Inexpensive 4-hour micro-agar dilution susceptibility determination method.

Using a micro-agar dilution (MAD) method in which microscope slides are covered with a thin film of agar, and MICs are read microscopically after a 4-h incubation, 18 antibiotics were tested against 29 to 32 microorganisms each. Identical MICs were obtained for microscopic MAD MICs performed in duplicate in 87.1% of the antibiotic-microorganism combinations, and 97.9% were identical within one dilution. When read macroscopically after an 18-h incubation, identical duplicate MICs were obtained in 86.8% of the cases, and 98.4% were identical within one dilution. Using agar dilution as the "gold standard," the correlation obtained with MAD slides read microscopically at 4 h was 94.3%, and macroscopic correlation at 18 h was 97.6%. The correlation of MAD slides with agar dilution for the groups of microorganisms most frequently used was as follows (microscopic/macroscopic): Staphylococcus aureus 96%/98%; Streptococcaceae 97%/98%; Enterobacteriaceae 98%/99%; and Pseudomonadaceae 95%/98%. At the present rate of exchange (fl 1.60 = $1.00f1p4he cost of a MAD slide, including labor, is $1.28 (20 microorganisms tested) or $0.06 per microorganism-antibiotic combination tested. This method is easy to perform, rapid, and inexpensive. It is suitable for use in routine and research laboratories.

Changes in symptoms, peak expiratory flow, and sputum flora during treatment with antibiotics of exacerbations in patients with chronic obstructive pulmonary disease in general practice.

BACKGROUND: Bacterial infections of the lower airways during an exacerbation in patients with asthma or chronic obstructive pulmonary disease (COPD) may be the cause of an exacerbation or the consequence of a viral infection or an increase in airways limitation. To determine whether bacterial infection is an important component in the pathogenesis of an exacerbation, the effects of antimicrobial treatment must be studied. METHODS: Patients with asthma or COPD seen in general practice were studied in a double blind randomised manner to investigate whether the antimicrobial drugs amoxicillin (500 mg three times daily), cotrimoxazole (960 mg twice daily), or a placebo, each when added to a short course of oral corticosteroids, can accelerate recovery from exacerbations. Patients were instructed to contact their own physician early in the morning when complaints of increased shortness of breath, wheezing, or exacerbations of cough with or without sputum production occurred. Treatment effects were evaluated over the next 14 days by studying symptom scores (wheeze, dyspnoea, cough with and without mucus production, and awakening with dyspnoea), peak expiratory flow values (PEF, expressed as % predicted), and sublingual temperature. Bacteriological study of the sputum was made at the onset of an exacerbation and 7, 21 and 35 days afterwards. RESULTS: Of 195 patients enrolled 71 (36%) contacted their physician for symptoms of an exacerbation. Symptoms improved in all three groups, improvements ranging from 0.54 to 0.75 points per day on a four point scale. PEF% predicted showed improvements in the three groups after the exacerbation, ranging from 0.34% to 0.78% predicted per day, finally returning to baseline values. Sublingual temperature did not change. Six of 71 patients consulted their physician because of a relapse between four and 24 days after the start of treatment. In only two of the 50 sputum samples, collected during an exacerbation, and which contained > or = 10(5) bacteria in culture sensitive to the chosen antibiotic given, did any benefit from antimicrobial treatment occur. During the recovery period sputum purulence improved irrespective of antibiotic treatment. CONCLUSIONS: Antibiotics given with a short course of oral prednisolone during an exacerbation do not accelerate recovery as measured by changes in peak flow and symptom scores in ambulatory patients with mild to moderate asthma or COPD when treated by their general practitioners. Moreover, antibiotics do not reduce the number of relapses after treating an exacerbation.

In vitro studies on stability and development of metronidazole resistance in Helicobacter pylori.

Seventy isolates of Helicobacter pylori from antral biopsy samples were tested for their susceptibilities to metronidazole by agar dilution. Seven (10%) of these clinical isolates appeared to be resistant to metronidazole. Sixty-three strains were susceptible. In 42 (67%) of the 63 susceptible isolates, resistant isolates were obtained by serial passage on plates containing subinhibitory concentrations of metronidazole. In 10 of these 42 strains, the acquired resistance appeared to be unstable. The difference between the stability of resistance that occurred after one or two passages and the stability of resistance that occurred after three passages was statistically significant (P < 0.006). Primary resistance in clinical isolates was a stable phenomenon. Whether the resistance that emerges during therapy in patients is stable or unstable needs to be established.

Oropharyngeal flora in asthma and in chronic obstructive pulmonary disease. Indigenous oropharyngeal microorganisms in outpatients with asthma or chronic obstructive pulmonary disease.

In vitro and in vivo studies have shown that various strains of "viridans streptococci" (nongroupable alpha-hemolytic streptococci) inhabiting the oropharynx suppress the growth of gram-positive and gram-negative microorganisms. We conducted an inventory of the oropharyngeal flora from ambulatory asthma and chronic obstructive pulmonary disease (COPD) patients and a control group to examine the interaction between viridans streptococci and potential pathogens in vivo. In addition, the difference in colonization patterns of these bacteria was studied. Oral washings from 195 patients, 48 asthma (24.6%), 147 COPD (75.4%), and 157 control subjects were examined microbiologically on two occasions with a 2-wk interval, resulting in a total of 384 and 295 oral washings, respectively. All patients were in a stable phase of disease throughout the study. The distribution of low (< or = 10(4)/ml) or high (> or = 10(5)/ml) concentrations of viridans streptococci did not differ substantially between asthma or COPD patients and control subjects. Potentially pathogenic microorganisms found in a low (< or = 10(4)/ml) or high (> or = 10(5)/ml) concentration were equally distributed between the two groups. Staphylococcus aureus and beta-hemolytic streptococci were found significantly less often in the asthma and COPD group (p < 0.005 and p < 0.0005, respectively), but the prevalence of Enterobacteriaceae species was significantly higher (p < 0.0005). No correlation was found between the concentration of viridans streptococci and the prevalence of gram-negative microorganisms. These findings suggest that viridans streptococci are probably not responsible for growth control of gram-negative microorganisms in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)