D

MICRO 18

Staphylococcus Genus Characteristics (Q1)

  • Gram positive

  • Clusters arrangement

  • Catalase positive

  • Coccus shaped

Streptococcus Genus Characteristics (Q2)

  • Catalase negative

  • Gram positive

  • Coccus shaped

  • Chains arrangement

Neisseria Genus Characteristics (Q3)

  • Gram negative

  • Coccus shaped

Differentiating Staphylococcus Species (Q4)

  • Perform a coagulase test

Coagulase Test for Staphylococcus Species (Q5)

  • Staphylococcus aureus is positive .... Staphylococcus epidermidis and Staphylococcus saprophyticus are negative

Staphylococcus aureus Locations (Q6)

  • Skin and anterior nares (nostrils)

Staphylococcus aureus Virulence Factors (Q7)

  1. Capsule – aids in biofilm formation to colonize medical equipment, causing opportunistic infections.

  2. Enterotoxin – causes Staphylococcal food poisoning, found in cream-based food and processed meats.

  3. Exfoliative toxin – causes skin separation in Staphylococcal scalded skin syndrome.

  4. Toxic shock syndrome toxin (TSST) – leads to high fever, hypotension, shock, and death.

Staphylococcus aureus Skin Infections (Q8)

  1. Folliculitis – superficial inflammation at the hair follicle.

  2. Furuncle – deeper inflammation of a hair follicle, can progress to a pustule.

  3. Carbuncle – clusters of furuncles, leading to deeper lesions, can cause death in severe cases.

  4. Impetigo – bubble-like swellings that break and peel away, common in newborns.

Staphylococcus aureus Systemic Infections (Q9)

  1. Lung – Pneumonia

  2. Bone – Osteomyelitis

  3. Heart – Endocarditis

  4. Blood – Septicemia/sepsis

MRSA (Q10)

  • A strain of Staphylococcus aureus that makes an enzyme called penicillinase, making it resistant to penicillin.

Coagulase Negative Staphylococcal Species: Staphylococcus epidermidis (Q11)

  • Lives on the skin

  • Virulence factor: Capsule – causes biofilm formation and colonization of medical devices.

Coagulase Negative Staphylococcal Species: Staphylococcus saprophyticus (Q12)

  • Lives on the skin or sometimes in the vagina

  • Causes urinary tract infections (UTIs) in sexually active women

Beta-Hemolytic Streptococcus Species (Q13)

  • Streptococcus agalactiae

  • Streptococcus pyogenes (Group A Strep or GAS)

  • Enterococcus faecalis

Streptococcus pyogenes Normal Carriage (Q14)

  • Skin and throat

Streptococcus pyogenes Virulence Factors (Q15)

  1. Capsule – Protection from immune system cells.

  2. Streptolysin – A species-specific hemolysin causing beta-hemolysis.

  3. Erythrogenic toxin – Can lead to scarlet fever after a strep throat infection.

  4. Hyaluronidase – Degrades connective tissue, contributing to necrotizing fasciitis.

Localized Infections of Streptococcus pyogenes (Q16)

  1. Erysipelas – Infection that progresses to the dermis and subcutaneous layers, causes redness, fever, and pain.

  2. Necrotizing fasciitis – Flesh-eating disease due to degradation of connective tissue, can lead to death.

  3. Streptococcal pharyngitis – Strep throat or tonsillitis with red throat and pus.

  4. Impetigo – Bubble-like swellings that break and peel away, highly contagious.

Diagnosis and Treatment of Streptococcal Pharyngitis (Q17)

  • Rapid strep test .... penicillin

Sequelae of Strep Throat (Q18)

  1. Affects the kidney – Acute glomerulonephritis

  2. Affects the heart – Rheumatic fever

  3. Leads to endocarditis – Rheumatic fever

  4. Can eventually lead to kidney failure – Acute glomerulonephritis

  5. Can be diagnosed by listening for unusual heart sounds – Rheumatic fever

Beta-Hemolytic Streptococcus agalactiae Characteristics (Q19)

  • Resides in vagina

  • Pregnant women are screened late in pregnancy and given antibiotics during delivery to prevent transmission to newborn

  • Can be transferred to newborns during birth, causing pneumonia, meningitis, permanent damage, or death

Beta-Hemolytic Enterococcus faecalis Characteristics (Q20)

  • Of concern due to VRE (Vancomycin-Resistant Enterococcus)

  • Causes opportunistic infections after surgery or with the use of catheters

  • Resides in the large intestine (colon)

Alpha-Hemolytic Streptococcus Species (Q21)

  • Streptococcus pneumoniae

  • Streptococcus mutans

  • Streptococcus sanguinis

Viridans Group Alpha-Hemolytic Species (Q22)

  • Streptococcus mutans

  • Streptococcus sanguinis

Viridans Group Habitat (Q23)

  • Oral cavity

Viridans Group Characteristics (Q24)

  • Streptococcus mutans: Forms a biofilm leading to dental plaque and caries.

  • Streptococcus sanguinis: Forms a biofilm on the heart leading to endocarditis.

Streptococcus pneumoniae Capsule (Q25)

  • A capsule – an important virulence factor for survival in the human body.

Diseases Caused by Streptococcus pneumoniae (Q26)

  1. M = Meningitis – Fever, stiff neck, headache.

  2. O = Otitis media – Middle ear infection.

  3. P = Pneumonia – Acquired via respiratory droplets or normal flora.

  4. S = Sinusitis – Excessive exudate in the lungs, possibly drowning in secretions.

DRSP (Q27)

  • A strain of Streptococcus pneumoniae that has obtained drug resistance to several antibiotics.

Neisseria Virulence Factor (Q28)

  • IgA protease – Helps evade the immune system by degrading antibodies.

Neisseria gonorrhoeae Characteristics (Q29)

  • Hemorrhaging of blood vessels, petechiae or ecchymosis

  • Discharge from the penis or vagina

  • Can be transmitted to a newborn

  • Can cause pelvic inflammatory disease and infertility in women

  • Can cause gonorrhea

  • Can be transmitted to cause extragenital infections

Neisseria gonorrhoeae Infection in Newborns (Q30)

  • Blindness; that is why babies are given antibiotic drops in their eyes at birth

Neisseria meningitidis Characteristics (Q31)

  • Production of endotoxin can lead to meningococcemia

  • Hemorrhaging of blood vessels, petechiae or ecchymosis

  • Second most common cause of bacterial meningitis

Acinetobacter baumannii Characteristics (Q32)

  • More strains are developing drug resistance, limiting treatments

  • Originally isolated from bed sore infections

  • Originally isolated in injured military personnel