Diversity Analysis of the Human Intestinal Flora: A Simple Method Based on Bacterial Morphotypes

Abstract

A preserved diversity is a distinctive feature of the health of any ecosystem. A reasonable estimation of the diversity of the human intestinal microflora can be easily obtained without the need of complicated methods of culture and speciation. From a study of 100 healthy human adults, 40 different bacterial morphotypes were recognised from colour prints obtained by microphotography of Gram-stained smears of faeces. On average each individual harbours 15.5 morphotypes (morphological diversity index, i.e. MDI = 15.5/40= 0.38). The number of morphotypes (or the MDI) increases in formula-fed newborns in contrast with breast-fed babies. In a semi-continuous culture system mimicking the microbial community of the human large intestine, the MDI sharply decreases when a broad spectrum antibiotic (imipenem) is added to the system. The results obtained in these two models of rise and fall of diversity as indicated by the MDI, suggests the potential usefulness of this simple approach for the study of bacterial diversity and stability in a variety of clinical circumstances in large human populations. Keywords: Diversity analysis; Bacterial morphotypes; Human intestinal flora.