number Done by Corrected by Doctor Hamid Al Zoubi

Transcription

1 number 15 Done by أبو عجمي ة مها Corrected by Waseem Abu Obeida Doctor Hamid Al Zoubi

2 In case you don t know - (Bacillus = rod) and (bacilli = rods) - hypersensitivity tests can be either immediate (within few hours or less) or delayed, in this sheet, we are discussing the delayed test. - Dormant (from the verb dormir which means sleep) - Focus = many foci & bacterium = many bacteria Mycobacteria: Mycobacteria tuberculosis. Mycobacteria leprae. Mycobacteria tuberculosis Mycobacterium tuberculosis (M. tuberculosis) is a strict aerobic bacillus. It affects 50% of people worldwide (about 2 billions). It causes death to 3 million (Tuberculosis (TB) increases, when immunity responses are lowered as a result of chemotherapy and HIV infections). MDR (multi-drug resistant tuberculosis) is one of the problems, we are facing today. The M. tuberculosis complex are human pathogens that cause tuberculosis, the complex includes: Notes: 1. M. tuberculosis 2. M. africanum 3. M. bovis 4. M. canettii M. canetti has smooth colonies but M. tuberculosis has rough colonies. The mycobacteria are characterized by thick lipid-rich cell walls (thick mycolic acid), this is why they are stained by acid-fast / ziehl neelson stains, so we don t use gram stains because of their hydrophobicity. mycobacteria are characterized by acid-fast staining property. Most of them are strict aerobic acid-fast bacilli.

3 They are killed by UV, Alcohol, many types of aldehydes, they are also destroyed by pasteurization (heat sensitive). They are resistant to alkalis, acids and ammonia. Growth Media -Löwenstein Jensen (LJ) medium is an egg glycerol-based medium to which malachite green dye is added to inhibit the growth of other bacteria (other than mycobacteria) and to provide a contrasting colour against which colonies of mycobacteria are easily seen. (something like a background) -Liquid medium, enriched with bovine serum albumin. Note: Liquid medium is more rapid (takes about 10 days) but Löwenstein Jensen (LJ) is slow, it takes more time (6-8 weeks), because the bacterium that causes TB is slow growing. Pathogenesis: (commonly in lungs) ( immune response by CD4 T helper cells) If a malnourished patient from a poor environment, with fever (rise in his body temperature), weight loss, sweating, think about TB as a possibility. TB vaccines (BCG) are given intradermally (age: 1 st month), some countries don t provide TB injections, why? Because TB tests cannot distinguish active disease from past vaccination, meaning If a person was immunized against TB, the result would be a positive test, because antibodies were produced by vaccines but if the person is not already vaccinated, one option is left, he is latently infected/ have the disease- (bear with me, this will be discussed in more detail in the following pages). What Slides Say: o Lung Primary TB: Macrophages 1 in alveoli > Ghon s focus > To hilar lymph nodes > primary TB complex > PTB attacked by Macrophages 2 (O2 consumption) > surrounding the lesion in granuloma (caseation) > latent Tuberculosis (TB) TB in other places: Skin, intestine and lymph nodes

4 o Post Primary TB 90% of primary infections > latent > reactivation or reinfection > post primary TB Reactivation of primary TB > Post primary TB (Also due to REinfection): Same as in primary but tuberculoma instead of granuloma Spread to LLL, upper airways, bladder, skin (Lopus vulgaris) and bladder (more spread and infectivity) o Secondary and Milliary TB 10% of primary > secondary TB > meningitis, pott s disease, urogenital and skin involvement (s.t milliary TB if opened into a blood vessel > disseminated) crossword puzzle? Let s try to solve it. Note: we wrote what the doctor said, you might find some differences when referring to greenwood or any other source. Initial infection is commonly in the lung, (inhalation of mycobacteria). The alveolar macrophages (Macrophages1) engulf the inhaled bacteria in the alveoli (leading to the formation of Ghon s focus,), Some bacteria are carried to the hilar lymph nodes, then the primary TB complex is formed, then this PTB complex is attacked by another type of macrophages (macrophages 2 :/), these macrophages consumes oxygen decreasing the amounts of O2 reaching the bacteria thus killing it, PTB complex plus macrophages 2 form granuloma and caseation necrosis. (In addition to lungs, Tuberculosis can occur in other places such as skin, intestine and lymph nodes) Then in 90% of patients (with good immune responses), primary infections become latent (dormant foci), then when immunity becomes low for one reason or another, Reactivation of dormant foci of tubercle bacilli or exogenous reinfection leads to post-primary tuberculosis, this leads to post primary TB (reactivated latent), The same process of granuloma formation occurs, but the caseation areas here are called tuberculoma, forming cavities in the lungs and spread to the bronchi,so it will be very infectious and transmitted by coughing,

5 it can also spread to LLL (lower lung loop), upper airways, bladder, skin (Lupus vulgaris) and bladder (more spread and infectivity). What about the remaining 10%? (those who are immunocompromised) Secondary TB arises from the primary TB directly which gives rise to the serious manifestations including meningitis, pott s disease (spine), urogenital and skin involvement. If a focus of infection ruptures into a blood vessel, bacteria are disseminated throughout the body, This, is known as miliary tuberculosis. (it is when bacteria reach the bloodstream, dissemination throughout the body) - Immunocompromised (10%): primary TB> secondry TB>miliary TB (in some cases). - Immunocompetent (90%): primary TB (granuloma)>latent TB>post-primary TB (tuberculoma). Extra note: Infection is different from disease. Infection is producing a focus of organisms (e.g.: bacteria) which may or may not cause tissue damage (i.e, disease), as we said before, when the bacteria (mycobacteria/ tubercle bacilli) remain dormant, the person is infected but does not have the active disease and therefore cannot transmit bacteria to others. In other words, if there was no reactivation of these bacteria or reinfection, the mycobacteria stop at the latent stage and the person will not develop post-primary TB) it is as if these bacteria are kept sleeping. If this person was lucky enough, the bacteria might remain dormant forever. (special thanks to Kumar, Abbas and Aster) Clinically: The following factors increase the likelihood that a patient will have tuberculosis (TB): o HIV infection o History of prior TB treatment (especially if there was no compliance).

6 o TB exposure, Travel to or emigration from a TB endemic area. o Homelessness, shelter-dwelling, incarceration (malnutrition). Symptoms Classic features associated with active TB are as follows: Cough Weight loss/anorexia Fever Night sweats Hemoptysis (coughing up of blood) Chest pain Diagnosis: Diagnosis of post- primary found in upper lung loop :/ (According to Greenwood: For unknown reasons, reactivation or reinfection tuberculosis tends to develop in the upper lobes of the lungs) - Labrotary diagnosis: o Stain: Acid fast stain (Ziehl Neelsen stain) o Culture 6-8 Weeks on LJ less time in liquid medium o Interferon Gamma interferon o PCR (polymerase chain reaction) - History and examination: o Chest x-ray (CXR). o PDD (purified protein derivative) also known as, Mantoux test/ tuberculin test Weeks post infection, an antigenic part of the mycobacteria is injected intradermally, a delayed hypersensitivity in skin occurs 2-3 days after exposure to the antigen whether it is an active infection (that will cause Tuberculosis), vaccine (BCG), environmental mycobacteria (from environment, non-tuberculous mycobacteria).

7 IGRT? interferon gamma release test is promising, though not without problems of specificity, it detects interferon-γ-producing peripheral blood T cells that respond to antigens present only in the bacteria of the active infection. (not environmental or BCG) (to whom it may concern, since we have much time, and we have nothing to do except Micro, The doctor said: read more about IGRT, well, if we found a question in our exam about it, our reference in this course would be anything on Earth but not Greenwood( Back to the PDD test: according to the tuberculin skin test reaction, if the diameter was 5 in immunocompromised people, the result would be a positive test. If the diameter was 15, the result would be positive in any person. (The only thing, the doctor said about this table( Management: Isolation: (isolating a patient in a room to prevent him from transmitting the disease to others outside the room). Combination of medicines, DOTS

8 (DOTS: Directly Observed Treatment Short-course, a strategy to reduce TB cases, in DOTS healthcare workers observe patients as they take their anti- TB medicines, compliance is really important) Treatment: (1st line anti TB) 4 drugs are used for 6 months (first 2 months of REFINA ((rifampicin & isoniazid) +Ethambutol and Pyrazinamide) (the following 4 months, we use only REFINA ((rifampicin & isoniazid))) (2nd line treatment in MDR (multi-drug resistance): Macrolides, Fluroquinilones, aminoglycosides, cycloserine... (3rd line treatment) Linezolid, rifabutin, arginine, vitamin D.. Note: if there was resistance to the first line, second line treatment is used Prevention: by BCG *Bacille Calmette Guérin* it is a life attenuated vaccine, it doesn t kill mycobacteria, it keeps them viable (alive) BCG vaccine has a documented protective effect against meningitis and disseminated TB in children. remember: children s immunity is weak- Mycobacterium leprae stained by Acid fast aerobic Intracellular bacilli

9 similar to M. Tuberculosis (Leprosy bacilli resemble tubercle bacilli in their general morphology) fat in cell wall, M. leprae has a characteristic surface lipid that can be extracted from it. It causes leprosy (Hansen s disease) chronic granulomatous disease principally affecting the skin, mucous membrane, peripheral nervous system and anterior chamber of eyes. The infection often causes severe disfigurement and deformity, it might lead to loss of sensation since peripheral nervous system is affected. Approximately 2 million cases worldwide; Africa, Asia and south America (India, Nepal, Tanzania, Brazil, Madagascar, Mozambique) MOT (mode of transmission): Inhalation (respiratory droplets) Incubation period on average is 4-8 years (1-30 years) Pathogenesis: (determined by the immune response) Brief bacteremic phase Binds to macrophages and Schwann cells immune response Clinically: Thickened lesions of skin / nodules Nerve thickening and Loss of sensation (muscle weakness, tissue /organ and nasal septum destruction, ulcers...) Disfigurement and mutilation Classification (types of leprosy) 1) Tuberculoid (Paucibacillary) leprosy o There are Few skin lesions ( less than 5 lesions) o Usually no acid fast bacilli seen in the lesions 2) Lepromatous (Multibacillary) leprosy o skin lesions ( more than 5)

10 o Many acid fast bacilli seen in lesions o More in cold areas (nose, ear, knees, elbow and buttocks) o Leonine facies = (a lion-like face) 3) Borderline leprosy Note : it is important to know whether it is a multibacillary or paucibacillary, for the selection of treatment. Diagnosis Specimens: Full thickness skin biopsy, skin scrapings and nasal smears (trivial extra: tuberculosis specimen is certainly sputum) - Acid fast staining and histological examination: Not only for diagnosis but Also for diseases classification and therapy monitoring - Molecular techniques (probing and PCR which is Promising - Culture: not available in vitro (intracellular) Grown in mice footpads, athymic mice and in Armadillo Armadillo This animal has therefore provided sufficient bacilli Treatment: - Effective treatment is available: 1) Paucibacillary Dapsone + Rifampicin 6 months 2) Multibcillary Dapsone+Rifampicin+Clofazamine 12 months Sorry for any mistake, writing micro sheets ain t that easy, I was being so sweet while writing this sweet sheet of the sweetest course of this semester, which is being taught by the super-sweet doctor