革兰阴性菌引起的血培养阳性标本的直接鉴定药敏试验

目的 为进一步缩短实验室菌血症诊断时间,评估联合法阳性血培养直接鉴定药敏试验的可行性.方法 将血培养瓶放人BACTEC 9000血培养系统进行培养筛选.选取65份含革兰阴性杆菌的阳性血培养瓶进行试验.抽取培养液,用BD真空分离管离心分离血细胞.在收集到足量菌液后,用Phoenix 100 NMIC/ID-4革兰阴性菌鉴定药敏卡做0.25 McF和0.5 McF直接鉴定药敏试验.用标准方法及哑培养后的鉴定药敏试验对直接鉴定药敏试验进行评估.结果 0.25 McF直接鉴定试验,65株中的63株(96.9%)准确鉴定.0.5 MeF直接鉴定试验,65株中的59株(90.8%)准确鉴定.0.25 McF直接药敏试验标准符合率97.8%以上.0.5 McF直接药敏试验标准符合率95.9%以上.KB法血标本直接药敏试验标准符合率96.4%以上,但微小错误率高于联合药敏法.结论 采用0.25 McF、0.5 McF两种菌液浓度法进行血培养阳性标本鉴定药敏试验是切实可行的.联合法0.25 McF菌液浓度的直接鉴定药敏试验具有明显优势,对临床具有很好的及时、有效地指引作用.     

革兰阴性菌引起的血培养阳性标本的直接鉴定药敏试验

目的 为进一步缩短实验室菌血症诊断时间,评估联合法阳性血培养直接鉴定药敏试验的可行性.方法 将血培养瓶放人BACTEC 9000血培养系统进行培养筛选.选取65份含革兰阴性杆菌的阳性血培养瓶进行试验.抽取培养液,用BD真空分离管离心分离血细胞.在收集到足量菌液后,用Phoenix 100 NMIC/ID-4革兰阴性菌鉴定药敏卡做0.25 McF和0.5 McF直接鉴定药敏试验.用标准方法及哑培养后的鉴定药敏试验对直接鉴定药敏试验进行评估.结果 0.25 McF直接鉴定试验,65株中的63株(96.9%)准确鉴定.0.5 MeF直接鉴定试验,65株中的59株(90.8%)准确鉴定.0.25 McF直接药敏试验标准符合率97.8%以上.0.5 McF直接药敏试验标准符合率95.9%以上.KB法血标本直接药敏试验标准符合率96.4%以上,但微小错误率高于联合药敏法.结论 采用0.25 McF、0.5 McF两种菌液浓度法进行血培养阳性标本鉴定药敏试验是切实可行的.联合法0.25 McF菌液浓度的直接鉴定药敏试验具有明显优势,对临床具有很好的及时、有效地指引作用.     

Metabolic Induction of Lactic Acid Bacteria for Urea Removal

Objective：This study aims to induce nonpathogenic bacteria for urea removal as a potential treatment in renal failure. Methods：Lactococus lactis MG1363 was induced by repeated exposure to urea-rich culture media, the ability to remove urea from the media was evaluated. The effect of gastroenteric environment, such as low pH, bile salt and antiagonistic properties were investigated. The antimicrobial activities on pathogenic E. coli and S. aureus in the intestinal tract and the antibiotic tolerance of the induced bacteria were also studied. Results ： Induced bacteria of 50 generations could decrease the urea level from 40.01 mg/dL to 32.99 mg/dL after 24 h. The bacteria could grow after treatment at pH3.0 for 2 h and in 0.1% bile salt for 6 h, and the urea removal activity was retained in such simulated gastroenteric environment. The removal of urea was significantly enhanced to 35.8% by addition of Ni^2＋ to the culture medium at neutral pH. It was also found that the induced bacteria could inhibit the growth of E. coli and S. aureus, and tolerate ampicillin, gentamicin, roxithromycin, tetracycline and cefradine. The safety tests were performed by feeding normal rats with either Lactococus lactis MG1363 or induced Laetococus lactis MG1363. The two materials did not cause any changes in blood cells, blood biochemical indexes and body weight. Conclusion： These results ＂suggest that the induced Laetoeocus lactis MG1363 has the potential as an oral therapy for the removal of urea in patients with renal failure.     

超声对金黄色葡萄球菌生物膜的体外破坏作用

BACKGROUND: Studies have shown that the ultrasound enhances the on bactericidal activity of antibiotics in an intensity-dependent manner, that is, the higher the ultrasound intensity, the greater its effectiveness.OBJECTIVE: To study the destructive effect of different intensities of ultrasound on Staphylococcus aureus and its biofilm.METHODS: Staphylococcus aureus biofilms were cultured in vitro using guide sheet culture method and divided into three groups for intervention. The biofilm in the control group received no treatment. The biofilm in the low-intensity ultrasound group was intervened by pulsed ultrasound with an intensity of 500 mW/cm and frequency of 200 kHz for 10 minutes. The biofilm in the high-intensity ultrasound group was intervened by continuous ultalsound with an intensity of 40 W and frequency of 1 MHz for 10 minutes. Bacterial colonies were counted using ultrasonic oscillation-live bacteria counting method. DNA and polysaccharide of the bacteria were respectively marked using propidium iodide and FITC-ConA. The molding of the bilfilm was determined using laser scanning confocal microscope.RESULTS AND CONCLUSION: The number of bacterial colonies in the high-intensity ultrasound group were lower than that in the control and low-intensity ultrasound groups (P < 0.05), and there were no significant differences between control and low-intensity ultrasound groups. There were no significant differences in the number and intensity of red fluorescence and green fluorescence between low-intensity ultrasound and control groups; however, the number and intensity of red fluorescence and green fluorescence in the high-intensity ultrasound group were significantly decreased compared with the low-intensity ultrasound and control groups. These results demonstrate that the low-intensity ultrasound cannot kill the bacteria and it has a tiny destructive effect on the biofilm of bacteria; however, the high-intensity ultrasound can effectively kill the bacteria and has a strong destructive effect on the bilfilm of bacteria.  中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

Molecular mechanism of the qnrA genemediated quionlone resistance in Gram-negative bacteria

To explore the prevalence of the plasmid-mediated quinolone resistance gene qnrA in Gramnegative bacteria and to investigate its molecular genetic background and resistance profile in isolates harboring this gene, a total of 629 nalidixic acid-resistant isolates of non-repetitive Gram-negative bacteria were collected from clinical specimens between April 2004 and April 2006 and these isolates were screened for qnrA gene by PCR using specific primers combined with DNA sequencing. The extended spectrum β-1actamase （ESBL） or AmpC-producing isolates were distinguished by the phenotypic confirmatory test combined with DNA sequencing, and the antibiotics susceptibility test for qnrA-positive isolates was carried out by Kirby-Bauer and E-test method. To detect the location of the qnrA gene, plasmid conjugation and Southern hybridization were performed and the integron structure containing the qnrA gene was cloned by PCR strategy and sequenced by primer walking. It was demonstrated that the incidence of the qnrA-positive strains in nalidixic acid-resistant bacteria was 1.9% （12/629）, in which the detection rates for Klebiesiella pneumoniae. Enterobacter cloacae, Enterobacter aerogenes, Citrobacterfreundii and Salmonella choeraesuis were 2.2% （3/138）, 17. 1% （6/35）, 9. 1% （1/11）, 12.5% （1/8）, and 14.3% （1/7）, respectively. The qnrA gene was found to be embedded in the complex sull-type integron located on plasmids with varied size （80-180 kb）. Among them, 4 qnrA-positive isolates carried integron In37 and 8 isolates carried a novel integron, temporarily desig- nated as InX. All the qnrA-positive isolates were ESBL-producing and transferable for the multi-drug resistance. It is concluded that the plasmid-mediated drug-resistance mechanism exists in the quinolone resistant strains of isolates from hospitals in Guangdong area, but the incidence was rather low. Nevertheless, it is still possible that the horizontal transfer of the resistant qnrA gene might lead to the spreading of drug-resista     

EMILIN1基因多态性与蒙古族原发性高血压相关性研究

Objective To explore the relationship between genetic polyrnorphisms of 3 single nucleotide polymorphisms (SNPs) in the elastin microfibril interfacer 1 (EMILIN1)gene and essential hypertension. Methods A case-control study was conducted in which 201 hypertensive patients and 202 healthy controls in Mongolian population were enrolled, and the genotypes of rs3754734, rs2011616 and rs2304682 loci were analyzed using polymerase chain reaction-restriction fragment length polyrnorphism (PCR-RFLP) and direct sequencing techniques. Results There were significant differences in the frequencies of alleles and genotypes for the rs2304682 between the hypertensives and normotensives in the population(P＜0. 05). The frequency of the G-G haplotype established by rs3754734 and rs2304682 was significantly higher in the hypertensive patients (P＜0. 05). The frequencies of alleles and genotypes for the rs2304682 also had significant differences between the group with high diastolic blood pressure and normal diastolic blood pressure (P＜0.05). There were no significant differences in the frequencies of alleles and genotypes for the 3 SNPs between the group with high systolic blood pressure and normal systolic blood pressure (P＞0.05). Conclusion The rs2304682 locus in the EMILIN1 gene, as well as the haplotypes G-G constructed using rs3754734 and rs2304682, may associate with the susceptibility of essential hypertension in the Mongolian population. Also, rs2304682 may associate with the level of the diastolic blood pressure.     

EMILIN1基因多态性与蒙古族原发性高血压相关性研究

Objective To explore the relationship between genetic polyrnorphisms of 3 single nucleotide polymorphisms (SNPs) in the elastin microfibril interfacer 1 (EMILIN1)gene and essential hypertension. Methods A case-control study was conducted in which 201 hypertensive patients and 202 healthy controls in Mongolian population were enrolled, and the genotypes of rs3754734, rs2011616 and rs2304682 loci were analyzed using polymerase chain reaction-restriction fragment length polyrnorphism (PCR-RFLP) and direct sequencing techniques. Results There were significant differences in the frequencies of alleles and genotypes for the rs2304682 between the hypertensives and normotensives in the population(P＜0. 05). The frequency of the G-G haplotype established by rs3754734 and rs2304682 was significantly higher in the hypertensive patients (P＜0. 05). The frequencies of alleles and genotypes for the rs2304682 also had significant differences between the group with high diastolic blood pressure and normal diastolic blood pressure (P＜0.05). There were no significant differences in the frequencies of alleles and genotypes for the 3 SNPs between the group with high systolic blood pressure and normal systolic blood pressure (P＞0.05). Conclusion The rs2304682 locus in the EMILIN1 gene, as well as the haplotypes G-G constructed using rs3754734 and rs2304682, may associate with the susceptibility of essential hypertension in the Mongolian population. Also, rs2304682 may associate with the level of the diastolic blood pressure.     

应用多重连接依赖式探针扩增技术快速高通量诊断胎儿染色体非整倍体异常

Objective To assess the diagnostic value of multiplex ligation-dependent probe amplification (MLPA) for detection of common chromosome aneuploidy in amniotic fluid (AF) cells in order to obtain an accurate, rapid, cost-effective and high-throughput method in routine prenatal clinical practice.Methods The MLPA test was performed on 500 AF samples by using kit P095 and the results were obtained by using analysis software RH-MLPA-v511. The results were compared with that from fluorescence in situ hybridization (FISH) and traditional karyotyping (TK). The technical critical issues were analyzed in routine diagnostic application. Results The absolute specificity and sensitivity of the MLPA test to detect the aneuploidy were 100%. For the 500 AF samples, the success rate of the MLPA tests was 97%. Among them 92% were finished within three working days and 5% required more days for repeating. The test failure rate was 3%. The results confirmed that for the 38 detectable aneuploid samples,the probe reliability weighted mean ratio values were more than 4SD compared to normal diploids and the 2 suspected trisomy samples were more than 2SD. In this study, authors analyzed hybridization efficiencies of 8 probes for chromosome 21, and the presence of a trisomy was considered if at least 4 of the 8 probes gave probe ratio of ＞1.3. Conclusion The data suggested that MLPA is a rapid, simple and reliable method for large scale testing for aneuploidy of chromosomes 13, 18, 21, X, or Y in AF. The MLPA technology is complementary to AF culture and valuable for prenatal diagnosis.     

应用多重连接依赖式探针扩增技术快速高通量诊断胎儿染色体非整倍体异常

Objective To assess the diagnostic value of multiplex ligation-dependent probe amplification (MLPA) for detection of common chromosome aneuploidy in amniotic fluid (AF) cells in order to obtain an accurate, rapid, cost-effective and high-throughput method in routine prenatal clinical practice.Methods The MLPA test was performed on 500 AF samples by using kit P095 and the results were obtained by using analysis software RH-MLPA-v511. The results were compared with that from fluorescence in situ hybridization (FISH) and traditional karyotyping (TK). The technical critical issues were analyzed in routine diagnostic application. Results The absolute specificity and sensitivity of the MLPA test to detect the aneuploidy were 100%. For the 500 AF samples, the success rate of the MLPA tests was 97%. Among them 92% were finished within three working days and 5% required more days for repeating. The test failure rate was 3%. The results confirmed that for the 38 detectable aneuploid samples,the probe reliability weighted mean ratio values were more than 4SD compared to normal diploids and the 2 suspected trisomy samples were more than 2SD. In this study, authors analyzed hybridization efficiencies of 8 probes for chromosome 21, and the presence of a trisomy was considered if at least 4 of the 8 probes gave probe ratio of ＞1.3. Conclusion The data suggested that MLPA is a rapid, simple and reliable method for large scale testing for aneuploidy of chromosomes 13, 18, 21, X, or Y in AF. The MLPA technology is complementary to AF culture and valuable for prenatal diagnosis.     

一种新生SD大鼠皮质源性神经元的培养方法

BACKGROUND: Primary culture in vitro of neurons plays an important role in the development, regeneration, signal transduction mechanisms, neuropharmacology and gene expressions of the nervous system. OBJECTIVE: To establish a simple method for primary culture of high-purity cortical neurons in neonatal Sprague-Dawley rats. METHODS: Cortical tissues were acquired from neonatal Sprague-Dawley rats born 1 day. In traditional experimental group, the whole cortex was removed; in improved experimental group, the cortical tissues, 2-3 mm thick on the brain surface were removed. Single cell suspensions were prepared after papain digestion and centrifugation and were then seeded onto 24-well culture plates containing neuron solutions for primary culture (1×105 per well). Cells were identified by neuronal specific markers MAP-2 and Tuj1 after 3-day culture. The number of neurons and neurite length were observed under inverted phase contrast microscope and recorded at 6, 24, 48 and 72 hours, 5 and 7 days of culture, resprctively. RESULTS AND CONCLUSION:The cultured cells expressing MAP-2 and Tuj1 were neurons that could be used in the following experiments. The purity of neurons in the improved experimental group was 92% at 3 days, while only 51% in the traditional experimental group. Cells in both two groups had attached to the wall presenting with small processes at 6 hours, and a simple neural network formed at the 3rd day until dense neural networks could be found at the 5th day. To conclude, our culture method herein is simple and convenient, and can be used to produce neurons with high purity, which will be helpful for the experimental studies on cortical neurons from Sprague-Dawley rats. 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Identification and susceptibility testing of Enterobacteriaceae and Pseudomonas aeruginosa by direct inoculation from positive BACTEC blood culture bottles into Vitek 2

Inoculation of an automated system for rapid identification (ID) and antimicrobial susceptibility testing (AST) directly from positive blood culture bottles will reduce the turnaround time of laboratory diagnosis of septicemic patients, which benefits clinical outcome and decreases patient costs. Direct test results, however, must always be confirmed by testing a pure overnight culture, which is the "gold standard." We studied the accuracy of direct testing versus repeat testing in order to investigate the possibility of refraining from repeat testing. We also assessed the clinical risk of reporting results based on direct testing only. We inoculated Vitek 2 (bioMérieux) directly from 410 positive BACTEC 9240 (BD) blood culture bottles containing gram-negative rods and studied the ID and AST results. In a comparison of direct inoculation with the standard method, a total of 344 isolates of Enterobacteriaceae and Pseudomonas aeruginosa were tested, and 93.0% were correctly identified. Of the 39 (10.2%) samples that contained bacilli not identifiable by Vitek 2, only 1 gave a conclusive, correct result. The overall MIC agreement among 312 isolates was 99.2%, with 0.8% very major and 0.02% major error rates. Of only three (polymicrobial) samples, the direct susceptibility pattern would be reported to the clinician as too sensitive. Vitek 2 results obtained from direct inoculation of blood culture bottles containing gram-negative bacilli are safe enough for immediate reporting, provided that ID and AST are consistent. Repeat testing is not necessary, unless Gram stain or overnight subculture results raise doubt about the purity of the culture.     

Use of positive blood cultures for direct identification and susceptibility testing with the vitek 2 system

In order to further decrease the time lapse between initial inoculation of blood culture media and the reporting of results of identification and antimicrobial susceptibility tests for microorganisms causing bacteremia, we performed a prospective study in which specially processed fluid from positive blood culture bottles from Bactec 9240 (Becton Dickinson, Cockeysville, Md.) containing aerobic media were directly inoculated into Vitek 2 system cards (bio-Mérieux, France). Organism identification and susceptibility results were compared with those obtained from cards inoculated with a standardized bacterial suspension obtained following subculture to agar; 100 consecutive positive monomicrobic blood cultures, consisting of 50 gram-negative rods and 50 gram-positive cocci, were included in the study. For gram-negative organisms, 31 of the 50 (62%) showed complete agreement with the standard method for species identification, while none of the 50 gram-positive cocci were correctly identified by the direct method. For gram-negative rods, there were 50% categorical agreements between the direct and standard methods for all drugs tested. The very major error rate was 2.4%, and the major error rate was 0.6%. The overall error rate for gram-negatives was 6.6%. Complete agreement in clinical categories of all antimicrobial agents evaluated was obtained for 19 of 50 (38%) gram-positive cocci evaluated; the overall error rate was 8.4%, with 2.8% minor errors, 2.4% major errors, and 3.2% very major errors. These findings suggest that the Vitek 2 cards inoculated directly from positive Bactec 9240 bottles do not provide acceptable bacterial identification or susceptibility testing in comparison with corresponding cards tested by a standard method.     

Rapid identification and susceptibility testing using the VITEK(R) 2 system using culture fluids from positive BacT/ALERT(R) blood cultures

BACKGROUND AND PURPOSE: In order to reduce the turnaround time for laboratory diagnosis of bacteremia, the efficacy of identification and antimicrobial susceptibility testing using samples taken directly from positive BacT/ALERT(R) standard aerobic and standard anaerobic blood culture bottles was evaluated. METHODS: 160 positive blood culture bottles were examined and incubated at 35 degrees C in 5% carbon dioxide for 4-24 h, and an aliquot of the culture fluid was Gram stained. Samples containing Gram-negative bacilli were inoculated on VITEK(R) 2 ID-GNB (identification-Gram-negative bacilli) and AST (antimicrobial susceptibility testing)-GN04 cards, and those containing Gram-positive cocci were inoculated on ID-GPC (identification-Gram-positive cocci) and AST-P526 cards. The same samples were also examined by the standard method, involving subculture from positive BacT/ALERT standard blood culture bottles. RESULTS: Eighty seven of 97 Gram-negative bacilli (89.7%) and 21 of 63 Gram-positive cocci (33.3%) were correctly identified to the species level. For antimicrobial susceptibility testing, the direct method had an overall error rate of 5.4% for Gram-negative bacilli, with 0.9% very major, 0.9% major, and 3.6% minor discrepancies compared to the standard method. The overall error rate in antimicrobial susceptibility testing for the 13 Staphylococcus spp. was 10.3%, with 6.0% very major, 2.6% major, and 1.7% minor discrepancies. CONCLUSION: These data suggest that VITEK 2 cards inoculated with samples taken directly from positive Bact/ALERT blood culture bottles would provide acceptable identification and antimicrobial susceptibility testing results for Gram-negative bacilli, but not for Gram-positive cocci. Compared to the standard method, the direct method would reduce turnaround time by at least 24 h.     

Rapid identification and antimicrobial susceptibility testing of gram-negative bacilli from blood cultures by the AutoMicrobic system.

A procedure was developed which allows direct identification and antimicrobial susceptibility testing of fermentative and nonfermentative gram-negative bacilli from positive blood cultures. A 10-ml sample was removed from turbid blood culture bottles, and the bacteria were washed and concentrated by centrifugation. The bacterial pellet was used to inoculate an Enterobacteriaceae Plus Identification Card and a Gram-Negative General Susceptibility Card of the AutoMicrobic system. Results with these cards were compared with results obtained with standard technique for 196 blood cultures seeded with recent clinical isolates. Identification of most cultures was available in 8 h, whereas the antimicrobial susceptibility results were available in an average of 4.7 h for all organisms. Direct identification was correct for 95% of the cultures, whereas the antimicrobial susceptibility data had an average agreement of 87% with 3.8% very major and 1.4% major errors. In using this procedure it was possible to provide accurate preliminary identification and results of antimicrobial susceptibility tests for gram-negative bacilli on the same day that a blood culture was determined to be positive.     

Detection of Salmonella spp. in clinical specimens by capture enzyme-linked immunosorbent assay.

A capture enzyme-linked immunosorbent assay (ELISA; Kirkegaard and Perry Laboratories, Gaithersburg, Md.) was used to detect Salmonella spp. in clinical and artificially inoculated specimens. In patients with bacteremia caused by Salmonella spp., 48% (12 of 25) and 82% (13 of 16) of serum and urine specimens, respectively, were positive for Salmonella spp., as determined by ELISA. All serum and urine specimens collected from healthy individuals (25 specimens) or patients whose blood cultures grew gram-negative bacteria other than Salmonella spp. (18 specimens) were negative for Salmonella spp., as determined by ELISA. For blood culture bottles in which Salmonella spp. (16 specimens) was grown the ELISA was positive (100%), while it was negative for all the 65 blood culture bottles in which gram-negative bacteria other than Salmonella spp. (42 specimens) or gram-positive bacteria (23 specimens) were grown. All samples of urine (16 specimens), stool (8 specimens), serum (16 specimens), culture media (12 specimens), and blood culture bottles (reported sterile after 2 weeks of incubation; 16 specimens) that were artificially inoculated with 10(3) to 10(7) CFU of four species of Salmonella per ml were positive by ELISA. Similar specimens inoculated with or containing various species other than Salmonella were negative by this test. Thus, ELISA offers a promising opportunity for the rapid detection of Salmonella spp. in clinical microbiology laboratories.     

Evaluation of an accelerated protocol for detection of extended-spectrum beta-lactamase-producing gram-negative bacilli from positive blood cultures

We evaluated a protocol for the accelerated detection of extended-spectrum beta-lactamases (ESBLs) in gram-negative bloodstream pathogens. Two hundred eighty-three blood culture bottles were subjected to direct ESBL testing by inoculating samples directly from blood culture bottles onto agar plates containing cefotaxime and ceftazidime disks, with and without clavulanate. Standard ESBL testing in accordance with the NCCLS guidelines after subculturing on agar plates was performed in parallel. Results of the direct ESBL testing were reported 2.3 days sooner and were comparable to those of the standard NCCLS method with sensitivity, specificity, and positive and negative predictive values of 100, 98, 94, and 100%, respectively.     

Rapid detection of Klebsiella pneumoniae carbapenemase genes in enterobacteriaceae directly from blood culture bottles by real-time PCR

Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae are endemic in New York City hospitals and have been associated with serious infections globally. A real-time polymerase chain reaction (RT-PCR) assay was developed to detect carbapenem resistance attributable to KPC from blood culture bottles positive for gram-negative bacilli. Culture confirmation of carbapenemase production included automated imipenem and meropenem susceptibility testing and ertapenem susceptibility testing by disk-diffusion. A total of 323 Enterobacteriaceae isolates were tested, of which 8.7% (n = 28) demonstrated carbapenem-resistance by automated and manual susceptibility testing methods or by RT-PCR. The sensitivity, specificity, and positive and negative predictive values of the RT-PCR assay when compared with the automated method were 92.9%, 99.3%, 92.9%, and 99.3%, respectively, and 96.4%, 99.7%, 96.4%, and 99.7%, respectively, when compared with the ertapenem disk-diffusion method. RT-PCR is a rapid and reliable means of detecting carbapenem resistance due to KPC-plasmids in Enterobacteriaceae directly from blood culture bottles.     

Direct susceptibility testing of positive blood cultures by using Sensititre broth microdilution plates

Traditional susceptibility testing of blood cultures requires overnight incubation in order to obtain isolated colonies. Susceptibility results can be reported up to 24 h sooner by using a bacterial pellet from the blood culture broth. This study evaluated the accuracy of direct susceptibility testing from positive ESP blood culture broths by using Sensititre broth microdilution plates compared to testing with isolated colonies. Practical inclusion criteria were applied to gram-positive organisms to avoid reporting susceptibilities for probable contaminants. All gram-negative organisms were tested directly. An aliquot of the blood culture was centrifuged, and the resulting pellet was used to make a 0.5 McFarland suspension. Microdilution plates were inoculated and interpreted according to the manufacturer's instructions. Colony counts were performed to ensure proper colony density was achieved. A total of 199 patient and seeded blood cultures were evaluated for both essential (within +/-1 twofold dilution) and categorical (sensitive, intermediate, or resistant) agreement. Testing of 93 gram-positive isolates (1,214 antimicrobial agent-organism combinations) yielded 98% essential agreement and categorical error rates of 0.3% minor, no major (false resistance), and 1.7% very major (false susceptibility) errors. For 106 gram-negative isolates (1,828 antimicrobial agent-organism combinations), the essential agreement was 99%. Categorical error rates were 0.5, 0, and 2.0% for minor, major, and very major errors, respectively. Performance was comparable for both gram-positive and gram-negative isolates, as well as for both aerobic and anaerobic media. Using this direct testing methodology, reliable susceptibility results can be reported to physicians 24 h sooner, allowing earlier appropriate modification of antimicrobial therapy.