Comparison of serology, culture, and PCR for detection of brucellosis in slaughtered camels in Iran

Early application of metagenomics next-generation sequencing may significantly reduce unnecessary consumption of antibiotics in patients with fever of unknown origin

BACKGROUND

Metagenomic next-generation sequencing (mNGS) is a novel nucleic acid method for the detection of unknown and difficult pathogenic microorganisms, and its application in the etiological diagnosis of fever of unknown origin (FUO) is less reported. We aimed to comprehensively assess the value of mNGS in the etiologic diagnosis of FUO by the pathogen spectrum and diagnostic performance, and to investigate whether it is different in the time to diagnosis, length of hospitalization, antibiotic consumption and cost between FUO patients with and without early application of mNGS.

METHODS

A total of 149 FUO inpatients underwent both mNGS and routine pathogen detection was retrospectively analyzed. The diagnostic performance of mNGS, culture and CMTs for the final clinical diagnosis was evaluated by using sensitivity, specificity, positive predictive value, negative predictive value and total conforming rate. Patients were furtherly divided into two groups: the earlier mNGS detection group (sampling time: 0 to 3 days of the admission) and the later mNGS detection group (sampling time: after 3 days of the admission). The length of hospital stay, time spent on diagnosis, cost and consumption of antibiotics were compared between the two groups.

RESULTS

Compared with the conventional microbiological methods, mNGS detected much more species and had the higher negative predictive (67.6%) and total conforming rate (65.1%). Patients with mNGS sampled earlier had a significantly shorter time to diagnosis (6.05+/-6.23 vs. 10.5+/-6.4 days, P < 0.001) and days of hospital stay (13.7+/-20.0 vs. 30.3 +/-26.9, P < 0.001), as well as a significantly less consumption (13.3+/-7.8 vs. 19.5+/-8.0, P < 0.001) and cost (4543+/-7326 vs. 9873 +/- 9958 China Yuan [CNY], P = 0.001) of antibiotics compared with the patients sampled later.

CONCLUSIONS

mNGS could significantly improve the detected pathogen spectrum, clinical conforming rate of pathogens while having good negative predictive value for ruling out infections. Early mNGS detection may shorten the diagnosis time and hospitalization days and reduce unnecessary consumption of antibiotics.

Molecular detection of Brucella spp. in ruminant herds in Greece

Brucellosis is a worldwide distributed infectious disease. Ruminants and other animal species (swine, dogs, equids, etc.), as well as wild mammals, can be affected. The disease can be transmitted to humans through the food chain or by direct contact with infected animals. Because of the relatively high economic burden due to abortions within a herd, significant efforts have been employed and hence the disease in most European countries has been eradicated. Accordingly, Greece applies both control and eradication programs concerning small ruminants (sheep and goats) and bovines depending on the geographical area. Current challenges in the standard antibody-based laboratory methods used for Brucella detection are the failure to differentiate antibodies against the wild strain from the ones against the vaccine strain Rev1 and antibodies against B. melitensis from those against B. abortus. The aim of the study was to reexamine and combine previously published protocols based on PCR analysis and to generate a rapid, not expensive, and easy to perform diagnostic tool able to confirm the doubtful results delivered from serology. For this reason, 264 samples derived from 191 ruminants of the farm and divided in 2 groups (male/female) were examined with a modified DNA extraction and PCR protocol. Molecular examination revealed the presence of Brucella spp. in 39 out of 264 samples (derived from 30 animals). In addition, Brucella spp. was detected in infected tissues such as testicles, inguinal lymph nodes, fetal liver, and fetal stomach content.

Occurrence and risk factors of brucellosis among domestic animals: an artificial neural network approach

Brucellosis is a zoonotic infectious disease with a worldwide distribution. This cross-sectional study aimed to determine the occurrence of Brucella in milk and blood samples of ruminants and the importance factors associated with animal brucellosis in Eastern Iran. A total of 200 paired samples, including blood (100) and milk (100), were obtained from the goats, sheep, and cows in Eastern Iran. Serum agglutination (SAT) and 2-mercapto ethanol (2-ME) tests were performed on the sera. A multiplex-polymerase chain reaction (m-PCR) assay was performed to identify the following species of Brucella, including B. abortus biovar 1, 2, 4, 3b, 5, 6, and 9, B. abortus S19, B. melitensis, and B. melitensis Rev.1 vaccine strain. B. abortus RB51 vaccine strain was also investigated in a second PCR assay. Risk factors for infection with Brucella spp. including the effect of abortion, contact with the wild animals, herd type, age, and previous vaccination in predicting blood contamination with B. abortus biovar 1, 2, and 4 were modeled by use of the artificial neural network. A total of 23 samples were seropositive regarding SAT and 2-ME tests. In total, B. abortus was detected in 35% and 15% of blood and milk samples, respectively, by the m-PCR assay. One sample of each of milk and blood was detected to have B. melitensis. Some samples were simultaneously contaminated with two Brucella species or two biovars of B. abortus. B. abortus S19 and B. melitensis Rev.1 vaccine strains were also detected in milk and blood samples. The sensitivity and specificity of the ANN model were 81% and 62%, respectively. In conclusion, B. abortus had higher frequency than B. melitensis in blood and milk samples. ANN determined herd type, previous vaccination, and age of the animal as the largest predictors of blood contamination with B. abortus.

Isolation of Brucella melitensis from seronegative camel: potential implications in brucellosis control

Brucellosis is a significant zoonotic infection in Iran impacting both humans and animal health status. A number of reasons such as few clinical signs complicate the diagnosis of this infection in Camelidae. Despite the ubiquitous use of serological tests for the first screening of brucellosis in camel, this approach showed several restrictions because of the intracellular properties of this organism as well as decline antibody titers in chronic stage. This study aimed at identifying the presence of Brucella spp. in blood and lymph node samples collected from slaughtered male camels of Sistan-Baluchistan province by serology, culture and polymerase chain reaction (PCR) assay. For this purpose, 2854 blood camel samples were sampled and analyzed for Brucella detection by serological screening tests. The molecular detection of IS711 gene and Bruce-ladder assay as well as culture were performed using the lymph nodes of all seropositive camel (n = 10) and 30 seronegative samples. Results showed that 0.35% (10/2854), 0.24% (7/2854) and 0.21% (6/2854) of blood samples were positive by RBPT, SAT and 2ME, respectively. However, 0% (0/10) and 70% (7/10) of lymph node samples collected from seropositive camels were positive for Brucella infection by culture and PCR, respectively. Furthermore, 6.6% (2/30) of seronegative lymph node specimens showed the presences of Brucella by PCR and culture assay. The results of the present study indicated the low seroprevalence of Brucella infection in male camels of the Sistan-Baluchistan province and highlighted the complementary role of PCR techniques for a better screening of Brucella infection among seronegative camels. Moreover, the potential shedding of Brucella within undiagnosed camel milk and secretions is a serious problem which may result in further spread and maintenance of Brucella infection among both human and livestock. Thus, for brucellosis detection and control, our results suggested that a first PCR screening supported by a bacteriological isolation on positive samples should be performed along with the serological test in endemic countries to identify the source and prevent the uncontrolled spread of the disease among camels.

Zoonotic implications of camel diseases in Iran

Approximately 60% of all human pathogens and 75% of emerging infectious diseases are zoonotic (of animal origin). Camel zoonotic diseases can be encountered in all camel-rearing countries. In this article, all studies carried out on camel zoonotic diseases in Iran are reviewed to show the importance of camels for public health in this country. More than 900 published documents were systematically searched to find relevant studies from 1,890 until late 2018. The collected articles were classified according to the aetiological agents. In this study, 19 important zoonotic diseases were reported among Iranian camels including listeriosis, leptospirosis, plague, Q fever, brucellosis, campylobacteriosis, tuberculosis, pasteurellosis, clostridiosis, salmonellosis, Escherichia coli infections, rabies, camelpox, Middle East respiratory syndrome coronavirus, Crimean-Congo haemorrhagic fever, echinococcosis, cryptosporidiosis, toxoplasmosis and dermatophytosis, most of which belong to bacterial, viral, parasitic and fungal pathogens, respectively. Results show that camels are one of the most important sources of infections and diseases in human; therefore, continuous monitoring and inspection programs are necessary to prevent the outbreak of zoonotic diseases caused by this animal in humans.

Brucella abortus contamination of camel milk in two Iranian regions

Brucella spp. commonly infect humans in various regions worldwide. Human brucellosis mainly spreads through the consumption of contaminated raw dairy products and meat from domestic livestock (water buffalo, goats, sheep, cattle, pigs and camels). In this regard, the origin and routes of transmission of this bacterium should be carefully determined in order to control the source of infection. This study aimed to evaluate the rate of Brucella spp. contamination of camel milk samples sent for analysis to the national brucellosis laboratory during 2018 in Iran. For this purpose, 96 milk samples from 96 dairy camel herds were randomly collected from two provinces and investigated for the presence of Brucella spp contaminations by both bacterial culture method and polymerase chain reaction (PCR). No clinical manifestation of brucellosis was reported in camels from which milk samples were collected. Using the culture method, three milk samples (3%) originating from two camels of Isfahan province (4%) and one camel from the Semnan province (2%), were contaminated with Brucella abortus. According to PCR analyses, B. abortus gene was detected in 14 (14.5%) milk samples, including 9 and 5 samples from Isfahan (18%) and Semnan (11%) province, respectively. PCR method revealed significant differences (p = 0.02) in the level of contamination with B. abortus between milk samples collected from two regions. These results represent the first report regarding the isolation of B. abortus from raw camel milk in Iran and highlight the importance to screen apparent healthy camels. Therefore, the consumption of raw camel milk may contribute to the spread of human brucellosis in endemic regions.