Gram Positive Bacteria

Gram positive

group of bacteria that have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain used in the Gram staining procedure, making them appear purple under a microscope

What are the species of gram positive bacteria?

Staphylo
Strepto
Entero

Staphylococci are broken into what two categories

Coagulase negative- S. Epidermidis
Coagulase positive- S. Aureus

Gram positive cocci in clusters

Staphylococci

Is Staphylococcus aureus resistant?

Multi drug resistance- high morbidity and mortality

Resistance: Methicillin-Resistant Staph Aureus (MRSA)

Staphylococcus aureus virulence factors

Attachment - MSCRAMMs

Persistence- Biofilm, SCV, intracellular tolerance

Evading/destroying host defenses- Leukocidins, protein A

Tissue invasion/penetration- proteases, lipases, nucleases

Toxin-mediated disease and/or sepsis- enterotoxins, TSST1, alpha toxin

Staphylococcus aureus infection types

Skin, soft tissue, sinus, pneumonia, osteomyelitis, endocarditis, bloodstream infections, meningitis

Staphylococcus aureus epidemiology

Hospital assoicated - MRSA, reduces fitness, invades population at risk less common virulence factors
Community assoicated- Invades normally healthy, increased fitness, more common virulence factors

Staphylococcus epidermidis infection types

Adheres to prosthetic surfaces: Prosthetic joints, valves, IV catheters, other hardware, surgical site infections, native bone

Gram positive cocci in chains

Streprococcus spp

Two types of strep

B-hemolytic: Group A (pypgenes), Group B(agalactiae) , Group C(equis)

Alpha-hemolytics: Pneumoniae, Viridans streprococci

Strep Pneumoniae infection types

Upper and lower respiratory, CNS (meningitis), Otitis media

Strep Pyogenes infection types

Strep throat, impetigo, cellulitis, necrotizing fasciitis, toxic shock syndrome

Strep Agalactiae infection types

Neonatal sepsis

Immunocompromised adults: Pneumonia, bacteremia, endocarditis, UTI, SSTI

Which streps are treatable with penicillin?

Strep Pyogenes
Strep Agalactiae

Gram positive cocci in chains

Enterococcus spp

Normal flora of GI, mouth, femal egeneital tract

Enterococcus spp

Two types of Enterococcus spp

E. Faecalis: More common, pathogenic & antibiotic susceptible

E. Faecium: Nosocomial, antibiotic resistant

Is Enterococcus spp resistant?

Less pathogenic but highly drug resistant

Commonly encountered antibiotic resistance:
Fluoroquinolones
Vanco
Tetracyclines
Penicillins
Cephalosporins
Aminoglycosides

Enterococcus spp infection types

Bacteremia, UTI, wounds

Gram positive anaerobes

Normal flora of mouth/upper respiratory tract, GI, skin, and genitourinary tract- GI infections, skin infections, aspiration pneumonia

Gram positive cocci( mouth)
Peptococcus, PeptostreptococcusZ
Mostly PCN & clindaymycin suscpetible

Gram positive Bacilli (lower GI)
Clostridium, propionibacterium lactobacillus, actinomyces

Bacillus Spp

Human cases usually associated with exposure to infected animals or contaminated animal products

Bacillus anthracis→ ANthrax

3 routes of exposure:
Cutaneous
GI
Inhalation

Clostridioides

C. Perfringens
C. Diff

Listeria monocytogenes

Intracellular pathogen

Who is susceptible: Neonates, pregnant women, elderly, transplant

Treatmet: Beta lactam + Aminoglycoside

Transmission: Food

Infections: CNS meningitis, endocarditis, blood, septic emboil