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Hospital acquired infections are a common cause of increased these stays, health care costs and mortality. Currently, the Enterococcus is one of the most common microorganisms involved in these infections. Often these infections are difficult to treat because of the multiple resistances of these microorganisms to conventional antibiotics. The literature on infections caused by this microorganism is limited. This problem is more pronounced when it comes to know the characteristics of infections in specific locations, as is the case of blood bacterial infections.

It is widely known that Enterococcus faecalis have an increased susceptibility to ampicillin, an antibiotic, compared to E. faecium. Because the difference in antimicrobial susceptibility among different species of the genus Enterococcus can have an impact on clinical practice, it was performed a comparative study of clinical and microbiological characteristics and prognosis of patients with blood infections due to E. faecalis against E. faecium and it is unknown whether these features are consistent with those reported in the literature.

A similar study focused on cancer patients with blood infection of vancomycin-susceptible enterococci, another antibiotic, was also carried out. To our knowledge, this is the first study evaluating this population with enterococcal blood infection susceptible to vancomycin, the most prevalent susceptible pattern in Spain and Europe. Previous knowledge of these factors can be employed as a warning mechanism for suspected bacterial blood infection in order to initiate early appropriate empiric therapy. Appropriate empirical treatment is directly related to increased survival in these infections.

It was performed a retrospective observational study at the Hospital del Mar between 1 January 2000 and December 31, 2006. We included all episodes of bacterial blood infections with E.faecalis or E.faecium isolation in blood culture. It was collected demographic, clinical and biochemical data at admission date and the date of positive blood culture for Enterococcus, history of previous admissions, hospital ward (medical, surgical, ICU), other possible risk factors, underlying diseases, previous antibiotic treatment, microbiological characteristics, and mortality.

It was assessed a total of 228 episodes of bacterial blood infections, 168 corresponding to E.faecalis and 60 to E.faecium. All isolates of E.faecalis were susceptible to ampicillin and only 25% was in the group E.faecium. There was one anecdotal isolated of E.faecium resistant to vancomycin. The independent factors associated with the acquisition of bacterial blood infections of E.faecium when compared to those produced by E.faecalis were the surgical ward admission, more than five days of previous treatment with cephalosporin or with carbapenem, prior administration of penicillin and liver disease at baseline and greater severity of the patient on admission.

In the case of cancer patients, we analyzed a total of 73 patients: 54 caused by E.faecalis and 19 caused by E.faecium. In the univariate analysis, comorbidity of diabetes mellitus and prior exposure to penicillins were distinctive factors in the group of E.faecium. The independent factors associated with the isolation of E.faecium were previous exposure to penicillin and greater severity of the patient on admission.

The results of both studies are of upmost importance to decide empirical antibiotic treatment in patients admitted to our hospital. In addition, these conclusions led to the modification of current protocols for empirical treatment of patients with hospital acquired infections in our hospital.