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107 Cards in this Set
- Front
- Back
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List the genera that are considered pathogenic cocci.
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1. Staphylococci
2. Streptococci 3. Neisseria and moraxella |
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Define pyogenic and suppurative
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Pus producing
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Define purulent exudate
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Fluid containing pus
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List the genera and species of Micrococcaceae
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Genus: Staphylococcus, Micrococcus
Species: S. aureus, S. epidermis, S. saprophyticus, S. haemolyticus, M. luteus |
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Common characteristics to all staphs
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1- all are G pos coccci that generally like to cluster
2- medium size dome shaped colonies on SBA, white to light gold color, colonies are smaller then enteric GNR 3- all are catalase positive 4- commonly found a s normal flora except in sm intestine or vagina |
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Examples of skin infections caused by S. aureus
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-Furuncles
- Carbuncles - Impetigo |
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What is a furuncle?
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-Furuncles- pus filled lesion that begins as folliculitis
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What is a carbuncle?
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Carbuncles- several furuncle coalesce and extend deeper into the tissued
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What is impetigo and it's two general types?
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-Small, flattened, red patches on the face and limbs usually of children
Two Types 1- Bollous- like a sunburn blister. The organism is in the fluid of the blister. Causes are 80% S. aureus and 20% S. pyogenes 2- Pustule- always caused by S. pyogenes |
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Examples of disease caused by dissemination of S. aureus.
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-Septicemia
- Osteomyelitis -Pneumonia -Endocarditis (drug users) -meningitis |
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Examples of toxin mediated S. aureus diseases
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Toxic shock syndrome
Food poisoning Staphylococcal Scalded Skin Syndrome |
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Toxic Shock Syndrome
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-Linked to super absorbant tampons in the 80's
-S aureus produces the toxin TSST-1 which is absorbed into the blood and can cause fever, hypotension, shock, and death |
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S. aureus Food poisoning
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-S. aureus arises in food left our at room temp for 2 hours or longer
-Begins to produce enterotoxins A and D -Symptoms start in 2-8 hours, nausea, vomiting, severe cramps, diarrhea -Source is usually the preparer |
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Scaled Skin Syndrome
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-Skin sloughs off
- AKA Ritter's disease -produced by an exfoliative toxin -Symptoms are self limiting -usually associated with children |
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Invasive mechanisms of S. aureus
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-coagulase-(Clumping factor)
- Hyaluronidase-(spreading factor) -Protein A -Lipase -Staphylokinase -Beta lactamase |
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Coagulase
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coagulase-(Clumping factor) converts fibrinogen into fibrin causing a clot
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Hyaluronidase
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Hyaluronidase-(spreading factor)- breaks down hyaluronic acid in the matrix between cells
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Protein A
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Protein A- prevents antibody mediated phagocytosis by binding to Fc portion of antibody
-30% is free floating that is excreted to bind up IgG -Unique to S. aureus -can bind to FAB and Fc portion of antibody |
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Lipase
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breaks down oils produced by sebaceous glands
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Staphylokinase
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Dissolves fibrin threads in blood clots allowing S. aureus to free itself from clots.
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Beta Lactamase
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aka Penicillinase
- now present in over 90% of S. aureus strains -Doesn't play a role in inhibiting the body's natural defenses -allows bacteria to survive treatment with beta-lactamase antimicrobial drugs such as penicilln and cephalosporin |
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Toxins produces by S. aureus
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-Enterotoxin A-E- affect the lining of the GI tract
-Exfoliative toxin- epidermolytic toxin - Toxin 1- TSST-1 |
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S. aureus Cytolytic toxins
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-alpha, beta, delta, gamma
-these toxins break down leukocytes, erythrocytes, platelets, and macrophages. - when these toxins destroy phagocytes, lysosomes are released and they damage the nearby tissue |
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CNS species
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Coagulase negative staphylococcus
- S. Epidermidis - S. Saprophyticus - S. Haemolyticus -- all three can be reported out as CNS unless it's in a urine culture or it's in a sterile body site |
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Characteristics of S. Epidermidis
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- most common aerobic bacteria on skin
- causes 70-80% of CNS infections - low virulence, opportunistic Pathogen - causes nosocomial infections |
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Characteristics of S. Saprophyticus
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Appear in uti's in sexually active women and older men
- adhere to epithelial cell lining of urogenital tract - causes cystitis |
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S. haemolyticus characteristics
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NF occasionally seen in clinical samples
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Gram stain contol species
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Escheichia coli- gram neg rods
Enterococcus faecalis- gram pos cocci |
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Describe catalase test, purpose materials, controls
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- Used to differentiate colonies of staph from strep
- uses hydrogen peroxide, glass slide, and inoculating loop - positive Staph aureus - negative Strep pyogenes |
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Describe coagulase test, purpose, materials, and controls
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- Used to differentiate staph aureus from others staphs
- uses rabbit plasma - place 2-3 drops of plasma on slide, transfer 2-3 colonies onto plasma, and mix well for 30 sec. - pos is Staph aureus - neg is Staph epidermidis |
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Describe novobiocin test, purpose, materials, controls
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- used to differentiate Staph saprophyticus from Staph epidermidis
- use an sba plate with novo disk - susceptible is Staph epi - resistant is staph sapro |
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MRSA
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Methicilin resistant staph aueus
- methicilin binds to transpeptidases and inhibits peptidoglycan synthesis - mrsa strains have modified their transpeptidases so that the drug cannot recognize the enzyme and connot be affected |
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What is a PBP?
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- penicillin binding protein
- it's a transpeptidase enyme that if bound to by penicillin will prevent the cross bridge from binding to the NAM |
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Beta lactamase
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An enzyme produced by 95% of S aureus strains that is able to inactivate penicillin.
- acts by breaking apart the beta lactamase ring of penicillin producing an inactive form of the drug called penicilloic acid |
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Tanspeptidases
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Eyeing the synthesis of the peptidoglycan there are enzymes that bind the tetrapeptice cross bridge to the NAM molecules
- also called penicillin binding proteins |
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Why is oxicillin resistant S aureus a more appropriate name than MRSA?
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- the drug methicillin is no longer used ih th u.s. Instead a drug called oxacillin is used.
- oxacillin is morer stable and has a longer shelf life than methicillin |
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MRSE and VRSE
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Methicillin resistant S. Epidermidis
- vancomycin resistant S. Epidermidis |
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What are two problems associated with vancomycin
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- it has some serious side affects
- it task much longer ot kill the Bactria than than oxacillin adding significantly to the length of time an individual is required to be hospitalized |
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Genera and species of streptococci
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Genus- Streptococcus and Enterococcus
Species- - S progenies - S. Agalactiae - S. Pneumoniae - viridans - Enterococcus faecalis - E. Faecium - gp. D streps |
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Clinical characteristics of streptococcus
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- G pos cocci
- progenies likes to form chains especially is broths - on SBA it's non pigmented (translucent) - progenies is beta hemolytic - pneumoniae is alpha hemolytic - found anywhere in the body where there is normal flora |
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Explain PYR test
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A PYR disc is placed on the slide and moistened with saline
- 3-4 large or 5-6 small colonies are placed on disc - add ine drop of cinnamaldehyde reagent - allow 2 minutes for color to develop |
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Explain bacitracin test
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- inoculate SBA pie plate with an isolated colony of beta hemolytic strep
- aseptically place a bacitracin disk in the center of the pie wedge - incubate in co2 for 18-24 hrs - susceptible control is S. pyogenes - resistant control is S. agalactiae |
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Explain optochin test
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- inoculate SBA pie plate with alpha hemolytic strep
- aseptically place optochin disk in center of pie wedge - incubate in co2 for 18-24 hrs - susceptible control is S. pneumoniae - resistant strain is S. progenies or S. agalactiae |
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Explain hippurate test
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- inoculate sodium hippurate reagent with 3-4 colonies
- parafilm and incubate test tube O/N at 37c - after incubation add 6-10 drops of ninhydrin reagent to the tube DO NOT SHAKE - read after 10 minutes - test should be used conjunction with camp test - positive control is Gp. B strep - negative control is E faecalis |
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Explain camp test
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- take a vet hemolytic S. Aureus and steak a straight line down an SBA
- streak the test organism in a straight line perpendicular to the s aureus line. - lines should be 2 mm apart - inoculate plate in co2 at 37c O/N - positive control is S. agalactiae - negative control is S. pyogenes |
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Explain bile esculin hydrolysis test
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- innoculate the agar plate, slant or broth with an isolated colony
- incubate for 18-24 hrs in air - observe media for color change - positive control is Gp. D strep or enterococcus sp. - negative control is an non Gp. D strep |
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Explain lance field classification scheme
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- based on layer of CHO found in Cell wall which determine serological rxns
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Name the three division categories for lancefield
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- C CHO
- lipoteichoic acid - non-lancefield |
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C CHO category
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5 groups A, B, C, F, G
- each cause different sereological rxn's - group A is S. progenies - group B is S. agalactiae |
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Lipoteichoic acid category
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- this group does not have C CHO in the cell wall
- the llipoteichoic acids are different than they are in Gp. A and Gp. B - the unique type is Gp. D which includes S bovis, S equinus, E faecalis, E faecium. - if it's not enterococcus we sign it out as Gp. D strep |
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Non-lancefield grouping
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Has neither C CHO or lipoteichoic acid
- includes S pneumoniae and viridans |
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What are the six pathogenicity factors of Gp. A strep
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- M protein
- DNase -hyaluronidase - streptokinase - streptolysin O and S - pyrogenic exotoxins |
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Explain M protein
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Unique to S progenies
- attached to peptidoglycan - 80 different strain dependent serological groups - assists organism by resisting phagocytosis and helps to adhere to mucosal cells |
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Explain DNase
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- allows organism to break up DNA that is expelled from lysed cells
- DNase breaks the DNA up and helps to make the humor it's in less viscous |
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When and how to test for streptolysin O
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Use in Gp. A strep screen only
- streak out plate with organism and then stab agar between Q1 and Q4 not letting stabs touch either - place bacitracin disk in Q1 close to Q2 - to sign out Gp. A you must have strong beta hemolysis, Streptolysin O pos, and bacitracin susceptible - Must meet all three criteria |
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Explain the Rapid Gp A strep tests
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- A double swab is used to collect the sample, one swab is used for the rapid strep kit, and the second kit is reserved so if the test is negative we MUST do and SBA with BAC and Stab-O
- 10% of kits give false negatives - we report out as Gp. A Strep POS or NEG - We CANNOT report out as NF |
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What are the pathogenic characteristics of strep
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- Streptolysin O and S
- Hyaluronidase - M protein - Streptokinase - Pyrogenic exotoins - DNase |
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Explain role of Streptolysin O and S
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O is labile
S is stable - Lyse rbc's, wbc's, and platelets and interfere with oxygen carrying capacity - when phagocytized they cause the phagocyte lysosomes to release their content which lyses the cell and releases the bacteria |
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Explain the role of M protein
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- unique to S. pyogenes
- 80 different strains - helps resist phagocytosis, and helps with adherence to mucosal cells |
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Explain the role of streptokinase
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Breaks down fibrin, spreading factor
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Explain the role of pyrogenic toxins
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- stimulate helper T lymphocytes and macrophages to release cytokines that in turn stimulate fever, widespread rash, and shock.
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Explain the role of DNase
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- Allows organism to break up DNA that is expelled from lysed cells reducing the firmness of the surrounding pus
- Facilitates bacterial spread |
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Define Beta lactam ring
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- Functional portion of penicillin which is broken down by Beta-lactamase from S. aureus
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Explain Strep pharyngits
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- Localized infection that is suppurative, purulent
- Causes sore throat, malaise, fever, headache - most prevalent in ages 5-15, 90% have bacterial (90% of these are Gp. A), and 10% are Viral - In adults the cause is 10% bacterial and 90% viral - Overall only 50% of patients diagnosed actually have strep throat |
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Strep impetigo
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-Strep pyogenes produces all pustule impetigo
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Pyoderma
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- Gp. A strep disease
-A confined pus producing lesion that usually occurs on the exposed skin of the face, arms, or legs |
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Erysipelas
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- Gp. A strep disease
- Infection that involves surrounding lymph nodes and triggers pain and inflammation - most commonly seen on childrens faces |
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Cellulitis
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-Gp. A strep disease
- May develop following deeper invasion of Gp. A Strep following erysipelas. - May be serious, and even life threatening especially in cases where the bacteria becomes septicemic |
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Scarlett fever
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-Gp. A strep sequela disease
- Often accompanies Strep throat when the infection involves a lysogenized strain of S. pyogenes - Pyrogenc toxins are released and trigger a diffuse rash, and causes tongue to be strawberry red |
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Rheumatic fever
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Gp. A strep sequela disease
- Complication of untreated Gp. A Strep pharyngitis. - inflammation leads to damage of heart valves and muscle |
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Acute glomerulonephritis
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Gp. A strep disease
- antibodies bound to the antigens of some strains of Gp. A accumulate in the glomeruli resulting in inflammation of the glomeruli and nephron which obstructs blood flow. |
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Necrotizing fascitis
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Invasive Gp. A Streptococcal disease
- Secretes enzymes that destroy fascia - moves through tissue at a rate of one inch per hour - infected areas must be removed |
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Toxic shock syndrome
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Gp. A Streptococcal disease
- PYOGENIC EXOTOXINS - Spread of the organism in immunocompromised patients which leads to bacteremia |
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Antimicrobial therapy for Gp. A strep
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Penicillin
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Diseases caused by Enterococcus and drug of choice for treatment
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- E. faecalis, and E. faecium are the pathogenic species
- Common cause of nosocomial infections and UTI - Drug of choice is Vancomycin |
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Define SXT and when it is used
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- SBA plate with sulfamethoxazole and trimethroprim
- used in Gp. A strep culture - inhibits most NF and is used in the isolation of Gp. A and Gp. B strep |
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Explain ELISA
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- Sera being tested is added to a well
- anti-group A antibody is added - Enzyme labeled anti-antibodies are added to the well and bind to any bound antibody - enzymes substrate is added and the enzyme converts the substrate into a colored product |
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Explain the Quelling reaction
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Reaction in S. pneumoniae where a type specific capsular antigen added to the cells cause the cells to swell
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Explain the Bile solubility test
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Used to distinguish pneumo colonies from other alpha hemolytic strains.
- Add a drop of bile to the colony, and chemicals present in pneumo are triggered to lyse the cells causing the colony to dissolve in a few minutes |
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Name an alternative technique to a sputum sample for collecting a lung aspirate
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Bronchial wash.
- allows you to retrieve a sample without contaminating it |
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List disease caused by S. pneumoniae in order of occurance
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1- pneumonia- pneumo constitutes 85% of of pneumonia in adults especially if older than 65
2- Eye and ear infections- known as otitis media. pneumo and Haemophilus influenza cause 50% of all cases 3- Meningitis- pneumo can spread to meninges via bacteremia during sinusitis or otitis media. mortality rate is 20x that of other meningitis causing organisms |
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List virulence factors of S. pneumoniae
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1- Pneumolysin enzyme- allows bacteria to cross pass ciliated cells
2- Secretory IgA proteases- destroy IgA 3- Phosphorycholine- chemical that stimulates the lung, meninge, an blood vessel wall cells to engulf the bacteria |
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Antimicrobial for S. pneumoniae
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Penicillin, erythromycin and others,
- 33% of S. pneumoniae is penicillin resistant |
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Explain the S. pneumoniae vaccine composition and when it is needed
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- Consists of purified capsular material from 23 different strains which covers about 94% of clinical isolates and is given in a single dose
- recommended for individuals over 65 |
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Which tests differentiate Enterococcus form Gp. D streps
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Enterococcus is NaCl POS, and PYR pos, whereas Gp. D is negative for both
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Why is it important to differentiate between Gp. D and Enterococcus
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- Gp. D is susceptible to penicilln whereas Enterococcus is resistant. The drug of choice for Enterococcus is Vancomycin however resistant strains are becoming common
- Require 2 confirmatory test for enterococcus or Gp. D strep like NaCl which should NEVER BE TESTED OFF OF AN SBA |
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Clinical importance of Gp. D and Enterococcus
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Both are NF in the intestinal tract and upper respiratory tract
- Are a common cause of nosocomial infections and UTI's |
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Alternative media for resistant Enterococcus
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- Enterococcosel plate with Vancomycin
- Growth on this plate would indicate resistant strains, and is sometimes used as a primary plating media in urine cultures |
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Strep Viridans species and importance
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milleri group, sanguis, mutans, mitis, salivarius
- All are opportunistic pathogens - Mutans is a causative agent of tooth decay. It forms dextran from glucose, and when large quantities of dextran is present it allows viridans and other microorganisms to colonize and from plaque. - Major disease caused by viridans is bacterial endocarditis which commonly precedes dental extraction, oral surgery, and occasionally routine teeth cleaning. Can lead to heart failure |
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Genus and species of Neisseriaceae
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Genus- Neisseria and Moraxella
Spp- N. gonorrhoeae, meningitidis, cinerea, sicca, mucosa, flavescens, subflava, and Morexella catarrhalis |
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Diseases caused by N. gonorrhoeae
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- Gonorrhea- 3-5% of males are asymptomatic, the rest have acute urethritis, purulent discharge, and dysuria. Females have dysuria, lower abdominal pain, and vaginal bleeding. Symptoms occur 2-5 days after infection
- PID: infection of uterus, fallopian tubes, and adjacent pelvic structures. 25% of women with gonorrhea come down with PID which can lead to infertility or ectopic pregnancy, and can cause Gonococcal ophthalmia which is an eye infection in newborns and may cause blindness if not treated with silver nitrate, tetracyclin, or erythromycin |
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Diseases caused by N. meningitidis
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- Normal flora in 40% of population
- opportunistic pathogen - #1 cause of meningitis, called meningococcal meningitis |
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Meningococcal meningitis symptoms, epidemiology, and diagnosis
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Symptoms: abrupt frontal headache, stiff neck, nausea, vomiting, confusion, petechiae. If encephalitis occurs deafness, blindness, coma, or death may result
Epidemiology: Spread through respiratory droplets in close populations such as in dorms and prisons and barracks. Mortality rate is 100% if not detected and treated early, 10% if treated early. Death may occur 6-12hrs after initial symptoms. Lab Diagnosis: spinal tap, direct G.S., milky due to bacteria and WBC's. Will grow on CHOC as a Gray mucoid colony |
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Viral menigitis
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Usually milder than bacterial, same symptoms but death is rare.
-90% of cases are from the genus Enterovirus. - Patients recover completely without treatment after 7-10 days |
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Explain how N. gonorrhoeae has become penicillin resistant
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- 15-20% of strains are plasmid-mediated penicillinase-producing PMPP.
- They produce an R factor which is a gene for Beta lactamase - There is no vaccine because the surface antigens are highly variable which is why promiscuous people can get infected more than once. |
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Virulence factors for Neisseria
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1-Capsule- protects against phagocytosis, helps adhere, and prevents dessication
2- Cell wall proteins- I, II, and III. Consistently found in all strains, basis of ELISA tests 3- Pili- strains T1 and T2 have pili which make them virulent. Conjugation pili are used for transferring genetic information. Pili are also inhibit phagocytosis, and stick like velcro to tissue 4- Endotoxin- lipooligosaccharide, inhibits phagocytosis and causes damage to host cells and tissue, and helps with adherence 5- IgA protease: breaks down IgA which is found in the URT, GI, urogenital tract, saliva, tears, and breastmilk |
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List the special requirements for collection, incubation, and transport of Neisseria gonorrhoeae
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- Must use Dacron or Rayon swabs which don't have fatty acid contaminants
- Sensitive to drying out during transport so much be plated within 6 hrs, and must use specialized Jembec GC transport media - Must be kept at room temp or above, easily killed in fridge temps of 4 degrees C - Organism is fastidious so it requires hemin. Will not grow on SBA, unlike N. meningitidis which will - Capnophile, preferes 3-5% CO2, our incubator is 7% and the incubator grows just fine |
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Thayer-Martin antibiotics
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- CHOC plate
Vancomycin- inhibits G pos cocci Colistin- inhibits GNR Nystatin- inhibits yeasts |
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Modified Thayer-Martin antibiotics
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-CHOC plate
Vancomycin- inhibits G pos cocci Colistin- inhibits GNR Nystatin- inhibits yeasts Trimethroprim lactate- inhibits proteus spp. |
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New York City
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Vancomycin- inhibits G pos cocci
-Transparent media Colistin- inhibits GNR Amphotericin B- inhibits yeasts Trimethroprim lactate- inhibits proteus spp. |
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Possible specimen sources for N. gonorrhoeae
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- Urethra
- Surgical tissue from PID patients - Throat swab - Joint fluids - called a GC (gonococcal) screen: if other flora are present, only work up diplococci |
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Key lab reactions for Neisseria
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1- Gram stain: tiny diplococci that are pleiomorphic
2- Colony morphology: small gray translucent, N. gonorrhoeae will not grow on SBA 3- Capnophile 4- Cat POS 5- Oxidase POS 6- CHO utilization using CTA (cystine tripticase Agar), pathogenic strains are unable to ferment maltose, sucrose, or lactose |
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Non-pathogenic Neisseria and characteristics
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- cinerea, sicca, mucosa, flavescins, subflava
- NF in URT - rarely involved in human infections - Non-fastidious - G neg diplococcus - CAT POS - Oxidase POS - Colonies are dry with white, tan or light yellow color |
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Define saprophytic
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- feeding on dead or decaying organic matter, obtaining food osmotically from dissolved organic material
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Previous names for Moraxella catarrhalis
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- Neisseria catarrhalis
- Branhamella catarrhalis |
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Infections caused by M. catarrhalis
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NF in the URT and is involved in respiratory tract infections.
- Considered a rare opportunistic pathogen and rarely causes diseases in humans - if it does cause disease it's involved in Bronchitis, otitis media, sinusitis, and pnuemonia |
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Lab identification characteristics of M. catarrhalis
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- Oxidase pos
- Cat POS - G neg diplococcus - NOT fastidious - Colony morphology is like a hockey puck consistency. It will slide across the plate as a whole intact colony when you try to move it - Beta lactamase pos - DNase POS |
