Staphylococcus, Micrococcus and similar organisms

Rothia sp

The colonies of this organism resemble staphylococcus, but adhere to the agar because of their capsule ("sticky staph")

Slide coagulase test

The original iteration of the coagulase test

MIC Testing

This Is routinely done on all Staphylococcus aureus isolates, as well as clinically significant isolates of Coagulase Negative Staphylococci, because the susceptibility patterns of these organisms cannot be predicted

Techoic acid

This cell wall constituent of Staphylococcus aureus acts as a virulence factor by facilitating adherence to mucosal surfaces

Peptidoglycan

This cell wall constituent of Staphylococcus aureus acts as a virulence factor by having endotoxin-like activity, Activation of complement, and Aggregation of PMN's (abscess formation)

Scalded skin syndrome (ritter disease)

This disease caused by Staphylococcus aureus results in bullous formations over large areas of body with subsequent sloughing of superficial skin, primarily affecting infants and young children. Toxins are responsible for symptoms

Fibrinolysin

This enzyme produced by Staphylococcus aureus acts as a virulence factor by breaking down fibrin clots, allowing the spread of infection

Coagulase

This enzyme produced by Staphylococcus aureus acts as a virulence factor by converting fibrinogen to fibrin to protect the organism from phagocytosis

Hemolysin

This enzyme produced by Staphylococcus aureus acts as a virulence factor by having a lethal effect on many PMN's and RBC's Staphylococcus aureus may produce 4 different enzymes: α, β, γ, δ α - extensive tissue damage β - ' hot cold lysin'

Catalase

This enzyme produced by Staphylococcus aureus acts as a virulence factor by inactivating toxic hydrogen peroxide formed by phagocytic cells after ingestion.

community acquired MRSA

This infection is becoming more prevalent in children and adults, associated with skin and soft tissue infections presenting as a "spider bite." Can also cause necrotizing pneumonia, and may produce Panton-Valentine Leukocidin (PVL) (cytotoxin)

Protein A

This virulence factor of Staphylococcus aureus Interferes with ingestion by PMN's, Activation of complement, and hypersensitivity reactions

48 hours

Another way to help control hospital infections of MSSA / MRSA is to change IV catheters this often

Staphylococcus aureus

Approximately 10-20% of the general population may carry this organism asymptomatically in their nostrils (nares), and up to 50% of health care workers are colonized as normal flora Most strains (99%) of this organism are resistant to penicillin due to beta-lactamase production (plasmid mediated)

VISA (Vancomycin Intermediate Staphylococcus aureus)

1. A strain of MRSA that is intermediate resistant to vancomycin (glycopeptide). 2. Definition: vancomycin MIC 4-8 µg/ml. 3. The organism has a thick cell wall which contributes to its resistance to vancomycin. 4. All of these isolates have been MRSA to date. 5. This organism is important because of the severely limited treatment options.

blue

The color of a positive microdase test

Staphylococcus lugdunensis

1988 - first description of this organism May have virulence similar to S. aureus Normal skin flora, but can cause serious infections Associated with variety of infections: ◦Cardiovascular infections (endocarditis, native valves) ◦Osteomyelitis ◦Prosthetic joint infections ◦Bloodstream infections ◦Skin and soft tissue infections Properties that promote tissue adherence ◦Adhesins ◦Binding to scar tissue ◦Production of a biofilm Treatment ◦Resistance to beta lactams is rare (<15%) ◦Removal of infected material

Staphylococcus saprophyticus

Creamy white colonies on blood agar, non-hemolytic ◦Strongly pigmented 'drops of paint' Coagulase negative Resistant to 5 µg Novobicin disk (<16 mm) Important cause of UTI in young adult females and in patients who have indwelling catheters Treated empirically Routine susceptibility testing of urine isolates of this organism is not advised, because infections respond to concentrations achieved in urine of antimicrobial agents commonly used to treat acute, uncomplicated urinary tract infections (e.g. nitrofurantoin, trimethoprim/sulfa, or a fluoroquinolone)

Staphylococcus aureus

Diseases caused by this organism are characteristically: 1. Pyogenic (fever producing), suppurative (pus producing) 2. Swelling, redness, increase in temperature around area This organism is the most virulent of its genus due to several virulence factors

MRSA (Methicillin Resistant Staphylococcus Aureus)

First reported in Great Britain in 1961 These are strains of Staphylococcus aureus that carry the mecA gene, which encodes for penicillin binding protein (PBP2a). PBP2a does not allow the drug to bind to the bacterial cell. The mecA gene is plasmid mediated, carried on a mobile DNA element (SSSmec) that mediates wide dissemination of antibiotic resistance. Resistant to penicillins, beta lactams, cephalosporins. Currently accounts for >60% of hospital acquired Staphylococcus aureus infections.

cephalosporins

If an organism is resistant to oxacillin, they are considered resistant to all antibiotics in this class

Fibrinogen, IgG specific for Protein A, IgG specific for cell surface antigen

In the latex agglutination test (Staphaurex Plus), what are the latex beads coated with?

vanA

MRSA that has received a plasmid containing this gene from VRE is VRSA (Vancomycin Resistant Staphylococcus Aureus) There have been 14 reported cases of VRSA (Vancomycin Resistant Staphylococcus Aureus) in the U.S as of June 2017.

Staphylococcus lugdunensis

Of the Staphylococcus, Micrococcus and similar organisms, this organism has a characteristic bleach-like odor

Staphylococcus lugdunensis

Of the Staphylococcus, Micrococcus and similar organisms, this organism is Ornithine decarboxylase positive (ODC)

Staphylococcus lugdunensis

Of the Staphylococcus, Micrococcus and similar organisms, this organism is catalase positive and coagulase negative ("weird coagulase"), but is not Staphylococcus aureus

Rothia sp

Of the Staphylococcus, Micrococcus and similar organisms, this organism is the only catalase negative to weak positive

CNS (coagulase negative staphylococcus sp)

Of the Staphylococcus, Micrococcus, and similar organisms, These organisms are increasing in frequency of isolation with increased use of implantable medical devices: heart valves, catheters, prosthetic joints, etc.

CNS (coagulase negative Staphylococcus sp)

Of the Staphylococcus, Micrococcus, and similar organisms, These organisms are ubiquitous colonizers, frequently found as contaminants

CNS (coagulase negative Staphylococcus sp)

Of the Staphylococcus, Micrococcus, and similar organisms, these organisms are both catalase positive, and coagulase negative

CNS (coagulase negative Staphylococcus sp)

Of the Staphylococcus, Micrococcus, and similar organisms, these organisms are prevalent as a healthcare associated infection (HAI)

PBP2a

Rapid immunochromatographic assay is performed on Staphylococcus aureus to detect this protein to determine if it is MRSA or MSSA

Micrococcus sp

Some strains of this organism produce pigments and appear yellow, pink, orange or tan

indophenol

The product of the microdase test

clumping (fibrin strands)

The product of the slide coagulase test

clot formation (fibrin)

The product of the tube coagulase test

H2O, and O2 (bubbles)

The products of the catalase test

H2O2 (Hydrogen peroxide)

The reactant of the catalase test

Tetramethyl-p-phenylenediamine

The reactant of the microdase test

Bound coagulase (clumping factor), and EDTA plasma (fibrinogen)

The reactants of the slide coagulase test

Extracellular (free) coagulase, and EDTA plasma (fibrinogen)

The reactants of the tube coagulase test

Penicillin Binding Protein

These are a group of proteins that are characterized by their affinity for and binding of penicillin, and beta lactam drugs. These proteins bind B-lactam antibiotics. MRSA produces a version of this protein which is encoded by the mecA gene Detection of these proteins identifies strains that not only harbor the mecA gene, but also produce the protein that confers resistance to methicillin

Staphylococcus sp., Micrococcus sp., and similar organisms

These organisms are gram positive cocci, catalase positive, non-motile, non-sporeforming, aerobic or facultatively aerobic, and have circular, smooth colonies that are usually white to yellow in color

CNS (coagulase negative Staphylococcus sp)

These organisms grow on Mannitol Salt agar (but no mannitol fermentation)

Enterotoxin

These toxins produced by Staphylococcus aureus act as virulence factors by differing methods. A through E are associated with food poisoning, and TSST-1 is associated with toxic shock syndrome TSST-1 is a pyrogenic toxin superantigen that Induces fever and has the ability to stimulate proliferation of T-lymphocytes without regard to antigenic specificity

Toxic shock syndrome

This infection is caused by TSST-1 enterotoxins of Staphylococcus aureus. Low levels of magnesium contribute to increased level of toxin production Characteristics: ◦Hypotension ◦Fever >102.0, chills ◦Rash - diffuse macular erythroderma ◦Vomiting and/or diarrhea ◦Headache, may be disoriented ◦Desquamation of the palms and soles ◦Associated with tampon usage ◦May be a complication of abscesses, osteomyelitis, and post-surgical wound infections Many of the fibers previously used in tampons combine with magnesium This causes a magnesium deficient environment Excess production of TSST-1 by certain strains of SA occurs when the organisms are grown in an environment deficient in magnesium. TSST-1 = pyrogenic exotoxin C

food poisoning

This infection is caused by enterotoxins A and B of Staphylococcus aureus, which are produced at room temperature. The result of improper food handling Symptoms: ◦Rapid onset (2-6 hours): nausea, vomiting, diarrhea, abdominal pain and cramping ◦Rapid recovery (6-8 hours) for most patients ◦Rapidly progressing due to preformed toxins in food Organisms destroyed by cooking, but not toxin itself Culprits: potato salad (mayo) - picnic foods, processed meats, dairy

Rothia sp

This is an opportunistic organism, and has been associated with edocarditis (valves), bacteremia, peritonitis

DMSO (dimethyl sulfoxide)

This is the chemical that is used in the microdase test which interacts with the cell wall of the organism, allowing for the Tetramethyl-p-phenylenediamine to get through the gram positive cell wall

Latex agglutination test (Staphaurex Plus)

This is the current iteration of the coagulase test

mecA

This is the gene that is detected for molecular identification of MRSA from swabs or blood cultures.

Spectra MRSA agar

This is the media used for nasal screens performed on patients with risk factors (according to established protocol) Risk factors include recent hospital stay, nursing home resident, recent antibiotic use, open, draining wound Done in conjunction with infection prevention ◦Selective and differential chromogenic media to detect nasal colonization with MRSA ◦Uses a novel chromagen that yields blue color as a result of phosphatase activity. ◦(FYI, there's also one of these for VRE)

tube coagulase test

This is the second iteration of the coagulase test

Staphylococcus aureus

This organism is DNAse positive

MRSA

This organism is a common Hospital acquired infection (HAI)

Rothia sp

This organism is emerging as a pathogen in patients with malignancies and BM transplants (ICH)

Micrococcus sp

This organism is lysostaphin resistant

Staphylococcus aureus

This organism is lysostaphin sensitive

Staphylococcus sp

This organism is lysostaphin susceptible

Staphylococcus aureus

This organism is most commonly associated with these infections: Toxin mediated ◦Food Poisoning ◦Toxic Shock Syndrome ◦Scalded Skin Syndrome Cutaneous ◦Cellulitis (inflammation) ◦Folliculitis (inflammation) ◦Furuncles (nodules formed in skin) ◦Carbuncles (necrotizing, skin and subQ) ◦Impetigo (inflammatory skin disease characterized by isolated pustules) Other infections include: ◦Post surgical wound infections ◦Bronchopneumonia (elderly) ◦Bacteremia ◦Osteomyelitis ◦Endocarditis

Staphylococcus sp

This organism is non-motile

Micrococcus sp

This organism is part of normal flora, opportunistic (may become more important in the immunocompromised host), or can be a contaminant

Micrococcus sp

This organism is resistant to the antibiotic furazolidone

Staphylococcus sp

This organism is susceptible to the antibiotic furazolidone

Staphylococcus aureus

This organism produces extracellular toxins A, B, C2, E and TSST-1

Staphylococcus sp

This organism reduces nitrates to nitrites

Staphylococcus sp

This organism will grow in a 7.5-10% NaCl solution

Staphylococcus aureus

This organism will grow on Mannitol Salt agar - ferments mannitol (yellow zone)

D-zone Test

This test is used to detect inducible Clindamycin resistance in Staphylococcus species and Group B Beta Streptococcus. The D-Zone test is performed only when the organism is resistant to Erythromycin and sensitive to Clindamycin. Positive = organism not susceptible to clindamycin Erythromycin resistant isolates of Staph aureus, coag neg staph, and GBS may have inducible resistance to clindamycin. This is encoded by the 'erm' gene. The 'erm' gene requires an inducing agent to express resistance to clindamycin. Erythomycin can act as such an inducer. On a blood agar plate, inoculated with the test organism for confluent grow, place a clindamycin disk and an erythromycin disk 15 mm apart. After 24 hours, observe. Inducible resistance is indicated by a flattening of the clindamycin zone between the two disks.

Microdase

This test is used to differentiate Micrococcus species from other catalase positive gram positive cocci (modified to use with gram positive cell wall vs. gram negative cell wall)

catalase

This test is used to differentiate Staphylococcus from streptococcus, and the name is also the catalyst of the test

Exfoliatin

This toxin produced by Staphylococcus aureus acts as a virulence factor by (proteolytic) dissolving the mucopolysaccharide matrix of the epidermis, associated with scalded skin syndrome - the epidermis peels away leaving a moist red area.

Leukocidin

This toxin produced by Staphylococcus aureus acts as a virulence factor by acting exclusively on PMN's and macrophages, altering cell permeability (Panton-Valentine leukocidin)

capsule formation (capsular polysaccharide)

This virulence factor of Staphylococcus Aureus may prevent ingestion of the organism by PMN's, and may promote adherence to cells and prosthetic devices

Hand washing

What is the best way to decrease the spread of MRSA / MSSA infection in the hospital

Staphylococcus epidermidis

White, or off-white creamy raised colonies on blood agar Normal human flora of skin and mucous membranes Associated with bacterial endocarditis following insertion of artificial prosthetic heart valves, IV catheters, prosthetic orthopedic devices, CNS shunt, and CAPD patients 75-80% of isolates from this group of organisms are this organism. This organism is most commonly associated with human infections, infecting prosthetic heart valves.

Rothia mucilaginosa, Rothia dentocariosa

formerly known as stomatococcus, these two organisms are found as colonizers of the human oral cavity

tube coagulase test

free coagulase activates prothrombin, converting fibrinogen to fibrin is the method of this test

Micrococcus sp

of the Staphylococcus, Micrococcus and similar organisms, This is the only organism that is microdase positive

Staphylococcus aureus

of the Staphylococcus, Micrococcus and similar organisms, this is the only organism that is coagulase positive

Micrococcus sp

of the Staphylococcus, Micrococcus and similar organisms, this is the only organism that is truly bacitracin sensitive

Staphylococcus lugdunensis

of the Staphylococcus, Micrococcus and similar organisms, this organism is PYR positive

cytochrome oxidase

the catalyst of the microdase test