Staph

• 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 1 – 2 um
• Macrococcus


  Quite similar to Staphylococcus, but able to produce a slightly larger type of colony, around 1 – 2.5 um, and it is relatively non-pathogenic
• Family Micrococcaceae

  • Micrococcus
  • Arthrobacteria
  • Kocuria
• Micrococcus


  • Tetrads, pairs, or clusters
  • Usual colony size is around 0.5 – 1.5 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