CO2026 Gram-Positive Bacteria

What gram-positive bacteria does the following describe?

-cocci

-catalase positive

-coagulase positive

-mannitol fermentation positive

Staphylococcus aureus

Where is staphyloccocus aureus found?

in normal flora of skin, nose

Bone infections, joint infections, otitis externa (ear infection), folliculits, impetigo abscesses, cellulitis, toxic shock syndrome, and scalded-skin syndrome are all symptoms of being infected by what microbe?

Staphylococcocus aureus

Resistance S.aureus has ______ which is an alternate PBP that beta-lactams cannot bind to.

MecA

Staph aureus has many virulence factors and pathogenetic factors. Name them.

-Protein A which binds to Fc of antibodies (antiphagocytic)

-Pantone-Valentine Leucocidin (destroys white blood cells, necrotic infection, common in skin infections)

-Exfoliative toxin (loss of cell-to-cell contact, Scalded-skin syndrome)

-MecA (methicillin resistance)

What gram-positive bacteria does the following describe?

-cocci

-catalase positive

-coagulase negative

-does not ferment mannitol

Staphylococcus epidermidis

How is Staphyloccocus epidermidis transmitted?

inoculation of normal flora in skin to other areas

What is the only gram-positive cocci that is diplo? (lacent diplococci)

Streptococcus pneumoniae

What is the biggest risk factor for being infected by Staphyloccocus epidermidis? How is the bacteria spread?

foreign materials (prosthetics, catheters); respiratory droplets/aerosols, endogenous spread from our own flora

Slime layer/glycocalyx formation that is sticky as well as MecA are characteristics of what bacteria? What are the symptoms of this infection?

Staphylococcus epidermidis- prosthetic joint/bone infections, wound infections that are opportunistic with slow onset

Which of the following gram-positive bacteria does this describe?

-lacent diplococci

-catalase negative

-hemolysis on blood agar

-capsule

-soluble in bile

Streptoccocus pneumoniae

What can Streptoccocus pneumoniae cause in children? WHat about adults over 65? (HINT: think disease)

children- otitis media, sinusitis

adults over 65 - pneumonia, meningitis

Streptoccocus pneumonia is spread by what?

human-only (oropharnyx)- endogenous spread

What are the 2 virulence factors/pathogenesis that Streptococcus pneumoniae takes?

Polysaccharide capsule (antiphagocytic), IgA protease

How can Streptococcus pneumoniae be prevented?

vaccinations with either polysaccharide capsules conjugated to protein or the capsules only

Which of the gram-positive bacteria does the following described?

-cocci in chains

-catalase-negative

-beta-hemolytic

-bacitracin sensitive

Streptoccocus pyogenes

Where is Streptoccocus pyogenes found? How is it spread?

human-ONLY (oropharynx, transient skin)

-endogenous spread

-respiratory droplets

-direct contact (impetigo)

Which bacteria can cause Group A strep, strep throat, impetigo, necrotizing fasciitis, cellulitis, erysipelas, and rheumatic fever (strep throat, scarlet fever, or impetigo)?

Streptoccocus pyogenes (photo of erysipelas)

What can make toxins that cause the rash in Scarlet Fever when infected with Streptoccocus pyogenes?

Pyrogenic exotoxin A or B --> superantigen

What are some of the pathogenesis/virulence factors of Streptoccocus pyogenes?

-hydraluronic capsule

-M protein

-Streptolysin O

-DNase B (deoxyribonuclease)

-Pyogenic exotoxin (superantigen)

Which gram-positive bacteria does the following described?

-cocci in chains

-catalase negative

-alpha hemolytic

-optochin resistant

Viridans Streptococci

Where is Viridans Streptococci found? How is it transmitted?

human-only in oropharynx normal flora; spread endogenously through poor dental hygiene, major surgery

What are some disease caused by being infected with Viridans Streptococci?

dental caries, periodontal disease, endocarditis

Biofilm formation in tooth enamel or heart valve adhesion is commonly seen in what organism?

Viridan Streptococci

Sometimes, dentists will give a _____________ antibiotic prior to major dental surgery to prevent infection of ______ ________.

prophylactic antibiotic to prevent Viridans Streptococci

Which 2 gram-positive rods are obligate anaerobes? Which one is the non-spore former?

Cutibacterium acnes (NON-spore former) and Clostridium perfringes

Where do Cutibacterium acnes live?

fatty acids in sebum (commensal- a part of skin flora)

How is Cutibacterium acnes transmitted? What does it cause?

endogenous overgrowth of skin flora; acne vulgaris

Which gram-positive bacteria does the following describe?

-rods

-obligate anaerobe

-spore-former

Clostridium perfringes

What is the reservoir for Clostridium perfringes? How can it be transmitted?

endospores in soil, environment

-direct inoculation of spores to deep wound

-sharing/using dirty needles

-ingestion of undercooked meat (1 of the most common causes of food poisoning)

What is the biggest risk factor for Clostridium perfringes?

traumatic entry of spores in wounds (deep puncture wound after motorbike accident)

What is the pathogenesis of Clostridium perfringes?

-Alpha toxin- phospholipase C and sphingomyelinase

-Beta toxin- cytotoxin (hole-puncher)

-Invasin enzymes (hyaluronidase)

-capsule

What are some symptoms or physical characteristics of being infected by Clostridium perfringes?

necrotic destruction of muscles/tissues, pockets of air/gas under skin, purple bullae (necrosis)

Which gram-positive rod is diagnosed using double hemolysis on blood agar and also detects leicithinase activity (alpha toxin) on egg yolk agar?

Clostridium perfringes

Which gram-positive bacteria has a unique capsule of Poly-D-gamma-glutamic acid?

Bacillus anthracis

Which two gram-positive rods are non-spore forming?

Cutibacterium acnes and cornebacterium diptheriae

Which two gram-positive rods are spore forming?

Bacillus anthracis and clostridium perfringes

What gram-positive bacteria does the following describe?

-rods in chains

-spore-former

-non-motile

-non-hemolytic

-poly-D-gamma-glutamic acid capsule

Bacillus anthracis

Where does Bacillus anthracic exist? How is it transmitted to the cutaneous gastrointestinal and pulmonary?

endospores in environment, soil

-Cutaneous: spore inoculated directly into skin, germinate locally

-GI: spores ingested, germinate in stomach

-Pulmonary: spores are inhaled, germinate in lungs

The epidemiology of this bacteria is zoonotic, particularly ruminate herbivores as they eat the grass where the spores are present. A risk factor for getting infected would be working with livestock. It can also be used as a bioweapon. Which gram-positive bacteria does this best describe?

Bacillus anthracis

What are the symptoms in someone who develops a cutaneous infection of Bacillus anthracis?

painless, pruritic black eschar at inoculation site with massive edema around (necrotic ulceration)

What is the pathogenesis of Bacillus anthracis? How can you diagnose this bacterial infection?

spores, anthrax toxins (protective (B portion of AB), lethal, and edema), capsule with unique poly-D-gamma-glutamic acid; PCR

Which gram-positive is described in the following?

-rods with clubbed ends

-metachromatic granules

-non-spore-former

-non-motile

-aerobic

Corynebacterium diptheriae

Which 2 gram-positive rods are aerobic?

Bacillus anthracis and Corynebacterium diptheriae

What is the reservoir of Corynebacterium diptheriae and how is it transmitted?

reservoir: human only

transmission: person-person through aerosols, respiratory droplets

What areas are endemic to Corynebacterium diptheriae? What are some risk factors in developing the infection?

Epidemiology: Haiti, Dominican Republic, Asia & South Pacific, Eastern Europe, Middle East

Risk factors: unvaccinated, war or natural disaster, immunocompromised, less than 5 years of age

What are some of the symptoms of Diptheria (caused by Corynebacterium diptheriae)?

Respiratory issues

-First symptoms: sore throat, malaise, low-grade fever, dysphagia

-thick, grey pseudomembrane that can block throat and stop breathing

-Bull neck: swelling of cervical lymph nodes

The Diptheria toxin was originally acquired through lysogenic conversion (bacteriophage) transduction. It uses the ___ toxin which inactivates EF2, preventing ___________.

AB toxin; preventing protein synthesis

How do you prevent Corynebacterium diptheriae?

toxoid vaccination