Staph

Cards (74)

  • Gram-positive cocci

    • Staphylococcus
    • Rothia
    • Planococcus
    • Micrococcus
    • Gemella
    • Macrococcus
    • Salinicoccus
    • Stomatococcus
    • Leuconostoc
    • Streptococcus
    • Alloiococcus
    • Pediococcus
    • Lactococcus
    • Aerococcus
  • Gram-positive cocci

    • High in peptidoglycan, and low in lipid content (Cell Wall)
    • Alcohols and other solvents do not penetrate the Gram (+) cell wall → causes the cell wall to tighten, shrink, and crenate, thereby locking in the primary stain used for Gram staining (Crystal Violet)
    • Natural inhabitants of Skin and Mucous Membrane
    • Can be ubiquitous in the environment
    • Infection is through direct contact from an infected person, or contaminated objects (fomite)
    • Infections or exposure to these organisms lead to accumulation of neutrophils, bacterial cells, and fluids at the site → Pyogenic Infection
  • Among these, Staphylococcus and Micrococcus are Catalase positive, whereas Streptococcus is Catalase negative
  • Reclassification of Gram Positive Cocci
    • In 1996: Bergey's Manual of Systematic Bacteriology included 4 genera under the Family Micrococcaceae: Micrococcus, Staphylococcus, Planococcus, Stomatococcus
    • Recent edition only includes 2 families: Family Staphylococcaceae and Family Micrococcaceae
  • Family Staphylococcaceae
    • Staphylococcus
    • Gemella
    • Macrococcus
    • Salinicoccus
  • Staphylococcus
    • Major human pathogen
    • Colony size is about 12 um
  • Macrococcus
    Quite similar to Staphylococcus, but able to produce a slightly larger type of colony, around 12.5 um, and it is relatively non-pathogenic
  • Family Micrococcaceae
    • Micrococcus
    • Arthrobacteria
    • Kocuria
  • Micrococcus
    • Tetrads, pairs, or clusters
    • Usual colony size is around 0.51.5 um in diameter
    • Can colonize the skin but rarely infectious
  • Stomatococcus mucilaginosus
    • Only member of the Genus Stomatococcus
    • Reclassified under Rothia as Rothia mucilaginosus
    • Considered to be a normal microbiota of the human upper respiratory tract
    • Cannot grow in the presence of 5% NaCl
    • Weakly catalase (+), coagulase (-) and has a capsule
    • Emerging pathogen in immunosuppressed patients
  • Clinically Significant Staphylococcus
    • S. aureus
    • S. epidermidis
    • S. saprophyticus
  • Staphylococcus aureus
    • 10% - 30% carriers (present in the anterior nares or skin)
    • Transmission through direct contact, fomites, poor hygiene
    • Can cause a variety of infections such as abscesses, respiratory tract infections, pneumonia, arthritis, sepsis, endocarditis, meningitis, osteomyelitis
    • Infections can manifest depending on the virulence of strain, size of inoculum, and immune status
  • Staphylococcus aureus Virulence Factors
    • Surface Structures
    • Enzymes
    • Toxins
  • Staphylococcus aureus Surface Structures
    • Protein A (binds to Fc region of IgG, affects immediate and delayed hypersensitivity reactions)
    • Capsular polysaccharide (anti-phagocytic, enhances binding to host cells and prosthetics)
    • Peptidoglycan and Teichoic Acid (chemoattractant for neutrophils, activates complement, elicits production of IL-1 and opsonic Abs by monocytes, mediates adhesion by binding to tissue fibronectin)
  • Staphylococcus aureus Enzymes
    • Catalase
    • Coagulase (bound and free)
    • Staphylokinase
    • Lipase
    • Hyaluronidase
    • DNase
    • Beta lactamase
  • Staphylococcus aureus Toxins
    • Exfoliatin
    • Leukocidin
    • Hemolysins (alpha, beta, gamma, delta)
    • Enterotoxins (heat-stable, types A-I, responsible for food poisoning)
    • Superantigens (enterotoxins, TSST-1)
  • Hydrolyzes tissue through cleaving the stratum granulosum materials

    This is responsible for the SSSS or the Staphylococcus Scalded Skin Syndrome
  • Leukocidin
    Toxin that can lyse neutrophils and macrophages, thereby inhibiting phagocytosis
  • Hemolysins
    • Alpha
    • Beta
    • Gamma
    • Delta
  • Hemolysins
    Can lyse erythrocytes and are actually toxic also to leukocytes
  • Enterotoxins
    Heat-stable CHONs; food poisoning (enterotoxin A and B)
  • S. aureus are able to produce 7 types of heat-stable proteins (A, B, C, D, E, H, and I)
  • In particular, A and B is responsible for a lot of food poisoning cases
  • Superantigens
    • Enterotoxins
    • TSST-1
  • Superantigens
    Able to trigger the immune system to release a large amount of cytokines into the system, and when cytokines are released in large numbers, they case havoc. They can trigger a lot of signs and symptoms of different infections casued by S. aureus.
  • Staphylococcus aureus Disease Process
    1. SAU → invades tissues and produce toxins
    2. Organisms spread (site of carriage) → site of infection (breaks on the skin)
    3. The portal of entry is typically the breaks on the skin such as; surgical wounds, skin abrasions, lacerations, or punctures
    4. Upon entry, the; Organism → Blood → Lungs, bones, liver, brain, or heart
    5. Entry → staphylococcemia → systemic infection → organ infection
  • Symptoms of infection
    • Redness
    • Swelling, and the likes
  • Types of Staphylococcal Disease
    • Local Abscess
    • Focal suppuration
  • Folliculitis
    The inflammation of hair follicles, commonly seen in the back area, chest, arms, and sometimes in the buttocks portion
  • Furuncles (Boils)

    A panful infection that forms arounf a hair follicle and is characterized by the presence of pus
  • Carbuncles
    A collection of boils that develop under the skin (typically more than 20)
  • Sty
    Red, painful lump near the edge of your eyelid, look like a boil or pimple
  • Osteomyelitis
    Starts from an infected tissue near a bone and has spread to the bone, can be seen as a complication in patients with diabetes mellitus or those with atherosclerosis as a result of trauma or injury to the infected site
  • Empyema
    Lung infectio characterized by the presence of pus in different areas of the lungs – it could be the lung tissue itself or it could be in the pleural membranes
  • Impetigo/ Pyoderma
    A superficial skin infection that starts with the reddening of the skin which may involve the soft tissues. it develops into fluid-filled lesions → eventually bursts, creating a lesion that appear to be constantly weeping → exudates and transudates will flow out from those regions
  • Diseases caused by toxin elaboration (Exotoxin Elaboration)
    • Food poisoning
    • Scalded Skin Syndrome
    • Toxic Shock Syndrome
  • Food poisoning
    Enterotoxins A and B, Nausea, vomiting, and abdominal pain
  • Scalded Skin Syndrome
    Epidermolytic toxin/ exfoliatin = Exfoliation, Blisters form and eventually burst. The blisters mimics scalded skin
  • Toxic Shock Syndrome
    Multisystem disease, TSST-1 producing strains of SAU, Characterized by hypotension (very low blood pressure), septic shock, fever, desquamation of palms and soles, chills, headache, and vomiting
  • TSS is not exclusive to women only, as it can also afflict men and children