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Microbiology Flashcards

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1
Q

What are the three classifications of life?

A

Eubacteria, archaea, eukaryotes

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2
Q

Which classifications of life do bacteria, viruses, fungi, and protozoa fall into?

A

Eubacteria, archaea, eukaryotes x2

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3
Q

Which two external structures are present only in bacteria and what are their purposes?

A

Fimbrae - attachment, flagella - movement

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4
Q

Describe the storage of genetic information in the bacteria.

A

One large bacterial chromosome, several smaller plasmids

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5
Q

What is the ideal pH growth range for bacteria?

A

6.8 - 7.2

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6
Q

Osmotic protection - what is the ideal concentration of NaCl for growth of bacteria?

A

0.85%

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7
Q

What are the four phases of bacterial growth?

A

Lag, exponential, stationary, decline

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8
Q

What is a biofilm?

A

A community of bacteria that has a more sophisticated culture

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9
Q

Which aspect of bacteria form biofilms?

A

Pillae

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10
Q

What is the difference between aerobic and anaerobic bacteria (except that one uses oxygen)?

A

Electron acceptors - aerobic use oxygen, anaerobic use e.g. nitrogen

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11
Q

Define facultative and capnophilic bacteria types.

A

Tolerates O2, prefers CO2

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12
Q

What are the three main shapes of bacteria?

A

Cocci (spheres), bacilli (rods), spirillum/spirochete/fusiform (spiral shaped)

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13
Q

Describe what can be ascertained from the results of a gram stain test, and how.

A

The gram stain type - piNk is negative, purPle is positive

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14
Q

Which pathogen is tested for using haemolysis?

A

Streptococcus

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15
Q

What are the three types of haemolysis and what do they show?

A

Alpha - greening, beta - yellow halo, gamma - N/A

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16
Q

Which Lancefield groups of streptococcus are shown by haemolysis?

A

Alpha - D, Beta - A, B, C, F, G

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17
Q

What is the coagulase test? Which bacteria tests positive?

A

Tests for the presence of the enzyme coagulase - staph aureus

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18
Q

What is the catalase test? Which bacteria tests positive?

A

Tests for the enzyme catalase, which breaks down H2O2. Staphylococcus

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19
Q

What is the Ziehl Neelsen stain used for, and which pathogen in particular shows +ve?

A

Seperates acid fast from acid slow. Mycobacterium tuberculosis.

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20
Q

What is selective media?

A

Allows the growth of one bacteria over another.

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21
Q

What is differential media?

A

Visible changes in colonies allow identification.

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22
Q

Bacilli and vibrio bacteria are which shape?

A

Rods

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23
Q

Serological tests use which primary type of cell?

A

Antibodies

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24
Q

Describe the mechanism of the agglutination test.

A

Provides heavy cells which clump together if the particular pathogen is present - binds to antigen

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25
Which type of test is ELIZA?
Serological
26
What is PCR?
Polymerase chain reaction - provides primers specific for the pathogen's DNA to provide many copies
27
What is the difference between PCR and qPCR?
qPCR is viral - i.e. uses reverse transcriptase
28
Describe multi-locase sequence type.
Increases the resolution, and allows entire genome sequencing.
29
What does MALDI-TOF stand for?
Matrix assisted laser desorption/ionization - time of flight
30
Describe briefly the mechanism of MALDI-TOF.
Based on the m/q ratio. Splits into charged mass fragments which alters time of flight.
31
Which bacteria is MALDI-TOF NOT good for?
Staph and strep
32
Name the four main requested specific microbiology tests.
Blood culture, urine culture, faeces culture, swab of pus.
33
What is virulence?
Capacity to cause harm
34
What are commensal organisms?
'Symbiotic' endogenous organisms which live on the skin/body
35
What is an opportunistic pathogen?
A pathogen which takes advantage of a change of circumstance i.e HIV
36
Describe the structure of the gram positive cell wall.
Cell membrane with thick layers of peptidoglycan
37
Describe the structure of the gram negative cell wall.
Two cell membranes, separated by peptidoglycan. Lipopolysaccharide is present on outer membrane
38
Which types of antibiotic target bacterial DNA?
Gyrases
39
Which types of antibiotic target the cell wall?
Penicillins and glycopeptides
40
Which types of antibiotic target the ribosome?
Protein synthesis inhibitors
41
Which types of antibiotic target the cell membrane?
Sonication, ethanol
42
What is beta-lactam?
A molecule which blocks the cross-links in the cell wall
43
What is the difference between bacteriostatic and bacteriocidal?
Bacteriostatic inhibits growth, bacteriocidal kills bacteria
44
What is meant by synergistic effects of antibiotics?
They multiply (i.e. 1 + 1 = 3)
45
Why can broad spectrum antibiotics be bad in the elderly?
Increases risk of C. diff
46
What are the three types of protozoa?
Amoeba, plasmodia, toxoplasmodia
47
Which type (shape) of bacteria are coliforms?
Bacilli (rods)
48
What gram stain is shown by coliforms?
Negative
49
Describe when coliforms can be dangerous.
When they infect a sterile site.
50
Coliforms contain two types of toxin. Describe them.
Endotoxins are parts of the cell wall that break off. Exotoxins are produced inside the cell and released.
51
Endotoxins and exotoxins can be divided into two main types. What are these and what do they cause?
Prostaglandin E - fever. Cytokines - inflammation.
52
Name two of the main beta-haemolytic streptococci.
Agalactase, pyogenes
53
Name two of the main alpha-haemolytic streptococci.
Viridans, pneumoniae
54
Name the main gamma-haemolytic streptococcus.
Enterococcus
55
What is tropism?
The range of hosts a virus can infect
56
How may a virus enter a cell?
Fusion of membranes, or endocytosis
57
How are viral proteins assembled in a cell?
Own viral enzymes (protease), host ribosomes, reverse transcriptase
58
How may viral fragments leave a cell?
Budding or lysis
59
What is the name for the class of drugs which may affect viruses and bacteria?
Antimicrobials
60
What is a convalescent viral infection?
One where there are no symptoms
61
What is the main effect of continuous activation of the immune system by viruses? What's dangerous about this?
Chronic inflammation - asymptomatic, infectious, and life threatening.
62
Which newer tests may be used to detect viruses?
PCR, serology, mass spectroscopy
63
B-lactam antibiotics include which four subtypes?
Penicillins, cephalosporins, carbapenems, monobactams
64
Describe the mechanism of beta-lactam drugs.
A suicide substrate - resembles D-alanine D-alanine. Binds irreversibly and blocks cross links
65
Which two types of antibiotic target the cell wall?
B-lactams and glycopeptides
66
Which are the two main types of glycopeptides?
Vancomycin, teloplanin
67
What are the major positives and negatives of the glycopeptides?
Treats MRSA, toxic buildup in kidney can cause failure, +ve only.
68
Which are the good points about the penicillins?
Safe, effective, and flexible. Rapid excretion.
69
Which are the bad points about the penicillins?
Resistance, hypersensitivity
70
Which is the standard penicillin of choice for most general treatments?
Amoxicillin
71
Which antibiotic is used in skin infections and why?
Flucloxacillin - targets +ve (narrow range), i.e. staph and strep
72
What is co-amoxiclav?
Amoxicillin with clavulanic acid. A beta-lactam and beta-lactamase inhibitor.
73
Which IV penicillin antibiotics are used in extreme infection? Why?
Temocillin - it is beta-lactamase and ESBL resistant. Piperacillin may also be used.
74
Which long lasting penicillin is used intramuscularly?
Benzathine
75
Name the 8 main penicillin types.
Amoxicillin, flucloxacillin, benzathine, piperacillin, temocillin, phenoxymethylpenicillin, co-amoxiclav, benzylpenicillin
76
Give an account of the cephalosporins.
Broad spec and bacteriocidal, but encourage growth of c. diff. Rarely used in Tayside
77
Which drugs are mainly bacteriostatic?
Tetracyclines, macrolides
78
Name the macrolides.
Clarithromycin, azithromycin, erythromycin
79
Name the two main bacteriocial antibiotics (excluding the B-lactams).
Aminoglycosides, gentamicin
80
Why must blood levels of gentamicin regularly be monitored?
To avoid toxic buildup.
81
Describe some methods of natural bacterial resistance.
Target isn't present (i.e. no cell wall), not accessible, or different metabolism (anaerobic/aerobic)
82
Which community of bacteria are particularly resistant to antibiotics? Which particular cell types?
Biofilms, persistor cells
83
Which three main methods are encouraging antibiotic resistance?
Unneccessary doses, sub-optimal doses, selection pressure
84
Bacteria can alter their permeability, to avoid antibiotics. Give the main methods of this.
Alters influx (reducing OmPF), alters efflux (pump i.e. tetracycline)
85
Which enzymes form the B-lactamases?
Penicillinase, cephalosporinase
86
Which enzymes form the ESBLs?
Carbapenamase, monobactamase, serine/metalloenzymes
87
Which two enzymes are the main metalloenzymes?
New Delhi metallo-B lactamase 1, collastin
88
How can bacteria transfer their genes?
Naturally, bacteriophage, sex pilli
89
Which antibiotics affect folic acid synthesis?
Sulphonamides, trimethoprim
90
Which antibiotics affect DNA gyrases?
Quinolones, fluroquinolones
91
Which drug affects DNA replication in bacteria?
Metronidazole

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