MIDTERMS: L1 - GRAM POSITIVE COCCI Flashcards
T OR F: Gram positive cocci has high peptidoglycan and high level of lipid
F
Gram positive cocci are natural inhabitants of ______
Skin and Mucous membrane
Characterization of infection of gram positive cocci:
Pus, pyogenic infection - Acc. of neutrophils, bacterial cells, fluids at site
Staphylococcus and Stomatococcus are catalase (+ or -)
Catalase +
Catalase -
Streptococcus
In 1996: Bergey’s Manual of Systematic Bacteriology, what are the 4 genera of family micrococcaceae
Micrococcus, Planococcus, Staphylococcus, Stomatoccus
2 Families (Recent ed)
Family Staphylococcaceae and Micrococcaceae
Major human pathogen
Staphylococcus (1-2um colony)
Difference between staphylococcus and macrococcus
Macrococcus - larger type of colony (1-2.5um) and non pathogenic
Stomatococcus mucilaginosus - old and new genus and name
From stomatococcus, reclassified under Rothia > Rothia mucilaginosus
Emerging pathogen in immunosuprressed patients - R. mucilaginosus. Isolated in blood cultures in patients with _____
Endocarditis and septiciemia
Micrococcus vs Staphylococcus
- Obligate aerobe
Micrococcus
Micrococcus vs Staphylococcus
- Lysostaphin and Furazolidone susceptible
Staphylococcus
Micrococcus vs Staphylococcus
- Bacitracin susceptible
Micrococcus
Micrococcus vs Staphylococcus
- Fermentative (Carbohydrate utilization medium)
Staphylococcus
Micrococcus vs Staphylococcus
- Modified oxidase test negative
Staphylococcus
Micrococcus and Staphylococcus similarities:
- Inhabitants of the skin
- Similar colony appearance
- Gram positive cocci
- Catalase positive
Staphylococcus bacteria are nonmotile and spore forming (T or F)
False (no flagella and non-spore forming
Clinically significant staphylococcus
S. aureus, S. epidermidis, S. saprophyticus
Virulence of strain by S. aureus
Surface structures and Enzymes or toxins
Protein A
Attach to a portion reserved for host or immune cells, interferes with complement fixation and opsonization, and phagocytosis
Mediates adhesion by binding to tissue fibronectin
Teichoic acid
3 surface structures of S. aureus
Protein A, Capsular polysachharide, Peptidoglycan and Teichoic acid
Catalase
Enzyme inactivates hydrogen peroxide (usually in Neutrophils)
2 types of coagulase (by S. aureus) and differentiate:
- Bound and Free Coagulase
- BC: bound to bacterial cell wall and reacts directly with fibrinogen
FC: inactivate CRP > form fibrin clot
Hydrolyzes lipids and plasma
Lipase
Hydrolyzing hyaluronic acid in connective tissue
Hyaluronidase
Hydrolyzes and inactivate penicillin thru breaking down B lactam ring and penicillin molecule
Beta lactamase (Specifically penicillinase)
Responsible for SSSS
Exfoliatin - hydrolyze tissue thru cleaving stratum granulosum
Lyse erythrocyte
Hemolysin
7 heat stable proteins
ABCDEHI
2 enterotoxin responsible in food poisoning
Enterotoxin A and B
Trigger the immune system to release a large
amount of cytokines in the system which causes havoc
Superantigens (enterotoxins and TSST-10
Types of staph diseases;
- Local Abscesses
- Focal Suppuration
- Diseases caused by toxin elaboration
Inflammation of hair follicles
Folliculitis
Collection of boils that develop under the skin
Carbuncles
Painful infection that forms around a hair follicle and is characterized by a presence of pus
Furuncles
Can bee seen in patients with diabetes mellitus
or atherosclerosis as a result of trauma or
injury to the infected site
Osteomyelitis
Impetigo/Pyoderma
Develops into fluid-filled lesions which eventually burst creating lesions that appear to be constantly weeping
- common in infants and newborns
Most significant CoNS:
- Staphylococcus epidermidis
- Staphylococcus saprophyticus
T or F
S. epidermidis - resistant to novobiocin and DNase negative
False
T or F
S. saprophyticus resistant to novobiocin
True
S. saprophyticus virulence factor
Ability to adhere to epithelial cells of the urinary tract
MRSA - used oxacillin, cloxacillin for detection and diagnosis
True
Enumerate specimens for processing+
Wound, blood, sputum, urine
T or F
- Do direct gram stain from specimen
- Gram (+) cocci & neutrophils are noted
True
Enumerate culture medium for Staphylococcus+
Sheeps’ BAP, CNA, MSA, Chromogenic Agar
SBPA pigment color
White to golden yellow
Contents of CNA and its purpose
Colistin - disrupt cell membrane of gram neg
Nalidixic Acid - Blocks DNA replication and membrane integrity of gram negative bacteria
Contents of MSA
Mannitol and Phenol red
Color of SAU in MSA
Yellow
Color of S. epidermidis in MSA
Pink - no acid change since mannitol is not fermented
Chromogenic Agar - colors of bacteria
SAU - deep pink to fuschia colonies
S. epi - partially or completely inhibited
S. saph - turqoise colonies
Yellow pigment for the color of SAU macroscopic colonies
Staphyloxanthin - carotenoid pigmen gold in color
Differentiate Staph from Strep, identify its positive outcome
Catalase test, Effervescence or bubbling - Staphylococcus
I. Coagulase test - differentiates sau from cons
II. Add plasma to test the present of coagulase
T or F
T
- Two types of coagulase test
2. Differentiate - what its detecting, and the result
- Slide and Tube Coagulase test
- Slide - cell bound coagulase, formation of clot
Tube - free coagulase, formation of gel
Latex agglutination - latex particle is coated with _____ and reacts with ______ of SAU
Coated with human plasma fibrinogen and igG, clumping factor and protein A of SAU
EXAMPLE: Staphyloslide Latex Test
Reagent used in Modified Oxidase Test
6% tetramethyl-p-phenylenediamine dihydrochloride in dimethyl sulfoxide
I. In Modified Oxidase test, it will differentiate Staphylococcus and Streptococcus
II. In MO, positive - micrococcus (cytochrome c) with no change in color, negative - staphylococcus with purple color
MOTF
BOTH F
Bacitracin Susceptibility Test
- Differentiates what groups of bacteria
- Interpretation of results:
Differentiate Micrococcus & Rothia from Staphylococcus
Zones > 10 mm = Susceptible; Micrococcus & Rothia
Zones < 10 mm or no zone of inhibition =
Resistant; Staphylococcus
Differentiate S. saprophyticus from other CoNS
Novobiocin Susceptibility Test
POSITIVE RESULT - zone is lesser than or equal to 16mm
Meaning - S. saprophyticus is present
Two DNAse test and its results
Methyl Green - colorless
Toluidine Blue O - bright pink color
Detection of thermostable nuclease
Toluidine Blue O
Test for Detection of Antibiotic-Resistant SAU
Cefoxitin Disk Screen Test, Latex Agglutination for PBP2a, MH Agar with NaCl & 6 ug/mL of Oxacillin, Chromogenic Agar, etection of mecA gene or its Product PBP2a
Positive and negative result of Cefoxitin Disk Screen Test
+MRSA - no zone
MSSA - has zone
Positive and negative result of Latex Agglutination for PBP2a
+MRSA - agglutination within 3 mins
MSSA - no agglutination within 3 mins
Positive and negative result of MH Agar with NaCl & 6 ug/mL of Oxacillin
+MRSA - growth of more than one colony
Non-MRSA - no growth or only one colony growing
Chromogenic Agar results in detection of MRSA
MRSA grow and produce mauve-colored colonies
Turquoise-colored colonies are non-MRSA or MSSA
40% of CoNS are resistant to beta-lactamase resistant
T or F
True
Treatment for acne
Tetracyclines
Usually given for treating MRSA
Vancomycin
S. saprophyticus can be adequately treatetd with antibiotics. What are the usual antibiotic of choice used?
Nitrofurantoin (Macrobid)
Trimethoprim-sulfamethoxazole (TMP-SMX)
