Laboratory-prepared (conventional) and commercial susceptibility testing systems were compared by using a group of methicillin-resistant (MR) and methicillin-susceptible (MS) strains of Staphylococcus aureus. A group of 25 MR and 15 MS S. aureus strains were coded and tested blindly by disk diffusion, agar dilution, broth microdilution, Sensititre, Micro-Media, Sceptor, API 3600S, MicroScan, Autobac I, and MS-2 systems. All systems were incubated at 35°C and read with either a manual or automated reader at the recommended times. Where applicable, systems were also read at 48 h. Among the conventional assays, the broth and agar dilution methods were comparable, both detecting 88% of the MR strains at 24 h and detecting 92 and 96%, respectively, at 48 h. The disk diffusion method was less efficient, detecting only 36 and 72% at 24 and 48 h, respectively. Detection of cephalothin resistance was low for all systems at both time periods, with agar dilution and disk diffusion being the most and least efficient, respectively. Some variability was also seen with detection of resistance to clindamycin and gentamicin. Among the MS strains, variability among the conventional systems occurred with methicillin, gentamicin, ampicillin, and penicillin. Comparison of the commercial systems with manual readers with the broth microdilution method (reference method) showed that for MR strains, the Sceptor system gave identical results at 24 and 48 h. Sensititre detected 68 and 88% of the MR strains, whereas Micro-Media was least effective detecting 12 and 80% at 24 and 48 h, respectively. None of the commercial systems detected cephalothin resistance well, with only one strain being indicated by the Sceptor and Sensititre systems at 48 h. Slight differences were also seen among the systems with clindamycin and gentamicin. With regard to the MS strains, variability among the systems was seen with methicillin, penicillin, ampicillin, clindamycin, and gentamicin. Among commercial systems with automated readers, the API system detected a greater number of MR strains than did the reference method at 24 and 48 h, 96 and 100%, respectively. The MicroScan method was comparable to the reference method detecting 80 and 88% of the MR strains at both time periods, respectively. Both Autobac I and MS-2 were much less effective in detecting MR strains, noting only 32 and 16%, respectively, at the 3-to 6-h readings. Poor detection of cephalothin resistance among MR strains was evident in all systems. Variability also occurred among the systems with clindamycin, gentamicin, and ampicillin. A single strain of the MR group was reported to be vancomycin resistant by the API system. Among the MS group, the greatest variability was seen with methicillin. Less variability occurred with penicillin, ampicillin, gentamicin, and vancomycin. The introduction of penicillin as antistaphylo-ducing strains. In 1961, only 2 years after the coccal therapy was highly successful until resist-introduction of this compound, Jevons reported ance due to 3-lactamases was...
One hundred clinical isolates of methicillin-resistant (Metr) Staphylococcus aureus from five different geographical origins were tested for their susceptibility to 12 non-li-lactam antibiotics by the broth microdilution technique recommended by the National Committee for Clinical Laboratory Standards.Coumermycin and rifampin showed the highest activity with of MIC90s of 0.032 jig/ml for each compound. No resistance was found to coumermycin, whereas a single Metr S. aureus strain was found to be resistant to rifampin. Ciprofloxacin, vancomycin, and teicoplanin were the next most active compounds with MIC90s of 0.25, 0.5, and 0.5 ,ug/ml, respectively. Norfloxacin was less active, with an MIC90 of 1.0 ,ug/ml. Amikacin was the most active aminoglycoside tested, whereas high levels of resistance were found to tobramycin and gentamicin. Doxycycline and chloramphenicol showed variable results. Geographical variations in results were seen with doxycycline, chloramphenicol, and aminoglycosides. Kill-curve studies showed that coumermycin, ciprofloxacin, teicoplanin, vancomycin, and rifampin were highly bactericidal; more than 90% of the inoculum was killed within 8 h.
The association of Helicobacter pylori with an increased risk of gastric adenocarcinoma has been documented, but its mechanisms have not been elucidated. This study explored these mechanisms by addressing the relationship between H pylori and the silver-staining nucleolar organizer regions (AgNORs) in the gastric antrum. The number of AgNORs per nucleus has been correlated with proliferative rate and ploidy. The results of gastric biopsies performed before and after treatment for H pylori showed that only patients who cleared the H pylori infection had a significant decrease in the number of AgNORs per nucleus. A positive association between AgNOR counts and the severity of polymorphonuclear infiltrate could be demonstrated in patients who did not clear H pylori infection. The authors concluded that H pylori infection alters the replication cycle of the antral mucosa, inducing hyperproliferation and possibly ploidy abnormalities. Whether these alterations are induced directly by the bacterium or by the acute inflammatory infiltrate remains undecided; the data in this study suggest a possible direct effect of the polymorphonuclear leukocytes.
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