Normal Microbial Flora and Their Importance

Flashcards covering definitions, types, body site distributions, acquisition, influencing factors, functions, and opportunistic pathogenicity of normal microbial flora based on the lecture by Dr. Lawson S. D.

What is the definition of normal microbial flora (normal microbiota)?

Normal microbial flora refers to the population of microorganisms (including bacteria, fungi, protozoa, and viruses) that inhabit various body sites of humans without causing disease under normal conditions.

How are resident flora distinguished from transient flora?

Resident flora permanently colonize particular body sites and re-establish after disturbances, whereas transient flora are temporarily present and can be displaced by resident flora or eliminated by immune mechanisms.

How do commensal flora and mutualistic flora differ in their host relationship?

Commensal flora benefit from the host without causing harm, while mutualistic flora provide benefits to the host while also gaining benefit themselves.

Which bacterial species form the normal microbial flora of the skin?

Staphylococcus epidermidis, Propionibacterium acnes, and Corynebacterium spp.

Which microorganisms represent the normal flora of the oral cavity?

Streptococcus mutans, Neisseria spp., and Actinomyces spp.

Which normal flora bacteria reside in the respiratory tract of carriers?

Staphylococcus aureus and Streptococcus pneumoniae.

Which bacterial species make up the normal flora of the gastrointestinal tract?

Escherichia coli, Lactobacillus spp., and Bacteroides spp.

What microorganisms compose the normal flora of the genitourinary tract?

Lactobacillus spp. and Streptococcus spp. in the vagina, and coagulase-negative staphylococci in the urethra.

How is normal microbial flora acquired during birth and early life?

Initial exposure occurs at birth during passage through the birth canal, followed by postnatal exposure (contact with mother, caregivers, air, food) and environmental exposure (surfaces, diet, interactions).

What factors influence the composition of normal flora in human body sites?

Age and hormonal status, diet and nutrition, hygiene and antibiotic use, host immune status, environmental exposure, and site-specific pH, oxygen tension, and temperature.

How does normal flora protect against pathogens through colonization resistance?

Normal flora compete with pathogens for nutrients and space, and produce bacteriocins.

What metabolic contributions and specific vitamins are synthesized by normal flora?

Normal flora aid in digestion and synthesize vitamins such as vitamin K and vitamin B12.

What are the primary functional benefits provided by normal microbial flora?

Protection against pathogens (colonization resistance), immune system modulation, metabolic contributions, maintenance of mucosal integrity, and detoxification of toxins and xenobiotics.

How can Staphylococcus epidermidis cause an opportunistic infection?

Through skin breaches, where Staphylococcus epidermidis can cause wound infections.

Under what condition does Candida albicans become an opportunistic pathogen causing candidiasis?

Under host immune suppression, which leads to Candida albicans overgrowth.

How does antibiotic therapy lead to Clostridium difficile colitis?

Antibiotic therapy disrupts normal flora balance, leading to overgrowth of Clostridium difficile and resulting in colitis.

What opportunistic infection occurs when Escherichia coli migrates from its primary site?

Migration of E. coli from the intestine can cause urinary tract infections.

What is the clinical relationship between normal flora and nosocomial infections?

Nosocomial infections often arise from endogenous flora.

What clinical interventions help maintain or restore a healthy microbiota balance?

Antibiotic stewardship to prevent microbiota disruption, and the use of probiotics and prebiotics to restore gut balance.