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2A content- Sameera > 4. MICROBIOLOGY > Flashcards

4. MICROBIOLOGY Flashcards

1
Q

define a pathogen

A

an organism that is capable of causing disease

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2
Q

define an commensal

A

organisms that colonises the host and causes no disease in normal circumstances

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3
Q

define virulence/ pathogenicity

A

the degree to which an organism is pathogenic

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4
Q

define aymptomatic carriage

A

When a pathogen is carried harmlessly at a tissue site where it causes no disease

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5
Q

define opportunistic pathogen and what type of people does it occur in

A

pathogen that only causes disease if host defences are compromised
immunocompromised or damaged host defense

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6
Q

how often do bacteria divide

A

divide every 30-60 minutes

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7
Q

describe gram + bacteria structure (3)

A

very thick peptidoglycan cell wall layer
1 membrane: cytoplasmic
lipotechoic acids present on cell wall

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8
Q

describe gram - bacteria structure (3)

A

thinner peptidoglycan cell wall layer
2 lipid membranes: cytoplasmic and outer
lipopolysaccharides present on cell wall

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9
Q

what shape are majority gram + and - bacteria

A

+ cocci
- bacilli

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10
Q

what is blood agar and what specific test is it used for

A

sheep/ horse blood
haemolytic test to determine the type of streptococcus (alpha/beta/gamma)

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11
Q

what is chocolate agar and what is it used for and give an example of bacteria that grows on this

A

lood agar heated to 80’C for 5 minutes
allows fastidious (fussy) bacteria to grow eg Neisseria gonorrhoea

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12
Q

what two bacteria does XLD differentiate between and what type of bacteria r both of these

A

differentiates between salmonella and shigella (non-lactose fermenting gram neg bacilli)

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13
Q

what is sabourard agar used for

A

cultures fungi

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14
Q

what is lowenstein-jenson agar used for

A

cultures mycobacteria

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15
Q

what is macconkey agar used for

A

differentiates lactose fermenting and non-lactose fermenting gram negative bacteria

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16
Q

what is CLED used for (2)

A

stops motile protease swarming and also can identify lactose status in gram - bacilli

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17
Q

what are enterobacteriae and where can they be found in the human

A

gram negative anaerobic bacilli
found as a normal part of the gut flora

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18
Q

give examples of enterobacteriae (4)

A

klebsiella, E. coli, shigella, salmonella

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19
Q

where are enterobacteriae infections common

A

infections in healthcare settings

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20
Q

what does the mycobacterium cell wall contain

A

lipoarabinomannan

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21
Q

what are viruses

A

infectious intracellular parasites

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22
Q

are viruses living and what do they require to replicaiton

A

non living, host cell

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23
Q

explain viral strucutre 4

A

genetic material surrounded by a protein coat/ membrane
no cell wall or organelles

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24
Q

explain four step of viral life cycle

A

attaches to host cell membrane
enters the cell and ejects genome
genome is transcripted and translation and assembled
the new virus is assembled and then exits the cell

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25
Q

what are the 5 viral methods of causing disease

A

direct destruction
modification
over-reactivity
cell proliferation damage
evasion of host defense

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26
Q

explain an example of direct destruction by viruses

A

polio causes host cell lysis after replication

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27
Q

explain an example of modification by viruses

A

rotavirus atrophies villi

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28
Q

explain an example of over-reactivity caused by viruses

A

chronic hepatitis B causes an immune response that leads to cirrhosis of liver

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29
Q

explain an example of cell proliferation caused by viruses

A

HPV causes overproliferation of cervical endothelial cells=cervical cancer

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30
Q

explain an example of evasion of host defence by viruses

A

varicellular zoster virus= chickenpox can lay dormant and reactivate as shingles

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31
Q

what are the two generic treatments for viruses

A

support as it is often self-resolving
antivirals eg acyclovir

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32
Q

what type of virus is HIV and what does this mean

A

retrovirus
encodes reverse transcriptase and this transcribes RNA to DNA

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33
Q

describe the structure inside the HIV envelope 3

A

HIV envelope includes RNA, capsid and RNA reverse transcriptase

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34
Q

how is HIV transmitted? 1

A

via bodily fluids

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35
Q

what does HIV do in the body? 2

A

infects and lyses CD4+ T cells and macrophages

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36
Q

what does HIV lead to and define what this is

A

leads to AIDs: immunodeficiency which can lead to opportunistic infections

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37
Q

what test is done to detect HIV what are the 3 blood markers for a HIV diagnosis

A

ELISA blood test
HIV Igs, HIV RNA, p24 antigen

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38
Q

what is the treatment for HIV and what does it stand for

A

HAART (highly acting anti-retroviral therapy

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39
Q

what are the three ways antibiotics work

A

inhibits cell wall synthesis
inhibits nucleic acid synthesis
inhibit protein synthesis

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40
Q

what do antibiotics that inhibit cell wall synthesis work against well and what are the two types

A

gram += thick cell walls that they are vulnerable without
beta lactams and glycopeptides

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41
Q

give an example of glycopeptides

A

vancomycin

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42
Q

give 3 examples of beta lactams (2,1,1)

A

penecillin- amoxicillin and flucloxicillin
cephalosporin- cefotaxime
cerbapenams- meropenem

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43
Q

what is prescribed to people that are allergic to penecillin

A

macrolides

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44
Q

what are the four types of drugs that inhibit protein synthesis

A

CHOLERAMPHENICOL, macrolides, tetracyclines, aminoglycosides

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45
Q

give 2 examples of macrolides

A

erythromycin and clarithromycin

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46
Q

give an example of tetracyclines

A

doxycycline

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47
Q

give 2 examples of aminoglycosides

A

gentamicin and streptomycin

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48
Q

what are the 4 pharmacological methods of inhibiting nucleic acid synthesis

A

inhibit folate synthesis, inhibit DNA gyrase, break DNA strand, bind to RNA polymerase

49
Q

what is the contraindication of trimethoprim

A

pregnancy- as it inhibits folate synthesis, it can cause spina bifida in the foetus

50
Q

what are the two general types of antibiotic resistance

A

intrinsic and extrinsic

51
Q

what does intrinsic antibiotic resistance mean

A

naturally resistant bacteria

52
Q

how does extrinsic antibiotic resistance be gained? (2)

A

spontaneous gene mutations or horizontal gene transfer

53
Q

what is the disadvantage of broad spec antibiotics

A

promote resistance in gut microbiome

54
Q

how can pathogen genes be acquired by bacteria? (1,3)

A

horizontal gene transfer (via conjugation, transformation or transduction)

55
Q

what is bacterial conjugation (gene transfer)

A

sex pilus transfers a plasmid from one bacteria to another

56
Q

what is bacterial transduction (gene transfer)

A

bacteriophages (viruses invading bacteria) cause bacterial DNA transfer

57
Q

what is bacterial transformation (gene transfer)

A

bacteria take up free DNA from environment and incorporate into their chromosome

58
Q

what are the bacteria that are resistant to penicillin (example and why)

A

MRSA
produce beta lactamase

59
Q

explain the mechanism of why MRSA is resistant to beta lactam antibiotics

A

MRSA carries a gene called mecA that is a transpeptidase that is not inhibited by beta lactam antibiotics so MRSA cam continue peptidoglycan crosslinking because it is resistant

60
Q

what is a common bacterial resistance mechanism

A

efflux pumps which pump out antibiotics making them ineffective

61
Q

what is prescribed for staphylococcus infections

A

flucloxacillin

62
Q

what is the first line of treatment for S pyogenes

A

amoxicillin (penecillin)

63
Q

what is prescribed for MRSA (1)

A

vancomycin

64
Q

what is prescribed for C difficile association infections (2)

A

vancomycin/ metronidazole

65
Q

what is prescribed for UTIs (2)

A

nitrofuratoin/ trimethoprim

66
Q

what is prescribed for pneumocystis pneumonia

A

co-trimoxazole

67
Q

what are the 5 C drugs for C difficile

A

carbapenams
ciprofloxacin
co-amoxiclav
cephalosporins
clindamycin

68
Q

what is prescribed for entamoeba histolytic and giardia

A

metronidazole

69
Q

what is prescribed for pneumonia

A

amoxicillin

70
Q

what is the side effect of aminoglycosides

A

gentamicin causes ototoxicity and renal impairment

71
Q

what does M. tuberculosis stand for

A

mycobacterium tuberculosis

72
Q

what type of resp mechanism does M. tuberoculosis used

A

strict aerobe

73
Q

how can M.tuberculosis avoid detection by immune system

A

live dormant in macrophages for long periods

74
Q

symptoms of tuberculosis (4)

A

cough, haemoptysis, weight loss, night sweats

75
Q

histological characteristic of M.tuberculosis and what causes this

A

caseous necrosis
soft cheese appearance of granulomas

76
Q

4 drug treatments of TB and a side effect for each

A

isoniazide- numb/ tingly extremities
ethambutamol- ocular side effects
rifampicin- orange/red urine
pyranzinamide- arthralgia (joint stiffness)

77
Q

what type of cells are fungi and what type of infections do they cause?

A

eukaryotes
opportunisitc

78
Q

what is fungal wall composition

A

chitin and glucan

79
Q

what are the two types of fungi and explain each

A

yeast- single cells that divide via budding
mould- multicellular hyphae that replicate via spores

80
Q

tell me about treatment for fungi

A

end in ‘azole’ eg fluconazole
drugs are usually ineffective as they target cell membrane

81
Q

what is the most pathogenic fungal candida species and what does it cause, rate of death and treatment

A

candida albicans
causes vaginal and oral infections, sepsis (candidiasis), catheter infections
kills rapidly
treated with antifungals: topical nystatin, oral fluconazole

82
Q

what is the most pathogenic fungal aspergillus species, what does it cause, rate of death, prognosis

A

aspergillus fumigatus fungus
causes lung infection and allergic disease
kills slowly
poor prognosis

83
Q

what is a helminth

A

worm

84
Q

what are the 3 types of helminths

A

nematodes (roundworms)
trematodes (flatworms)
ceratodes/cestatodes (tapeworms)

85
Q

what is the condition for helminth replication

A

adult worms need a a period of development outside before replicating inside body

86
Q

define a pre-patent period

A

interval between infection and appearance of eggs/ larvae in stool

87
Q

what type of immune response do helminths induce

A

induces a poor immune response
mainly IgG and IgE mediated

88
Q

what is a treatment for helminths

A

mebendazole for hookworm and schistosomiasis

89
Q

what are protozoa and where can they be found

A

microscopic unicellular eukaryotes
free living or parasitic

90
Q

how are protozoa classified and name 4 classes

A

classification based on movement: ameoboids, ciliates, sporozoan, flagellates

91
Q

give 4 examples of protozoa

A

falciparum malaria
trochomonas vaginalis
toxoplasmosis species
giardia

92
Q

what protozoa causes malaria

A

plasmodium protozoa

93
Q

what are the 5 strains of malaria causing protozoa

A

P.vivax
P.ovale
P.malariae
P.knowleseii
P.falciparum

94
Q

what strains of plasmodium can go dormant in the human body

A

P.vivax, P.ovale

95
Q

tell me about P.falciparum

A

most common and dangerous
causes obstructive microcirculation and cerebral malaria

96
Q

what is the diagnosis of malaria

A

blood smear and staining

97
Q

what are the symptoms of malaria

A

aneamia, jaundice, hepatosplenomegaly (simultaneous enlargement of spleen and liver)

98
Q

what are the two treatments for malaria

A

oral chloroquine and IV artesunate

99
Q

what is the vector and host in the plasmodium life cycle

A

vector= anopheles mosquito
host= humans and animals

100
Q

what is the route of transmission of malaria

A

via blood

101
Q

what does plasmodium infect in the human body

A

infects liver and RBCs

102
Q

when are the 4 times that hands should washed in a healthcare setting

A

before contact with patient
before aseptic procedures
after contact with patient surroundings
after patient contact

103
Q

when is the Varicella zoster virus present in the body (2)

A

chickenpox infection
can remain dormant in body and cause shingles in later life

104
Q

symptoms of shingles

A

red painful rash confined to a single dermatome

105
Q

what does epstein barr virus cause

A

causes infectious mononucleosis (glandular fever)

106
Q

symptoms of infectious mononucleosis caused by EBV (4)

A

cough, fever, splenomegaly (enlarged spleen), white/ yellowish purulent lining over the tonsils

107
Q

how is infectious mononucleosis caused by EBV diagnosed (what do positive tests look like)

A

FBC should show atypical lymphocytes (basophilic cytoplasm and prominent nucleolus)
serology for EBC immunoglobulins should have a clotted sample (ELISA test has IgM positive) and this can diagnose a patient with acute EBV

108
Q

how long do FBC, PCR and ELA serology test results take

A

FBC- results in few hours
PCR- results next day
serology (ELISA)- results in 1-2 days

109
Q

what are most viral infections diagnosed with and what is an exception

A

green swab test
infectious mononucleosis caused by EBV

110
Q

what is a differential for infectious mononucleosis caused by EBV, what is common symptoms between the two and how is it eliminated

A

S.pyogenes throat infection
both present with white/ yellowish purulent lining over the tonsils
black charcoal swab

111
Q

treatment for infectious mononucleosis caused by EBV

A

supportive therapy of fluids and analgesics

112
Q

what does BALF stand for and what is it

A

Bronchoalveolar lavage fluid
sample of fluid collected from lungs which is sent off for analysis eg PCR

113
Q

what does CMV stand for and what does it cause

A

cytomegalovirus
cytomegalovirus colitis

114
Q

what is a unique characteristic on cytomegalovirus colitis and what is its treatment

A

characteristic owl eye inclusion bodies
treatment is IV ganciclovir (antiviral)

115
Q

what are AIDs defining illnesses

A

CMV colitis
oral candida (thrush)
lymphomas
PCP (pneumocystitis pneumonia)

116
Q

what is the presentation of meningitis (4)

A

headaches, fever, photophobia, neck stiffness

117
Q

what samples are taken for suspected meningitis (4)

A

CSF sample, stool sample, charcoal and green swab of throat

118
Q

what clinically diagnoses meningitis

A

high white cell count and protein in CSF

2A content- Sameera (21 decks)

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