Finally, two strains from women with mastitis (CJ11 and DG2S) were resistant to streptomycin (> 1000 μg mL-1) and one strain (AQLI2) from the same group was resistant to vancomycin (16 μg mL-1). No strains resistant to these two antibiotics were found among the strains from healthy women. Table 2 Distribution of MIC’s to several antibiotics amongS. epidermidisisolated from mastitis and healthy women       Percentage of strains for which the MIC (μg mL-1) was as follows: Antibiotics Breast milk N° of strains ≤ 0.03 0.12 0.25 0.5 1 2 4

8 > 8   PEN H 36 17 8   8 14 14 8 11 19     M 40 10 5 5 8 10 33 8 8 18   AMP       ≤ 0.12 0.25 0.5 1 2 4 8 100 > 100   H 36   19 6 17 22 8 8 6 14     M 40 Doxorubicin research buy   15 8 5 23 20 10 5 13 3 OXA         ≤ 0.25 0.5 1 2 > 2         H 36     11 31 11 8 39         M 40     5 8 13 8 68       CIP         ≤ 0.25 0.5 1 2 > 2         H 36     47 39 8   6         M 40     30 38 18 3 13       CHL                   ≤ 8 16 > 16   H 36               75 17 8   M 40               78 10 13 ERY         ≤ 0.25 0.5 1 2 4 > 4       H 36     39 14 6 8   33       M

40     23 15     3 60     CLI           ≤ 0.5 1 2 > 2         H 36       81 8 3 8         M 40       70 3   28       TET                 ≤ 4 8 > 8     H 36             56 19 25     M 40             68 8 25   VAN           ≤ 0.5 1 2 4 8 16 ≥ 16   H 36         44 50 6         M 40         43 48 5 3 3   MUP                 ≤ 4 256 > 256     H 36             78 11 11     M 40             58 13 30   H: strains

isolated from healthy women; M: strains isolated from mastitis-suffering women; PEN: penicillin; AMP: ampicillin; OXA: oxacillin; CIP: Pirfenidone ic50 ciprofloxacin; new CHL: chloramphenicol; ERY: erythromycin; CLI: clindamycin; TET: tetracycline; VAN: vancomycin; MUP: mupirocin. Statistically-significant differences between isolates from mastitis and healthy women are in bold. Presence ofmecAand SCCmectyping Among the 41 strains showing oxacillin resistance, themecA gene could be detected by PCR in 37 (25 from mastitic milk and 12 from milk of healthy women). No amplification was observed in two strains of each group (F12 and CJ9; LI5081 and LC047, respectively), which had shown an oxacillin MIC value of > 2 μg mL-1. In contrast, themecA gene was detected in five oxacillin susceptible strains, one from a mastitis case (YLIC13) and four from healthy women (LO5RB1, LX5RB3, LV221 and LCC5082). The type of SCCmecwas determined in all themecA+strains. TheccrB gene could be amplified from 22 of the 26mecA+strains from the mastitis group and, on the basis of theccrB restriction pattern withHinfI (type IV: 264, 227 and 154 bp; type III: 537 and 106 bp) or withHinfI/BsmI (type IV: 227, 171, 153 and 93 bp; type III: 320, 174, 106 and 44 bp), 19 strains were assigned to type IV and the remaining three (S1LDC12, Z2LDC17 and DF2LAB) to type III (see additional file 1).