Gram Positive And Gram Negative Cocci

Front 1

What are general characteristics of Gram Positive Cocci? Name the three important species for humans.

Back 1

- circular or spherical in shape
- purple in a gram stain
- (thick peptidoglycan layer)

Staphylococcus epidermidis - normal flora of the skin and muscosae
Staphylococcus aureus- pathogenic, often normal flora
Staphylococcus saprophyticus- in environment and on skin, can cause urinary infections

Front 2

Name the general characteristics of Staphylococcus aureus.

Back 2

- grows well on simple media (sugar, blood- agar)
- colonies 2-3 mm in 24 hrs.
- 37 degrees
- produce many toxins and enzymes
- only true staph pathogen

Front 3

What toxins does Staphylococcus aureus make? And their characteristics.

Back 3

1. Cytotoxins (alpha, beta, theta, gamma, P-V leukocidin): toxic to many cells- Leukocytes, erythrocytes, macrophages, platelets, fibroblasts. Spreads
2.Haemolysins: break down RBCs to get nutrient from blood, spread faster. lethal
3. Enterotoxin (A-E, G-I): superantigens, important cause of food poisoning (nausea, vomiting, cramps, pooping)
4. Exfoliative toxins (ETA, ATB): Scaled syndrome in infants
5. "Toxic shock syndrome Toxin 1": cause of toxic shock syndrome.

- the more toxins S. aureus can make the more pathogenic it is.

Front 4

What enzymes do Staphylococcus aureus make?

Back 4

1. Coagulase: coagulates fibrin (blood clots)
Coagulase test can be used for identification of S. aureus
-most pathogenic strains of S. aureus produce this. Blocks macrophages from getting rid of bacteria
2. Beta- Lactamase (penicillinase): destroys penicillin.
Others: hyaluronidase, staphylokinase.

Front 5

What are the clinical finding of S. aureus? ie. resistance, and symptoms

Back 5

- many of the strains in the normal population and 85- 90% of strains isolated in the hospital are penicillin resistant.
- 15% of healthy indiv. carry S. aureus. InL anterier nares, axilla, perineum, on hands.
- tends to produce localized purulent infections: pustules, boils, styes, conjunctivitis, otitis.
- Serious: pneumonia, osteomyelitis, septicaemia, endocarditis and others, particularly in compromised/ immunosuppressed hosts

ALSO: Food Poisoning. Toxic Shock Syndrome. Scaled Skin Syndrome.

- important cause of hospital acquired infections. (stitche abscesses. infected wounds,generalized infections
often resistant strains.

Front 6

What epidemiology does S. aureus present?

Back 6

- strains are lysed by a number of diff bacteria viruses.
-Cells originating from the same parental cells are lysed by the same bacteriophage.
- You can use "bacteriophage types" to track the source of infection

Front 7

What are preventative measures against S. aureus infections?

Back 7

1. Washing hands
2. Strict adherence to aseptic techniques. in post op.
3. Education of personal.

Front 8

Describe Staphylococcus epidermidis.

Back 8

- part of skin/ mucous membranes normal flora
- non- pathogenic.
- effects immunocompromised patients (opportunistic)
- post op. infections (brain, open heart)
-endocarditis (heart valve insertion)
-shunt infections
- in neonates can be cause of necrotising enterocolitis.

Front 9

Name the general characteristics of Streptococci bacteria. And how are they subdivided?

Back 9

- Gram positive
- pairs or forming chains
- fastidious in nutritional requirements (blood agar)
Subdivided by:

Haemolytic properties
-Alpha haemolysis: greenish brown zone of partial RBC destruction
-Beta haemolysis: clear zone of complete RBC destruction around colonies
* some strains are non- haemolytic

Carbohydrate C- Antigen
- extracted from the cell wall
- sub divides into groups A-T (lancefield classification)
- A is most common

M- Protein (type of pilliae)
- subdivides beta- haemolytic streptococci into over 70 serotypes
- virulence factor: antiphagocytic, degrades complement C3b

Front 10

How does Streptococcus pyogenes present itself?

Back 10

Acute tonsilitis: (strept infection)
- can lead to scarlet fever
- rheumatic heart disease

Skin infections
- cellulitis
- erysipelas
- wound, burn, infection

Fever:
- post partum
- post abortion

Septicemia

Complications (especially young patients:
- acute glomerulonephritis
- rheumatic fever (joints, heart valves)

Front 11

Name key characteristics of Streptococcus pyogenes.

Back 11

- Group A, beta- haemolytic
- common in environment and humans

Front 12

Which toxins does Streptococcus pyogenes produce?

Back 12

Streptolysins (O + S): beta- haemolytic and highly toxic for neutrophils and macrophages

Streptococcal pyrongenic exotoxins (Spes):
- super antigens Spe A- C
- causes the rash in scarlet fever

Front 13

What enzyme does S. pyogenes produce?

Back 13

Hyluronidase: splits hyaluronic acid in connective tissue, helps infection spread
"flesh eating disease"= necrotizing fasciitis
*not all strains can make this

Front 14

How many healthy individuals carry S. pyogenes? Is it penicillin resistant? How is it transmitted?
Prevention?

Back 14

- found 5-10%
- No, it is penicillin G sensitive
- direct contact, nasal carriers, contaminated food
- Education, strict asepsis in obstetric, early detection and treatment (because it is non transferable after 24 hrs.)

Front 15

Which bacteria (our example) is found in Streptococcus group B?

Back 15

Streptococcus agalactiae

Front 16

Describe Streptococcus agalactiae.

Back 16

- Opportunistic
- found in vagina of healthy women
- can cause neo natal infections

Front 17

Which neonatal infections does Streptococcus agalactiae cause?

Back 17

1. Early Septicaemia (SIRS= whole body inflammatory state): respiratory distress/ shock at birth or within 24 hrs. High fatality rate

2. Delayed Meningitic Form:
- 1-12 weeks later
- better prognosis
- can result in neurological damage

Front 18

Which bacteria (our example) is found in Streptococcus group D?

Back 18

Streptococcus faecalis

Front 19

Describe Streptococcus faecalis

Back 19

- Enterococcus: normal flora of the human GI tract.
BUT can cause infections when introduced into tissues (urinary, endocarditis, meningitis)
-often shows antibiotic resistance

Front 20

What are viridens Streptococci?

Back 20

- classification for the undecided types.
- found in oral cavity of healthy individuals.
- can cause problems in people with previously damaged heart valves
-this can happen through dental surgery, or other cuts.

Front 21

What are some major characteristics of Streptococcus pneumoniae? besides that it has stupid spelling

Back 21

- diplocci
- polysaccharide capsule has antiphagocytic properties
- 90 distinct serotypes
- found in naso-pharynx of healthy individuals

Front 22

What infections do Streptococcus pneumoniae cause?

Back 22

Lobar pneumonia: most often an auto infection
-can spread as carrier
-most frequent in the old, alcoholics, infancy
- can be an epidemic

Meningitis:
most often in infant and elderly.
- accompanied by bacteremia and septicemia

Front 23

Name two prevention methods for Streptococcus pneumoniae.

Back 23

1. Programs for the elderly and alcoholics.
2. vaccination for those at high risk: (above + crowed living quarters)

Front 24

What are the key characteristics of Gram negative cocci ?

Back 24

- pink stain
- thin peptidoglycan layer
- outer membrane
- round cells

Front 25

What are the general characteristics of Neisseria meningitidis?

Back 25

- gram negative
- diplococci: 2 round cells stuck together
-Lab isolation on chocolate agar (lysed blood) 5- 15% CO2 37 degrees
-use selective media to differentiate from naso- pharynx (thayer- martin)
- antiphagocytic polysaccharide capsules: 13 diff serogroups ABCXY W135 most common

Front 26

What are the infection specs. for N. meningitidis?

Back 26

Carriers occasionally develop infection. or pass it to non-immune people who get it.
- only affects humans
- affects young and crowed living quarters
- epidemics occur occasionally

Front 27

What infections does N. meningitidis present as?

Back 27

1. meningitis: purulent, high fatality rate if not treated fast
2. septicemia: high fever, rash, endotoxic shock.
3. If 1 and 2 together =complications = Water-fridrishesen syndrome:
- bilateral adrenal cortical haemorhage
- collaspe/ death in less than 24 hrs.

Front 28

What are preventions against N. meningitidis?

Back 28

Penicillin is primary.

Vaccination:
-conjugated vaccine for A, C, Y and W135
-infant for C

Front 29

Name two prevention methods for Streptococcus pneumoniae.

Back 29

1. Programs for the elderly and alcoholics.
2. vaccination for those at high risk: (above + crowed living quarters)

Front 30

what are the general characteristics of Neisseria gonorrhoeae

Back 30

- gram negative
- diplococci
- 0.6 - 1 micrometers
- lab: thayer- martin plates, damp CO2
- very sensitive to drying, temp changes

Front 31

What infections does N. gonorrhoeae cause? If untreated?

Back 31

Genital:
Men: acute infection of urethra
untreated- epididimitus, prostatitis
Women: 50% asymptomatic
cervicitis, urethra, rectum
Untreated- PID (pelvis inflammatory disease), sterility

Both Sexes: Rectal gonorrhea
pharyngeal infection
DGI: disseminated gonococcal infection- low grade fever, cutaneous infection, arthritis

Neonatal: rare

Front 32

What is the diagnosis of N. gonorrhaeae?

Back 32

Men: microscopy-
observe swabs of urethral discharge
Women: necessary from endocervical urethral, anal swab

Front 33

How do you treat N. gonorrhoeae

Back 33

Resistance has been seen from penicillin
- ceftriaxon, cefixime, ciprofloxin, azithromycin

- Simultaneous treatment of partners essential

- no vaccine available
- one protein can go through genetic replacement
- vaccine only against one strain. then changes