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RS Microbiology

Respiratory System Microbiology - Bacteriology- Fungal

QuestionAnswer
How many cases of TB are reported yearly? 10 million
How many deaths due to TB happen yearly? 2-3 million
What percentage of TB deaths occur in developing countries? 95%
In patients with HIV, what is the second most common infectious cause of death? TB
Characteristics of tubercle bacilli: 1) Acid fast 2) Found in animals and humans 3) Grow slowly 4) Resistant to dryness and acidity 5) Susceptible to UV and heat
Characteristics of M. tuberculosis: 1) Most common cause of human TB (95%) 2) Causes resp. infection 3) One positive patients may spread it to hundreds 4) People of all ages affected 5) Mostly children with malnutrition
Optimal conditions for transmission include: Overcrowding Large cities Poor conditions Low standard public hygiene
90% of pulmonary TB is Primary tuberculosis
Characteristics of primary TB: 1) In Children, mainly 2) Asymptomatic 3) Infect alveolar macrophages 4) Small lung lesions 5) Fibrosis, Calcification, Hypersensitivity
A person infected with TB is positive for: Tuberculin Skin Test
How is the identification of TB done? Aspirate from nose (sputum sample) Identify causative agent using acid fast bacilli stain (Ziehl Neelsen stain) Culture bacteria Sensitivity tests
Route of transmission of TB by: Inhalation
A positive tuberculin test result is when the patient shows an erythematous skin lesion at the site of infection. In the case of a true infection, the lesion is: Over 1 cm in diameter
How do we perform the Tuberculin Skin test? Culture M. bovis 50 times in order to reduce pathogenicity Cultured cells are purified extracting cell wall components Inject purified components at a concentration of 0.5 IU on the forearm If there is a positive reaction after 48 hours - positive
A positive tuberculin test is not pathognomonic for TB; other tests are used to confirm the findings. These include: Isolation of the microorganism via culture (sputum or other bodily fluids) X-ray Clinical features (they vary from one person to the other; thus, it is hard to decide based upon them)
Characteristics of M.bovis: 1) Can infect humans 2) Starts in the GI 3) Transmitted through contaminated foods 4) Similar to M. tuberculosis
Characteristics of M. Kansasii: 1) Discovered in Kansas 2) Related to contamination in soil 3) Produces a yellow pigment under light 4) Only establishes infection in the immunodeficient (30% of HIV)
Characteristics of M.marinium: 1) Related to aquatic organisms 2) Survives low temperatures 3) Skin ulcers known as aquarium granuloma 4) It often infects fish and then infects humans
Characteristics of M. ulcerans: 1) Found in tropical and subtropical areas 2) It produces localized infection
Growth pattern of M. TB and Bovis: 2-8 weeks
Growth pattern of Atypical mycobacterium: 1-3 weeks
Which mycobacterium cannot disseminate to other parts of the body? 1) Ulcerans 2) Avium 3) Marinium
Which strains produce pulmonary symptoms? 1) M. Kansasii 2) Typical M. TB
Stages of detecting a mycobacterium: Direct smear from skin or sputum followed by staining Culture (report slow or rapid growth) Biochemical tests and resistance tests. PCR is not accurate because it only indicates the presence of an acid fast bacillus without indicating the type
Duration of treatment: Normal TB: 3-6 months (200 JD’s cost) Multiresistant: 1-3 years. (10,000 JD’s cost) Vaccine: BCG
Characteristics of Nocardia: 1) Gram +ve dimorphic bacillus 2) Slow growers, grow best at room temp. 3) RTI, kidney, meningitis, and brain abscesses 4) Associated with infection during dialysis 5) Skin lesions
Treatment for Nocardiosis: Cotrimoxazole or aminoglycosides We do not give typical anti TB agents
What are the two types of yeast infections? 1) Endogenous 2) Exogenous
The endogenous infection is related to the presence of normal fungal flora in our bodily cavities This type of yeast is called candida
When yeasts are transformed they go from: Non-filamentous to filamentous (pseudohyphae)
Characteristics of yeast: The tip of the filament attaches itself to certain receptors on the mucosa causing an infection in the form of a biofilm We use a wet preparation to demonstrate the presence of filaments The filaments are a proof of the presence of pathogenic yeast
Which candida is associated with the majority of clinical infections? Albicans
Tropicalis does not produce spores, it produces: Filaments
Features of Candidiasis: 1) Localized infection 2) Systemic candidiasis is uncommon 3) Patients with immunodeficiency 4) The use of immunosuppressant drugs produces the same effect of AIDS. 5) Systemic candidiasis is dangerous and lethal.
Treatment of Candidiasis: Treating systemic candiasis is not easy as it requires a very specific dosing regimen as antifungal drugs (ex. Amphotrecin) are highly toxic. For local infections we use ointments such as Nystatin
Only family of yeast which shows a capsule: Cryptococcus
Most common Cryptococcus: Neoformans
Characteristics of Cryptococcus: 1) Starts with the inhalation of this yeast 2) Lodges in the sinuses and spreads to the lungs where it forms granumolatous lesions and can cause sepsis 3) Lack of specific clinical symptoms 4) Present in small numbers of cells 5) High mortality rate
Diagnosis of Cryptococcus: X-rays and CT scans might give an impression of granulomas To detect the causative agent, we either use culture or practical tests Looking for antibodies and PCR test is useless Demonstrate the cells using India ink
Characteristics of filamentous fungi: 1) Presence of true hyphae 2) Horizontal (vegetative) and vertical (aerial) filaments 3) We can find spores (microspores or macrospores) that hold cells 4) The arrangement of spores and filaments determines helps in the identification of the fungus
There are three clinically important types of Aspergillus: Niger (black) Fumigatus(blue to green) Flavus (yellow)
Characteristic of Aspergillus spores: Widely distributed in nature Associated with dead organic material Highly resistant to harsh conditions (dryness and extremes of temperature) Spores account for more than 50% of the spores in the environment
Diseases related to Aspergillus can be divided into several categories: 1) Mycotoxicosis 2) Allergic brunchopulmonary disease 3) Release of aphlatoxin 4) Respiratory aspergilloma
Characteristics of Allergic bronchopulmonary disease: A form of allergic reaction that can end in asthma. Very common in Jordan and accounts for 5% of allergic reactions It is associated with in increase in eosinophils
Characteristics of aflatoxin release: 1) It is released from the flavus species 2) Fatal toxin (nano amounts are enough) 3) Associated with milk and nuts 4) Having a humid environment encourages the growth of spores which release this type of toxin
Characteristics of respiratory aspergilloma: 1) Pulmonary form of aspergillus infection. 2) The lung must have a TB cavity, fibrosis, or malignancy for the fungus to grow (fungus ball) 3) Destroys tissues and affects pulmonary function 4) Disseminate to the sinuses causing rhino-cerebral lesions
What is the treatment of aspergillus and other types of filamentous fungi? Surgical and chemical treatment should be used together Chemical treatment is not sufficient because you cannot give doses high enough to penetrate the whole fungus ball
Examples of dimorphic fungi: Histoplasma capsulatum Coccidioides immitis Blastomyces dermatitidis
Characteristics of Histoplasmosis and related diseases: 1) Capsulatum is not capsulated 2) The first 2 are found in bird intestines 3) If they reach the RT --> allergic reaction 4) In immunocompromised patients, the old infection might flare up producing flu like symptoms 5) Southern US 6) Meningitis
Characteristics of Blastomyces dermatitis: Infection with this organism might start as a skin infection rather that a pulmonary infection It can disseminate to other organs, including the meninges, causing a severe infection often leading to the death of the patient
Characteristics of Pneumocystic carinii: It was first thought of as a parasite; however, they discovered more related to yeasts The organism is a yeast-like cell that cannot be easily isolated from the animals or humans A rat origin is suspected
Characteristics of Pneumocystic jyroveci: 1) Discovered 10 years ago 2) Related to humans 3) Route of infection unknown 4) Disease of the young 5) Mild clinical symptoms without further complications 6) Infection rate increases with age 7) Immunocompromised patients - sepsis and meningitis
Diagnosis of Pneumocystic jyroveci: Not easily isolated in cultures Most of the identified cases were identified through a lung biopsy Stains with silver stain and Giesma stain We test for its antigen; testing for antibodies is useless
Treatment of Pneumocystic jyroveci: It can be treated with an antibacterial drug like cotromaxizole
Created by: Ulaisl
 

 



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