Performance of two tube coagulase methods for rapid identification of Staphylococcus aureus from blood cultures and their impact on antimicrobial management.

Test parameters and clinical impact of the direct tube coagulase test (DTCT) for rapid identification of Staphylococcus aureus from blood culture were investigated. The sensitivity of the DTCT at 4 h using saline dilution was 96%, compared with 93% using serum separator tubes; specificity was 100% for both methods. Among 32 patients with S. aureus bacteraemia, treatment modifications were based on microbiology results from the primary source of infection in 12 patients, on a Gram's stain from blood culture in seven patients, and on the DTCT in nine patients. The DTCT is a valuable adjunct in the routine microbiology laboratory because of its good performance, technical simplicity and low cost.

Ventilator-associated pneumonia caused by Dolosigranulum pigrum.

Dolosigranulum pigrum is an unusual gram-positive catalase-negative coccus. It was isolated, only after prolonged incubation, from bronchial secretions from a patient with ventilator-associated pneumonia. The patient responded well to antimicrobial therapy. Identification was done by 16S rRNA DNA sequence analysis, but it can be done with relatively simple phenotypic tests.

Urosepsis with Actinobaculum schaalii and Aerococcus urinae.

Actinobaculum was isolated from urine only after prolonged incubation in 5% CO(2) after discrepancy between urine Gram stain and initial culture results was observed. Additional patients were diagnosed using this method. The prevalence of Actinobaculum species in urinary tract infections is underestimated since it is not isolated by routine urine culture procedures.

Coagulase-negative staphylococci as a cause of infections related to intravascular prosthetic devices: limitations of present therapy.

Coagulase-negative staphylococci (CNS) are an important cause of catheter-related bloodstream infections. This review will shed light on the pathogenesis related to biofilm formation, and will discuss antimicrobial susceptibility of CNS to older and newer antibiotics, as well as therapeutic options.

Chronic melioidosis in a patient with cystic fibrosis.

Burkholderia pseudomallei, the causative agent of melioidosis, is endemic in Southeast Asia and northern Australia, where it can be found in soil and surface water. We report a case of chronic pulmonary melioidosis in a patient with cystic fibrosis who had traveled to an area where B. pseudomallei is endemic.

Activities of the oxazolidinones linezolid and eperezolid in experimental intra-abdominal abscess due to Enterococcus faecalis or vancomycin-resistant Enterococcus faecium.

The in vivo effectiveness of oxazolidinones eperezolid (U-100592) and linezolid (U-100766) against one strain each of Enterococcus faecalis and vancomycin-resistant Enterococcus faecium was examined in a rat model of intra-abdominal abscess. MICs of both drugs were 2 microg/ml for each strain. At doses of 25 mg/kg of body weight twice daily intravenously or orally, linezolid produced small but statistically significant reductions in abscess bacterial density for E. faecalis. The reduction in viable cells observed would not likely be clinically relevant. Eperezolid was ineffective at this dose. At a dosage of 100 mg/kg/day, linezolid treatment led to an approximately 100-fold reduction in viable cells per gram of abscess. Against E. faecium infections, intravenous eperezolid and oral linezolid were effective, reducing densities approximately 2 log(10) CFU/g. Both oxazolidinones demonstrated activity against enterococci in this model. However, results were modest with the dosing regimens employed.

In-vitro activity of the new ketolide antibiotic HMR 3647 against gram-positive bacteria.

The comparative in-vitro activity of HMR 3647, a new ketolide antibiotic, was investigated against 492 clinical isolates of gram-positive bacteria, including multiply resistant strains, by an agar-dilution technique. All streptococci tested were inhibited by the new ketolide at concentrations < or = 0.5 mg/L. HMR 3647 was more potent than erythromycin against staphylococci. For enterococci the new compound yielded an MIC90 of 8 mg/L. Erysipelothrix spp., Pediococcus spp., Leuconostoc spp., Lactobacillus spp., JK diphtheroids and Listeria monocytogenes were also susceptible to the new ketolide.

Susceptibilities of Legionella spp. to newer antimicrobials in vitro.

The in vitro activities of 13 antimicrobial agents against 30 strains of Legionella spp. were determined. Rifapentine, rifampin, and clarithromycin were the most potent agents (MICs at which 90% of isolates are inhibited [MIC90s], < or = 0.008 microgram/ml). The ketolide HMR 3647 and the fluoroquinolones levofloxacin and BAY 12-8039 (MIC90s, 0.03 to 0.06 microgram/ml) were more active than erythromycin A or roxithromycin. The MIC90s of dalfopristin-quinupristin and linezolid were 0.5 and 8 micrograms/ml, respectively. Based on class characteristics and in vitro activities, several of these agents may have potential roles in the treatment of Legionella infections.

Characterization of vancomycin-resistant Enterococcus faecium isolates from the United States and their susceptibility in vitro to dalfopristin-quinupristin.

In the course of clinical studies with the investigational streptogramin antimicrobial dalfopristin-quinupristin, isolates of vancomycin-resistant Enterococcus faecium were referred to our laboratory from across the United States. Seventy-two percent of the strains were of the VanA type, phenotypically and genotypically, while 28% were of the VanB type. High-level resistance to streptomycin or gentamicin was observed in 86 and 81%, respectively, of the VanA strains but in only 69 and 66%, respectively, of the VanB strains. These enterococci were resistant to ampicillin (MIC for 50% of the isolates tested [MIC50] and MIC90, 128 and 256 microg/ml, respectively) and to the other approved agents tested, with the exception of chloramphenicol (MIC90, 8 microg/ml) and novobiocin (MIC90, 1 microg/ml). Considering all of the isolates submitted, dalfopristin-quinupristin inhibited 86.4% of them at concentrations of < or = 1 microg/ml and 95.1% of them at < or = 2 microg/ml. However, for the data set comprised of only the first isolate submitted for each patient, 94.3% of the strains were inhibited at concentrations of < or = 1 microg/ml and 98.9% were inhibited at concentrations of < or = 2 microg/ml. Multiple drug resistance was very common among these isolates of vancomycin-resistant E. faecium, while dalfopristin-quinupristin inhibited the majority at concentrations that are likely to be clinically relevant.

In vitro activity of RU 64004, a new ketolide antibiotic, against gram-positive bacteria.

The comparative in vitro activity of RU 64004 (also known as HMR 3004), a new ketolide antibiotic, was tested by agar dilution against approximately 500 gram-positive organisms, including multiply resistant enterococci, streptococci, and staphylococci. All streptococci were inhibited by < or = 1 microg of RU 64004 per ml. The ketolide was more potent than other macrolides against erythromycin A-susceptible staphylococci and was generally more potent than clindamycin against erythromycin A-resistant strains susceptible to this agent. Clindamycin-resistant staphylococci (MIC, > 128 microg/ml) proved resistant to the ketolide, but some erythromycin A- and clindamycin-resistant enterococci remained susceptible to RU 64004.

Rapid drug susceptibility testing of Mycobacterium tuberculosis using conventional solid media.

Radiometric methods for M. tuberculosis drug susceptibility testing yield much faster results than standard techniques; however, these methods require sophisticated equipment and are expensive. We investigated a rapid drug susceptibility testing method for isoniazid, rifampin, ethambutol, streptomycin and pyrazinamide in specimens from 197 patients with pulmonary tuberculosis using a simplified agar-dilution method. Middlebrook 7H11 agar solid medium and microcolony detection were used to test sputum from 64 smear-positive, and from 70 culture-positive but smear-negative patients. Culture-positive material from bronchoscopy, surgical biopsy, pleural fluid or gastric fluid of 63 patients was tested. In 64 smear-positive patients, the median time for final susceptibility results was 11 days (95% confidence interval (95% CI) 10-12 days) compared to 62 days (95% CI 56-66 days) with the standard method. In 133 smear-negative patients, results were available after a median of 35 days (95% CI 32-40 days) in contrast to 72 days (95% CI 62-83 days) with the standard method, regardless of whether or not sputum or other materials were used for primary culture. The rapid method detected all cases of single-drug resistance (n = 20) and multidrug resistance (n = 14) within 13 days (95% CI 9-17 days) in smear-positive patients (n = 8), or within 38 days (95% CI 35-48 days) in smear-negative patients (n = 26). Only one discrepancy was encountered in 985 resistance tests. Moreover, contamination was not observed. Our rapid susceptibility testing method for M. tuberculosis on Middlebrook 7H11 agar is fast, practical and inexpensive. It provides an alternative when more sophisticated techniques are not available or affordable.