Bacteria Flashcards
What is the infection chain consists of
Host
–> Reservior
–> port of Exit
–> Mode of transport
–> Port of Entry
–> Suspectible Host
Name 4 pathogenic mechanism
Direct invasion into host, multiplication and damage
Production of toxin
Immunopathology
Oncogenesis
What does the outcome of host-pathogen interaction is dependent on?
characteristics of both the pathogen and the host
What does the cytoplasm of a bacteria includes
Nucleoid, plasmids, Ribosomes
What is covering the cytoplasm and what is outside of the stuff aforementioned
Cytoplasmic membrane
Cell Wall
What can be outside of the cell wall
Capsule, Pili/ Fimbriae, fragella, etc
What is pili for
Fragella
For Attachment and transfer of Plasmid
For motility
What is the component of cell wall
Peptidoglycan
What is endospore for
It is present in mainly what type of bacteria
What do we do the remove them
What is their appearance under Gram stain
Adapting to environment as it is resistant to heat, radiation and chemicals
Gram-positive bacteria
Wash hand with soap
Empty cell
What is the structural difference betweeen gram positive and gram niggative bacteria which contributes to the colour change in the result for Gram test
The thickness of peptidoglycan cell wall
Gram positive has thicker cell wall hence can hold more stain to appear violet
While gram niggative bacteria has thinner cell wall after washed by alcohol which degrade the outer membrane hence holds less gram stain and holds the counter stain to appear pink
Name a structure unqiue for gram niggative bacteria
What is it made of
Why does it bring clinical complications
Outer membrane
Lipid, polysaccharide, lipoprotein, lipopolysaccharide
It reduce the permeability of cell wall to antibiotics
How do we classify bacteria according to their oxygen requirement
Strictly aerobic (Must have oxygen)
Facultatively anaerobic (Mainly use aerobic respiration, but can use anaerobic respiration if needed)
Strictly anaerobic (Must have no oxygen)
Microaerophilic (Need low Oxygen and elevated CO2)
For gram positive bacteria
How do we describe if it is spherical shape
How do we describe if it is spore forming rod
How do we describe if the balls are diploid
How do we describe if the balls are in chain
How do we describe if the balls are in 4
How do we describe if the balls have a lot of them
Coccus
Bacillus
diplococci
streptococcus
Tetrad
Cluster
What is the test to different among coccus bacterium
What is the positive result
What is the name of the bacteria which gives positive result
What is the name of bacteria which gives negative result
Catalase test
Formation of Colourless gas bubbles when mixed with Hydrogen peroxide
Staphylococcus
Streptococcus
How to differentiate among staphylococcus bacterium
What are the 2 types of the test.
What are they reacting with to form what
What are the pros and cons
What is the positive result
What is the bacteria giving Positive result
What is the bacteria giving negative result
Coagulase test
Slide test
Fibrinogen to form fibril
Quick (~10s), but can give false negative
Tube test
prothrombin
Definitive, but takes up to 24 hours
Formation of any clot
Staphylococci aureus
Staphylococci Epidermidis
Staphylococci Saprophyticus
What is S. epidermidis
Part of the normal human microbiota, typically the skin microbiota (commensal / normal flora).
*
Adheres to prosthetic devices, e.g., implants, catheters.
*
Causes prosthesis-associated infections.
What is the clinical complication of S. saprophyticus
Acute Cystitis in young woman
What is the appearance of S aureus under Blood agar
What is responsible for the colour
What is it’s function
Golden yellow colonies
Staphyloxanthin
Protect it toxic oxygen radicals
What aids S aureus for
Attachment
Evasion of host defense
Invasion
Toxins
Teichoic acid
Protein A, catalase, coagulase
Protease, hydluronidase, lipase, DNase
Haemolysins
Epidermolytics toxins
Toxic Shock Syndrome Toxins
Enterotoxins
Panton-Valentine leucocidin
What does Protein A of S aureus
inhibits opsonophagocytosis and induces B cell death
** Opsonophagocytosis= Phagocytosis of pathogens opsonized with antibodies and/or complement proteins.
What does
Haemolytic toxins (also name what type is it)
Toxic shock Syndrome toxin
Enterotoxins
Panton-Valentine leucocidin
Cause
Damage erythrocytes lymphocytes, monocytes (α-haemolysin)
staphylococcal scalded (燙傷） skin syndrome
staphylococcal toxic shock syndrome
Food poisoning
Dermonecrosis (necrosis of skin)
What is the
Reservior
Transmission
Risk factor for Staphylococcus aureus
Human (30% healthy people are carrier)
Direct contact
- Risk factors:
- Increasing age.
- Male sex.
- Alcoholism.
- Hospitalisation.
- Diabetes mellitus.
- Dialysis.
- Intravenous drug use.
What does the word pyogenic mean
What are the Pyogenic symptoms caused by Staphylococcus aureus
Forming Pus
- Skin and soft tissue infections.
- Surgical site infections.
- Osteomyelitis, septic arthritis.
- Pneumonia.
- Infective endocarditis.
What are the toxin-mediated symptoms of Staphylococcus aureus
- Staphylococcal scalded skin syndrome.
- Staphylococcal toxic shock syndrome.
- Food poisoning.
What are the examples of Skin and soft tissue infections caused by Staphylococcus aureus
Folliculitis: inflamed hair follicles.
Furuncles: skin abscesses involving the hair follicles and surrounding tissue.
Carbuncles: coalescing clusters of furuncles, deeper suppuration and scarring
In short
Folliculitis= infection of follicle
Furuncle=deeper infection
Carbuncle: >1 Furuncle
What are the antibiotics that can work on Staphylococcus aureus (and the population which are resistant to the antibiotic)
Mark the one which most population are resistant to it. And the enzyme involved
Penicillin (90% of A aureus) [penicillinase]
Vancomycin (Vancomycin-resistant S. aureus, VRSA)
Penicillinase-stable penicillin: methicillin, cloxacillin
(Methicillin-resistant S. aureus ,MRSA)
For streptococci, what are their
Appearance
Diameter
OXygen requirement
Are they encapsulated
Spore-forming?
Gram-positive cocci in chains or in pairs.
0.5-1.2 μm in diameter.
Facultatively anaerobic, some requires CO2 for growth.
Some species are encapsulated.
Non-spore-forming.
How do we classify streptococci according to their haemolytic activity
α-haemolyticstreptococci (partially haemolytic)
β -haemolytic streptococci (fully haemolytic)
non-haemolytic streptococci
How do we further classify β -haemolytic streptococci
By Lancefield Grouping
Name the 2 β -haemolytic streptococci and their result under Lancefield Grouping
Streptococci pyogenes (GAS)
Streptococci agalactiae (GBS)
What can GAS cause
Acute tonsillopharyngitis (扁桃體炎)
Acute skin and soft tissue infections
Invasive GAS disease
Streptococcal toxic shock syndrome
Scarlet fever (猩紅熱)
Acute rheumatic fever (風溼熱 )
Post-streptococcal glomerulonephritis (急性增殖性腎小球腎炎)
What can GBS cause
Neonatal sepsis (blood infection in infant >90 days old)
Various invasive infections
Name an a-haemolytic streptococci
S. pneumoniae
What will Streptococci pneumoniae cause
Pneumococcal pneumonia
Invasive pneumococcal disease
Name 5 Gram positive Bacilli
Listeria monocytogenes,
Corynebacterium diphtheriae,
Bacillus anthracis,
Nocardia,
Clostridium
For gram-negative bacteria, what domain of their outermembrane is most bioactive.
What component of it is used to as endotoxin
What is the antigen on the fimbriae
Lipid A domain
Lipopolysaccharide
What is the natural habitat
And Antigens of
Enterobacterales
Most are commensals in the large bowel of human and animals
O antigen: Somatic LPS antigen
H antigen: Flagellar antigen
K antigen: Capsular antigen
Name 4 examples under enterbacterales
Escherichia Coli
Klebsiella spp.
Salmonella spp.
Shigella spp.
Name 2 Examples of escherichia Coli that cause Diahorrhoeal disease
Name 4 examples of disease that is extraintestinal disease
Enterotoxigenic E. coli (ETEC) → traveller’s diarrhoea
Enterohaemorrhagic E. coli (EHEC)/shiga toxin-producing E. coli (STEC) → haemorrhagic colitis, haemolytic uraemia syndrome.
urinary tract infection,
bacteraemia, (bacteria in blood)
meningitis in neonates, (neonate= baby< 4weeks, meningitis=腦膜炎)
peritonitis (腹膜炎)
Name an example of Salmonella Bacteria
Is Salmonela Oxidase positive or niggative
How can we distinguish the serotypes
Name a clinical significance of the whole family
What can cause typhoid and parathyphoid fever
How do we call those which can cause Disseminated/focal infections
Salmonella Enterica
Different O and H antigen composition
It is an important cause of food poisoning
Salmonella enterica serotypes Typhi + Paratyphi A, B, C.
Non-typhoidal salmonellae.
Name 2 non-fermentors
Pseudomonas aeruginosa
Burkholderia pseudomallei
What is the Shape of the non-fermentors
Oxygen requirement?
Are they resistant to antibiotics?
Why are they called non-fermentators
Bacilli (rod-shape)
Strictly aerobic
Very resistant
They do not ferment glucose
What is the result of Pseudomonas aeruginosa in
Oxidase test
Colour?
Any smell?
What does it cause
What is the clinical complication it cause that has high mortality
What is the mortality for the aforementioned clinical complication
Positive
Green
Fruity
Hospital-acquired infections
Neutropenic septicaemia (a whole-body reaction to an infection)
50%
What does Burkholderia pseudomallei cause
What is the place in which there are endemic
Melioidosis
Southeast Asia and northern Australia; also in China, the Indian subcontinent.
What is the incubation period of Burkholderia pseudomallei
Incubation period 1-21 days (mean, 9 days).
What is Burkholderia cepacia complex
Do they exhibit positive or nigative result in catalase test
What are the clinical disease caused
How is it antibiotic resistivity
a species complex consisting of Burkholderia cepacia and at least 20 different biochemically similar species of Gram-negative bacteria.
Positive
Respiratory tract colonisation/infection in patients with cystic fibrosis.
Nosocomial infections
Often resistant to multiple classes of antibiotics
For Neisseria
Are they
What shape?
Gram positive or niggative
What is their result in oxidase test
Name 2 species of Neisseria
Dicoccus
Niggative
Positive
N. gonorrhoeae (gonococci)
N. meningitidis (meningococci).
What is the function of the pili/fimbriae of the Neisseria
As well as the capsule
Name an endotoxin and what’s its function
Pili/fimbriae: Attachment
Capsule: Anti-phagocytic
Lipo-oligosaccharide. As endotoxin and important in adherence, colonisation and activation of immune cell
What is the reservior and transmission for Neisseria gonorrhoeae
What does it cause in men
What does it cause in women
Extra-genital infection?
What are the disseminated gonococcal infection
Name a clinical disease that happens when it infects an infant of 1st month old
Reservior: Human. By sexual contact and muscosal contact
Urethritis
Endocervicitis.
Pelvic inflammatory disease
Proctitis
Pharyngitis
Infective endocarditis
Septic Arthritis
Meningitis
Gonococcal ophthalmia neonatorum
What agar do we use for Neisseria gonorrhoeae
Does it develop Antitbiotic resistance
Thayer-Martin Agar (improved chocolate agar)
Yes
For Neisseria Meningitidis
What is the reservior
Transmission
One can be carrying the bacteria without having symptoms, how are they called
What clinical disease can it cause
What are the 3 types of vaccines
Humans
Respiratory droplets, direct mucosal contact
Asymptomatic carriage
Invasive meningococcal disease:
* Meningitis.
* Septicaemia (bacteria in blood that cause immune overreaction)
- Purulent conjunctivitis.
- Meningococcal pneumonia.
- Polysaccharide vaccine.
- Quadrivalent conjugate vaccine.
- Serogroup B protein-based vaccine
What can charcoal do in the recovery of Bordetella species
Remove the toxins that may be present in the swab or specimen that inhibit the growth of Brodetella Species
What genus of bacteria cause Cholera
Does all species of it cause cholera
What is the test result for oxidase
Appearance?
Is it motile?
Where is it present
What can it cause
Vibrio
No
Positive
Curved bacilli
Yes
Natural water bodies including sea and fresh water
Gastrointestinal tract infection and severe systemic infection
What can Shigella cause
What are the 4 species
What is the toxin and what is it’s function
bacillary dysentery
S. dysenteriae, S. flexneri, S. boydii, S. sonnei
Inhibits eukaryotic protein synthesis, eventually leading to host cell death.
