Bacterial Diseases

• The capsule is a major virulence factor for Streptococcus pneumoniae and Niesseria meningitidis

Diseases and Associated Bacteria

• Scalded Skin Syndrome is associated with Staphylococcus aureus
• Toxic Shock Syndrome can be associated with Staphylococcus aureus, and sometimes Group A Streptococcus
• Food poisoning typically results from Staphylococcus aureus
• Dental cavities are associated with Streptococcus mutans
• Rheumatic fever follows infection with Streptococcus pyogenes (Group A Strep)
• Acute glomerulonephritis also follows infection with Streptococcus pyogenes (Group A Strep)
• Gonorrhoeae is caused by Neisseria gonorrhoeae
• Waterhouse-Friderichsen syndrome is caused by Neisseria meningitis
• Impetigo can be caused by Staphylococcus aureus or Streptococcus pyogenes
• Scarlet fever is caused by Streptococcus pyogenes (Group A Strep)
• Necrotizing fasciitis can be caused by Staphylococcus aureus, Streptococcus pyogenes, Clostridium perfringens, Vibrio vulnificus, or Bacteroides fragilis
• Erysipelas comes from Streptococcus pyogenes
• Strep throat comes from Group A, B, C, or G Streptococcus
• Ophthalmia neonatorum comes from many bacteria including Neisseria gonorrhoeae
• PID Pelvic inflammatory disease is associated with Chlamydia and Neisseria gonorrhoeae

George and Gladys Dick Skin Test

• This skin test is used to determine susceptibility to scarlet fever
• Injecting 0.1 cubic cm of scarlet fever toxin into the skin.
• A reddening of the skin in an area over 10 mm (0.4 inch) in diameter within about 24 hours indicates a lack of immunity to the disease.
• The test was developed in 1924 by American physicians George Dick and Gladys Dick.

Schultz Charlton Skin Test

• The test is a skin test for scarlet fever
• Uses antitoxin to the erythrogenic toxin of Streptococcus pyogenes subcutaneously
• Blanching of the rash in the area around the injection site is a positive reaction.

Superantigen

• This is a substance (as an enterotoxin)
• An antigen is capable of stimulating much larger numbers of T cells than an ordinary antigen
• Super antigens can harm the human body due to excessive inflammation

ASO (Antistreptolysin O) Test

• This determines if a strep infection with group A Streptococcus is the cause of glomerulonephritis kidney disease or rheumatic fever
• It is an antibody Test

Anti DNase B

• Anti DNase B antibodies react against the exoenzyme desoxyribonuclease B produced by streptococci
• Detects antibodies providing evidence of an existing or past streptococcal infection like rheumatic fever, scarlet fever, tonsillitis, glomerulonephritis
• The antibody reaction against streptococcal DNase B starts later than the antibody production against streptolysin O, but it can then be detected on a greater percentage of patients
• An increase in the antistreptolysin concentration rarely occurs with skin infections, while a rise in the Anti-DNase B titer can be observed

PVL (Panton-Valentine Leukocidin)

• PVL is a cytotoxin-one of the B-pore-forming toxins
• Found in community-associated MRSA isolates
• It causes necrotic lesions involving the skin or mucosa, including necrotic hemorrhagic pneumonia
• PVL creates pores in the membranes of infected cells
• It is produced from the genetic material of a bacteriophage that infects Staphylococcus aureus, making it more virulent

Protein A

• Staphylococcus aureus utilizes Protein A, along with a host of other proteins and surface factors to aid its survival and, thus, virulence
• Protein A helps inhibit phagocytic engulfment and acts as an immunological disguise

Coagulase

• Coagulase is a protein enzyme produced by several microorganisms that enables the conversion of fibrinogen to fibrin
• Used to distinguish between different types of Staphylococcus isolates
• S. aureus is generally coagulase-positive
• A negative coagulase test would instead show the presence of coagulase-negative organisms such as S. epidermidis or S. saprophyticus
• Coagulase is tightly bound to the surface of the bacterium S. aureus and can coat its surface with fibrin upon contact with blood
• The fibrin clot may protect the bacterium from phagocytosis and isolate it from other defenses of the host

Erythrogenic Toxin

• Streptococcal pyrogenic exotoxins also known as erythrogenic toxins, are exotoxins secreted by strains of the bacterial species Streptococcus pyogenes
• Strains that secrete the toxin carry a bacteriophage
• Erythrogenic toxins are known to damage the plasma membranes of blood capillaries under the skin and produce a red skin rash (characteristic of scarlet fever)

M Protein

• M protein is strongly anti-phagocytic and is the major virulence factor for group A streptococci (Streptococcus pyogenes)
• Cross-reactivity of anti-M protein antibodies with heart muscle has been suggested to be associated in some way with rheumatic fever
• The M protein is a surface antigen

Streptococcus Pneumoniae Vaccine

• Prevnar, a heptavalent pneumococcal conjugate vaccine (PCV 7), was recommended for children aged 2-23 months and at-risk children aged 24-59 months in 2000
• The normal four-dose series is given at 2, 4, 6 and 12-14 months of age
• In February 2010, a pneumococcal conjugate vaccine which protects against an additional six serotypes was introduced (PCV 13/brand name: Prevnar 13)
• On 10 June 2021, a pneumococcal conjugate vaccine which protects against 20 serotypes was approved with the brand name Prevnar 20
• In April 2023, the FDA approved the use of Prevnar 20 vaccine to prevent pneumococcal disease in children aged six weeks to 17 years

Neisseria Meningitidis Vaccine

• MENVEO is a vaccine indicated for active immunization to prevent invasive meningococcal disease caused by Neisseria meningitidis serogroups A, C, Y, and W-135 in individuals 2 months through 55 years of age
• MENVEO does not prevent N. meningitidis serogroup B infections
• There is a separate vaccine for serotype B

Infections and Diseases caused by: Group A Strep (S. pyogenes)

• The major ones are sepsis, impetigo, Strep throat, scarlet fever, rheumatic fever, post streptococcal glomerulonephritis, erysipelas, necrotizing fasciitis, and spinal meningitis
• Group A strep can infect any organ in the human body

Infections and Diseases caused by: Group B Strep (S. agalactiae)

• The major bacteria that causes spinal meningitis of the newborn
• Causes fewer infections in adults than Group A strep
• It can get into any organ

Infections and Diseases caused by: Groups C and G Strep

• Cause strep throat but not the sequelae such as Rheumatic fever or acute glomerulonephritis
• They can get into any organ but the infection rate is less than group A Strep
• They do not cause hospital infections

Infections and Diseases caused by: Group D Strep( including Enterococcus faecium and Enterococcus faecalis)

• The enterococci can cause endocarditis, spinal meningitis, Urinary tract infections
• They can infect any organ in the human body
• Many strains are antibiotic resistant

Infections and Diseases caused by: S. aureus

• Sepsis, Food poisoning, scalded skin syndrome, Toxic shock syndrome, impetigo, UTI, boils
• It can infect any organ in the body

Infections and Diseases caused by: S. epidermidis

• No information provided in text

Infections and Diseases caused by: S. saprophyticus

• UTI infections, especially in females who are becoming sexually active

Infections and Diseases caused by: Viridans Streptococci

• They are normal flora of the mouth
• If they enter the blood they can cause endocarditis
• They may occasionally cause neonatal infections
• They may be involved in mouth infections

Infections and Diseases caused by: S. gallolyticus (S. bovis)

• Streptococcus bovis (S. bovis) bacteria are associated with colorectal cancer and adenoma
• S. bovis is currently named S. gallolyticus
• 25 to 80% of patients with S. bovis/gallolyticus bacteremia have concomitant colorectal tumors
• It is also an important cause of bacteremia and endocarditis in adults

Infections and Diseases caused by: S. mutans

• As a major etiological agent of human dental caries, Streptococcus mutans resides primarily in biofilms that form on the tooth surfaces, also known as dental plaque
• In addition to caries, S. mutans is responsible for cases of infective endocarditis
• It belongs to the Viridans Streptococcus group

Infections and Diseases caused by: S. pneumoniae

• Leading cause of lobar pneumonia in adults
• Can cause sepsis and spinal meningitis
• In children it is a common cause of ear infections
• Can cause brain abscesses, infectious arthritis, corneal infections and conjunctivitis

Infections and Diseases caused by: N. gonorrhoeae

• Neisseria gonorrhoeae, also known as gonococcus (singular) or gonococci (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Neisser in 1879
• It causes the sexually transmitted genitourinary infection gonorrhea as well as other forms of gonococcal disease including disseminated gonococcemia, septic arthritis, and gonococcal ophthalmia neonatorum
• It can also cause pelvic inflammatory disease
• Additional infections that can occur are conjunctivitis, spinal meningitis and endocarditis

Infections and Diseases caused by: N. meningitidis

• Neisseria meningitidis, often referred to as the meningococcus, is a Gram-negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis
• The bacterium is referred to as a coccus because it is round, and more specifically a diplococcus because of its tendency to form pairs
• Septicemia caused by N. meningitidis has been linked to infant deaths
• Severe complications include the Waterhouse-Friderichsen syndrome, a massive hemorrhage into the adrenal glands that causes circulatory collapse

Infections and Diseases caused by: N. lactamica

• This species is most commonly carried by young children

• There is an inverse relationship between colonization by N. lactamica and Neisseria meningitidis

• Carriage of N. lactamica has been associated with decreased incidence of invasive meningococcal disease

• The erythrogenic toxin produced with scarlet fever infections depends on a bacteriophage being inside the bacteria

• Panton Valentine leucocidin (PVL) is dependent on a bacteriophage being inside the S. aureus

Antibiotics - Novobiocin

• It can be used as a antibiotic disc identification since Staphylococcus epidermidis is sensitive and Staphylococcus saprophyticus is resistant

Abbreviations

• MRSA: Methicillin Resistant Staphylococcus aureus
• MSSA: Methicillin Sensitive Staphylococcus aureus
• hVISA: heterogenous Vancomycin Intermediate Staphylococcus aureus
• VRSA: Vancomycin resistant Staphylococcus aureus
• VRE: Vancomycin Resistant Enterococci

Treatment for MRSA

• Vancomycin, linezolid, daptomycin, bactrim

Treatment for VRE

• Daptomycin, Linezolid and The combination of daptomycin and ampicillin is another option to treat VRE infections, especially for bacteremia

Antibiotics

• A combination of azithromycin and ceftriaxone can be used to treat gonorrhoeae

• N. meningitidis is often treated with ceftriaxone

• Carries of N. Meningitidis can be treated with Rifampin or minocycline

• Staphylococcus is positive for the enzyme catalase

• Neisseria is positive for the enzyme cytochrome oxidase

S. aureus, S. epidermidis, and S. saprophyticus lab tests

• ONLY S. aureus is coagulase positive, all other members of the Staphylococcus group are coagulase negative

• An alternate test is Protein A, again only S. aureus is positive

• A novobiocin disc can be used to separate S. epidermidis (sensitive) and S. saprophyticus (resistant)

• All members of the Staphylococcus group are catalase positive

• Additionally< S. aureus is usually beta hemolytic and the other members are usually negative for beta hemolysis

• S. aureus usually ferments Mannitol and most other species are negative

• N. gonorrhoeae ferments only glucose and N. meningitidis ferments glucose and maltose

Thayer Martin agar

• Thayer Martin is a chocolate agar(lysed sheep red blood cells)

• The released nutrient are requires for the growth of > meningitidis AND N. gonorrhoeae

• Nystatin is added to prevent the growth of yeast and fungi

• Colistin is added to prevent the growth of most competing gram-negative bacteria

• Vancomycin is added to prevent the growth of Gram-positive bacteria

• N. Gonorrhoeae and N. meningitidis are capnophiles

• The Viridans Streptococci and streptococcus pneumoniae both give alpha hemolysis

Viridans Versus S. Pneumoniae

• Viridans is Insoluble in bile and pneumoniae is Soluble
• Viridans Not a fermenter and pneumoniae is Fermenter with acid production
• Viridans is Not sensitive to optochin and pneumoniae is Sensitive
• Viridans is Non pathogenic to mice and pneumoniae is Pathogenic
• Viridans is Negative under Quellung test and pneumoniae is Positive

Case Studies

• Acute POST STREPTOCOCCAL GLOMEULONEPHRITS This is the most-likely sequelae since there is blood in the urine
• The ASO test is usually positive for both Rheumatic fever and Acute POST STREPTOCOCCAL GLOMEULONEPHRITIS
• Group B strep fits the gram stain results and Group B is the bacteria that most often caused spinal meningitis of the newborn
• NEISSERIA GONORRHOEAE Since the bacteria is a gram-negative cocci we can eliminate all Staphylococcus and Streptococcus species
• N. gonorrhoeae is the most-likely gram -negative cocci to get into the synovial fluid of the knee
• STREPTOCOCCUS PNEUMONIAE This bacteria is most likely to cause pneumonia and it does produce a capsule which is the major virulence factor
• STAPHYLOCOCCUS AUREUS S. aureus grows on a mannitol plate and it also ferments the sugar mannitol
• The phenol red pH indicator then turns yellow(acid)