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The Main Genera of Gram Positive Cocci
- 1. Family Streptococcaceae
- 2. Family Micrococcaceae
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Family Streptococcaceae
- Family Streptococcaceae
- 1. genus Enterococcus
- 2. genus Streptococcus
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2. Family Micrococcaceae
- Family Micrococcaceae:
- 1. genus Staphylococcus
- 2. genus Micrococcus
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Catalase Test
differentiates between 1. Micrococcae and 2. Streptococcacea
- 1. Micrococcaceae= catalase (+)
- 2. Streptococcacea= catalase (-)
- Staphylococci contain the enzyme catalase which converts H2O2 (hydrogen peroxide) into water and oxygen.
- The test is performed by emulsifying a colony of staphylococcus in H2O2 and observing a bubbling reaction as O is liberated.
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Hemolysis types
- 1. Gamma (y) hemolysis- no hemolysis
- 2. Alpha hemolysis -zone of green - partial lysis of RBC's
- 3. Beta hemolyisis- clear zone of hemolysis - complete lysis of RBC's
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Staphylococcus General Characteristics
- mainly inhabitants of the skin, skin glands, and mucous membranes
- generally opportunistic pathogens that enter through skin ruptures
- 31-40 diff species
- 6-7 are clinically significant, the rest are found mainly in animals
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Staphylococcus (most commonly isolated species)
- 1. Staphylococcus aureus (most serious pathogen)
- The Coagulase (-)
- 2. Staphylococcus epidermidis
- 3. Staphylococcus capitis
- 4. Staphylococcus hominis
- 5. Staphylococcus saprophyticus
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Staphylococcus aureus
Growth and Physiological Characteristics
- Size: M-L
- Color: buttery white to creamy to golden
- w/some strains being B-hemolytic
- facultative anaerobes
- extremely resistant to adverse environmental conditions: pH, temp, drying, and many disinfectants
- Virulent Factors Enzymes and toxins:
- 1. Coagulases (triggers clotting of plasma)
- 2. Staphylokinase (fibrinolysin) - dissolves fibrin clots
- 3. Lipases
- 4. Hyaluronidases
- 5. Deoxyribonucleases
- Toxins:
- 1. Cytolytic toxins (1. Hemolysins 2. Leukocidins)
- 2. Enterotoxins -A, B, C, C2, D, E, and F
- 3. Exfoliative toxin (epidermolytic toxin) and Toxic Shock Syndrome toxin (TSST)
- Staphylococcus aureus is present in most environments, colonization of some infants begins hrs after birth
- carriage rate in normal healthy adults ranges from 20%-60% mostly in the anterior nares (will be present in the on the skin and mucous membranes)
- main predisposing factors include: tissue injury, preexisting primary infections, diabetes mellitus, poor hygiene
- Methicillin Resistant (MRSA)
- emerged in mid 80's as 1 of the so called "superbugs"
- multi-resistant organism that poses an epidemiological problem in the hospital setting (nosocomial infections)
- 10-15% of population are carries
- 95% of strains of S. aureus have acquired genes for penicillinase
- Strains of MRSA carry multiple resistance to antimicrobials including methicillin, gentamicacin, cephalosporins, tetracycline, erythromycin, and even quinolones
- few strains have acquired resistance to all major drug groups except Vancomyosins
- Scope of clinical Staphylococcal disease:
- 1. Localized cutaneous infections (superficial skin infections)
- a.Boils or furuncles
- b. Carbuncles
- 2. Post-operative wound infections
- 3. UTI's
- 4. Bacteremia, meningitis, osteomyelitis
- Staphylococcal infections
- inhabit nasopharynx, they can be aspirated into the lungs and cause a pneumonia involving multiple abcesses and symptoms of fever, pain, and bloody sputum
- circulating bacteria can be transported to the liver, kidney and spleen and form abscesses
- Toxigenic Staphylococcal disease
- 1. Food Poisoning- caused by strains that produce enterotoxins A, B, and D in improperly refrigerated food (mayonnaise. processed meats, sauces, ham, chicken)
- 2. Scalded Skin Syndrome (SSS) or Ritter's disease- caused by strains that produce the exofoliative or epidermolytic toxin
- 3. Toxic Shock Syndrome (TSS)
- associated w/high fever, rash, vomiting, and sometimes death
- caused by strains that producce the toxin TSST-1 also known as enterotoxin F
- originally associated w/tampon use
- (sunburn-like rash, fascitis necroticans- extreme infection of skin and deeper parts, influenza-like rash, signs of soft tissue infection, coma, multiogan failure,
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Osteomyelitis
- established in the metaphysis of a variety of bones (femur, tibia, ankle, wrist)
- abcess formation in the infected area result in a tender lump causing bone breakage
- symptoms: fever, pain, chills, and muscle spasms
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TSS Prevention
- read manufacture's instructions about the use of tampons
- compare absorbency from brand to brand
- be familiar with the terms "junior", "regular", "super", and "super plus"
- wear only during the day
- replace 4-6hrs
- wash hands before inserting
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Coagulase
- Coagulase is a plasma clotting enzyme secreted by Staphylococcus aureus- allows for clot formation
- 1. (+) Staphylococcus aureus
- 2. (-) Staphylococcus epidermis or S. saprophyticus
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Staphylococcus epidermidis
- generally part of the normal flora of the skin and mucous membranes
- mainly associated w/nosocomial infections such as catheter site infections, shunts, incision site infections, and nosocomial UTI"s
- associated w/ UTI's in elderly
- Characteristics of S. epidermidis:
- resembles S. aureus in microscopic and colonial morphology
- Coagulase (-)
- Novobiocin- sensitive
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Staphylococcus saprophyticus
- generally produces white to extremely white colonies
- microscopic morphology resembles S. aureus
- it is mainly part of the normal skin flora
- Clinical Significance:
- mainly associated w/UTI's that involve the bladder and (or) the kidneys in young sexually active women or in adolescent girls
- Coagulase (-)
- key biochem test is that it is resistant to Novobiocin disc
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Treatment of Staphylococcal infections
- penicillin susceptible strains (about 5%) are treated w/penicillin
- majority strain of S. aureus lactamase which allows them to breakdown penicillin
- susceptibility studies are recommended due to the variability in susceptibility patterns of penicillin resistant strains
- Drainage of abscesses should be performed for successful therapy
- 40% of nosocomial S. aureus infections are caused by MRSA
- new threat is an increasing number of Vancomycin resistant S. aureus
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Family Streptococcaceae
- 1. Streptococcus
- 2. Enterococcus
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Family Streptococcaceae
- 1. Streptococcus 2. Enterococcus
- gram (+)
- generally arranged in chains
- catalase (-)
- divided into categories based in the type of hemolysis they produce
- Classification and naming of Streptococci
streptococci are classified and named following two systems: - 1. Hemolytic pattern in conjunction with the Lancefield grouping
- 2. Scientific name from taxonomic organization
- Beta Hemolytic Streptococcus 1. Streptococcus pyogenes
- S. pyogenes is a strict parasite generally involved in upper respiratory tract infections
- Taxonomy-Beta Hemolytic
- these organisms can be further divided into a number of immunologic groups known as the Lancefield Groups (given alphabetic designations)
- Groups A, B, C, F, and G are commonly associated w/human infections
- Group A: Streptococci= S. pyogenes
- Group B Streptococci= S. agalactiae
- Virulence factors and toxins:
- 1. C carbohydrates- can also be teichoic acids found on surface of cell wall-protect from host cell's lysozyme defense
- 2. M-protein- resists phagocytosis and increases adherence
- 3. Capsule- chemically indistinguishable from HA capsules of host
- 4. Streptolysins- hemolysin that destroys that injures WBCS, liver, and heart tissue
- 5. Erythrogenic toxin- contributes to red rash and fever of scarlet fever
- 6. Streptokinase
- 7. Hyalyronidase
- Epidemiology and Pathogeneis:
- humans are the only significant reservoirs of S. pyogenes
- 5-15% of population are carriers
- outbreaks are seasonal, main pop. group affected is children 5-15yrs
- Main infections associated with S. pyogenes:
- skin infections: 1. Empetigo (associated w/poor hygiene, insect bites, and crowded living conditions)
- 2. Erysipelas
- 3. Cellulitis
- 4. Wound infections
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Strept Throat
- redness, edema, and swelling of pharyngeal membranes which results in difficulty in swallowing
- other fever, headache, nausea, and abdominal pain
- purulent discharge exudate may form over the tonsils and swollen lymph nodes
- tonsils may be white patch and contain white abscesses as well as pus
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Upper respiratory tract infections
- 1. Pharyngitis- tonsillitis (strep throat)- often diagnosed by symptoms and direct antigen testing
- 2. Scarlet fever- caused by a strain capable of producing the pyrogenic toxin
- similar symptoms as in pharyngitis w/ addition of a skin rash and yellow to white coloration of tongue
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Long term complications and conditions associated w/ S. pyogenes
- 1. Rheumatic fever (inflammatory condition of the joints, heart, and subcutaneous tissues)
- 2. Acute glomerulonephritis (AGN) (affects filtration of blood)
- 3. Streptococcal toxic shock syndrome
- 4. Streptococcal gangrene (necrotizing fascitis) also known as "flesh eating disease)
- note: necrotixing (dead) fascitis- connective tissue sheath around muscles and other organs
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Complications
- Rheumatic fever (begin between 6 weeks after a strep infection)
- return fever after strep infection has finished
- pain, swelling and redness in joints
- shortness of breath
- unusual skin rashes
- unusually fast heart beat or heart damage
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Glomerulonephritis
- develops between 3-6 weeks after the initial strep infection
- puffiness of face
- swelling of ankles
- headaches
- high blood pressure
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Necrotizing Fascitis
- streptococcus are introduced into small abrasions or cuts, where they grow rapidly
- their enzymes digest connective tissue in skin, while their toxins poison the epidermal and dermal tissue
- rare, but potential for harm is high
- most aggressive infections have come from the Rocky Mountains and East
- Epidemiologists believe that these new strains are probably mutants that have acquired toxin genes from infecting viruses
- high incidence in 80's
- note that even the most virilant strains are not antibiotic resistant
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Other infections include:
- 1. Ear infections
- 2. Bacteremia and septicemia
- 3. Endocarditis
- 4. Meningitis
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Identification of Streptococcus pyogenes
- size: Pinpoint-Small
- large zone of hemolysis
- key biochem reaction- sensitive (+) to bacitracin (A) disc
- Latex agglutination
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Antibiotic identification discs:
- 1."A" disc- Bacitracin disc
- 2."P" disc- Optochin disc
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1. "a" disc
- 1. Bacitracin discs ("A" disc)
- distinguishes Streptococcus pyogenes from Streptococcus agalactiae
- Streptococus agalactiae is resistant to it
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2. Streptococcus agalactiae
- B-hemolytic Streptococcus group B
- normal flora in: GI tract, vaginal canal
- size: Pinpoint-Small convex
- very small zone of hemolysis
- key biochem reaction- positive CAMP test
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Main infections associated w/ Streptococcus agalactiae
- In adults:
- UTI's, skin infections, bacteremia, endocarditis, osteomyelitis, post-partum infections (septicemia), urogenital (reproductive and urinary) infections in females
- In neonates:
- #1 agent implicated in pneumonia, bacteremia, meningitis
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3. B-helolytic Streptococcus groups C, F, and G (found in animals)
- may be involved in the same types of infections as groups A and B but with less frequency and generally in a milder form of the disease (NP infections, pneumonia, abscesses, meningitis)
- are not identified with one single biochemical test;
- identified by a Latex agglutination test
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Alpha hemolytic Streptococcus
- 1. Streptococcus viridans group
- 2. Streptococcus pneumoniae
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Other Viridans strains
- Streptococcus oralis
- Streptococcus mutans
- produce slime layers that are made of glucose polymers that adhere to tooth surfaces
- these sticky polysaccharides are the basis for plaque, the adhesive white material that comes from coinfected with other bacteria and fosters dental disease
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Streptococcus viridans group
- alpha hemolytic
- group of at least 5 species of gram(+) cocci that are Alpha-hemolytic resembling Streptococcus pneumoniae (Streptococcus mitans, S. mutans, S. Milleri, S. salivarius, S sanguis)
- part of normal flora of the oral cavity (gingiva, cheeks, tongue, saliva) as well as teh nasopharyx, genital tract, and skin
- occasionally involved in subacute endocarditis
- differential from Streptococcus pneumoniae by a negative (resistant) optochin "P" disc
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Endocarditis (Symptoms)
range from fever, heart murmur, emboli, weight loss, anemia
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1. Streptococcus pneumoniae
- Alpha-hemolysis
- gram (+)
- lancet shaped
- Pinpoint
- "checker" appearance
- "P" disc-Optochin
- Most common infections caused:
- 1. Lobar Pneumonia, mainly caused by the encapsulated strain
- 2. Nasopharyngeal infections
- 3. Eye and ear infections
- 4. Occasionally meningitis on newborns or infants
- Symptoms of Pneumonia:
- chills, shaking, rapid breathing, fever
- severe pain in the chest wall, cyanosis, a cough that produces rusty colored blood sputum
- In children, can spread to the meninges and cause meningitis
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2. "P" disc
- "P" disc- Optochin disc
- identifies Streptococcus pneumoniae as it is sensitive to it
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chart Streptococcus Species
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Genus Enterococcus
- Non-hemolytic
- gram (+)
- cocci
- catalase (-)
- part of normal flora of GI tract and skin
- Opportunistic pathogens- mainly involved in UTI's and superficial skin infections and surgical wound infections
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Main species in the genus Enterococcus:
- 1. Enterococcus faecalis
- (in elderly patients undergoin surgery and affect the urinary tract, endocardium, wounds, blood, appendix, and other intestinal structures)
- is isolated w/much more frequency
- "superbug" VRE
- 2. Enterococcus faecium
- (large intestine)
- 3. Enterococcus durans
- (large intestine)
- ALL species are involved in the same infections, but E. faecalis is isolated w/much more frequency
- identified to species level by automated methods (Vitek, Microscan)
- Key biochem test: PYR (+)
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Non-hemolytic (gamma)
Hemolytic Streptococcus
- generally part of normal flora of skin, mucous membranes, or oral cavity
- generally non-pathogenic
- need to be differentiated from Enterococcus by PYR test
- Ex: S. bovis, S. equinus, and others
- source-animals
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Gram (+) Antibiotic Resistance
- 5 most significant strains in nosocomial infections are:
- 1. Methicillin resistant Staphylococcus aureus (MRSA)
- 2. Vancomycin resistant enterococcus (VRE)
- 3. Multidrug resistant Streptococcus pneumonia (MDRSP)
- 4. Vancomycin resistant Staphylococcus aureus (VRSA)
- 5. Methicillin resistant Staphylococcus epidermsi (MRSE)
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Genus Neisseria
- General Characteristics:
- gram (-)
- diplococci
- adjacent side flattened (coffee or kidney bean shape)
- capnophilic- requiring a CO2 concentration between 3-10%
- fastidious
- cold labile
- oxidase (+)
- fimbriae
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Gonorrhea
- caused by Neisseria Gonorrhoeae
- symptoms:
- symptomatic, mild, severe
- appears: 2-5 days, moths, year
- Transmission: vaginal intercourse, anal intercourse, anal intercourse, oral sex, mother to child
- symptoms in men:
- prostatitis, periurethral abscesses, epididymitis, sterility
- Other complications: gonococcal conjunctivits, newborn and adylt: eye inflammation, discharge
- gonococcal pharyngitis, sore throat, fever, chills
- top 5 sexually transmitted diseases
- oropharyngeal and anorectal infections
- Specimen collection and processing:
- plated and incubated ASAP
- collected on MTM based media that provide CO2 environment such as JEMBEC plates
- Meningococcus found in nasopharynx of 3-15% asymptomatic individuals
- main strains associated with disease are: A, B, C, Y and W-135; with B being the most prevalent in the U.S.
- main virulent factors include the capsule, fimbriae and endotoxin production
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Meningitis
- inflammation of the meninges
- infections of the CSF
- infections and conditions associated w./Neisseria meningitis infects the mucous membranes of the nose and throat (nasopharyngeal), causing a sore throat
- Bacterial meningitis
caused by 1of3 types of bacteria - 1. Streptococcus pneumoniae (Pneumococcal)
- 2. Heaemophilus influenza (Hib meningitis)
- 3. Neisseria Meningitidis (Meningococcal)
- Neisseria Meningitidis come in 3 main or common strain called A, B, and C, and two rarer strains called Y and W-135
- each group can be recognized by molecules present in the capsule
- gram (-)
- diplococcus
- Infections and conditions associated w/ Neisseria meningitidis can cause meningitis can if the bacteria enters blood and cerebral spinal fluid where it can infect the protective covering (meninges) of the brain and spinal cord.
- Incubated: Chocolate Agar
- Marked by: fever, sore throat, headache, stiff neck, convulsions, and vomiting
- Symptoms:
- early symptoms are similar to flu
- In adults and children, the 1st are fever, vomiting, and drowsiness
- In infants:
- high-pitched moaning cry fever, perhaps cold hand and feet, difficult to wake up, dislike of being handled, vomiting, arching back
- Spread: sharing utensil, drinking containers, lipstick, cigarettes, kissing
- Aftereffects: balance problems, brain damage, deafness, epilepsy, recurring headaches, violent temper tantrums, amputations
- Prevention: vaccination, chemoprophilaxis, drinking containers, spoon, forks, knives, covering of mouth when sneezing or coughing, good hygiene
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4. Meningococcus and subcutaneous hemorrhages
when pathogen spreads endotoxin into the generalized circulation, which is a potent white blood cells. Damage to the blood vessels caused by cytokines leads to vascular collapse, hemorrhage, and crops of legions called pertechiae
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Meningococcemia
- 5. Meningoccemia can become a disease that has a sudden onset, marked by high fever, chills, delirium, and severe widespread ecchymoses
- 6. Generalized intravascular clotting, cardiac failure, damage to the adrenal glands, and death can occur within a few hours.
- Who is at risk?: newborns, children, young adults, elderly, AIDS patients, college students, and soldiers
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