Staphylococcus saprophyticus

Staphylococcus

• The Staphylococcus genus includes pathogenic and non-pathogenic organisms
• These are gram-positive cocci that commonly occur as irregular clusters of spherical cells
• They are mesophilic, non-spore formers
• These bacteria thrive in organic matter like blood, pus, and tissue fluids

Staphylococcus saprophyticus

• This bacteria is commonly found in soil, water, and on human and animal skin
• It is a coagulase-negative Staphylococcus species that is less pathogenic than Staphylococcus aureus
• It is a significant cause of urinary tract infections (UTIs), primarily in young, sexually active women
• It can adhere to uroepithelial cells, making it a frequent cause of UTIs
• It appears purple under a microscope after Gram staining
• This bacteria does not produce the enzyme coagulase, which distinguishes it from Staphylococcus aureus
• It is resistant to the antibiotic novobiocin, which helps in laboratory identification
• UTIs caused by S. saprophyticus may cause frequent and painful urination as well as discomfort in the bladder area
• Infections are treated with antibiotics, like nitrofurantoin or trimethoprim-sulfamethoxazole

Staphylococcus epidermidis

• This is a common bacterium that lives on human skin
• It is a normal part of the skin's microbiota
• It can become an opportunistic pathogen, especially in healthcare settings
• It is gram-positive, which gives it a thick cell wall that stains purple in Gram stain
• It is coagulase-negative, helping to differentiate it from Staphylococcus aureus
• It is normally harmless, but can cause infections, particularly in people with weakened immune systems or implanted medical devices

General Characteristics of Staphylococcus

• Cocci shaped bacteria are either spherical or oval shaped
• They grow in grape-like clusters due to their division pattern
• Gram-positive species retain the purple color of the stain due to the peptidoglycan layer in their cell walls
• Most Staphylococcus species are non-motile, meaning they lack flagella
• Staphylococcus produce catalase, an enzyme that breaks down hydrogen peroxide into water and oxygen
• This is commonly used to identify the species
• Staphylococcus species are facultative anaerobes and can grow with or without oxygen
• Coagulase-positive species, such as Staphylococcus aureus, produce the enzyme coagulase
• Staphylococcus are non-spore forming, which makes them more susceptible to environmental stressors compared to spores
• Some Staphylococcus species, like Staphylococcus aureus, can grow in high salt environments (10% salt)
• This allows them to grow on human skin and mucosal surfaces
• Certain Staphylococcus species, specifically S. aureus, can form a capsule
• The capsule acts as a protective outer layer, and helps avoid the host immune response

Differentiation of pathogenic and non-pathogenic Staphylococci

• Pathogenic Staphylococci, such as Staphylococcus aureus, produce coagulase to clot plasma
• Non-pathogenic Staphylococci, such as Staphylococcus epidermidis, are coagulase-negative
• Pathogenic strains often produce toxins and enzymes like hemolysins, leukocidins, and exfoliative toxins
• Antibiotic resistance patterns, like methicillin resistance in S. aureus (MRSA), can differentiate strains

Staphylococcus Pathogenicity Factors

• Pathogenicity is established through virulence factors, immune evasion, and tissue destruction
• Staphylococcus aureus is the most well-known pathogenic species
• Staphylococcus epidermidis and other coagulase-negative Staphylococci may cause infections
• Staphylococcus, especially Staphylococcus aureus, has microbial surface components recognizing adhesive matrix molecules (MSCRAMMs)
• MSCRAMMs facilitate adherence to host tissues
• Some strains, especially S. epidermidis, form biofilms that protect bacteria from immune responses and antibiotics
• Capsules prevent phagocytosis by neutrophils
• Protein A binds to the Fc region of IgG, preventing opsonization and phagocytosis
• Coagulase converts fibrinogen to fibrin, forming a clot around bacteria to shield them from immune attack
• Leukocidins, such as Panton-Valentine Leukocidin (PVL), kill white blood cells
• Staphylokinase dissolves clots to facilitate bacterial spread
• Exotoxins, like enterotoxins, cause food poisoning
• Toxic Shock Syndrome Toxin-1 (TSST-1) causes toxic shock syndrome by triggering excessive immune responses
• Exfoliative toxins are responsible for Staphylococcal Scalded Skin Syndrome (SSSS)
• Cytolysins (e.g., α-hemolysin, β-hemolysin) damage host cell membranes
• Hyaluronidase breaks down hyaluronic acid in connective tissues, leading to deeper invasion
• Lipases and proteases degrade host lipids and proteins to facilitate bacterial survival and spread

Diseases Caused by Staphylococcus aureus

• Staphylococcus aureus (S. aureus) can cause infections in the body
• It is found on the skin and in the nose of healthy people
• It can cause diseases when it enters the body through a cut, wound, or contaminated food
• Skin Infections cause red sores, pimples, or painful pus-filled lumps
  • Impetigo presents as contagious sores, common in children
  • Folliculitis exhibits infected hair follicles, causing red bumps
  • Boils are painful, swollen pus-filled lumps
  • Cellulitis is a deep skin infection causing redness and swelling
• Food poisoning via bacteria in contaminated food causes nausea, vomiting, diarrhea, and stomach pain within hours
• Toxic Shock Syndrome (TSS) is a life-threatening condition with fever, rash, low blood pressure, and organ failure
  • TSS is linked to tampons, wounds, or surgery
• Pneumonia can be caused by S. aureus as a severe lung infection causing fever, cough, chest pain, and breathing difficulty
• Osteomyelitis presents as a painful bone infection leading to swelling and fever
  • It is often from wounds or bloodstream infections

Salmonella Typhi

• Salmonella Typhi is a gram-negative, rod-shaped, motile bacterium that causes Typhoid Fever
• It is a serious systemic infection belonging to the Enterobacteriaceae family
• It is primarily transmitted through contaminated food and water
• Humans are the only known hosts
• The bacteria can persist in carriers, such as in the gallbladder, even after the symptoms disappear

Symptoms of Typhoid Fever

• Common symptoms include a sustained high fever of 103–104°F (39–40°C)
• Weakness and exhaustion are also frequent
• A severe headache may occur
• Abdominal pain can be mild to severe
• Bowel changes are possible, including constipation or diarrhea
• A rash of flat, rose-colored spots may appear on the abdomen or chest
• Loss of appetite, coughing, nausea, and prolonged sweating are also symptoms
• Symptoms typically start 8-14 days after infection and may not appear for 6-30 days

Prevention of Typhoid Fever

• Get vaccinated with the typhoid vaccine, especially for travelers to high-risk areas
  • It is not 100% effective, but reduces infection risk
• Safe food and water practices include drinking only boiled or bottled water
  • Avoid ice from unsafe sources
  • Eat freshly cooked and hot food
  • Wash or peel fruits and vegetables thoroughly
• Maintain good hygiene by washing hands with soap and water, especially before eating and after using the toilet
  • Use hand sanitizer if soap is unavailable
  • Avoid close contact with infected individuals
• Improve sanitation by using proper waste disposal and clean water sources
  • Communities should ensure safe sanitation practices to reduce contamination risks
• Avoid close contact with infected individuals by avoiding sharing personal items
  • Practice good hygiene
  • Ensure caregivers follow proper infection control measures
• Contaminated water or water used for washing food from an infected person can carry Salmonella Typhi
• In areas with poor sanitation, untreated water sources (rivers, wells) can be sources of bacteria
• Food can become contaminated if it is washed with contaminated water, handled by an infected person, or stored improperly
• Raw or undercooked foods, like seafood, eggs, and dairy products, are more likely to be contaminated
• Fruits and vegetables that come into contact with contaminated water or soil can also carry bacteria
• The bacteria can be passed from an infected person through stool or urine
• People who do not wash their hands properly can spread the bacteria when handling food
• Those who recover from typhoid fever can become chronic carriers of Salmonella Typhi
  • Carriers may not show symptoms but still shed bacteria through their stool or urine
• Close contact with a carrier, especially in environments with poor hygiene, increases the risk of transmission