European Committee on Antimicrobial Susceptibility Testing (EUCAST) Technical Notes on antimicrobial susceptibility testing

The main objectives of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) are to harmonise breakpoints for antimicrobial agents in Europe, and to act as the breakpoint committee for the European Medicines Agency (EMEA) during the registration of new antimicrobial agents. Detailed EUCAST procedures for harmonising and setting breakpoints for antimicrobial agents are available on the EUCAST website. Beginning with the current issue, a series of EUCAST Technical Notes will be published in CMI, based on the rationale documents produced by EUCAST for each of the antimicrobial agents studied, with the aim of highlighting important background information underlying decisions on breakpoints made by EUCAST.     

Concomitant mitral valve surgery with aortic valve replacement: a 21-year experience with a single mechanical prosthesis

Background  

Long-term survival for combined aortic and mitral valve replacement appears to be determined by the mitral valve prosthesis from our previous studies. This 21-year retrospective study assess long-term outcome and durability of aortic valve replacement (AVR) with either concomitant mitral valve replacement (MVR) or mitral valve repair (MVrep). We consider only a single mechanical prosthesis.     

Microbiologically proven bacterial infections in AIDS.

We have reviewed the incidence, type and site of microbiologically proven bacterial infection occurring in 52 patients with the acquired immunodeficiency syndrome (AIDS) who presented to Southmead Hospital, Bristol between 1990 and 1994. A total of 30 (58%) patients had significant bacterial isolates. The majority of infections were community acquired. Overall, more infections were caused by Gram-negative organisms but Gram-positive organisms predominated in bacteraemia. Mycobacterium avium intracellulare (MAI) caused infection in the largest number of patients, followed by Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas sp, and Campylobacter sp. When individual episodes of infection were considered, after MAI, Haemophilus influenzae, Streptococcus pneumoniae and Pseudomonas sp were the organisms most frequently isolated; often these same organisms caused recurrent chest infection. Bacterial infections in AIDS patients are common and although they generally respond well to antimicrobial chemotherapy there is a high recurrence rate, particularly in the respiratory tract, which is the commonest site of infection.     

Streptococcus milleri and second trimester abortion.

Review of 214 fetal necropsies performed in the department of pathology, University of Aberdeen, showed 40 cases of chorioamnionitis or intrauterine pneumonia, five of which were associated with Streptococcus milleri. In two cases there was good evidence to implicate S milleri as the cause of infected abortion while in the other cases its pathogenic role was less clear.     

Evaluation of API 20 STREP system for identifying Listeria species.

The API 20 STREP system was used to identify 146 known strains from seven species of the genus Listeria, including both pathogenic and environmental strains. The gallery was easy to use and tests, with the exception of leucine arylamidase (LAP) and starch fermentation (AMD), were simple to interpret. Identification to genus level was satisfactory but differentiation between species was poor. Using the API 20 STREP the haemolytic species L monocytogenes, seeligeri, and ivanovii could easily be differentiated from the non-haemolytic species L welshimeri, innocua, grayii and murrayi. Of the haemolytic species, L monocytogenes could not be distinguished from L seeligeri but L ivanovii could be separated from the two other haemolytic species because it fermented ribose. Non-haemolytic L welshimeri could not be differentiated from non-haemolytic L innocua, but mannitol and ribose fermenting non-haemolytic L grayi and L murrayi were easily differentiated from the other two non-haemolytic species. The API 20 STREP identified Listeria in four hours and therefore might be used for rapid identification of strains causing infection in man. It would, however, not be useful to identify environmental isolates when speciation is important.     

Do blood cultures need continuous monitoring so that clinical action can be taken outside normal working hours?

Many automated blood culture reading systems monitor bacterial growth 24 hours a day but it is unclear if reacting to prompts indicating bacterial growth outside normal laboratory hours is of clinical benefit. An analysis of 50 blood cultures from 43 patients which had organisms seen on Gram films and had triggered positive out-of-hours showed that examination of the Gram film altered management of seven patients and the results of culture or sensitivity testing altered that of a further four. However, after review, it was felt the clinical outcome would not have been influenced by earlier intervention in any of these patients. We therefore consider that an out-of-hours service for dealing with positive blood cultures is not justified in our hospital. This conclusion may not apply universally, especially in hospitals where potential pathogens show less predictable antimicrobial sensitivity patterns.     

An audit of the use of manual handling equipment and their microbiological flora--implications for infection control

A review of the use of manual handling aids in two hospitals found equipment was employed on a multi-patient basis with inadequate cleaning. Sampling with a Casella slit sampler demonstrated frequent contamination by methicillin-resistant Staphylococcus aureus and Clostridium difficile of fabric aids. Recommendations for care of equipment are made.