Introduction

Have you ever wondered if free-living microorganisms could exist in and on us without causing disease? Yes, microorganisms live in and on us in different anatomical locations without causing disease. Collectively, these microorganisms make up the normal flora of human beings, including bacteria and other microorganisms.

Where do we find normal flora?

The normal flora is found on the skin, mouth, urinogenital, gastro-intestinal, conjunctiva of the eye, and respiratory systems.

Types of normal flora

• The resident flora consists of relatively fixed types of microorganisms regularly found in a given area at a given age; if disturbed, it promptly re-establishes itself. 

• The transient flora consists of non-pathogenic or potentially pathogenic microorganisms that inhabit the skin or mucous membranes for hours, days, or weeks.

Components of the normal flora at different anatomical positions.

The predominant resident microorganisms of the skin are aerobic and anaerobic diphtheroid bacilli and nonhemolytic aerobic and anaerobic staphylococci. Predominant organisms of the eye’s conjunctiva are Moraxella sp, Diphtheroid, Staphylococcus epidermidis and Non-haemolytic streptococci.The nasopharynx of the infant is sterile at birth, but in 2-3 days’ time, it acquires the flora carried by the mother and attendants. The flora of the nose harbours Diphtheroids, Staphylococcus, Streptococcus, Haemophilus, and Moraxella lacunata.

The mouth contains micrococci, gram-positive aerobic spore-bearing bacilli, coliforms, proteus and lactobacilli. The mouth of an infant is not sterile at birth. It generally contains the same types of organisms as found in the mother’s vaginal canal. The vaginal canal of the newly born child is sterile, and within 24 hours, it colonizes with micrococci and enterococci. In 2-3 days, time lactobacillus acidophilus appears. So, the flora keeps changing depending on the pH of the vagina. However, lactobacillus acidophilus remains in the vagina till menopause.

E.coli bacteria predominantly inhabit the colon.

Advantages of Normal flora

• • They prevent or suppress the entry of pathogens.
  • These synthesize vitamins, especially Vit. -K and several B Group vitamins.
  • The normal flora evokes the Antibodies production. These antibodies cross-react with pathogens having related or shared antigens, thus raising the host’s immune status against the invading pathogen.
  • Colonies produced by some organisms of normal flora have a harmful effect on the pathogens. 

Disadvantages of normal flora

• They become pathogenic when the immunity is lowered. 
• They may act as pathogens in different tissues other than their normal habitat e.g. normal flora of the intestine may cause urinary tract infection (UTI). 
• Normal flora may cause confusion in diagnosis due to their ubiquitous presence in the body and their resemblance to some pathogens.

CONCLUSION

We need to understand our normal flora to prevent all catastrophes that arise due to poor handling, which involves killing the normal flora or aiding their transfer into anatomical sites which are not normal to them. Failure to do so has a potential risk of aiding the pathogenic microbes to flourish and giving an opportunity for normal flora to become pathogenic respectively.