Comparison of the Bactec and lysis concentration methods for recovery of Brucella species from clinical specimens

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.

Microbiological laboratory diagnostics of neglected zoonotic diseases (NZDs)

This review reports on laboratory diagnostic approaches for selected, highly pathogenic neglected zoonotic diseases, i.e. anthrax, bovine tuberculosis, brucellosis, echinococcosis, leishmaniasis, rabies, Taenia solium-associated diseases (neuro-/cysticercosis & taeniasis) and trypanosomiasis. Diagnostic options, including microscopy, culture, matrix-assisted laser-desorption-ionisation time-of-flight mass spectrometry, molecular approaches and serology are introduced. These procedures are critically discussed regarding their diagnostic reliability and state of evaluation. For rare diseases reliable evaluation data are scarce due to the rarity of samples. If bio-safety level 3 is required for cultural growth, but such high standards of laboratory infrastructure are not available, serological and molecular approaches from inactivated sample material might be alternatives. Multiple subsequent testing using various test platforms in a stepwise approach may improve sensitivity and specificity. Cheap and easy to use tests, usually called "rapid diagnostic tests" (RDTs) may impact disease control measures, but should not preclude developing countries from state of the art diagnostics.

Factors affecting Brucella spp. blood cultures positivity in children

Brucella infections have a wide spectrum of symptoms especially in children, making the diagnosis a complicated process. The gold standard for the final diagnosis for brucellosis is to identify the Brucella spp. isolated from blood or bone marrow cultures. The main purpose of this work was to evaluate the factors affecting the isolation of Brucella spp. from blood cultures. In our study, the ratio of fever, presence of hepatomegaly, and splenomegaly were found to be higher in the bacteremic group. In addition, C-reactive protein levels and liver function enzymes were found to be higher in the bacteremic group. In our opinion, while evaluating the febrile child with suspected Brucella infection, we highly recommend sampling blood cultures regardless of the history of previous antimicrobial therapy and duration of the symptoms.

Use of the BACTEC MYCO/F LYTIC medium for detection of Brucella melitensis bacteremia

In a prospective volume-controlled study, the sensitivity of the BACTEC MYCO/F LYTIC medium was similar to that of the Peds Plus/F and Plus Aerobic/F vials for detecting Brucella melitensis bacteremia, but the time to detection with the MYCO/F LYTIC medium (101.4 +/- 46.7 h) was significantly longer than that with the combined comparator media (65.5 +/- 18.9 h, P = 0.004).

Endocarditis due to rare and fastidious bacteria

The etiologic diagnosis of infective endocarditis is easily made in the presence of continuous bacteremia with gram-positive cocci. However, the blood culture may contain a bacterium rarely associated with endocarditis, such as Lactobacillus spp., Klebsiella spp., or nontoxigenic Corynebacterium, Salmonella, Gemella, Campylobacter, Aeromonas, Yersinia, Nocardia, Pasteurella, Listeria, or Erysipelothrix spp., that requires further investigation to establish the relationship with endocarditis, or the blood culture may be uninformative despite a supportive clinical evaluation. In the latter case, the etiologic agents are either fastidious extracellular or intracellular bacteria. Fastidious extracellular bacteria such as Abiotrophia, HACEK group bacteria, Clostridium, Brucella, Legionella, Mycobacterium, and Bartonella spp. need supplemented media, prolonged incubation time, and special culture conditions. Intracellular bacteria such as Coxiella burnetii cannot be isolated routinely. The two most prevalent etiologic agents of culture-negative endocarditis are C. burnetti and Bartonella spp. Their diagnosis is usually carried out serologically. A systemic pathologic examination of excised heart valves including periodic acid-Schiff (PAS) staining and molecular methods has allowed the identification of Whipple's bacillus endocarditis. Pathologic examination of the valve using special staining, such as Warthin-Starry, Gimenez, and PAS, and broad-spectrum PCR should be performed systematically when no etiologic diagnosis is evident through routine laboratory evaluation.

Rapid detection of Brucella melitensis from blood cultures by a commercial system

To assess the capability of the Peds Plus medium of the Bactec 9240 blood culture system to recover Brucella melitensis within the routine seven-day protocol used by most clinical microbiology laboratories, inoculated blood culture bottles were monitored by the Bactec 9240 instrument for four weeks, and blind subcultures were performed once a week. A total of 2579 blood cultures were drawn, 42 (1.6%) of which were positive for Brucella melitensis. Forty-one of the 42 (97.6%) positive cultures were detected by the Bactec 9240 instrument within two to six days; a single positive culture was missed by the instrument and detected by blind subculture performed on day 7.

Update on detection of bacteremia and fungemia

The presence of microorganisms in a patient's blood is a critical determinant of the severity of the patient's illness. Equally important, the laboratory isolation and identification of a microorganism present in blood determine the etiologic agent of infection, especially when the site of infection is localized and difficult to access. This review addresses the pathophysiology and clinical characteristics of bacteremia, fungemia, and sepsis; diagnostic strategies and critical factors in the detection of positive blood cultures; characteristics of manual and instrument approaches to bacteremia detection; approaches for isolating specific microorganisms associated with positive blood cultures; and rapid methods for the identification of microorganisms in blood cultures.

Comparison of BACTEC 9240 Peds Plus medium and isolator 1.5 microbial tube for detection of Brucella melitensis from blood cultures

The sensitivity and time to detection of Brucella melitensis by the BACTEC 9240 and the Isolator blood culture systems were compared in a prospective volume-controlled study. Blood sample aliquots, obtained from children with suspected brucellosis, were inoculated into a BACTEC 9240 Peds Plus bottle and into an Isolator 1.5 Microbial Tube. Overall, 122 pairs of blood samples for culture were obtained, and 28 (23%) were positive by at least one method. The BACTEC 9240 system detected all 28 positive cultures (sensitivity, 100%), and the Isolator system detected 22 positive cultures (sensitivity, 79%) (P = 0.023). Among those 22 cultures positive by both methods, 21 (95%) and 15 (68%) were found to be positive within 3 days by the BACTEC and the Isolator systems, respectively; 8 (36%) were found to be positive at least 1 day earlier by the BACTEC instrument, and the remaining 14 were found to be positive by the two systems on the same day (P = 0.045). The BACTEC 9240 blood culture system is more sensitive than the Isolator system for the detection of B. melitensis and is superior in terms of time to detection of the organism.

Brucellosis: an overview

Brucellosis remains a major zoonosis worldwide. Although many countries have eradicated Brucella abortus from cattle, in some areas Brucella melitensis has emerged as a cause of infection in this species as well as in sheep and goats. Despite vaccination campaigns with the Rev 1 strain, B. melitensis remains the principal cause of human brucellosis. Brucella suis is also emerging as an agent of infection in cattle, thus extending its opportunities to infect humans. The recent isolation of distinctive strains of Brucella from marine mammals has extended its ecologic range. Molecular genetic studies have demonstrated phylogenetic affiliation to Agrobacterium, Phyllobacterium, Ochrobactrum, and Rhizobium. Polymerase chain reaction and gene probe development may provide more effective typing methods. Pathogenicity is related to production of lipopolysaccharides containing a poly N-formyl perosamine O chain, CuZn superoxide dismutase, erythrlose phosphate dehydrogenase, stress-induced proteins related to intracellular survival, and adenine and guanine monophosphate inhibitors of phagocyte functions. Protective immunity is conferred by antibody to lipopolysaccharide and T-cell-mediated macrophage activation triggered by protein antigens. Diagnosis still centers on isolation of the organism and serologic test results, especially enzyme immunoassay, which is replacing other methods. Polymerase chain reaction is also under evaluation. Therapy is based on tetracyclines with or without rifampicin, aminoglycosides, or quinolones. No satisfactory vaccines against human brucellosis are available, although attenuated purE mutants appear promising.

Childhood brucellosis in Israel

BACKGROUND

Brucellosis has become a major medical problem in Israel particularly in the Muslim Arab population.

METHODS

Eighty-eight children with acute brucellosis are described. Sixty-seven were studied retrospectively during 1987 through 1988, and 21 children were studied prospectively during 1989 through 1992. Epidemiologic, clinical and laboratory features were evaluated, and the outcome of 4 antimicrobial regimens are compared.

RESULTS

Although the clinical manifestation varied, the classical triad of fever (91%), arthralgia or arthritis (83%) and hepato- and/or splenomegaly (63%) characterized most patients. Sixty-one percent of the children had elevated liver enzymes. Brucella melitensis was isolated from 61% of blood cultures. The relapse rate in patients who were treated with monotherapy (doxycycline) was 43% compared with 14% with regimens of combined therapy with rifampin and doxycycline, streptomycin and doxycycline or rifampin and trimethoprim-sulfamethoxazole (P < 0.049). Eleven children (33%) who were treated for 3 weeks had relapse compared with 1 patient (3.5%) treated for 4 weeks or longer. The total relapse or reinfection rate was 20%. All patients with relapse recovered after a second course of antibiotic therapy. During the 2 years of follow-up one child progressed to chronic osteomyelitis.

CONCLUSIONS

Combination therapy and extending treatment for 4 weeks or longer gave significantly better results than monotherapy or shorter courses of therapy and resulted in fewer relapses.

Synovial fluid L-lactic acid in acute arthritis of the adult knee joint

Determination of synovial fluid (SF) lactic acid has been suggested to be an unspecific indicator of SF leukocytosis, and it is not recommended for differential diagnosis of bacterial arthritis. We analyzed the L-lactic acid content by enzymatic UV-method in 65 SF samples obtained from adult patients with acute knee arthritides. The concentration of L-lactic acid was not high in any SFs with intensive leukocytosis. The mean concentration of L-lactic acid was 13.5 mmol/l (95% confidence intervals 9.4; 17.6 mmol/l) in the synovial-fluid samples from culture-positive arthritis and 5.5 mmol/l (4.9; 6.2 mmol/l) in the synovial-fluid samples from culture-negative arthritis. Determination of SF L-lactic acid is an important part of the diagnostic setup for acute arthritis. Values > 9 mmol/l strongly support occurrence of bacterial arthritis and indicates an immediate onset of the treatment.

Detection of Brucella melitensis by BACTEC NR660 blood culture system

Data on the performance of modern blood culture systems for the detection of Brucella spp. are insufficient. To evaluate the performance of the BACTEC NR660 blood culture system for the detection of Brucella melitensis within the routine 1-week blood culture protocol, a prospective 24-month study was conducted in an area endemic for B. melitensis in southern Israel. Blood samples obtained from patients with suspected brucellosis were monitored and blindly subcultured once per week for 4 weeks, and the fraction of blood cultures positive for B. melitensis detected by the BACTEC NR660 instrument within the first week was determined. During the study period, a total of 373 blood cultures were obtained from patients in whom brucellosis was suspected, and 27 (7.2%) of them, drawn from 21 different patients, were positive for B. melitensis. Twenty-one (78.8%) of these positive cultures were detected by the BACTEC instrument within 7 days, and six positive cultures were detected by subculture after 2 or 3 weeks of incubation. It is concluded that the BACTEC NR660 blood culture system detects the majority of B. melitensis isolates within the routine 1-week blood culture schedule. To maximize the recovery of the organism, however, prolonged incubation and periodic performance of blind subcultures are still required.

Synovial-fluid D-lactic acid in bacterial and other acute joint effusions

The use of D-lactic acid in differential diagnosis of bacterial arthritis was evaluated in a prospective study. The concentration of D-lactic acid was determined by the enzymatic UV-method in sixty-eight synovial fluids (SF) and in twenty four sera from adult patients with acute knee effusion. High concentrations of D-lactic acid (> 0.15 mmol/l) were measured most frequently in SF from bacterial arthritis, but also in individual culture-negative SF samples from patients with inflammatory culture-negative joint effusions with and without identified history of infections. Determination of SF D-lactic acid is not useful in differential diagnosis of bacterial arthritis.

Group II phospholipase A2 in synovial fluid and serum in acute arthritis

Increased catalytic activity of synovial-type (group II) phospholipase A2 (syn-PLA2), has been associated with cartilage erosions in rheumatoid arthritis and osteoarthritis. The catalytic activity of phospholipase A2 and the concentration of syn-PLA2 were measured in a prospective study in synovial fluid (SF) samples from 66 patients with acute knee joint effusion. The median (range) of the concentration of syn-PLA2 in SF was 210 micrograms/l (80-1480 micrograms/l) in culture-positive septic arthritis, 460 micrograms/l (270-1040 micrograms/l) in reactive arthritis, 780 micrograms/l (120-2710 micrograms/l) in osteoarthritis and 230 micrograms/l (80-1400 micrograms/l) in traumatic joint effusions. High concentrations of syn-PLA2 are found also in SF of patients with arthritides not expected to lead to permanent destruction of cartilage.

Faster isolation of Brucella spp. from blood by isolator compared with BACTEC NR

Brucella spp. was isolated from blood cultures in a mean time of 3.1 days (range, 2-5) in seven cases of human brucellosis processed with the Isolator lysis-centrifugation system. Simultaneous BACTEC NR blood cultures in the same patients were positive in six, with a mean detection time of 20.6 days (range, 17-29). These data suggest a higher speed of recovery of Brucella spp. from blood specimens with the lysis-centrifugation procedure compared with the BACTEC NR system.