1 Core Microbiology Flashcards
(102 cards)
1
Q
What are antibiotics?
A
Chemical products of microbes that inhibit or kill other organisms
2
Q
What are antimicrobial agents?
A
drugs: antibacterial, antifungal or antiviral
3
Q
What does bacteriastatic mean?
A
inhibits bacterial growth which enables them to be killed e.g. protein synthesis inhibitors
4
Q
What does bactericidal mean?
A
kill bacteira
5
Q
What is the MIC?
A
Minimum inhibitory concentration. minimum concentration of antibiotic at which visible growth is inhibited
6
Q
What is synergism?
A
Activity of two anti-microbials given together is given together is greater than the sum of their activity if given separately e.g. combination of beta-lactam/aminoglycoside combination therapy of streptococcal endocarditis
7
Q
What is antagonism?
A
one agent diminishes the activity of another
8
Q
What is indifference?
A
Activity unaffected by the addition of another agent
9
Q
How do antibacterials work?
A
inhibit critical processes in the cell
10
Q
What are the 5 antibiotic targets?
A
cell wall protein synthesis on bacteria DNA synthesis RNA synthesis Plasma membrane
11
Q
What is targeted on the cell wall by antibiotics?
A
peptidoglycan: both gram negative and positive. It is a polymer of glucose derivatives: N-acetyl muramic acid (NAM) and N-acetyl glucosamine (NAG)
12
Q
What are cell wall synthesis inhibitors and give examples?
A
B-lactams:
penicillins, cephalosporins, carbapenems, monobactams
Glycopeptidases:
vancomycin, teicoplanim
13
Q
How do B lactams and glycopeptidases work on the cell wall?
A
interfere with transpeptidses which are involved in peptidoglycan cross linking
14
Q
How is protein synthesis affected in bacteria?
A
translation of RNA is targeted
50S and 30S subunit form a 70S initiation complex on the mRNA
15
Q
What are protein synthesis inhibitors?
A
Aminoglycosides- gentamicin Macrolides (erythromycin), lincosamides, streptogramins (MLS) Tetracyclines Oxazolidinones (linezolid) Mupirosin Fusidic acid
16
Q
What are DNA synthesis inhibitors?
A
Trimethoprim and sulfonamides (combines is co-trimoxazole)
Quinolones and fluoroquinolones
17
Q
What is a RNA synthesis inhibitor and how does it work?
A
Rifampicin. It is an RNA polymerase inhibitor and prevents the synthesis of mRNA
18
Q
What destroys the plasma membrane?
A
Colistin and daptomycin
19
Q
What are adverse effects of aminoglycosides?
A
reversible renal impairment on accumulation
irreversible ototoxicity on accumulation
20
Q
What are the adverse effects if B-lactams?
A
main problems: allergic reactions
21
Q
What is the adverse effect of linezolid?
A
bone marrow depression if used for along period
22
Q
What B lactam is safe to use in someone with a penicillin allergy?
A
a non-severe: cephalosporins and carbapenems
any allergy: aztreonam
23
Q
What are the common precipitating antibiotics that cause Clostridium Difficile?
A
co-amoxiclav
cephalosporins
ciprofloxacin
clindamycin
24
Q
What are 7 key antibiotic-bacteria combinations?
A
flucloxacillin- staphylococcus aureus (not MRSA)
benzylpenicillin- streptococcus pyogenes
cephalosporins- gram negative bacilli
metronidazole- anaerobes
vancomycin- gram positive (MRSA)
meropenem- most clinically-relevant bacteria
colistin- last option for multi-resistant gram negatives
25
What reasons are there for combining antibiotics?
- increase efficacy
- provide adequately broad spectrum
- reduce resistance
26
What are the risks of empiric therapy?
risk of under treatment
| risk of excessively broad spectrum
27
What are the disadvantages of targeted therapy?
alternative may be:
expensive - linezolid, tigecycline, daptomycin vs. flucloxacillin for MRSA
last line - meropenem vs. ciprofloxacin for multi-resistant enterobacteriaceae
toxic - colistin vs. meropem for NDM-1 producers
28
What is sensitivity testing and what are some of the advantages?
Culture of micro-organisms in the presence of antimicrobial agent: solid or liquid media
adv:
-enables targeted therapy over empiric
-explains treatment failures
-provides alternative antibiotics in case of treatment failure or intolerance/adverse effects
-provides alternative oral antibiotics if IV is not longer required
29
What are 6 resistance mechanisms?
- no target
- reduced permeability
- altered target
- over-expression of target
- enzymatic degradation
- efflux pump
30
Give 2 examples of reduced permeability?
- gram negatives have an outer membrane that is impermeable to vancomycin
- anaerobic organisms and gentamicin because uptake of aminoglycosides requires requires an O2 dependent active transport mechanism
31
Explain target alteration and give examples
target modified by single gene mutation so the antibiotic can't interact with the target anymore
flucloxacillin: MRSA -altered penicillin-binding proetin (PBP2' encoded by Mec A) does not bind B lactams
vancomycin: VRE- altered peptide sequence in gram pos peptodoglycan (D-ala D-ala to D-ala D-lac)
Trimethoprim: gram negative bacilli- mutations in dihydrofolate reductase gene
32
Explain enzymatic degradation and give examples
The drug is destroyed: the antibiotic gets into the cell but is attacked by an enzyme
penicillins and cephalosporins: B lactamases (includinging ESBLs and NDM-1)
gentamicin: aminoglycoside modifying enzymes
chlorampheniol: chloramphnicol acetyltransferae (CAT)
33
Where is resistance genes encoded in bacteria and how is it transferred?
resistance genes are encoded in plasmids
| horizontal and vertical transfer
34
What is horizontal transfer of resistance?
- enabled by transposons and integrons
| - DNA sequences designed to be transferred from plasmid to plasmid or plasmid to chromosome
35
What is vertical transfer of resistance?
chromosomal or plasmid-born resistance gene transferred to daughter cells on bacterial cell-division
36
Which viral infections cause the child to present with a rash?
- Parvovirus
- Measles
- Chickenpox
- Rubella
- Non-polio enterovirus infection
- Glandular fever (more likely to get a rash if taken ampicillin. May think you're allergic to penicillin)
37
What is the term for the measles virus?
Paramyxovirus
| Enveloped single stranded RNA virus
38
What are the clinical features of measles?
Rash, Fever, Cough/coryza/conjunctivitis
39
What are the complications of measles?
Otitis Media: Inflamation of the ear (7-9%)
Pneumonia (1-6%)
Diarrhoea (8%)
Acute Encephalitis- rare but fatal (1 in 2000)
40
What is the treatment for measles?
Antibiotics for superinfection
41
How do you prevent measles?
- Vacination with the live MMR before the age of 1
42
What's the name of the virus which causes chicken pox?
Varicella Zoster Virus or Herpes Virus
43
What are the clinical features of chicken pox?
- Fever
- Malaise
- Anorexia
- Rash
44
What are the complications of chicken pox?
- Pnemonitis (especially in smokers)
- CNS involvement
- Thrombocytopenia Purpura
- Foetal Varicella Syndrome
- Congenital Varicella
- Zoster
45
What is the treatment for chicken pox?
It's symptomatic in adults and immunocomprimised children
- Aciclovir oral, IV in severe cases of the disease or neonates
- Chloropheniramine can relieve itch in less that 1 year olds)
46
How can you prevent chicken pox?
- Expose when young
| - Live vaccine, 2 doses (used in USA and Japan)
47
Which virus causes Rubella?
Togavirus (an RNA virus)
48
What are the clincal features of the Rubella Virus?
- Prodrome (an early symptom or sign of disease)
- Lymphadenopathy: post-auricular and sub-occipital
- Very non specific rash: Transcient, erythematous, behind ears, face and neck
49
What are the complications of rubella?
- Thrombocytopenia
- Post infectious encephalitis
- Arthritis
50
How is the child affected when you contract rubella in pregnancy?
Congenital Rubella Syndrome (CRS):
- Catarcts and other eye defects
- Deafness
- Cardiac abnormalities
- Microephaly
- Retardation of the intra-uterine growth
- Inflammatory lesions of the brain, liver, lungs and bone marrow
CRS is more severe when the infection is contracted earlier in pregnancy.
Foetal damage rare after 16 weeks. Deafness only reported up to 20 weeks
51
What's the treatment for rubella?
No treatment available.
Immunoglobulin given to exposed pregnant women.
Vaccine; part of the MMR. 2-3% of women of child bearing age remain susceptible
52
What is the virus that cause Parvovirus?
B19 (a DNA virus)
53
How is parvovirus transmitted?
Respiratory secretions or from mother to child
54
What are the symptoms of parvovirus?
- Asymptomatic in 20%
- Risk of miscarriage in early pregnancy, but low risk
- Foetal disease: Anaemia and hydrops (foetal transfusion)
- Clinical disease: Minor respiratory illness, Rash (slapped cheek), Arthralgia, Aplastic anemia, Anaemia in the immunosuppresed (this may be prolonged)
55
How do you treat parvovirus?
- None if it's a self limiting illness
- Blood transfusion
- Infection control: Difficult as infectious prior to the arrival of the rash.
56
What is Respiratory Syncytial Virus (RSV)?
A form of Pneumovirus
Bronchilitis:
- Affects 0-24 month olds
- Annual winter epidemics, incubation 4-6 days
- It can be life threatening and reinfections are common
57
What is Metapneumovirus?
Caused by the Paramyxovirus.
Causes respiratory illness similar to RSV.
It ranges from mild upper respiratory tract infection to pneumonia
58
What is adenovirus?
Accounts for 10% of childhood respiratory infection
| Clinical Disease: Mild URTI (occasionally Severe Pneumonia), Conjunctivitis and diarrhoea
59
What is Parainfluenza?
Caused by the paramyxovirus
There are 4 types; 1 in winter and 3 in summer
It's transmitted person to person
Clinical: Croup (Inflamation of the larynx), bronchiolitis and upper respiratory tract infection.
60
What is Rhinovirus?
Also known as the common cold.
Found in 70% of children with mild upper respiratory tract symptoms.
Similar clincal features to adenovirus
61
How do you diagnose and treat RSV?
Diagnosis- PCR on the secretions from nasopharyngeal aspirate
Treatment- O2, manage fever and fluid intake
62
How do you diagnose and treat Metapneumovirus?
Diagnosis- PCR
| Treatment- Supportive only
63
How do you diagnose and treat Adenovirus?
Diagnosis- Respiratory panel PCR or eye swab PCR
| Treatment- None or Cidofovir in immunocomprimised
64
How do you diagnose and treat Parainfluenza?
Diagnosis- Multiplexed PCR
| Treatment- None
65
What is Rotavirus?
Reovirus (RNA virus)
Transmission: Foecal-oral and occasionally respiratory
Low infective dose
Incubation is only 1-2 days
Epidemiology: Seasonal in the UK (winter and spring) but worldwide
440000 deaths a year
66
What are the clincal features of Rotavirus?
- Diarrhoea and vomiting
- It usually affects 6/12 months to 2 year old babies
- It's a severe disease if you're 6 to 12 months old.
- Increased mortality in poorer countries
67
How do you diagnose, treat and prevent Rotavirus?
Diagnosis: PCR
Treatment: Oral rehydration
Prevention: Oral live vaccine- UK introduction in 2013. Given and 2 and 3 months of age.
68
What is Norovirus?
- Known as the winter vominting bug
- Often outbreaks in nurseries, hospitals and cruise ships
- It's food-Borne
- Transmitted by person to person transmission
- High incidence of vomiting (more than 50%)
- Short course: 12 to 60 hours
69
How do you diagnose and treat Norovirus?
Diagnosis: PCR
Treatment: Oral rehydration
70
Which virus causes mumps?
A member of the Paramyxoviridae family
71
What is the current treatment for mumps?
The MMR.
In the pre-vaccine era 90% of infections were in under 14s and so more than 85% of adults were immune because of previous childhood infection
72
What are the clinical features of mumps?
- Prodrome
- In the next 24 hours you develop earache and tenderness over the ipsilateral parotid
- In the next 2-3 days you develop a gradually enlarging parotid with severe pain. It's normally bilateral but can be unilateral in 25%
- Pyrexia up the 40 degrees centigrade
- Within a week the parotid gland returns to normal size
73
Which viral infections cause the child to present with respiratory symptoms?
```
repiratory syncytial virus (RSV)
metapnuemovirus
adenovirus
parainfluenza
rhinoviurs
```
74
Which viral infections cause the child to be present with diarrhoea?
rota virus
norovirus
mumps
75
What are good targets for anti-fungal agents?
beta-1-3-glucan present in fungal cell wall
| ergosterol in the fungal cell membranes required for normal growth and function of the fungal cell wall
76
What are beta-1-3-glucans?
large polymers of UDP glucose
major structural component of fungal cell wall
synthesized bu beta-1-3-glucan synthase
77
Which anti-fungal drugs require therapeutic drug monitoring?
itraconazole (there is a minimum level at which it doesn;t work at)
5-flurocytosine (can't go above a certain threshold)
voriconazole (high level cause liver toxicity and below a level it doesn't work)
78
What is aspergillosis?
a group of fungal conditions caused by aspergillus spp
79
Describe the polyene anti fungal agents
- joins with ergosterol, forms holes and causes death by the leakage of k+
- amphotericin B and nyastatin
- used against most fungi of medical importance
- causes allergic reactions and nephrotoxicity
- AmB not absorbed orally, administered parenterally and used for serious systemic infections
- Nyastatin too toxic for systemic use so only used for superifical infections e.g. oral/vaginal candidiasis
80
Describe the allylamines anti fungal agents
- inhibits ergosterol (at first arrow)
- terbinafine
- has a broad spectrum of activity but only used for dermatophyte infections in practice
- can cause liver toxicity
- topical use: tinea, pedis, tinea corporis, tinea cruris
- systemic use: tinea capitis, onychomycosis
81
Describe azole anti fungal agents
- inhibits ergosterol synthesis
- has a 5 membered azole ring
- imidazoles (clotrimazole) have 2 nitrogen atoms and are toxic so rarely used systemically
- triazoles (fluconazole) have 3 nitrogen atoms and are less toxic
- fluconazole cannot be used on Aspergillus soo
- can cause hepato-toxicity and also have drug interactions : can inhibity cytochrome P450 enzymes
82
Describe Echinocandins anti fungal agents
- they inhibity beta-1.3-glucan synthase so there is construction of a severely abnormal cell wall
- e.g. anidulafungin
- used for aspergillus and candida but misses out certain moulds and crytococcus (causes meningitis in people with HIV)
- has minimal adverse effects
83
Describe 5 fluorocysteine anti fungal agents
- enters cell using fungal cytosine permease, converts to 5FU (from 5FC) to inhibit DNA and RNA synthesis
- only works on yeasts
- can cause bone marrow suppressio
- used to treat crytocoocal meningiitis in combination with AmB
84
Describe Griseofluvin anti fungal agents
- inhibit fungal mitosis
| - works on dermatophytes e.g. kerion and onychomycosis
85
What is a definitive host?
either harbours the adult stage of a parasie of where the parasite utilises the sexual method of reproduction
86
What is an intermediate host?
harbours the larval or asexual stages of the parasite
87
What is a paratenic host?
host where the parasite remains viable without any further development
88
What are NRTI's
nuceloside analogue reverse transcriptase inhibitors
- they are activated by phosphorylation by cellular enzymes to the triphosphate form
- inhibition of viral RNA-dependent DNA polymerase (reverse transcriptase) and chain terminaon of the viral RT reaction
89
What are NNRTI's?
non-nucleoside reverse transcriptase inhibitors
| -non-competitive inhibitors of RT, they bind to hydrophobic pocket on RT, separate from the active site
90
What are Protease Inhibitors?
binds to the protease active site and inhibits
91
What mutation leads to reisistance to lamivudine?
M184V
92
Name some anti-hepatitis C compounds
- interferon alpha and pegylated interferon alpha
| - ribavirin
93
What is aciclovir used for?
treatment of herpes simplex virus and VZV
94
What is ganciclovir used for?
cytomegalovirus (CMV)
95
What is oseltamir and zanamavir used for?
they are neuraminidase inhibitors used for influenza
96
What is ribavirin used for?
Hep C and Respiratory syncytical virus
97
What are interferons used for?
hep B and hep C infections
98
What is IgM?
produced in acute infections
short term
used to check for current illness
it is the primary repsonse which deveops in the few weeks following first exposure to antigen
99
What is IgG?
it is long term immunity
| used to check for past disease
100
What is IgA?
it is found in breast milk and used in passive immunity
101
What is IgE?
Used in allergy
102
What is surveillance?
Process if gathering information to ensure that disease outbreaks are pre-empted or idenitified early
