STAPH INFECTION TO STREP INFECTION

BACTE LEC MIDTERMS

Suppurative

Infections caused by S. aureus are what?

Folliculitis, furuncles, bullous impetigo

3 Common infections caused by S. aureus

Folliculitis

is a relatively mild inflammation of a hair follicle or oil gland

Furuncles

an extension of folliculitis are large, raised, superficial abscesses

Carbuncles

occur when larger more invasive lesions develop from multiple furuncles which can progress into deeper tissues

Impetigo contagiosa

staphylococcal pustules are larger and surrounded by a small zone of erythema

Insect or spider bites

Occasionally, superficial Staphylococcal infections can be misidentified as:

Scalded skin syndrome

is a bullous exfoliative dermatitis that occurs primarily in newborns and previously healthy young children

Pemphigus neonatorum

impetigo of the newborn

Exfoliative toxin

causes scalded skin syndrome

Toxic epidermal necrolysis

What is the meaning of TEN?

Drug reactions

Most common cause of TEN

Steroids

TEN can be resolved by the administration of:

aggravated

SSS is \_____________________ by steroids

Toxic shock syndrome

rare but potentially fatal multisystem disease characterized by onset of fever, chills, vomiting, diarrhea, muscle aches and rash which can progress to hypotension and shock

Highly absorbent tampons

TSS was first described in 1978 and was associated with women using:

Menstruating-associated and nonmenstruating-associated

2 categories of TSS

Toxic shock syndrome toxin-1

A superantigen and causes toxic shock syndrome, formerly known as Enterotoxin F

High temperature, rash, dehydration, watery diarrhea and vomiting

Initial clinical presentation of TSS (5)

Enterotoxins A, D, B

Enterotoxins for food poisoning (3)

Nausea, vomiting, abdominal pain, severe cramping

Common symptoms of food poisoning (4)

Staphylococcal bacteremia

Staphylococcus aureus bacteria in the blood

Staphylococcal pneumonia

has been known to occur secondary influenza virus infection

Pneumonia

characterized by multiple abscesses and focal lesions in the pulmonary parenchyma

Staphylococcal osteomyelitis

occurs as a manifestation secondary to bacteremia

Septic arthritis

frequently caused by S. aureus in children, especially with trauma to the extremities

Staphylococcus epidermidis

a common cause of health care-acquired UTIs

Biofilm production

Key component in bacterial pathogenesis and is a complex interaction between host, indwelling device and bacteria

poly-gamma-DL-glutamic acid

provides a protective advantage against host defenses

Staphylococcus saprophyticus

UTI in young women

Staphylococcus lugdunensis

cause both community-associated and hospital-acquired infections

mecA

the gene that encodes oxacillin resistance

Staphylococcus warneri
Staphylococcus capitis
Staphylococcus simulans
Staphylococcus hominis
Staphylococcus schleiferi

Species less commonly seen but established as opportunistic pathogens

Staphylococcus haemolyticus

commonly isolated CoNS reported in wounds, bacteremia, endocarditis and UTIs

Staphylococcus pseudintermedius

pyoderma

Aspirate

Best sample for microscopic examination

Sheep blood agar

Staphylococci grow easily on routine laboratory culture media, particularly in what media?

CHROMagar Staph aureus

a proprietary selective and differential medium for isolation and identification of S. aureus

Methicillin susceptible Staphylococcus aureus

CHROMagar MRSA can further classifc S. aureus into:

round, smooth, white, creamy colonies

Characteristics of Staphylococci on SBA

small to medium sized

Size of S. epidermidis colonies

nonhemolytic

S. epidermidis, hemolytic or nonhemolytic?

Gray to white

Color of S. epidermidis colonies

Staphylococcus saprophyticus

50% of strains producing a yellow pigment, what Staphylococci?

Staphylococcus haemolyticus

medium-sized colonies with moderate or weak hemolysis and variable pigment production, what Staphylococci?

Staphylococcus lugdunensis

Are often hemolytic and medium sized, although small colony variants can occur. What staphylococci?

Staphylococcus saprophyticus
Staphylococcus auricularis
Staphylococcus hominis
Staphylococcus xylosus
Staphylococcus cohnii

Staphylococci that fail to grow or produce acid anaerobically (5)

Microdase disk

can be used to rapidly differentiate staphylococci from micrococci

matrix-assisted laser desorption/ionization time of flight

MALDI-TOF means?

Clumping factor

causes agglutination in human, rabbit, or pig plasma

formerly known as cell-bound coagulase

Tube coagulase method

detects staphylocoagulase or free coagulase

Staphylocoagulase

is an extracellular molecule that causes a clot to form when bacterial cells are incubated with plasma

Coagulase-reacting factor

Staphylocoagulase reacts with a thermo-stable thrombin-like molecule called \_________________________ to form coagulase-CRF complex

coagulase-coagulase-reacting factor complex

resembles thrombin and indirectly concerts fibrinogen to fibrin

Testing for pyrrolidonyl arylamidase activity

can be used to differentiate S. aureus from S. lugdunensis, S. intermedius and S. schleiferi

Negative

S. aureus in test for pyrrolidonyl arylamidase activity

Positive

S. lugdunensis, intermedius, and schleiferi in test for pyrrolidnoyl arylamidase activity

Formation of acetoin from glucose or pyruvate

Voges-Proskauer test positive result

Positive

S. aureus in Voges-Proskauer test

Negative

S. intermedius in Voges-Proskauer test

Coagulase negative staphylococci

Staphylococci that do not produce staphylocoagulase are called?

Novobiocin

S. saprophyticus is resistant to what antibiotic?

B-lactamase

break down the B-lactam ring of many penicillins

Methicillin-resistant Staphylococci

isolates that are resistant to nafcillin or oxacillin have been traditionally termed:

community-associated methicillin-resistant Staphylococcus aureus

these infections can be found in patients who lack traditional health-care associated risk factors

Vancomycin

treatment of choice for MRSA infection

Cefoxitin

a better inducer of mecA-mediated resistance

Borderline oxacillin-resistant Staphylococcus aureus

hyperproducers of B-lactamase

PBP2a

altered penicillin binding protein gene

Vancomycin-intermediate Staphylococcus aureus

VISA stands for:

First recovered in Japan for its resistance to Vancomycin

Clindamycin

macrolide frequently used in staphylococcal skin infections

Lancefield grouping

antigen serogrouping

Streptococcaceae

Streptococcus and Enterococcus spp. belong to what family?

pairs or chains

Morphology of Streptococcus

Enterococcus

formerly known as Group D streptococci

Lactococcus

formerly known as Group N streptococci

Gram-positive

Streptococci in Gram-stain

Negative

Streptococci in Catalase test, positive or negative?

Aerotolerant anaerobes

Streptococci grown in the presence of oxygen but are unable to use oxygen for respiration. Therefore, they are?

C carbohydrate

appears in the cell wall of Streptococci except for many of the viridans group

Rebecca Lancefield

Who classified streptococci based on their cell wall components?

Alpha

Partial hemolysis

Beta

Complete hemolysis

Nonhemolytic

No lysis

Alpha-prime

Small area of intact RBCs around colony surrounded by a wider zone of complete hemolysis

Pyogenic streptococci

B-hemolytic streptococci

Nonpyogenic streptococci

non-B-hemolytic streptococci

Streptococcus pyogenes
Streptococcus agalactiae
Streptococcus dysgalactiae subsp. equisimilis
Streptococcus anginosus group

Pyogenic streptococci isolated frequently from humans

A

Lancefield group of Streptococcus pyogenes

B

Lancefield group of Streptococcus agalactiae

C

Lancefield group of Streptococcus dysgalactiae subspecies equisimilis

D

Lancefield group of Streptococcus bovis group

M protein

virulence factor of Streptococcus pyogenes, causes streptococcal cell to resist phagocytosis and plays a role in adherence of the bacterial cell to mucosal cells

emm

gene that encodes M protein

M1 serotype

pharyngitis

Fibronectin-binding protein

Protein F

Lipoteichoic acid and fibronectin-binding protein

are adhesion molecules that mediate attachment to host epithelial cells

Deoxyribonuclease B

most common Deoxyribonuclease in Streptococcus pyogenes

Streptolysin O

responsible for hemolysis on sheep blood agar plates incubated anaerobically

Streptolysin S

The hemolysis seen around colonies incubated aerobically is due to: