infection
disease subsides but microorganisms remain in the body and can restart disease later
chronic carrier state
host survives disease but continues to shed the pathogen indefinitely (TB)
epidemic
much more frequent infection than usual
pandemic
worldwide distribution of infection
Obligate intracellular parasites
all viruses, few bacteria.
Must enter the host cells to reproduce
Facultative intracellular parasites
Can reproduce outside host cells when they need to (ie bacteria)
Opportunistic pathogens
very unlikely to cause disease in a healthy person, will take advantage of a host that is injured or immunosuppresed
Commensals
usually non-pathogens with some opportunistic pathogens
Virulence
A numerical measure of pathogenicity
ID50
50% infectious dose- Lower value corresponds to fewer infecting organisms are needed for successful colonization of host
LD50
50% Lethal dose- lower value corresponds to fewer infecting organisms are needed to kill the host
Virulence factors
Gene products expressed by pathogens that directly contribute to the disease process. Can be drug targets.
Siderophores
A molecule that binds and transports Iron in mircroorganisms
Name the 5 major activities of Virulence Factors
- Adhesion
- Survive in extreme environments
- Immune evasion
- Takeover host cell
- Poison the host
Give an example of adhesion
Pili, slime layer, adhesins sticking to host surfaces. Creation of biofilm
An example of survival in extreme environments
pH tolerance, siderophores, resistance to drying or detergents
An example of immune evasion
Capsules resist phagocytosis, IgA proteases, inductions of macrophage apoptosis, “serum resistance” factors escaping complement
An example of host cell takeover
Actin polymerization pathways, endosome escape routes
An example of poisoning the host cell
Tissue degrading enzyme secretions, endotoxins and exotoxins
What are endotoxins?
naturally occuring, exposure causes overactivation of immune system
Gram negative endotoxin, Gram positive endotoxin
negative- LPS, LOS
positive- teichoic acids
What are exotoxins?
Among the most toxic substances known, secreted by bacteria
exposure induces neutralizing antibodies
you can raise vaccines of inactivated toxoid form of exotoxin
Koch’s Postualte- what is it?
Proof of Causality of infectious agent- THE GOLD STANDARD
Structural appearances and features of Gram negative Cocci
(neisseria) diplococci- not quite spherical, grows on chocolate agar, LOS endotoxin in membrane, IgA protesase
Structural appearances and features of Staphylococci
Coagulate plasma (causes abscess), grows in clumps, catalase positive
Structural appearances and features of Streptococci
grows in chains (divide and stay attached), use serotypes to identify strains, catalase negative, cell wall include pili
Name the 3 important Staphylococci
S. aureus, S. epidermis, S. saprophyticus
Gram positive, staphylococci, coagulase positive, causes abscesses, R- nose and skin, T- direct, fomites
S. aureus
Gram positive, staphylococci, catalase positive, coagulase negative, non-hemolytic, novobiocin sensitive, R- skin, mucous membranes T- infected piercings
S. epidermis
Gram positive, staphylococci, catalase positive, coagulase negative, non-hemolytic, novobiocin resistant, R- women reproductive tract, T- UTIs “honeymoon cystitis”
S. saprophyticus
Gram positive, streptococci, catalase negative, alpha hemolytic, optochin sensitive, R=T- throat, when fluid clearnace from lungs is altered
S. pneumoniae
Gram positive, streptococci, catalase negative, alpha hemolytic, optochin resistant, has tissue degrading enzymes, R and T- mouth (can lead to decalcification, plaque, endocarditis
Veridans Streptococci- s. veridans, s. sanguis
Gram positive, betahemolytic, bacitracin sensitive, reacts to group A antiserum, has pili, numerous toxins, R and T- pharynx and skin, sore throats
Group A strep- s. pyogenes
Gram positive, streptococci, beta hemolytic, resistant to bacitracin, CAMP test positive, Capsule, R+T- genital tract, transmits meningitis to neonate
Group B strep- S. agalctiae
Gram positive, streptococci, gamma hemolytic, bile resistant, anaerobic, R+T- normal flora of colon, causes abscesses, UTIs
Group D- Enterococcus fecalis
Gram negative, grows on chocolate agar, ferments maltose, multiple serotypes, capsule, R+T- 5% of all people in respiratory tract, transmitted by droplets
N. meningitides (meningitis)
Gram negative, grows on chocolate agar, does not ferment maltose, NO capsule–pili to allow attachment, R+T- sexual and/or neonatal transmission. Chronic infection may be asymptomatic
N. gonorrhoeae (gonorhea)
