The Public - Semester 1 Flashcards
1
Q
What is Public Health?
A
Prevention and management of disease/health condition through health promotion
2
Q
What is epidemiology?
A
The study of the incidence, distribution and possible control of a disease
3
Q
What is pathogenicity?
A
The ability of a microorganism to grow within an infected host - usually causes harm to the host
4
Q
Define commensalism and symbiosis
A
- Commensalism - Allowing microorganism growth without causing damage to the host (co-existence)
- Symbiosis - A partnership in which the host and microorganism both benefit
5
Q
What is the difference between opportunistic and obligate pathogens?
A
- Opportunistic pathogens can survive outside of a host and be transmitted without causing disease
- Obligate pathogens must infect a host and cause disease in order to survive
6
Q
What are the methods of elimination of a pathogen?
A
- Physical or internal removal
- Starvation of nutrients preventing growth
- Immune response
7
Q
What are the methods of accumulation for a pathogen?
A
- Adherence to host cells or tissues
- Obtaining nutrients from host or other pathogens
- Proliferation in the body
8
Q
What affects human-pathogen interactions?
A
- Host factors (e.g. health status)
- Pathogen factors (e.g. type of pathogen)
9
Q
What are the two types of disease transmission?
A
- Vertical (from mother to child)
- Horizontal (between members of a population)
10
Q
What is an incubation period?
A
The period between infection and disease where the microorganism can grow
11
Q
Define virulence
A
A measure of the pathogenicity of a microbe
12
Q
What is the difference between disease and infection?
A
- Infection - The establishment of a pathogen in the body
- Disease - Damage or injury that impairs host function
13
Q
How can an infection develop?
A
- Attachment to epithelial cells
- Invasion of cells of the mucous membrane
- Penetration of the epithelial cells allowing invasion of deeper tissues
14
Q
Describe the microbiota of the oral cavity
A
- High nutrient concentration provides a desirable environment for microorganisms
- Acidic glycoproteins on the tooth surface allows bacterial colonisation, causing dental plaque
- Bacteria produce acid the decalcifies tooth enamel and causes decay
15
Q
Describe the anatomy and microbiota of the GI tract
A
- Consists of stomach, small intestine and large intestine
- Natural gut flora responsible for absorption of nutrients from digested food
16
Q
Describe the anatomy and microbiota of the respiratory tract
A
- Upper RT = sinuses, nasopharynx, pharynx, oral cavity, larynx
- Lower RT = Trachea, bronchi, lungs
- If individual is healthy, only upper RT will be colonised
17
Q
Describe the microbiota of the urogenital tract
A
- Bladder is sterile but bacteria may be present in the urethra
- If bacteria in urethra multiplies and becomes pathogenic it can cause an infection (e.g. UTIs)
18
Q
How are acidic conditions maintained in the vagina?
A
- Presence of Lactobacillus acidophilus
- Glycogen fermented to lactic acid which maintains acidic conditions
19
Q
Explain the concept of chemotherapy and its relevance to antimicrobials
A
- Chemotherapy - Selective toxicity to the invader
- Closer the invading cells are to our cells makes selective toxicity harder
- Bacterial differences make infections caused by them much easier to treat
- Viruses and cancers are difficult to treat due to similarities to our cells
20
Q
How was a treatment for Syphilis developed?
A
- Paul Ehrlich - Using principles of selective toxicity to develop a treatment for Sleeping Sickness
- Atoxyl (first development) ended up being a lead compound for Salvarsan which could be used to treat syphilis
- Development of Neosalvarsan - More hydrophilic and less toxic than Salvarsan
21
Q
What is Salvarsan and how does it work?
A
- Pro Drug - Decomposes to oxophenarsine
- Oxophenarsine reacts with thiol groups on proteins causing denaturation
22
Q
How is the therapeutic index of a drug related to selective toxicity?
A
Measurement between a drug being therapeutic and toxic (may be therapeutic to humans but toxic to microorganisms in a specific dose range)
23
Q
What is Vancomycin used for?
A
Treatment of Strep. pneumoniae and MRSA infections
24
Q
What are common drug targets in a bacterial cell?
A
- Cell wall and membrane
- Ribosomes (transcription and protein synthesis)
- DNA synthesis
- Metabolism
25
How do pathogens cause disease?
- Virulence factors
| - Toxicity and invasiveness can determine whether an infection is local or systemic
26
Describe a test for virulence and why it applies to 50% of a test group
LD50 - The amount of agent required to kill 50% of a test group
50% instead of 100% because the pathogen numbers for 100% are similar for all organisms
27
Define attenuation
Alteration of favourable growth conditions of an organism, resulting in reduced virulence
28
Define toxicity
A toxin released by an organism which inhibits host cell function or kills the cell - can be systemic
29
Define invasiveness
Growth of an organism to a density the inhibits normal host function and causes damage
30
In which systems can a pathogen invade the body?
Circulatory and lymphatic systems
31
Give two examples of anatomical virulence factors of a bacterial cell
- Capsule - Protects bacterial cell and enhances ability to causes disease
- Pili - Allows attachment of bacteria to host cells or is involved in DNA exchange between bacterial cells
32
What type of pathogen causes diphtheria, how does it present and how does it cause disease?
- Non-Invasive Pathogen
- Pseudomembrane on throat
- Production of AB toxin inhibits EF2 which prevents protein synthesis and kills the cell
33
What type of pathogen causes whooping cough, how does it present and how does it cause disease?
- Non-Invasive Pathogen
- Violent cough, mucous present in throat
- Produces pertussis exotoxin, tracheal cytotoxin and invasive adenylate cyclase toxin
34
What type of pathogen causes cholera, how does it present and how does it cause disease?
- Non-Invasive Pathogen
- Infects small intestine causing rice water stools
- Cholera toxin increases adenylate cyclase activity which causes excess salt and water movement into the lumen of the small intestine, death by dehydration
35
Give an example of a disease caused by a partially invasive pathogen and describe it
- Shigellosis
- Blood and pus in diarrhoea
- Shiga toxin produced
36
How do primary invasive pathogens spread?
Enter lymphatic system from a primary infection site
37
Give an example of a disease cause by an invasive pathogen and describe it
- Enteric Fever (Typhoid)
- Infects small intestine and then enters system through epithelial cells
- Causes constipation/diarrhoea and a fever
- Spread through contaminated people/foods
38
Give an example of disease without colonisation
Food Poisoning
- Neurotoxin produced from Clostridium botulinum
- Entertoxin produced from Staphylococcus aureus
- Emetic and enterotoxins produced by Bacillus cereus
39
Describe the structure and function of gram positive and negative cell walls
- Positive: Thick layer of peptidoglycan outside cell membrane, teichoic acids in membrane (maintains iodine stain)
- Negative: Two membranes with a thin layer of peptidoglycan in between
- Function: Shape and structure, prevents rupture due to osmotic pressure
40
Why is it difficult to stain Nocardioform bacteria?
- Gram positive BUT
| - Peptidoglycan covalently linked to arabinogalactan which is esterified to lipids, making it resistant to staining
41
Describe the structure of peptidoglycan
- Alternating NAM and NAG residues
- Branched peptide chains
- Peptide chains cross link to form peptidoglycan sheets
42
Describe the structure and function of the Beta Lactams
- Lactam ring present in structure
- Possibly constructed from valine, cysteine and phenylalanine residues
- Lactam ring binds transpeptidase/carboxypeptidase enzymes to prevent cross-linking in the cell wall
- Cell wall weakened causing cell to rupture
43
What four factors affect the efficacy of a Beta Lactam?
- Ability to penetrate cell wall
- Affinity to peptidase enzymes
- Resistance to stomach acid
- Bacterial resistance
44
What are the 5 main penicillins and how susceptible are they to Beta Lactamases?
- Amoxicillin and Penicillin G - Susceptible to Beta Lactamase degradation
- Ampicillin - Resistant to class 1 Beta Lactamases
- Methicillin and Flucloxacillin - Resistant to all Beta Lactamases
45
What are the generations of Cephalosporins?
- 1st, 2nd and 3rd
- 1st not widely used anymore
- Gram negative activity
46
What are carbapenems?
- Broad spectrum beta lactam antibiotics
| - Resistant to beta lactamases
47
What are monobactams and which one is in use?
- Gram negative beta lactams
| - Only aztreonam in use
48
Describe the structure and mechanism of action of Vancomycin
- Glycosylated structure made of amino acids
- Non-ribosomal peptide
- Crystal structure fits between peptidoglycan sheets, preventing cross-linking
- Cannot penetrate gram negative cell wall therefore only exhibits gram positive action
49
Give an alternative to Vancomycin
Teicoplanin - A glycopeptide
50
How does immunology help us understand drug mechanisms?
Drugs generally work synergistically with the immune system for an effective response
51
What are the benefits and disadvantages of the immune system?
- Benefits: Protection, removal of infected cells
| - Disadvantages: Discomfort as a result of inflammation, damage to host cells (autoimmunity)
52
What is the difference between the innate immune system and the adaptive immune system?
- Innate: Rapid, first line of defence but does not vary between pathogens
- Adaptive: Slower activation but initiates a specific response to each pathogen. Response stored in immunological memory for a faster secondary response
53
List 4 innate defence mechanisms
- Anatomical and physiological barriers
- Phagocytosis
- Vasodilation
- Increased capillary permeability
54
How does the epithelia protect the body from infection?
- Prevents entry of bacteria
| - Locally produced antibiotics and intraepithelial lymphocytes kill bacteria at the surface
55
What are the components of the innate immune system and what are their functions?
- Lysozymes - Split the cell wall of bacteria
- Acute Phase Proteins - Opsonization, attraction of phagocytes, increased blood flow
- Complement System - Opsonization
- Interferons - Antiviral resistance
- Macrophages - Engulf and break down cells to present them to the immune system
- Natural Killer Cells - Recognise changes in cell surface of infected cells
56
What are the granulocytic cells of the immune system?
Cells with a multi lobed nucleus
- Neutrophils: Destruction through lysosomes
- Basophils: Contains granules containing toxic chemicals which are secreted when in contact with a microorganism, release of histamine in allergic reactions, bind complements C3a, C3b and C5a
- Eosinophils: Release toxins from crystalloid granules at the site of parasitic infection/allergic reaction
57
What are the monocytes cells of the immune system?
Cells with one large nucleus
- Macrophages - Breakdown cells and present antigens to immune system, repair damaged tissues, remove infected cells
- Dendritic Cells - Bring antigen to lymphoid organs
58
How do NK cells know which host cells are infected?
- Virus suppression of MHC Class 1
| - MHC Class 1 is expressed on healthy cells and stimulates inhibitory receptor of NK cells
59
What is the complement pathway?
- Mast cells are activated causing vasodilation and increased capillary permeability to bring immune cells to the site of infection
- Phagocytes then engulf and present microorganisms for opsonisation
60
List four evasion mechanisms of pathogens
- Resistance to phagocytosis
- Resistance to the complement pathway
- Resistance to reactive oxygen intermediates in phagocytes
- Resistance to locally produced peptide antibiotics
61
How does immunological memory work?
Structure of antigen and antibody produced is stored in the immunological memory, faster antibody production if infected again
62
What are the cells of the adaptive immune system and what are their functions?
- Th Cells: Recognise antigens presented on MHC class 2 (type 1, cell mediated immunity, type 2, humoral immunity)
- Tc Cells: Recognise antigen on MHC class 1, triggering apoptosis of the infected cell
- B lymphocytes: Differentiate to plasma cells which produce antibodies (stimulated by cytokines)
- Interactions between T and B cells ensure correct antibody is produced
63
Describe the structure and function of antibodies
- 2 light and 2 heavy peptide chains
- N terminal binds to antigen and C terminal binds to specific immune cell
- Functions include opsonisation, neutralisation, complement activation and antibody-dependent cytotoxicity
64
What increases in a secondary immune response?
- The speed of response
| - The antibody titre
65
What are vaccines and why are they used?
- A suspension of a dead, attenuated or modified microorganism
- Provide immunological memory for a disease without contracting it
- Prophylaxis
66
What are the three characteristics of vaccinations?
- Immunogenicity: Ability to induce antibodies
- Efficacy: Reduction in incidence between those who have been vaccinated and those who haven't
- Effectiveness: The ability of a vaccine to protect a community
67
Describe the 5 different types of vaccines
- Killed Virulent Organism: Pathogen killed but antigen intact
- Live Attenuated: Strain doesn't cause disease but still elicits an immune response
- Modified Toxins: Toxin treated with heat/chemicals, no symptoms experienced but immune response is triggered
- Isolated Antigens: Antigen injected to elicit immune response
- Genetically Engineered Antigens: Antigen is isolated and genetically engineered
68
What affects the response to a vaccine?
- Antigen content (e.g. live vaccines have higher content)
- Protein content (results in increased antibody content)
- Adjuvants present
- Type of antigen
- Dosage intervals - Longer intervals = more MHC interaction
- Genetics
- Age
69
Describe the structure of bacterial ribosomes
- About 55 proteins and 3 RNA strands
| - Up to 30% of dry cell weight
70
Why are ribosomes a good antibacterial target?
- Up to 40% of total energy consumption is from protein synthesis
- Even slow growing cells require protein synthesis so it targets all bacterial cells
71
What are tetracyclines and how do they work?
How are bacteria resistant?
- Synthesised from acetate by various Streptomyces
- Binds nucleic acids and proteins but ribosomal inhibition is the main inhibitor of cell function
- Usually cell membrane modifications cause resistance but mutations in the S10 ribosomal protein also cause resistance (prevent binding)
72
Give some examples of tetracyclines and their indications
- Chlortetracycline: Feline conjunctivitis
- Oxytetracycline: Acne, Foulbreed in honey bees
- Demeclocycline: Lyme Disease
- Doxycycline: Prophylaxis of malaria
- Lymecycline: Acne (more soluble than tetracycline)
- Minocycline: Treatment of Neisseria meningitis infections
73
Describe the structure and function of aminoglycosides
- Several sugar rings + min. one amino group
- Bind to 16S RNA in the 30S ribosomal subunit, preventing aminoacyl-tRNA binding to A site
- Gram negative action, appears to disrupt cell wall
74
How does tobramycin work?
Binds to both ribosomal subunits to prevent them combining
75
Give some examples of aminoglycosides and the diseases they treat
- Streptomycin - TB
- Tobramycin - Pseudomonas aeruginosa
- Gentamycin - Pseudomonas aeruginosa (less preferred)
- Amikacin (Kanamycin derivative) - Hospital acquired gram negative infections
- Paramomycin - Visceral and cutaneous leishmaniasis
76
What type of drug is Linezolid and what is its method of action?
What is it used for?
- Oxazolidinone
- Binds to 23S RNA in 50S subunit, preventing 30S subunit binding
- Secondary treatment of gram positive infections and MRSA infections
77
What are macrolides used for and what is their mechanism of action?
- Gram positive infections
- Deep seated infections
- Inhibit protein synthesis so can be used as a penicillin alternative - exit tunnel blocked
78
What enzyme metabolises erythromycin and what can this result in?
- CYP3A4
| - Drug interactions
79
What happens when macrolides are taken with food and why?
- Can experience nausea, vomiting, diarrhoea
| - Macrolides are gut motility agonists
80
What is the difficulty of using macrolides in paediatric preparations?
They have a bitter taste which is not easily masked
81
What is the difference between first and second generation macrolides?
- More acid resistant
- More hydrophobic
- More favourable pharmacokinetics
82
Give an example of a ketolide
Telithromycin
83
How have bacteria developed resistance to macrolides?
- Modification of L22 protein (exit tunnel structure)
- Macrolide efflux pumps
- Methylation of adenine 2058 in 23S RNA
84
What is convergent synthesis?
The process of making a multi-step synthesis more efficient
85
What is Chloramphenicol? Describe its structure and explain why it is used topically
- Broad spectrum growth inhibitor produced by fungus
- Molecule with 2 chiral centres (therefore 4 isomers, only one of which is active)
- If used internally it can cause aplastic anaemia
86
Give two examples of lincosamides and explain how they work
- Clindamycin
- Lindamycin
- Assumed same action as macrolides due to same methylation resistance method
87
What can clindamycin be used for?
- Anaerobic infections (mainly)
- TSS treatment, in combination with vancomycin
- Treatment of protozoa infections (in combination with chloroquine/quinine)
88
What is fusidic acid and how does it work?
- Terpenoid produced from fungus
- Used for treatment of gram positive infections - usually as eye drops but sometimes tablets
- Binds an EGF-GTP complex which then binds a ribosome, hydrolysis of GTP then prevents the complex from leaving ribosome so protein synthesis is inhibited
89
What are the meninges?
Protective membrane surrounding the brain - inflammation of the meninges from infection is meningitis
90
How does meningococcal disease progress?
- Organ failure and death can occur less than 12 hours after showing symptoms
- Meningococcal septicaemia can cause coagulopathies to form in peripheral tissues
- Can cause limb loss through gangrene and ischaemia
91
Describe the structure of meningococci bacteria
- Gram negative diplococci
| - Capsule, which defines what type of meningococci (12 types but B, C, W, Y are most common)
92
Which form of bacterial meningitis is most common?
Meningitis caused by capsular type B
93
How is the meningococcal C vaccine licensed and how was the efficacy tested?
- Licensed on immunological memory
| - Efficacy data from HiB conjugate trial
94
What is pneumococcal disease and what are the causes of death?
- Invasive Strep. pneumoniae infection
| - Septic shock, empyema and meningitis
95
Describe the structure of Streptococcus bacteria and the form of the vaccines
- Gram positive cocci with a capsule
- Conjugate Vaccine: (with diphtheria protein) made from capsular polysaccharides from 13 common serotypes
- Polysaccharide Vaccine: Capsular polysaccharide with 23 serotypes
96
What are the symptoms of haemophilus influenzae type B commonly mistaken for?
Bacterial meningitis
97
Describe the characteristics of a Norovirus virion
- Single stranded RNA
- No envelope
- Low infectious dose - less than 10 virions
- Variable
- Extremely stable to temperatures, disinfection and high sugar concentrations
98
What is gastroenteritis?
'Winter vomiting virus' caused by a norovirus
99
What are the symptoms of norovirus and how long do they last?
- Nausea and vomiting
- Watery diarrhoea
- Abdominal cramps
- Headaches
- Slight fever
- Myalgia or malaise
Last around 72 hours - short term
100
How is norovirus transmitted?
- Direct contact
| - Fecal-oral route
101
What is viral shedding?
- Expulsion of a virus from a cell
- Movement to another area of the body
- Shedding into the environment
102
What causes diarrhoea as a symptom of norovirus?
- Small intestine microvilli damaged
| - Leads to nutrient malabsorption and enzymatic dysfunction at brush border
103
What causes vomiting in norovirus?
- Changes in gastric motility
| - Delayed gastric emptying
104
How is the spread of norovirus prevented?
- Hand washing
- Ward closures in hospitals following outbreaks
- General hygiene measures
105
What is the main worry surrounding symptoms of norovirus?
Dehydration due to diarrhoea and vomiting - consider dioralyte treatment
106
Why is folate metabolism important?
- Tetrahydrofolate is the active substance but it cannot enter cells
- 1-carbon metabolism in the body depends on tetrahydrofolate
107
What enzyme is an antibacterial target in the tetrahydrofolate pathway?
Dihydropteroate synthetase
108
Why did the diethylene glycol elixir of sulfanilamide cause deaths?
- Diethylene glycol oxidised to toxic aldehyde by liver
| - Elixir wasn't tested in humans before use
109
What was used as a prodrug for sulfanilamide?
Protosil - a red dye
110
How does sulphanilamide work and what are its limitations?
- Mimics para-aminobenzoic acid which is used by the enzyme dihydropteroate synthetase in the tetrahydrofolate pathway
- Difference in pKa means ionisation isn't ideal and reduces its potential as a drug
111
How are sulfanilamides made more acidic?
Substitutions within the molecule
112
Give an example of a substituted sulphanilamide and what it's used for
- Sulfapyridine
- Gram positive infections
- Pneumonia
113
What is folate metabolism essential for?
- DNA/RNA synthesis
| - C1 metabolism in mammals
114
Describe the pathway of tetrahydrofolate biosynthesis in bacterial cells, including the enzymes in evolved in each step
```
- Para-aminobenzoic acid + Pteridine
(Dihydropteroate Synthetase)
- Dihydropteroic Acid
(Dihydrofolate Synthetase)
- Dihydrofolic Acid
(Dihydrofolate Reductase)
- Tetrahydrofolic Acid
```
115
Why is Trimethoprim an effective antibacterial despite inhibiting the enzyme present in the mammalian pathway (dihydrofolate reductase)?
It has a higher affinity for the bacterial enzyme than the mammalian enzyme
116
What are the indications for Trimethoprim?
- Antimalarial
| - Treatment of cystitis (UTIs)
117
What type of combination treatment is used for blocking folate metabolism and what effect does it have?
- Sequential blocking
| - Has a synergistic effect due to drug resistance
118
Give a combination treatment for the inhibition of the folate pathway and why it is used
- Trimethoprim and Pyrimethamine
| - Prevent drug resistance
119
What are the characteristics of Pyrimethamine?
- More hydrophobic
- More active in protozoa
- Antimalarial action
120
What is methotrexate used for and how does it work?
Why doesn't it work in bacterial cells?
- Anticancer treatment or IBD/rheumatoid arthritis at low doses
- Targets dihydrofolate reductase preventing folate metabolism and therefore DNA synthesis
- Too polar to act on bacterial cells
121
What are the downsides of methotrexate use?
- Moderately toxic
| - If used concomitantly with penicillin, elimination is inhibited (overdose)
122
Why are travel vaccinations important?
- Risk to health of disease present in other areas
- Prevent spread of infection
- Check immunisation status of patients
- Decrease the risk of reintroduction of an eradicated disease
123
How is Cholera spread? Describe the vaccine type and regimen
- Contaminated water, food and faeces
- Killed cell vaccine, administered orally
- 2 doses required within 6 weeks
124
What is Hepatitis A and how is it spread? Describe the vaccines
- Viral spread/Faecal-Oral spread
- Infection of the liver
- Either short-term immunisation from immunoglobulin vaccine or I/M injection of inactivated virus
125
What is Japanese Encephalitis? Describe the vaccine
- A virus spread through a vector
- Inactivated virus - aluminium adjuvant enhances immune response
- I/M administration
126
Describe the meningococcal vaccine and the distribution of meningococcal disease
- Capsular polysaccharides conjugated to proteins
| - Different capsular serotypes more prevalent in different parts of the world
127
What is rabies? Describe the vaccine
- Virus transmitted through an infected animal bite
| - Embryonated egg inactivated vaccine - Virus for vaccine grown in fertilised hens eggs
128
What is tick-borne encephalitis? Describe the vaccine
- Virus transmitted through infected tick bites
| - Inactivated vaccine given as an I/M injection
129
What is typhoid and how is it spread? Describe the vaccines
- Invasive bacterial pathogen
- Transmitted through contaminated food/water
- Live attenuated vaccine given as an EC capsule or I/M injection of conjugated polysaccharide
130
What is yellow fever and how is it spread? Describe the vaccine
- Arbovirus
- Transmitted through mosquitoes (vector)
- Live attenuated vaccine administered I/M
131
Which malarial parasites are most harmful to humans? How are they transmitted?
- Plasmodium falciparum and Plasmodium vivax
| - Female anopheles mosquito
132
Describe the life cycle of the malarial parasite
- Invasion and differentiation in hepatocytes, then released into blood
- Merozoites multiply in red blood cells
- Some merozoites differentiate into gametocytes which are taken up by the mosquito
- Sporozites enter mosquito salivary glands and are then transmitted between humans when bitten
133
What are the symptomatic stages of a malarial infection?
Cold stage, hot stage and sweating stage
134
Why is an Artemisinin combination treatment used when the malarial parasite is unknown?
- Artemisinin quickly removes most of parasite
| - Partner compound removes remainder
135
How can malaria be avoided?
- Prevention of bites using DEET, long-sleeve clothing and mosquito nets treated with permethrin
- Prophylactic medication starting 1 week before and finishing 4 weeks after
- Monitor for symptoms for up to a year after return
- Avoid travelling in pregnancy
136
What is natural immunity?
Immunity that develops when living in an area where the disease is prevalent - this can be diminished when the area is left for a long time
137
What are the two types of chemoprophylaxis used in malaria? Describe them and how they work
- Suppressive Prophylaxis - Directed against red blood cell stages, treatment for 4 weeks
- Causal Prophylaxis - Directed against hepatocyte stages, treatment for 7 days
138
How is the Zika virus spread and how does it affect pregnancy?
- Transmission through mosquito bites
| - Can cause foetal abnormalities
139
Describe the structure of the Herpes virus
dsDNA, lipid envelope surrounding virion
140
What do Herpes Simplex 1 and 2 cause and how does it infect a human?
- 1 = Cold sores (oral)
- 2 = Genital herpes
- Virus enters through a break in the skin
141
Why is herpes a life long virus?
- Remains in sensory nerve ganglion, evading the immune system
- Travel back to the body surface can cause reactivation of the virus
- Reactivation is more common in type 2
142
How can herpes lead to systemic infections?
Viraemia can cause the virus to spread systemically
143
How is Herpes Simplex treated and how can it be avoided?
- Aciclovir or similar antiviral
| - Use of condoms (HSV2) or wearing gloves when handling lesions caused by HSV1
144
What is the Varicella-Zoster virus and how does it present?
- Herpes virus causing chickenpox and shingles
- Causes systemic lesions
- Can cause nerve damage and blindness in eye lesions
145
How is Varicella-Zoster treated?
Aciclovir
146
What is the Epstein Barr virus and how does it present?
- Glandular fever caused by a herpes virus
- Fever, sore throat, fatigue, swollen glands
- Can remain asymptomatic if controlled by T cells
147
Describe the vaccine for Varicella Zoster and explain why dead vaccines are not as effective
- Live attenuated vaccine given in 2 doses (adults) or a single dose (children)
- Immunoglobulins produced from dead vaccine eventually broken down by the body
148
What is the function of DNA gyrase?
- Induces left-handed supercoiling in duplex DNA to allow it to fit into the cell
- Through cutting, passing through and rejoining
149
Why is DNA gyrase a good antibacterial target?
Only bacteria supercoil their DNA
150
How do Quinolones work?
- Inhibit A subunit of DNA gyrase, interfering with DNA breakage and joining
- Broad spectrum activity so can be used if penicillin-resistant
151
What is nalidixic acid and what is it used for?
- First generation quinolone
- Broad spectrum but mainly gram negative infections
- UTI treatment
152
What are fluoroquinolones and how do they differ from first generation quinolones?
- Second generation quinolones for treatment of gram positive infections
- Fluorine substitutes hydrogen in an aromatic ring, difference in electronegativity alters properties
153
What are the indications of Ciprofloxacin?
- Respiratory/Urinary tract infections
- Gonorrhoea
- Anthrax
- Prophylaxis of meningococcal meningitis
154
Describe the pharmacokinetics of Ciprofloxacin
- Good absorption/distribution
- Renal excretion without modification
- Modified by CYP1A2 - can lead to interactions with warfarin and caffeine
155
What are the problems relating to Ciprofloxacin?
- Absorption reduced by antacids
- Concomitant use with NSAIDs causes CNS disturbances
- Can cause cartilage damage
- Reactions are more severe than with other antibiotics
156
What are third generation quinolones and what are they used for?
- Broad spectrum antibiotics
| - Treatment of Streptococcus infections and UTIs
157
How do DNA strand breakers work?
- Reduction of Nitro groups in the molecule (in low oxygen conditions) causes the formation of radical anions
- Radical anions extract a hydrogen radical from DNA, causing cleavage of the sugar-phosphate backbone
158
What types of DNA strand breakers are there?
Nitrofurans and Nitroimidazoles
159
What is Nitrofurantoin used for?
Treatment of UTIs
160
What are nitroimidazoles used for? List one side effect
- Anaerobic bacterial and protozoal infections
| - Alcohol intolerance
161
How do C. difficile infections occur and what are the symptoms?
- Strains acquired from hospital
- Broad spectrum antibiotic treatment diminishes normal microflora, promoting overgrowth of C. difficile
- Symptoms include diarrhoea, abdominal pain, fever, nausea
162
How are C. difficile infections treated?
- Metronidazole = First line
| - Vancomycin
163
How are C. difficile infections prevented?
- Good hygiene practice
- Use of narrow spectrum antibiotics
- Patient isolation if suspected C. difficile
164
What are the symptoms of chlamydia and how is it treated?
- Generally asymptomatic
- Can cause pain during urination and discharge
- Abdominal pain and irregular bleeding in women
- Pain in testicles
- 1g Azithromycin (single dose), 100mg Doxycycline BD 7/7, 500mg Erythromycin BD 14/7
165
What are the symptoms of urethritis (gonococcal and non-gonococcal) and how is it treated?
- Urethral inflammation
- Discharge (white, yellow or green)
- Swelling and pain in genitals
- Pain when urinating
- Gonococcal Treatment: 1g Azithromycin + Ceftriaxone (500mg I/M or 400mg PO)
- Non-Gonococcal Treatment: 1g Azithromycin (single dose), 100mg Doxycycline BD 7/7, 500mg Erythromycin BD 14/7
166
What are the causes and symptoms of bacterial vaginosis and how is it treated?
- Overwashing causing a build up of anaerobic bacteria
- Fishy smell
- Grey/white discharge
- 400mg Metronidazole or 300mg Clindamycin BD 7/7
- Also some vaginal gel formulations
167
What are the symptoms of trichomoniasis and how is it treated?
- Odorous, yellow discharge
- Pain during urination/sex
- Itching
- 2g Metronidazole (single dose) or 400mg Metronidazole BD 7/7
168
What are the symptoms of genital herpes and how is it treated?
- Fluid-filled blisters
| - 200mg Aciclovir or Aciclovir 5% cream 5 times a day 5/7
169
What are the symptoms of syphilis and how is it treated?
- First stage: Chancre (painless ulcer, may not be visible)
- Second stage: Non-irritating rash
- Third stage: Much later on, can present as neurological symptoms/cardiovascular disease
- Treated with penicillin or 100mg Doxycycline BD 14/7
170
What are the causes and symptoms of genital warts and how is it treated?
- Caused by HPV
- Itching but painless
- Can be recurrent
- Podophyllotoxin 0.5% applied BD 3/7 or imiquimod 5% applied 3 times weekly
171
What is TB and how is it transmitted?
- Bacterial infection caused by M. tuberculosis
- Air-bourne, infects lungs
- Only contagious if showing symptoms
