Infection and Microbiology Flashcards
What is the biggest kind of microbe?
Eukaryotic
What are the smallest microbes?
Viruses
What microbes are of intermediate size?
Prokaryotic microbes
Do prokaryote microbes have membranes
No- no nuclear membrane or membrane-bound organelles
Do prokaryotic microbes have DNA or RNA?
Both
What are viruses?
Obligate cell parasites
What is meant by obligate?
It has to perform a specific function
Do viruses have DNA or RNA?
One or the other, but not both
Are all agents of infection microbes?
No
What are most deep tissues considered to be?
Sterile
Where are microbes predominantly found?
Epithelial tissue
Why are microbes predominantly found in epithelial tissue?
All epithelial surfaces are constantly in contact with microbes
How was the stomach traditionally considered?
As sterile
Why was the stomach traditionally considered sterile?
Because the acid
What is now known regarding the stomach?
Some microbes are able to withstand acid, and can therefore infect the stoamch
Why aren’t bacteria seen on micrographs?
- They stain poorly with H&E
- Tissue preparation deliberately remove many of them
- Insufficient magnification
- Routine histology often ignores or deliberately removes the microbes normally present on/in the human body
What do normally resident microbes comprise?
Our microbiomes
What is the metabolic power and effect of our microbome comparable too?
At least an organ like the lvier
What are differences in individuals’ microbes linked to?
Health and disease
How is an individuals microbiome linked to health?
Important for tissue differentiation
How is an individuals microbiome linked to disease?
Can be significant in obesity, diabetes and psoriasis
What do we need to see microbes?
Special stains and microscopy techniques
What does the Gram stain allow?
Detection and beginnings of classification of most bacteria
What do acid fast stains allow?
Detection of bacterial causes of TB and leprosy
What is the clinical importance of bacteria stains?
Help in diagnosis and treatment of infection
What happens in the Gram stain?
- +vely charged crystal violet binds to -vely charged cell components, predominantly nucleic acids
- Iodine forms large molecular complexes with crystal violet
- Acetone and methanol extract the complexes through the Gram -ve, but not through the Gram +ve cell wall
- Red dye is used to stain the now unstained Gram -ve cells
What does the Gram stain reveal?
Profound difference in the cell surface of different types of bacteria
What colour do Gram+ bacteria stain?
Dark blue
What colour do Gram- bacteria stain?
Red
Describe the bacterial cell envelope of a Gram+ bacteria
- Single molecule spreading all the way around the cell surface
- Thicker peptidoglycan covering on outside
- Cytoplasmic membrane on inside
How does the Gram- cell envelope differ from that of the Gram+?
NAME?
Describe the bacterial cell envelope of a Gram- bacteria
- Outer membrane
- Layer of peptidoglycan
- Cytoplasmic membrane
Give 3 shapes of bacteria
- Cocci
- Rods/bacilli
- Coccibacilli
Give 3 variations of bacteria
- Curved
- Spiral
- Filamentous
Give 2 internal structures of bacteria
NAME?
Give 3 external structures of bacteria
- Fimbrae/pili
- Flagallae
- Capsule
What does the Gram- out membrane consist of?
NAME?
What is significant about the LPS layer?
It is highly toxic
What are most symptoms of infection caused by?
The immune reaction
Give 3 cell envelope types that can’t be visualised by the Gram stain?
- Mycobacterium
- Mycoplasmas
- Those that are too small
What stains can be used to visualise mycobacterium?
- Acid fast stain
- Fluorescent
- Z-N brightfield stains
Give an example of an acid fast stain
Turamine
Why can’t mycoplasmas be visualised by the Gram stain?
No peptidoglycan
Give 2 examples of mycobacterial diseases?
NAME?
What does the mycobacterial cell wall consist of?
- Glycolipids on outside
- Mycolic acid
- Arabinogalactan
- Peptidoglycan
- Plasma membrane
What is the advantage of smears for acid fast bacilli?
Rapid
What is the disadvantage for smears for acid fast bacilli?
Relatively insensitive
What is the clinical importance of cell walls?
- Detection and diagnosis via Gram and acid fast stains
- Endotoxin effects
- Target for antibiotics
What is the advantage of using bacterial cell walls as a target for antibiotics?
Allows for selective toxicity
Give 3 examples of antibiotics that use cell walls as their target
- ß-lactams
- Glycopeptides
- Isoniazid
Where can bacteria be grown?
- In broth
- Colonies on agar media
- Biofilms
How do bacteria grow in broth?
Replication by binary fission
What does growth in broth give rise to?
Lag, exponential (log) and stationary phases of growth
What are the stages that happen when bacteria grow on biofilms?
Attachment → colonisation → growth on surface
What is the clinical importance of broth turbidity?
NAME?
What is the clinical importance of colonies?
Easy identification and counting of bacteria
What is the clinical importance of biofilms?
Can model bacterial growth on medical devices
Why is bacterial growth on medical devices important?
Because one of the major reasons for needing to remove intravascular diseases is that they get infected
What is the clinical importance of the speed to bacterial growth?
- Rate at which disease develops
- Time available to diagnose
What are the requirements for bacterial growth?
- Specific energy source
- Specific building blocks
- Specific atmosphere
What atmosphere is required by the majority of bacteria in/on the body?
Absence of oxygen
What are the 3 types of organisms, classified by their atmospheric requirements?
- Aerobes
- Anaerobes
- Facultative
Give 2 Gram+ cocci?
- Staphylococcus
- Streptococcus
Give a Gram+ bacilli
Clostridium
Give a Gram- cocci
Neisseria
Give 7 Gram- bacilli
- Escherinchia
- Salmonella
- Helicobacter
- Pseudomonas
- Legionella
- Bacteriodes
What is the problem with spore forming groups of organisms?
They are difficult to eliminate with disinfection, because can withstand boiling
What are the major groups of prokaryotes?
- Bacteria
- Archaea
What are the features of prokaryotes?
- No membrane-bound organelles
- 1 chromosome
- No introns
- Coupled transcription/translation
- Very labile mRNA
What ribosomes to prokaryotes have?
70s (30s+50s)
What do all bacteria have?
Peptidoglycan cell wall
What prokaryotes don’t have peptidoglycan cell walls?
Mycoplasms
What are the major groups of eukaryotes?
NAME?
What are the important features of eukaryotes?
- Membrane-bound organelles
- Many chromosomes
- Introns
- Compartmentalised transcription/translation
- Stabile and labile mRNA
What ribosomes do eukaryotes have?
80s (40s+60s)
Do eukaryotes have peptidoglycan cell walls?
No
What is infection?
The establishment of an organism on/in a hist associated with its multiplication and damage or dysfunction of host, specifically related to that microorganism or its product
What causes infection?
Pathogenic microbes;
- Viruses
- Prions
- Bacteria
- Archaea
- Protozoa
- Fungi
- Helminths
Why do particular individuals get particular infections?
- Encounter
- Virulence vs. host resistance
- Innate and adaptive immunity
What influences the outcome of an infection?
- Encounter dose and route
- Virulence and host resistance
- Innate and adaptive immunity
- Timely diagnosis and treatment
