LABORATORY DIAGNOSIS: Staphylococcus aureus

Question 1

beta – hemolytic pattern
golden yellow

Answer 1

BLOOD AGAR

Question 2

contains 7.5% to 10% sodium chloride

Answer 2

MANNITOL SALT AGAR

Question 3

inhibits gram – negative organism

Answer 3

PHENYL ETHYL ALCOHOL (PEA)
COLISTIN NALIDIX ACID AGAR (CNA)

Question 4

Selective and differential for
isolation of MRSA (+) mauve/pink
colored colonies

Answer 4

CHROM agar

Question 5

Coagulase is an enzyme that converts soluble fibrinogen into soluble fibrin

Answer 5

Coagulase Tests

Question 6

is the only significant human pathogen that possessess the coagulase enzyme

Answer 6

Staphylococcus aureus

Question 7

Principle:
Fibrinogen _______________Fibrin
(+) white fibrin clots
(-) Smooth suspension

Answer 7

Coagulase test

Question 8

Cell bound coagualse

Answer 8

Slide

Question 9

Free coagulase

Answer 9

Tube –

Question 10

Uses ___ (anticoagulated with EDTA) for coagulase test

Answer 10

Rabbit plasma

Question 11

Purpose:
Staphylococcus aureus contains a heat-stable thermonuclease and coagulase negative staphylococcus does not.

Answer 11

THERMONUCLEASE TEST

Question 12

A rapid test to differentiate between the two organisms. : heat-stable thermonuclease and coagulase negative

Answer 12

THERMONUCLEASE TEST

Question 13

THERMONUCLEASE TEST: Positive:

Answer 13

Pink zone of clearing at the edge of the well with a darker blue ring at the outer periphery of the zone;

Question 14

use MSA plate; (+) = yellow colored S.
aureus colonies (w/ yellow halo)

Answer 14

Mannitol Fermentation test

Question 15

(+) = jet black colonies

Answer 15

Tellurite glycine agar

Question 16

(+) = pink color acetoin (acetylmethyl carbinol)

Answer 16

Voges-Proskauer test

Question 17

(+) = clear/colorless zone around the test
organism

Answer 17

DNase test (DNA-Methyl green agar)

Question 18

used in detecting both clumping factor and Protein A

Answer 18

Latex agglutination test

Question 19

useful in detecting altered PBP and oxacillin resistant strains

Answer 19

Latex agglutination test

Question 20

used for identification of mecA gene

Answer 20

Molecular test (Nucleic acid probes or PCR
amplification)

Question 21

gold standard for MRSA detection

Answer 21

Molecular test (Nucleic acid probes or PCR
amplification)

Question 22

Drug of Choice for Staphylococcus aureus

Answer 22

Penicillin (Drug of Choice)

Question 23

resistant penicillin (Nafcillin, oxacillin,
methicillin)

Answer 23

Penicillinase

Question 24

used when isolates are resistant to
the penicillin derivatives

Answer 24

Vancomycin

Question 25

- screened using 6ug/ml VA that is incorporated to BHI agar, (+) = any growth of the medium

Answer 25

Vancomycin agar screen plate

Question 26

used to screen MRSA clinical sample - (+) growth of more than 1 colony - (-) absence of growth on the agar plate * resistant to oxacillin → Beta-lactam drugs report as resistant

Answer 26

Oxacillin screen plate (MHA w/ 4%NaCl and 6ug/ml oxacillin)

Question 27

- preferred method for detecting resistance in both S. aureus and S. lugdunensis.

Answer 27

Cefoxitin disc diffusion (30ug)

Question 28

- detect inducible clindamycin resistance in staphylococci - 15ug E and 2ug Cd (15-26 mm apart on MHA or BAP) - (+) = flattening on one side (near erythromycin disc) of the clindamycin ZOI, which gives appearance of a “D-zone” - (-) absence of blunting indicates E resistance

Answer 28

Double-disc diffusion test (D –test)

Question 29

represents 50% - 80% of all coagulase – negative staphylococci

Answer 29

Staphylococcus epidermidis

Question 30

organisms that have traditionally been considered skin contaminants, and their recovery from cultures doesn't always indicate presence of disease.

Answer 30

Staphylococcus epidermidis

Question 31

account for a large number of nosocomial and opportunistic pathogen in immunocompromised patient

Answer 31

Staphylococcus epidermidis

Question 32

Habitat: Skin & Mucus membrane

Answer 32

Staphylococcus epidermidis

Question 33

Mode of Transmission: sterile site by implantation of medical devices e.g. shunts, prosthethic devices; human serves as exogenous or endogenous source of infection

Answer 33

Staphylococcus epidermidis

Question 34

Bacteremia associated with the use of catheter, orthopedic/prosthetic implants, CNS shunt, pacemaker

Answer 34

Staphylococcus epidermidis

Question 35

Stitch abscess, endocarditis, UTIs,

Answer 35

Staphylococcus epidermidis

Question 36

Habitat: human skin, peri – urethral and urethral area

Answer 36

Staphylococcus saprophyticus

Question 37

second most common pathogen associated with UTIs causing 10-20% of all UTIs in sexually active young women

Answer 37

Staphylococcus saprophyticus

Question 38

The virulence factors of S. saprophyticus include

Answer 38

adherence to urothelial cells by means of a surface- associated protein, lipoteichoic acid; a hemagglutinin that binds to fibronectin, a hemolysin; and production of extracellular slime.

Question 39

It infects humans through sexual intercourse or through contact with animals.

Answer 39

Staphylococcus saprophyticus

Question 40

Urinary tract infection in young sexually active adolescent female (Cystitis)

Answer 40

staphylococcus saprophyticus

Question 41

Urinary tract infection in young sexually active adolescent female (Cystitis)

Question 42

burning sensation when passing urine, the urge to urinate more often than usual, a dripping effect' after urination, weak bladder, a bloated feeling with sharp razor pains in the lower abdomen around the bladder and ovary areas, and razor-like pains during sexual intercourse.

Answer 42

staphylococcus saprophyticus

Question 43

Staphylococcus saprophyticus TREATMENT

Answer 43

Ciprofloxacin Trimethoprim – Sulfamethoxazole Quinolones such as norfloxacin

Question 44

Catalase positive (+); coagulase negative (-), non – mannitol fermenter

Answer 44

Staphylococcus saprophyticus

Question 45

Novobiocin and Nalidixic acid resistant

Answer 45

Staphylococcus saprophyticus

Question 46

novobiocin sensitive

Answer 46

Staphylococcus epidermidis