Eradicating Bacteria

Empirical antibiotics should be started after initial blood cultures are drawn based on the common pathogens suspected for the particular patient group.

Eradicating bacteria

It is difficult to eradicate bacteria, as they reside in avascular areas thereby escaping host defences. They may be dormant and relatively inactive if located deep within vegetations, and patients are prone to repeat infections from subsequent embolisation and re-seeding. Keeping this in mind high concentrations of bactericidal antibiotics are needed for prolonged periods to attempt ultimate eradication. Usual regimes last 4-6 weeks for native valves and 6-8 weeks for prosthetic ones. It is very important that antibiotics are tailored to cultures and sensitivities of bacteria in order for treatment to be effective, and therefore consultation with local microbiology team is essential.

Antibiotics

Penicillin or Cephalosporins are usual first-line antibiotics, with Vancomycin for cases of MRSA (Methicillin Resistant Staphylococcus aureus) or Penicillin allergy. Good laboratory support with precise MIC (Minimum Inhibitory Concentration) estimation can help tailor dosage of Penicillin so that adequate serum concentrations can be achieved. Gentamicin is frequently used in the acute phase for its synergistic interaction with Penicillin. Regular discussion with microbiologists should aid appropriate treatment planning [4].

Regular blood cultures

Once antibiotic therapy is commenced, regular blood cultures should be taken, as they become negative with effective therapy. Temperature usually settles in 6-7 days, quicker with Penicillin than Vancomycin.

Persistent temperature

Persistence of temperature beyond 7 days should lead to re-evaluation of the patient: repeat echocardiography to rule out abscess formation, and appropriate evaluation of extra cardiac structures to look for abscess and embolic phenomena.

Ceftriaxone is widely used for its convenience (less frequent dosage requirement) and wide cover of most organisms including the HACEK group.

Fever with sterile blood cultures could result from drug-associated fever or reaction and this should be kept in mind. Effective treatment reduces incidence of embolic phenomenon from 13 per 1000 patient days in the first week of treatment to 1.2 per 1000 patient days in the third week of treatment [4]. Therefore, persistence of fever or occasional embolic phenomena are not, of themselves, necessarily an indication of treatment failure.

The size of valvular vegitation

The size of valvular vegetation is not correlated with cure and is a poor indicator of effectiveness of treatment. Though most vegetation reduces in size with effective therapy, some remain unchanged, and 25% actually increase in size at 3 months.