Limitations of the standard agglutination test for detecting patients with Brucella melitensis bacteremia

Metagenomic next-generation sequencing for the diagnosis of neurobrucellosis

Objective: This study investigates the application of metagenomic next-generation sequencing (mNGS) in the diagnosis of neurobrucellosis (NB). Methods: We retrospectively analyzed patients diagnosed with NB who underwent cerebrospinal fluid (CSF) mNGS testing in Xijing Hospital from 2015 to 2021. Results: Among the 20 individuals included in the study, the serum rose bengal test was positive in 11 out of 16 cases, serum agglutination test was positive in 13 out of 16 cases, CSF culture was positive in 6 out of 11 cases, and CSF mNGS tests were positive in 18 out of 20 cases. Conclusion: CSF mNGS demonstrates superior sensitivity; therefore, it is recommended to collect CSF for mNGS testing prior to antibiotic therapy when NB is suspected.

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.

Risk Factors for Acute Brucellosis in Patients on the Day of Admission at Selected Hospitals of Abbottabad, Pakistan

Brucellosis is a neglected zoonotic disease of ruminants. It causes severe health problems in humans and significant economic loss. Only a limited number of studies have been conducted in Pakistan to determine the prevalence of human brucellosis and related risk factors. The objectives of the current cross-sectional study were to determine the prevalence of anti-Brucella antibodies in sera collected from symptomatic patients at three hospitals of Abbottabad using a commercial slide agglutination test (SAT) and to determine risk factors for brucellosis for these patients. Five hundred blood samples were collected. A questionnaire was filled in for each patient to obtain information on age, gender, living area, brucellosis associated symptoms, associated risk factors, pregnancy and abortion history. A total of 13.6% (n = 68) patients were found to be SAT positive and in 83.3% (n = 57) of these samples Brucella DNA was detected by genus specific RT-PCR for BCSP-31 gene. Statistical analysis was performed to determine odd ratios, risk ratios, 95% confidence intervals, and p-values. The prevalence of brucellosis by SAT was reported to be higher in women (14.6%, n = 44) than in men (12.1%, n = 24). The age group 25–50 years was found to be at higher risk for brucellosis (14.5%, n = 50) “animal contact” was reported as the main risk factor followed by “consumption of raw animal products.” Out of 131 pregnant women and 21 patients had abortion, the seropositivity of Brucellosis was 9.9% and 23.8%, respectively. The present study reports a striking prevalence of brucellosis among patients including pregnant women at three hospitals of Abbottabad. These findings may foster strategies for controlling human brucellosis at household level, raising of awareness about brucellosis in hospital and family doctors, and finally in setting up an eradication program in the dairy industry.

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.

Clinical and laboratory characteristics of childhood brucellosis in high-risk area of Western China

Childhood brucellosis present various non-specific clinical symptoms, and limited laboratory data exist for clinical diagnosis. A better understanding of these clinical and laboratory characteristics can avoid clinical misdiagnosis and mistreatment. In this case-series study, a total of 78 children with confirmed diagnosis of brucellosis were evaluated retrospectively. We observed that the incidence rate was higher in the first two quarters every year. The most common symptom was fever. Osteoarticular involvement was found in 44.87% of the patients. Laboratory tests showed that the values of erythrocyte sedimentation rate(ESR), C-reactive protein(CRP), Hemoglobin(Hb), Neutrophils(NEU), Alanine aminotransfease(ALT) and Ferritin in childhood brucellosis with osteoarticular involvement had significant differences than those without osteoarticular involvement or control group (P<0.05). Childhood brucellosis without osteoarticular involvement often accompanied by decrease of NEU , increase of CRP and ALT compared with that control group (P<0.05). The Receiver Operating Curves (ROC) analysis revealed that NEU, CRP and ALT can be used as adjunct parameters in the differential diagnosis of childhood brucellosis. These data suggest that clinical and laboratory characteristics are very important for every clinician, which may have a complementary role in diagnosis of childhood brucellosis.

The implications of Rose Bengal test seroconversion in the diagnosis of brucellosis in children in an endemic region

BACKGROUND

The Rose Bengal test (RBT) is a commonly used simple serological test for brucellosis. We assessed brucellosis in individuals <18 years for RBT performance; duration of RBT positivity following infection; and potential factors associated with RBT seroconversion timing.

METHODS

The medical files of first hospital admissions of brucellosis, 2005-2014, southern Israel, were retrospectively reviewed.

RESULTS

Overall, RBT was positive in 99% of 416 primary brucellosis admissions. The mean age was 9.8 ± 4.5 years; all patients were of Bedouin ethnicity. Of 273 patients with subsequent RBT testing, RBT remained positive in 169 cases (duration range: 0.1-122 months). Overall, 104 patients had subsequent negative RBT result (duration range: 0.9-127; median: 29.9 months). Comparing fast (<30 months) vs. slow (≥30 months) seroconversion, IgM titres ≥1:640 were more common in fast seroconversion episodes (53% vs. 23%, p = .003). Anaemia was more common in the slow seroconversion group (76% vs. 52%, p = .02). Age, gender, ethnicity, fever, arthralgia, thrombocytopenia, leukopenia, liver enzymes, bacteraemia and adequate treatment rates were similar.

CONCLUSIONS

RBT positivity rate in first hospital visit was high. Fast negative seroconversion was associated with high IgM titres and lower anaemia rates at first presentation. These findings may assist early recognition of long-lasting brucellosis patients in endemic regions.

Factors Associated With Single and Recurrent Bacteremia in Childhood Brucellosis

BACKGROUND

Data regarding risk factors of bacteremic brucellosis, and specifically recurrent bacteremia, are scarce. We assessed patients with childhood brucellosis, differentiating between those having culture-negative, single-bacteremic, and recurrent-bacteremic episodes.

METHODS

The medical files of pediatric brucellosis patients, from 2005 through 2014, were reviewed retrospectively. Univariate and multivariate analyses were performed to compare demographic and clinical characteristics of culture-negative, single-bacteremic, and recurrent-bacteremic (≥30 days between positive cultures) episodes.

RESULTS

Of all 436 brucellosis cases, 22% were culture-negative, 72% were single-bacteremic, and 6% were recurrent-bacteremic. In a univariate analysis, single-bacteremic episodes were associated with fever (90% vs 65% and 40% in culture-negative and recurrent bacteremia, respectively) and elevated glutamic oxaloacetic transaminase (GOT) levels. Recurrent-bacteremic episodes were associated with anemia (26% vs 14% and 9% in single bacteremia and culture negative, respectively), elevated GOT, low immunoglobulin M (IgM) titers (56% vs 89% and 99%, respectively), and lower levels of adequate treatment (74% vs 94% and 86%, respectively). In multivariate analyses, single bacteremia was associated with fever (odds ratio [OR], 3.595, compared with culture negative), while recurrent bacteremia was inversely associated with IgM titers ≥1:160 (OR, 0.022 and 0.226 compared with culture negative and single bacteremia, respectively) and fever (OR, 0.108 compared with single bacteremia).

CONCLUSIONS

Brucellosis episodes are commonly complicated with bacteremia. Single-bacteremic episodes were associated with high-grade fever and elevated liver enzymes, possibly indicating high bacterial virulence. Recurrent-bacteremic episodes were associated with poor treatment at initial diagnosis, along with low rates of fever, low IgM titers, and high anemia rates, possibly indicating impaired host response. Physicians should consider treatment modifications for suspected recurrent-bacteremic brucellosis, including monitoring treatment adherence, and possibly administering prolonged treatment.

Use of touch-down polymerase chain reaction to enhance the sensitivity of Brucella melitensis detection in raw milk

Brucellosis is a highly contagious bacterial zoonotic infectious disease severely affecting the public health and economic features of endemic and non-endemic countries. The present study assessed the potentials of using the touch-down polymerase chain reaction (TD-PCR) compared to the conventional PCR and culture methods in order to detect Brucella melitensis in raw milk samples of 55 sheep and 45 goats through deriving the primers from the omp31 element of the Brucella genome. In addition, nine isolates of B. melitensis were identified using the culture method. No positive cases were found in sediment samples, while the fatty tap layer test by conventional PCR and TD-PCR revealed 6 and 16 positive samples, respectively. Based on the survey of the limits of detection by TD-PCR and conventional PCR, TD protocol had a detection threshold of three logs higher than the conventional protocol under the experimental condition. The developed protocol of this study was highly sensitive and extremely fast. Therefore, this TD-PCR protocol could detect even a very low number of bacteria in milk samples. To our best knowledge, this is the first report on the use of the TD-PCR method to identify B. melitensis in milk.

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.

Hematologic Manifestations of Brucellosis in Children

BACKGROUND

Brucellosis is a common zoonosis in the Bedouin population of southern Israel. Limited data exist for the rate and risk factors of hematologic complication of brucellosis in children. We assessed anemia, leukopenia, thrombocytopenia and pancytopenia in childhood brucellosis in southern Israel.

METHODS

Our medical center is the sole hospital in southern Israel. All medical files of brucellosis, 2005-2014, identified through positive blood cultures or International Classification of Diseases 9th revision coding with positive serology, were reviewed retrospectively.

RESULTS

Overall, 511 brucellosis episodes were identified; 42% (N = 214) with ≥1 cytopenia, including 13% (N = 68) anemia, 28% (N = 144) leukopenia, 14% (N = 74) thrombocytopenia and 2% (N = 9) pancytopenia. Overall, 99.8% of episodes were in Bedouin children and 70% in males. In 79% of episodes, blood culture was positive for Brucella melitensis. Acute infections comprised 84% of all episodes. In univariate analysis, older age (10.49 ± 4.81 vs. 9.25 ± 4.89 years), fever (92% vs. 78%), positive blood culture (84% vs. 75%) and IgM ≥1:640 levels (50% vs. 39%) were associated with cytopenia. In contrast, arthralgia was associated with noncytopenic episodes. In multivariate analyses, older age (odds ratio = 1.063) and fever (odds ratio = 3.127) were associated with cytopenia.

CONCLUSIONS

Brucellosis is commonly presented with cytopenia, especially in bacteremic episodes with fever. However, pancytopenia is uncommon and its finding should alert the physician to look for other possible etiologies.

The Bactec FX Blood Culture System Detects Brucella melitensis Bacteremia in Adult Patients within the Routine 1-Week Incubation Period

The performance of the Bactec FX blood culture system for detecting Brucella bacteremia within the routine 1-week incubation period was assessed in a prospective study conducted in an area in southern Israel in which Brucella melitensis is endemic. Aerobic vials (BD Bactec Plus Aerobic/F medium) inoculated with blood specimens obtained from adult patients with positive Rose-Bengal screening test results were monitored for 4 consecutive weeks, and blind subcultures of negative vials were performed on solid media on days 7 and 28. During a 16-month period, a total of 31 (35.2%) of 88 cultures, obtained from 19 (38.0%) of 50 patients, were positive for Brucella melitensis The blood culture instrument identified 30 (96.8%) of 31 positive vials within 7 days of incubation; the single positive vial that was missed by the automated readings was detected only by the blind subculture performed on day 28. It is concluded that the Bactec FX system is able to detect the vast majority of episodes of Brucella bacteremia within the 1-week incubation protocol instituted in most clinical microbiology laboratories and without the need to perform blind subcultures of negative vials, enabling early diagnosis and saving labor and incubation time and space.

Epidemiological, diagnostic, clinical, and therapeutic aspects of Brucella bacteremia in children in southern Israel: a 7-year retrospective study (2005-2011)

BACKGROUND

Data on the various aspects of brucellosis in children living in southern Israel are missing.

OBJECTIVES

Our aim was to study the epidemiological, microbiological, diagnostic, clinical, therapeutic and outcome features of brucellosis in children <19 years of age in southern Israel during 2005-2011.

PATIENTS AND METHODS

The study population included all patients hospitalized with a diagnosis of brucellosis, established according to a clinical presentation compatible with brucellosis+presence of Brucella bacteremia (BB).

RESULTS

A total of 128 (50.8%) of 252 patients admitted with a diagnosis of brucellosis had BB (all with Brucella melitensis). All patients were of Muslim Bedouin ethnicity. The mean incidence of BB in southern Israel was 16 cases/100,000 Bedouin, with no significant changes during the study period. Overall duration of symptoms before diagnosis was 10.1±10.9 days. Fever at diagnosis was recorded in <20% of the patients. The most frequent symptoms were arthralgia (61.7%), weakness (32.8%), gastrointestinal disturbances (27.3%), myalgia (25%), and headache (18.8%). The main clinical findings included monoarthritis (36.7%), hepatosplenomegaly (25%), lymphadenopathy (17.2%), heart murmur (11.7%), and skin rash (9.4%), respectively. Anemia, leukopenia, thrombocytopenia, and pancytopenia were reported in 17.6%, 29.6%, 12.8%, and 2.3% of the patients, respectively. Twenty-nine (30.5%) patients with BB had serum agglutinin titers ≤1/160 (13, 13.7%%, had titers <1/160). Twenty-seven (93%) of the 29 patients aged 0-4 years were treated with gentamicin and trimethoprim-sulfamethoxazole; a total of 77 (60.2%) patients received gentamicin and doxycycline.

CONCLUSIONS

Childhood brucellosis remains an important public health problem in southern Israel. BB was diagnosed in >50% of the children with brucellosis, and B. melitensis was identified in all cases. Arthralgia, weakness, and gastrointestinal complaints were the most common symptoms, and monoarthritis, hepatosplenomegaly, and lymphadenopathy were the most common clinical findings. A considerable number of patients with BB had undetectable/low serum agglutinin titers, suggesting insufficient reliability on serology alone in diagnosis of brucellosis.

A protein-conjugate approach to develop a monoclonal antibody-based antigen detection test for the diagnosis of human brucellosis

Human brucellosis is most commonly diagnosed by serology based on agglutination of fixed Brucella abortus as antigen. Nucleic acid amplification techniques have not proven capable of reproducibly and sensitively demonstrating the presence of Brucella DNA in clinical specimens. We sought to optimize a monoclonal antibody-based assay to detect Brucella melitensis lipopolysaccharide in blood by conjugating B. melitensis LPS to keyhole limpet hemocyanin, an immunogenic protein carrier to maximize IgG affinity of monoclonal antibodies. A panel of specific of monoclonal antibodies was obtained that recognized both B. melitensis and B. abortus lipopolysaccharide epitopes. An antigen capture assay was developed that detected B. melitensis in the blood of experimentally infected mice and, in a pilot study, in naturally infected Peruvian subjects. As a proof of principle, a majority (7/10) of the patients with positive blood cultures had B. melitensis lipopolysaccharide detected in the initial blood specimen obtained. One of 10 patients with relapsed brucellosis and negative blood culture had a positive serum antigen test. No seronegative/blood culture negative patients had a positive serum antigen test. Analysis of the pair of monoclonal antibodies (2D1, 2E8) used in the capture ELISA for potential cross-reactivity in the detection of lipopolysaccharides of E. coli O157:H7 and Yersinia enterocolitica O9 showed specificity for Brucella lipopolysaccharide. This new approach to develop antigen-detection monoclonal antibodies against a T cell-independent polysaccharide antigen based on immunogenic protein conjugation may lead to the production of improved rapid point-of-care-deployable assays for the diagnosis of brucellosis and other infectious diseases.

Brucellosis in low-income and middle-income countries

PURPOSE OF REVIEW

Human brucellosis is a neglected, underrecognized infection of widespread geographic distribution. It causes acute febrile illness and a potentially debilitating chronic infection in humans, and livestock infection has substantial socioeconomic impact. This review describes new information regarding the epidemiology of brucellosis in the developing world and advances in diagnosis and treatment.

RECENT FINDINGS

The highest recorded incidence of human brucellosis occurs in the Middle East and Central Asia. Fever etiology studies demonstrate brucellosis as a cause of undifferentiated febrile illness in the developing world. Brucellosis is a rare cause of fever among returning travelers, but is more common among travelers returning from the Middle East and North Africa. Sensitive and specific rapid diagnostic tests appropriate for resource-limited settings have been validated. Randomized controlled trials demonstrate that optimal treatment for human brucellosis consists of doxycycline and an aminoglycoside. Decreasing the burden of human brucellosis requires control of animal brucellosis, but evidence to inform the design of control programs in the developing world is needed.

SUMMARY

Brucellosis causes substantial morbidity in human and animal populations. While improvements in diagnostic options for resource-limited settings and stronger evidence for optimal therapy should enhance identification and treatment of human brucellosis, prevention of human disease through control in animals remains paramount.

A high percentage of serum samples that test reactive by enzyme immunoassay for anti-Brucella antibodies are not confirmed by the standard tube agglutination test

We describe a retrospective analysis of Brucella enzyme immunoassay (EIA) IgM and IgG results compared to those of the standard tube agglutination test (SAT). Among 1,091 samples tested, 104 (9.5%) and 24 (2.2%) sera were positive by IgM and IgG EIA, respectively. Supplemental testing by SAT showed that 82.7% (86/104) of IgM EIA-reactive samples and 54.2% (13/24) of IgG EIA-reactive samples were negative by SAT. Testing all EIA screen-reactive samples by SAT is required when evaluating patients for potential brucellosis. Due to the limitations of serology, culture remains the gold standard for detecting Brucella infection.