The clumping factor test and some commercial systems may misidentify S. lugdunensis. Oxacillin resistance detected by commercial systems is not indicative of the presence of the mecA gene. These facts, together with beta-lactamase production, may preclude adequate treatment of infections by this virulent coagulase-negative Staphylococcus.

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Biofilm production was assessed in 52 Staphylococcus epidermidis isolates from the catheters of 52 patients with catheter-related bloodstream infections (CR-BSI) and compared with 14 isolates from the skin of healthy volunteers by spectrophotometry. The isolates were classified as non- (G1), weak- (G2) or strong- (G3) slime producers based on optical density, and as producers and non-producers based on the results of the Congo red agar test. Differences (p = 0.012) in the proportion of G1, G2 and G3 among the isolates were found between catheter and healthy skin strains: there was a higher percentage of G1 types among the healthy skin strains (35.7 vs. 11.5%; p = 0.046) and a higher percentage of G3 types among the catheter isolates (44.2 vs. 0%; p = 0.001). No significant differences were found with the Congo red agar test. G3 is a phenotypic marker for CR-BSI.

In vitro tigecycline subinhibitory concentrations were able to interfere with biofilm formation by E. faecalis.

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Interference of cefditoren (CDN) and amoxicillin/clavulanic acid (AMC) with biofilm production was studied using 11 Streptococcus pneumoniae isolates with minimum inhibitory concentrations (MICs) ranging from 0.015 g/mL to 0.5 g/mL for CDN and from 0.06 g/mL to 2 g/mL for AMC (except for one isolate with an AMC MIC of 8 g/mL) and 5 Haemophilus influenzae isolates with MICs of 0.03-0.06 g/mL for CDN and 0.5-16 g/mL for AMC. Slime production was assessed in antibiotic-free medium and with 0.03 g/mL CDN or 1/0.5 g/mL AMC by pneumoniae versus H. influenzae for each antibiotic, no differences were found for AMC (15.92% vs. 9.40%; P = 0.36), with a tendency for CDN (24.02% vs. 13.79%; P = 0.069). Different -lactams may have different capabilities of interfering with S. pneumoniae biofilm development when tested under the same experimental conditions.

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