1、1,BRUCELLOSIS,2,Introduction & HistoryBrucellosis: Disease of domestic and wild animals (zoonosis): Transmittable to humans. It has different non-specific symptoms and signs “No disease, not excepting tuberculosis and syphilis, is more protean in its manifestations”(Simpson). Marston Surgeon serving
2、 with Royal Artillery during Crimean war-reported first accurate description of human brucellosis. 1886, Bruce isolated Micrococcus (later Brucella) Melitensis from spleens of malta fever victims.,3,Introduction and History (Contd.) Zamit maltese physician, identified native goats as infection reser
3、voir, during his work with Mediterranean fever commission 1904-1907. He also identified fresh goats milk as vehicle of transmitting disease from animals to humans. 1895, Bang (Danish Veterinarian) identified Bacillus (later Brucella) abortus as cause of contagious abortions in cattle. Evans (America
4、n bacteriologist) recognized relation of Malta fever agent and Bangs disease,4,Introduction and History (Contd.) Genus Bacillus, micrococcus, causing Malta fever, renamed Brucella, to honor Bruce. Traum, 1914, isolated Brucella Canis, from aborted Kennel-bred dogs. Carmichael, 1966, isolated Brucell
5、a Canis, from aborted Kennel-bred dogs. Brucella ovis from sheep and Brucella neotomae from desert wood rats, added to Brucella species, but to date these two not shown to cause human infections.,5,Introduction and History (contd.)1994, British and American workers, independ-ently, isolated previuou
6、sly unknown Brucellaorganism from carcasses of marine mammals andcetaceans on Scotland coast, and from dolphin inCalifornia. These isolates-homogenous with distinctive metabolic, sensitivities to dye, phagesensitivity-tentatively named Brucella Maris.,6,THE PATHOGEN Brucellae: Small, GN cocobacilli,
7、 non-motile, non-spore forming. Brucellae grow aerobically. Some spp. Require supplemental carbon dioxide for primary isolation. Any high-quality peptone-based media enriched with blood or serum serve for in vitro cultivation. Isolation form clinical specimens require prolonged ( 30 days) incubation
8、. Brucella strains always catalse-positive; but oxidase and urease and H2S production vary.,7,The Pathogen (contd.) Major Brucellae species and their biovars differentiated by selective inhibition of growth on media containing dyes-e.g. Thionin and basic fuchsin. Genus Brucella divided into six (pos
9、sibly seven) nomen spp. on basis of preferred hosts and cultural, metabolic and antigenic characteristics. DNA-DNA hybridization studies shown remarkable( 95%) homology between strains, suggesting mono-specific gems with subspecies corresponding evolutionary lineage adapted to specific hosts.,8,The
10、Pathogen (contd.) Wilson and Miles, first described major cell wall antigen and virulence factor of brucellae to be S-Lps containing A and M antigens. Presence of 4-amino, 4,6 dideoxymannose in Lps is responsible for antigenic cross-reaction with other G.N.B. e.g. - vibrio cholerae 01 and Yersinia 0
11、9. Numerous protein antigens maybe important in inducing protective immunity.,9,Epidemiology Brucellosis zoonosis all infections, derive directly or indirectly from animals exposure. Disease exists world-wide, esp. Mediterranean, Arabic Peninsula, Indian subcontinent, parts of Mexico and Central Sou
12、th America. B. abortus found mainly in cattle, but others spp. like buffalo, camels, tales can be affected. B. Melitensis primary affects goats and sheep. Camels can be important source in some countries. B. Suis biovars 1-3 in domestic and feral swine, cause abattoir-assoc. human disease.,10,Epidem
13、iology (Contd.) B. Canis: Least common cause of human disease. Animals: Brucellosis, Ch. Infection, persisting for life. Brucellae localization in reproductive organs, accounts for major manifestations abortion and sterility. Brucellae shed in large numbers in: Milk, urine, cyetic products of infect
14、ed animals.,11,Epidemiology (Contd.) Thus, Brucellosis constitutes occupational risk for: farmers, veterinarians, abattoirs and Laboratory personnel. Routes of transmission to human include:- Director contact with animals or their secretions,through cuts and skin abrasions.- Infected aerosols inhale
15、d or inoculated into eyeconjunctival sac.- Ingestion of unpasteurized dairy products.,12,Epidemiology (Contd.)- Meat products: rare source of infectionbecause: Meat is rarely eaten raw andorganisms are present in low number ofmuscle tissue.- Blood and bone marrow may transmitdisease when ingested in
16、 some cultures.- Human-to-human transmission: Unusual, butrare cases suspected to be sexuallytransmitted.,13,Epidemiology (contd.)- One case reported recently, presumptively dueto intra-uterine transmission. Aids patient, prone to infections by zoonoses, but Brucellosis occurred in very few of these
17、 patients. If CD4 not severely depressed, course of brucellosis in Aids pts. not different from disease in immunocompetent pts. Brucellosis not rare in children as previously believed. Brucellosis manifests similarly in: Neonates, children and adults.,14,Pathogenesis B. melitensis and B. suis, more
18、virulent than B. abortus and B. canis. Infection with any B. species, including attenuated vaccine strains can cause serious human disease. Disease determined by:- Host nutritional and immune status.- Size of infectious inoculum.- Route of transmission.Ex: -Low gastric juice PH, more effective inpre
19、venting B. abortus than B. melitensisinfection when administered by oral route.,15,Pathogenesis (contd.)-Therefore, drugs that decrease gastricacidity were implicated in food bornebrucellosis. Once brucellae gain entry to body: PMN Leukocytes attracted to inoculation site by chemotaxis. Normal human
20、 serum has limited bactericidal activity against brucellae, but it effectively opsonizes bacteria for phagocytosis by PMN Leukocytes.,16,Pathogenesis (contd.) Brucellae: Facultative intracellular, slowly dividing pathogens with capacity to survive and multiply within host phagocytic cells. Mechanism
21、 by which brucellae evade intracellular killing by PMN-Leukocytes incompletely under-stood, it is possible that bacteria property enable them to escape detection. Factors contributing to intracellular survival:- Production of adenine and guanine monophos-phate.,17,Pathogenesis (contd.) -These suppre
22、ss myeloperoxide H2O2-halidesystem and cu-zn superoxide dismutase, whicheliminates reactive oxygen intermediates. Spink compared brucellosis with typhoid fever because bacteria enter lymphatic and replicate within regional lymph nodes. Hematogenous dissemination then followed by localization of bact
23、eria within organs rich in reticuloendothelial system, e.g. liver, spleen and B. marrow.,18,Pathogenesis (Contd.) Brucellae ingested by mononuclear phagocytes survive and replicate initially. Intracellular survival within macrophages facilitated by inhibition of phagoxome-Lysosome fusion by soluble
24、products of brucellae, and production of stress-induced proteins. Eventual elimination of virulent brucellae depends on activation of macrophages through develop-ment of Th-1type cell-mediated immunity. Cytokines contributing to anti-brucella activity of activated macrophages include: TNF-alpha, TNF
25、-gamma, IL-1, IL-12.,19,Pathogenesis (contd.) Major determinant of virulence and immuno-dominant antigen of Brucella is S-Lps. Growth of B. abortus in cattle placental tissue apparently enhanced by eruthritol, this may explain localization of brucellae in genital tracts of ungulates.,20,HOST IMMUNIT
26、Y Genetic studies in various animals showed that resistance to intracellular pathogens is polygenic; but single genes recognized to have major effect on immune-mediated resistance. Selected breeding of cattle yielded evidence for genetic determination of resistance to bovine brucellosis. Data sugges
27、ted that resistance reflected in immunoglobulin allotypes and in difference in ability of macrophages to control B. abortus replication in vitro.,21,Host Immunity (Contd.) S-Lps is major deter of virulence of brucellae and dominates antibody response. Humoral anti-bodies to S-Lps confer short-term p
28、rotection as shown by passive transfer experiments using monoclonal and polyclonal antibodies. Antibodies to S-Lps used for diagnosis when bacterial isolation is unsuccessful. Variety of serologic tests used to measure anti-bodies to brucellae. Earliest was serum agglutina-tion test (SAT), devised b
29、y Wright and Smith 1897. SAT. Measures total quantity of agglutinating anti-bodies, but does not distinguish between immuno-globulin isotypes.,22,HOST IMMUNITY (Contd.) In time, IgM antibodies titers decline, and with treatment IgG antibodies titers fall consistent with recovery. Failure of IgG tite
30、r to decline is prognostic of relapse or chronic infection. Currently, there is interest in cytoplasmic protein antigens in both smooth and rough strains, which could be used for diagnostic purposes. Reddin and colleagues modified SAT, by adding 2-mercapto-ethanol(2ME) to differentiate agglutina-tio
31、n by IgG-antibodies, and showed that IG antibodies correlated well with active infection.,23,Host Immunity (contd.) Combination of SAT and 2 ME test shown to be useful to monitor Brucellosis course and response to therapy. Application of enzyme-linked immunoabsorbent assay (ELISA) measures immune re
32、sponse to therapy. IgM antibodies appear within 1st week of infection and followed by switch to IgG synthesis after 2nd week. In time, IgM antibodies titers decline and with treat- ment IgG antibodies, titers fall consistent with recovery.,24,Host Immunity (contd.)Failure of IgG titer to decline is
33、prognostic of relapse or chronic infection. Currently, there is interest in cytoplasmic protein antigens in both smooth and rough strains, which could be used for diagnostic purposes.,25,Clinical Manifestation Symptoms of Brucellosis: non-specific, e.g. fever, sweats, malaise, anorexia, headache, ba
34、ckpain. Onset: acute or insidious, beginning within 2 to 4 weeks after inoculation. An “Undulant” fever pattern observed if patients go untreated for long periods. Some patients c/o malodorous sweat and peculiar mouth taste. Depression common and often out of proportion to severity of symptoms. In c
35、omparison to plethora of somatic complaints, physical abnormalities are few. Mild lymphadenopathy reported in 10 to 20% of cases.,26,Clinical Manifestation Splenomegaly or hepatomegaly in 20 to 30% of cases. Brucellosis: systemic infection in which any organ or system of the body can be involved. At
36、tempts to categorize the disease into acute, subacute and chronic, according to symptoms, length and severity are purely arbitrary. Disease referred to focal or localized when involvement of specific organ predominates. However, there is little evidence that such complication represent distinct subs
37、et of patients.,27,Clinical Manifestation (contd.) When CNS or heart involved, such cases: difficult to treat and outcome can be affected. Problem in interpreting literature on brucellosis is differentiating acute and chronic forms of brucellosis. Because of necessity to treat patients for prolonged
38、 periods, relapse not uncommon, especially if therapy discontinued prematurely. Most relapses occur within 3 to 6 months of discontinuing therapy. Disease considered chronic if infection persistsmore than 12 months (arbitrary definition).,28,Clinical Manifestation (contd.) Chronic Brucellosis usuall
39、y caused by persisting deep foci of infection, e.g. suppurative lesions in bone, joints, liver, spleen or kidneys. In contrast, some patients experience delyaed convalescence after treatment, with persisting non-specific complaints of ill health, notably fatigue. Such disease distinguished from true
40、 chronic brucellosis by absence of objective signs of disease, as fever, in addition, chronic brucellosis characterized by persistently high IgG antibodies titres in serum, but:-,29,Clinical Manifestation (contd.) Patients with delayed convalescence: poorly understood, some authorities attribute tha
41、t to pre-existing psychoneurosis exacerbated by brucellosis. Such patients present diagnostic dilemma, because their complaints resemble brucellosis, but further antimicrobial therapy, ineffective, and patients often believe they suffer from incurable brucellosis.,30,Clinical Manifestation (contd.)
42、Patients with delayed convalescence: poorly understood, some authorities attribute that to pre-existing psychoneurosis exacerbated by brucellosis. Such patients present diagnostic dilemma, because their complaints resemble brucellosis, but further antimicrobial therapy, ineffective, and patients oft
43、en believe they suffer from incurable brucellosis.Relapse not usually caused by antibiotic resistance, because strains of brucellae isolated during relapse have antibiogram identical to original infecting strains.,31,ComplicationsNervous SystemDirect CNS invasion by brucellosis less than 5%although
44、depression and mental inattention occurcommonly in brucellosis. CNS Complications:- Meningitis- Encephalitis- Myelitis radiculoneuritis,32,Complications (contd.)- Brain abscess- Epidural abscess- Demyelinating syndromes- Meningovascular syndromes- Acute and chronic meningitis: Most frequentCNS compl
45、ication, and can be presentingfinding, or occur late in disease course.- Brucella meningitis difficult to distinguish fromother causes of meningitis.,33,Complications (contd.) Nuchal rigidity occurs in 50% of cases. Brucella meningitis difficult to distinguish from other causes CSF: Lymphocytic pleo
46、cytosis, elevated protein, low to normal glucose. G. stain usually negative. Culture positive 25% of cases. Diagnosis made by finding specific antibodies in CSF,34,Histologic findings:- Inflammation of leptomeninges- Adhesive arachnoiditis- Vasculitis- LeukoencephalitisGIT 70% of patients with bruce
47、llosis- Anorexia, abd. Pain, nausea, vomiting, diarrheaor constipation.,35,GIT 70% of patients with brucellosis (contd)- Pathologic lesions:- Intestinal mucosa hyperemia with peyerspatches inflammation.- Acute ileitis radiologically and histologicallyin patients with colitis B. melitensis.Hepatobili
48、ary system (HPS)- Liver, largest reticuloendothelial organ, probablyalways involved in brucellosis.- LFT, usually slightly elevated.,36,Hepatobiliary system (HPS)- Brucella hepatitis pathologic findingsspectrum is variable.- B. abortus infection: Granulomasindistinguishable from sarcoidosis.- In con
49、trast: B. melitensis: Lesions range from small, almost insignificantmononuclear cell aggregates surroundingfoci of necrosis scattered throughout parenchyma, to diffuse non-specificinflammation resembling viral hepatitis.,37,Hepatobiliary system (HPS) (contd.)- Occasionally: Collections of mononuclea
50、rcells forming loose granuloma may be found.- Suppurative abscess of liver and spleencommon with B. suis infection, andoccasionally with B. melitensis.- Hepatic lesions resolve with antimicrobialtherapy, and in absence of other causes(HCVm HBV, alcohol abuse). No cirrhosis,despite inflammation severity.,
