Risk Factors Associated with Human Brucellosis: A Systematic Review and Meta-Analysis

Background: Brucellosis is a zoonosis disease that can affect humans and a wide range of domestic and wild animals. Susceptibility to brucellosis in humans can be related to various factors, such as nutritional and occupational factors. This study evaluated factors related to brucellosis and identified influential risk factors for human infection. Methods: We performed a systematic literature review and meta-analysis of studies in PubMed, Web of Science, and Scopus. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to measure the strength of the association between some potential factors and the risk of brucellosis. Results: From 277 initial studies, 19 case-control studies were included in this review. Significant risk factors for brucellosis included occupation (OR 3.31, 95% CI 1.68-6.55), having aborted animals (OR 4.16, 95% CI 2.03-8.50), consumption of meat (OR 2.17, 95% CI 1.44-3.36), unpasteurized milk (OR 3.86, 95% CI 1.81-8.23), and raw cheese (OR 4.20, 95% CI 1.63-10.85). Conclusion: The results of this study advance the understanding of the etiology of brucellosis. In this meta-analysis, we found the association of different environmental factors with the risk of brucellosis. Additional high-quality prospective studies are needed to determine whether these factors cause brucellosis and to identify other factors.

Detection of Virulence-Associated Genes among Brucella melitensis and Brucella abortus Clinical Isolates in Greece, 2001-2022

Brucellosis remains an important zoonotic disease in several parts of the world; in Greece, although it is declining, it is still endemic, affecting both the financial and public health sectors. The current study was undertaken to investigate the presence and distribution of virulence-associated genes among Brucella spp. clinical strains isolated during 2001-2022. Species identification was performed using conventional methodology and Bruce-ladder PCR. The presence of the virulence genes mviN, manA, wbkA, perA, omp19, ure, cbg and virB was investigated using PCR. During the study period, a total of 334 Brucella isolates were identified, of which 328 (98.2%) were detected from positive blood cultures; 315 (94.3%) of the isolates were identified as B. melitensis, whilst the remaining 16 (4.8%) and 3 (0.9%) were identified as B. abortus and B. suis, respectively. Notably, two of the B. melitensis were assigned to the REV-1 vaccine strain type. The presence of the omp19, manA, mviN and perA genes was confirmed in all 315 B. melitensis isolates, while ure, wbkA, cbg and virB genes were detected in all but 9, 2, 1 and 1 of the isolates, respectively. All eight virulence genes were amplified in all B. abortus and B. suis isolates. The detection rate of virulence genes did not differ significantly among species. In conclusion, brucellosis is still considered a prevailing zoonotic disease in Greece, with the majority of the isolates identified as B. melitensis. The eight pathogenicity-associated genes were present in almost all Brucella isolates, although the ure gene was absent from a limited number of B. melitensis isolates.

Adaptation of Brucella melitensis Antimicrobial Susceptibility Testing to the ISO 20776 Standard and Validation of the Method

Brucellosis, mainly caused by Brucella (B.) melitensis, is associated with a risk of chronification and relapses. Antimicrobial susceptibility testing (AST) standards for B. melitensis are not available, and the agent is not yet listed in the EUCAST breakpoint tables. CLSI recommendations for B. melitensis exist, but they do not fulfill the requirements of the ISO 20776 standard regarding the culture medium and the incubation conditions. Under the third EU Health Programme, laboratories specializing in the diagnostics of highly pathogenic bacteria in their respective countries formed a working group within a Joint Action aiming to develop a suitable method for the AST of B. melitensis. Under the supervision of EUCAST representatives, this working group adapted the CLSI M45 document to the ISO 20776 standard after testing and validation. These adaptations included the comparison of various culture media, culture conditions and AST methods. A Standard Operation Procedure was derived and an interlaboratory validation was performed in order to evaluate the method. The results showed pros and cons for both of the two methods but also indicate that it is not necessary to abandon Mueller–Hinton without additives for the AST of B. melitensis.

Human Brucellosis in Greece, 2005-2020: A Persistent Public Health Problem

Brucellosis remains an important zoonosis in various parts of the world. In Greece, brucellosis is endemic in sheep and goats. Since 1998, animal control measures include vaccination of sheep and goats older than 3 months of age in the mainland (vaccination zone) and slaughtering of infected livestock on the islands (eradication zone). We retrieved data from the mandatory notification system for 2005-2020 to describe the epidemiology in humans and assess current public health measures. Overall, 1786 notifications and an additional 111 cases related to an outbreak in 2008 (eradication zone) were recorded. The mean annual notification rate was 0.9/100,000 population (standard deviation [SD]: 0.35). A substantial mean annual decline in notification rate was reported in 2019 and 2020. A statistically significant decreasing trend of brucellosis notification rate was observed over the whole 16-year period (p < 0.001). The mean annual notification rate was significantly higher in the vaccination zone (1.2/100,000) (SD: 036) compared with the eradication zone (0.2/100,000) (SD: 0.14) (p < 0.001). Seventy percent of cases was male (n = 1175) and the highest mean notification rate was recorded in the 45-64 age group (1.3/100,000). The majority of cases (71%) reported animal contact and almost half of the cases (49%) were stockbreeders by occupation. Consumption of unpasteurized dairy products, mainly of their own production, was reported by 57% of cases; for 115 (6.5%) cases, animal exposure or consumption of unpasteurized dairy products were not recorded. Despite animal control measures, brucellosis remains endemic in Greece with cases in the vaccination zone, as well as the eradication zone. We recommend re-evaluation and strengthening of animal control programs and training of people working in stock breeding regarding disease transmission in co-operation with local farmers' associations.

Predictive analysis of the number of human brucellosis cases in Xinjiang, China

Brucellosis is one of the major public health problems in China, and human brucellosis represents a serious public health concern in Xinjiang and requires a prediction analysis to help making early planning and putting forward science preventive and control countermeasures. According to the characteristics of the time series of monthly reported cases of human brucellosis in Xinjiang from January 2008 to June 2020, we used seasonal autoregressive integrated moving average (SARIMA) method and nonlinear autoregressive regression neural network (NARNN) method, which are widely prevalent and have high prediction accuracy, to construct prediction models and make prediction analysis. Finally, we established the SARIMA((1,4,5,7),0,0)(0,1,2)12 model and the NARNN model with a time lag of 5 and a hidden layer neuron of 10. Both models have high fitting performance. After comparing the accuracies of two established models, we found that the SARIMA((1,4,5,7),0,0)(0,1,2)12 model was better than the NARNN model. We used the SARIMA((1,4,5,7),0,0)(0,1,2)12 model to predict the number of monthly reported cases of human brucellosis in Xinjiang from July 2020 to December 2021, and the results showed that the fluctuation of the time series from July 2020 to December 2021 was similar to that of the last year and a half while maintaining the current prevention and control ability. The methodology applied here and its prediction values of this study could be useful to give a scientific reference for prevention and control human brucellosis.

Trends of Bloodstream Infections in a University Greek Hospital during a Three-Year Period: Incidence of Multidrug-Resistant Bacteria and Seasonality in Gram-negative Predominance

The aim of the study was to assess the epidemiology, the incidence of multidrug-resistant bacteria and bloodstream infections' (BSIs) seasonality in a university hospital. This retrospective study was carried out in the University General Hospital of Patras, Greece, during 2011-13 y. Blood cultures from patients with clinical presentation suggestive of bloodstream infection were performed by the BacT/ALERT System. Isolates were identified by Vitek 2 Advanced Expert System. Antibiotic susceptibility testing was performed by the disk diffusion method and E-test. Resistance genes (mecA in staphylococci; vanA/vanB/vanC in enterococci; bla_KPC/bla_VIM/bla_NDM in Klebsiella spp.) were detected by PCR. In total, 4607 (9.7%) blood cultures were positive from 47451 sets sent to Department of Microbiology, representing 1732 BSIs. Gram-negative bacteria (52.3%) were the most commonly isolated, followed by Gram-positive (39.5%), fungi (6.6%) and anaerobes bacteria (1.8%). The highest contamination rate was observed among Gram-positive bacteria (42.3%). Among 330 CNS and 150 Staphylococcus aureus, 281 (85.2%) and 60 (40.0%) were mecA-positive, respectively. From 113 enterococci, eight were vanA, two vanB and two vanC-positives. Of the total 207 carbapenem-resistant Klebsiella pneumoniae (73.4%), 202 carried bla_KPC, four bla_KPC and bla_VIM and one bla_VIM. A significant increase in monthly BSIs' incidence was shown (R2: 0.449), which may be attributed to a rise of Gram-positive BSIs (R2: 0.337). Gram-positive BSIs were less frequent in spring (P < 0.001), summer (P < 0.001), and autumn (P < 0.001), as compared to winter months, while Gram-negative bacteria (P < 0.001) and fungi (P < 0.001) were more frequent in summer months. BSIs due to methicillin resistant S. aureus and carbapenem-resistant Gram-negative bacteria increased during the study period. The increasing incidence of BSIs can be attributed to an increase of Gram-positive BSI incidence, even though Gram-negative bacteria remained the predominant ones. Seasonality may play a role in the predominance of Gram-negative's BSI.

Novel diagnostic approach on the identification ofBrucella melitensisGreek endemic strains-discrimination from the vaccine strain Rev.1 by PCR-RFLP assay

Despite the intensive implementation of control programmes goat, sheep and human brucellosis remains endemic in Greece. As the discrimination between field endemic strains and vaccine strain Rev.1 is not feasible, it is essential to develop new diagnostic tools for brucellosis diagnosis. Moreover, effective disease control requires enhanced epidemiological surveillance in both humans and animals including robust laboratory support. Two new multiplex (duplex) polymerase chain reactions (PCRs) were developed and the results were compared with those obtained by real‐time PCR and bacteriological biotyping. A total of 71 Brucella spp. Greek endemic strains were identified at species and biovar level, using both molecular and conventional techniques. Their discrimination from the vaccine strain Rev.1 was achieved, using polymerase chain reaction‐restriction fragment length polymorphism assay (PCR‐RFLP). All 71 strains were identified as Brucella melitensis by multiplex PCR as well as by real‐time PCR and conventional biotyping. Sixty‐two (87.3%) out of 71 strains were identified as B. melitensis biovar 3, eight (11,3%) strains as biovar 1 and only one (1,4%) as biovar 2. Digestion with PstI restriction enzyme revealed that all strains were field endemic strains, as they gave different patterns from the vaccine strain Rev.1. Brucella melitensis biovar 3 appears to be the predominant type in Greece. The novel multiplex PCR produced results concordant to ones obtained by real‐time PCR and conventional biotyping. This technique could support and facilitate the surveillance of Brucellosis in Greece contributing in the control of the disease.

Caprine brucellosis: A historically neglected disease with significant impact on public health

Caprine brucellosis is a chronic infectious disease caused by the gram-negative cocci-bacillus Brucella melitensis. Middle- to late-term abortion, stillbirths, and the delivery of weak offspring are the characteristic clinical signs of the disease that is associated with an extensive negative impact in a flock's productivity. B. melitensis is also the most virulent Brucella species for humans, responsible for a severely debilitating and disabling illness that results in high morbidity with intermittent fever, chills, sweats, weakness, myalgia, abortion, osteoarticular complications, endocarditis, depression, anorexia, and low mortality. Historical observations indicate that goats have been the hosts of B. melitensis for centuries; but around 1905, the Greek physician Themistokles Zammit was able to build the epidemiological link between "Malta fever" and the consumption of goat milk. While the disease has been successfully managed in most industrialized countries, it remains a significant burden on goat and human health in the Mediterranean region, the Middle East, Central and Southeast Asia (including India and China), sub-Saharan Africa, and certain areas in Latin America, where approximately 3.5 billion people live at risk. In this review, we describe a historical evolution of the disease, highlight the current worldwide distribution, and estimate (by simple formula) the approximate costs of brucellosis outbreaks to meat- and milk-producing farms and the economic losses associated with the disease in humans. Successful control leading to eradication of caprine brucellosis in the developing world will require a coordinated Global One Health approach involving active involvement of human and animal health efforts to enhance public health and improve livestock productivity.

Incidence Patterns and Occupational Risk Factors of Human Brucellosis in Greece, 2004-2015

Background:

Brucellosis is the most common bacterial zoonosis worldwide. Greece has the highest reported incidence among EU countries. However, occupational risk factors have not been well described.

Objective:

To determine the incidence patterns and exposure risk factors of brucellosis in Greece.

Methods:

We used national-level surveillance and occupational denominator data to estimate the incidence patterns and exposure risk factors of brucellosis in Greece, with particular emphasis on occupation.

Results:

Between November 2003 and December 2015 a total of 2159 human brucellosis cases was reported. The mean incidence rate was 1.62 per 100 000 population per year. A large majority of cases (77.1%) reported consumption of unpasteurized milk or contact with livestock animals. Most cases occured in farmers and livestock breeders (1079 [87.7%] of 1231 cases reporting their occupation), corresponding to an annual incidence of 7.1 per 100 000. However, there were other occupations with a similar or higher risk: butchers and abattoir workers (12.7 per 100 000), laboratory personnel (3.1 per 100 000), while the highest risk was for veterinarians (53.2 per 100 000).

Conclusion:

Brucellosis incidence in specific occupational groups was much higher than in the general population. These results underline the importance of collecting information on occupation, both during the diagnostic process and in the surveillance system. Besides efforts to control brucellosis in animals, organized prevention efforts are needed within an occupational health framework, especially for the most vulnerable workers.