Treating Infection Flashcards
(23 cards)
Name some examples of specific and supportive treatment in cases of infection.
SPECIFIC:
- antimicrobials
- surgery (drainage e.g. of pus, debridement - removal of dead/damaged tissue - & dead space removal - preventing further infection)
SUPPORTIVE:
- symptom relief
- physiological restoration (combat changes caused by infection e.g. pH, O2, CO2)
List some of the different mechanisms of infection and give examples for each.
Contiguous/direct spread: one part of body to another
e.g. commensals in bowel causing UTI, perforation of organ causing peritonitis
Haematogenous: bloodstream spread e.g. endocarditis
Ingestion: faecal-oral e.g. Salmonella enteritis
Inoculation: contaminated object entering body e.g. bite (Rabies), stabbing
Inhalation: droplet/aerosol
Vector: third party organism e.g. mosquito, ticks
Vertical: intrauterine e.g. syphilis, toxoplasmosis; during delivery e.g. HIV, hepatitis B
What are some important things to consider when using antimicrobials?
Bacteriocidal (kills bacteria) v.s. bacteriostatic (prevents multiplication of bacteria)
Broad v.s. narrow spectrum
- selectively toxic
- few side-effects
- reach site of infection
- oral/IV
- long half-life (infrequent dosing)
- no interference with other drugs
Give some examples of antibacterial drugs which target cell wall synthesis.
Beta-lactams =
- Penicillins: penicillin (Streptococci), amoxicillin (Streptococci & some Gram+ve), flucloxacillin (Staph. & Strep.), co-amoxiclav (all above + anaerobes + lots of Gram-ve)
- Cephalosporins: cetriaxone (acts in CSF: blind treatment of meningitis)
- Meropenem: broad spectrum, almost all Gram-ve, generally safe for penicillin allergy
Glycopeptides (vancomycin) = most Gram+ve, some enterococci resistant VREs, Staph. resistance rare, not absorbed, narrow therapeutic window
Give some examples of antibacterial drugs which target protein synthesis.
Tetracyclines (doxycycline): oral, broad spectrum, specifically used in penicillin allergy, Gram+ve, atypical pneumonia, chlamydia, some protozoa inc. malaria treatment & prophylaxis, DON’T GIVE TO <12yrs)
Aminoglycosides (gentamicin): Gram-ve, severe Gram-ve sepsis, blood/urine, potentially nephro/ototoxic, narrow therapeutic window
Macrolides (erythromycin): intracellular penetration, alternative to penicillin for mild Gram+ve, atypical respiratory pathogens
Give some examples of antibacterial drugs which target nucleic acid synthesis.
Quinolones (ciprofloxacin): inhibit DNA gyrase, lots of activity on Gram-ve, atypical pathogens, increased chance of resistance & risk of Clostridium difficile
Give some examples folic acid synthesis inhibitors.
Trimethoprim
Sulfonamides
e.g. co-trimoxazole for pneumocystis pneumonia & MRSA
Give an example of an anti-fungals.
Fluconazole for Candida albicans
inhibits cell membrane synthesis
Give some examples of antivirals.
Aciclovir: Varicella zoster, Herpes simplex
(inhibits DNA pol)
Tamiflu: flu A & B
What is metronidazole used to treat?
Anaerobic bacteria & protozoa (amoebae, diarrhoea, vaginitis)
How would you measure antibiotic activity?
Disc sensitivity testing
How would you determine the minimum concentration of an antibiotic required to inhibit bacterial growth?
Minimum inhibitory concentration:
Double dilution of antibiotic-bacterial solution until bacteria is visible
What are the types of horizontal gene transfer?
Conjugation = temporary union of unicellular organisms to exchange genomic material
Transduction = transfer of genetic material between bacteria via a bacteriophage or plasmid
Transformation = uptake of fragments of genetic material by bacteria which are then incorporated into the recipient genome
Give some examples of mechanisms of antibiotic resistance.
Drug inactivating enzymes e.g. beta-lactamases, aminoglycoside enzymes
Altered target (reduces affinity for antibiotic) e.g. meticillin, macrolides, trimethoprim
Altered uptake: reduced permeability (beta-lactams)/increased efflux (tetracyclines)
Outline the transmission, signs and symptoms, and treatment of cellulitis.
Severe inflammation of dermal and subcutaneous layers of the skin
note: the term erysipelas also used (superficial form of cellulitis)
Direct contact (break in skin) e.g. cuts, bites, surgery, psoriasis, Athlete's foot, etc.
Most common causative organisms = group A beta-haemolytic Strep. (e.g. S. pyogenes) & Staph. aureus
S&S:
- inflammation: rubor (erythema), tumor, dolor (tender to touch)
- +/-fever
- throbbing area of inflammation which spreads
- “unwell”
- tends start on the leg and move up
Treatment:
- start antibiotics immediately - flucloxacillin 1st line
- check spread of infection by marking edge of inflammation
- examine heart in case it has spread —> endocarditis
- RICE = rest, ice, compression, elevate
note: necrotising fasciitis mimics cellulitis in the early stages (but has severe, constant pain out of proportion to physical signs)
Outline the transmission, signs and symptoms, and treatment of conjunctivitis.
Inflammation of conjunctiva of eye (mucous membrane lining the eyelids and sclerae)
Direct contact e.g. touching eye, makeup application, eye drops
Causative organism usually viral (e.g. adenovirus) but can also be bacterial (e.g. Staph. aureus, N. gonorrhoe, Chlamydia) or can be due to allergy rather than infection
S&S:
- soreness
- redness
- discharge
- burning
etc.
Treatment:
- analgesia
- hydration
- medication depends on cause
Outline the structure, replication, transmission, diagnosis, clinical presentation, and treatment of Streptococcus pneumoniae infection.
STRUCTURE = Gram+ve diplococci, anaerobic, alpha-haemolytic
TRANSMISSION = aerosol
COMMENSAL = found in resp. tract & nasopharynx
DIAGNOSIS = Gram stain (presence of neutrophils also)
catalase -ve, green on blood agar (alpha-haemolytic)
CLINICAL PRESENTATION =
- community acquired pneumonia
- pneumococcal meningitis
- sinusitis
- otitis media
note: pneumococcal disease usually affects >5yrs & 65yrs< or chronic heart, lung, liver disease + sickle-cell anaemia +HIV/AIDS
TREATMENT =
- penicillin if sensitive
- otherwise vancomycin or ceftriaxone
How can Staphylococcus and Streptococcus be differentiated and identified?
Gram stain:
- Staphylococcus = “bunch of grapes”, Gram+ve
- Streptococcus = “string of pearls” e.g. Strep. pyogenes or diplococci e.g. Strep. pneumoniae, Gram+ve
Catalase:
- Staphylococcus = catalase+ve
- Streptococcus = catalase-ve
Staph. differentiation:
- coagulase: only Staph. aureus is +ve
- haemolysis: only Staph. aureus is haemolytic (beta - complete destruction of RBCs)
Strep. differentiation:
- beta-haemolytic includes Group A (e.g. Strep. pyogenes), B, D (e.g. Strep. faecalis)
- alpha-haemolytic (green on blood agar due to partial destruction of RBCs) e.g. Strep. pneumoniae
Outline the structure, transmission, pathogenesis, diagnosis, clinical presentation, and treatment of Clostridium difficile infection.
STRUCTURE = Gram+ve rods, obligate anaerobes (but can form spores)
COMMENSAL = large intestine (becomes pathogenic after antibiotic treatment reduces commensal bacteria which compete with C. difficile and produce antimicrobials)
e.g. amoxicillin, cephalosporins, clindamycin, quinolones
PATHOGENESIS = endotoxins A & B
A —> produces enterotoxin —> damages membrane (so B can enter) & produces cytokines causing inflammation & excessive fluid secretion
B —> disrupts protein sysnthesis & produces cytokines causing inflammation
DIAGNOSIS = stool sample culture - Gram stain, ELISA (for toxins A & B)
CLINICAL PRESENTATION = pseudomembranous colitis
TREATMENT =
- discontinue predisposing antibiotics, PPIs, immunosuppressants, laxatives, opioids (if possible)
- fluid replacement
- oral metronidazole (IV if more serious) + vancomycin for severe diarrhoea
- isolate patient and inform infection control
What diseases do Clostridium spp. cause?
C. botulinum = botulism
C. perfringens = gas gangrene/food poisoning
C. tetani = tetanus
C. difficile = pseudomembranous colitis
Give some examples of microorganisms which cause diarrhoea.
Watery diarrhoea
e.g. Bacterial: E.coli (enterotoxigenic), Salmonella typhi, Vibrio cholerae (“rice water” stools)
Viral: Rotavirus, Norovirus,
Parasitic: Cryptosporidium parvum (+ microscopic cysts in stool), Giardia lamblia
Bloody diarrhoea (dysentery)
Bacterial: E.coli (enteroinvasive), Campylobacter spp., Shigella
Parasitic: Entaemoeba histolytica
Outline the structure, transmission, diagnosis, pathogenicity, clinical presentation, and treatment of Legionnaire’s disease.
STRUCTURE = Gram-ve rod, aerobic (Legionella pneumophila)
TRANSMISSION = aerosol of water vapour (found within amoebae & protozoae in water and soil)
PATHOGENICITY = phagocytosed by macrophages but phagosome and lysosome do not fuse —> protected environment —> replicates
DIAGNOSIS = Gram stain/Gimenez stain, urinary & respiratory antigen test
CLINICAL PRESENTATION = acute atypical lobar pneumonia (after travel e.g. to Southern Europe)
TREATMENT = macrolides/fluoroquinolones
Why can fungi not be treated with antibiotics?
Fungi are eukaryotic, not prokaryotic
