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Several classes of antibiotics were assessed for activity against non-growing Escherichia coli and cells grown as a biofilm. Antibiotics which had activity against non-growing cells also showed some activity against biofilms. Cephamycins were more active than other cephalosporins, but the most effective antibiotics were imipenem and ciprofloxacin, which were also active against steady state biofilms. However, none of the antibiotics studied was capable of completely eradicating a biofilm. These results suggest that growth rate plays a role in mediating resistance of biofilms to antibiotics.

A standardized agar dilution susceptibility testing method was developed for Campylobacter that consisted of testing on Mueller-Hinton medium supplemented with 5% defibrinated sheep blood in an atmosphere of 10% CO2, 5% O2, and 85% N2. Campylobacter jejuni ATCC 33560 was identified as a quality-control (QC) strain. Minimal inhibitory concentration (MIC) QC ranges were determined for two incubation time/temperature combinations: 36 degrees C for 48 hr and 42 degrees C for 24 hr. Quality-control ranges were determined for ciprofloxacin, doxycycline, erythromycin, gentamicin, and meropenem. For all antimicrobial agents tested at both temperatures, 95-100% of the QC MIC results fell within recommended QC ranges. Twenty-one Campylobacter clinical isolates, encompassing five species of Campylobacter (C. jejuni, C. coli, C. jejuni, subsp. doylei, C. fetus, and C. lari) were tested in conjunction with the C. jejuni QC strain. While C. jejuni and C. coli could be reliably tested under both test conditions, growth of C. jejuni subsp. doylei, C. fetus, and C. lari isolates was inconsistent when incubated at 42 degrees C. Therefore, it is recommended that these species only be tested at 36 degrees C.

We characterized baseline and repopulating stool isolates recovered during a phase II trial of ramoplanin for the treatment of patients with stool carriage of vancomycin-resistant enterococci (VRE). Repopulation with a strain with a related genotype was found in 74, 60, and 53% of individuals in groups treated with placebo, 100 mg of ramoplanin, and 400 mg of ramoplanin, respectively. All ramoplanin-treated patients with a culture positive for VRE at day 7 had a relapse caused by a genotypically related isolate. In ramoplanin-treated patients, antibiotics with activities against anaerobic organisms were associated with positive cultures on day 7 (relative risk [RR] = 8.8; P = 0.004), and the avoidance of such antibiotics was significantly associated with culture negativity through day 21 (RR = 0.16; P = 0.02).

beta-Lactam antibiotics containing a catechol moiety show potent activity against Gram-negative bacteria, particularly organisms grown under iron-limited conditions, suggesting that the iron-regulated outer membrane proteins (IROMPs) play a role in antibiotic uptake. A catecholic C(7) alpha-formamido-substituted cephalosporin showed increased penetration into Escherichia coli cells grown in an iron-deficient medium compared with cells grown in a medium supplemented with iron. In contrast, penetration of the corresponding monohydroxyphenyl analogue was not influenced by iron concentration. Susceptibility studies with mutants of E. coli lacking one or more IROMPs suggested that the catecholic analogue was able to utilize the Fiu (83 kDa) and Cir (74 kDa) proteins, but not the enterobactin receptor FepA (81 kDa). Mutants lacking both Fiu and Cir showed a specific decreased susceptibility for catechol-containing cephalosporins. Radio-ligand binding studies with a Fe-catecholic cephalosporin confirmed an association with these proteins.

SUMMARY: The effect of various lectins and sugars on adhesion of five strains of Candida albicans to buccal and vaginal epithelial cells in vitro was investigated. Adhesion of C. albicans GDH 2346 was inhibited primarily by l-fucose and winged-pea lectin, whereas adhesion of strain GDH 2023 was inhibited by N-acetyl-d-glucosamine, or d-glucosamine, and wheat-germ agglutinin. Three other strains of C. albicans (MRL 3153, GRI 681 and GRI 682) gave results similar to those obtained with strain GDH 2346. Extracellular polymeric material (EP) isolated from strain GDH 2346 inhibited adhesion of strains MRL 3153, GRI 681 and GRI 682 by more than 50%, but that of strain GDH 2023 by only 30%. EP from strain GDH 2023 had little or no effect on the adhesion of any other yeast strain. Lectin-like proteins with affinities for l-fucose, N-acetyl-d-glucosamine and d-mannose were detected in EP from all five strains in different amounts. These results indicate that there are at least two types of adhesion mechanism and that glycosides containing l-fucose or N-acetyl-d-glucosamine can function as epithelial cell receptors for C. albicans.

Candida albicans produces extracellular polymeric material (EP) which contains a mannoprotein adhesin. EP isolated from culture supernatants of C. albicans GDH 2346 consisted of a mixture of glycoprotein components and inhibited yeast adhesion to buccal epithelial cells by up to 60%. Partial purification of the adhesin was achieved by a two-step procedure involving chromatography of EP on concanavalin A-Sepharose and DEAE-cellulose. The purified adhesin inhibited adhesion to buccal cells 30 times more efficiently (on a weight basis) than unfractionated EP. Pretreatment of EP with heat, dithiothreitol or proteolytic enzymes either partially or completely destroyed its ability to inhibit adhesion, whereas pretreatment with sodium periodate or alpha-mannosidase had little or no effect. These results suggest that the protein portion of the mannoprotein adhesin is more important than the carbohydrate moiety in mediating yeast attachment to buccal epithelial cells.