Lecture 3 Gram Positive Bacteria (Part 2) PDF

Gram Positive Bacteria (Part 2) ReCap…Gram Positive Bacteria The bacteria described is Gram- positive, characterized by a cell wall made primarily of peptidoglycan and the absence of an outer membrane found in Gram-negative bacteria. Firmicutes, commonly found in the GI tracts...

Gram Positive Bacteria (Part 2) ReCap…Gram Positive Bacteria The bacteria described is Gram- positive, characterized by a cell wall made primarily of peptidoglycan and the absence of an outer membrane found in Gram-negative bacteria. Firmicutes, commonly found in the GI tracts of mammals, include bacteria like Staphylococcus, Streptococcus, and Lactobacillus, which play roles in both human health and food production. Focused on Lactobacillus….this lecture will explore the Streptococcus spp. Genus Order Phylum (Firmicutes) Or NEW name (click) Bacillota Pg. 531 Firmicutes: Lactobacillales Streptococcus and Other Cocci Two groups of Streptococci: S. pyogenes (strep throat) and S. mutans (Dental caries) Blood agar hemolysis is diagnostic Beta-hemolysis (complete red blood cell hemolysis) diagnostic for S. pyogenes (produces Streptolysin) Alpha-hemolysis is diagnostic for viridans group Streptococcus viridans group composed of several different bacteria: (Latin Viridans = “Green”) S. anginosus S. mitis (sounds like metus) S. sanguinis S. salivarius S. mutans S. gordonii S. oralis Streptolysin Streptolysin is produced by Streptococcus bacteria, particularly Streptococcus pyogenes, which is a Group A Streptococcus (GAS). There are two types of streptolysins produced by these bacteria: 1.Streptolysin O (SLO) – Oxygen-sensitive and responsible for hemolysis under anaerobic conditions. 2.Streptolysin S (SLS) – Oxygen-stable and causes hemolysis under aerobic conditions. Both types contribute to the bacteria's ability to lyse red blood cells (beta hemolysis) and evade the immune system. Streptococcus viridans The viridans group consists of Streptococci that are typically part of the: normal flora of the human mouth, gastrointestinal tract, and urogenital tract. They are known to cause alpha-hemolysis (partial hemolysis) on blood agar. These bacteria are considered low-virulence pathogens but can sometimes cause serious infections, such as endocarditis, Streptococcus mutans, in particular, is also associated with dental caries (tooth decay).  Lactobacillus Streptococcus mutans Cheek cell Cheek cell nucleus Blood Agar Microflora of oral cavity A swab sample of the oral cavity on Blood Agar Firmicutes: Lactobacillales Streptococcus (con’t) Gram positive cocci approximately 0.5-1.2um in diameter Arrangement is in chains or pairs Facultative anaerobic (both with or without Oxygen). As mentioned before the to differentiate at the species level of the streptococcus, researchers can use the type of Hemolysis (Alpha, Beta, Gamma) which is a reaction to the red blood cells. For example the Streptococcus pyogenes is beta hemolytic, S. pneumonia is alpha hemolytic and Enterococcus faecalis is gamma hemolytic. S. pyogenes Firmicutes: Lactobacillales Streptococcus hemolysis which is lysis of erythrocytes (RBC) on the blood agar medium by enzymes Hemolysin (toxin) released by the organism is a useful identifying characteristic of streptococci. In 1934, streptococci were further classified in the name of Lancefield grouping, based on the presence of group-specific wall polysaccharides on the bacterial surface. Rebecca Lancefield (1895–1981), that divides streptococci into serotype groups based on the bacteria’s antigens known as Lancefield antigens. There are many different serological groups that have so far been identified A-H, K-V. Grp A Streptococcus (GAS) as known as Streptococcus pyogenes has the most clinical Question??? Q: Are there any bacteria within the Lancefield Group A typing other than S. pyogenes? No, within the Lancefield Group A classification, Streptococcus pyogenes (Group A Streptococcus) is the only bacterium included. The Lancefield grouping system, developed by Rebecca Lancefield, is a method of classifying beta-hemolytic streptococci based on the specific carbohydrate antigens found on their cell surfaces.  Virulence factors of GAS Figure 31.10 Necrotizing Fasciitis Madigan et al. Group A Streptococcus (GAS), specifically Streptococcus pyogenes, has several virulence factors that allow it to invade host tissues, evade the immune system, and cause various infections ranging from mild pharyngitis (strep throat) to life- threatening conditions like necrotizing fasciitis and toxic shock syndrome. Necrotizing Fasciitis (Flesh eating disease). A serious disease caused by group A Streptococcus, sensationalized by the news media. It results in loss of muscle and fat tissues, organ failure, and death in about 20% of patients. Treatment is usually IV board spectrum antibiotic and worse case amputation. Virulence Factors of GAS 1. M Protein A major surface protein that inhibits phagocytosis by preventing complement deposition and opsonization. Allows the bacterium to adhere to host cells and contributes to immune system evasion. 2. Hyaluronic Acid Capsule The capsule mimics human hyaluronic acid (a form of molecular mimicry), allowing GAS to evade the immune system by hiding from phagocytes. Prevents recognition by immune cells, aiding in immune evasion. Virulence Factors of GAS 3. Streptolysins (S and O) (mentioned previous slide) Streptolysin S (SLS): Oxygen-stable hemolysin responsible for beta-hemolysis on blood agar plates, leading to the destruction of red and white blood cells. Streptolysin O (SLO): Oxygen-sensitive hemolysin that also lyses cells, including red blood cells, white blood cells, and platelets, contributing to tissue damage and inflammation. Virulence Factors of GAS 4. Streptococcal Pyrogenic Exotoxins (SPEs) Includes SPE-A, SPE-B, SPE-C, and other superantigens that can cause: Streptococcal toxic shock syndrome (STSS): Massive immune activation leading to shock. Scarlet fever: Characterized by a rash and systemic toxicity. These toxins can also contribute to necrotizing fasciitis and other severe infections. 5. Streptokinase https://www.rxlist.com/streptase-drug.htm Converts plasminogen to plasmin, which breaks down fibrin clots. This allows the bacteria to spread by dissolving the host’s blood clots that would otherwise wall off the infection. Virulence Factors of GAS 6. DNases (Streptodornase) Degrades DNA from dead host cells in pus, reducing the viscosity and allowing the bacteria to spread more easily through tissues. 7. C5a Peptidase Degrades C5a, a complement component involved in attracting immune cells (chemotaxis). This helps GAS evade neutrophil recruitment and immune attack. 8. Hyaluronidase Breaks down hyaluronic acid in connective tissues, promoting the spread of the bacteria through tissues (often referred to as a "spreading factor"). Virulence Factors of GAS 9. Adhesins Surface proteins (such as fibronectin-binding proteins) that allow GAS to attach to host tissues, particularly the throat, skin, and other epithelial surfaces. 10. SpeB Protease A cysteine protease that degrades host proteins, including immunoglobulins and complement components. It also contributes to tissue destruction and immune evasion. 11. Autoantigen Production Some virulence factors of S. pyogenes (such as M protein) can trigger autoimmune reactions, leading to conditions like rheumatic fever and post-streptococcal glomerulonephritis.  Summary of the Virulence Factors of GAS (S. pyogenes) Streptoc occus pyogenes The M protein inhibits phagocytic functions in human tissues and fluids Other Group A Streptococcal Diseases Pharyngitis. A sore throat caused by streptococci, commonly called “strep throat,” is a type of pharyngitis, or inflammation of the pharynx. Scarlet fever bacterial infection caused by S. pyogenes, characterized by a red rash, fever, and sore throat, commonly affecting children. Rheumatic fever is a potential complication of S. pyogenes pharyngitis or of scarlet fever in which inflammation leads to damage of heart valves and muscle. The damage may be due to cross-reactive immune responses. Streptococcal toxic shock syndrome (STSS) is a rare but severe bacteremia followed by intense pain and organ failure, and over 40% of patients die. Cellulitis is a soft tissue infection that penetrates deeper into the skin Group A Streptococci (GAS) – Final thoughts… Streptococcus pyogenes, is one of the most important human pathogens which causes Streptococcal sore throat and skin infections S. pyogenes is inhibited by the antibiotic bacitracin, an important diagnostic criterion. A condition called Necrotizing fasciitis caused most commonly be S. pyogenes is sensationalized by the news as the “Flesh Eating Bateria”. This was characterized by Hippocrates in the 5th century. We now know that there may be a number of bacteria acting in concert to cause this condition; S. aureus and Clostridium perfringens. Enzymes secreted by GAS damage body tissues Firmicutes: Nonsporulating Bacillales and Clostridiales Key genera: Listeria Sarcina Clostridium Listeria Genus Sarcina Order Phylum Clostridium buh-SILL-ay-leez Firmicutes: Nonsporulating Bacillales and Clostridiales Key genera: Listeria, Staphylococcus, Sarcina Listeria (Genus) in order Bacillales found widely in soils, opportunistic pathogen that causes foodborne illness (An organism that causes disease ONLY in the absence of normal host resistance) gram-positive, catalase-positive, rod-shaped, facultatively aerobic chemoorganotrophs (obtain energy by oxidizing organic compounds such as fats, carbohydrates and proteins) Acid-, salt-, and cold-tolerant and facultatively aerobic often grow well at low temperatures (e.g., in refrigerated foods) Growth range 1oC to 45oC, Known to cause Listeriosis by Listeria monocytogenes. This is due to improperly sanitized equipment in meat and animal product or for produce from the contaminated water used. Each year ~48 million people in the US get sick from contaminated food. RTE (Ready To Eat foods) Growth at LOW temperature Firmicutes Listeria (con’t) Mortality rate is 16 percent, primarily affect the elderly, pregnant women, newborns, and adults with weakened immune systems May lead to bacteremia and meningitis (swelling of the membrane in the brain) Food contaminated with Listeria monocytogenes may not look or smell spoiled but can still make you sick. Symptoms can include vomiting, nausea, persistent fever, muscle aches, severe headache and neck stiffness. Pregnant women, the elderly and people with weakened immune systems are particularly at risk. So far this year, at least 21 food items from different companies have been recalled by the Canadian Food Inspection Agency (CFIA) due to Listeria concerns. Listeria monocytogenes is a type of bacteria commonly found in soil and it causes food-borne illnesses in humans. It is wide spread in nature. For most RTE foods, it is the “post-processing contamination” that takes place. ational Center for Emerging and Zoonotic Infectious Diseases (CDC 2013) Route of Transmission: Listeriosis: (Click) Caused by Listeria monocytogenes, a Foodborne illness. Once ingested, if the bacteria evade the host immune responses then they will be taken up by the intestinal phagocytic cells where the BIG problem will begin (read section 33.13) Once inside the phagocytic cells, the bacteria release the toxin Listeriolysin which can eventually lysed the cell thereby release Listeria bacteria into the cytoplasm. The bacterial cells then become covered with host cell actin (a globular multi-functional proteins that form microfilaments in cytoskeleton) that assists in their movement to the cell periphery. Filopods facilitate transfer of Listeria bacteria to neighboring host cells, where the cycle repeats. Click on the title “Listeriosis” for a short video of the binding of the bacterium to the epithelial cell. Fluorescently stained cells of Listeria monocytogenes (red) showing actin- assisted motility inside a eukaryotic cell (actin stains green, and the host cell nucleus is blue). The dashed white line labels the boundary Firmicutes Sarcina In the order of Clostridiales Catalase negative Obligate anaerobe, and are exceptionally acid tolerant thriving in highly acidic conditions such as that of the stomach. A notable species is the Sarcina ventriculi. Which is found in the humans suffering from pyloric ulceration. Organism occurs more in females than male, 68% to 31%, respectively https://doi.org/10.5858/arpa.2016-0028-RS FirmicutesClostridiales Clostridium C. difficile C. botulinum C. tetani C. perfringens END….