Microbiology Flashcards
Why has there been a reduction in children getting infections caused by H.infleunzae?
Hib vaccine
What are the conditions needed for growing H.influenzae colonies?
Chocolate agar - blood agar, heated to 80 deg C
Containing factor 5 + 10
Big cause of COPD exacerbations
H. influenzae
How do mycobacteria differ from normal bacteria?
Intracellular
Alongside RIPE, what should also given in TB?
Vit B6 !
Bc isoniazid depletes VitB6 which causes peripheral neuropathy
Causes Osteomyelitis
Haematogenous - Staph Aureus
Exogenous/Local - Staph Epidermidis !
Why is treating Osteomyelitis so difficult?
How do you overcome this problem?
Vascular supply to bone may be poor
Longer Abx therapy! + using Abx that can penetrate bone tissue
How does the treatment for TB osteomyeltitis and pulmonary TB differ?
Osteomyeltitis TB is longer
12 months not 6
Causes Septic Arthritis
depends on who
Prosthetic joint - staph epidermidis!
Young/sexually active - gonococcal
IVDU - psuedomonas aeuriginosa
Immuno comp - TB
Children - Staph aereus, group A strep and gram -ve bacilli
Skin infections common cause
Most are gram +ve
Staph aereus, strep pyogenes
Soft tissue sepsis presentation?
Inflam cardinal signs of local
Systemic - fever, sweats, rigors
What layer does cellulitis affect?
SC tissue
Who does cellulitis tend to affect?
Patients with :
Ulcers - Vascular / DM patients
Tinea pedis
Obesity
SKin conditions - eczema
Cause Cellilitis
Strep Pyogenes
Staph aureus
What MUST you distinguish cellulitis from?
DVT !!!!!!!!!!!!!!!!!!!
Ix Cellulitis
Clinical diagnosis
Blood culture - ↑vol sample, more than 1 size and more than 1 time
Tx Cellulitis
Flucloxacillin
1st Line ABx treatment for staph aureus
Flucloxacillin
Lowenstein-Jensen
Stains for?
Myco TB
Blood agar
for?
Anaerobes
e.g. fusobacteria
Charcoal agar
For?
Campylobacer jejuni
Chocolate agar
For?
Anaerobes
e.g. S. pneumoniae
MacConkey
Stains for?
Lactose Fermenting bacteria
Pathogen causing Pneumonia?
Strep Pneumoniae
Pathogen causing Bronchitis?
Adenovirus - Acute
Rhinovirus - Chronic
Define pathogen
Organism that causes disease
Define commensal
Organism that colonises host but causes no disease normally
Define Opportunist pathogen
Microbe that only causes disease if host defence is compromised
Define Virulence or Pathogenicity
The degree to which an organism is pathogenic
Describe the stages of Gram staining
Come In And Stain
- Fixate to microscope slide with heat or methanol
- Apply Crystal violet - all cells turn purple
- Apply Iodine (Mordant) - crystal violet-iodine complexes form
- Use Alcohol (acetone or ethanol) to decolourise and distinguish between +ve and -ve
- Apply counterstain Safranin to stain Gram -ve pink
Why does Gram +VE stain purple?
Thick layer of peptidoglycans
What is coagulase?
Enzyme produced by S. Aureus that converts soluble fibrinogen to insoluble fibrinogen
Why might you use Beta Lactams or Glycopeptides against gram pos bacteria?
there’s others u can use, not only for gram pos - but why miiight you?
Because Beta Lactams and Glycopeptides inhibit cell wall synthesis
Gram +ve bacteria have thick cell walls!!! make them vulnerable!!!!!!
If penicllin is CI (bc penicllin allergy), what might you use instead?
Macrolides
Why is folate important for the baby during pregnancy?
Prevents spine bifida!!
What Abx for MRSA?
Vancomycin
What are mycobacteria?
Aerobic, non-spore forming, non-mobile bacilli
How to identify virsuses?
PCR + nucleic acid amplification tests (NAAT)
OR serology
Why can’t you culture viruses?
Bc only reproduce inside live cells
3 groups of worms
Nematodes - roundworms
Trematodes - flatworms
Ceratodes - tapeworms
How can adult worms replicate?
Can only replicate inside body if they have a period of development outside body
Which stain is used for Mycobacteria?
Ziehl-Neesen
Examples of protazoa
Malaria
Giardia Lamblia
Toxoplasmiosis
How are protozoae classified?
On movement
State the classes of protozoa
Ameoboids
Ciliates
Sporozoan
Flagellates
Describe the cell wall of fungi
Chitin + Glucans
How do fungi move?
Either growing across or through structures
OR dispersion in air or water
Describe the forms in which fungi can exist
Yeast - single cell that divides via budding?
Moulds - form multicellular hyphae or spores
What do anti-fungals target?
Cell wall or plasma membrane
“-azole” -
^but also this isnt true cos metronid”azole” targets parasites so idk
Regarding worms, what is the pre-patent perioid?
Interval between infection + appearance of eggs/larvae in stool
Describe the immune response against worms
Poor
Mainly IgE + IgG mediated
Examples of worms
Hookworm
Schistosmoiasis
Cause of Pharyngitis
Strep. Pyogens
Comps of Pharyngitis
Peri-tonsillar abscess
Sinusitis
Cervical lymphadenitis
Rheumatoid fever
Glomerulonephritis
How to detect bacterial causes of phayngitis?
Culture of charcoal throat swab
How to test for rotavirus?
Antigen detection on stool sample
How does rotavirus present?
DIarrhoea
How to test for EBV or haemolytic strep?
Venepuncture for acute phase serology
Comp of GB
RESP FAILURE
ALWAYS CHECK FEV1 AND FVC
What is adenocarcinoma derived from?
Bronchial mucus glands
What cells regenerate?
Hepatocytes
Pneumocytes
All blood cells
Gut epithelium
Skin epithelium
Osteocytes – help remodel bone fractures
Shingles
Sx Sx
Cause
grrrrrrrrrr
Painful red rash confined to single dermatome
VZV
What does EBV cause?
Glandular fever
DDx Glandular fever
Step pyogens throat infection
aka pharyngitis
How does glandular fever present?
Strep. pyogens also presents the same btw
White/Yellowish purulent lining over tonsils
How to diff between Strep Pyogens throat infection and glandular fever?
Strep pyogens - take a black charcoal swab !
Ix Glandular fever
FBC - atypical lymphocytes (basophilic cytoplasm + prominent nucleus)
Serology for EBV Ig with clotted sample
Main AIDS defining illnesses
PNEUMOCYSTITIS JIROVECCI
CMV colitis
Oral candida (thrush)
Lymphomas
Tx Pneumocystitis Jirovecci
Co-trimoxazole (aka septrin)
+ prednisolone if T1 resp failure
CMV Tx
IV ganciclovir
MC cause of meningitis
Enterovirus!!
Atypical pneumonia is resistant to?
Amoxicillin
Tx Atypical pneumonia
Macrolides (erythromycin, clarithryomycin)
Fluroquinolone (ciprofloxacin)
Tetracycline (doxycycline)
1st line for Legionella
Clarithromycin
H. influenzae Tx
Amoxicillin
Co-amoxiclav
S. pneumoniae Tx
Amoxicillin
H. influenzae grown on what agar?
Chocolate agar as fastidious bacteria
TB Histology
Granuloma with central caseating necrosis
Other granulomatous causes?
How do these differ from TB?
Sarcoidosis, Crohn’s, Leprosy
NON-CASEOUS
Mucus colour for brochiectasis
Yellow normally
Green if exacerbations
P. aeruginosa Tx
Brochiectasis
Piperacillin + tazobactem
Soft tissue infection patho
Pathogens enter soft tissue through breach in skin
Erysipelas Bacteria cause
S. pyogens
s. Agalactiae
S. aureus
Impetigo presentation
Honey-coloured, clustered, crusty lesions on chin and cheeks of young person
Itchy growing spot which keep scratching
Otherwise well
Swab for impetigo
Black charcoal
Cause impetigo
S. pyogens
S. aureus
mainly
Tx impetigo
Flucoxacillin
or benzylpenicillin if s. pyogens only?
MRSA Ix
Chromogenic axilla and groin swab taken on admission
Tx MRSA
Vancomycin or Teicoplanin
2 weeks IV ABX MINUMUM
If sus IE - 6 weeks minimum
What drugs can cause nephrotoxicity?
Vancomycin
Teicoplanin
Gentamycin (also ototoxic)
Uncomp UTI Tx
Trimethoprim 200mg 2xd for 3 days
or
Nitrofurantoin 50mg 4xd for 3 days
What is an important thing to note when doing urinalysis?
Why?
NEVER on catheterised sample urine
Bc bacteria likely present in all CSU samples regardless of infection or not!
Whereas midstream urine is reliable as urinary tract is normally sterile!S.
S. Viridans Tx
IV Benzylepenicillin 4-6 weeks
+/- gentamicin 2 weeks
MC cause of IE
S. aureus
Comp IE
Septicemboli!
Stroke/PE etc
