4. MICROBIOLOGY Flashcards
1
Q
define a pathogen
A
an organism that is capable of causing disease
2
Q
define an commensal
A
organisms that colonises the host and causes no disease in normal circumstances
3
Q
define virulence/ pathogenicity
A
the degree to which an organism is pathogenic
4
Q
define aymptomatic carriage
A
When a pathogen is carried harmlessly at a tissue site where it causes no disease
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
6
Q
how often do bacteria divide
A
divide every 30-60 minutes
7
Q
describe gram + bacteria structure (3)
A
very thick peptidoglycan cell wall layer
1 membrane: cytoplasmic
lipotechoic acids present on cell wall
8
Q
describe gram - bacteria structure (3)
A
thinner peptidoglycan cell wall layer
2 lipid membranes: cytoplasmic and outer
lipopolysaccharides present on cell wall
9
Q
what shape are majority gram + and - bacteria
A
+ cocci
- bacilli
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)
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
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)
13
Q
what is sabourard agar used for
A
cultures fungi
14
Q
what is lowenstein-jenson agar used for
A
cultures mycobacteria
15
Q
what is macconkey agar used for
A
differentiates lactose fermenting and non-lactose fermenting gram negative bacteria
16
Q
what is CLED used for (2)
A
stops motile protease swarming and also can identify lactose status in gram - bacilli
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
18
Q
give examples of enterobacteriae (4)
A
klebsiella, E. coli, shigella, salmonella
19
Q
where are enterobacteriae infections common
A
infections in healthcare settings
20
Q
what does the mycobacterium cell wall contain
A
lipoarabinomannan
21
Q
what are viruses
A
infectious intracellular parasites
22
Q
are viruses living and what do they require to replicaiton
A
non living, host cell
23
Q
explain viral strucutre 4
A
genetic material surrounded by a protein coat/ membrane
no cell wall or organelles
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
25
what are the 5 viral methods of causing disease
direct destruction
modification
over-reactivity
cell proliferation damage
evasion of host defense
26
explain an example of direct destruction by viruses
polio causes host cell lysis after replication
27
explain an example of modification by viruses
rotavirus atrophies villi
28
explain an example of over-reactivity caused by viruses
chronic hepatitis B causes an immune response that leads to cirrhosis of liver
29
explain an example of cell proliferation caused by viruses
HPV causes overproliferation of cervical endothelial cells=cervical cancer
30
explain an example of evasion of host defence by viruses
varicellular zoster virus= chickenpox can lay dormant and reactivate as shingles
31
what are the two generic treatments for viruses
support as it is often self-resolving
antivirals eg acyclovir
32
what type of virus is HIV and what does this mean
retrovirus
encodes reverse transcriptase and this transcribes RNA to DNA
33
describe the structure inside the HIV envelope 3
HIV envelope includes RNA, capsid and RNA reverse transcriptase
34
how is HIV transmitted? 1
via bodily fluids
35
what does HIV do in the body? 2
infects and lyses CD4+ T cells and macrophages
36
what does HIV lead to and define what this is
leads to AIDs: immunodeficiency which can lead to opportunistic infections
37
what test is done to detect HIV what are the 3 blood markers for a HIV diagnosis
ELISA blood test
HIV Igs, HIV RNA, p24 antigen
38
what is the treatment for HIV and what does it stand for
HAART (highly acting anti-retroviral therapy
39
what are the three ways antibiotics work
inhibits cell wall synthesis
inhibits nucleic acid synthesis
inhibit protein synthesis
40
what do antibiotics that inhibit cell wall synthesis work against well and what are the two types
gram += thick cell walls that they are vulnerable without
beta lactams and glycopeptides
41
give an example of glycopeptides
vancomycin
42
give 3 examples of beta lactams (2,1,1)
penecillin- amoxicillin and flucloxicillin
cephalosporin- cefotaxime
cerbapenams- meropenem
43
what is prescribed to people that are allergic to penecillin
macrolides
44
what are the four types of drugs that inhibit protein synthesis
CHOLERAMPHENICOL, macrolides, tetracyclines, aminoglycosides
45
give 2 examples of macrolides
erythromycin and clarithromycin
46
give an example of tetracyclines
doxycycline
47
give 2 examples of aminoglycosides
gentamicin and streptomycin
48
what are the 4 pharmacological methods of inhibiting nucleic acid synthesis
inhibit folate synthesis, inhibit DNA gyrase, break DNA strand, bind to RNA polymerase
49
what is the contraindication of trimethoprim
pregnancy- as it inhibits folate synthesis, it can cause spina bifida in the foetus
50
what are the two general types of antibiotic resistance
intrinsic and extrinsic
51
what does intrinsic antibiotic resistance mean
naturally resistant bacteria
52
how does extrinsic antibiotic resistance be gained? (2)
spontaneous gene mutations or horizontal gene transfer
53
what is the disadvantage of broad spec antibiotics
promote resistance in gut microbiome
54
how can pathogen genes be acquired by bacteria? (1,3)
horizontal gene transfer (via conjugation, transformation or transduction)
55
what is bacterial conjugation (gene transfer)
sex pilus transfers a plasmid from one bacteria to another
56
what is bacterial transduction (gene transfer)
bacteriophages (viruses invading bacteria) cause bacterial DNA transfer
57
what is bacterial transformation (gene transfer)
bacteria take up free DNA from environment and incorporate into their chromosome
58
what are the bacteria that are resistant to penicillin (example and why)
MRSA
produce beta lactamase
59
explain the mechanism of why MRSA is resistant to beta lactam antibiotics
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
what is a common bacterial resistance mechanism
efflux pumps which pump out antibiotics making them ineffective
61
what is prescribed for staphylococcus infections
flucloxacillin
62
what is the first line of treatment for S pyogenes
amoxicillin (penecillin)
63
what is prescribed for MRSA (1)
vancomycin
64
what is prescribed for C difficile association infections (2)
vancomycin/ metronidazole
65
what is prescribed for UTIs (2)
nitrofuratoin/ trimethoprim
66
what is prescribed for pneumocystis pneumonia
co-trimoxazole
67
what are the 5 C drugs for C difficile
carbapenams
ciprofloxacin
co-amoxiclav
cephalosporins
clindamycin
68
what is prescribed for entamoeba histolytic and giardia
metronidazole
69
what is prescribed for pneumonia
amoxicillin
70
what is the side effect of aminoglycosides
gentamicin causes ototoxicity and renal impairment
71
what does M. tuberculosis stand for
mycobacterium tuberculosis
72
what type of resp mechanism does M. tuberoculosis used
strict aerobe
73
how can M.tuberculosis avoid detection by immune system
live dormant in macrophages for long periods
74
symptoms of tuberculosis (4)
cough, haemoptysis, weight loss, night sweats
75
histological characteristic of M.tuberculosis and what causes this
caseous necrosis
soft cheese appearance of granulomas
76
4 drug treatments of TB and a side effect for each
isoniazide- numb/ tingly extremities
ethambutamol- ocular side effects
rifampicin- orange/red urine
pyranzinamide- arthralgia (joint stiffness)
77
what type of cells are fungi and what type of infections do they cause?
eukaryotes
opportunisitc
78
what is fungal wall composition
chitin and glucan
79
what are the two types of fungi and explain each
yeast- single cells that divide via budding
mould- multicellular hyphae that replicate via spores
80
tell me about treatment for fungi
end in 'azole' eg fluconazole
drugs are usually ineffective as they target cell membrane
81
what is the most pathogenic fungal candida species and what does it cause, rate of death and treatment
candida albicans
causes vaginal and oral infections, sepsis (candidiasis), catheter infections
kills rapidly
treated with antifungals: topical nystatin, oral fluconazole
82
what is the most pathogenic fungal aspergillus species, what does it cause, rate of death, prognosis
aspergillus fumigatus fungus
causes lung infection and allergic disease
kills slowly
poor prognosis
83
what is a helminth
worm
84
what are the 3 types of helminths
nematodes (roundworms)
trematodes (flatworms)
ceratodes/cestatodes (tapeworms)
85
what is the condition for helminth replication
adult worms need a a period of development outside before replicating inside body
86
define a pre-patent period
interval between infection and appearance of eggs/ larvae in stool
87
what type of immune response do helminths induce
induces a poor immune response
mainly IgG and IgE mediated
88
what is a treatment for helminths
mebendazole for hookworm and schistosomiasis
89
what are protozoa and where can they be found
microscopic unicellular eukaryotes
free living or parasitic
90
how are protozoa classified and name 4 classes
classification based on movement: ameoboids, ciliates, sporozoan, flagellates
91
give 4 examples of protozoa
falciparum malaria
trochomonas vaginalis
toxoplasmosis species
giardia
92
what protozoa causes malaria
plasmodium protozoa
93
what are the 5 strains of malaria causing protozoa
P.vivax
P.ovale
P.malariae
P.knowleseii
P.falciparum
94
what strains of plasmodium can go dormant in the human body
P.vivax, P.ovale
95
tell me about P.falciparum
most common and dangerous
causes obstructive microcirculation and cerebral malaria
96
what is the diagnosis of malaria
blood smear and staining
97
what are the symptoms of malaria
aneamia, jaundice, hepatosplenomegaly (simultaneous enlargement of spleen and liver)
98
what are the two treatments for malaria
oral chloroquine and IV artesunate
99
what is the vector and host in the plasmodium life cycle
vector= anopheles mosquito
host= humans and animals
100
what is the route of transmission of malaria
via blood
101
what does plasmodium infect in the human body
infects liver and RBCs
102
when are the 4 times that hands should washed in a healthcare setting
before contact with patient
before aseptic procedures
after contact with patient surroundings
after patient contact
103
when is the Varicella zoster virus present in the body (2)
chickenpox infection
can remain dormant in body and cause shingles in later life
104
symptoms of shingles
red painful rash confined to a single dermatome
105
what does epstein barr virus cause
causes infectious mononucleosis (glandular fever)
106
symptoms of infectious mononucleosis caused by EBV (4)
cough, fever, splenomegaly (enlarged spleen), white/ yellowish purulent lining over the tonsils
107
how is infectious mononucleosis caused by EBV diagnosed (what do positive tests look like)
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
how long do FBC, PCR and ELA serology test results take
FBC- results in few hours
PCR- results next day
serology (ELISA)- results in 1-2 days
109
what are most viral infections diagnosed with and what is an exception
green swab test
infectious mononucleosis caused by EBV
110
what is a differential for infectious mononucleosis caused by EBV, what is common symptoms between the two and how is it eliminated
S.pyogenes throat infection
both present with white/ yellowish purulent lining over the tonsils
black charcoal swab
111
treatment for infectious mononucleosis caused by EBV
supportive therapy of fluids and analgesics
112
what does BALF stand for and what is it
Bronchoalveolar lavage fluid
sample of fluid collected from lungs which is sent off for analysis eg PCR
113
what does CMV stand for and what does it cause
cytomegalovirus
cytomegalovirus colitis
114
what is a unique characteristic on cytomegalovirus colitis and what is its treatment
characteristic owl eye inclusion bodies
treatment is IV ganciclovir (antiviral)
115
what are AIDs defining illnesses
CMV colitis
oral candida (thrush)
lymphomas
PCP (pneumocystitis pneumonia)
116
what is the presentation of meningitis (4)
headaches, fever, photophobia, neck stiffness
117
what samples are taken for suspected meningitis (4)
CSF sample, stool sample, charcoal and green swab of throat
118
what clinically diagnoses meningitis
high white cell count and protein in CSF
