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MBBS IASM > Bacteria > Flashcards

Bacteria Flashcards

1
Q

What is the infection chain consists of

A

Host
–> Reservior
–> port of Exit
–> Mode of transport
–> Port of Entry
–> Suspectible Host

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2
Q

Name 4 pathogenic mechanism

A

Direct invasion into host, multiplication and damage

Production of toxin

Immunopathology

Oncogenesis

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3
Q

What does the outcome of host-pathogen interaction is dependent on?

A

characteristics of both the pathogen and the host

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4
Q

What does the cytoplasm of a bacteria includes

A

Nucleoid, plasmids, Ribosomes

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5
Q

What is covering the cytoplasm and what is outside of the stuff aforementioned

A

Cytoplasmic membrane
Cell Wall

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6
Q

What can be outside of the cell wall

A

Capsule, Pili/ Fimbriae, fragella, etc

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7
Q

What is pili for

Fragella

A

For Attachment and transfer of Plasmid

For motility

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8
Q

What is the component of cell wall

A

Peptidoglycan

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9
Q

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

A

Adapting to environment as it is resistant to heat, radiation and chemicals

Gram-positive bacteria

Wash hand with soap

Empty cell

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10
Q

What is the structural difference betweeen gram positive and gram niggative bacteria which contributes to the colour change in the result for Gram test

A

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

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11
Q

Name a structure unqiue for gram niggative bacteria

What is it made of

Why does it bring clinical complications

A

Outer membrane

Lipid, polysaccharide, lipoprotein, lipopolysaccharide

It reduce the permeability of cell wall to antibiotics

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12
Q

How do we classify bacteria according to their oxygen requirement

A

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)

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13
Q

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

A

Coccus

Bacillus

diplococci

streptococcus

Tetrad

Cluster

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14
Q

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

A

Catalase test

Formation of Colourless gas bubbles when mixed with Hydrogen peroxide

Staphylococcus

Streptococcus

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15
Q

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

A

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

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16
Q

What is S. epidermidis

A

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.

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17
Q

What is the clinical complication of S. saprophyticus

A

Acute Cystitis in young woman

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18
Q

What is the appearance of S aureus under Blood agar

What is responsible for the colour

What is it’s function

A

Golden yellow colonies

Staphyloxanthin

Protect it toxic oxygen radicals

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19
Q

What aids S aureus for

Attachment

Evasion of host defense

Invasion

Toxins

A

Teichoic acid

Protein A, catalase, coagulase

Protease, hydluronidase, lipase, DNase

Haemolysins
Epidermolytics toxins
Toxic Shock Syndrome Toxins
Enterotoxins
Panton-Valentine leucocidin

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20
Q

What does Protein A of S aureus

A

inhibits opsonophagocytosis and induces B cell death

** Opsonophagocytosis= Phagocytosis of pathogens opsonized with antibodies and/or complement proteins.

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21
Q

What does

Haemolytic toxins (also name what type is it)

Toxic shock Syndrome toxin

Enterotoxins

Panton-Valentine leucocidin

Cause

A

Damage erythrocytes lymphocytes, monocytes (α-haemolysin)

staphylococcal scalded (燙傷） skin syndrome

staphylococcal toxic shock syndrome

Food poisoning

Dermonecrosis (necrosis of skin)

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22
Q

What is the

Reservior

Transmission

Risk factor for Staphylococcus aureus

A

Human (30% healthy people are carrier)

Direct contact

  • Risk factors:
  • Increasing age.
  • Male sex.
  • Alcoholism.
  • Hospitalisation.
  • Diabetes mellitus.
  • Dialysis.
  • Intravenous drug use.
23
Q

What does the word pyogenic mean

What are the Pyogenic symptoms caused by Staphylococcus aureus

A

Forming Pus

  • Skin and soft tissue infections.
  • Surgical site infections.
  • Osteomyelitis, septic arthritis.
  • Pneumonia.
  • Infective endocarditis.
24
Q

What are the toxin-mediated symptoms of Staphylococcus aureus

A
  • Staphylococcal scalded skin syndrome.
  • Staphylococcal toxic shock syndrome.
  • Food poisoning.
25
Q

What are the examples of Skin and soft tissue infections caused by Staphylococcus aureus

A

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

26
Q

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

A

Penicillin (90% of A aureus) [penicillinase]

Vancomycin (Vancomycin-resistant S. aureus, VRSA)

Penicillinase-stable penicillin: methicillin, cloxacillin
(Methicillin-resistant S. aureus ,MRSA)

27
Q

For streptococci, what are their

Appearance

Diameter

OXygen requirement

Are they encapsulated

Spore-forming?

A

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.

28
Q

How do we classify streptococci according to their haemolytic activity

A

α-haemolyticstreptococci (partially haemolytic)

β -haemolytic streptococci (fully haemolytic)

non-haemolytic streptococci

29
Q

How do we further classify β -haemolytic streptococci

A

By Lancefield Grouping

30
Q

Name the 2 β -haemolytic streptococci and their result under Lancefield Grouping

A

Streptococci pyogenes (GAS)
Streptococci agalactiae (GBS)

31
Q

What can GAS cause

A

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)

32
Q

What can GBS cause

A

Neonatal sepsis (blood infection in infant >90 days old)

Various invasive infections

33
Q

Name an a-haemolytic streptococci

A

S. pneumoniae

34
Q

What will Streptococci pneumoniae cause

A

Pneumococcal pneumonia
Invasive pneumococcal disease

35
Q

Name 5 Gram positive Bacilli

A

Listeria monocytogenes,
Corynebacterium diphtheriae,
Bacillus anthracis,
Nocardia,
Clostridium

36
Q

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

A

Lipid A domain

Lipopolysaccharide

37
Q

What is the natural habitat

And Antigens of

Enterobacterales

A

Most are commensals in the large bowel of human and animals

O antigen: Somatic LPS antigen

H antigen: Flagellar antigen

K antigen: Capsular antigen

38
Q

Name 4 examples under enterbacterales

A

Escherichia Coli
Klebsiella spp.
Salmonella spp.
Shigella spp.

39
Q

Name 2 Examples of escherichia Coli that cause Diahorrhoeal disease

Name 4 examples of disease that is extraintestinal disease

A

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)

40
Q

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

A

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.

41
Q

Name 2 non-fermentors

A

Pseudomonas aeruginosa
Burkholderia pseudomallei

42
Q

What is the Shape of the non-fermentors
Oxygen requirement?
Are they resistant to antibiotics?
Why are they called non-fermentators

A

Bacilli (rod-shape)

Strictly aerobic

Very resistant

They do not ferment glucose

43
Q

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

A

Positive

Green

Fruity

Hospital-acquired infections

Neutropenic septicaemia (a whole-body reaction to an infection)

50%

44
Q

What does Burkholderia pseudomallei cause

What is the place in which there are endemic

A

Melioidosis

Southeast Asia and northern Australia; also in China, the Indian subcontinent.

45
Q

What is the incubation period of Burkholderia pseudomallei

A

Incubation period 1-21 days (mean, 9 days).

46
Q

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

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

47
Q

For Neisseria
Are they

What shape?

Gram positive or niggative

What is their result in oxidase test

Name 2 species of Neisseria

A

Dicoccus

Niggative

Positive

N. gonorrhoeae (gonococci)

N. meningitidis (meningococci).

48
Q

What is the function of the pili/fimbriae of the Neisseria

As well as the capsule

Name an endotoxin and what’s its function

A

Pili/fimbriae: Attachment

Capsule: Anti-phagocytic

Lipo-oligosaccharide. As endotoxin and important in adherence, colonisation and activation of immune cell

49
Q

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

A

Reservior: Human. By sexual contact and muscosal contact

Urethritis

Endocervicitis.
Pelvic inflammatory disease

Proctitis
Pharyngitis

Infective endocarditis
Septic Arthritis
Meningitis

Gonococcal ophthalmia neonatorum

50
Q

What agar do we use for Neisseria gonorrhoeae

Does it develop Antitbiotic resistance

A

Thayer-Martin Agar (improved chocolate agar)

Yes

51
Q

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

A

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
52
Q

What can charcoal do in the recovery of Bordetella species

A

Remove the toxins that may be present in the swab or specimen that inhibit the growth of Brodetella Species

53
Q

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

A

Vibrio

No

Positive

Curved bacilli

Yes

Natural water bodies including sea and fresh water

Gastrointestinal tract infection and severe systemic infection

54
Q

What can Shigella cause

What are the 4 species

What is the toxin and what is it’s function

A

bacillary dysentery

S. dysenteriae, S. flexneri, S. boydii, S. sonnei

Inhibits eukaryotic protein synthesis, eventually leading to host cell death.

MBBS IASM (23 decks)

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