Bacteria ✅ Flashcards
What is the size of bacteria comparable to?
Variable - smallest similar to the largest viruses, biggest are the size of RBCs
What are the shapes of bacteria?
- Cocci
- Bacilli
- Spiral
What shape are cocci?
Round
What shape are bacilli?
Rod-like
What shape are spirochetes?
Spiral
What arrangements can cocci take up?
- Clusters
- Chains
- Pairs
Give an example of a cocci that exists in clusters?
Staph aureus
Give an example of a cocci that exists in chains
Streptococcus pneumoniae
Give an example of a cocci that exists in pairs
Neisseria meningitidis
Are bacteria capable of independent metabolic existence and growth?
Most are
What are bacteria called when they are not capable of independent metabolic existence and growth?
Obligate intracellular pathogens
Give 2 bacteria that are obligate intracellular pathogens
- Chlamydia
- Rickettsia
How do bacteria multiply?
Binary fission
What is produced from cell division in bacteria?
Each cell produces 2 daughter cells
What is the result of each bacterial cell producing 2 daughter cells?
Allows exponential growth of bacterial colonies
How long does it take for a single bacterium to develop into a million?
Can be within hours
What is bacterial classification based on?
- Gram reaction
- Bacterial shape
- Growth requirement
- Presence of spores
What can bacteria be classified into on the basis of growth requirements?
- Aerobic
- Anaerobes
What is the most common type of class of bacteria in terms of growth requirement?
Aerobes
What can aerobic bacteria be further divided into?
- Obligate aerobes
- Faculative aerobes
What are obligate aerobes?
Bacteria that require oxygen to grow
What are facultative aerobes?
Bacteria able to generate energy in the absence of sufficient oxygen
What are anaerobic bacteria?
Bacteria only able to grow in an atmosphere containing less than 20% oxygen
What can some bacteria do to survive in adverse conditions?
Produce spores
What does the generation of bacterial spores allow survival in the face of?
Exposure to chemicals and heat
Give an example of a spore forming bacteria
Clostridium species
What is the limitation of classification of bacteria based on gram staining?
Some do not take up the gram stain
Give 4 bacteria that do not take up gram stain
- Mycoplasma
- Chlamydia
- Rickettsia
- Mycobacteria
Why do mycoplasma not take up gram stain?
They have no cell wall
Why do chlamydia and rickettsia not take up gram stain?
They are intracellular bacteria
What staining is required to detect mycobacteria
Acid fast staining
Give 3 examples of bacteria that are;
- Gram positive
- Cocci
- Aerobic
- Non-spore forming
- Staphylococci
- Streptococci
- Enterococci
Give an example of a bacteria that is
- Gram positive
- Bacilli
- Aerobic
- Non-spore forming
Listeria
Give an example of a bacteria that is:
- Gram positive
- Bacilli
- Aerobic
- Spore forming
Bacillus
Give an example of a bacteria that is:
- Gram positive
- Bacilli
- Anaerobic
- Spore forming
Clostridium
Give an example of a bacterium that is:
- Gram negative
- Cocci
- Aerobic
- Non-spore forming
- Neisseria
Give 5 examples of a bacteria that is:
- Gram negative
- Bacilli
- Facultative aerobic
- Non-spore forming
- E coli
- Klebsiella
- Salmonella
- Shigella
- Haemophilus
Give an example of a bacteria that is:
- Gram negative
- Bacilli
- Aerobic
- Non-spore forming
Pseudomonas
Give an example of a bacteria that is:
- Gram negative
- Bacilli
- Anaerobic
- Non-spore forming
Bacteroides
Give an example of a bacteria that is:
- Gram negative
- Spirochete
- Anaerobic
- Non-spore forming
Borrelia
What do bacterial cells consist of?
Cytoplasm surrounded by cell wall
What is found in the cytoplasm of bacteria?
- DNA
- Ribosomes
- All elements required for growth and pathogenesis
In what forms does DNA exist in bacteria?
- Single chromosome of circular DNA
- Within plasmids
What is the importance of the cell wall of bacteria?
Essential for survival
What is the clinical implication of the cell wall being essential for the survival of bacteria?
It is a key target for antibiotics
Describe the structure of the cell wall in a gram positive bacteria?
They have a thick peptidoglycan layer with no outer membrane
What colour do gram positive bacteria appear on gram stain?
Blue/purple
Why do gram positive bacteria appear blue/purple on gram stain?
Due to retention of crystal violet dye in the thick cell wall
Describe the structure of the cell wall of a gram negative bacteria?
They have a thin peptidoglycan layer surrounding by an outer lipid membrane
What colour do gram -ve bacteria appear on gram stain?
Red/pink
What might be found in the periplasmic space of gram-negative bacteria?
ß-lactamase
What is the clinical relevance of ß-lactamase?
It degrades antibiotics such as penicillin
What might be found on the cell surface of bacteria?
- Endotoxin
- Pili
- Flagella
- Other proteins
What components found on some bacteria can induce septic shock?
- Endotoxins
- Teichoic acid
Where are endotoxins found?
On the outer membrane of gram-negative bacteria
What are bacterial endotoxins made of?
Lipopolysaccharide
Where is teichoic acid found?
In gram positive bacteria
What are pili?
Hair like structures
What is the function of pili?
Facilitate adhesion and acquisition of external DNA
What is the function of flagella?
Help with locomotion
What is the clinical relevance of flagella?
Can help with bacterial identification
What might other proteins found on the cell surface of bacteria act as?
- Sensors
- Receptors
- Adhesins
What may bacteria be surrounded by?
A polysaccharide capsule
Give 3 bacteria that are surrounded by a polysaccharide capsule?
- Streptococcus pneumoniae
- Neisseria meningitidis
- Klebisella pneumonia
- Escheria coli
What is the purpose of a polysaccharide capsule surrounding bacteria?
It enables them to evade phagocytosis
What plays an important role in clearing bacteria with a polysaccharide capsule?
The spleen
What is the implication of the spleen playing an important role in clearing bacteria with a polysaccharide capsule?
Individuals who are hyposplenic are more susceptible to these organisms
What do some bacteria produce in addition to the capsule?
Slime
What is slime?
A tough protective matrix
What is the clinical relevance of slime-producing bacteria?
- Very difficult for antibiotics to penetrate
- Can form biofilms on foreign materials
What routes can bacteria be transmitted via?
- Respiratory
- Gastrointestinal
- Urogenital
- Cutaneous
What do bacteria do once they have entered the body?
Adhere to mucosal sites
What facilitates the adherence of bacteria to mucosal sites?
- Pili
- Surface proteins
When is it said that bacteria have ‘colonised’?
Once a stable population has been established
What happens in some instances of bacterial colonisation?
Invasion occurs, and the bacteria penetrate host cells and tissues
Are all strains of bacteria equally pathogenic?
No
Give an example of where not all strains of bacteria are equally pathogenic?
There are 6 strains of Haemophilus influenza, but type b (Hib) causes the most serious disease
What does different strains of the same bacteria having differing virulence determinants give rise to?
Distinct patterns of infection
Give an example of where the same bacteria having different virulence determinants can cause distinct patterns of infection
E. coli may cause disease in the GI tract, meningitis, sepsis, or UTI
