Microbiology
Summary
Staphylococcus epidermidis and Staphylococcus saprophyticus are two common staphylococci that inhabit the human skin and mucous membranes. Staph epidermidis often infects artificial joints, indwelling catheters, and implanted heart valves due to its ability to produce copious adherent biofilm, which enables it to stick to metal and plastic surfaces while also protecting it from antibiotics and immune cells. Infections caused by Staph epidermidis are typically treated with vancomycin. This species is also novobiocin-sensitive, which helps distinguish it from Staph saprophyticus.
Staph saprophyticus is associated with honeymoon cystitis and acute bacterial prostatitis. Honeymoon cystitis is a urinary tract infection (UTI) resulting from sexual activity, thought to occur more frequently in women due to the shorter female urethra. Both Staph epidermidis and Staph saprophyticus share the characteristics of being catalase-positive and coagulase-negative, distinguishing them from Staphylococcus aureus, which is coagulase-positive.
Lesson Outline
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FAQs
Staph epidermidis and Staph saprophyticus are both gram-positive, coagulase-negative bacteria commonly found on the skin and mucosal surfaces. They are part of the normal human microbiota and are generally considered opportunistic pathogens. The primary difference between the two is that Staph epidermidis is associated with infections related to artificial implants and indwelling devices, while Staph saprophyticus is more commonly associated with urinary tract infections, particularly honeymoon cystitis.
Biofilms are complex communities of microorganisms encased in a self-produced extracellular matrix that offers protection and enhanced attachment to surfaces. In the case of Staph epidermidis, biofilm formation is a significant virulence factor in the development of infections associated with artificial implants and indwelling devices. The biofilms provide a protective environment for the bacteria, making them more resistant to both the host's immune system and antibacterial treatment, ultimately contributing to the persistence and recurrence of the infection.
Vancomycin is a glycopeptide antibiotic that is often used for the treatment of serious infections caused by gram-positive bacteria, including Staph epidermidis and Staph saprophyticus. It is particularly important in cases where the bacteria are resistant to methicillin or other beta-lactam antibiotics. Vancomycin works by inhibiting the synthesis of the bacterial cell wall, ultimately leading to cell death.
Novobiocin is an antibiotic that selectively inhibits DNA gyrase, an enzyme crucial for bacterial DNA replication. Susceptibility testing using novobiocin can help differentiate Staph saprophyticus from other coagulase-negative staphylococci, such as Staph epidermidis. Staph saprophyticus is characterized by being resistant to novobiocin, while other coagulase-negative staphylococci, including Staph epidermidis, are generally susceptible. This difference in susceptibility can be used in the identification and diagnosis of the causative agent in infections.
Honeymoon cystitis is a term used to describe acute urinary tract infections (UTIs) that occur in sexually active women, particularly following frequent or recent sexual activity. Staph saprophyticus is the second most common cause of uncomplicated UTIs in young women, after Escherichia coli. Its affinity for the genitourinary tract and its ability to adhere to uroepithelial cells makes it a significant causative agent in honeymoon cystitis.
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