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1 Does aciclovir prevent the chances of developing herpes zoster (shingles) when given during primary infection?

2 How long does it take after vaccination to become immunized against chickenpox and therefore safe to work in infectious areas?

3 Is meticillin-resistant Staphylococcus aureus (MRSA) the only major hospital-acquired infection?

4 Do you have to have antibiotics to get Clostridium difficile infection?

5 Why do some patients with rheumatic fever later progress to chronic rheumatic heart disease?

6 What is the World Health Organization recommendation for the prophylaxis of rheumatic fever after a streptococcal throat infection?

7 Does rheumatic fever have an infectious or an immunological aetiology?

8 Why is migratory polyarthritis found in rheumatic heart disease?

9 Are penicillins still the drug of choice in streptococcal infections (particularly Strep. Pneumoniae)?

10 1. How long can the antistreptolysin-O (ASO) titre remain positive after a streptococcal infection? 2. What is the effect of a suitable antibiotic on the ASO titre, if any

 Answer 1

There is no evidence that giving aciclovir during the primary infection

(chicken pox) has any effect on the subsequent development of

shingles.

Answer 2

To ensure safety for healthcare workers in this situation, antibody levels

should be checked 1-2 weeks post-vaccination.

Answer 3

No. Vancomycin-insensitive Staphylococcus aureus (VISA), vancomycinresistant Staphylococcus aureus (VRSA) and glycopeptide-resistant

enterococci (GRE) are also problems. Clostridium difficile is another

problem and occurs mainly after taking antibiotics.

Answer 4

Usually. Clostridium difficile is normally carried by approximately 5% of

the healthy population. It can cause diarrhoea after other normal bowel

commensals have been eliminated by antibiotics. In addition, debilitated

patients not on antibiotics can be infected by the faecal-oral route. Patients

and healthcare workers can spread the organism through hand contact,

hence the importance of hand washing.

Infectious diseases, tropical medicine and STI 4

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Answer 5

Antibodies to streptococcal polysaccharides are substantially elevated

and can cross-react with some myocardial tissue antigens. The

pathogenesis is, however, far from clear.

Step-by-step explanation

Answer 6

Phenoxymethylpenicillin 250 mg twice daily until the age of 20 years or

for 5 years after the latest attack. This prevents recurrence and further

cardiac damage.

Answer 7

Both. Rheumatic fever starts with a streptococcal sore throat. It is

followed by an immunological response, which is the result of molecular

mimicry between the M proteins of the infecting Streptococcus pyogenes

and cardiac myosin and laminin. This causes the cardiac lesions. Also, see

next answer.

Answer 8

Migratory polyarthritis found in rheumatic fever is due to the reaction of

the circulating M protein of Streptococcus pyogenes and the synovial

membrane. It is therefore migratory. There is no long-term damage to the

joints.

Answer 9

Penicillin (usually amoxicillin) is the drug of choice for streptococcal

infections. However, resistance to Streptococcus pneumoniae is increasing

(up to 25% in some studies) and you should check your hospital's

antibiotic policy for the appropriate antibiotic.

Answer 10

1. The ASO titre peaks 4-5 weeks after infection. The levels then fall

rapidly with a slower decline after 6 months.

2. Antibiotics have no effect on the levels