Infection Diagnosis and Causes

Questions and Answers

Which of the following infections is typically transmitted vertically?

Toxoplasma gondii

What proportion of cases of Pyrexia of Unknown Origin (PUO) are due to infection?

30%

What is the primary basis for treating MRSA infections?

The results of antimicrobial susceptibility testing

Which of the following bacteria is typically found colonizing the anterior nares and skin?

Staphylococcus aureus Signup and view all the answers

Which of the following antibiotics is NOT typically used to treat milder MRSA infections?

Glycopeptides Signup and view all the answers

What is the classic definition of Pyrexia of Unknown Origin (PUO)?

Temperature above 38.0°C on multiple occasions for more than 3 weeks Signup and view all the answers

What is the primary characteristic used to classify streptococci?

Haemolysis on blood agar Signup and view all the answers

What is the approximate incubation period of Covid-19?

4-14 days Signup and view all the answers

Which group of streptococci is commonly associated with cellulitis in elderly, diabetic, or immunocompromised patients?

Groups C and G streptococci Signup and view all the answers

What percentage of Pyrexia of Unknown Origin (PUO) cases are idiopathic?

15% Signup and view all the answers

What is the hallmark feature of scarlet fever?

Diffuse erythematous rash Signup and view all the answers

What is the primary goal of treating scarlet fever with antibiotics?

To prevent rheumatic fever Signup and view all the answers

Which of the following is a coagulase-positive staphylococcus that causes infection following dog bites?

Staphylococcus intermedius Signup and view all the answers

What is the typical duration of scarlet fever?

7-10 days Signup and view all the answers

What is the main cause of staphylococcal infections?

Staphylococcus aureus Signup and view all the answers

What is the name of the sign characterized by residual petechial lesions in the antecubital fossa?

Pastia's sign Signup and view all the answers

What is the primary cause of morbidity following hospital admission associated with Staphylococcal infection?

Cannula sepsis and thrombophlebitis Signup and view all the answers

What is the mechanism of meticillin-resistance in Staph.aureus?

Penicillin-binding protein mutation Signup and view all the answers

What is the primary location for Staphylococcal biofilm formation?

Plastic surfaces Signup and view all the answers

Which of the following is NOT a type of skin infection caused by Staphylococci?

Pemphigus Signup and view all the answers

What is the primary method of preventing wound infections caused by Staphylococci?

Careful hand hygiene, skin preparation and aseptic technique Signup and view all the answers

What is the treatment for cannula-related Staphylococcal infections?

Cannula removal and antibiotic treatment Signup and view all the answers

What is the name of the Staphylococcal strain that is resistant to vancomycin?

VRSA Signup and view all the answers

What is the primary commensal organism of the skin?

Epidermidis Signup and view all the answers

Study Notes

Infection

Chain of infection: Toxoplasma gondii, Listeria monocytogenes, Treponema pallidium, Parvovirus, HIV, Varicella zoster virus, Rubella, Cytomegalovirus (CMV), and Herpesviruses (HSV) 1 and 2 (TORCH)

Diagnosis

Pyrexia of unknown origin (PUO): temperature above 38.0°C on multiple occasions for more than 3 weeks, without diagnosis, despite initial investigation
Subsets of PUO: HIV-1 related, immune-deficient, or nosocomial
Causes of PUO: Infection (30%), Connective TD (15%), Miscellaneous (30%), Malignancy (20%), Idiopathic (15%)

Bacterial Infection

Incubation periods: 4-14 days for Covid-19
Normal flora: Staphylococci are usually found colonizing the anterior nares and skin
Staphylococcal infections:
- Skin infections: ecthyma, folliculitis, furuncles, carbuncles, bullous, impetigo, and scalded skin syndrome
- Wound infections: many wound infections caused by staphylococci, which may prolong post-operative hospital stays
- Cannula related infections: Staphylococcal infection associated with cannula sepsis and thrombophlebitis
Meticillin-resistant Staph. aureus (MRSA): resistance to meticillin due to a penicillin-binding protein mutation
- Treatment: based on antimicrobial susceptibility testing, may include clindamycin, tetracyclines, co-trimoxazole, glycopeptides, linezolid, and daptomycin

Streptococcal Infections

Streptococci: nasopharyngeal and gut commensals, classified by haemolysis and serotypes
Skin presentations:
- Group A streptococci (GAS): major cause of cellulitis, erysipelas, and impetigo
- Groups C and G streptococci: cause cellulitis, in elderly, diabetic, or immunocompromised patients
- Group B streptococcal (GBS) infection: increasing problem at the extremes of age
Streptococcal scarlet fever:
- Caused by Group A (or occasionally groups C and G) streptococci producing a streptococcal pyrogenic exotoxin
- Common in school age children, can occur in young adults with contact with young children
- Symptoms: diffuse erythematous rash, circumoral pallor, strawberry tongue, and residual petechial lesions in the antecubital fossa (Pastia’s sign)
- Treatment: susceptible antibiotics (Penicillin), which can prevent rheumatic fever but not Poststreptococcal Glomerulonephritis

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Description

This quiz covers the chain of infection, diagnosis of pyrexia of unknown origin, and its causes, including infections and connective tissue diseases. Test your knowledge of TORCH infections and more.