Staphylococcus aureus: Gram-Positive Cocci

Gram Positive Cocci: Staphylococcus aureus

• Staphylococcus aureus is an opportunistic pathogen and a component of the indigenous microbiota of the skin and anterior nares.
• Classified as Gram-positive, with cocci in grape-like clusters, nonmotile, and facultative anaerobic.
• Found in human noses and skin, it spreads through direct contact with nasal secretions or indirectly via fomites, and through ingestion of contaminated food.
• Virulence factors include exoenzymes like coagulase, catalase, hyaluronidase, fibrinolysin, and protease, as well as toxins like Exfoliatin, Enterotoxin, and Toxic Shock Syndrome Toxin-1 (TSS).
• Diseases caused encompass skin infections (impetigo, boils, carbuncles, stye), Staphylococcal Scalded Skin Syndrome (SSSS) due to Exfoliatin toxin, Toxic Shock Syndrome (due to TSS-1 toxin), and Staphylococcal Food Poisoning because of preformed enterotoxin.
• Management and prevention strategies consist of appropriate antibiotic therapy, handwashing, and proper disposal of respiratory secretions and soiled linens.

Gram Positive Cocci: Streptococcus pyogenes

• Streptococcus pyogenes, also known as "Group A streptococcus," is an opportunistic pathogen and part of the indigenous microbiota of the upper respiratory tract (URT).
• Classified as Gram-positive, with cocci in chains, nonmotile, and facultative anaerobic.
• Found in the human upper respiratory tract, it is transmitted through respiratory droplets or indirect contact through fomites.
• Virulence factors comprise exoenzymes like Hyaluronidase and fibrinolysin, along with toxins like Erythrogenic toxin (Scarlet Fever) and Streptolysin O (Pharyngitis), Exotoxin B (Necrotizing Fasciitis), and M protein.
• Diseases caused includes Streptococcal pharyngitis, Scarlet fever (caused by strains that produce erythrogenic toxin), and Necrotizing fasciitis (due to Exotoxin B).
• Rheumatic Fever involving M proteins which produces an autoimmune response to the proteins found on the joint, heart and brain through MOLECULAR MIMICRY, and Post-Streptococcal Glomerulonephritis where M protein incites immune complex deposition on renal tubules
• Management and prevention involve appropriate antibiotic therapy, handwashing, and proper disposal of respiratory secretions; soiled linens.

Gram Positive Cocci: Streptococcus pneumoniae

• Streptococcus pneumoniae, referred to as "Pneumococcus", is an opportunistic pathogen.
• Classified as Gram-positive, with "lancet-shaped" diplococci and nonmotile.
• Found in the human URT, it spreads through respiratory droplets.
• Virulence factor is capsule.
• Diseases caused includes Pneumonia, and Otitis media.
• Management and prevention include appropriate antibiotic therapy, Pneumococcal vaccine, and supportive therapy such as O2 therapy and adequate fluid intake.

Gram Negative Cocci: Neisseria gonorrhoeae

• Neisseria gonorrhoeae, known as "Gonococcus," is consistently pathogenic.
• Classified as Gram-negative, featuring kidney bean-shaped diplococci with concave sides facing each other, and is nonmotile, facultative anaerobic, and possesses pili.
• Resides in the human genital tract and transmits via sexual contact (orogenital or anogenital) or from passage through the birth canal.
• Virulence factors include pili and endotoxin.
• Diseases caused include Gonorrhea, and Ophthalmia neonatorum - conjunctivitis of the newborn.
• Management and prevention involve appropriate antibiotic therapy, sex education, and contact tracing of sexual partners.

Gram Negative Cocci: Neisseria meningitidis

• Neisseria meningitidis, "Meningococcus" is classified as Gram-negative, featuring kidney bean-shaped diplococci with concave sides facing each other.
• Transmitted through respiratory droplets or fomites, residing in the human URT.
• Its virulence factors include a capsule, pili, and endotoxin.
• Disease caused is Bacterial meningitis.
• Management and prevention include appropriate antibiotic therapy, and vigorous supportive care

Gram Positive Bacilli: Corynebacterium diphtheriae

• Corynebacterium diphtheriae is always a pathogen
• Gram-positive with club-shaped bacilli arranged in V or L configurations, also with encapsulated and pili
• Found in Human URT
• Transmitted through respiratory droplets and Indirect contact
• Virulence Factors of capsule, and exotoxin
• Diphtheria involves mild sore throat with fever and pseudomembrane formation on pharynx with bull's neck appearance
• Managed and prevented using vaccine, antibiotic therapy and supportive therapy

Gram Positive Bacilli: Clostridium botulinum

• Clostridium botulinum is always a soil-dwelling pathogen that is gram positive
• The anaerobic bacteria has bacilli morphology and is flagellated
• Bulging spores from canned goods and raw honey
• Botulinum toxin is known as one of the most potent ones known to man
• Botulism is a paralytic illness caused by a potent neurotoxin (Botulinum Toxin) and ingestion of contaminated food.
• Health education on proper food preparation and antibiotic therapy

Gram Positive Bacilli: Clostridium tetani

• Clostridium tetani is always a pathogen
• Gram positive with tennis racket morphology and motile
• Found in soil, transmitted through unsterile metals and materials
• Causing tetanus, by way of tetanospasmin (Toxin)
• Acute onset of hypertonia or painful muscular contractions - strong muscle spasm trismus
• Tig (Tet IG) with 72 hours
• Wound debridement

Miscellaneous bacteria and other factors regarding Clostridium tetani

• AR: Anaerobe, with terminal spore & peritrichous flagella.
• The bacteria is transmitted by umbilical stump of the newborn, ear piercings.
• Inhibits release of GABA and glycine.
• Causes risus sardonicus, opisthotonos, respiratory muscle paralysis, laryngospasm.
• Treat using Tetanus Toxoid vaccine & DPT vaccine, antibiotic medication, and supportive therapy