NORMAL FLORA AND THE HUMAN BODY

 

INTESTINAL TRACT: At birth the intestine is sterile. In breast-fed children the intestine contains large number of lactic acid streptococci and lactobacilli. In bottle-fed children a mixed flora exists in the bowel and lactobacilli are less prominent. Diet has a marked influence on the composition of intestinal and faecal flora. Bowels of newborns in intensive care nurseries tend to be colonized with pathogenic organisms such as Klebsiella, Citrobacter and Enterobacter.

OESOPHAGUS AND THE STOMACH: In oesophagus and stomach the number of organisms is that swallowed with the food and it is temporary because the acidity of the stomach is protective. In conditions where there is decreased acidity of the stomach there are chances of increased number of organisms present in the stomach.

IN THE INTESTINES: The number of bacteria increases progressively beyond the duodenum to the colon, being comparatively low in the small intestine. In the upper intestine, lactobacilli and enterococci predominate, but in the lower ileum and caecum the flora is faecal. In normal adult colon the resident flora is predominantly anaerobic ranging between 96-99% consisting of Bacteroides, Fusobacterium, Anaerobic lactobacilli, Clostridium sp. and anaerobic streptococci.

Only about 4% are facultative aerobes consisting of gram-negative coliform bacteria, Enterococci, Lactobacilli, Proteus, Pseudomonas, Candida and others. More than 100 distinct types of organisms occur regularly in normal faecal flora. Prevalence of drug resistant organisms in the intestine serves as a source of plasmid-mediated drug resistance in the bacteria. Antimicrobial drug resistance

IN THE URETHRA: The anterior urethra of both sexes contains small numbers of the same types of organisms found on the skin and perineum. The organisms regularly appear in the normal voided urine. The commonly encountered organisms are Coagulase negative Staphylococci, Enterococci, Non-pathogenic neisseriae, Non-pathogenic mycobacteria, Various enteric gram-negative rods, Corynebacterium. In addition to the mentioned above, there is occasionary; Trichomonas vaginalis, Candida albicans, Staphylococcus aureus.

IN THE VAGINA: The usual microflora of the vagina from the menarche to the menopause is dominated by lactobacilli designated as Doderlien’s bacilli. The nature of the flora in the vagina depends on the pH of its secretions and it enzyme content. At birth the vagina is sterile. In the first 24 hours it is invaded by micrococci, enterococci and diphtheroids. With the appearance of glycogen the pH changes to acidic and the nature of the flora changes. The organisms normally encountered in the vagina are; Anaerobic streptococci, Beta haemolytic streptococci, Bacteroides, Gardnerella vaginalis, Ureaplasma urealyticum, Listeria monocytogenes, Staphylococcus aureus. Vaginal organisms present at the time of delivery may infect the newborn.

MOUTH AND UPPER RESPIRATORY TRACT: The flora of the nose consists of prominent corynebacteria, staphylococci (Staph. epidermidis and Staph. aureus) and streptococci. The mucous membrane of the mouth and pharynx are often sterile at birth but may be contaminated by passage through the birth canal. Within 4-12 hours after birth, viridans streptococci become established as the most prominent members of resident flora and remain so for life. Early in life, aerobic and anaerobic staphylococci, gram-negative diplococci, diphtheroids and occasional lactobacilli are added. When teeth begin to erupt anaerobic spirochaetes establish themselves along with anaerobic vibrios and lactobacilli. Actinomyces spp. are normally present in tonsillar tissue and various protozoa may also be present. Candida spp. can also be present in mouth. In the pharynx and trachea, a similar flora establishes itself. A few bacteria are found in normal bronchi. Small bronchi and alveoli are normally sterile. The predominant organisms in the upper respiratory tract, particularly the pharynx are non-haemolytic and alpha haemolytic streptococci and neisseriae.

RELATED;

1.  Enterobacteriaceae

2.  Streptococcus

3.  Bacteriology

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