Microbiology Flashcards
What is the causative agent of Rheumatic fever?
S. pyogenes (GAS) pharyngitis
What is an important adhesin to keratinocytes?
M protein
What is the name of the structure that may allow Group A strep GAS to bind to the host HA receptor CD44 found on the surface of pharyngeal epithelial cells?
The hyaluronic acid (HA) capsule
What are the functions of the proteins produced by Group A streptococcus ?
- To degrade chemotoxins that recruit neutrophils to the site of infection
- inactivate or degrade antibodies
- block antimicrobial peptide function
What are the functions of M proteins?
M proteins prevents opsonization by complement through two mechanisms.
-1.Binds the host cell plasma protein, fibrinogen, which interferes with the alternative pathway of complement deposition by forming a dense layer on the bacterial surface.
- Binds host complement control proteins that inhibit the formation of opsonins by the complement cascade
What s the best prevention method of antibiotics?
Correct use of antibiotic
What is the age range for patients to develop rheumatic fever?
5 and 15 years old
Fill in the blanks. “Group A strep pharyngeal infection precedes clinical manifestations of RF by _______.”
2-6 weeks
What are the most important antigenic proteins in external layer of cell wall?
M, R & T proteins
What are the clinical features of Rheumatic Fever?
Arithritis
Carditis
Sydenham’s chorea
Erythema marginatum
Subcutaneous nodules
Arthralagias
Epistaxis
Serositis
What is the criteria used in the diagnosis of Rheumatic Fever?
Jones criteria
What is the most common feature of Rheumatic Fever?
Arthritis
What are the joints preffered in arthritis?
Knees, ankles ,wrists, elbows , shoulders
What is the most serious manifestation of rheumatic fever?
Carditis
What are the clinical signs of Carditis?
High pulse rate
Murmurs
Cardiomegaly
Rhythm disturbances (prolonged PR interval)
Pericardial friction rubs
Cardiac failure
What are the most common lesions in Carditis?
Mitral and aortic valves regurgitation
What are the clinical features of Sydenham’s Chorea?
Extrapyramidal disorder
- Fast ,clonic, involuntary movements(epecially face and limbs)
- Muscular hypotonus
- Emotional lability
What is the normal length of subcutaneous nodules?
.5-2 cm long
Fill in the blanks. “ Subcutaneous nodules are most common along ______.”
Along extensor surfaces of joints
- Knees ,elbow, wrists
What are other locations of subcutaneously nodules?
On bony prominences, tendons, dorsi of feet, occiput or cervical spine
Where is the common location of Erythema Marginatum?
Trunk ,abdomen ,Inner arms or thighs
What are the features of the cutaneous lesions seen in Erythema Marginatum?
- Reddish pink border
- Pale centre
- Round or irregular shape
What are the major criteria seen in Rheumatic Fever?
- Arthritis
- Carditis
- Sydenham ‘s chorea
- Erythema marginatum
- Subcutaneous nodules
What are the minor criteria seen in Rheumatic Fever?
- Fever
- Arthralgia
- Elevated c-reactive protein or
- Elevated erthrocyte sedimentation rate
- Prolonged PR interval on ECG
How is the Jones criteria used in the diagnosis of Rheumatic fever?
- Evidence of previous infection with strep upper airway infection and
- 2 major criteria or
- I major criteria and 2 minor criteria
What are the antibodies present in Rheumatic fever ?
Antistreptolysin O antibody
Anti DNAase B titer, anti-hyaluronidase, anti –streptokinase anti-nicotinamide, streptozyme screen
What are the different tests that can confirm /give a documented evidence of recent GAS infection?
- Positive throat culture or specific nucleic acid based test.
- Detection of GAS antigen in a throat swab
- An elevation of anti-ASO ,anti-DNase B, anti-hyluronidase antibodies.
What is the best treatment for Rheumatic Fever to eradicate GAS?
Single dose IM benzathine penicillin G
Which drug should be given for treatment of RF to eradicate GAS in patients with a Penicillin allergy?
Oral clindamycin
Which drugs DO NOT eradicate Group A streptococcus?
SULFA-DERIVED ANTIBIOTICS
What is the treatment for arthritis seen in RF?
Salicylates or NSAIDs x 3 weeks
What is the treatment for carditis seen in RF?
Steroid use compulsary
* Prednisone 1-2 mg /kg/d (max 60 mg) x 10- 15 d
* Taper
What is the treatment of Sydenham’s Chorea?
Haloperidol .5-1 mg/kg
Alternate - sodium valproate 15-20 mg/kg/d
What are the clinical features of Group A strep infections?
Sudden-onset sore throat , pain on swallowing , malaise, high fever, abdominal pain, soft palate petechiae, vomiting, nausea