Microbiology Flashcards
What colours are gram +ve and gram -ve bacteria?
Gram +ve = purple
Gram -ve = pink
Why does gram +ve stain purple and not pink?
because contains thick layer of peptidoglycans in cell wall
What are the two big groups of gram +ve bacteria and how can you distinguish them?
Staphylococci and Streptococci
Catalase test
OR under a microscope (strep = chains, staph = clusters)
How can you distinguish Streptococci?
Haemolysis test - grow on blood agar
What are the types of Streptococci and how do they appear?
Alpha haemolytic - partial/green
Beta haemolytic - full/clear
Gamma haemolytic - none
Name an important alpha haemolytic streptococci and how would you differentiate this from other a-strep ?
Strep. pneumoniae
Optochin susceptibility test = strep. pneumoniae
If resistant, strep. viridans
How is beta haemolytic strep differentiated?
Lancefield grouping
What organism is in group A of Lancefield grouping that is resistant to optochin?
Streptococcus pyogenes
How does Staph. aureus appear on blood agar?
Gold colonies
How do you differentiate between types of Staph bacteria?
Coagulase test
How do you distinguish Gram -ve bacteria?
- MacConkey / XLD / CLED agar
What are the big boy lactose fermenters?
Klebsiella pneumoniae and E. Coli
How do you distinguish non-lactose fermenters?
Oxidase test!
Pseudomonas is oxidase +ve
ESQ -
It is reported that the organism from the sample you sent is a Gram -ve cocci. What organism are you worried about?
Neisseria Meningitidis
What unusual organism can cause infective endocarditis?
Coxiella burnetti
What Tx is prescribed for a Staph-induced infective endocarditis?
IV benzylpenicillin + gentamycin
What Tx is prescribed for a Strep-induced infective endocarditis?
IV flucloxacillin + gentamycin
What is the most common cause of CAP?
Streptococcus pneumoniae
Other common causes of CAP
Staph. aureus, viruses
Atypical causes of CAP
Chlamydia psittaci
Chlamydia pneumoniae
Coxiella burnetti
Mycoplasma pneumoniae
Legionella pneumophilia (SPAIN, A/C, HOLIDAYS)
If legionella is indicated in history for CAP, what do you do?
Urinary Ag
First line for legionella CAP?
Clarithromycin
First line for strep. pneumoniae CAP?
Amoxicillin
Causes of HAP
Same as CAP
+
Staph. aureus (and MRSA)
Klebsiella pneumoniae
Pseudomonas aeruginosa
What antibiotic might you use if someone has a pneumonia causes by MRSA? Why?
Vancomycin - broad spectrum Abx
Big boi cause for COPD exacerbations
H. influenzae
Agar for growing H. influenzae colonies
Chocolate agar
(blood agar heated to 80oC, has factors X + V for growth)
Why is there a reduction in children getting infections caused by H. influenzae?
Hib vaccine
Most common cause and other causes of TB
**Mycobacterium tuberculosis
Mycobacterium bovis/africanum/microti
How is mycobacteria different from normal bacteria?
Intracellular
TB : test for rifampicin resistance?
PCR Xpert
When is the mantoux test positive?
In Px w/ latent TB and those who have has BCG vaccination
Alongside RIPE, what should you give?
Vit B6 bc isoniazid depletes Vit B6 - causes peripheral neuropathy
Causes of osteomyelitis : haematogenous spread
Staph. Aureus
Causes of osteomyelitis : exogenous/local spread
Staph. Epidermis, pseudomonas aeruginosa
How does treatment vary between Osteomyelitis TB and pulmonary TB?
Tx for Osteomyelitis TB is longer (12 months instead of 6)
Cause of septic arthritis
Prosthetic joint
gram +ve bacteria (mostly staph - Staph epidermis)
In children, staph aureus, group A strep, gram -ve bacilli
Main bacteria in skin infections
Gram +ve bacteria
Staph. Aureus, Strep pyogenes
What MUST you distinguish cellulitis from?
DVT
What is given to treat cellulitis and why?
Penicillin V (phenoxymethylpenicillin) + flucoxacillin
Flucloxacillin bc covers both strep and staph
Types of necrotising fasciitis
TYPE 1 : Polymicrobial - mix of anaerobic (clostridium perfringens) + aerobic bacteria
TYPE 2 : Single bacteria (esp. Group A strep)
1st line antibiotic for staphylococcus aureus infection?
Flucloxacillin
Name common organisms of meningitis
Neisseria meningitidis
Strep pneumoniae
Group B streptococcus
Common causes of UTI
**E. coli
Klebsiella
Enterococci
Name 2 anti-fungal treatments
Clotrimazole, fluconazole
micro tbd
Antibiotics: bacteriostatic vs bactericidal, resistance, mechanism of action
Malaria
HIV (know one of each treatment class: e.g. protease inhibitors)
(Tropical diseases)
(Helminths)
Soft tissue infections: impetigo + erysipelas + abscesses (staph. Aureus)
Neurology: rabies, tetanus, botulinism, polio
Resp: URTI, LRTI, influenza
Fungal infections (e.g. aspergillosis)
GI: serological findings of viral hepatitis
