MIDTERM: Staphylococcus & Micrococcus Flashcards
This term means “bunches of grapes”
Staphle
Colonies are produced after how many hours of incubation?
18-24 hours
Describe the usually appearance of Staphylococcus in culture?
medium size, cream colored, white or rarely light gold and buttery looking
These are responsible for several suppurative infections. These organisms are normal inhabitants of the skin and mucous membranes of humans and other animals.
Staphylococci
This the most virulent species of staphylococci encountered
Staphylococcus areus
The most clinically significant species. It causes various cutaneous infections and purulent abscesses.
Staphylococcus areus
State the superficial skin and soft tissues infections caused by S. areus
Impetigo and cellulitis
S. aureus is a common cause of infective endocarditis and toxin-induced disease, such as?
food poisoning, (and is associated with scalded skin syndrome (SSS) and toxic shock syndrome (TSS) )
The reason why your S. aureus causes a lot of disease
Virulence factors
A protein that has sites that is able to bind the FC portion of IgG.
Protein A
This help penicillinase (betalactamase) to disrupt the beta lactam portion of the molecule rendering the antibiotic useless against this organism
Coagulase
This protein protects the organism from opsonization and phagocytosis of neutrophils
Protein A
An enzyme that can even lead to fibrin formation around the bacteria and protect it from phagocytosis
Coagulase
They are able to destroy or hemolysed your red blood cells. (They can even destroy neutrophils, macrophages, and platelet)
Hemolysin
Acts on sphingomyelin in the plasma membrane of erythrocytes and is also called the “hot-cold” lysin
Beta toxins (sphingomyelinase C)
This test performed in the laboratory to identify group B streptococci.
Christie, Atkins, and Munch- Petersen(CAMP)test
Disrupts smooth muscle in blood vessels and is toxic to erythrocytes, leukocytes, hepatocytes, and platelets
Alpha toxins
This toxin is seen as enhanced hemolytic activity on incubation at 37° C and subsequent exposure to cold (4° C).
“hot-cold” feature of Beta toxins (sphingomyelinase C)
Produced by all strains of S. aureus and may actually function in association with the Panton- Valentine leukocidin (PVL).
Gamma toxins
Cytolytic to erythrocytes and demonstrates nonspecific membrane toxicity to other mammalian cells.
Delta toxins
Enumerate the species of Staphylococcus that have been identified as capable of producing delta toxins
S. aureus
S. epidermidis
S. haemolyticus
An exotoxin lethal to polymorphonuclear leukocytes
Panton - Valentine leukocidin (PVL)
Contributes to the invasiveness of the organism by suppressing phagocytosis and has been associated with severe cutaneous infections and necrotizing pneumonia
Panton- Valentine leukocidin (PVL)
Spreading factor; Permits bacteria to spread through connective tissues
Hyaluronidase
it is often associated with community-acquired staphylococcal infections and might be a marker for such infections
Panton-Valentine leukocidin
Breaks down the proteoglycans in our connective tissue
Hyaluronidase
Able to degrade fats and oils that are often accumulated the surface of our body
Lipase
Protein that lyses the formed fibrin clots; similar to streptokinase produced by Streptococcus
Staphylokinase
This particular degradation facilitates the ability of S. aureus to colonize especially our sebaceous glands
Lipase
Destroys protein
Protease
Illness most common in women 15-25 years of age who use tampons during menstruation
Toxic shock syndrome (Exotoxin TSST-1)
Cause of the majority of staphylococcal food poisoning cases but only happens rarely any only be fatal to immunocompromised individuals
Enterotoxins A-E
Cause the epidermal layer of the skin to slough off and are known to cause staphylococcal SSS (Skin Scald Syndrome)
Exfoliative Toxins
Most significant exfoliative toxin
epidermolytic toxin A & B
What is the cause of Toxic Shock Syndrome?
exotoxin-TSST 1 or the pyrogenic exotoxin C
It will cause fever, desquamation, hypotension, and could even lead to bacterial shock and death
Toxic Shock Syndrome
Damages erythrocytes, platelets, and macrophages
Alpha toxin
Found in some CoNS strains as well as S. aureus. Less toxic than other hemolysins
Delta toxins
Also known as sphingomyelinase C
Beta toxin
Polymophonuclear toxicity
Panton-Valentine leukocidin
Disrupts the erythrocyte plasma membranes. Responsible for CAMP assay effectiveness
Beta toxin
Associated with Panton Valentine leukocidin
Gamma toxin
Enzyme that cleaves the ring structure of penicillins and derivative antibiotics making them ineffective
B-lactamase
Permits bacteria to spread through connective tissue
Hyaluronidase
Altered membrane binding protein
Penicillin-binding protein 2
Responsible for a positive tube coagulate test results. Also present in S. intermedius, S. pseudintermedius, S. hyicus, S. deelphini, S. lutrae, S. agnetis, ans some S. schleiferi
Staphylocoagulase
Common to S. aureus and CoNS. Degrades lipids on skin surface making it more susceptible to bacterial entry into epidermal layers
Lipases
A superantigen causing an overactive immune response. Formerly known as enterotoxin F
Toxic shock syndrome toxin- 1
Binds lgG and prevents phagocytosis
Protein A
These cause the majority of staphylococcal food poisoning cases
Enterotoxins A, B, and D
Enterotoxins A-E, G, J are described as?
Heat stable
Enterotoxins that can cause enterocolitis
Enterotoxins B, and C and rarely G and I
Solely responsible for SSS and present in a minority of S. aureus species. May also cause bullous impetigo
Exfoliative toxins
Also known as epidermolytic toxin
Exfoliative toxins
Less virulent than S. aureus and are opportunistic pathogens
S. epidermis
Common source of hospital-acquired infections. UTIs; Prosthetic valve endocarditis
S. epidermis
Their prevalence as healthcare associated pathogens is more related to medical procedure and practices than the organism itself capability to established an infection
S. epidermis
Usually involve implantation of medical devices; infection can even resemble S.aureus infection
S. lugdunensis
This particular genus is resistant to oxacillin
S. lugdunensis
Associated with UTIs in young sexually active females; second most common cause, after E. coli
S. saprophyticus
Commonly isolated CoNS. It has been reported in wounds, bacteremia, endocarditis, and UTIs
S. haemolyticus
Why does S. lugdunensis resembles S. aureus infection?
both are community-associated and hospital acquired infections
Species less commonly seen but established as opportunistic pathogens
S. warneri
S. capitis
S. simulans
S. hominis
S. schleifer
Sterile site by traumatic introduction
Endogenous strain
Endocarditis caused by this organism is particularly aggressive, frequently requiring valve replacement, and infections have a high mortality rate
S. lugdunensis
This particular organism display resistance to vancomycin
S. haemolyticus
This organism is more virulent than other is known to contain the gene mecA, which encodes oxacillin resistance
S. lugdunensis
Indirect contact:
aerosolized
Direct contact:
person-to- person, fomites
The greatest prevention (of bacterial infections)
strengthen our immune system
and avoid abuse of antibiotics
Staphylococcus is non fastidious and can generally grow on any primary plating media. However, if
you want to be more selective, you can use _________ or ____________
Phenylethyl alcohol (PEA) or Columbia colistin-nalidixic acid (CNA) agars
Staphylococcus aureus growing on Sheep Blood Agar would produced
beta-hemolytic, creamy, buttery-looking colonies
The term “aureus” has something to do with?
production of the golden yellow pigment (Staphyloxanthin)
This agar contains a high concentration of salt (7.5%-10%), the sugar mannitol, and phenol red as the pH indicator
Mannitol Salt Agar
The addition of this substance in MSA makes the medium selective for Staphylococcus
high NaCl concentration (7.5%)
Incorporation of these in MSA distinguishes S. aureus from most CoNS (Coagulase negative staphy)
Mannitol and phenol red
This ferments mannitol and produces a yellow halo on this media as a result of acid production altering the pH
S. aureus
This staphylococci may also ferment mannitol and thus resemble S. aureus on MSA medium
S. saprophyticus
This can be used for the identification of methicillin resistant Staphylococcus aureus (MRSA) isolates through the selective and differential formation of mauve-colored colonies
CHROM Agar
Catalase test detects the presence of what enzyme?
Catalase
These are fastidious, requiring carbon dioxide, hemin, or menadione for growth. These so-called small colony variants (SCVs) grow on media containing blood, forming colonies about one tenth the size of wild-type strains even after 48 hours or more of incubation.
Rare strains of staphylococci
Appear as small, pinpoint, nonhemolytic, and nonpigmented colonies on blood agar
small colony variants of S. aureus
A test that differentiate Catalase positive Micrococcus & Staphyloccocus species from that of Catalase negative Streptococcus
Catalase Test
This enzyme converts hydrogen peroxide into oxygen and water
catalase
How many drop of hydrogen peroxide do you place in a catalase test?
1 drop of 30% or 3% Hydrogen peroxide
Bound coagulase, or “clumping factor”
Slide Coagulase Test
Free coagulase or staphylocoagulase
Tube Coagulase Test
Formerly referred to as cell-bound coagulase, causes agglutination in human, rabbit, or pig plasma.
Clumping factor
An extracellular molecule that causes a clot to form when bacterial cells are incubated with plasma
Staphylocoagulase
This reacts with a thermostable, thrombin-like molecule called coagulase-reacting factor (CRF) to form coagulase-CRF complex
Staphylocoagulase
The positive result of Slide Coagulase test
Clumping within 30 seconds
The positive result of Tube Coagulase Test
Clot formation
How many hours do you incubate the test tube in the Tube Coagulase Test?
4 hours of incubation at 37° C
After four hours of incubation, still no clot appears. What is the next step?
Tube should be left at room temperature and checked the next day
These are the organisms that may present a false positive result in the slide coagulase test
S.lugdunensis
S.schleiferi
These are the organisms that may present a false positive result in the tube coagulase test
S.intermedius
S.hyicus
This is used to differentiate S. aureus (negative) from S. lugdunensis, S. intermedius, and S. schleiferi (positive)
Pyrrolidonyl arylamidase activity or PYR test
What is the positive result for the Voges-Proskauer (VP) Test?
formation of acetoin from
glucose or pyruvate; red color
This is a test to determine whether an organism that is inoculated in the plate is susceptible to 5-ug novobiocin disk
Novobiocin Susceptibility Test
This is the staphylococcus that is resistant to novobiocin
S. saprophyticus
Used to differentiate coagulase-negative staphylococci (CoNS) isolated from urine samples
Novobiocin Susceptibility Test
In Microdase test, what organism/screening plate shows resistance to Bacithracin (Taxo A) and furazolidone (Fx)
Staphylococcus epidermis
A modified oxidase test, detects your Cytochrome C; and is used for differentiating Micrococcus spp. from Staphylococcus spp.
Microdase test
They are particularly useful for the identification of MRSA organisms, which are often weakly positive or negative in the slide coagulase test
Kits (Immunodiagnosis)
Besides detecting protein A and clumping factor, it contains antibodies that bind capsular antigens 5 and 8 or other surface molecules.
Third-generation agglutination kits
Mediated by the mecA gene, which encodes an altered penicillin-binding protein, PBP-2a.
B-Lactamase
Due to the gene mecA which is carried in a mobile cassette known as SCCmec
MRSA
What is the cause of why a lot of strain displays resistance against methicillin, nafcillin, and oxacillin medications?
The production of Beta-lactamase
When using a cefoxitin disk, isolates ____ is considered as
susceptible and those with zone sizes that are _______ are reported as oxacillin-resistant
> 22 mm and less or equal
(</= 21 mm), respectively
The gold standard for MRSA detection
Presence of mecA gene; molecular nucleic acid probes or pCR amplification
What agar do we use to screen isolates of S. aureus for oxacillin resistance?
Mueller Hinton agar (supplemented with 4% sodium chloride)
Resistance to macrolide is mediated by:
Clindamycin
Efflux pump, MRSA
Methylase enzyme that alters the ribosomal
binding site. Erm
D-zone test
What test do you perform to determine the organism’s susceptibility to Clindamycin?
Kirby-Bauer test or the Dzone test
In the Dzone test, how do you know if the organism displays resistance to clindamycin in the presence of erythromycin?
Cells will demonstrate a characteristic Dzone pattern
The most commonly used cell wall–active agent that retains activity and is an alternative drug for the treatment of infections with resistant strains.
Vancomycin
Alternatives for vancomycin
Linezolid & Daptomycin
Readily detected using standard microdilution techniques
Vancomycin Resistance
Distance of clindamycin disk from the erythromycin disk in the Dzone test
15 mm
