Introduction

Brucellosis is a zoonotic infection that is transmitted to humans by contact with animal secretions and/or consumption of unpasteurized animal products [1]. Brucellosis is an infection with a high rate of morbidity for humans as well as animals; and is known to be endemic in our region.

The prevalence of Brucellosis in United Arab Emirates was estimated at 3.3 cases per 100,000 individuals in 2010 [2]. Brucellosis presents a great threat to economy particularly in low-income countries [3]. The pathogenesis of the infection is highly variable and is influenced by certain factors peculiar to the host as well as those characteristic of the strain of Brucella; therefore, mandating the need for an extensive differential diagnosis [4]. A definitive diagnosis is made by isolating Brucella organisms from blood, bone marrow or other tissue. Rising titers of specific antibodies in presence of symptoms also is confirmatory of diagnosis [5]. As for the treatment regimen for this infection, fortunately, many antibiotics regimens are active against Brucella; however, their efficacies vary. Currently, there is no data on the presentation of brucellosis amongst UAE’s pediatric population. Our study aims to retrospectively depict the epidemiologic and clinical features of brucellosis, as well as, the manifestations, complications, treatment, and prognosis in our pediatric population.

Material and Methods

A retrospective chart review was conducted after obtaining the approval of the institutional review board (Ref: CRD 497/17 AAMD-HREC Protocol No. 531-17). Data of confirmed pediatric Brucella cases between January 2009 and July 2017 were obtained from the health records department at Tawam Hospital; one of the largest tertiary hospitals in the United Arab Emirates (UAE), serving the fourth most populous city in the country. Patients aged between 0-18 years were included.

A diagnosis of Brucella was based on 1) Positive blood culture for Brucella spp. Or 2) Positive Brucella serology of ≥1:160 using the standard Serum Agglutination Test (SAT) with positive symptoms suggestive of Brucellosis. Patients were reviewed from the time of presentation up to one year after completion of therapy. Data included patient’s demographics, presenting signs and symptoms, laboratory investigations and treatment regimen. Analysis was performed with the STATA statistical package (version 15 StataCorp, college Station, TX, USA)

Results

A total of 91 patients were diagnosed with Brucellosis during the 8-year period. The number of cases per year has shown variability throughout the study, with a decline in the later years. The highest number of diagnosed cases was in the year 2016 (Figure1).

The mean age of the affected patients was 6.7 years. Males predominated the cohort, where they comprised 60% of the study population. Overall 76% of patients originated from outskirts of the city (50 Km or more from the city center). Ninety-three percent of our patients had history of unpasteurized milk consumption. Among those who had history of unpasteurized milk ingestion, 79% were from camels, 20% from goats and 1% from cows. Interestingly, 78% of the patients had a positive family history of Brucellosis.

Most reported symptoms were fever (83%), followed by joint pain (36%), abdominal pain (10%) and back pain (4%) (Table 1). Most common reported complication was osteomyelitis at 5%.

Brucella diagnosis was based on positive a blood culture and/or positive antibodies to Brucella strains by direct agglutination testing, namely to B.abortus and B.melitensis. Sixty-five percent of our patients had positive blood cultures. Time to positivity ranged from 40 hours up to 168 hours (mean= 89hrs). As for antibody testing, 91% of our patients had positive titers to B.abortus and B. melitensis. Complete Blood Counts (CBC) were measured in 88 patients. Forty-six percent of our patients had anemia for age and gender, 22% had leukopenia and 14% thrombocytopenia. Liver enzymes were also obtained in all the patients. 30% had elevated AST and 19% had elevated ALT (Table 1).

Several antibiotic combination regiments were used in treating our patients. The following oral regimens were mostly used: Rifampicin plus Trimethoprim-sulfamethoxazole (TMP/SMX) (61%) and Rifampicin plus Doxycycline (20%). Other regimens are summarized below (Table 2).

(Rif – Rifampin; Doxy – Doxycycline; TMP-SMZ – Trimethoprim-Sulfamethoxazole; Gent – Gentamicin)

During the course of treatment, twenty-four antibiotic regimen changes have occurred. These changes were either due to a complex medical course, inability to tolerate medication, to improve compliance or due to physician’s preference. Most of the antibiotic regimen changes were due to TMP/SMX side effects (allergy, rash, raised transaminases, thrombocytopenia or neutropenia).

Forty-nine patients had repeat of titers by the end of treatment. On follow up, 81.6% had high B.abortus levels, with an average repeated level of 1:237 and a maximum of 1:2600, while 67.3% had high B.melitensis with an average level of 1:467, and a maximum of 1:1280.

Discussion

Epidemiology & Burden

Alshehi, et al. estimated the prevalence of Brucellosis in the emirate of Abu Dhabi in UAE to be 3.3 per 100,000 populations in 2016 [2]. However, different numbers have been reported by various health authorities in UAE, reflecting possible under reporting and regional variations. In addition, a recently suggested transmission of Brucella through the hands of family and workers handling cattle may have resulted in increased recognition of cases in our region [2].

Etiology

Brucella spp. are small, gram negative, non-motile, non-spore-forming, rod shaped (coccobacilli) bacterial organisms. It is a zoonotic disease caused by the ingestion of unpasteurized milk from infected animals or close contact with their secretions. Among our population the main reported species were B.melitensis and B.abortus which is endemic among animals in our region such as cows and camels. While other strains such as B.canis and B.suis are not being reported since pigs are never raised in our region and dogs are rare carriers [5] (Table 3).

Clinical Presentation

Prolonged fever and arthritis are the most common presenting signs. In our cohort, almost 96% of our subjects complained of fever for 14 days or more prior to presentation. Only 32% (n=89) complained of joint pain; hip and knee being most affected. Unlike in adults, the sacroiliac joint and the axial skeleton were not affected among our subjects [5]. Only 5% (n=4) of our patients have developed osteomyelitis which is higher than reported rates of 1-2%. Other examples of rare manifestations include: meningoencephalitis, brain abscess, Guillain Barre syndrome, pneumonia, endocarditis and myocarditis, transaminitis, splenic abscess, nephritis, uveitis, thyroid abscess, immune thrombocytopenic purpura and hemophagocytic syndrome [5]. Individual cases of liver failure, epedidemo-orchitis, septic arthritis and hemophagocytic syndrome have occurred in our cohort.

Diagnosis

Although blood culture is the gold standard, it’s yield remains suboptimal. The explanation of the low yield of blood culture is multifactorial including patient’s age [6], the prolonged or chronic clinical course the previous exposure to antibiotics as well as technical aspects including blood sample volume, incubation time, frequency of growth monitoring, performance of blood culture media or detection systems [7-10]. In our study, all the confirmed Brucella cases had elevated titers. In comparison to other published reports, only 65% of the cohort had positive cultures, despite prolonged incubation [11,12]. Al-Tawfiqa JA and AbuKhamsinb A have reported positivity of blood cultures at rate of 80.7% irrespective to age. They have also concluded that patients with higher titers were more likely to have a positive culture, an association that we did not observe in our cohort [12]. In another Chinese retrospective study in 2012, all the patients diagnosed with Brucella had positive blood cultures [11].

ELISA IgM/IgG titers is another method of detection namely used for screening purposes. It is preferably used in the presence of clinical indicators. Brucella titer > 1:320 is still specific for the presence of disease even in the absence of symptoms [13]. However, the presence of high titer post successful therapy could be misleading. After completion of therapy, Brucella titers were repeated in half of our cohort and revealed that approximately 67-80% of patients had elevated titers despite clinical resolution; supporting the previously known fact that titers can remain high up to 2 years or more post treatment.

Other laboratory tests varied from one patient to the other in our cohort depending on their condition and clinical presentation. The most common abnormal lab findings were anemia and elevated transaminases, while the remaining parameters were marginally abnormal.

Brucellosis can cause anemia mostly due autoimmune hemolysis and may also mimic primary hematologic diseases [14]. Brucellosis might have been a direct cause for the anemia in our patients, but the lack of baseline hemoglobin level can argue against Brucellosis being a cause. On the other hand, rising transaminases could be explained by the direct involvement of the liver with resultant hepatosplenomegaly, chronic suppurative disease, and rarely hepatic granulomas [15]. The pathogenic role of brucellosis in development of liver fibrosis and cirrhosis remains limited and understudied [16].

In a pediatric Brucellosis study conducted in Texas, the authors found the WBC to range between 2900-10,600/mm3. They also reported thrombocytopenia, and anemia with variable CRP and ESR levels [17]. Therefore, it seems that all of the above investigations have limited role in the initial diagnosis of Brucellosis [18].

Management

All of our patients were treated with combination therapy. Sixty-one percent of patients received TMP/SMX and Rifampin (n=54). The second most popular combination used was Doxycycline and Rifampin which was used in 20% of our patients (n=18). Other combinations are summarized (Table 2). As for the length of therapy, almost all patients received total of 6 weeks with negligible relapse rate. There have been 24 changes of antimicrobial therapy during treatment for variety of reasons as indicated previously. There are no clear guidelines on how to optimally switch from one regimen to another. Our study is among the first to indicate the reasons of change which will help in anticipating the side effects and guide the therapy.

The literature on pediatric Brucellosis management is limited and there are only few randomized controlled trials among children. Lubani, et al. has concluded that relapse rate in combination therapy group versus monotherapy was not statistically significant, except in TMP/SMX monotherapy, were relapse rate was 30% no matter what the length of therapy was [5]. Lubani, et al. has achieved zero relapse rate after 8 weeks of treatment [5]. Since Lubani’s randomized controlled trial, most of the pediatric literature focused on combination therapy for longer periods of time trying to achieve zero relapse rate [5]. At 2004, Roushan et al. found that 8 weeks of treatment with TMP/SMX plus Doxycycline is better than TMP/SMX plus Rifampin, where failure and relapse rate was 1.96 times higher in the latter [19].

One of the most recent guidelines on management of pediatric Brucellosis was published by Alshaalan MA and colleagues. They have proposed using parenteral gentamicin in combination with Doxycycline for 7 days in children aged less than 8 years followed by five more weeks of oral Doxycycline.

Those recommendations were based on several previous published papers such as Solera J. Espinosa et al. in 1997. Solera and colleagues had conducted a randomized clinical trial, which concluded that that combination of Doxycycline and Parenteral gentamicin for 7 days served as an adequate coverage, provided that the length of therapy of Doxycyclin wasn’t less than 45 days.

A limitation of our study is related to the lack of needed information from the chart review, related to clinical presentation, investigations and changes in management; which is a well-known drawback expected from a retrospective study. This has encouraged us at our institution to start on formulating a local standardized Brucellosis practice guideline. Once completed a prospective cohort study of pediatric Brucella cases will be implemented, which will be an excellent tool to asses for the success of the newly implemented guideline, providing further information on common clinical findings and successful antibiotic regimens.

Conclusion

Pediatric Brucellosis appears to be on an overall decline, this is particularly related to the increased public health awareness of cattle growers and measures employed by local governmental institutions. As Brucellosis can have non-specific presentation a high index of suspicion should be guided by presence of positive Brucella family history, consumption of unpasteurized products or animal contact. There appears to be a strong correlation between culture positivity and the agglutination tests, suggesting that it is as sensitive as the cultures in diagnosing Brucellosis. On the other hand, other ancillary investigations have limited role in diagnosis. The antimicrobial combination therapies were successful, and surveillance of medication side-effect are important to guide anti-microbial regimen changes; however, standardization of care must be implemented.

Conflict of Interest Statement: The authors declare that there is no conflict of interest regarding the publication of this paper.

Ethical Approval: Institutional review board (Ref: CRD 497/17 AAMD-HREC Protocol No. 531-17)

Data Availability: The data used to support the findings of this study are available from the corresponding author upon request.

Acknowledgments: Members of the Microbiology Department at Tawam Hospital.

                                                                                         Figure 1: Pediatric Brucellosis cases between 2009 and 2017.

Table 2: Antibiotic Combinations reported in managing Pediatric Brucellosis.

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