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These guidelines have been produced following a literature review of the requirement for prophylaxis to prevent bacterial endocarditis following dental and surgical interventions. Recommendations are made based on the quality of available evidence and the consequent risk of morbidity and mortality for ‘at risk’ patients.

A novel beta-lactamase activity which confers resistance to expanded-spectrum cephalosporins and penicillins has been found in strain IC 5/21 of Capnocytophaga spp. Enzyme activity migrated at a molecular size of 38,000 daltons and at an isoelectric point of 3.6, with a minor band at 4.1. Kinetic studies suggested that it belonged to Richmond and Sykes beta-lactamase class 1c. Isoelectric focusing could be achieved only if a nonionic detergent was added to the gel, suggesting the presence of a hydrophobic enzyme akin to a membrane-bound beta-lactamase of gram-positive bacteria. The location of the gene coding for this beta-lactamase is not yet known.

Nine patients with lower respiratory tract infections were used to study in detail the effect of ampicillin or erythromycin on the colonization patterns of Haemophilus influenzae and Haemophilus parainfluenzae in sputum and saliva. H. influenzae was isolated from purulent sputum of eight patients before the start of treatment. Ampicillin was more effective than erythromycin at clearing H. influenzae from sputum and in decreasing purulence. By careful characterization of multiple strains, the changes in biotype distribution and antibiotic susceptibility patterns were shown. Five biotypes of H. influenzae were associated with chest infection, with type II predominating. Mixed biotype infections occurred in five patients. Most saliva contained multiple biotypes of H. parainfluenzae. Neither antibiotic selected resistant haemophili in saliva or sputum. After treatment with ampicillin, the mucoid sputum was colonized with ampicillin-susceptible H. parainfluenzae biotypes previously found in saliva. We postulate that as inflammation decreases at the bronchial mucosa, the ampicillin concentration drops, allowing ampicillin-susceptible oral H. parainfluenzae isolates to seed the residual mucoid sputum.

<it>Objectives</it>: To investigate the variability in antimicrobial susceptibility of <it>Pseudomonas aeruginosa</it> from sputa of patients with cystic fibrosis, to compare testing individual colonies of the same morphotype either separately or combined and to study the reproducibility of testing antimicrobial susceptibility within and between laboratories. <it>Methods</it>: One hundred and one sputa were cultured. Four colonies of each <it>P. aeruginosa</it> morphotype were suspended. Susceptibility to 12 agents by disc diffusion was tested individually or by pooling the four suspensions. A sputum sample containing four morphotypes of one genotype of <it>P. aeruginosa</it> was used to study reproducibility. Susceptibility was tested in duplicate by eight biomedical scientists in one laboratory and by routine procedures in seven different laboratories. <it>Results</it>: There was a mean of four morphotypes of <it>P. aeruginosa</it> per sputum and three antibiograms per morphotype. In some cases, all four colonies of a single morphotype had different antibiograms. The susceptibility profiles of single isolates of <it>P. aeruginosa</it> correlated poorly with pooled cultures, with the pooled tests missing resistance. Results from one sample tested in duplicate by eight biomedical scientists in one laboratory and in seven other laboratories did not correlate well. The wide range of zone sizes in disc diffusion tests illustrated the variation in susceptibility of 48 colonies from one sputum sample. <it>Conclusions</it>: The role of conventional antimicrobial susceptibility testing is questionable once <it>P. aeruginosa</it> chronically infects the cystic fibrosis lung. A range of susceptibility patterns is seen, even within a morphotype. Routine test results are not reproducible and underestimate resistance.

The BSAC Guidelines on Endocarditis were last published in 1998. The Guidelines presented here have been updated and extended to reflect changes in both the antibiotic resistance characteristics of causative organisms and the availability of new antibiotics. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking, and therefore a consensus approach has again been adopted. The Guidelines cover diagnosis and laboratory testing, suitable antibiotic regimens and causative organisms. Special emphasis is placed on common causes of endocarditis, such as streptococci and staphylococci, however, other bacterial causes (such as enterococci, HACEK organisms, <it>Coxiella</it> and <it>Bartonella</it>) and fungi are considered. The special circumstances of prosthetic endocarditis are discussed.