Isolation and antimicrobial susceptibility testing of fecal strains of the archaeon Methanobrevibacter smithii.

BACKGROUND: The archaeon Methanobrevibacter smithii is regarded as part of the indigenous microflora of the human intestine but may be connected with pathological conditions. The microbe is extremely oxygen intolerant and is not detectable by anaerobic culture techniques for bacteria. Accordingly, to date quantitative antimicrobial susceptibility data of human isolates are missing. METHODS: The anoxic Hungate technique and a three-step culture procedure using media supplemented with antibiotics were applied to isolate M. smithii from randomly selected human feces. The minimum inhibitory concentrations (MICs) of 15 isolates and the reference strain DSM 861 were determined using a broth macrodilution test resembling the procedure for testing anaerobic bacteria. RESULTS: The 16 strains were highly resistant (MICs >64 mg/l) against penicillin G, cephalothin, vancomycin, streptomycin, gentamicin, ciprofloxacin, and clindamycin. Metronidazole inhibited the strains at MICs between 0.5 and 64 mg/l. CONCLUSIONS: Multiple-antibiotic-resistant Methanoarchaea occur in the human gut. They may be selected during therapy with common antibacterial agents and may be eliminated by the application of metronidazole.

Influence of the cultivation, devitalization and preservation of Staphylococcus aureus ATCC 12598 on the activity of cell-bound protein A.

Different culture conditions, devitalizing treatments, and preservation procedures were tested for the production of protein A-bearing cells of Staphylococcus aureus ATCC 12598. Native cells with the highest IgG-binding activity were obtained after cultivation at 37 degrees C for 24-48 h in enriched media. Devitalization by ethanol, 1-propanol, formaldehyde, glutardialdehyde, chloramine T, and by heat, reduced the protein A activity depending on the duration of treatment. The protein A content of devitalized cells were best preserved by storage at -20 degrees C or by lyophilization. Staphylococcal preparations with a stable IgG-binding activity of 20 mg/g bacteria, which are very suitable for coagglutination tests, were produced by culture in TSB medium, followed by devitalization with 1-propanol and lyophilization.

Differentiation of the major flagellar antigens of Pseudomonas aeruginosa by the slide coagglutination technique.

Antisera against the two major flagellar antigens of Pseudomonas aeruginosa were obtained by immunization of rabbits with isolated flagella and absorption of contaminating antisomatic antibodies. In the conventional slide agglutination test, the pure H antisera did not agglutinate the flagellated cells of the homologous strains. The addition of protein A-bearing staphylococci to H antiserum and homologous flagellated cells, the so-called slide coagglutination, results in a rapid development of flaky clumps. H coagglutination tests of reference strains, which formerly have been H typed by long-term tube agglutination and by the indirect fluorescent-antibody technique, yielded exactly the same subdivision of the strains in H type a and H type b as the more laborious and time-consuming methods. O grouping and H typing of 181 isolates from clinical specimens revealed a free combination of the somatic and flagellar antigens. 25 OH serovars were found. The simple and rapid coagglutination technique can promote the serovar determination of P. aeruginosa, particularly for the purpose of hospital infection control.

Substitution of anti-human globulin by protein A-bearing staphylococci in the detection of Brucella antibodies.

A coagglutination test using protein A-bearing staphylococci has been developed for the detection of Brucella antibodies. Comparing the results of a random sample of 57 sera collected from Malta fever patients, suggestive titers of 1: greater than or equal to 160 were found in 8 sera (14%) with the standard agglutination test, in 22 sera (39%) with the Coombs test, and in 23 sera (40%) with the coagglutination test. The titers in the Coombs test and the coagglutination test coincided in 54 (95%) of the 57 sera, in 3 sera (5%) the difference was no more than one dilution step. Sera from healthy subjects and patients with infections other than brucellosis showed titers up to 1:40 in all three tests. Because of its sensitivity and specificity in detecting non-agglutinating antibodies, the Brucella-antibody coagglutination test may replace the Coombs test as a complementary assay to the standard agglutination. Native sera from Malta fever patients frequently show a prozone phenomenon in the standard agglutination test and a reduced agglutinate formation in both the Coombs test and the coagglutination test. The inhibitors of agglutination lattice formation are apparently serum beta-lipoproteins which become attached to the Brucella antigen and can be removed from the serum by treatment with MnCl2-heparin.