Over the past decade, an increasing number of infections due to Agrobacterium radiobacter have been reported. Observation of three cases of bacteremia due to this organism prompted a review of the English-language literature. Nineteen cases of significant disease have previously been reported. In more than one-half of the cases, bacteremia was the primary manifestation, often associated with the presence of an intravascular catheter. Other clinical syndromes (peritonitis, urinary tract infection, and endocarditis) have been described. Infection is strongly related to the presence of plastic foreign material, and effective treatment often requires removal of the device. Because antimicrobial sensitivity is variable, treatment must be based on sensitivity data for the individual isolate.

Linezolid-resistant coagulase-negative staphylococci have emerged at our institution and are predominately of a single clone. We believe that the most likely scenario to explain this emergence is that person-to-person spread of linezolid-resistant coagulase-negative staphylococci led to establishment of skin colonization with the strain. Subsequent use of linezolid was followed by selection of the linezolid-resistant strain, which then became the dominant skin flora. The potential for a parallel scenario involving clonal dissemination followed by selection of linezolid-resistant methicillin-resistant Staphylococcus aureus is a real possibility.

Cefepime is a potentially useful antibiotic for treatment of infections with Enterobacter cloacae. However, in our institution the MIC 90 for E. cloacae bloodstream isolates is 16 g/ml. PCR amplification of bla genes revealed that one-third (15/45) of E. cloacae bloodstream isolates produced SHV-type extended-spectrum beta-lactamases (ESBLs) in addition to hyperproduction of AmpC-type beta-lactamases. The majority (11/15) of ESBL producers also produced the TEM-1 beta-lactamase. The SHV types included SHV-2, -5, -7, -12, -14, and -30. All but two of the ESBL-producing E. cloacae isolates, but none of the non-ESBL-producing strains, had MICs of cefepime of >2 g/ml. The MIC 90 for cefepime for ESBL-producing strains was 64 g/ml, while for non-ESBL producers it was 0.5 g/ml. Using current Clinical and Laboratory Standards Institute breakpoints for cefepime, two thirds (10/15) of ESBL-producing isolates would have been regarded as susceptible to cefepime. Phenotypic ESBL detection methods were generally unreliable with these E. cloacae isolates. Based on these results, pharmacokinetic, pharmacodynamic, and clinical reevaluation of cefepime breakpoints for E. cloacae may be prudent.