High Incidence of Respiratory Involvement in a Cluster of Brucella suis-Infected Workers from a Pork Processing Plant in Argentina.

Epidemiological and clinical aspects of Brucella suis infection in 17 workers from a pork processing plant in Argentina occurring between January 2014 and July 2015 are presented. All patients reported working 9 h daily without adequate personal protection garment. Blood cultures were positive for Brucella spp. in 14 of the 17 patients (82.3%). All isolates were identified as B. suis biovar 1. Although fever, sweats, asthenia, myalgia and hepatic involvement were the most frequent clinical manifestations, an unusually high incidence of respiratory involvement was found. From 13 patients in which chest radiography was performed, four (30%) had radiological abnormalities, including lobar pneumonia in two cases (one with pleural effusion) and interstitial involvement in other two. The high frequency of respiratory involvement in our series makes necessary to consider brucellosis in the differential diagnosis of respiratory diseases in pork processing plant employees.

Occupational infection due to Brucella abortus S19 among workers involved in vaccine production in Argentina.

The pathological consequences of exposure to the vaccine strain Brucella abortus S19 were evaluated in 30 employees from vaccine-manufacturing plants. Active brucellosis was diagnosed in 21 subjects, of whom only five recalled an accidental exposure. Clinical manifestations were mild, and only one patient presented a complication. After antimicrobial therapy, initially symptomatic patients either experienced clinical remission or had mild persistent symptoms. This is the first study reporting infection by B. abortus S19 among workers from vaccine-manufacturing plants, which in many cases was acquired from unnoticed exposures. Measures to improve the safety of B. abortus S19 handling should be implemented.

Limited diagnostic usefulness of antibodies to cytoplasmic proteins of Brucella in early-treated human brucellosis.

Antibodies to cytoplasmic proteins (CP) of Brucella have been shown to be useful for the diagnosis of human brucellosis; however, some early-diagnosed patients lack such an antibody response while having high titers of antibodies to lipopolysaccharide (LPS). To address which factors determine this serological discrepancy in the early stages of brucellosis we examined the antibody response to CP and LPS of 21 patients involved in an outbreak of B. melitensis infection who had a short duration of clinical illness at diagnosis (3-40 d). At diagnosis, antibodies to LPS (IgM and/or IgG) were found in all patients, while anti-CP antibodies were detected in 16 subjects (76%). At 6 weeks post-diagnosis IgG to CP (with or without IgM) had been detected in 13 patients and IgM alone had been found in 4; however, 4 other patients (19%) had no response to CP. No significant differences were found between these 3 groups in terms of age, gender, antimicrobial agents or factors that could hamper the immune response. Notably, however, the 4 non-responders and 3 of the 4 patients having only IgM to CP had started antibiotic therapy within 14 d post-symptoms, while treatment was started later in 9 of 13 patients who developed anti-CP IgG. In addition, maximum titers of IgG to CP tended to be lower in early-treated patients. These results suggest that very early antibiotic therapy hampers the antibody response to Brucella CP but has little impact on the anti-LPS response. Given the higher specificity of the former and the higher sensitivity of the latter, both reactivities should be measured in order to diagnose human brucellosis.

Detection of antibodies to Brucella cytoplasmic proteins in the cerebrospinal fluid of patients with neurobrucellosis.

The diagnosis of human neurobrucellosis usually relies on the detection of antibodies to Brucella lipopolysaccharide (LPS) in cerebrospinal fluid (CSF) by agglutination tests or enzyme-linked immunosorbent assay (ELISA). Here we describe the detection of immunoglobulin G (IgG) to cytoplasmic proteins (CP) of Brucella spp. by ELISA and Western blotting in seven CSF samples from five patients with neurobrucellosis. While IgG to CP (titers of 200 to 12, 800) and IgG to LPS (800 to 6,400) were found in the CSF of these patients, these antibodies were not detected in CSF samples from two patients who had systemic brucellosis without neurological involvement. The latter, however, had serum IgG and IgM to both LPS and CP. No reactivity to these antigens was found in CSF samples from 14 and 20 patients suffering from nonbrucellar meningitis and noninfectious diseases, respectively. These findings suggest that, in addition to its usefulness in the serological diagnosis of human systemic brucellosis, the ELISA with CP antigen can be used for the specific diagnosis of human neurobrucellosis.

Human infection by Brucella melitensis: an outbreak attributed to contact with infected goats.

Although several outbreaks of Brucella melitensis infection have been reported among laboratory workers or goat cheese consumers, outbreaks related to rural labour have been rarely studied. An outbreak of human brucellosis among farm workers of Argentina was studied and revealed a close relationship with an epidemic of caprine abortions which occurred shortly before on the same farm. High rates of B. melitensis infection were found among goats. Active brucellosis was diagnosed in 33 subjects (14 with positive blood culture for B. melitensis), while other 27 did not show evidence of illness. While 25 of the brucellosis active patients were rural workers, only 5 of the healthy subjects were engaged in rural labour. Active brucellosis was diagnosed in 91.3% of the subjects in continuous contact with goats and in 32% of those having an occasional contact with the animals. All the 60 subjects denied consumption of goat cheese or milk. As shown here, epidemic human infections by B. melitensis may develop among people frequently in contact with infected goat herds or goat manure.

Serological follow-up of human brucellosis by measuring IgG antibodies to lipopolysaccharide and cytoplasmic proteins of Brucella species.

A serological 2-year follow-up of 35 patients who had brucellosis with different clinical outcomes was performed. Patients were followed up by standard tube agglutination (STA) and 2-mercaptoethanol STA (2ME-STA) tests and by two enzyme-linked immunosorbent assays (ELISAs) to independently measure values of serum IgG to either lipopolysaccharide (LPS) or cytoplasmic proteins of Brucella. Whereas STA and 2ME-STA tests revealed characteristic antibody profiles for patients who recovered (group I), this was not the case for patients with persistent illness (group II) or patients with relapses (group III). On the other hand, titers measured by the 2ME-STA test were low or negative in 10 patients who had positive blood cultures. Levels of IgG antibodies to LPS and proteins in each group of patients exhibited characteristic changes. For group I, however, antibodies to proteins were better predictors of recovery, since titers reached negative values for five patients. Levels of IgG antibodies to LPS and proteins were persistently high in group II patients, and peaks in these antibody levels corresponded with relapses in group III patients. The determination of values of IgG antibodies to proteins by ELISA appears useful for the serological follow-up of patients with brucellosis.

Urban outbreak of a Brucella melitensis infection in an Argentine family: clinical and diagnostic aspects.

An outbreak of Brucella melitensis in a family was studied. From the fourteen family members who ate unpasteurized goat cheese nine became ill. Patients included four females and five males of 8 to 75 years old. In seven of the patients the diagnosis was confirmed by positive blood culture for B. melitensis biovar 1. All the patients were analyzed by standard tube agglutination (STA) and standard tube agglutination with 2-mercaptoethanol (STA-2ME) tests at the time of diagnosis. In six of the patients, ELISA assays were used to assess the humoral immune anti-protein and anti-lipopolysaccharide (LPS) responses. Anti-LPS IgG antibodies were detected in all of the patients. Anti-proteins IgG antibodies were present at significant levels in all the studied patients including the STA-2ME negative ones.

Characterization of an 18-kilodalton Brucella cytoplasmic protein which appears to be a serological marker of active infection of both human and bovine brucellosis.

Some anticytoplasmic protein monoclonal antibodies (MAbs) from mice immunized by infection with Brucella ovis cells have been obtained. One of these MAbs, BI24, was used to purify by immunoaffinity a protein with a pI of 5.6 and a molecular mass of 18 kDa. This protein was present in all of the rough and smooth Brucella species studied, but it could not be detected in Yersinia enterocolitica 09. Three internal peptides of this protein were partially sequenced; no homology with other bacterial proteins was found. The immunogenicity of the 18-kDa protein was studied with both human and bovine sera by a capture enzyme-linked immunosorbent assay system with MAb BI24.

Differentiation between active and inactive human brucellosis by measuring antiprotein humoral immune responses.

A preparation of Brucella abortus cytoplasmic proteins was depleted of lipopolysaccharide (LPS) by immunoadsorption with a monoclonal antibody (MAb), BC68, specific for the O antigen of B. abortus smooth LPS. Two enzyme-linked immunosorbent assay (ELISA) systems were developed and used in this study. The first system includes an LPS-free cytoplasmic protein preparation; the second one was based on antigen capture on MAb BC68. By using these systems, we have demonstrated that 94% (33 of 35) of the brucellosis patients studied showed immunoglobulin G antiprotein response and also that all of the patients showed a strong anti-LPS reactivity. Thirty-six serologically positive individuals with no active infection at the time of examination (SPI) were also included. No immunoglobulin G antibodies against proteins were detected in 34 of them (92%), whereas 31 SPI (86%) showed various degrees of anti-LPS reactivity. The use of the LPS-free protein extract in ELISAs made it possible to establish differential reactivity patterns between active and inactive brucellosis.