Microbiology Case Study III Questions and Answers 100% Correct

Microbiology Case Study III Questions and Answers 100% Correct Streptococcus Pneumoniae - what is it? Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, alpha-hemolytic or beta-hemolytic, facultative anaerobic member of the genus Streptococcus. They are usually found in pairs and do not form spores and are non-motile - causes "typical pneumonia" - causes ~30% of pneumonias - nose and throat of 30-70% of a given population can contain S. pneumoniae - highly adaptive, making humans its only natural reservoir - in an otherwise healthy adult, pneumococcal pneumonia usually involves one lobe of the lungs Streptococcus Pneumoniae - How it settles in the body and how the immune system reacts? - initial colonization is facilitated by a slippery polysaccharide capsule that allows the organism to avoid engulfment by phagocytic cells and removal by the mucociliary escalator - helps S. pneumoniae gain access to the respiratory epithelium - once these bacterium reach the epithelium, the thick capsule becomes a hindrance to attachment and changes to a thin, transparent one - the microbe then reaches the lungs and grows in nutrient-rich edema fluid of the alveolar spaces - damaged alveolar cells release chemokines that recruit neutrophils and macrophages - polysaccharide capsule of pneumococcus makes phagocytosis difficult - infiltration of granulocytes (PMN) and fluid leakage creates characteristic diffuse cloudy areas seen on x-rays - a sudden need for a larger quantity of neutrophils causes an increase in release of immature neutrophils from bone marrow. The immature neutrophils have a band-shaped nuclei called "bands" (elevated band cells indicate bacterial infection) Streptococcus Pneumoniae - Signs and Symptoms Signs: fever, rapid heart-rate, rapid breathing (tachypnea), cough with mucus, pus or blood, shortness of breath Symptoms: chills, weakness, pain with breathing Streptococcus Pneuomoniae - Transmission - airborne droplets - direct contact - 20-40% of population are asymptomatic carriers Streptococcus Pneuomoniae - Prevention - Vaccination: Pneumococcal Polysaccharide Vaccine - PPE - frequent hand-washing! - mask Streptococcus Pneuomoniae - Virulence Factors - toxins kill cells to obtain nutrients - polysaccharide capsule makes phagocytosis difficult - adhesin - attaches to host cells where it colonizes - many variations of surface proteins Streptococcus Pneuomoniae - Diagnosis - sputum test - gram-stain (Gram+) - look for slide morphology (streptococcus) - look for capsule (halo) Streptococcus Pneumoniae - Treatment - Beta-lactams (penicillin, ampicillin) - Macrolides or quinolone Mycobacterium TB - what is it? Mycobacterium tuberculosis is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis - cases on the rise in developed countries due to HIV and a growing population - does not gram stain due to thick, waxy, peptidoglycan cell wall - rapid onset (fulminant) and fatal disease among HIV patients - highly infectious, even to healthy people without HIV - thick cell wall makes it difficult to treat with antibiotics - tubercles form around site of infection - MDR found in many inter-city hospitals - causes primarily a respiratory infection but can dessimate through the bloodstream to produce abscesses in many different organ systems - infected nodules are termed "tubercles" - no animal reservoir - spread person to person through aerosolization or respiratory secretions Mycobacterium TB - Primary Disease characterized by a productive cough that generates sputum, fever, night sweats, and weight loss - these patients have ACTIVE TB and are contagious! infection risks of TB depend on frequency and duration of exposure to people with active TB disease Mycobacterium TB - Latent TB bacteria contained by the immune system often for an extended period of time can be reactivated and cause secondary TB - can be reactivated months or years after initial infection (secondary TB) - occurs in immunocompromised patients; symptoms of secondary are more serious than primary due to uninhibited replication - TB cavities are seen in 40% of patients Mycobacterium TB - Tuberculin Skin Test Indicates exposure to TB bacillus when positive. An immune system exposed to TB generates T cell-mediated response to M. TB, providing the basis for skin test (true whether they develop the disease or not) - read 48-72 hours after placement of antigen. Induration, larger than 5-15mm at injection site interpreted as positive test Mycobacterium TB - How it settles in the body? - once the species enters the body via inhalation of respiratory droplets, it travels down to the lungs where it is phagocytozed by macrophages and survive sheltered in modified macrophages - delayed-type hypersensitivity response results, and a small, hard tubercles form around the site of infection - over time, the tubercles develop into caseous lesions that have a cheese-like consistency and can calcify into hardened Ghon complexes seen on typical x-rays - trapped bacilli are usually killed by the immune system; if not they're contained by the immune system, often for extended periods of time (latent TB) Mycobacterium TB - Diagnosis - screening for TB disease involves chest x-ray, Mantoux TB skin test, interferon gamma release assays, nucleic acid amplification testing, and examination of sputum by microscopy and culture - acid-fast stain must be used for mycobacterial TB Mycobacterium TB - Treatment - 4 drug regimen (isozanoid, rifampin, pyrazimide and ethambutol) given over course of several months - MDR strains treated with nine drug regimen Mycobacterium TB - Signs and Symptoms Signs: Fever, weight loss, productive cough, abscess in lungs Symptoms: night sweats Chlamydia Trachomatis - what is it? Gram-negative-like obligate intracellular pathogen that has several serotypes infecting the reproductive tract and eye (trachoma) - most commonly reported STI in the US, but many people are unaware they're infected - 3/4 of women infected have no symptoms - major cause of nongonococcal urethrititis in US - obligate intracellular pathogens that start out as small, non-replicating infectious elementary bodies that enter target eukaryotic cells - once inside the vacuoles, begin to enlarge into replicating reticulate bodies - people at most risk: young, sexually active men and women - if left untreated, can cause pelvis inflammatory disease - men left untreated can suffer urethral and testicular infections and a serious form of arthritis Chlamydia Trachomatis - Diagnosis - samples of patients urethral discharge sent for nucleic acid amplification test (ex. PCR) to confirm diagnosis Chlamydia Trachomatis - Treatment Azithromycin and doxycycline Chlamydia Trachomatis - Replication Cycle 1) Elementary bodies bind and enter epithelial cell via phagocytosis 2) Elementary body differentiates into reticular body 3) Reticular body replicates 4) Reticulate bodies differentiate to elementary bodies and form inclusions - can attach to new epithelial cells 5) Elementary bodies are released Chlamydia Trachomatis - Signs and Symptoms Signs: unusual discharge from the urethra, spotting Symptoms: abdominal pain, pain in eye and during urination Borrelia Burgdorferi - What is it? - bacterial species in the spirochete class that cause Lyme Disease - considered diderm (double-membrane) rather than Gram+ or Gram- Borrelia Burgdorferi - Morphology - Spirochete - outer and inner membrane with thin layer of peptidoglycan in between - .3um in width; 5-20um in length - bundled periplasmic flagella set at each end that allow bacterium to move in low and high-viscosity media (related to its high virulence) Borrelia Burgdorferi - Life Cycle - circulates between Ixodes ticks and a vertebrate host in an enzootic cycle - B. burgdorferi living in a tick cannot be passed to offspring - tick larvae must feed on blood of an infected animal to acquire it - infected nymphs transmit B. burgdorferi by feeding on another vertebrate to complete lifecycle - humans are "dead-end" hosts meaning the B. burgdorferi are unlikely to continue the life cycle in humans - nymphs molt into adult ticks that feed on larger mammals that are not able to support survival of B. burgdorferi Borrelia Burgdorferi - Disease Lyme disease is a zoonotic, vector-borne disease transmitted by Ixodes tick - infected nymphal tick transmits B. burgdorferi via its saliva to human during its blood meal Once transferred into the human via tick bite, the microbe can travel rapidly via the bloodstream to any area in the bod, but prefers to grow in the skin, nerve tissue, synovium (joint lining), and the conduction system of heart Borrelia Burgdorferi - Diagnosis - bulls-eye rash and erythema chronicum migrans (rash that spreads peripherally and spares central part)