Use of BACTEC 9240 blood culture system for detection of Brucella melitensis in synovial fluid

Laboratory Diagnosis of Human Brucellosis

The clinical presentation of brucellosis in humans is variable and unspecific, and thus, laboratory corroboration of the diagnosis is essential for the patient's proper treatment. The diagnosis of brucellar infections can be made by culture, serological tests, and nucleic acid amplification assays. Modern automated blood culture systems enable detection of acute cases of brucellosis within the routine 5- to 7-day incubation protocol employed in clinical microbiology laboratories, although a longer incubation and performance of blind subcultures may be needed for protracted cases. Serological tests, though they lack specificity and provide results that may be difficult to interpret in individuals repeatedly exposed to Brucella organisms, nevertheless remain a diagnostic cornerstone in resource-poor countries. Nucleic acid amplification assays combine exquisite sensitivity, specificity, and safety and enable rapid diagnosis of the disease. However, long-term persistence of positive molecular test results in patients that have apparently fully recovered is common and has unclear clinical significance and therapeutic implications. Therefore, as long as there are no sufficiently validated commercial tests or studies that demonstrate an adequate interlaboratory reproducibility of the different homemade PCR assays, cultures and serological methods will remain the primary tools for the diagnosis and posttherapeutic follow-up of human brucellosis.

Synovial fluid culture: agar plates vs. blood culture bottles for microbiological identification

OBJECTIVES

Bacteriological diagnosis of septic arthritis (SA) is complicated. Agar plates are the main culture method and yields 40-60% of positive bacterial detection. Addition of bottled culture broth (Bactec®) as a method for detecting synovial microorganisms is common. The advantages of this method and the combination of both have not been thoroughly investigated. This study evaluates an added value of the Bactec culture broth as a single method or as combined with the agar-plate culture.

METHODS

All culture aspirates of SA-suspected patients were analyzed. All cases with a positive result by either method were reviewed for background data and clinical diagnosis.

RESULTS

Out of 5000 synovial fluid samples, a clinical diagnosis of SA was suspected in 1024 cases. Samples processed by both culture methods were extracted during the same event. Bactec® vials were positive for significant bacterial detection in 113/148 cases (76.4%) while agar-plate cultures were positive in only 96/154 (62.3%) representing higher sensitivity of 0.5 vs. 0.42 and a positive predictive value (PPV) of 0.76 vs. 0.62. Bacterial detection by both methods combined was positive in 137/221 (62%) and did not achieve a significant increment.

CONCLUSIONS

The Bactec® method has many advantages in bacteriological identification of synovial infection, including a broader identification spectrum, faster response time, and superior qualities of identification although being more expensive. This method has a better yield in detecting septic arthritis and might be considered a single method for synovial fluid culture in cases suspected for SA.Key Points• The Bactec method had improved detection rates.• Culturing by agar plates and Bactec revealed higher sensitivity and lower specificity.• The use of the blood culture bottles (Bactec system) alone will raise the detection rate of septic arthritis with lower false positive rates and at lower costs.

Diversity of virulence genes in Brucella melitensis and Brucella abortus detected from patients with rheumatoid arthritis

The presence of Brucella melitensis and Brucella abortus genomes were investigated in the synovial fluid (SF) samples from 90 patients with rheumatoid arthritis (RA). DNA extraction and PCR assay were performed for simultaneous identification and discrimination of B. melitensis and B. abortus from the SF using three specific primers. After gel electrophoresis, the PCR products were confirmed by DNA sequencing. The cbg, omp31, manA, virB, and znuA virulence genes typing were performed by multiplex-PCR. Of the 90 samples, 14 were positive for B. melitensis (n = 9; 10%) and B. abortus (n = 5; 5.5%). The virulotyping of positive samples revealed the presence of all five virulence genes in B. melitensis. The virB, cbg, and om31 were detected in all five samples of B. abortus. In addition, zhuA and manA were detected in three (60%) and four (80%) samples, respectively, of the B. abortus-positive samples. Moreover, a total of 94.2% and 89.2% of the 14 positive samples were also found positive for manA and znuA, respectively. Our findings revealed that the Brucella spp. genomes can be detected in the SF of RA patients by the PCR-based method. We thus suggest that physicians should consider the Brucella spp. as indicators of potential RA for the timely diagnosis and treatment of RA.

Highly Sensitive Bacteriophage-Based Detection of Brucella abortus in Mixed Culture and Spiked Blood

For decades, bacteriophages (phages) have been used for Brucella species identification in the diagnosis and epidemiology of brucellosis. Traditional Brucella phage typing is a multi-day procedure including the isolation of a pure culture, a step that can take up to three weeks. In this study, we focused on the use of brucellaphages for sensitive detection of the pathogen in clinical and other complex samples, and developed an indirect method of Brucella detection using real-time quantitative PCR monitoring of brucellaphage DNA amplification via replication on live Brucella cells. This assay allowed the detection of single bacteria (down to 1 colony-forming unit per milliliter) within 72 h without DNA extraction and purification steps. The technique was equally efficient with Brucella abortus pure culture and with mixed cultures of B. abortus and α-proteobacterial near neighbors that can be misidentified as Brucella spp., Ochrobactrum anthropi and Afipia felis. The addition of a simple short sample preparation step enabled the indirect phage-based detection of B. abortus in spiked blood, with the same high sensitivity. This indirect phage-based detection assay enables the rapid and sensitive detection of live B. abortus in mixed cultures and in blood samples, and can potentially be applied for detection in other clinical samples and other complex sample types.

Comparison of BacT/Alert FAN and FAN Plus Bottles with Conventional Medium for Culturing Cerebrospinal Fluid

We compared the BacT/Alert system FAN and FAN Plus media to conventional media for culturing cerebrospinal fluid (CSF) with 2,545 samples. FAN/FAN Plus bottles showed better performance for isolating microorganisms in CSF than conventional media (positive rate, 7.2% [182/2,545] versus 3.1% [80/2,545]). The incremental recovery rate of Cryptococcus neoformans from FAN Plus bottles was higher than that from FAN bottles.

A case of brucellar monoarthritis and review of the literature

Brucellosis is a systemic infectious disease, which constitutes a public health problem in Turkey. Brucellosis has a broad spectrum of clinical manifestations. Osteoarthicular manifestations are often seen in brucellosis but most of the brucellar monoarthritis cases are reactive rather than being septic. We report a case of brucellar (septic) monoarthritis of the knee in a 74-year-old cattleman and review of the literature.

Bacterial septic arthritis in adults

Symptoms and signs of septic arthritis are an important medical emergency, with high morbidity and mortality. We review the changing epidemiology of septic arthritis of native joints in adults, encompassing the increasing frequency of the disorder and its evolving antibiotic resistance. We discuss various risk factors for development of septic arthritis and examine host factors (tumour necrosis factor alpha, interleukins 1 and 10) and bacterial proteins, toxins, and enzymes reported to be important determinants of pathogenesis in mouse models. Diagnosis of disease is largely clinical, guided by investigations and the opinion of skilled clinicians. We emphasise the need for timely medical and surgical intervention-most importantly, through diagnostic aspiration of relevant joints, choice of suitable antibiotic, and appropriate supportive measures. Management is growing in complexity with the advent of novel and antibiotic-resistant causative microorganisms and within the current climate of increased immunosuppression. Findings from animal models and patients are shedding light on disease pathogenesis and the possibility of novel adjunctive treatments, including systemic corticosteroids, cytokines and anticytokines, and bisphosphonates.

Evaluation of an automated blood culture system for the isolation of bacteria from equine synovial fluid

The objective of this study was to evaluate an automated blood culture system for the isolation of microorganisms from infected equine synovial fluid (SF). Samples were collected from 220 severely inflamed synovial joints and classified as either presumably infected (group A: n=149) or not infected (group B: n=71), based on a combination of clinical history, clinical signs and cytological analysis of the SF. Samples were inoculated into blood culture bottles and after incubation were subcultured onto agar media to confirm the results and to facilitate full bacterial identification. Microorganisms were isolated from 107 group A samples (71.8%) and from three group B samples (4.2%). Overall, the detection system identified 117 bottles as positive and 103 as negative, including nine instrument-false-positives and two instrument-false-negatives. The median time-to-detection for Gram-positive bacteria, Gram-negative bacteria, and for fungi was 14.3 (interquartile range [I.R.] 10.0) h, 8.8 (I.R. 12.8) h, and 72.0 (range 60.8-74.8) h, respectively. It was concluded that culture of infected SF using the automated system combines the advantages of enrichment in specialised medium with the rapid detection of bacterial growth.

Epidemiology and antibacterial susceptibility patterns of bloodstream infections, 2001-2004: an experience with BACTEC 9240 in Southern Iran

This study was conducted to determine the prevalence of bacteria recovered from bloodstream samples by Bactec 9240 at our hospital wards and to evaluate their antibacterial susceptibility patterns. During January 2001 through December 2004, 9407 referred blood samples in Bactec bottles from admitted patients at three main wards, neonates, pediatrics and adults at Nemazee Hospital, affiliated to Shiraz University of Medical Sciences in Shiraz were processed. Positive cultures were purified and identified according to standard methods. Sensitivity of bacteria to different antibiotics was determined by Kirby-Bauer disk diffusion method. Staphylococcus aureus 132(25%), Escherichia coli 64(12.1%) and Pseudomonas aeruginosa 52(9.8%) were the most pathogenic bacteria which were recovered from the blood samples. Pathogenic microorganisms were isolated from blood samples of 305 (57.8%) at pediatrics, from 181 (34.2%) at adults and from 42 (8%) at neonates wards. The highest antibiotics activities against gram positive isolates observed for vancomycin (98.4%), chloramphenicol (86.4%) and ciprofloxacin (77.4%), while in gram negative bacteria imipenem (96.1%), ciprofloxacin (83%) and amikacin (77.9%), were effective antibiotics. Frequency of isolated bacteria at pediatrics compared to adults and neonates wards were approximately two and seven folds high, respectively which indicates special attention should be paid to pediatrics patients both in prevention and treatment aspects. Vancomycin and imipenim are the effective antibiotics and could cover majority of gram positive and negative bacteria. Therefore, combined administrations of these antibiotics seems mandatory for empirical therapy.

Brucella isolated in humans and animals in Latin America from 1968 to 2006

We report a retrospective analysis of 1933 Brucella strains isolated from humans and animals in Latin American countries between 1968 and 1991 and in Argentina between 1994 and 2006. During the first period 50% of strains were from humans, mainly from Argentina, Mexico and Peru but, while B. suis was the main cause of infection in Argentina, B. melitensis was responsible for most infections in the other countries. In Argentina in the later years, B. melitensis and B. suis were observed more frequently than in the first period while isolation of B. abortus decreased. Of 145 B. melitensis human isolates, eight gave susceptibility patterns to dyes and penicillin and two were B. melitensis biovar 3, which has never been reported in animals. Forty-six percent of B. suis isolated were resistant to dyes which is an atypical feature in this species.

Comparison of the BACTEC blood culture system versus conventional methods for culture of normally sterile body fluids

This study compared the BACTEC blood culture system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md) with conventional culture methods for recovery and time to detection of significant isolates from normally sterile body fluids. A total of 412 specimens were included in the study. Half of the specimens were inoculated directly into the automated blood culture system. The remaining specimens were centrifuged at 3000 rpm for 10 min and were inoculated onto conventional media. Clinically significant microorganisms were isolated from 41 specimens (10%) by both culture systems; however, for 62 specimens (14.9%), growth was detected only with the BACTEC system. No isolates were detected with only conventional culture methods. A significant difference was noted between the blood culture system and routine culture methods for recovery of pathogenic microorganisms that were from sterile body fluids. The most frequently isolated microorganisms recovered only with the blood culture system were gram-positive cocci; gram-negative bacilli were the most frequently isolated microorganisms that were recovered with both culture methods. Streptococcus pneumoniae, Streptococcus viridans, Aeromonas hydrophila, and Brucella were recovered only with the blood culture system. Furthermore, the mean time to detection of significant pathogens was significantly less with the blood culture system than with conventional media. The BACTEC blood culture system was found to improve the yield of clinically significant isolates from normally sterile body fluids with reduced time to detection; it may be advantageous for isolation of fastidious microorganisms, such as Brucella and S pneumoniae, especially from cerebrospinal and synovial fluid specimens.

[Improving the diagnosis of septic arthritis by use of a pediatric blood culture system]

BACKGROUND

Prognosis and outcome of bacterial joint infections are dependent on the fast and reliable identification of pathogens in the synovial fluid. Previous studies have suggested the possible advantage of using a blood culture system in contrast to conventional culture methods.

PATIENTS AND METHODS

A total of 101 synovial specimens from patients presenting with symptoms suggesting septic arthritis were taken by aspiration with a sterile syringe. We compared the diagnostic results of automated analysis in a blood culture system against conventional culture on solid agar plates.

RESULTS

Some 67 specimens (66.3%) were found to be negative in both preparations, while samples from 21 patients (20.8%) yielded the same microorganisms. In 13 cases (12.9%), the isolation of a pathogen was possible only with the blood culture method, whereas the conventional method never yielded a positive result when the blood culture was negative. Thus, the diagnostic yield was significantly improved by use of the blood culture system (P <0.001).

CONCLUSION

The use of a commonly available blood culture system offers a fast, reliable and cost-effective approach for the diagnosis of septic arthritis and should therefore be considered as an useful alternative to conventional culture methods.

Evaluation of the Bactec microbial detection system for culturing miscellaneous sterile body fluids

This study sought to evaluate the efficacy of the Bactec blood culture system for culturing sterile body fluids, in comparison with traditional culture methods. A total of 906 specimens were cultured using both conventional media and the Bactec detection system. Differences in numbers of isolates determined by each system were compared. Clinically significant microorganisms were isolated from 15.3% (139) of 906 specimens by both the Bactec system and conventional culture, whereas for 8.8% (80) of the specimens a positive culture was obtained by Bactec only. Of the 80 specimens in which growth was detected only in the Bactec blood culture system, 11.0% were comprised of cerebrospinal fluid, 9.9% peritoneal fluid, 4.9% pleural fluid, 4.5% synovial fluid and 9.1% bone marrow materials. Strains of Brucella melitensis, Neisseria meningitidis, Pseudomonas fluorescens and Rothia dentocariosa were cultured only by the Bactec system. In conclusion, the Bactec blood culture system might be advantageous for isolation of fastidious microorganisms such as Brucella, especially from cerebrospinal and peritoneal fluid specimens.

A case of brucellar septic arthritis of the knee with a prolonged clinical course

Brucellosis is a systemic infectious disease with a broad spectrum of clinical manifestations. Arthritis is frequently observed in its course and may be one of the main presenting clinical features of the disease. We report a case of brucellar monoarthritis of the knee with a prolonged clinical course despite efficient antibiotic treatment.

Optimum detection times for bacteria and yeast species with the BACTEC 9120 aerobic blood culture system: evaluation for a 5-year period in a Turkish university hospital

We tracked and documented the time of positivity of blood cultures by using the BACTEC 9120 (Becton Dickinson Diagnostic Instrument Systems) blood culture system over a 5-year study period. A 7-day protocol of the incubation period was selected, and a total of 11156 blood cultures were evaluated. The clinically significant microorganisms (32.95%) were isolated in 3676 specimens. Gram-positive and -negative bacterial isolation rates were found to be 41.07 and 44.88%, respectively. Yeasts were found in 14.03% of all pathogens. Both the false-positivity and -negativity rates were very low (0.1 and 0.3%, respectively). The mean detection times for all of the pathogens were determined to be 19.45 h. Yeasts, nonfermentative gram-negative bacteria, and Brucella melitensis strains were isolated within 5 days. By taking these data into account, we decided to establish a 5-day-incubation protocol in our laboratory instead of the 7 days that are commonly used.

Use of simulated blood cultures for time to detection comparison between BacT/ALERT and BACTEC 9240 blood culture systems

In order to avoid the influence of pre-analytical steps, the following study was performed by using sterile blood spiked with defined loads of microorganisms as inoculum. Time-to-Detection (TTD) was evaluated for the most frequently encountered bacteria and fungi in septicemia, comparing two commercially available blood culture systems, BACTEC 9240 (Becton Dickinson) and BacT/ALERT (Organon Teknika). A specific medium, Bactec Mycosis IC/F (Becton Dickinson), was compared with the Bactec Plus Aerobic (Becton Dickinson) and FAN Aerobic (Organon Teknika) media for recovery of fungi in general and in case of mixed bacterial/fungal septicemia. The results show that the BACTEC system detects nearly all enrolled microorganisms significantly faster than the BacT/ALERT; the anaerobic vial contributes to the detection of anaerobes and facultative anaerobes and, in the case of BACTEC, shortens TTD; the Bactec Mycosis IC/F bottle shortens TTD of fungi.