Infections Flashcards
Define: pathogen
Any organism or agent (toxin) that produces a disease
Define: pathogenicity
The ability of a pathogen to cause disease
Define: virulence
Intensity of disease
What are the 9 types of infections?
Acute Chronic Latent Healthcare associated infection Opportunistic Primary Secondary Septicaemia Toxaemia
What are the 3 common bacteria that cause healthcare associated infection?
Clostridium difficile –> gut infection
Staphylococcus aureus
E.coli–> UTI
What is the difference between septicaemia and bacteraemia?
Septicaemia- high conc of bacteria DIVIDING in blood
More severe
Bacteraemia -Presence of bacteria in blood
What’s the main cause of URT infections? What bacteria can also be the causation?
70% viral Streptococcus pyogenes (group A)
What are the 2 common URT infections?
Pharyngitis - throat
Tonsillitis - tonsils
What’s the treatment used in URT infection?
Oral penicillin
What can be the causation of an acute otitis media?
Mainly viral
Bac: streptococcus pneumoniae
Haemophilius influenzae
Causes of conjunctivitis
Mainly viral Allergic -pollens Reactive - dust, smoking STI associated -new born babies Bac: staphylococcus spp Streptococcus spp Heamophilus spp
Treatment for conjunctivitis
Topical chloramphenicol
The bac which involved in STI associated conjunctivitis
Neisseria gonorrhoeae
- severe conjunctivitis in new born
- perforation of cornea
Chlamydia trachomatis
- adult
- trachoma–> blindness
What is the name of the bacteria that cause tuberculosis?
Mycobacterium tuberculosis
What are the bacteria that cause pneumonia?
Streptococcus pneumoniae
Haemophilus inflenzae
Staphylococcus aureus
What is the main cause for acute bronchitis? What bacteria involved in 2’ infections?
95% viral
Mycoplasma pneumoniae -atypical pneumonia. non productive cough
2’ : streptococcus pneumoniae
Haemophilus influenzae
What is the main cause of chronic bronchitis? (COPD)What bacteria exacerbate the symptoms
Usually due to smoking / irritant
Inflammation of trachea and bronchi
Streptococcus pneumoniae
Haemophilus influenzae
What are the two types of urinary Tract infection? Give an example of infection. What type of bacteria are involved?
Ascending - entry through urethra - cystitis (E coli)
and descending - infection from blood to kidney (staphylococcus)
What is the impact of urinary tract infection on elderly
Confusion
Difficulty passing urine
What is pyelonephritis?
It is the complication of common bladder infection
Potentially serious kidney /ureters infection that has spread to blood
What are The symptoms of pyelonephritis?
Fever
Fewer UTI symptoms
Haematuria- blood in urine
What are the common causes of sexually transmitted infections STIs
Bacteria*
Viral-human Papilloma virus- cervical cancer, HIV
Fungal - Candida albicans -yeast
Protozoa
What are the bacteria that cause STI
Chlamydia trachomatis *
Neisseria gonorrhoea
Treponema pallidum
What are the symptoms due to chlamydia trachomatis or neisseria g
Women: discharge, pelvic pain–> PID pelvic inflame disease, infertility
Men: discharge–> inflame of prostate urethra. Infertility
Examples for latent infections
Herpes
Shingles- skin rash
TB
Describe the mechanism of action fluorinated pyrimidine analogues in treating fungal infections, name the drug
5- flucytosine
Disrupt RNA DNA biosynthesis
Misincorporation of 5-fluorouridine
Give two examples of drug that belong to antifungal class-polyenes
Nystatin
Amphotericin B
How does nystatin and amphotericin produce antifungal effect
Cell membrane ergosterol
(Only presence in fungus cell wall not human- cholesterol) Increase permeability of PM and oxidative damage
Not toxic to human
Name an example drug that belongs to antifungal class - allylamines and thiocarbamates
Terbinafine
What’s the MOA of terbinafine
Ergosterol biosynthesis
-squalene epoxidase
Same step in human cells but not the same shape of enzyme
Describe the MOA of azole/ triazoles
Inhibition of ergosterol biosynthesis
- lanosterol 14- deMETHYlase
Accumulation of toxic METHYLsterol intermediates- enzymes recognise increase in conc. and shut pathway
What is the side-effect of antifungal agents
Diarrhoea only
Name The drug that belongs to echinocandins
Caspofungin- very expensive!!
Describe the MOA of caspofungin
Inhibition of Cell wall biosynthesis
1,3 betaD glucan synthase
Inhibition of glucan
Safe to patient : 16-18 long C chain
What are the three types of helminths?
Nematodes - large round worms (ascaris) , threadworms , hook worms or filariae - lymphatic filariasis, onchocerciasis, loiasis
Cestodes -tape worms. from uncooked meat, segmentated worm with eggs at the end of segment, excreted via faeces
Trematodoes (flukes)- snail intermediate host, damage to vital organs
Life cycle of ascariasis
Worm live in SI Produce fertilised egg Excreted through faeces Stay in soil for 2 WEEKS TO DEVELOP Re ingested (egg) in SI Larvae latch, goes to LUNG Final stage- mouting, cough up and swallow back to SI- develop into mature worms
Transmission and Symptoms of schistosomiasis cause by Schistosoma (blood flukes)
Go in the snails then human
Eggs stuck in tissues, body immune says try to get rid of it, chronic inflammation and scarring - cancer
Give 3 example of pathogenic fungi?
Candida Albicans-oral, vaginal thrush, nail infection, ocular candidiasis
Aspergillus fumigatus- pulmonary infection or inhalation of spores. Asthma, TB
Dermatophytes- skin, nail, hair infection athletes foot or ringworm
What are fungi
Eukaryotic org. Have true nuclei
Fungi are divided into 2 families…
Yeast, unicellular, round cells, budding/ fission
Moulds, multicellular, also called filamentous fungi, produce hyphae
Fungi are carbon Hetero/ homo trophs? What does it mean
Heterotrophs, they require ready made organic compounds as carbon source
What are dermatophytes?
How is it spreaded
Common symptoms
They are keratinophilic moulds associated with infections of skin, nails, hair, scalp. Spread through direct contact and spores. Common symptoms are itching burning pain irritation
Ring worm infections What part of body is infected in Tinea corporis Tinea cruris Tinea capitis
Ring worm of the skin
Groin
Scalp
What are the ringworm treatment for tinea corporis and cruris
And other possible treatment
Topical imidazole
Clotrimazole, econazole, micinazole
Terbinafine >12 yo
Topical corticosteroid cream can be added in combination if severe inflam
What are the oral therapy available for T. Corporis, cruris if topical fails
Terbinafine
Itraconazole
Griseofulvin -rare
What are the treatments for tinea capitis
Oral + ketoconazole, selenium sulphide shampoos (risks of transmission?) or terbinafine creams
Which fungi spp. Is griseofulvin and terbinafine active against?
G- microsporum spp
T- trichiphyton tonsurans
Profile of griseofulvin
Narrow therapeutic range
Long course needed
Contra indication with severe liver disease n systemic lupus erythrmatosus
Avoid if breastfeeding/ pregnancy
Things to look out for (griseofulvin
Potentiate alcohol effect
Interacts with Oral contraceptives -decreases efficacy
Take with fatty food helps absorption
What’s tinea pedis also called
Althelets foot
What might be the causes for tinea pedis
Trichophyton rubrum
Tichophyton mentagrophytes
Epidermophyton floccosum
What are the treatments for T pedis
First line - imidazole cream
-terbinafine cream
Stages of bac infection
Pathogenicity/ virulence/ no. Of bac/ host IMS Transmission Adhesion and invasion Evasion of host defence Multiply Damage host cells, get nutrients Release toxins
Adherence to surfaces depends on (bac
Adhesins
Example of adhesins
Proteins -fimbrial, afimbrial surface proteins
Polysaccharides- component of cap, teichoic/ lipoteichoic acid
E. coli binding onto bladder causes UTI
P pili type 1 binds to sugar moieties (mannose) of glycolipids on ep cells lining urianry travt
3 ways of surviving phagocytosis (bac
Reside in phagolysosome (harsh environment low PH)
Reside in unfused phagosome (salmonella)
Destroy or escape from phagosome and live in cytosol
Invading non phagocytic cell
Bac injects invasion proteins into host cell to recruit host proteins to induce phagocytosis
Secreted by g-ve bac (salmonella, pseudomonas)
Activate host signalling, recruit actin (cytoskeleton protein)
Bac taken up by NON phagocytic cells
Extra cellular invasion (bac
Bac produces en. That
Attack extracellular matrix
Degrade carbs- protein complexes between cells - protease, glycanase
Disrupt cell surface
Uses of biofilm
Protect from
Phagocytosis
AB
disinfectants
Name the bac grow biofilm on microscope coverslip
Enterococcus faecalis
Limiting source of nutrient for bac in host
Iron
Why iron is limiting in host
Aerobic con. Iron oxidised into ferric form - low sol.
Complexes to protein eg transferrin in serum
Ferritin heamoglobin in interracellular
Bac acquiring iron
1 direct contact use cell surf proteins: transferrin binding protein TBP and haemoglobjn BP
2 produced when conc is low. secret siderophores w high affinity for Fe- from proteins/ insoluble ferric salt. Transport Fe into cell
Structure of siderophores
Catechol gp
Hydroxymate gp
Bac evading complement of host
Thick Psac layer around cells- cap
Elongated (LPS) O chain bw com and bac
Prevent complement activation
Lipid A causes fever
Resisting phagocytosis by (3)
Prevent contact w phagocyte (biofilms, cap)
Affect phag migration (S.pyogenes peptidase cleaves complement C5a)
Destroy phag (use toxins eg leukocidins)
Evade host ab response (2)
Bind to host proteins e.g. Albumin, fibronectin - m protein s.pyogenes not detected as foreign
Produce surface protein which bind ab ‘backwards’ (Heavy chain end binds) - proA in s.aureus n proG s.pyogenes -prevent opsonisation (marked pathogens, draw WBC for ingestion
Toxoid
Inactive or very low activity. Used for vaccination eg tetanus
Exotoxin
Endotoxins
Activitely secreted during bac growth
Inside bac or a structure part. Not secreted. Only released when bac die and Lysis eg LPS
