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The bacterial index (BI) as defined by the sum of log10 colony-forming units (cfu) of microorganisms per milliliter of bronchoalveolar lavage (BAL) fluid, i.e., a multiplication of the single cfu/ml, has been used to distinguish between polymicrobial pneumonia (BI> or =5) and colonization (BI<5). Since many false-positive results are to be expected using this parameter, the diagnostic value of the BI was studied prospectively by obtaining bacteriologic cultures of BAL fluid in 165 consecutive unselected patients. In 27 cases the diagnosis of bacterial pneumonia was established on clinical criteria. In 133 patients pneumonia could be excluded, and in five patients the diagnosis remained unclear. Using a cut-off of > or = 10(5) cfu/ml BAL fluid, sensitivity and specificity for the diagnosis of pneumonia were 33% (9/27) and 99% (132/133), respectively. Sensitivity was mainly influenced by prior treatment with antibiotics, being 70% (7/10) in untreated and 12% (2/17) in treated patients. Applying the BI methodology at a cut-off of > or =5, however, resulted in an unacceptably high rate of 16 additional false-positive results, thus lowering the specificity to 87% (116/133; P<0.0001) while increasing the sensitivity to only 41% (11/27; P = 0.77). In conclusion, given the high rate of false-positive results, the methodology of the BI is of doubtful value for the diagnosis of bacterial pneumonia by BAL in an unselected patient group. By applying the absolute number of cfu/ml BAL fluid, however, positive bacteriologic cultures of BAL fluid are highly specific for the diagnosis of pneumonia. Their sensitivity is limited by previous antibiotic therapy.

The in vitro activity of ceftriaxone combined with tazobactam against 190 strains of anaerobic bacteria was compared with that of amoxicillin with clavulanic acid, ampicillin with sulbactam, piperacillin alone and with tazobactam, cefoxitin, and imipenem, i.e. beta-lactam antibiotics established in the treatment of anaerobic infections. All anaerobes tested were susceptible to < or = mg/l ceftriaxone when tazobactam was added at fixed ratios (ceftriaxone to tazobactam) of 2:1 and 8:1 and at constant concentrations of 2,4 and 8 mg/l, respectively. When 4 mg/l tazobactam was added, the MICs of ceftriaxone for 83 of 94 strains of the Bacteroides fragilis group were reduced by a factor of 8 to 512; for eight strains, this reduction was two to fourfold. Only the MICs of ceftriaxone for three Bacteroides fragilis strains were not influenced.

The performance of two enzyme immunoassays for rapid detection of group B streptococci (GBS) was evaluated in comparison to culture using cervical swabs from 191 pregnant women. Ten percent of the women harboured GBS. There were two positive results in the Icon assay (Hybritech), both in women with heavy growth in the culture, and four positive results in the Quidel assay (Quidel), two in the women with heavy colonization and one each in women with moderate and light growth of GBS respectively. The sensitivity of both assays was low, being 11% (2/18) for the Icon assay and 24% (4/17) for the Quidel assay. The specificity of both assays was 100%. Both assays could detect > or = 10(6) group B streptococci per swab. A positive result justifies ampicillin prophylaxis due to the high risk for the newborn. A negative result should be confirmed by rapid culture techniques.

The susceptibility of 146 recent clinical isolates of gram-negative and gram-positive anaerobes was determined by the E test (AB Biodisk) on both Wilkins-Chalgren and PDM ASM II (AB Biodisk) agar. Results of the E test were compared with results obtained by the NCCLS agar dilution method using Wilkins-Chalgren agar. Incubation was for 20 hours and 44 hours in the E test and for 44 hours in the NCCLS method. In general, 44 hour results were more reliable; however, NCCLS readings were made only once after 44 hours. After two days of incubation, 91% of E test results on Wilkins-Chalgren agar were within one dilution and 98% within two dilutions of the corresponding NCCLS values; on PDM agar these values were 89% and 98%, respectively. Major and very major discrepancies combined were less than 1%.

The in vitro activity of the ester Ro 41-3399 and its free active acid Ro 40-6890 was tested against 189 strains of anaerobic bacteria in comparison to other oral cephalosporins and to antimicrobial agents established in the treatment of anaerobic infections. Prevotella, Porphyromonas, Peptostreptococcus, Fusobacterium and Clostridium spp. were susceptible to Ro 40-6890, with few exceptions. Due to its lack of activity against the major pathogens of the Bacteriodes fragilis group, Ro 40-6890 does not promise to be of major use in the treatment of infections caused by anaerobes.

Sparfloxacin disk susceptibility test criteria for the NCCLS and ICS/DIN methods were determined by testing 400 bacterial wild-type isolates. Disks containing 5 micrograms of the drug could be used satisfactorily in both procedures. The following interpretive zone size breakpoints for the NCCLS and ICS/DIN methods were proposed: less than or equal to 18 and 20 mm respectively for resistance (MIC greater than 1 mg/l), and greater than or equal to 23 and 25 mm respectively for susceptibility (MIC less than or equal to 0.5 mg/l). These criteria were based on preliminary maximum serum concentrations of approximately 1.5 mg/l after a single oral dose of 400 mg of the drug. Regression equations for both methods correlating MICs and zone sizes based on test results for 361 organisms are presented. The equations allow calculation of breakpoints for higher or lower serum peak levels. Sparfloxacin was two to four times more active than ciprofloxacin against gram-positive cocci, and showed equal activity against gram-negative rods. Zone diameter quality control values for Escherichia coli ATCC 25922 were 26-30 mm (NCCLS) and 30-33 mm (ICS/DIN), and for Staphylococcus aureus ATCC 29213 27-28 mm (NCCLS) and 29-31 mm (ICS/DIN).

One hundred ninety-eight (89.2%) of 222 isolates of Enterobacteriaceae were correctly identified by the manual Cobas-IDA system; 19 (8.5%) could not be identified within 4 h and required additional testing. Five strains (2.3%) were misidentified.

The results of susceptibility tests performed by the Cobas-Bact system were compared with those of the NCCLS agar diffusion (Kirby-Bauer) and NCCLS agar dilution methods. A total of 998 clinical isolates were tested against 10 to 18 antimicrobial agents. Essential agreement (comprising full agreement and minor discrepancies) varied from 90.5% to 99.2% on comparison of Cobas-Bact with Kirby-Bauer results, depending on the bacterial group (mean for all 998 strains tested 95.7%). These figures ranged from 91% to 99.2% (mean 96.3%) for the Cobas-Bact/MIC comparison and from 95.2% to 99.7% (mean 98.7%) for the Kirby-Bauer/MIC comparison. The best results were found for Enterobacteriaceae and Staphylococcus aureus, whereas for enterococci and coagulase-negative staphylococci there was a lower rate of essential agreement in all three comparisons. In the case of Pseudomonas aeruginosa there was a good rate of essential agreement but many minor discrepancies, resulting in a disappointing rate of full agreement of between 67.5% and 78.9% in the three comparisons. The Cobas-Bact system would appear to provide satisfactory susceptibility test results in most cases, however there are still some major problems in the system which should be resolved.