Mycobacteria PDF

Mycobacteria Mycobacteria are a genus of bacteria that are characterized by their waxy cell walls. This unique feature gives them a distinctive appearance under a microscope and makes them resistant to many disinfectants. by Heba Rashed ILOs Classification of Mycobacteria...

Mycobacteria Mycobacteria are a genus of bacteria that are characterized by their waxy cell walls. This unique feature gives them a distinctive appearance under a microscope and makes them resistant to many disinfectants. by Heba Rashed ILOs Classification of Mycobacteria Transmission and Pathogenesis Mycobacteria are classified Mycobacterium tuberculosis based on their habitat, host, (MTB) is spread through and biochemical airborne droplets from properties. infected individuals. Infection occurs through inhalation. Lab Diagnosis Clinical Features Diagnosis involves Clinical features of microscopic examination tuberculosis include cough, of sputum, culture, fever, night sweats, and biochemical tests and weight loss.  Definition of Mycobacteria Rod-shaped Bacteria Waxy Cell Wall Difficult to Treat Mycobacteria are a genus of aerobic They are known for their waxy cell This unique cell wall also makes them bacteria that possess a unique cell wall wall, which gives them a difficult to treat and contributes to structure, making them resistant to characteristic acid-fastness. their ability to persist in the staining and disinfection. environment and within host cells.  Classification of Mycobacteria Mycobacterium tuberculosis Atypical Mycobacteria Complex (MTC) This complex includes several species, Also known as non-tuberculous including M. tuberculosis, M. bovis, and mycobacteria (NTM), these are a diverse M. africanum. group. They are often found in the environment These species are responsible for and can cause infections in humans, tuberculosis in humans and animals. particularly in those with compromised immune systems. Non-Cultivable M. leprae is a unique species of mycobacteria that cannot be grown in artificial media. This makes it challenging to study and diagnose leprosy.  Classification based on Habitat Facultative/ Free-Living Obligate Pathogens Opportunistic Saprophytes Pathogens These species These species can exist These species primarily exist exclusively thrive independently but become in the environment, often pathogenic under specific in a living host, found in soil, water, or conditions, often when the host's relying on the decaying matter. They don't immune system is weakened. host's resources for typically infect humans unless M. avium complex, a group of survival. introduced into the body closely related mycobacteria, is an 1.M. tuberculosis (MTB) 1.M. asmegmatis through wound or other example of an opportunistic 2.M. leprae pathogen. They can cause lung means. 2.M. gordonae disease, especially in people with weakened immune systems.  Classification based on 1 Tubercle Bacilli Host 2 Bovine Bacilli Mycobacterium Mycobacterium bovis (M. tuberculosis (MTB) bovis) is a species primarily infects humans, causing found in cattle. This bacterium is tuberculosis. This a rare cause of tuberculosis in bacterium is responsible humans. for the majority of TB cases worldwide. 3 Lepra Bacilli Mycobacterium leprae is the causative agent of leprosy, a chronic infectious disease that primarily affects the skin, peripheral nerves, upper respiratory tract, and eyes.  MYCOBACTERIUM TUBERCULOSIS COMPLEX The Mycobacterium tuberculosis complex is a group of closely related bacteria that are the primary cause of tuberculosis. M. tuberculosis Characters Morphology Growth Characteristics Cell Wall Composition M. tuberculosis is a slightly M. tuberculosis multiplies slowly, M. tuberculosis has a thick, waxy lipid curved, rod-shaped bacillus. The with a generation time of cell wall that provides resistance to bacilli are about 0.2 - 0.5 microns approximately 18-24 hours. This slow various environmental factors. The in diameter and 2 - 4 microns in growth rate contributes to the lengthy cell wall plays a crucial role in the length. They are acid-fast, duration of tuberculosis treatment. bacterium's virulence and survival meaning they resist within the host. decolorization by acidified alcohol after prolonged Route of Transmission Mycobacterium tuberculosis is primarily transmitted through the air, specifically via droplet nuclei. These tiny droplets, measuring 1 to 5 micrometers in diameter, are released into the air when an infected individual coughs, sneezes, speaks, or sings. While droplet nuclei can remain suspended in the air for extended periods, they can also be generated during procedures involving infected lesions or clinical specimens. This poses a risk to healthcare professionals handling such materials. The inhalation of these droplets can lead to infection, particularly in the lungs. Pathogenesis Postprimary Primary Infection Tuberculosis Subsequent disease The initial infection in a previously with _M. sensitized person, either from an tuberculosis_ is exogenous source or known as a primary by reactivation of a primary infection, is infection. known as postprimary Pathological Features tuberculosis. Both primary and postprimary tuberculosis exhibit quite different pathological features. Clinical Features Tuberculosis (TB) is a disease that can affect different parts of the body. The majority of TB infections involve the lungs, known as pulmonary TB. However, TB can also affect other organs, known as extrapulmonary TB. Some common examples of extrapulmonary TB include TB of the lymph nodes, brain, kidneys, and bones. While less common than pulmonary TB, extrapulmonary TB can still be very serious. Symptoms and Signs of Tuberculosis Cough Shortness of BreathFever and Night Chest Pain Sweats Cough is a common Shortness of breath is a Chest pain is a common symptom of common symptom of Fever and night sweats symptom of tuberculosis. It can be tuberculosis. It is are common symptoms tuberculosis. It is dry or productive. It can caused by damage to of tuberculosis. The caused by inflammation be accompanied by the lungs. fever is often low-grade of the pleura, the lining blood. Patients often and occurs in the of the lungs. report cough lasting afternoon or evening.  Extrapulmonary Tuberculosis Spread of TB Commonly Affected Areas When Mycobacterium tuberculosis Common sites include the genitourinary spreads beyond the lungs, it can affect system, meninges, gastrointestinal tract, various organs and systems throughout skin, lymph nodes, bone marrow, spine, the body. This disseminated form of TB is and joints. called extrapulmonary TB. Extra pulmonary TB can present with Tuberculosis bacteria can travel through various symptoms depending on the the bloodstream, reaching different parts affected organ or system. of the body. Diagnosis of TB Infection 1. Non-Specific Tests 2. Radiological 3. Hypersensitivity Examination to TB Antigens Non-specific tests include Chest X-ray is an important Tuberculin skin test elevated erythrocyte diagnostic tool, revealing (TST) and QuantiFERON- sedimentation rate (ESR) characteristic patterns of TB Gold (QFT) are and complete blood count lung involvement in TB commonly used to detect (CBC) with monocytosis infection. TB infection. and neutrophilic leukocytosis. 4. Histopathological Examination 5. Bacteriological Examination Biopsy of lymph nodes reveals granulomatous Direct smear microscopy using Ziehl- inflammation with caseation necrosis, a hallmark of Neelsen stain and culture are essential TB infection. for confirming TB infection.  Bacteriologic Examination Sputum Blood Urine Biopsy Urine samples are useful A biopsy of affected Sputum is the most Blood cultures can help for diagnosing TB in tissue, such as lung common specimen for detect TB in cases of cases where the tissue, lymph nodes, or diagnosing pulmonary miliary TB or when the infection has spread to other organs, can be TB. It contains the infection has spread to the kidneys. examined for the bacteria responsible for the bloodstream. presence of TB bacteria. the infection. The type of specimen collected depends on the site of infection. For example, sputum is typically used for pulmonary TB, while biopsies and aspirates are used for extrapulmonary TB. Examination of Direct Smears Advantages Disadvantages Rapid The Ziehl-Nielsen stain is Specific less sensitive than other methods, such as culture, Inexpensive for detecting AFB. It Ziehl-Nielsen Stain requires at least 10,000 organisms per milliliter of The Ziehl-Nielsen stain is a specific stain used to identify acid- sample to be positive. fast bacilli (AFB) in a sample. AFB are characterized by their resistance to decolorization with acid alcohol. This resistance is due to the presence of mycolic acids in the cell walls of AFB. Culture Advantages and Limitations Sensitivity Specificity Culture is highly sensitive, Culture is highly specific, detecting low bacterial loads. accurately identifying This helps diagnose infection Mycobacterium species. This even with limited bacilli. is crucial for accurate diagnosis and treatment. Time Consuming Culturing Mycobacterium takes several weeks. This can delay diagnosis and treatment, impacting patient care. Types of Media Lowenstein- Middlebrook Media BACTEC Media MGIT Jensen Media Available in both agar and Automated radiometric Automated non- Egg-based media is a broth forms, and is system provides rapid radiometric system for traditional method for designed for rapid growth detection of detecting mycobacterial cultivating M. of mycobacteria. mycobacterial growth. growth based on tuberculosis. fluorescent detection of Contains a variety of Contains a defined The system measures the oxygen consumption. nutrients including nutrient composition, production of CO2 by glycerol, asparagine, and ensuring consistent growing mycobacteria The system is designed to malachite green to growth and facilitating the and reports the results in be safe and support the growth of use of selective agents a short period of time. environmentally friendly, mycobacteria. like pyrazinamide and reducing the risk of ethambutol. radioactive waste. Middlebrook Media Middlebrook media is a type of culture medium used for the growth of mycobacteria. It is a solid medium that is based on an agar base. Middlebrook media is enriched with a variety of nutrients, including oleic acid, albumin, dextrose, catalase, glycerol, and malachite green. These nutrients provide the mycobacteria with the essential components they need to grow. Middlebrook media is often used in combination with other diagnostic tests, such as the Ziehl-Neelsen stain, to help confirm the diagnosis of tuberculosis. Middlebrook Media Advantages and Disadvan Advantages Disadvantages Middlebrook media provides rapid results and enables the Middlebrook media is expensive, and not suitable for follow-up identification of the causative organism, which is important for studies due to its susceptibility to contamination. targeted treatment. The media also provides information about the sensitivity of the organism to different antibiotics. BACTEC MGIT (Mycobacteria Growth Indicator The BACTEC MGIT system is a rapid and automated method for detecting mycobacteria in clinical specimens. It utilizes a modified Middlebrook OADC medium containing oleic acid, albumin, dextrose, and catalase. The medium also includes a silicon film that acts as a fluorescence indicator. When viable mycobacteria are present in the tube, they consume oxygen, leading to a decrease in the fluorescent output of the sensor. The bottom of the tube fluoresces when exposed to ultraviolet light, indicating the presence of mycobacteria. The MGIT system can detect growth in as little as 5 days, making it a more rapid method compared to traditional culture techniques.  Molecular Techniques Molecular Probes (NAP) PCR (Polymerase Chain Reaction) This technique allows for the PCR is a powerful tool for detecting identification of mycobacterial growth Mycobacterium tuberculosis directly in from both solid and liquid media. Probes clinical samples, even before culture are used to detect and identify specific results are available. This technique is DNA sequences, enabling the used to amplify specific DNA sequences, identification of Mycobacterium allowing for the rapid and sensitive tuberculosis and other mycobacterial detection of the pathogen. PCR also has species. the capability to detect drug resistance mutations. Sample Collection and Handling Sterile Technique Use aseptic technique during collection to avoid contamination from other microorganisms. Appropriate Specimen Select specimen type based on suspected infection site, e.g., sputum, blood, urine, or tissue. Proper Labeling Label samples clearly with patient information and date of collection for accurate identification. Transport Media Use specialized transport media to maintain viability and prevent overgrowth of other organisms. Refrigeration Refrigerate samples promptly to preserve mycobacteria for optimal culture and testing. Cultivation of Mycobacterium Growing mycobacterium in a lab requires specific conditions and media. The goal is to create an environment that promotes their growth, allowing for identification and testing. Media Selection 1 Use selective media designed for mycobacteria, such as Löwenstein-Jensen (LJ) or Middlebrook 7H10. Incubation 2 Incubate at 35-37°C, with a 5-10% CO2 atmosphere. Growth Time 3 Mycobacteria grow slowly, often taking 2-8 weeks for visible colonies to form. Safety Precautions 4 Always handle mycobacterium cultures in a biosafety level 3 (BSL-3) laboratory to prevent exposure. The chosen media and incubation conditions are crucial for the successful cultivation of mycobacteria, ensuring proper growth for accurate identification and further analyses. Growth Requirements Temperature Oxygen Nutrients Time Mycobacteria are typically Most mycobacterial They require specific Due to their slow growth slow-growing organisms. species are aerobic, nutrients, including rates, cultures need to be They thrive at requiring oxygen for glycerol, fatty acids, and incubated for several temperatures ranging growth. amino acids. weeks, sometimes from 35°C to 37°C. months, to achieve visible growth.  Non-Specific Tests Non-specific tests are used for screening of tuberculosis. They are not directly measuring Mycobacterium tuberculosis but measure the immune response to it. Tuberculin tests, such as the Mantoux test or PPD, are the most common non-specific test. They are based on the principle of delayed-type hypersensitivity. TST Interpretation The tuberculin skin test (TST) is a valuable diagnostic tool for tuberculosis infection. It assesses an individual's immune response to the Mycobacterium tuberculosis (Mtb) antigen. A positive TST reaction, indicated by an induration greater than 10mm, suggests exposure to Mtb. A negative TST, with an induration less than 10mm, suggests no prior Mtb infection. However, factors like BCG vaccination or allergies can influence the results. Tuberculin Skin Test Advantages The tuberculin skin test (TST) is easy to administer, safe for most individuals, and relatively inexpensive. It is a valuable tool for detecting latent tuberculosis infection (LTBI). Disadvantages The TST has limitations, including the need for multiple patient visits, low specificity due to cross-reactivity with environmental mycobacteria, and potential influence by prior BCG vaccination. Limitations The TST does not reliably differentiate between active TB and LTBI. It also has a high rate of false positives and false negatives. Therefore, it is not ideal for screening individuals in all situations. Interferon Gamma Release Assays: Quantiferon-GOLD Blood Test Immune Response Quantiferon-GOLD is a blood It measures the immune test to detect latent TB response to specific TB infection. antigens in a blood sample. Sensitivity and Advantages Specificity Results within 24 hours It has high sensitivity and No need for a second visit specificity for detecting latent Less risk of false positives TB infection. Vaccine Bacille Calmette-Guérin (BCG) BCG is a live attenuated vaccine derived from a strain of Mycobacterium bovis. It is administered via intradermal injection in the deltoid. BCG is a compulsory vaccination for newborn infants. It helps prevent miliary and disseminated TB. BCG vaccination does not prevent TB infection. BCG is not recommended for individuals with an impaired cell-mediated immune response such as infants with primary immunodeficiency, HIV-infected individuals, burn patients, or patients with extensive, active skin disease. CONTROL Tuberculosis control requires a multifaceted approach to prevent and treat infections. Key strategies include preventing transmission, early detection, and effective treatment. The WHO’s "End TB Strategy" aims to reduce TB deaths by 95% and incidence by 90% by 2035. Treatment of TB Treatment of tuberculosis is a long-term process that requires a combination of drugs. The treatment regimen aims to eliminate Mycobacterium tuberculosis from the body and prevent further transmission. The duration of treatment varies depending on the patient's condition and response to therapy. Treatment for active tuberculosis typically involves a multidrug regimen consisting of four primary drugs: isoniazid, rifampin, pyrazinamide, and ethambutol. These drugs work by targeting different metabolic pathways in the Mycobacterium tuberculosis bacteria. The effectiveness of treatment relies on the patient's adherence to the prescribed medication regimen. Poor adherence can lead to drug resistance and treatment failure. Thank You This concludes the presentation on Mycobacterium Tuberculosis. We hope you enjoyed the information shared. For further questions or inquiries, please contact Dr. T.V. Rao MD.