Microbiology and Antibiotic Therapy Flashcards
What colour do acid-fast bacteria stain? Why?
Red due to myocolic acid in cell wall
What are the 3 ways to describe bacteria?
- Shape
- Stain
- Growth requirements
What influences how a bacteria stains on a gram stain?
Gram positive: violet/purple due to thick layer in peptidoglycan cell wall.
Gram negative: stain with safranin (counterstain) due to thinner peptidoglycan cell wall.
How can the growth requirements of bacteria be described?
Aerobic, anaerobic or facultative
What type of bacteria are S. aureus?
Gram positive cocci in a cluster
What type of bacteria are Strep. pneumoniae?
Gram positive cocci in chains, alpha-haemolytic
What type of bacteria are Str. pyrogenes (GAS)?
Gram positive cocci, chains, beta-haemolytic
What type of bacteria are C. difficile?
Gram positive rods
What type of bacteria is Treponema. pallidum?
Spirochaete (corkscrew) shaped and does not take up gram stain easily (atypical stain)
What type of bacteria is Niesseria meningitidis?
Gram negative diplococci
What type of bacteria is E. coli?
Gram negative bacilli
What type of bacteria is Haemophilus influenza?
Gram negative bacilli
What type of bacteria is Helicobacter pylori?
Gram negative bacilli
What type of bacteria is Campylobacter jejuni?
Gram negative bacilli
What type of bacteria is Neisseria gonorrheae?
Gram negative diplococci, intracellular
What type of bacteria is Mycobacterium tuberculosis?
Atypical gram stain, Ziehl-Neelson positive for Acid-Fast Bacillus
What are general systemic observations indicating infection?
Temperature, RR/HR sensitive, BP/shock, pain/symptoms related to body system
Which bloods can be done to indicate infection?
- White cells; neutrophilia more likely bacterial and lymphocytosis more likely viral (NOT COVID)
- CRP
- Cultures, gram stain
Common symptoms of URTI?
Tonsillitis, otitis media, laryngitis, sinusitis Cough Sore throat Rhinorrhoea Nasal congestion Sneezing Headache
Common symptoms of LRTIs?
Bronchitis, pneumonia Productive cough (usually green or yellow) Fever Breathlessness Chest pain Flu-like symptoms, i.e. muscle ache
What are important investigations for a respiratory tract infection?
Sputum culture
Blood cultures
Urinary antigens for atypical pneumonias
CXR
Which bacteria commonly cause CAP, HAP and infective exacerbation of COPD?
Most common: strep. pneumoniae, haemophilus influenza
Less common: staph. aureus
Rare: legionella, mycoplasma
What is 1st line antibiotic for CAP? What would you add if is caused by legionella?
Amoxicillin, add clarithromycin
Which bacteria cause HAP but not CAP?
Pseudomonas aeruginosa & Klebsiella pneumoniae
Which organism causes infective exacerbations of COPD but not HAP/CAP?
Moraxella catarrhalis
What is the difference between HAP and CAP?
To be considered HAP, it must be acquired at least 48 hours into admission.
How would you treat an infective exacerbation of COPD or bronchiectasis?
Doxycycline & prednisolone. May later need amoxicillin.
What is the treatment for pulmonary TB?
6 months RIPE: rifampicin, isoniazid, pyrazinamide (first 2 months only), ethambutol (first 2 months only)
What signs point to infective carditis?
IE specific: splinter haemorrhages, Osler’s nodes, Janeway lesions
Non-specific: Fever, malaise, weakness, petechiae, cardiac murmur, shortness of breath
If you suspect cardiovascular infection, what investigations should you do?
Blood cultures
ECG
CXR
Definitive: ECHO
Which bacteria cause infective endocarditis?
Staph. aureus
Staph. epidermidis
Viridans Streptococci
What is first line treatment for infective endocarditis?
IV flucloxacillin
How should you treat IE caused by MRSA?
IV Vancomycin
What signs may indicate a GI infection?
Diarrhoea (bloody) Nausea + vomiting Abdominal pain Fever Rigors Indigestion/reflux
Which signs may indicate peritonitis?
Diffuse pain and tenderness
Involuntary guarding, rigidity
Rebound tenderness
Which investigations are important for a suspected GI infection?
Stool culture x3 for
MC+S
Ova, Cysts and Parasites
C-urea breath test
Which bacteria commonly cause gastroenteritis?
Campylobacter jejuni
Salmonella
E.coli
Shigella
When do you need to notify public health authorities about a case of gastroenteritis?
Suspected food poisoning or bloody diarrhoea
When should you give antibiotics for gastroenteritis? Which antibiotic should you give?
Ciprofloxacin only if known organism and severe
Which bacteria commonly causes peptic ulcers and reflux?
H. pylori
How do you eradicate H. pylori?
Triple therapy: PPI, amoxicillin, metronidazole
Which symptoms/signs indicate UTI?
Dysuria, change in smell, cloudy urine, suprapubic tenderness/pain
Which symptoms/signs indicate pyelonephritis?
Fever, rigors, N/V, loin to groin pain, writhing in pain on bed (peritonitis)
What investigations should you do if ?UTI/pyelonephritis?
Urine dip
Mid-stream urine (MSU) MC&S
What bacteria are lower UTIs caused by?
E. coli
Occasionally Klebsiella
How do you treat a lower UTI?
Trimethoprim and nitrofurantoin then swap if needed after MC&S comes back. Different for men, women and age.
What skin changes indicate skin infection?
Hot, erythematous, painful, swollen, rapidly spreading, obvious skin wound, fever, rigors
What investigations are important for ?skin infection?
Wound swab MC&S
Blood cultures
What bacteria can cause cellulitis?
Staph. aureus
MRSA
Strep. pyogenes (GAS - group A streptococcal disease)
How do you manage cellulitis?
Draw around infection in permanent marker to monitor.
First line = flucloxacillin -> coamoxiclav
What are symptoms/signs of an STI?
Asymptomatic
Sores/lumps in genital/oral/rectal area, discharge (more, consistency, smell, colour), dysparaeunia (painful sex), dysuria, lower abdominal pain, rash, fever, testicular swelling/tenderness
What investigations would you do for STI?
First-void urine (FVU) nucleic amplification test (NAAT)
Swab MC&S
Serology (HIV, hepatitis, syphilis)
Which bacteria cause chlamydia?
Chlamydia trachomatis
What are complications of chlamydia?
Trachoma
Neonatal conjunctivitis
Reiter’s syndrome (reactive arthritis, urethritis and conjunctivitis)
How do you treat chlamydia?
Doxycycline -> erythromycin
What bacteria causes gonorrhea?
Neisseria gonorrhoeae
Complications of gonorrhea?
Gonococcal ophthalmia neonatorum
Septic arthritis if untreated
How do you treat gonorrhea?
1st line: IM Ceftriaxone
Then ciprofloxacin if sensitivity known
What causes Trichomoniasis?
Trichomoniasis vaginalis protozoan
How do you treat Trichomoniasis?
Metronidazole then trinidazole
What causes syphilis?
Treponema pallidum
How does syphilis progress?
- Primary: painless chancre (genital ulcer)
- Secondary: diffuse rash
- Latent: usually asymptomatic for years
- Tertiary: neurosyphilis & gummas (soft, benign growths)
How do you treat syphilis?
1st line: IM benzathine benzylpenicillin
2: IV benzylpenicillin
What are the signs of sepsis?
Mottled/cyanosed skin Increased RR Tachycardia/hypotension N/V Decreased urination Very high or low temperature Rigors
What are signs of meningitis?
Non-blanching rash Headache Neck stiffness Fever Photophobia/phonophobia Confusion/altered consciousness
What investigations are needed if you suspect meningitis?
Blood cultures
Lumbar puncture analysis
Which bacteria commonly cause sepsis?
Lots! Staph aureus Group A Strep Strep. pneumoniae E. coli Neisseria meningitidis Pseudomonas aeruginosa
Which antimicrobials are used to treat sepsis?
1st line: IV piperacillin with tazobactam (tazocin)
- If MRSA add vancomycin
- Blood cultures to guide narrowing
Which bacteria cause meningitis?
Neisseria meningitidis (meningococcus)
Strep. pneumoniae
Haemophilus influenzae
Antimicrobial treatment for meningitis?
First line: IV Benzylpenicillin (G) URGENT
Can give IM if no venous access
