Important properties Mycobacterium tuberculosis

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1 Bacteria that cannot be stained by Gram Bacteria that are not stained by Gram Mycobacteria Spirochetes Mycoplasmas Chlamydias Mycobacteria aerobic, acid-fast bacilli cell wall: more complex than that of Grampositive or negative bacteria high lipid content acid fast bacteria - an organism s ability to retain the stain despite treatment with a mixture of acid and alcohol Ziehl-Neelsen staining (acid-fast staining) Classification pathogenic species M. tuberculosis M. bovis M. africanum M. leprae opportunstic mycobacteria, atypical mycobacteria (MOTT mycobacteria other than tuberculosis) M. avium M. intracellulare M. simiae M. asiaticum M. xenopi M. marinum M. kansasii saprophytic mycobacteria M. smegmatis M. gordonae M. gastri M. terrae 4 Important properties Mycobacterium tuberculosis obligate aerobe causes disease in highly oxygenated tissues slow growth hours cell wall structure lipids mycolic acid long chained fatty acids (acid-fastness) other lipids - waxes, phosphatides Cord factor trehalose dimycolate virulence factor serpentine cordlike growth Toxic to mammalian cells Inhibit migration of leukocytes and blocks macrophage activation Chronic granulomas proteins antigenic PPD (purified protein derivate) - tuberculin relatively resistant to acids and alkalis resistant to dehydration survival in dried sputum (importance in transmission by aerosols) 6

2 Morphology Smear with Ziehl-Neelsen stain - sputum slim rods in smears effectuated from cultures virulent strains show specific arrangement in serpentine due to the presence of cord factor 7 8 Immunfluorescence Cultivation Löwenstein-Jensen agar (egg yolk, malachite green, etc.) aerobic conditions long incubation first colonies may appear after days of incubation negative cultivation record only after 60 days R colonies cauliflower/breadcrumbs 9 10 Antigenic structure tuberculoproteins allergens induce delayed, cellular hypersensitivity polysaccharides induce antibody production (without significance in healing or diagnosis) Pathogenesis no exotoxins, no endotoxin infects macrophages survives and multiplies within the phagosome produces a protein that prevents the fusion of the phagosome with the lysosome the organism escapes the destroying effect of lysosomal enzymes 11

3 Evolution of the infection primary infection (usually in childhood) usually in the lungs, lower lobes parenchymal exudative lesion + lymph nodes: Ghon complex (characteristic radiologic findings) usually heals tubercle bacilli may disseminate via bloodstream in different organs reactivation (usually in adults) in the lung (usually in the apices) or other organs Lesions caused by M. tuberculosis exudative lesions acute inflammatory response resembles bacterial pneumonia lungs primary infection granulomatous lesions tubercles: granulomas surrounded by fibrous tissue; the central part of the granuloma undergoes caseation necrosis lung tubercles may erode a bronchus, empty their caseous content - spread heals by fibrosis and calcification during reactivation Immunity and hypersensitivity Mantoux test humoral immunity has no role in controlling the infection cellular immunity CD4+ T lymphocytes, macrophages in persons with impaired cellular immunity the risk of disseminated infection is more likely delayed cellular hypersensitivity develops diagnostic importance - tuberculin test (Mantoux test) PPD is injected intradermally after hours the diameter of the resulting induration is measured >10 mm: positive skin test => the person came in contact with M. tuberculosis and developed hypersensitivity reaction / indicates a previous infection by the organism and not necessarily an active disease positive results can be expected after 4-6 weeks from the infection BCG vaccination also causes positive reaction tends to decrease in time 15 Clinical findings most infections are asymptomatic disease occurs in case of inadequate cellular immune response many organs may be involved general symptoms: fever, fatigue, night sweats, weight loss pulmonary tuberculosis: cough, hemoptysis (blood in the sputum) scrofula: tuberculosis of cervical lymph nodes (nontender, usually unilaterally) miliary tuberculosis multiple disseminated tuberculosis ( millet seeds) meningitis, osteomyelitis (vertebral: Pott s disease) gastrointestinal tuberculosis abdominal pain, diarrhea renal tuberculosis dysuria, hematuria, flank pain, sterile pyuria Miliary tuberculosis kidney lung

4 Miliary tuberculosis Laboratory diagnosis miliary CNS tuberculosis miliary hepatic tuberculosis acid-fast staining of sputum or other specimens fluorescent methods cultivation detection of nucleic acid by polymerase chain reaction testing susceptibility against tuberculostatic agents resistance is spreading! MDR (multidrug resistant) strains, XDR (resistance to all tuberculostatic agents) strains Epidemiology transmission: from person to person by respiratory aerosols humans are the natural reservoir of M. tuberculosis in developing countries M. bovis may also cause tuberculosis; reservoir: cow the risk of infection is higher in socioeconomically disadvantaged people poor housing, poor nutrition Tuberculosis in Romania first place regarding tbc incidence in Europe 107,8/ inhabitants (2008) morbidity is increasing 21 Incidence of tuberculosis in Romania (/ inhabitants) MDR, XDR strains , ,6 134,1 142,2 135, WHO data ,2 million new cases 14,4 million registered cases 0,5 million cases due to MDR strains ,8 70 in Romania the ratio of MDR strains is 2,9% 4,5% of MDR strains are XDR strains

5 Prophylaxis BCG (Bacillus Calmette-Guerin) vaccine live attenuated Mycobacterium bovis used in countries with high incidence of tbc effective in preventing overt disease, especially in children (efficiency variable) before vaccination PPD it must not be given to immunocompromised people (live BCG bacilli may cause disseminated disease) nor to pregnant women screening (PPD, thoracic radiography) contacts: chemoprophylaxis Treatment antituberculosis agents combination therapy to prevent the development of resistance several month duration Mycobacterium leprae causes leprosy cannot be grown on culture media may be grown in the mouse footpad or armadillo humans are the natural host preferentially grows in skin structures, superficial nerves (optimal temperature for growth is 37 C) slow growing: doubling time: 14 days slowest growing human bacterial pathogen Clinical findings incubation several years (up to 20) onset: gradual tuberculoid leprosy cellular mediated immunity limits the growth hypopigmented macular skin lesions thickened superficial nerves, anesthesia lepromatous leprosy cell-mediated response is poor, lesions contain high number of bacilli multiple nodular skin lesions occur Clinical findings disfiguration due to: skin anesthesia results in burns and other traumas, which often become infected resorption of bones infiltration of the skin and nerves results in thickening end folding of the skin Epidemiology infection: after prolonged contact with patients (M. leprae present in nasal secretions, skin lesions of patients) present worldwide most cases in Asia, Africa Romania - Tichilesti, a few hundred patients 30

6 WHO/TDR/McDougall LL WHO/TDR 31 LL Atypical mycobacteria widespread in the environment cause diseases in immunocompromised patients are not spread from person to person M. avium-intracellulare complex highly resistant to antituberculosis drugs Spirochetes Treponema Borrelia Leptospira 33 Spirochetes thin-walled, flexible, spiral rods motile undulations of axial filaments that lie under the outer sheath (endoflagella) Treponema pallidum causes syphilis sexually transmitted disease does not grow on culture media may be isolated in rabbit testicle transmitted by intimate contact or vertically (mother to fetus) or by blood transfusion morphology: thin, tight, regular spirals

7 Treponema pallidum silver stain Treponema pallidum dark-field microscopy Antigenic structure lipids from the treponemal cell induce formation of nonspecific antibodies (reagin) protein antigens induce specific antibody formation Pathogenesis no toxins or enzymes infects the endothelium of small vessels important in brain and cardiovascular lesions in tertiary syphilis Clinical findings Primary syphilis ulcus durum primary syphilis the spirochetes multiply at the site of entry after 2-10 weeks of infection appears a characteristic primary lesion at the portal of entry: ulcus durum (chancre) indurated basis, not painful localization: vulva, cervix glans penis extragenitally: oropharynx, perianal, tongue cures spontaneously no symptoms for 2-24 weeks but spirochetes spread widely

8 Primary syphilis ulcus durum Primary syphilis ulcus durum Primary syphilis ulcus durum Ulcus durum Ulcus durum kissing lesions Clinical findings secondary syphilis maculopapular rash palms, soles moist lesions on mucosal surfaces: condylomata lata rich in spirochetes and highly infectious heal spontaneously + low-grade fever, malaise, anorexia, weight loss, myalgias, adenopathy internal organ involvement (meningitis, nephritis, hepatitis)

9 Second stage syphilis maculopapular rash Secondary syphilis Secondary syphilis - rash Secondary syphilis Secondary syphilis - condyloma lata Secondary syphilis - alopecia

10 Clinical findings Tertiary syphilis latent period: early stage 1-2 year after secondary syphilis symptoms of secondary syphilis may reappear late latent period can last many years no symptoms, patients are not infectious tertiary syphilis granulomas (gummas) skin, bones, organs central nervous involvement tabes dorsalis, paresis cardiovascular lesions (aortitis, aneurysm of ascending aorta) in tertiary lesions treponemas are rarely seen Ulcerated gumma Congenital syphilis treponemas are transmitted through the placenta (tipically after the 3 rd month) skin and bone lesions hepatosplenomegaly stillbirth, fetal abnormality Congenital syphilis Immunity antibodies do not stop disease progression patients cured in early stages may be reinfected patients in late stage disease are resistant to reinfection

11 Diagnosis detection of treponemas from lesions serology Epidemiology, prevention, treatment syphilis occurs worldwide, incidence is increasing may be underreported there is no vaccine; non-specific methods may prevent transmission prevention of congenital syphilis: screening and treatment of pregnant women treatment: penicillin Borrelia burgdorferi Borrelia genus microaerophilic, fastidious organisms can be cultivated on special culture media reservoir - rodents, domestic and wild animals vector ticks from Ixodes genus (hard ticks) Ticks larva, nymph, adult Ticks

12 Classification, morphology Borrelia burgdorferi Borrelia burgdorferi sensu lato includes 3 genospecies: Borellia burgdorferi sensu stricto - USA Borrelia afzelii - Europe Borrelia garinii - Europe large, irregular spirals Pathogenesis no exotoxins, no enzymes spread of the organism from the bite site through the surrounding skin dissemination by blood to various organs: heart, joints, central nervous system Borrelia burgdorferi infection Lyme disease tickbite tick-borne disease incubation 3-30 days progressive disease I. stage early localized infection weeks multiplication in the portal of entry, at the bite site erythema migrans (EM), non-itching, circular red rash with clear center +/- flulike symptoms dissemination via bloodstream Erythema migrans Lyme disease II. stage early disseminated infection weeks to months later meningitis, encephalitis, cranial neuropathy (seventh-nerve palsy), myocarditis latent stage borrelias persist in the organism

13 Lyme disease III. stage late persistent infection arthritis usually of large joints (chronic, intermittent symptoms) chronic progressive nervous system disease acrodermatitis chronica atrophicans (picture) in case of Borrelia afzelii among elderly Epidemiology spring - autumn infected tick s bite Romania: there are no clear data regarding the ratio of infected ticks In Europe: B. burgdorferi sensu lato infected ticks are found predominantly in central Europe isolated in almost every country incidence in southern countries is lower Prevention vaccine antigenic structure is variable LYMErix (contains recombinant outer membrane protein) results in limited protection, there are many controversies regarding this vaccine nonspecific prevention measures (clothing, tick repellents, body examination in order to early tick removal) Treatment antibiotics (amoxicillin, doxycyclin, amoxicillin clavulanate for early stage Lyme disease, ceftriaxone for neuroborreliosis and late stage Lyme diasease) in endemic areas: prophylaxis with one dose antibiotic (doxycyclin or amoxicillin) Diagnosis cultivable, but fastidious cultivation is not routine diagnostic approach Serology 2- tier test 1 st : ELISA or IF (may be false positive) 2 nd : confirmatory Western-blot neuroborreliosis detection of antibodies from the cerebrospinal fluid Leptospira genus L. interrogans human pathogen L. biflexa

14 Leptospira interrogans Leptospira scanning electron microscopy tightly coiled, fine, corkscrew shaped spirochetes with hooks at their ends, widely distributed in nature several serovars asymptomatic infections in different animal species pomona swine grippotyphosa mouse canicola dog icterohaemorrhagiae rats hebdomadis rats, mice ballum - mouse Silver stain on liver biopsy showing leptospires Leptospira dark-field microscopy Pathogenesis animal reservoir animals eliminate leptrospiras by urine contaminated water portal of entry skin, mucosa by ingestion Disease asymptomatic infections symptomatic infection - leptospirosis incubation weeks mild to severe disease 2 stages flue-like symptoms - bacteraemia involvement of different organs: central nervous system, liver, kidneys

15 Treatment, prevention antibiotics vaccine: killed whole bacteria for persons at risk Diagnosis detection of leptospiras first week from blood (low sensitivity) second week: urine, CSF Serology