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J Food Prot. 2000 Oct;63(10):1421-5.
Detection, quantitation, and identification of residual aminopenicillins by high-performance liquid chromatography after fluorescamine derivation.

Hong C, Kondo F.

Department of Veterinary Public Health, Faculty of Agriculture, Miyazaki University, Gakuen, Japan.

A high-performance liquid chromatographic (HPLC) method with fluorescence detection after precolumn fluorescamine derivation was developed to detect residues of two aminopenicillins, amoxicillin (AMPC) and ampicillin (ABPC), in bovine serum. Proteins in serum samples spiked with each of these penicillins were precipitated with sodium tungstate and sulfuric acid, centrifuged, and removed by passage through a C18 solid-phase extraction cartridge. After precolumn treatment of the extraction products of AMPC and ABPC with fluorescamine solution, HPLC analysis with fluorescence spectrophotometric detection at an excitation wavelength of 390 nm and an emission wavelength of 485 nm was performed to identify these products. Two mobile phases were used for residual analysis by the isocratic HPLC system. An ODP column (polyvinyl alcohol bonded with an octadecyl functional group) that can be used with strongly alkaline mobile phases (pH 2.0 to 13) was selected, and the column temperature was set at 40 degrees C. A mobile phase comprising 100-mM K2HPO4 solution and acetonitrile (72:28, vol/vol), which yielded AMPC and ABPC retention times of 4.1 and 7.9 min, respectively, was suitable for detection of residual ABPC but not for residual AMPC because interference was caused by peaks of other extracted substances. When a mobile phase comprising a different ratio of 100-mM K2HPO4 solution and acetonitrile (78:22, vol/vol) was used, the retention times of AMPC and ABPC were 7.3 and 26.3 min, respectively, and both penicillins could be analyzed using this system. The calculated standard curves of the reaction products with both mobile phases were linear, and the correlation coefficients were greater than 0.999. The lower limit of detection was 10 ng/ml for both penicillins. Analysis of extracts from bovine serum spiked with AMPC and ABPC at a concentration of 1 microg/ml yielded recovery rates of 102.2 +/- 5.5% and 79.0 +/- 5.2%, respectively. This detection method may be useful for routine laboratory testing of AMPC and ABPC.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11041144&dopt=Abstract




New Microbiol. 2000 Oct;23(4):347-56.
Virulence profiles and other biological characters in water isolated Aeromonas hydrophila.

Bondi M, Messi P, Guerrieri E, Bitonte F.

Dipartment of Biomedical Sciences, University of Modena and Reggio E., Italy.

Thirty water isolates of A. hydrophila were tested for potential virulence profiles, antibiotic resistance and Bacteriocin-Like Substances (BLS) production. Cytotoxic activity was present in all strains tested, 87% were hemolytic and 70% adhesive. Lysine decarboxylase reactions (LDC) positivity was correlated with virulence factors: 100% versus cytotoxicity, 84% versus adherence, 76% versus hemolytic activity. The correlation was also present in the LDC-negative strains. Hemolytic and cytotoxic activities were frequently associated: high cytotoxicity, corresponding to high hemolytic activity and vice versa. The in vitro susceptibility of A. hydrophila to 28 antibacterial agents showed that cefotaxime was the most active beta-lactam antibiotic, and Cefuroxime inhibited 90% of the strains. Isolates were resistant to Penicillin G, Ampicillin, Carbenicillin, Amoxicillin, Cephalotin and Cefaclor. Tetracycline, Chloramphenicol, Nitrofurantoine, the quinolones and the aminoglycosides (except Streptomycin) were consistently active. BLS production never emerged against closely-related microorganisms. On the contrary A. hydrophila presented a heteroinhibitory activity against non-taxonomically related genera such as Listeria spp. (L. seeligeri NCTC 11856, L. welshimeri NCTC 11857, L. ivanovii NCTC 11846) and S. aureus ATCC 25923. Although a large number of strains showed virulence determinants together with other biological characters such as antibiotic resistance and BLS production, it was not possible to relate these factors to the observed plasmids.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11061623&dopt=Abstract




Diagn Microbiol Infect Dis. 2000 Nov;38(3):189-91.
Antimicrobial susceptibility of Abiotrophia adiacens and Abiotrophia defectiva.

Tuohy MJ, Procop GW, Washington JA.

Section of Clinical Microbiology/L40, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195-5140, USA.

The susceptibilities of 27 Abiotrophia adiacens (proposed reclassification Granulicatella adiacens comb.nov., Collins & Lawson, 2000) and 12 Abiotrophia defectiva isolates were tested by microdilution in pyridoxal hydrochloride and lysed horse blood supplemented Mueller-Hinton broth. According to NCCLS interpretative criteria for Streptococcus spp. not Streptococcus pneumoniae, the susceptibilities of A. adiacens and A. defectiva were, respectively: penicillin, 55% and 8%; amoxicillin, 81% and 92%; ceftriaxone, 63% and 83%; meropenem, 96% and 100%; and 100% for both species with clindamycin, rifampin, levofloxacin, ofloxacin, quinupristin/dalfopristin, and vancomycin.

online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11109021&dopt=Abstract













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