UTIs in Women & Vaginal Flora

• HLT203 Lecture 7 focuses on the normal flora of the human body.
• The lecture aims to define normal flora, its occurrence, and location.
• It also covers the types of normal flora, their importance, and symbiosis with hosts.
• It identifies different anatomical sites of normal flora and their organisms, and understanding of opportunistic pathogens.

Normal Flora

• Normal flora, also known as indigenous microbiota, comprises microbes regularly found in specific body regions.
• Normally, they don't cause harm or infection.
• These microbes are present on the skin, eyes (conjunctiva), nose (respiratory tract), mouth (oral cavity), ears, digestive tract, and urogenital tract.
• Bacteria, fungi, and protists are included in this group.
• Viruses and parasites are not considered normal microbial flora.
• Some normal flora perform useful tasks for the host.
• The skin and mucous membranes host a variety of microorganisms classified into two groups.
• Resident flora are permanent members that colonize specific anatomical sites for life.
• Transient flora are temporary and unable to colonize the body for extended periods.
• The composition of normal flora varies with age, sex, diet, development, and environment.
• Healthy human internal tissues and fluids, such as blood, the brain, muscle, and cerebrospinal fluid (CSF), are typically free of microorganisms.

Importance of Normal Flora

• Normal flora protects the host by occupying ecological niches.
• It aids in production of vitamin B and vitamin K in the intestine.
• Normal flora stimulates the immune system by inducing low levels of circulating/secretory antibodies, which can cross-react with pathogens.
• It antagonizes other bacteria through bacteriocin production.

Symbiosis of Microbial Organisms

• Mutualism benefits both the host and the microbe.
• Commensalism benefits one organism while has no effect on the other.
• Parasitism benefits one organism while harming the other, causing disease.

Colonization

• Initial colonization occurs at birth during passage through the birth canal.
• The fetus is sterile in utero.
• Infant feeding leads to the establishment of stable normal flora, influenced by the mother's microflora.

Normal Flora Distribution

• An adult human hosts about 10^12 bacteria on the skin.
• 10^10 bacteria are in the mouth and 10^14 in the gastrointestinal tract.
• The bacterial count exceeds the number of eukaryotic cells in all human tissues and organs.
• 10^14 bacteria compare to 10^13 host cells in the body.

Normal Flora of the Skin

• An adult skin surface is about 2 m².
• The normal flora's density and composition vary by anatomical location.
• High moisture areas like the armpit (axilla) promote bacteria and fungi growth, leading to higher bacterial cell density.
• Most skin microorganisms are found in the epidermis's superficial layers and hair follicle area.
• Examples of skin normal flora include Gram-positive cocci and Gram-positive bacilli.
• Bacteria or their metabolites guard against colonization of dermatophytes fungi or pathogens.

Normal Flora of the Respiratory Tract

• Nares (nostrils) are heavily colonized, predominantly by Gram-positive cocci and Gram-positive bacilli.
• Healthy sinuses are sterile.
• The upper respiratory tract (nasopharynx) is colonized by non-hemolytic Gram-positive cocci, alpha-hemolytic Gram-positive cocci, and Gram-negative cocci/bacilli
• The lower respiratory tract (trachea, bronchi, pulmonary tissues) is usually sterile due to the ciliated epithelium's cleansing action and removal by coughing, sneezing, etc.

Normal Flora of the Urogenital Tract

• Urine is typically sterile.
• Lower urethra parts may be colonized by Gram-positive cocci.
• 80-90% of urinary tract infections in women occur due to the proximity of anus which is source of bacteria.
• Pathogenic bacteria in the urogenital system which can cause infection and inflammation may be Gram negative rods or Gram positive cocci.
• Vagina is colonized normally with:
  • Gram-positive bacilli, e.g., Lactobacillus Spp.
  • Gram-positive cocci
  • Small number of yeasts, mainly Candida albicans
  • Anaerobic Gram-positive bacilli

Normal Flora of the Gastrointestinal Tract (GIT)

• The stomach has few bacteria due to its high acidity (pH=3.0).
• Helicobacter pylori causes more than 95% of gastritis and peptic ulcer cases but can be found in the stomach.
• The small intestine contains small numbers of Gram-positive cocci, Gram-positive anaerobic bacilli, and yeast.
• The large intestine (colon) is the primary site of bacteria in the body.
• 20% of normal feces consists of bacteria mostly come from the colon.
• Gram-negative rods and anaerobic Gram-positive rods, such as Lactobacillus are main bacteria in colon..

Opportunistic Pathogen Problems and Occurrences

• Normal flora can sometimes act as opportunistic pathogens.
• This occurs in immunocompromised or immunodeficient individuals.
• When relocated to unusual anatomic locations can also cause problems.
• Microorganisms can be normally commensal or harmless but cause disease when the host immunity is low.
• Elderly and critically ill or immunosuppressed patients face higher opportunistic pathogen risk
• Suppressed immunity can allow normal flora overpopulation or invasion.
• Disturbance of microflora balance, is likely during broad spectrum antibiotics usages.
• Traumatic introduction of microflora to unusual body areas can trigger infections through injury, cuts, or nosocomial (hospital-acquired) infections.

Pathogenicity of Microbes

• Some bacteria possess "virulence factors" (tiny backpacks) that contains the weapons.
• Virulence factors are features that aid in causing disease or infection.
• Normal flora have fewer weapons than pathogenic bacteria.
• Pathogenicity typically correlates with weapon count.

Explore why urinary tract infections are more common in women. Learn about the types of bacteria commonly found in the normal flora of the vagina and its role in vaginal health.