Week 4

Question 1

List the genera that are considered pathogenic cocci.

Answer 1

-staphylococci G+ cocci, clusters, uniform
-Stereptococci, G+ cocci, chains, unifiorm
-Neisseria, G- diplococci hamburger buns, many sizes
-moraxella G- diplococci hamburger buns, many sizes flat adjacent sides

Question 2

Define the terms pyogenic, suppurative, and purulent exudate

Answer 2

puss

Question 3

What is the most frequently isolated GROUP of organisms in the clinical lab, part of normal flora and are opportunistic pathogens

Answer 3

Pathogenic cocci

Question 4

List the genera and species of the Family Micrococcaceae. 2 genus, 5 spp

Answer 4

Fam-micrococcaceae
Genus:
- staphlococcus
- Micrococcus
Species:
- S. aureus
-S. epidermidis
- S. saprophyticus
- S. haemolyticus
- S. luteus

Question 5

List the major characteristics of Micrococcaceae and explain the significance of each in the clinical lab. Staphylococcus Identification

Answer 5

-All G+ cocci that form clusters
-Med sized dome shaped colonies on SBA (smaller than G - rods) white colonies
-All are catalase positive (test differentiates staphs from streps)
-common normal flora (except in vagina and small intestines)

Question 6

Catalase test

Answer 6

3-5% H2O2 on slide, with loop 3-4 colonies, cat pos= rapid profuse bubbles
Wimpy bubbles= cat neg also RBC’s give fasle positive
Do not cool loop in agar, must have iso colonies

Question 7

What test is definitive for S. aureus (only produced by S. aureus)?

Answer 7

Coagulase

Question 8

Coagulase Test 4 methods

Answer 8

Rabbit plasma- fibrinogen= fibrin
Rapid slide- spot test, detects cell bound coagulase, some strains of S. aureus
Tube method- 4hr to O/N, detects free extracellular coagulase, must be done id rapid slide is neg, all strains
Rapid latex tests- spot text, staphyloslide- fibrinogen= fibrin and IgG= protein A

Question 9

S. aureus Colony morph, hemolysis, MSA, CNA, MAC, novo

Answer 9

-Colony morph SBA- med white to buttery color
-Hemolysis beta or gamma cannot use for ID
-MSA- man pos (48hrs)
-CNA- white growth
-MAC- NG
-Novobiocin- zone of inhibition or -susceptible S
- coag staph latex- pos

Question 10

S. epidermidis Colony morph, hemolysis, MSA, CNA, MAC, novo

Answer 10

-colony morph SBA- white dome shape
-hemolysis- almost always gamma or no hemolytic
-MSA- man neg both 24 and 48
-CNA- white growth
-MAC- NG
- novobiocin- susceptible
- coag staph latex-neg

Question 11

S. saprophyticus Colony morph, hemolysis, MSA, CNA, MAC, novo

Answer 11

-colony morph- white and yellow
-hemolysis- almost always gamma or non hemolytic
-MSA- man neg or weak man pos at 24 or 48hr
-CNA- white or yellow growth
-MAC- NG
- novobiocin- Resistant
-coag staph latex- neg

Question 12

Staphylococcus Flow Chart

Answer 12

look at flow chart

Question 13

List four major groups of infections/diseases caused by S. aureus. 4

Answer 13

skin infections
wounds
dissemination from local infections
toxin mediated diseases

Question 14

Skin infections causes by S. aureus

Answer 14

furuncles/ carbuncles
impetigo- bullous 80%

Question 15

Dissemination from local infection by S. aureus 6

Answer 15

Septicemia- infection in bloodstream with symptoms
Bacteremia- presence in bloodstream w/o symptoms
Osteomyelitis: inflammation on bone marrow
Pneumonia- infection in lungs
Endocarditis- drug users, heart infection
Meningitis- in meninges

Question 16

Toxin mediated diseases by S. aureus 3

Answer 16

-Toxic shock syndrome-traps S. aureus TSST-1
-Food poisoning- food left out, enterotoxins A & D= preformed toxins- 2-8hrs later
-Staphylococcal scalded skin syndrome
Ritters disease
Exfoliative toxin

Question 17

Invasive mechanisms by S. aureus 6

Answer 17

Coagulase- clumping factor
Hyaluronidase- hyaluronic acid breaks down tissue - spreading factor
Protein A- call wall protein unique to S. aureus- prevents phagocytosis 30% of protein A excreted by cell
Lipase- breaks down oils- all stap spp produce this
Staphylokinase- dissolves fibrin strands
Beta lactamase- breaks down penicillin, present in 90% of S. aureus strains

Question 18

Toxin production by S. aureus

Answer 18

Enterotoxins A-E: affects GI tract
Exfoliative toxin: epidermolytic toxin
Toxin 1: TSST-1

Question 19

Cytolytic toxins

Answer 19

alpha, beta, gamma. Toxin for many cells including leukocytes, macrophages, erythrocytes, platelets

Question 20

Coagulase Negative Staphylococcus (CoNS) 4

Answer 20

S. epidermitis
S. saporphytuc
S. haemolyticus
S. lugdunensis

Question 21

S. epidermidis

Answer 21

The most common aerobic bacteria on skin
Causes 70-80% CoNS infections
Low virulence-opportunistic pathogen
Causes nosocomial infections
Hospital inquiries infections
Plastic prosthetic devices- slime layer, adherence factor

Question 22

S. saprophyticus

Answer 22

UTI’s- adhere to epithelial cells lining urogenital tract
cystitis

Question 23

S. haemolyticus

Answer 23

NF occasionally seen in clinical samples

Question 24

S. lugdunesis

Answer 24

NF on skin, capable of causing osteomyelitis and septicemia, most known for causing aggressive endocarditis

Question 24

List the genera in the family Streptococcacae 2

Answer 24

-streptococcus -enterococcus

Question 25

List the species of the genus Streptococcus. 7

Answer 25

-S. pyogenes -S. agalactiae -S. pneumoniae -Viridans: S. mutans, S. sanguis, S. salivarius, S. mitis, S. milleri group -Enterococcus faecalis -E. Faecium -Group D streps

Question 26

List the laboratory characteristics of Streptococcus used to identify Streps.

Answer 26

Gram stain reaction: G pos cocci Cellular morphology: S. pyogenes: G pos cocci/ chains S. pneumoniae: G pos diplococci Colony morphology Nonpigmented Ground glass- translucent Hemolysis- beta, alpha gamma all used for ID Serological groupings- lancefield groups Normal flora- not found in outer ear

Question 27

Explain the Lancefield classification scheme and the basis of the three categories.

Answer 27

Based on components found in cell wall Caused diff serological reactions- 3 categories -C carbohydrates: 5 groups A,B,C,F,G -Lipoteichoic acid: group D: no C carbohydrate, look for LTA instead -Non-lancefield neither C carbo;s of LTA serotypes S. pneumoniae Viridans

Question 28

Which Strep spp are Beta hemolytic?

Answer 28

S. pyogenes (Group A) S. agalactiae (group B)

Question 29

Which Strep spp are alpha hemolytic?

Answer 29

S. pneumoniae Viridans Group D Streps: S. bovin, S. equinus, E. Faecalis, E. faecium

Question 30

Strep Pyogenes or Group A tests and results: hemolysis, bacitracin, pry, rapid Gr A strep kit, latex agglutination kit

Answer 30

Hemolysis- beta, due to streptolysin S and O (S=oxygen stable, O= oxygen labile) Bacitracin- A disk- bas S or susc PYR- pos Rapid Gr A strep test- pos Latex agglutination kits- pos

Question 31

Explain how to test for streptolysin O, when to use it, and how to interpret it.

Answer 31

Stab agar with organism, beta hemolysis= pos

Question 32

Positive for group A strep requires what 3 pos tests?

Answer 32

Good strong beta hemolysis Stab O pos Bacitracin sus (no growth )

Question 33

Define SXT and when it is used.

Answer 33

Inhibits NF sulfamethaxazole and trimethroprim

Question 34

Explain in detail how an ELISA Rapid Strep Test Kit functions.

Answer 34

Sample with C carbo added- antibody and enzyme conjunction added- add substrate = reaction of color is pos on T line

Question 35

List and describe the 6 pathogenic factors of Gp. A Strep. Streptococcus 6

Answer 35

-M protein: resists phagocytosis and adhere to mucosal cells -Dnase: break down DNA to give more room -Hyaluronidase: breaks down connective tissue- spreading factor -Streptokinase: breaks up clots -Streptolysin O and S: breaks down RBC’s -Pyrogenic exotoxins

Question 36

List and describe the clinical diseases each of the major Streptococcus species and Enterococcus. List the antimicrobial therapy or vaccines (if available) used to treat each species.

Answer 36

1. Localized infections: -pharyngitis- 90% Gp A strep ages 5-15 -impetigo- pustule -erysipelas- clear demarcations -cellulitis deeper invasion 2. Sequelae: -Scarlet fever-rash -Rheumatic fever- inflammation of heart -Acute glomerulonephritis- hypertension and low urine output -Invasive Group A strep- necrotizing fasciitis -Toxin shock syndrome- spread to blood