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

The Development of Diagnostic and Vaccine Strategies for Early Detection and Control of Human Brucellosis, Particularly in Endemic Areas

Brucellosis is considered one of the most serious zoonotic diseases worldwide. This disease affects both human and animal health, in addition to being one of the most widespread zoonotic illnesses in the Middle East and Northern Africa. Human brucellosis generally presents in a diverse and non-specific manner, making laboratory confirmation of the diagnosis critical to the patient’s recovery. A coordinated strategy for diagnosing and controlling brucellosis throughout the Middle East is required, as this disease cannot be known to occur without reliable microbiological, molecular, and epidemiological evidence. Consequently, the current review focuses on the current and emerging microbiological diagnostic tools for the early detection and control of human brucellosis. Laboratory assays such as culturing, serology, and molecular analysis can frequently be used to diagnose brucellosis. Although serological markers and nucleic acid amplification techniques are extremely sensitive, and extensive experience has been gained with these techniques in the laboratory diagnosis of brucellosis, a culture is still considered to be the “gold standard” due to the importance of this aspect of public health and clinical care. In endemic regions, however, serological tests remain the primary method of diagnosis due to their low cost, user-friendliness, and strong ability to provide a negative prediction, so they are commonly used. A nucleic acid amplification assay, which is highly sensitive, specific, and safe, is capable of enabling rapid disease diagnosis. Patients who have reportedly fully healed may continue to have positive molecular test results for a long time. Therefore, cultures and serological methods will continue to be the main tools for diagnosing and following up on human brucellosis for as long as no commercial tests or studies demonstrate adequate interlaboratory reproducibility. As there is no approved vaccine that prevents human brucellosis, vaccination-based control of animal brucellosis has become an important part of the management of human brucellosis. Over the past few decades, several studies have been conducted to develop Brucella vaccines, but the problem of controlling brucellosis in both humans and animals remains challenging. Therefore, this review also aims to present an updated overview of the different types of brucellosis vaccines that are currently available.

Microbiological Laboratory Diagnosis of Human Brucellosis: An Overview

Brucella spp. are Gram-negative, non-motile, non-spore-forming, slow-growing, facultative intracellular bacteria causing brucellosis. Brucellosis is an endemic of specific geographic areas and, although underreported, represents the most common zoonotic infection, with an annual global incidence of 500,000 cases among humans. Humans represent an occasional host where the infection is mainly caused by B. melitensis, which is the most virulent; B. abortus; B. suis; and B. canis. A microbiological analysis is crucial to identifying human cases because clinical symptoms of human brucellosis are variable and aspecific. The laboratory diagnosis is based on three different microbiological approaches: (i) direct diagnosis by culture, (ii) indirect diagnosis by serological tests, and (iii) direct rapid diagnosis by molecular PCR-based methods. Despite the established experience with serological tests and highly sensitive nucleic acid amplification tests (NAATs), a culture is still considered the “gold standard” in the laboratory diagnosis of brucellosis due to its clinical and epidemiological relevance. Moreover, the automated BC systems now available have increased the sensitivity of BCs and shortened the time to detection of Brucella species. The main limitations of serological tests are the lack of common interpretative criteria, the suboptimal specificity due to interspecies cross-reactivity, and the low sensitivity during the early stage of disease. Despite that, serological tests remain the main diagnostic tool, especially in endemic areas because they are inexpensive, user friendly, and have high negative predictive value. Promising serological tests based on new synthetic antigens have been recently developed together with novel point-of-care tests without the need for dedicated equipment and expertise. NAATs are rapid tests that can help diagnose brucellosis in a few hours with high sensitivity and specificity. Nevertheless, the interpretation of NAAT-positive results requires attention because it may not necessarily indicate an active infection but rather a low bacterial inoculum, DNA from dead bacteria, or a patient that has recovered. Refined NAATs should be developed, and their performances should be compared with those of commercial and home-made molecular tests before being commercialized for the diagnosis of brucellosis. Here, we review and report the most common and updated microbiological diagnostic methods currently available for the laboratory diagnosis of brucellosis.

Using a One Health Case-Based Investigation for Improved Control of Brucellosis in Isiolo, Kenya

Brucella is a highly pathogenic bacteria endemic in Kenya, and in spite of its severity in humans, the highly inadequate Febrile Antigen Brucella Agglutination Test (FBAT) remains a primary tool for its diagnosis. Blood samples were collected from febrile patients in Kinna health center and screened by the local routine. Milk samples were purchased from local milk hawkers and analyzed for Brucella antibodies using the milk ring test (MRT). The MRT-positive milk was traced to farms, and lactating cattle were sampled for milk and blood. Milk was MRT-tested and the serum was analyzed using the Rose Bengal test (RBT) and iELISA. Available patient and farm samples were stored on FTA cards for qPCR analyses. Despite a limited sample size, our study, in line with previous reports, shows a low diagnostic sensitivity (67%) and specificity (40%) of FBAT when compared to qPCR. As many as 48% of the raw bulk cattle milk samples were MRT-positive for Brucella antibodies and 60% of cattle on three visited farms were IS711 qPCR-positive. This case-based One Health investigation confirms the suspected Brucella presence, suggesting a targeted vaccination at high-prevalence farms, urgent interventions on milk safety, and a re-evaluation of the diagnostic and treatment regimen.

Atypical Presentation of Neurobrucellosis as Infection of Ventriculoperitoneal Shunt

Brucellosis is a frequent zoonosis in some regions of the world and may cause various symptoms. Neurobrucellosis is a rare but serious complication of the infection. Our case report describes the course of neurobrucellosis in a patient who had received a ventriculoperitoneal shunt in his native country 13 years prior to diagnosis of brucellosis. He initially presented to us with symptoms of peritonitis, which misled us to perform abdominal surgery first. After the diagnosis of neurobrucellosis was confirmed and appropriate antibiotics were initiated, the symptoms soon disappeared. Although the ventriculoperitoneal shunt was subsequently removed, the patient did not develop a symptomatic hydrocephalus further on. This case displays the challenges in diagnosing an infection that occurred sporadically in Europe and may be missed by currently applied routine microbiological workup. Considering the political context, with increasing relocation from endemic areas to European countries, it is to be expected that the cases of brucellosis and neurobrucellosis will rise. Brucellosis should be considered and adequate investigations should be performed.

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.

Isolation rates of Brucella melitensis in an endemic area and implications for laboratory safety

A retrospective study was conducted to assess the potential threat posed by processing blood cultures to clinical microbiology laboratory personnel working in an area endemic for Brucella melitensis in southern Israel. The computerized laboratory records for the 2002-2009 period were reviewed, and the proportion of aerobic vials from which Brucella organisms were isolated out of the total number of positive aerobic blood culture vials was determined. During the 8-year period, B. melitensis was isolated in 514 of 20,620 (2.5%) positive vials. Isolation rate increased at the end of the period reaching a peak of 5.3% in 2008. Between April 2008 and September 2009, the proportion of aerobic blood cultures from which B. melitensis was isolated was even higher than that positive for pneumococci (4.3% and 2.6%, respectively, P < 0.001). Although it has been recommended that processing of Brucella cultures should be confined to a Class II biologic safety cabinet, by the time the organism is identified, extensive manipulation of culture media has already been performed and inadvertent exposure of laboratory personnel may have already occurred. To reduce the risk of transmission, all positive blood culture vials in endemic areas should be processed in a safety cabinet.

Identification of Brucella by MALDI-TOF mass spectrometry. Fast and reliable identification from agar plates and blood cultures

BACKGROUND

MALDI-TOF mass spectrometry (MS) is a reliable method for bacteria identification. Some databases used for this purpose lack reference profiles for Brucella species, which is still an important pathogen in wide areas around the world. We report the creation of profiles for MALDI-TOF Biotyper 2.0 database (Bruker Daltonics, Germany) and their usefulness for identifying brucellae from culture plates and blood cultures.

METHODOLOGY/PRINCIPAL FINDINGS

We created MALDI Biotyper 2.0 profiles for type strains belonging to B. melitensis biotypes 1, 2 and 3; B. abortus biotypes 1, 2, 5 and 9; B. suis, B. canis, B ceti and B. pinnipedialis. Then, 131 clinical isolates grown on plate cultures were used in triplicate to check identification. Identification at genus level was always correct, although in most cases the three replicates reported different identification at species level. Simulated blood cultures were performed with type strains belonging to the main human pathogenic species (B. melitensis, B. abortus, B. suis and B. canis), and studied by MALDI-TOF MS in triplicate. Identification at genus level was always correct.

CONCLUSIONS/SIGNIFICANCE

MALDI-TOF MS is reliable for Brucella identification to the genus level from culture plates and directly from blood culture bottles.

Evaluation of different PCR assays for early detection of acute and relapsing brucellosis in humans in comparison with conventional methods

Human brucellosis is a significant public health problem in many Mediterranean countries including Greece. The conventional serological methods, as well as blood cultures, have serious limitations, especially in chronic, relapsing, and focal forms of the disease. Four different PCR assays were applied in 4,926 buffy coat, whole-blood, and serum samples received from 200 patients admitted with brucellosis to the Infectious Diseases Hospital, Thessaloniki, Greece, for the rapid diagnosis of acute infection and relapses and compared to blood culture and serological tests (i.e., Wright's seroagglutination test, Coombs' antibrucella test, and the complement fixation test). The four PCR assays had excellent sensitivity and specificity and were able to detect all of the cases of acute disease. Buffy coat and whole blood were the optimal specimens. All four PCR assays were negative in all follow-up samples from 183 patients who had completed a successful treatment and were positive in all follow-up samples from 17 patients who had relapses in the first year after therapy, including the times of the relapses. In conclusion, PCR is a very useful tool for the rapid diagnosis of acute brucellosis and a good marker for the posttreatment follow-up and the early detection of relapses.

Fungi, mycobacteria, zoonotic and other organisms in prosthetic joint infection

A systematic review of the presentation and management of prosthetic joint infection (PJI) due to zoonotic microorganisms, fungi, mycobacteria and other unusual microorganisms is not available. We therefore sought to provide a resource for the practicing orthopaedic surgeon which will serve as a guide for making appropriate decisions in managing such rare, but potentially problematic conditions. We conducted a Medline search of all case reports of PJI due to these unusual microorganisms. Our review of the current literature showed the diagnosis of PJI due to zoonotic microorganisms, fungi, mycobacteria and other unusual microorganisms typically necessitates specialized diagnostic tests. Maintaining a high index of suspicion in diagnosis of such unusual microorganisms and requesting the appropriate laboratory tests at the time of surgical débridement is crucial for determining the microbiologic etiology of these infections. The appropriate medical and surgical management of such infections is complex and often requires the use of special antimicrobials with which the orthopaedist may not be familiar. Collaboration with an infectious disease specialist is advisable when treating these infections.

Laboratory exposures to brucellae and implications for bioterrorism

Brucellae are class 3 organisms and potential agents of bioterrorism. Because of effective public health measures, brucellosis has become a rare disease in industrialized countries, and clinical microbiology laboratories are frequently unfamiliar with the genus. A low index of suspicion by physicians or failure to notify the laboratory, equivocal Gram-stain results, misidentification of the organism by commercial systems, unsafe laboratory practices, and laboratory accidents have been responsible for numerous cases of exposure to the organism and laboratory-acquired disease in recent years. Discovery of a laboratory exposure to brucellae should prompt an exhaustive investigation of the event and its circumstances, definition of the population at risk, enforcement of safe laboratory practices, and antimicrobial drug prophylaxis for exposed persons. Inadvertent exposures to brucellae in the clinical laboratory indicate a widespread lack of preparedness to cope with eventual biologic threats involving use of the organism.

Brucellosis in San Diego: epidemiology and species-related differences in acute clinical presentations

Although aggressive public health measures have greatly reduced the number of brucellosis cases in the United States, there is a resurgence of interest in this worldwide zoonosis because of its potential as a bioweapon and its 8-fold higher incidence in California, Texas, and the other borderlands between the United States and Mexico compared with the national rate. Accordingly, we reviewed the clinical records of 28 patients diagnosed at a university hospital in San Diego, CA, between 1979 and 2002 to look for new epidemiologic trends and to test the hypothesis that there are species-specific differences in clinical presentations. In contrast to the latest California-wide study completed in 1992, Brucella abortus infections were more common (73%) than Brucella melitensis after 1992, and women were more commonly infected (77% compared with 39%) than men. Major risk factors remained Hispanic ethnicity, travel to Mexico, and ingestion of nonpasteurized dairy products. Analysis of diagnostic procedures suggested that the traditional practice of prolonged incubation of blood cultures increased their sensitivity for Brucella, even in automated radiometric systems. Direct comparison of the clinical manifestations of infections with B. abortus and B. melitensis strongly supported differences in acute presentations. B. melitensis presented more acutely as fevers of unknown origin with statistically significant higher rates of abdominal tenderness, hepatomegaly, splenomegaly, thrombocytopenia, pancytopenia, and hepatic dysfunction. These results suggest that the epidemiology of brucellosis in California may be evolving, and they show, to our knowledge for the first time in a single series, that species-specific differences in presentations may account for some of the protean manifestations of brucellosis. Familiarity with manifestations of brucellosis and the optimal laboratory techniques for its diagnosis could help physicians protect the public against this reemerging, under-recognized zoonosis.

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).

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.

Detection of Brucella melitensis by the BacT/Alert automated system and Brucella broth culture

This study was conducted to evaluate the ability of the BacT/Alert automated blood culture system to detect Brucella spp. in comparison with traditional Brucella broth culture. Overall, 100 (50 bone marrow and 50 blood samples) paired cultures were obtained, and 59 were positive by at least one method. The Brucella broth culture method detected all 59 positive cultures (100%), and the BacT/Alert system detected 30 (50.8%) (P < 0.05). The mean detection times for B. melitensis were 4.5 days in the BacT/Alert system and 5 days in Brucella broth culture (P > 0.05). There is no significant difference between the two methods with respect to growth time of the microorganism, but Brucella broth culture is more sensitive than the BacT/Alert system.

The diagnosis of brucellosis by use of BACTEC 9240 blood culture system

The diagnosis of brucellosis is generally made when a standard tube agglutination titer of 1/160 or more for anti-Brucella antibodies in the presence of compatible clinical signs and symptoms. However isolation of the organism from blood or bone marrow is the proof of the disease. In this study we aimed to describe the rate and duration of isolation of Brucella spp. from blood and bone marrow by use of automated blood culture system (BACTEC 9240). Between 1997 to 2001, 23 adults were diagnosed as brucellosis. Blood culture was obtained in all and simultaneous bone marrow culture in 18 and both specimens were cultured by BACTEC 9240. Brucella was isolated from blood and bone marrow cultures in 19 (82.6%) and 13 (81.2%) respectively. All positive blood cultures yielded within 7 days and bone marrow cultures in 4 days. We concluded that automated BACTEC culture systems can isolate Brucella spp. in a fast and efficient way.

Bacterial pathogens as biological weapons and agents of bioterrorism

Bacterial pathogens have been identified as agents that have been, or could be, used as weapons of biological warfare and/or biological terrorism. These agents are relatively easily obtained, prepared, and dispersed, either as weapons of mass destruction or for more limited terrorist attacks. Although phylogenetically diverse, these agents all have the potential for aerosol dissemination. Physicians in the United States and most of the developed world have never encountered most of these agents and the diseases they produce. Public health programs must be prepared, and individual primary care providers must be able to recognize, diagnose, treat, and prevent infection with these agents.

[Osteoarticular brucellosis and signs of autoimmunity]

We report two cases of osteoarticular brucellosis in childhood, which illustrate the diagnostic difficulties in non-endemic areas.

CASE REPORT

A 12-year-old boy was admitted for a unilateral sacroiliitis for which the brucellosis origin was established by serological and blood cultures (without fever). Autoimmunity was detected and disappeared following the treatment of the affection. A six-year-old girl was admitted for a monoarthritis of the left ankle (with fever) for which the brucellosis origin was also established by serology and blood cultures.

COMMENTS

The above cases underline the importance of knowing the atypical varieties of brucellosis. The brucellosis serologies need to take part in the etiological workup of an infectious osteoarthritis when a classic infectious cause cannot be proved. Blood cultures on a specific medium are essential to carry out, even in the case of apyrexia. Finally, the possibility of autoimmunity signs for the brucellosis has to be known to avoid orientating the diagnosis towards an autoimmune systemic disease.

Brucella detection in blood: comparison of the BacT/Alert standard aerobic bottle, BacT/Alert FAN aerobic bottle and BacT/Alert enhanced FAN aerobic bottle in simulated blood culture

The objective of this study was to compare the performances of the standard aerobic bottle (StAe), FAN aerobic (FANAe) and enhanced FAN aerobic (E-FANAe) (the charcoal component of the FANAe was revised recently to improve the feasibility of Gram smear interpretation) blood culture bottles for BacT/Alert system for the detection of Brucella melitensis in simulated blood culture. Triplicate strains of eight clinical isolates of B. melitensis were studied. Each bottle was inoculated with 5 mL of freshly collected human blood at three different targeted bacterial inocula (10(1), 10(2) and 10(3) CFU/bottle). All bottles were monitored for up to 21 days or until they became positive. The results of time to detection (TTD) on the eight B. melitensis samples were as follows: at 10(1) CFU/bottle, the E-FANAe had a mean TTD significantly shorter than the StAe (48 h vs. 56.2 h, P < 0.05); and at 10(3) CFU/bottle, the FANAe and E-FANAe had a mean TTD significantly shorter than the StAe (41.2 h and 40 h vs. 45.6 h, P < 0.05). The reproducibilities (no.of positive signals/no.of all bottles) of three bottle systems were as follows: at 10(1) CFU/bottle, the reproducibilities of StAe, FANAe and E-FANAe were 96, 83 and 58%, respectively. At 10(3) CFU/bottle, the reproducibilities of StAe, FANAe and E-FANAe were 95, 95 and 91%, respectively. Positive results for the presence of bacteria in Gram smears were confirmed in 68% of StAe, 54% of FANAe and 90% of E-FANAe. In case of suspected brucellosis, the combination of one StAe bottle and one E-FANAe bottle seems to provide the highest and fastest recovery of the organism.

Zoonotic infections as causes of hospitalization among febrile Bedouin patients in southern Israel

A prospective 12-month study was conducted throughout 1998 to determine the frequency of selected bacterial zoonoses as causes of fever among hospitalized Bedouins in southern Israel. One or more zoonoses were diagnosed in 30 (27%) of 110 patients admitted with fever. Brucellosis was diagnosed in 9 (8%), rickettsial infections in 20 (18%), and ehrlichiosis in 2 (2%), one of whom had also evidence of rickettsial spotted fever infection. None of the patients was diagnosed with Q fever. Compared with patients without zoonoses, patients with zoonoses were younger (P = 0.01), fewer of them had underlying conditions (P < 0.02), they had a longer febrile period prior to hospitalization (P = 0.04), a significantly higher proportion had arthralgia (P = 0.02), rash (P = 0.03), and splenomegaly (P = 0.04) and a lower proportion had pathological findings on chest auscultation (P < 0.01). Patients with zoonoses were found to have more commonly anaemia (P = 0.03) and leucopenia (P = 0.02) compared to the rest of the study population. Of the 30 patients with zoonoses 60% were misdiagnosed and only 57% received adequate antibiotic treatment. Zoonotic infections are a common cause of fever in adult Bedouins living in southern Israel. Because of the non-specific features of these diseases they are often misdiagnosed. Blood cultures and multiple serological tests should be used in the investigation of fever in such patients and tetracycline should be considered for initial empirical treatment.

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

Synovial fluid specimens aspirated from patients with arthritis were inoculated into an aerobic Peds Plus blood culture bottle and monitored by the BACTEC 9240 instrument for 4 weeks. A total of 1,072 synovial fluid cultures were processed, and 15 (0.14%) were positive for Brucella melitensis. A single culture, harboring 1.3 CFU of viable organisms per ml, was missed by the instrument. All 14 positive BACTEC cultures were detected within 3 to 7 days.

Detection of selected fastidious bacteria

The intent of this article is to describe the optimal methods for culture recovery of 7 fastidious bacteria: Legionella species, Brucella species, Francisella tularensis, Leptospira species, Borrelia burgdorferi, Bartonella species, and Bordetella species. These organisms share much in common beyond the fact that their genus names all end in the letter "a." Culture recovery of these organisms, even from adequate clinical specimens, is logistically demanding, often costly, and lacking in both timeliness and sensitivity. In addition, there is generally no need to recover culture isolates on which to perform antimicrobial susceptibility tests because these 7 bacteria are nearly uniformly susceptible to specific, clinically useful antimicrobial agents and because, for some of them, susceptibility tests of proven reliability have not yet been devised. Perhaps for these reasons, alternative, more rapid, direct diagnostic approaches have been developed that are based on either immunochemical or nucleic-acid detection methods. These methods have generally served to supplant culture as a primary diagnostic modality. Situations exist, however, in which culture may be desirable, if not necessary, to establish a definitive diagnosis of infection with these 7 organisms. This review attempts to summarize how best to proceed in those cases.

Rapid diagnosis of Brucella bacteremia by using the BACTEC 9240 system

Almost 93% of 97 separate patient isolates of Brucella bloodstream infections were recovered within 5 days of incubation by using the BACTEC 9240 continuous-monitoring blood culturing system.