Pathogens Flashcards
1
Q
What is pathogenesis?
A
the ability of a micro-organism to causes disease
2
Q
What is a pathogen?
A
any organism OR agent that produces a disease
3
Q
What is virulence?
A
intensity of disease/ degree of harm caused
4
Q
What is an acute infection?
A
Sudden/rapid, usually short-lived. Can be severe
e.g. common cold, acute appendicitis
5
Q
What is a chronic infection?
A
Develops slowly. Long-lasting and/or recurrent
e.g. chronic hepatitis, Tuberculosis
6
Q
What is a latent infection?
A
Appears a long time after initial infection
e.g. Herpes, Shingles, Tuberculosis
7
Q
What is an HCAI?
A
Results from direct treatment in a healthcare setting or contact with a healthcare setting
8
Q
What is an opportunistic infection?
A
Caused by organisms that DON’T normally infect healthy hosts.
e.g. S. aureus, C. albicans, C. diff
9
Q
What is a primary infection?
A
Initial infection within a patient
e.g. surgical site infection, urinary tract infection
10
Q
What is a secondary infection?
A
Infections that follow a primary infection
e.g. infections of blood stream (septicaemia)
bones & joints
11
Q
What is septecaemia?
A
A life-threatening condition arising from pathogenic organisms in the blood
12
Q
What is bacteremia?
A
bacteria in the blood stream
13
Q
What are Group A Streptococcus?
A
common in throat and skin infections
(invasive cause TSS and necrotising fascitis)
14
Q
What are Group B Streptococcus?
A
Gut / urinary tract / Vagina
UTI, skin, bloodstream, pneumonia, soft-tissue bone and joint infections
15
Q
What are the most common URT infections?
A
Pharyngitis, tonsilitis and strep throat
16
Q
What are the 3 symptoms and 3 complications associated with URT infections?
A
Symptoms
- Inflamed tonsils
- difficulty swallowing
- fever
Complications
- Tonsillar abcesses
- otis media
- sinusitis
17
Q
What are the 3 less common symptoms of URTs?
A
- Scarlet fever - strep + rash
- Autoimmune effects - rheumatic fever, glomerulonephritis
- Invasive infection - TSS
18
Q
What are the 6 symptoms of acute otitis media?
A
Pain in ear
Hearing loss
Dizziness
Fever
Vomiting
Diarrhoea
19
Q
What does chronic otitis media cause?
A
Tissues surrounding eustachian tube swell and get blocked.
Air in middle ear gets absorbed into tissues, and vacuum forms in ear and fluid build up and leads to glue ear
20
Q
What are the 6 symptoms of conjunctivitis?
A
Redness in eye
Increased tears,
Thick crusty discharge after waking,
Green or white discharge during day,
Burning eyes
Blurred vision
21
Q
What is trachoma?
A
STI associated conjunctivitis
Spread by contact (towels, touch, flies)
Leading cause of blindness in low income countries – if left untreated
22
Q
Which bacteria causes chlamydia?
A
Chlamydia trachomatis
23
Q
Which bacteria causes gonorrhoea?
A
Neisseria gonorrhoeae
24
Q
What are the 4 symptoms of acute bronchitis?
A
- Non productive cough
- shortness of breath
- fever
- chest pains (lasts 10-11 days)
25
What are the 2 symptoms of chronic bronchitis?
- persistent cough (> 3 months),
- excessive mucus secretion
26
What are the 3 causes of chronic bronchitis?
Inflammation of trachea & bronchi
Usually due to smoking/irritants
Exacerbated by bacterial infection
27
What are the 4 symptoms of pneumonia?
Fever
Cough (productive)
Shortness of breath
Difficulty / pain on breathing
28
What is pneumonia?
Infection of lungs, inflammation of alveoli
29
What are the 4 symptoms of tuberculosis?
Persistent productive cough (> 3 weeks)
Blood in sputum
Chest pain, shortness of breath,
Fever (night), fatigue
30
Which bacteria causes tuberculosis?
Mycobacterium tuberculosis
31
What 5 things increases the risk of a lower UTI?
- Length of urethra- more common in women
- Catheterisation (50%)
- Disruption of normal urine flow- eg pregnancy, - enlarged prostate
- Older age
- Diabetes (more severe infections)
32
What are the 3 most common bacteria that ascending cause UTIs?
E. coli
Klebsiella
Proteus
33
What are the 5 main symptoms of an ascending lower UTI?
- Difficulty in passing urine/pain on urination (dysuria)
- Increased urge to urinate
- Urine may be cloudy/smelly
- Dull pain in pubic region
- Back pain/ generally unwell
(difficult to diagnose) in elderly or catheterised patients difficult to diagnose
34
What are the 4 main symptoms of an ascending upper UTI?
- Fewer UTI symptoms
- Pain in your side lower back
- Fever / loss of appetite/ feeling sick
- Haematuria (blood in the urine)
35
What is a descending UTI?
A rarer form of UTI where the UT becomes infected from bacteria in the blood (eg Staphylococci)
36
Which bacteria causes syphilis?
Treponema pallidum
37
What are the complications associated with chlamydia for adults and babies?
Adult: sterility, trachoma
Baby: premature birth, trachoma, pneumonia
38
What are the 4 symptoms of gonnorrhea and chlamydia?
Discharge
Pelvic pain
Infertility
Pain on urination
39
What are the complications associated with gonnorrhea for adults and babies?
Adults: sterility, systemic infection
Baby: trachoma →blindness
40
How is gonnorrhea treated?
Used to be 100% curable by penicillin
Now high levels of beta lactam resistance
Current PHE guidance:
- Ceftriaxone 1g IM or
- Ciprofloxacin 50mmg stat (if sensitivity known)
41
What is Caries?
A dental infection caused by Streptococcus mutans.
Grows on plaque on teeth, roduces Lactic acid and can cause tooth decay.
Treated with fillings/ extraction
42
What are dental abcesses?
Infection from tooth decay that spreads under the gum, can be treated with antibiotics but needs dental treament
43
What is peridontal disease?
Bacteroides/Actinomyces colonises between the teeth and gums. The gums bleed and receed, teeth may fall out. Can only be treated by better oral hygiene
44
Which bacteria causes oral thrush?
Candida albicans
45
What is Enterohaemorrhagic E. coli (EHEC)?
They bind to epithelial cells of large intestine, produce toxins which cause them to secrete fluid and causes diarrhoea
Can cause haemolytic-uraemic syndrome
46
What is Enterotoxigenic E. coli (ETEC)?
Bacteria bind to epithelial cells of small intestine
Produce plasmid-associated toxins which cause ‘Travellers diarrhoea'
47
What causes 'food poisoning'?
The presence of certain bacteria producing toxins, and the toxins cause the sickness
48
What are the top 3 bacteria the cause food poisoning?
Campylobacter jejuni
Salmonella enterica
E. coli
49
What is antibiotic associated diarrhoea? (and which two bacteria are most responsible?)
An opportunistic superinfection following treatment with broad spectrum antibiotics.
(Candida albicans or C. diff)
50
What is C. diff?
Obligate anaerobic, spore-forming bacteria, resistant to many antibiotics
Spores are resistant to most disinfectants - and once on a ward it becomes difficult to remove.
Produces toxins which cause severe diarrhoea & abdominal cramps.
Can progress, causing severe bloody diarrhoea, pseudomembranous colitis and toxic megacolon, can lead to death
51
Which 3 bacteria cause bacterial meningitis?
- Neisseria meningitidis* - most common in < 5’s, or 18-25’s
- Streptococcus pneumoniae - most common in <2’s or > 60’s
- Haemophilus influenza (Type B)
52
What are the 6 symptoms and treatment of bacterial meningitis?
Severe headache
Fever
Aching muscles & joints, Drowsiness
Neck stiffness
Rash
(late stage; sign of sepsis)
Treatment: IV antibiotics
53
Which 2 bacteria are the most common cause of skin infections?
Staphylococcus aureus
Streptococcus pyrogenes
54
What is folliculitis?
Infection of hair follicles
Treated by draining pus and oral abx if severe
55
What is impetigo?
Infection of the dermis, spreads quick and easily, treated with topical abx or oral if severe
56
What is cellulitis?
infection of wound/damaged skin causing overall malaise
treated by oral abx, or IV if severe
57
What is the difference between wet and dry gangrene?
Both are results of impaired blood supply, but wet grangrene involves a bacterial infection.
58
What is gas gangrene?
Caused by Clostridium perfringens, bacteria multiply and produced gas which opens and separates internal tissues, leading to rapid progression fo infection
59
What is necrotising fascitis?
causes widespread necrosis of underlying tissues and is frequently fatal
60
What is lyme disease?
Transmitted by tick
Initial infection in dermis
Infected tick bites can produce a red ‘target’ rash
Leads to systemic infection – acute flu like symptoms
Treat with antibiotics
If untreated can cause chronic disease
61
What bacteria causes lyme disease?
Borrelia burgdorferi
62
What is Osteomyelitis?
An infection of growing end of a long bone.
Pain, fever, pus in the blood vessels of a bone, dead areas. Can establish a biofilm.
Treated with 4-6 weeks of abx and removal of damage if severe
63
What is septic arthritis?
Pain, swelling, redness, fever
Following local infections e.g. cellulitis
Surgery (e.g. joint replacement)
64
What is endocarditis?
Biofilm infection of inner layers of heart e.g. heart valves. Streptococci, Staphylococci, Enterococci
Symptoms:
Temperature, heart murmur
Diagnosed by electrocardiography
Blood cultures frequently negative
Treated with penicillin (vancomycin) & aminoglycoside
65
What is sepsis?
A bacterial infection in the blood.
66
How are viruses different from other infectious agents?
Obligate intracellular parasites of bacteria, protozoa, fungi, algae, plants, and animals.
Ultramicroscopic size
Do not independently fulfill the characteristics of life.
67
What are the 6 stages of virus replication?
1. adsorption
2. penetration
3. uncoating
4. synthesis
5. assembly
6. release
68
What are the 2 modes of cell penetration?
Endocytosis (engulfment)
Fusion
69
What are the 5 main transmission routes of viruses?
- Respiratory
- Faecal-oral
- Blood-bourne
- Sexual transmission
- vectors
70
How to type 1 interferons aid immune response?
Viral RNA presence induces the expression of the interferons by the infected cell.
The binding of IFN-α & IFN-β to NK cells induces lytic activity, killing virally infected cells
71
What are virulence factors and the 5 things they are involved in?
Components that contribute to pathogenicity and virulence, including factors involved in:
- adhesion
- invasion
- evasion of host defence
- obtaining nutrients from the host
- toxicity
72
What are the two ways to measure virulence?
Infectious Dose:
ID50: dose to infect 50% of hosts
Lethal Dose:
LD50: dose to kill 50% of hosts
73
What are the 5 factors for indirect transmission?
- Soil
- contam food
- contam water
- inanimate objects
74
What are the 3 types of vectors?
Insects - malaria
Warm-blooded animals - rabies
Rat flea - black death
75
What is intracellular invasion?
Some pathogens penetrate cells and survive intracellularly
Others use it as a means of proliferation or spreading
Phagocytic cells invaded through phagocytosis
76
What is extracellular invasion?
Allows access to niches in tissue that aid in proliferation and spreading
Achieved through production of enzymes that:
attack extracellular matrix
degrade carbohydrate-protein complexes between cells
disrupt cell surface
77
What are the 2 types of adhesins?
Proteins
Polysaccharides
78
What are the 3 ways that some bacteria survive phagocytosis?
- Reside in the phagolysosome
- Reside in unfused phagosome
- Destroy or escape from phagosome and live in cytosol
79
What is a biofilm?
Bacteria attach to surface, grow, and become enveloped in matrix
A biofilm protects from phagocytosis, antibiotics, disinfectants
80
How does bacteria acquire iron?
Uptake of free iron or iron complexes
- direct contact using cell surface proteins: e.g. transferrin binding protein (TBP) and haemoglobin binding protein (HBP)
- by secreting small compounds (siderophores) with very high affinity for iron that capture iron from host proteins or insoluble ferric salts
81
What are siderophores?
Produced y bacteria when concentration of iron is low
Low mol wt, high affinity for iron
Compete for free or bound iron
Transport iron into cell
82
What are the two ways that bacteria can evade complement?
Capsules
- Thick polysaccharide layer around cells
- Prevents complement activation
LPS O-antigen
- Elongated O chains prevent complement activation
83
What are the 2 ways certain bacteria evade host-antibody response?
Bind to host proteins
Produce surface protein which bind antibodies “backwards”
84
What are the differences between exotoxins and endotoxins?
Exotoxin: actively secreted during growth
Endotoxin: only released cell bacteria dies
85
What are toxoids?
inactive or very low activity; used for vaccination (e.g. tetanus)
86
What are the 3 ways that exotoxins are transmitted?
- Ingestion of pre-formed exotoxin
food poisoning
- Colonisation followed by exotoxin production
- Infection of tissue followed by toxin production
87
What are exotoxins and what are the 3 types?
Proteins released by bacteria which harm cells
- Host-site specific exotoxins
- Membrane disrupting toxins
- Superantigen type
88
What are the 2 membrane disrupting toxins?
Pore-forming toxin (PFT)
Bi-layer disruption
89
What are super antigens?
Produced by e.g. staphylococci, eg toxic shock syndrome toxin (TSST)
Much higher proportion of T cells respond compared to normal antigens
Corrupts immune system, leading to massive non-specific inflammatory response, tissue damage, circulatory shock, multi-organ failure
90
What are endotoxins?
Released only when bacteria are destroyed
]
91
What is quorum sensing?
Many (pathogenic) bacteria only produce virulence factors until a quorum (minimal number) of cells is present
92
What are fungi?
Eukaryotic organisms – have true nuclei
Moulds
- Multi-cellular, also called filamentous fungi, produce hyphae (see on rotting food)
Yeasts
- Unicellular, round or oval cells, reproduce by budding or fission
Geophilic (soil), Zoophilic (animals) or Anthropophilic (humans)
93
What are tinea infections?
Associated with infections of skin, nails and hair
Common symptoms – itching, burning, pain, irritation
Risk factors – environmental, clothing, hyperhidrosis, immunocompromised
94
How is ringworm treated?
Tinea Corporis & Cruris – mild non-extensive disease – first line topical imidazole
Terbinafine is an alternative (> 12’s only)
Topical corticosteroids can be added in combination if inflammations +++
Oral therapy if topical fails
95
What is griseofulvin?
Antifungal drug
Narrow therapeutic range
Only effective against dermatophyte infections
Long courses needed since does not persist in keratinous tissue after the end of therapy
Contraindicated in patient’s with severe liver disease & Lupus
Avoid if breastfeeding or pregnant during and for one month after treatment stops (men not father children for 6 months post treatment)
96
What are the 4 counselling notes for griseofulvin?
- Main side effects – GI & headache, cognitive, hepatobiliary, skin sensitivity reactions
- Effects of alcohol potentiated
- Interacts with other medicines
Decreased efficacy
Oral contraceptives (COC & POP),
- Take with or after a fatty food
97
What is tinea pedis?
More common in adults, some higher risk groups
Skin becomes scaled, macerated and fissuring
Geophilic or anthrophilic
Causative species
- Trichophyton rubrum
- Trichophyton mentagrophytes
- Epidermophyton floccosum
98
How is tinea pedis treated?
First line
Imidazole cream: 2-4 weeks
Terbinafine cream: 1 week (over 12’s)
If inflammation +++ combine with hydrocortisone
If topical fails or severe infection – oral treatment
Terbinafine – 250mg daily for 2-6 weeks – 1st line
99
What are the 6 counselling advice for tinea infections?
- Clothing
- Hygiene
- Drying after washing
- Avoid scratching
- Wash clothes and bed linen
- No need to avoid school or nursery
100
What is terbinafine, when must it be avoided and what are the 3 side effects?
Antifungal medicine
Avoid in pregnancy, lupus, severe renal annd hepatic impairment
Side effects
- Mild GI disturbances
- Headache
- Hepatotoxicity (monitor)
101
What is onchomycosis?
fungal nails
102
How is fungal nail managed topically?
Only suitable for mild and superficial disease in up to 2 nails, OR people who cannot take systemic agents
Amorolfine – 6 months finger nails, 9-12 months toe nails
103
How is fungal nail managed when systemic?
1st line - Terbinafine
Itraconazole (pulse therapy)
oral itraconazole first line if it is caused by a candida infection
104
What advice is given for fungal nails?
Keep nails trimmed
Wear well-fitting shoes, without high heels or narrow toes. Consider replacing old footwear which could be contaminated
Wear cotton, absorbent socks
Wear protective footwear when using communal bathing places,
105
What is Pityriasis versicolor?
A fungal infection
Colonization of the stratum corneum
Classically starts around puberty
Multiple patches on the trunk, neck and shoulders – pigment of skin is altered
Diagnosis normally through visual observation alone
106
How is Pityriasis versicolor treated?
Topical – Ketoconazole shampoo if large areas affected
Topical – imidazole if only small areas affected
Systemic – only if topical fails
Itraconazole OR fluconazole
No Corticosteroids
107
How is oral thrush treated?
Topical therapies
Miconazole oral gel
If extensive or severe, oral fluconazole
108
What is vaginal thrush and what are the 3 symptoms?
Vaginal candidiasis one of the most commonest infections seen by GPs
More common in pregnancy and diabetes
Symptomatic following broad spectrum antibiotic treatment
Presentation
- Intense vulval + vaginal pruritus
- Thick white adherent plaques and/or discharge - odourless
- Pain on intercourse and on urination
109
How is vaginal thrush treated?
Oral therapy – fluconazole first line
Topical treatment (clotrimazole)
If there are vulval symptoms, recommend a 1 or 2% clotrimazole cream to be applied 2-3 times daily
Range of other intravaginal creams and pessaries available
110
What is cutaneous candidiasis?
Folds of skin- esp nappy area, groin, under breasts and between folds of fat
Risk factors
Systemic antibiotics, HIV, skin conditions, skin maceration, occupational
Presentation
pruritus and irritation, burning and pain
111
How is cutaneous candidiasis managed?
Skin care advice
Topical imidazole +/- hydrocortisone
Oral treatment only when severe or when treatment has failed – fluconazole
For children – treat topically
