Infectious diseases notes summarising all infectious pathologies for medical school examinations. Note there is also a slight excess in specialist knowledge for medical school examinations.
Look at specialty section and content list for the summary contents of this file.
Staphylococci
Description Pathology
- Commensal: Skin / nasal commensal in ~80 % - S. aureus
- Coagulase: +ve organisms are more severe infx. o Toxin: Scald Skin Syn. (Bullae + desquam.)
- NB: S. epidermidis commonest CVC infx isolate o Food Toxin: Sudden D&V within hours
Metabolic o Toxic Shock: ↑TO; ↓GCS; Rash; V&D; Tampon
- Gram Stain: Positive o Soft Tissue: Impetigo; Cellulitis; Mastitis
- Aerobic: Facultative Anaerobes o Bony Tissue: Septic arthritis; Osteomyelitis
- Enzymes: Catalase ± Coagulase - S. saprophyticus
Coagulase o GUT: UTI ➔ Cystitis
- +Ve: S. aureus - S. gallinarum
- -Ve: S. epidermis; S. saprophyticus; S. gallinarum o Eye: Endophthalmitis (rare)
Diagnosis Management
- MC&S: Take sample from site of infection - MSSA: Flucloxacillin
- Novobiocin: Can differentiate - MRSA: Glycopeptide; 4 % CHG + Nasal Mupirocin
- NB: epidermidis (sensitive); saprophyticus (resistant) - VRSA: Linezolid; 4 % CHG + Nasal Mupirocin
Enterococcus Faecalis (Formerly Group D Streptococcus)
Description Management
- Commensal: Gut commensals - Key. E. Faecalis is sensitive to ampicillin but E.
- NB: Enterococcus formerly known as Group D Strep. faecium is resistant
Pathology - Endocarditis: Amoxicillin/Benzylpenicillin + Gent.
- UTI: Over 30 % of all bacterial UTIs - Meningitis: Intrathecal vancomycin (NB: VRE exist)
- Endocarditis: Assume if detected in blood - UTI: Nitrofurantoin (regardless of VRE)
- Meningitis: Rare neurosurgical complication - AMR: Resistant to cephalosporins and quinolones
Streptococci
Description Pathology
- α-Haemolytic: Haemoglobin ➔ Biliverdin (green) - S. pneumoniae
- β-Haemolytic: Haemoglobin ➔ Complete haemolysis o Lungs: Pneumonia
- Grouping: Lancefield group of β-Haemolytic o ENT: Otitis media
Species - S. pyogenes
- Non-Haemolytic/Non-typable Lancefield: S. viridans o Systemic: Scarlet fever; Peripartum sepsis
- α-Haemolytic: S. pneumoniae; S. viridans o ENT: Tonsillitis; Pharyngitis;
- β-Haemolytic group A: S. Pyogenes o Skin: Impetigo; Erysipelas; Cellulitis; NF
- β-Haemolytic group B: S. agalactiae o Complications: RHD; GN; Toxic shock
- β-Haemolytic group D: S. gallolyticus; S. bovis - S. viridians
- β-Haemolytic group F: S. milleri complex o Heart: Endocarditis (from dental caries)
Management - S. gallolyticus
- Pneumonia: Amoxicillin o Heart: IE
- RHD: Penicillin V o Risks: Colon/Liver disease; CRC
- Skin: Fucloxacillin - S. milleri
- Endocarditis: Benzylpenicillin + Gentamicin o Abscesses: Lung; Liver; Bartholin’s
,Clostridia
Description Pathology
- Spores: Resilient Spores - C. difficile
- Aerobic: Obligate anaerobe o GI: Bowel infection – See relevant notes
- NB: C. botulinum can tolerate low levels of O2 - C. botulinum
Species o Nerve: Botulism – See relevant notes
- Gut: C. difficile - C. tetani
- Skin: C. perfringens (formerly C. welchii) o Nerve: Tetanus – See relevant notes
- Nerve: C. botulinum; C. tetani - C. perfringens
Management o Muscle/Skin: Gas/Fournier’s gangrene (α-toxin)
- Basic: Early recognition and surgical debridement o Sx: Crepitations heard over gangrene
- C. Diff: Metronidazole; Vancomycin; Fidaxomicin o Risks: GI surgery; Open fracture; malignancy
Diphtheria
Description Investigation
- Location: E. Europe; Russia; Asia - MC&S: Culture/PCR
Species - Serology: Toxin detection
- Species: Corynebacterium diphtheriae Management
Pathology - Key: Airway control
- Emergency: Tonsillar (grey) pseudomembrane - Antitoxin: Give within 48 hrs
- Sx: Fever; Odynophagia; Cervical lymphadenopathy - Abx: IM Benzylpenicillin / Erythromycin
Actinomycosis
Species Pathology
- Species: Actinomyces israelii - Subacute: Granulomatous/suppurative infx
Management - Location: Occurs adjacent to mucous membrane
- Abx: Penicillin - NB: Sulfur granules in pus/tissue characteristic
Neisseria meningitidis
Description Investigations
- Commensal: URT in 10 %; 25 % of teens - Microscopy: CSF; Blood; Skin lesion biopsy
- NB: Adheres to non-ciliated epithelial cells - NB: Intra/Extra-cellular diplococci
- Transmission: Aerosolized droplets Management
- Virulence: Serotypes ABCWY are virulent - Meningitis: Dexamethasone
- Microscopy: Gram negative diplococci - Prevention: Group B vaccination; ACWY at 14 YO
- Risks: Age; Complement defects; HIV; ↓Spleen - Abx: Ceftriaxone; Benzylpenicillin
Pathology - Prophylaxis: Ciprofloxacin/Ceftriaxone one dose
- Meningitis (50 % of cases) - Alternative: Rifampicin BD for 48 hrs
o Initial Sx: Headache; N&V; Malaise Complications
o Late Sx: Neck rigidity; Photophobia; ↓ GCS - Meningitis: ≥25 %; SNHL; Epilepsy
- Meningococcaemia - Systemic: AKI; ARDS; Thrombosis; Pneumonia
o Mild Sx: Fever; Macular rash; No shock signs
o Severe Sx: ↑To; Septic shock; Coagulopathy
Moraxella
Description Pathology
- Commensal: URT coloniser in children (↓ in adults) - Lungs: Bronchitis; Sinusitis; Laryngitis
- Risks: COPD; Elderly - ENT: Otitis media (esp. in children)
Species - Systemic: Septicaemia ➔ IE (20 % mortality)
- Species: Moraxella catarrhalis - MSK: Septic arthritis (rare)
Investigations Management
- MC&S: Sputum; Ear effusion; Sinus aspirate; Blood - Abx: Macrolide; Cephalosporin
- NB: Hockey puck sign (colonies move around on agar)
Escherichia coli
Description Pathology
- Commensal: Part of normal colonic flora - Enterotoxigenic: Traveller’s diarrhoea
- Pathogens: Many different pathogenic forms - Enterohaemorrhagic: D + haemorrhagic colitis
- Character: Facultative anaerobic; Lactose fermenter - Enteropathogenic: Esp. infants in poor sanitation
Management - Enteroinvasive: Dysentery-like syndrome
- Abx: TMP; Ampicillin; Cephalosporin; Ciprofloxacin - Enteroadherent: Traveller’s diarrhoea; Chronic D
- NB: ESBL and CRE commoner in E. coli strains - Extra-intestinal disease: Neo. sepsis; Pneumonia
Klebsiella pneumoniae
Description Pathology
- Commensal: Skin; Nasopharynx - Lungs: Pneumonia (alcoholics; Dysphagia pt.)
- Risks: Abx exposure; Catheter; ↓ Immunity - ENT: Nasopharyngitis
- NB: Very contagious in prolonged close quarters - GUT: UTI
Management - Complications: Sepsis + Necrosis if ↓ Immunity
- Abx: Aminoglycoside; Cephalosporin; Carbapenem
- Note: ESBL and CRE commoner in K. pneumoniae
Proteus mirabilis
Description Pathology
- Stones: Colonise stones formed in GUT - GUT: UTI (see Nephrolithiasis notes in urology)
- Metabolic: Urease which ↑ risk of stone formation - Risks: Struvite; Calcium oxalate; Uric acid stones
- Sex: More common in men - Complications: Renal calculi ➔ AKI
Presentation Management
- Signs: Alkaline urine; Fishy odour - Abx: Gentamicin; Carbapenems; Cephalosporins
Investigations - Resistant: Tetracycline; Nitrofurantoin
- Culture: Urine culture - NB: 10-20 % are resistant to ampicillin
- Microscopy: Characteristic swarming motility
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller sk25. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $10.97. You're not tied to anything after your purchase.