The in-vitro susceptibilities of vaginal lactobacilli to four broad-spectrum antibiotics, as determined by the agar dilution and E test methods

Abstract

The minimum inhibitory concentrations (MICs) of cefaclor, co-amoxiclav, clarithromycin and ciprofloxacin for 59 strains of vaginal lactobacilli were determined by both the reference agar dilution and E test methods. With the exception of clarithromycin, there was poor correlation between the results obtained by the two techniques. This was most apparent for the beta-lactams studied, the MICs of cefaclor as determined by the E test being particularly difficult to define. The stability of antimicrobial gradients in the E test may cause problems when testing slow-growing bacteria and/or organisms which grow only under anaerobic conditions. Accordingly, only those MICs determined by the agar dilution method are reported. The percentages of susceptible isolates were as follows: clarithromycin, 100; co-amoxiclav, 100; cefaclor, 20; and ciprofloxacin, 4. The administration of antimicrobials, such as ciprofloxacin and cefaclor, which have poor activities in vitro against lactobacilli, may therefore be advantageous to the host because it allows the protective effects of the normal vaginal flora to be preserved.

Relationship between lactobacilli and opportunistic bacterial pathogens associated with vaginitis

“…The low percentage of Lactobacilli resistance to amoxicillin in the present study was agreed with the result obtained by Herra et al . [37] who found that Lactobacilli resistance to amoxicillin was at low percentage and the Lactobacilli were mildly resistant to amoxicillin.…”

Comparison of Broth Microdilution, Etest, and Agar Disk Diffusion Methods for Antimicrobial Susceptibility Testing of Lactobacillus acidophilus Group Members

“…They concluded that this phenomenon may be explained by the high spontaneous frequency of mutation to antibiotic resistance (6), which is not uncommon in lactobacilli (3). Additionally, the loss of antibacterial activity of unstable antimicrobial agents during incubation may result in subinhibitory concentrations that could promote the emergence of resistant strains during prolonged exposure (9). This assumption is supported by the detection of erythromycin-and clindamycin-resistant colonies after 48 h but never after 24 h of incubation within the present study.…”

Evaluation of New Broth Media for Microdilution Antibiotic Susceptibility Testing of Lactobacilli, Pediococci, Lactococci, and Bifidobacteria

“…A mixed formulation of Iso-Sensitest broth (90%) and deMan-Rogosa-Sharpe broth (10%) with or without supplementation with L-cysteine, referred to as the LAB susceptibility test medium, provided the most optimal medium basis in terms of growth support of nonenterococcal LAB and correct indication of MICs of international control strains.A large variety of methods to determine antibiotic susceptibilities of nonenterococcal lactic acid bacteria (LAB) belonging to the genera Lactobacillus, Pediococcus, Lactococcus, and Bifidobacterium based on either agar disk diffusion (4, 5, 15, 20, 26, 29, 32, 33, 35), E-test (6, 9, 10, 13, 15, 16, 19, 21), agar dilution (3,7,11,17,19,22) or broth dilution (1,12,14,18,23,24,25,27,29,30,31, 34) has been described. Due to the fact that many of these organisms require special growth conditions in terms of medium acidity and nutrient supplementation, conventional media such as Mueller-Hinton and Iso-Sensitest (IST) agar or broth are not uniformly suitable for susceptibility testing of nonenterococcal LAB.…”

“…A large variety of methods to determine antibiotic susceptibilities of nonenterococcal lactic acid bacteria (LAB) belonging to the genera Lactobacillus, Pediococcus, Lactococcus, and Bifidobacterium based on either agar disk diffusion (4,5,15,20,26,29,32,33,35), E-test (6,9,10,13,15,16,19,21), agar dilution (3,7,11,17,19,22) or broth dilution (1,12,14,18,23,24,25,27,29,30,31,34) has been described. Due to the fact that many of these organisms require special growth conditions in terms of medium acidity and nutrient supplementation, conventional media such as Mueller-Hinton and Iso-Sensitest (IST) agar or broth are not uniformly suitable for susceptibility testing of nonenterococcal LAB.…”