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Belle Phase 2a > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What does an application of safranin do in gram staining?

A

Stains gram negative bacteria PINK

gram positive remain PURPLE

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2
Q

Why does gram positive bacteria remain purple after decolorisation?

A

Thick layer of peptidoglycan in cell wall

Gram negative bacteria have a thin layer of peptidoglycan and a high lipid content

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3
Q

What are the four steps of gram staining?

A

Come In And Stain

Crystal violet (turns all cells purple)
Iodine
Alcohol (decolourisation)
Safranin (gram negative turn pink)

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4
Q

Which gram positive cocci produces an enzyme that converts fibrinogen to fibrin?

A

Staphylococcus aureus and MRSA: produce coagulase

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5
Q

Which test differentiates clusters vs chains in gram positive cocci?

A

Catalase test
Positive: Staphylococcus (clusters)
Negative: Streptococcus (chains)

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6
Q

Which groups does a haemolysis test differentiate streptococcus into?

A

Alpha: partial lysis (green)
Beta (Lancefield A, B,C + G): complete lysis (clear)
Gamma (Lancefield D): no lysis (non haem)

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7
Q

Which test can be used to differentiate alpha haemolytic streptococci?

A

Optochin test
Resistant: viridans strep
Sensitive: s. pneumoniae

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8
Q

Name two alpha haemolytic streptococci

A

Streptococcus pneumoniae

Viridans group streptococci

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9
Q

Which gram positive bacteria is beta haem group A?

A

Streptococcus pyogenes

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10
Q

Which gram positive bacteria are non-haem Group D?

A

Streptococcus bovis

Enterococcus

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11
Q

Infections associated with staphylococcus epidermidis

A

Surgical wound infections
Septicaemia
Endocarditis (prosthetic valve)

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12
Q

Infections associated with streptococcus pneumoniae

A

Pneumonia
Meningitis
Otitis media
Sinusitis

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13
Q

Treatment of MRSA infection

A

Vancomycin

Methicillin resistant s. aureus = MRSA

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14
Q

Test to initially differentiate gram negative bacilli

A

MacConkey Agar
Lactose fermenting: pink
Non lactose fermenting: white

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15
Q

Lactose fermenting gram negative bacilli

A

E. Coli

Klebsiella

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16
Q

Non lactose fermenting gram negative bacilli

A

Shigella
Salmonella
Pseudomonas

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17
Q

Oxidase positive non lactose fermenting gram negative bacilli

A

Pseudomonas

Produce cytochrome c oxidases

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18
Q

Oxidase negative non lactose fermenting gram negative bacilli

A

Shigella

Salmonella

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19
Q

Infections associated with E. Coli

A

UTIs (causes the majority)
Travellers diarrhoea
Cholecystitis
Cholangitis

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20
Q

Infections associated with pseudomonas and treatment

A

Skin infections
Pneumonia

Treatment: gentamicin, quinolones

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21
Q

Infections associated with shigella and treatment

A

Shigellosis (diarrhoea, fever)

Treatment: quinolones, azithromycin

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22
Q

Infections associated with neisseria and treatment

A

Gonorrhoea
Meningitis

Treatment: cephalosporins

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23
Q

Two examples of mycobacteria

A

TB

Leprosy

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24
Q

Stain used for mycobacteria

A

Ziehl-Nielsen stain
Acid fast bacteria: red
Non-acid fast: blue

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25
Four different ways viruses can cause disease and examples of diseases for each
Direct destruction e.g. polio Modification e.g. rotavirus Over-reactivity e.g. hepatitis B Cell proliferation e.g. HPV
26
3 tests used for identification of viruses
PCR Nucleic acid amplification tests (NAAT) Serology (acute: IgM, IgG appears later)
27
Worms
Common worldwide but rare in the UK 3 groups: roundworms (nematodes), flatworms (trematodes), tapeworms (ceratodes) Mainly IgG and IgE mediated Example: hookworm
28
Listeria monocytogenes
Gram positive bacilli | Pregnant women at high risk of this cause of MENINGITIS 🤰🏼
29
Haemophilus influenza
Gram negative coccobacilli | Aerobic
30
Mechanism of action of glycopeptides and example AB
Inhibit cell wall synthesis Vancomycin
31
Mechanism of action of beta lactams and example groups
Inhibit cell wall synthesis Penicillins, cephalosporins
32
Three examples of penicillins
Amoxicillin Benzylpenicillin Flucloxacillin
33
Example of cephalosporins
Cephalexin Cefotaxime Ceftriaxone
34
Alternative AB used in the case of penicillin allergy
Macrolides e.g. erythromycin
35
Mechanism of action of macrolides
Inhibit protein synthesis by targeting bacterial ribosome (50S subunit)
36
Mechanism of action of aminoglycosides and example
Inhibit protein synthesis by targeting bacterial ribosome (30S) Gentamicin
37
Mechanism of action of tetracyclines and example
Inhibit protein synthesis by targeting bacterial ribosome (30S) Doxycycline
38
When is trimethoprim contraindicated
Pregnancy (folate is important in preventing spina bifida)
39
Mechanism of action of trimethoprim
Inhibit folate synthesis (inhibits nucleic acid synthesis)
40
Mechanism of action of fluroquinolones and example
Inhibit DNA gyrase (inhibits nucleic acid synthesis) Ciprofloxacin
41
Gold standard treatment for Staphylococcus infection
Flucloxacillin
42
Two first line treatments for lower UTIs
Nitrofurantoin | Trimethoprim
43
Two important bacterial resistance types
MRSA (methicillin) | VRE (vancomycin)
44
Hepatitis B testing
1) Total anti-HB total core antibody = IgM + IgG - Exposed to virus 2) Hepatitis B surface antigen (sAg) - Exposed to virus AND it’s still active 3) Anti-HB surface antibody (sAb) - Immunity to virus
45
Which hepatitis viruses have a vaccine?
A and B | THERE IS NO VACCINE FOR HEPATITIS C
46
Hepatitis C treatment
Direct acting antiviral therapy (successfully cure 90% of patients)
47
Streptococcal treatment
E.g. Strep throat | Penicillin e.g. amoxicillin
48
Enteric infection
Microorganisms that cause intestinal illness
49
Causative organism of osteomyelitis
staphylococcus aureus
50
Endocarditis symptoms
Fever, anaemia, murmur, breathlessness, chest pain
51
Uncomplicated UTI criteria
Non-pregnant women
52
Pyelonephritis triad
Loin pain + fever + pyuria (WCC)
53
Complicated UTIs Mx
Empirical antibiotics first Urinalysis Blood culture
54
Skin and soft tissue infection causative organisms and Tx
Beta haemolytic strep (Strep pyogenes): amoxicillin Staph Aureus: flucloxacillin
55
Three major classes of antibiotics
Inhibit cell wall synthesis Inhibit nucleic acid synthesis (folate, DNA, RNA) Inhibit protein synthesis (30S and 50S ribosomal subunits)
56
Mechanism of antimicrobial resistance in MRSA
Flucloxacillin and methicillin are no longer able to bind to the PBP (penicillin binding protein) of staphylococci
57
Mechanism of antimicrobial resistance in VRE
change in cell wall components reduce vancomycin binding
58
Which type of bacteria are intrinsically resistant to metronidazole and why
Aerobic bacteria | Unable to convert it to its active form
59
Which type of bacteria are intrinsically resistant to vancomycin and why
Gram negative bacteria | Vancomycin cannot penetrate its outer membrane
60
Streptococcal pharyngitis
Throat inflammation caused by streptococcus pyogenes (strep throat) - Group A Beta-haemolytic
61
Streptolysin
Enzyme that completely lyses RBC (Beta haemolysis)
62
RBCs in alpha haemolysis
Damaged RBCs (NOT ruptured)
63
Rheumatic fever microbiology/pathophysiology
Group A Beta-haem streptococci M protein (antibody) from the strep cell wall cross reacts with tissue causing inflammation and damage E.g. to heart valves
64
Rheumatic fever symptoms
``` Fever Arthritis (painful, tender joints) Chest pain SoB Fatigue Chorea ```
65
AB table
66
Cell wall synthesis disruption two mechanisms
``` Peptidoglycan cross-linking (Beta lactams) Peptidoglycan synthesis (Glycopeptides e.g. vancomycin) ```
67
Folic acid synthesis disruption example Ab
Trimethoprim
68
Pseudomembranous colitis is a complication of which microorganism?
Clostridium Difficile local inflammation of large intestine = significant diarrhoea
69
Treatment given to patients with suspected meningococcal septicaemia in the COMMUNITY
Benzylpenicillin IM
70
Meningitis hospital Tx
Cefotaxime IV
71
TB risk factors
``` Ethnicity IVDU homeless Immunosuppression Alcoholic Close contact with infected ```
72
Prophylaxis against meningococcal meningitis for close contacts
Ciprofloxacin

Belle Phase 2a (14 decks)

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