Gram +ve Bacteria 2024 PDF

Gram Positives Cocci, bacilli and filamentous  Bacteria are living forms that are micro-scopical in size (1-10 µm) and relatively simple, unicellular, in structure. Reproduce mostly asexually Anaerobic or aerobic : depending on the species, bacteria can be aerobic which means they require o...

Gram Positives Cocci, bacilli and filamentous  Bacteria are living forms that are micro-scopical in size (1-10 µm) and relatively simple, unicellular, in structure. Reproduce mostly asexually Anaerobic or aerobic : depending on the species, bacteria can be aerobic which means they require oxygen to live or anaerobic which means oxygen is deadly to them. Bacteria can be autotrophs or heterotrophs  The Gram stain, which divides most clinically significant bacteria into two main groups, is the first step in bacterial identification. Bacteria stained purple are Gram + (positive) their cell walls have thick petidoglycan and teichoic acid. Bacteria stained pink are Gram – (Negative) their cell walls have thin peptidoglycan and lipopolysaccharides with no teichoic acid. What are we concerned with? Shape of the bacteria/ Identifying factors Where it’s considered normal flora Virulence Factors –capsules? Toxins? Enzymes? Disease and presentation of illness How can we test for it? How can we treat or prevent it? Shapes  Staphylococcus Cocci in clusters; aerobic Shown on gram stain Catalase positive Three different species in family: S. aureus, S. epidermiditis, S. saprophyticus  S. aureus Gram positive cocci in clusters Catalase positive, Coagulase positive Normal flora of skin & nasal mucosa Virulence: Protein A: a part of the cell wall, binds IgG to inhibit phagocytosis Enzymes released: hemolysin, leukocidin, kinase, hyaluronidase Toxins: Toxic Shock Syndrome Toxin (super antigen – activates immune system),  Enterotoxin (pre-formed toxin in food – diarrhea, vomiting), Exfoliative (skin-exfoliating toxin) Diseases of Staph aureus: skin infections Cellulitis Impetigo Carbuncle Folliculitis Scalded-Skin Syndrome pneumonia, osteomyelitis, endocarditis, septic arthritis, abscesses, Toxic Shock Syndrome,food-poisoning, MRSA (Methicillin-Resistant Staph Aureus) alteration in penicillin binding protein. Lab Studies: morphology: gold colonies mannitol salt agar: survives high salt & metabolizes mannitol Treatment: Penicillins, Cephalosporins & Vancomycin Impetigo Osteomyelitis Folliculitis Septic Arthritis Carbuncle Impetigo Scalded Skin Syndrome Enterotoxin made by S. aureus causing food poisoning  S. epidermidis Gram positive cocci Catalase positive, coagulase negative Normal flora on skin Virulence: forms biofilms wherever it colonizes Diseases: Endocarditis Treatment: Vancomycin  S. saprophyticus Gram positive cocci Catalase positive, coagulase negative Normal flora: female genital tract Virulence factors: adhesins to attach Disease: Urinary Tract Infection in sexually active women, that can progress to “honeymoon cystitis” Treatment: Trimethoprim-sulfamethoxazole Streptococcus Forms cocci in straight chains rather than clusters. ALL are catalase negative, AEROBIC Classify types of Strep based on hemolytic qualities  Alpha  Beta (Group A & B)  Gamma Lancefield (1933) classification based on cell wall carbohydrates S. pneumoniae  S. viridans Gram positive Alpha hemolytic Normal flora of the throat Virulence: forms biofilms and attaches by using molecule known as dextran Disease: Dental caries, Endocarditis (affects damaged heart valve) Treatment: Penicillin  S. pyogenes  Gram positive cocci  Group A Strepococcal species, BETA HEMOLYTIC  Normal flora of throat and skin  Virulence factors:  M protein (inhibits phagocytosis, allows bacteria to attach to tissues, antigenic),  hyaluronidase, streptokinase, Dnase, erythrogenic toxin (rash)  streptolysin O & S (lyses RBC and neutrophils) : Antibodies form against antigen O, known as ASO give rise to Rheumatic fever. Streptococcus pyogenes Historically a common cause of serious infections Causes variety of infectious syndromes Based on M antigen- can be divided into multiple strains. The strains can be grouped into 2 main groups: Nephritogenic strains (cause skin infections- sequel can be Acute Glomerulonephritis AGN) Rheumatogenic strains (cause throat infections- sequel can be Acute rheumatic fever).  Diseases: Pyogenic: Pharyngitis (sore throat, fever, malaise, headache, abscess) Cellulitis, erysipelas Impetigo Toxigenic: Scarlet fever (sandpaper like rash sparing palms and soles, strawberry tongue) Toxic shock syndrome Immunogenic: - Rheumatic fever (occurs following pharyngitis) - Post-streptococcal glomerulonephritis (occurs after pharyngitis OR skin infection)  Labs Studies: rapid strep test (looks for antigen), ASO titers (Anti-streptolysin O antibodies), antiDNase (body produces antibodies against DNase made by bacteria). Treatment: Penicillins  S. agalactiae Gram positive cocci (group B strep) Normal flora of vagina and GI tract Virulence: polysaccharide capsule, lipotechoic acid of cell wall, hemolysin Diseases: Neonatal septicemia, neonatal meningitis and neonatal pneumonia Lab studies: CAMP test positive (enlarges the area of hemolysis formed by S. aureus) Treatment: Ampicillin  Enterococci faecalis Gram positive cocci, Group D, gamma hemolytic Normal flora of colon, urethra, female genital tract Virulence factors: hemolysin, adhesin Diseases: causes endocarditis to damaged heart valves, urinary tract infections, biliary tract infections Lab Studies: grows in bile and salt, PYR positive (pyrrolidonyl aminopeptidase) Treatment: Vancomycin Enterococcus faecium E. faecium – the bad one. Resistant to ampicillin More likely to be resistant to vancomycin than E. faecalis  Strep BOVIS +ve Gram _ Grows in the colon Associated with colon cancer  Branching Filaments Nocardia Actinomyces -Aerobic -Anaerobic -Found in Soil -Found in gingiva and vagina -Nocardiosis (pulmonary -Abscess of mouth due to infection) & cutaneous infection trauma, abscess in GI tract, with abscess in immuno- causes solitary brain abscess compromised host -Partially acid fast -Not acid fast - No sulphur granule In pus Presence of Sulphur granules in pus -Tx: TMP-SMX -Tx: Penicillin V Nocardia Actinomyces  Clostridium Spore forming Bacillus Rods/Bacilli Listeria Non-spore forming Corynebacterium  Clostridium C. tetani C. botulinum Anaerobic, spore-forming bacilli Anaerobic, spore-forming bacilli Transmitted when skin is penetrated by rusty Transmitted from food (honey, canned food) environment Spore germinates produce tetanospasmin: this Spore germinates  produces Botulism Toxin: blocks blocks release of GABA and Glycine from spinal cord release of acetylcholine (ACh) Tetanus: spastic paralysis, lockjaw Botulim: flaccid paralysis, respiratory distress Birbeck-granules (tennis-racket appearing) on stain Analysis for toxin in blood, vomit or stool. Treatment with immunoglobulin, Prevention with Treatment with antitoxin in adults Tetanus toxoid vaccine Used in BOTOX, why? Tetanus Botulism  C. perfringes:  found in soil, and colon Anaerobic Transmitted through trauma or foodborne (beef, poultry, gravies) Virulence: spore germinates in tissue to form alpha toxin (has lecithinase which disrupts membranes and causes hemolysis) Diseases: Gas gangrene/Myonecrosis, Food poisoning Lab Studies: Nagler reaction used to detect alpha toxin on egg yolk media Treatment: debridement, clindamycin  C. difficile: Found in colon Anaerobic, has flagella Due to overgrowth of C. difficile in the colon as a result of antibiotics killing normal flora. Virulence: Toxin A (enterotoxin damages intestinal mucosa) & Toxin B (cytotoxin that kills enterocytes) Diseases: Pseudomembranous Colitis – watery, mucus diarrhea, fever Lab Studies: toxin in stool Treatment: Metronidazole, Vancomycin  Bacillus Bacillus anthracis: Gram positive, spore forming, aerobic Virulence: polypeptide capsule (contains D- glutamate), anthrax toxin (increases cAMP which makes area edematous and necrotic) Disease: Anthrax (cutaneous  black eschar; pulmonary pulmonary hemorrhage) Lab Studies: Serpentine/ medusa-head appearance on microscopy Treatment: Ciprofloxacin, Doxycycline Bacillus cereus: G+, spore forming bacilli Virulence: toxin formed acts within 1-18 hours (reheated rice dishes) Treatment: self-limiting  Listeria Gram positive, non-spore forming, aerobic Grows on cheese, deli meats, coleslaw, hotdogs, unpasteurized milk, lettuce Virulence: Exotoxin, listeriolysin O (kills phagosome), facultative intracellular parasite (moves from cell to cell with actin filaments) Diseases: causes spontaneous abortion, neonatal meningitis, septicemia. May cause Listeriosis (gastroenteritis) in healthy adults, and meningitis. Lab Studies: tumbling motility, beta-hemolytic Treatment: Ampicillin  Corynebacterium diphtheriae  Gram positive, bacilli, aerobic  Normal Flora/Reservoir in throat, nasopharynx  Virulence: AB exotoxin (inhibits ribosome function and protein synthesis by stopping EF-2) – encoded by prophage  Disease: Diphtheria (pseudomembranous pharyngitis, lymphadenopathy), myocarditis  Lab Studies: grows on cystine-tellurite agar, forms granules, Elek test looks for toxin  Treatment: Penicillins to treat. Toxoid vaccine to prevent