Infectious Disease Flashcards
(302 cards)
Name a few Gram (+)ve & (-)ve cocci
Gram (+): Staphylococci & Strepto (including Enterococcus)
Gram (-):
- N meningitidis
- N gonorrhoea
- M catarrhalis
Gram (+)ve rods ??
ABCD-L
- Actinomyces
- Bacillus anthracis
- Clostridium
- Diphtheria
- Listeria monocytogenous
Gram (-)ve rods ??
E coli
H influenzae
P aeruginosa
Salmonella species
Shigella species
C jejuni
Difference b/w Endotoxins & Exotoxins ??
Exotoxins:
- SECRETED by the bacteria
- Generally released by Gram (+)ve bacteria (except V Cholera & some strains of E coli)
ENDOTOXINS :
- Only released after the LYSIS of cels
Types of toxins ??
Classified by their Primary effect
- Pyogenic toxin
- Enterotoxins
- Neurotoxins
- Tissu Invasive toxins
- Miscellaneous toxins
Features of Pyogenic Toxins ??
Stimulates release of Endogenous Cytokines => Fever, Rash
- They are SUPER-ANTIGENS which bridge MHC Class 2 on APCs with T-cell receptors on T cell surface => Massive Cytokine release
Staph. Aureus
- TSST-1
- High fever, Hypotension, Exfoliative rash
Strept. pyogenous
- Strept. pyogenic exotoxin A & C
- Scarlet fever
Features of Neurotoxins ??
Act on Nerve (Tetanus) of NMJ (Botulism) => Paralysis
C TETANI
- Tetanospasmin
- (-) GABA & Glycine release from Renshaw cells of S Cord => Continuous Motor neuron activity => Spastic Paralysis
C BOTULISM (Canned food & Honey)
- B toxin
- (-) ACh release => Flaccid paralysis
Features of Tissue Invasive Toxins ??
C PERFRINGENS
- Alpha-toxin (Lecithinase)
- Gas gangrene (Myonecrosis) & Haemolysis
- Tender, edematous skin + Bloody Blebs & Bullae +/- Crepitus
STAPH. AUREUS
- Exfoliatin
- Staph. Scalded Skin Syndrome
Features of Staphylococci ??
Normal commensal organism
- Gram (+)ve cocci
- Facultative Anaerobes
- CATALASE (+)ve
2 TYPES
Staph. aureus
- Coagulase (+)ve. - Cellulitis, Abscesses, Osteomyelitis, TSS
Staph. Epidermidis
- Coagulase (-)ve
- Central Line Infection & Infective Endocarditis
Features of Staph. TSS ??
Severe systemic reaction to Staph. EXOTOXINS- TSST-1 Superantigen
- Infected Tampons
Dx. Criteria
- Fever > 38.9 C. - SBP < 90mmHg
- Diffuse Erythematous rash
- Desquamation of Palms & Soles
- >= 3 organs involved
Rx.-
- Remove Infection Focus
- IV Fluids. - IV Antibiotics
Hallmark of MRSA ??
All pts. waiting for Elective admission & All emergency admissions Must be screened for MRSA
- Nasal swab & Skin lesion or Wounds
- Swab wiped around the rim of pts. nose for 5 sec.
How to treat MRSA carriers ??
NOSE : Mupirocin 2% in white paraffin, TDS for 5 days
SKIN: Chlorhexidine Gluconate OD for 5 days
- Apply all over but particularly to Axilla, Groin & Perineum
Rx. of MRSA infection ??
MC used Antibiotics are
- Vancomycin / Teicoplanin / Linezolid
The following even though found sensitive should not be used due to devt. of Resistance
- Rifampicin. - Tetracyclines
- Aminoglycosides. - Clindamycin
Linezolid, Quinupristin/Dalfopristin & Tigecycline are reserved for Resistant cases
Features of Streptococci ??
Gram (+)ve cocci; Classified based on Haemolysis pattern
ALPHA (Partial H, Green)
- Viridans Streptococci (No capsule) eg.- S mutans, S mitis & is (-)ve for Optochin sensitivity & Bile solubility
- S pneumonia (Encapsulated) is (+)ve for Optochin & Bile solubility
BETA (Complete Haemolysis, Clear)
- Grp. A (S pyogenes) is (+)ve for Bacitracin sensitivity & PYR status
- Grp. B (S agalactiae) is (-) for Bacitracin & PYR status
GAMMA (No Haemolysis, grows is Bile
- Nonenterococcus (S gallolyticus) is (-)ve for PYR status & Growth in 6.5% NaCl
- Enterococcus (E faecium, E faecalis) is (+)ve for the above 2 tests
Group A & B Streptococci ??
Grp. A
- Most imp. organism is S pyogenes
- Causes Erysipelas, Impetigo, Cellulitis, Type 2 Nec. Fasciitis, Pharyngitis & Tonsillitis
- Immune reaction can cause Rheumatic Fever or PSGN
- Erythrogenic toxin: SCARLET Fever
Grp. B
- S agalctiae
- NEONATAL Meningitidis & Septicaemia
Name the Organisms a/w the following virulence factor
- IgA Protease
- M Protein
- Polyribosyl ribitol phosphate capsule
- Bacteriophage
Virulence factors colonize the host & evade/ suppress the immunity
- Strep. Pneumonia, H influenzae, N gonorrhoea
- Strep. pyogenes
- H influenzae
- C diptheriae
Name the Organisms a/w the following virulence factor
- Spore formation
- Lecithinase Alpha Toxin
- D-Glutamate Polypeptide Capsule
- Actin Rockets
- B anthracis, C perfringens, C tetani
- C perfringens
- B anthracis
- Listeria monocytogenes
Hallmark of Cellulitis
Inflammation of Skin & Subcutaneous tissue due to Strep. pyogenes or Staph. aureus infection
- Site: Shins
- Erythema, Pain, Swelling
- Systemic upset- Fever
Clinical Dx; Bloods & Blood cultures needed if Admitted & Septicaemia is suspected
Criteria for admission in Cellulitis ??
Eron Classification
CLASS 1 :
- No signs of systemic toxicity
- No uncontrolled Co-morbidities
CLASS 2:
- Systemically Unwell/ Well but has Co-morbidity (PAD, Morbid Obesity, Chr. Venous Insufficiency); can complicate/ delay infection resolution
CLASS 3:
- Significant Systemic upset (OR)
- Unstable Co-morbidity that may interfere with Rx. response (OR)
- Limb threatening infection due to Vascular comprise
CLASS 4:
- Sepsis syndrome (OR) Severe life threatening infection (Nec. Fasciitis)
When should we admit pt. for IV Antibiotics ??
- Eron Class 3 or 4
- Severe rapid deteriorating Cellulitis
- Very Young (< 1yr) or Frail
- Immunocompromised
- Significant Lymphoedema
- Facial Cellulitis (unless very mild) or Periorbital Cellulitis
How is Eron Class 2 cellulitis managed ??
Admission not necessary if
- Facilities & Expertise are available in the community to give IV Abx. & monitor the patient
Other pts., can be treated with Oral Abx.
DoC for Cellulitis ??
1st line: FLUCLOXACILLIN (Mild to moderate)
- Clarithromycin, Erythromycin (in Pregnancy) or Doxycycline is used in pts. allergic to Penicillin
Severe Cellulitis
- Co-Amoxiclav. - Cefuroxime
- Clindamycin. - Ceftraixone
Hallmarks of Nec. Fasciitis ??
Medical emergency; 2 types
TYPE 1 (MC type)
- Mixed anaerobe & Aerobes
- MC Post-Sx in Diabetics
TYPE 2 - Strepto. Pyogenes
RFs
- Skin trauma, Burns, Soft tissue infection
- IV Drug use. - Immunosuppresion
- DM (especially if Pt. is on SGLT-2 i)
Features & Rx. of Nec. Fasciitis ??
Acute onset; Pain, Swelling, Erythema
- Rapidly worsening cellulitis with pain out-of-keeping with findings
- Extremely Tender + Hypoasethesia to light touch
Late signs
- Skin necrosis, Crepitus/Gas gangrene
- Fever & Tachycardia
TREATMENT
- Urgent Surgical Referral for Debridement & IV Antibiotics