MIDTERM: Staphylococcus & Micrococcus Flashcards by Jannine Mikaela

This term means “bunches of grapes”

Staphle

How well did you know this?

Not at all

Perfectly

Colonies are produced after how many hours of incubation?

18-24 hours

How well did you know this?

Not at all

Perfectly

Describe the usually appearance of Staphylococcus in culture?

medium size, cream colored, white or rarely light gold and buttery looking

How well did you know this?

Not at all

Perfectly

These are responsible for several suppurative infections. These organisms are normal inhabitants of the skin and mucous membranes of humans and other animals.

Staphylococci

How well did you know this?

Not at all

Perfectly

This the most virulent species of staphylococci encountered

Staphylococcus areus

How well did you know this?

Not at all

Perfectly

The most clinically significant species. It causes various cutaneous infections and purulent abscesses.

Staphylococcus areus

How well did you know this?

Not at all

Perfectly

State the superficial skin and soft tissues infections caused by S. areus

Impetigo and cellulitis

How well did you know this?

Not at all

Perfectly

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) )

How well did you know this?

Not at all

Perfectly

The reason why your S. aureus causes a lot of disease

Virulence factors

How well did you know this?

Not at all

Perfectly

A protein that has sites that is able to bind the FC portion of IgG.

Protein A

How well did you know this?

Not at all

Perfectly

This help penicillinase (betalactamase) to disrupt the beta lactam portion of the molecule rendering the antibiotic useless against this organism

Coagulase

How well did you know this?

Not at all

Perfectly

This protein protects the organism from opsonization and phagocytosis of neutrophils

Protein A

How well did you know this?

Not at all

Perfectly

An enzyme that can even lead to fibrin formation around the bacteria and protect it from phagocytosis

Coagulase

How well did you know this?

Not at all

Perfectly

They are able to destroy or hemolysed your red blood cells. (They can even destroy neutrophils, macrophages, and platelet)

Hemolysin

How well did you know this?

Not at all

Perfectly

Acts on sphingomyelin in the plasma membrane of erythrocytes and is also called the “hot-cold” lysin

Beta toxins (sphingomyelinase C)

How well did you know this?

Not at all

Perfectly

This test performed in the laboratory to identify group B streptococci.

Christie, Atkins, and Munch- Petersen(CAMP)test

How well did you know this?

Not at all

Perfectly

Disrupts smooth muscle in blood vessels and is toxic to erythrocytes, leukocytes, hepatocytes, and platelets

Alpha toxins

How well did you know this?

Not at all

Perfectly

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)

How well did you know this?

Not at all

Perfectly

Produced by all strains of S. aureus and may actually function in association with the Panton- Valentine leukocidin (PVL).

Gamma toxins

How well did you know this?

Not at all

Perfectly

Cytolytic to erythrocytes and demonstrates nonspecific membrane toxicity to other mammalian cells.

Delta toxins

How well did you know this?

Not at all

Perfectly

Enumerate the species of Staphylococcus that have been identified as capable of producing delta toxins

S. aureus
S. epidermidis
S. haemolyticus

How well did you know this?

Not at all

Perfectly

An exotoxin lethal to polymorphonuclear leukocytes

Panton - Valentine leukocidin (PVL)

How well did you know this?

Not at all

Perfectly

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)

How well did you know this?

Not at all

Perfectly

Spreading factor; Permits bacteria to spread through connective tissues

Hyaluronidase

How well did you know this?

Not at all

Perfectly

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 (

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