4 Infectious Diseases in Obstetrics and Gynecology Table 3: Antibiotic MICs (µg/mL) in LAPTg broth for vaginal Lactobacillus strains. STR: streptomycin, KAN: kanamycin, NOR: norﬂoxacin, NOV: novobiocin, CHL: chloranphenicol, VAN: vancomycin y MTZ: metronidazole. The assays were performed by triplicate. Table 4: Antibiotic MIC (µg/mL) in LAPTg agar for vaginal Lactobacillus strains. CRO: ceftriaxone, CTX: cefotaxime, CAZ: ceftazidime, CIP: ciproﬂoxacin, IPM: imipenem, CLR: clarithromycin, TET: tetracycline, OXA: oxacillin, NIT: nitrofurantoin, ERY: erythromycin, CLI: clindamycin, AMP: ampicillin, ATM: aztreonam, RIF: rifampin. The assays were performed by triplicate. STR 50 50 50 50 50 100 CRO 100 > 100 100 > 100 > 100 100 OXA > 100 1 10 100 > 100 10 KAN 100 500 500 250 250 250 CTX 100 > 100 100 > 100 > 100 1 NIT 1 1 10 > 100 > 100 10 NOR > 1000 > 1000 500 1000 750 250 CAZ 100 > 100 100 > 100 > 100 100 ERY 100 1 1 100 > 100 10 MIC (µg/mL) NOV 10 10 10 < 1 < 1 < 1 CHL 250 250 250 250 250 250 MIC (µg/mL) CIP > 100 > 100 100 > 100 > 100 10 MIC (µg/mL) CLI 10 1 0.1 > 100 > 100 0.1 IPM 1 > 100 10 > 100 > 100 10 AMP 1 > 100 1 > 100 10 1 Lactobacillus strain L acidophilus CRL 1266 L gasseri CRL 1259 L acidophilus CRL 1251 L paracasei CRL 1289 L johnsonii CRL 1294 L salivarius CRL 1328 Lactobacillus strain L acidophilus CRL 1266 L gasseri CRL 1259 L acidophilus CRL 1251 L paracasei CRL 1289 L johnsonii CRL 1294 L salivarius CRL 1328 Lactobacillus strain L acidophilus CRL 1266 L gasseri CRL 1259 L acidophilus CRL 1251 L paracasei CRL 1289 L johnsonii CRL 1294 L salivarius CRL 1328 they have been considered as “GRAS” for the FDA (Food and Drug Administration, USA) [24]. The available standard techniques and the guidelines for the disc diﬀusion method have been provided by the NCCLS only for selected aero- bic and anaerobic bacteria or yeasts related with laboratory clinical diagnostic. However, many researchers have devel- oped modiﬁcations of the semiquantitative disc assay for lac- tobacilli [19, 25–28]. Diﬀerent base media and type strains have been employed but reference data are still not avail- able. The E-test (AB Biodisk) has also been used and rec- ommended as an easy diﬀusion test but modiﬁcations of the original protocol had to be introduced for lactobacilli [23, 29]. In the present paper, the conventional methodology de- scribed by Bauer et al [18] was ﬁrst applied. Mu¨ller Hinton base medium was employed to test the eﬀect of the antibi- otics routinely used for the treatment of urinary tract infec- tions (UTIs) on Lactobacillus strains. As previously described by other researchers [30], the growth of lactobacilli in Mu¨ller Hinton was poor and irregular, and it was not possible to measure the diameter of the inhibition halos. When LAPTg was employed instead of Mu¨ller Hinton, the growth was op- timum while in MRS it was appropriate only for some Lac- tobacillus strains but not for all of them. The last observation is coherent with the composition of these two media. LAPTg has a wider variety of nutrients and allows the growth of lac- tobacilli under aerobic or microaerophilic conditions, while MRS as well as LBS [31] seems to be more appropriate for microaerophilic or anaerobic growth (data not shown). According to our results, the growth of vaginal lacto- bacilli in LAPTg and MRS agars was homogeneous and the inhibition halos were clearly deﬁned (except for L gasseri CRL1259 and L johnsonii CRL1294 which were not able to grow in MRS under microaerophilic incubation). Charteris et al [23, 32] have also used MRS for the disc diﬀusion and the E-test under anaerobic incubation conditions in both cases. Based on size of the halos, the mentioned authors have classiﬁed the microorganisms into susceptible, moderate sus- ceptible, and resistant. However, the reasons by which they consider the published ranges for the susceptibility category are not explained. Considering that the size of the halos de- pends on the diﬀusion media [33], reference data obtained in the same media are supposed to be employed for cat- egorization purposes. Other examples of the use of diﬀer- ent base media are the publications of Bayer et al [25] that have used Mu¨ller Hinton supplemented with yeast extract and L-cysteine (0.2% and 0.05%, resp), Felten et al [26] who have employed Mu¨ller Hinton with 5% of sheep blood, and VAN 10 < 1 < 1 < 1 < 1 > 1000 CLR 1 > 100 10 > 100 100 1 ATM 100 100 > 100 100 > 100 > 100 MTZ > 1000 > 1000 > 1000 > 1000 > 1000 > 1000 TET 100 > 100 10 > 100 100 1 RIF > 100 0.1 0.1 > 100 > 100 0.1