Quantitative polymerase chain reaction based quantification of Brucella DNA in serum of pre- and post-therapeutic occupationally exposed infected human population

A novel, highly sensitive, one-tube nested quantitative real-time PCR for Brucella in human blood samples

IMPORTANCE

This study developed a highly sensitive and efficient method for the detection of brucellosis by introducing a one-tube nested quantitative real-time PCR (qPCR) approach, representing a remarkable advance in the field. The method demonstrated an impressive analytical sensitivity of 100 fg/μL, surpassing conventional qPCR and enabling the detection of even low levels of Brucella DNA. In addition, the study's comprehensive evaluation of 250 clinical samples revealed a specificity of 100% and a sensitivity of 98.6%, underscoring its reliability and accuracy. Most importantly, the new method significantly improved the detection rate of low-burden samples, reducing cycle threshold values by an average of 6.4. These results underscore the immense potential of this approach to facilitate rapid and accurate brucellosis diagnosis, which is critical for effective disease management and control.

Human Brucellosis: An Observational Study From a Tertiary Care Centre in North India

AIM

The main aim/objective of this study was to detect and characterize the Brucella species from patients having complaints of joint pain and also to know the potential causes of human brucellosis. In our study, we focused on joint pain symptoms that may be due to arthralgia or arthritis.  Introduction: Brucellosis is a neglected zoonotic disease that affects both humans and animals. In humans, brucellosis begins with chronic illness leading to great financial losses from not being able to work well and continued treatment costs, but few such studies have come from northern India. Joint pain is the common presentation of brucellosis and there are several risk factors associated with brucellosis.

METHODS

A total of 200 blood samples were collected from the participants having joints pain from September 2019 to September 2021 at Gandhi Memorial & Associated Hospitals of King George's Medical University, Lucknow, India, and tested by serology for anti-Brucella IgM and IgG enzyme-linked immunosorbent assay (ELISA), molecular tests byreverse transcriptase-polymerase chain reaction (RT-PCR), conventional polymerase chain reaction (PCR), and automated blood culture system. The anti-Brucella IgM and IgG ELISA were performed using the kit from NovaTec Immundiagnostica GmbH (Dietzenbach, Germany). Isolation of DNA was carried out using the QIAamp DNA Mini kit (QIAGEN, Hilden, Germany), and the primers and probes specific for targeted regions (BCSP31 and IS711 gene) in the Brucella genome were procured from Eurofins Scientific SE (Luxembourg, France), and for internal control from CDC.

RESULT

The study showed 19 (9.5%) and 23 (11.5%) positive results by anti-Brucella IgM ELISA and anti-Brucella IgG, respectively, and of these, one (0.5%) was positive for both anti-Brucella IgM and anti-Brucella IgG ELISA. Out of 19 anti-Brucella IgM ELISA positive, eight (4%) samples were positive for PCR/RT-PCR and that was negative for anti-Brucella IgG ELISA. All blood culture reports of all patients were negative.  Conclusion: Anti-Brucella IgM ELISA was more accurate than anti-Brucella IgG ELISA in detecting human brucellosis. Consumption of animal products (i.e. milk, a dairy product of cow, buffalo, goat, and meat of goat) and contact with animals were the main risk factors that were identified for Brucella disease.

Seroprevalence of Brucellosis in Patients Having Complained of Joint Pain: A Case Control

BACKGROUND

Brucellosis is a neglected zoonotic disease affecting humans and animals.

OBJECTIVES

This study aimed to estimate the seroprevalence of brucellosis in patients with joint pain.

METHODS

A total of 200 participants aged from 7 to 86 years were involved in this study. Blood samples were collected from all the participants for two years, from September 2019 to September 2021, and screened for Brucella using anti-brucella IgM ELISA and anti-brucella IgG ELISA antibodies. A questionnaire was used to collect data on socio-demographic characteristics and human brucellosis-related risk factors.

RESULTS

Human Brucella seroprevalence was 19 (9.5%) for Brucella IgM ELISA and 23 (11.5%) for Brucella IgG ELISA. The sensitivity for Brucella IgM ELISA and Brucella IgG ELISA was 65.2% and 31.6%, respectively, while the specificity was 44.1% for Brucella IgM ELISA and 77.9% for Brucella IgG ELISA. All blood culture reports of all patients were negative. The principal presentation was the observable symptoms of human brucellosis: fever, headache, chills, myalgia, and Joint pain.

CONCLUSION

Risk factors like consumption of raw milk or their products were found to be the most important for Brucella infection, so the awareness or information of risk factors and the modes of transmission is much more important in control and prevention programs. General awareness about clinical symptoms should be increased, which will improve proper diagnosis and will be helpful in early treatment. An ELISA test should be considered for diagnosing brucellosis in both acute and chronic phases.

Prevalence of Brucella spp. in raw milk and artisanal cheese tested via real-time qPCR and culture assay

Brucellosis is one of the most prevalent zoonotic diseases with worldwide distribution. Although the incidence of brucellosis varies widely in different regions, it is a major concern for public health around the world. This study aimed to determine the prevalence and quantity of Brucella spp. in sheep and goat raw milk, as well as artisanal cheeses produced in the North-west of Iran. To evaluate the intrinsic parameters that may affect the survival of Brucella spp., some of the cheese properties (e.g., pH, salt, moisture, and storage time before selling) were also assessed. A total of 572 samples consisting in 214 sheep raw milk, 92 goat raw milk, and 266 local artisanal cheese samples were collected. The artisanal cheeses were manufactured from a mixture of raw sheep and goat milk. According to the results, using quantitative real-time PCR (qPCR), 17.29%, 15.22%, and 22.93% of the sheep raw milk, goat raw milk, and artisanal cheese samples were found positive for Brucella spp., respectively. In comparison with culture assay, qPCR was 3.5 to 5 times (p < 0.05) more sensitive in the detection of Brucella spp. The results also revealed that the mean values of Brucella spp. load in sheep and goat raw milk and artisanal cheeses were 1.22, 1.55, and 1.43 log cell/ml or g, respectively. A positive correlation was found between Brucella load and successful detection of Brucella spp. by culture assay. Data also suggested a correlation (p < 0.01) between the load of Brucella spp. estimated by qPCR and pH value, salt content, and storage period of the cheese samples. However, Brucella spp. load did not correlate significantly with the moisture content. Based on the results, in any of the cheese samples with a pH value less than 4.5 and a storage period more than five months, no contamination with Brucella spp. was detected.

Validation of real-time polymerase chain reaction versus conventional polymerase chain reaction for diagnosis of brucellosis in cattle sera

Background and Aim:

Different polymerase chain reaction (PCR) techniques have and are still being used for the direct detection of Brucella DNA in serum samples of different animal species and humans without being validated or properly validated, resulting in discrepancies. Thus, this study aimed to evaluate the diagnostic performance of the TaqMan Real-Time-PCR (RT-PCR) targeting the bcsp31 gene versus conventional PCR for the accurate diagnosis of brucellosis at the genus level in cattle sera.

Materials and Methods:

One hundred and eighty-four serum samples were collected from bacteriologically positive and negative cows with ages ranging from 1 to 5 years old at some infected private farms in the Nile Delta under quarantine measures as well as brucellosis free farms. These samples were classified into four groups after serological diagnosis and investigated by TaqMan RT-PCR and conventional PCR targeting the IS711 gene for Brucella DNA detection. The diagnostic performance characteristics of both PCR techniques were estimated considering the bacteriological results as a gold standard.

Results:

TaqMan RT-PCR revealed superiority over conventional PCR; it was able to detect Brucella DNA in 95% (67/70) and 89% (25/28) of the cattle sera samples belonging to Group 1 (serologically and bacteriologically positive) and Group 2 (serologically negative but bacteriologically positive), respectively. On evaluating the diagnostic performance, TaqMan RT-PCR showed superior diagnostic sensitivity (93.9%), diagnostic specificity (88.4%), performance index (182.3), almost perfect kappa agreement (0.825±0.042), strong positive correlation (r=0.826), high accuracy based on the receiver operating characteristic (ROC) curve, and area under the ROC curve (0.911) at p<0.05 and CI of 95%.

Conclusion:

A cattle serum sample is not the metric of choice for targeting Brucella genomic DNA by conventional PCR. The time-saving and rapid TaqMan RT-PCR method revealed a better diagnostic performance in the detection of Brucella DNA in cattle sera. Such performance offered by TaqMan RT-PCR may be considered a step toward the possibility of using such technology in the direct differentiation between Brucella-infected and -vaccinated cattle immunized by smooth vaccines from cattle sera using primers specific for such vaccines.

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.

Monitoring the course of Brucella infection with qPCR-based detection

OBJECTIVES

To determine blood Brucella DNA loads between brucellosis patients and those without brucellosis.

METHODS

The patient group included 350 brucellosis patients. The control was composed of 200 subjects without brucellosis. The extracted DNA from blood was tested by quantitative polymerase chain reaction (qPCR). The cutoff value was determined by receiver operating characteristic curve analysis. A portion of the brucellosis patients were monitored by qPCR during therapy.

RESULTS

The detection limit of qPCR was between 1E+01cfu/μL and 1E+08cfu/μL. The standard curve R² reached 0.998. The cutoff value was 4E+01cfu/μL, which was determined by comparison of the patient group and the control. The qPCR assay had a specificity of 100% and a sensitivity of 93.14%. The monitoring results showed that the Brucella DNA load decreased in most patients during the first 4 weeks of treatment. One patient with bad treatment compliance showed a rebound.

CONCLUSIONS

The qPCR results were in accordance with the course of brucellosis in the clinic. The DNA load often reflects the situation of the Brucella-infected patient. The cutoff value provides an important reference of infection. This qPCR-based method can be used to assist in the diagnosis of brucellosis and to adjust the therapy.

Optimization and validation of a real-time polymerase chain reaction protocol for the diagnosis of human brucellosis

Due to limitations in commercial diagnostic methods, this study aimed to develop a reliable real-time polymerase chain reaction (Rt-PCR) assay for early diagnosis of brucellosis. Optimization of the Rt-PCR method was performed on serum samples spiked by Brucella melitensis with different densities ranging from 10¹ to 10⁸ colony-forming units (cfu)/mL; each density was prepared in ten samples. The limit of detection was investigated by using Thermo DNA extraction kit with Maxima SYBR Green Rt-PCR and two TaqMan probe-based Rt-PCR protocols performed by QuantiTect and TEMPase multiplex PCR master mixes in two thermal cyclers, which were Rotor-Gene and Bio-Rad. The validation of the optimized protocol was carried on 20 brucellosis-negative samples and 20 samples spiked with B. melitensis by using a combination of Thermo DNA extraction kit with TEMPase PCR master mix. SYBR Green Rt-PCR yielded positive results on all samples having ≥ 10⁴ cfu/mL of B. melitensis in both thermal cyclers. Its limit of detection was 112 DNA copies per reaction. The positivity of both probe-based Rt-PCR protocols was 100% and 80% on the samples having 10³ cfu/mL and 10² cfu/mL of B. melitensis, respectively. The limit of detection of probe-based protocols was defined as 4 DNA copies per reaction. The optimized Rt-PCR protocol showed high-level accuracy, precision, specificity, and sensitivity, each having a rate of 100%. The current study indicated that the TaqMan probe-based Rt-PCR protocol optimized and validated with serum samples can be reliably used for early diagnosis of brucellosis.