Micro Lecture #14 notes p.342-361 Microorganisms and Human Health

Sudden inoculation at birth = O.K. (Mother's protective Ab=passive)

Neisseria gonorrhoeae (silver nitrate or antibiotics) blindness

Residents, transients, opportunists

T Toxoplasmosis O other R Rubella C Cytomegalovirus H herpes

CMV^- blood for neonates.

Symbiosis: Mutualism, commensalism, parasitism, neutralism, antagonism (know these already)

(nonspecific interior) (immune defenses) Future chapters

Nonspecific surface: structural, mechanical, biochemical (dryness[keratin]); acids of skin, stomach; lysozyme

Skin: Dry, tightly linked cells, acids, salts. P.aeruginosa can grow in hospital antiseptic wash solutions. Residents multiply, transients don't.

Conjunctiva: skin residents constantly into eye (flushed, lysozyme).

Nasopharyngeal: numerous inhabitants, but, mucocilliary defence. Cystic fibrosis= thick mucous, malfunctioning cilia, so, beat chest, antibiotics. Cigarettes paralyze cilia about 24 hours

Mouth: flora shifts toward anaerobes with teeth. Commensals to some(20%)= pathogens to others. Saliva not great growth medium. Strep sanguis, mutans major cariogenics. Tooth shape critical for fighting decay. Disclosing agents. Fluoridation, decalcification if microbes stick (dextran sucrase). Antibiotics help? Germ-free=cavity-free.

Stomach to lower small intestines; acid tolerant to neutral. Increasing numbers in lower intestines Large intestine: fermentation vat. Very dense flora dominated by anaerobes. E. coli minor inhabitant. 4 liters flatus per day? Not me!

Vagina: antibiotics promote overgrowth of yeasts. Yoghurt?

Bladder: Constant flushing O.K., but shorter female urethra problem.

Pasteur vs. Metchnikoff: text: "germ-free animals proved Pasteur wrong"(in belief normal flora are essential). Germ-free live longer, but intestines, immune systems not properly developed. Skin residents create organic acids, scavenge wastes, so exotics suppressed. Also stimulate proper development of large intestines.

Candida albicans: diaper rash, vaginitis, thrush (+HIV severe problems)

http://www.quinion.com/words/turnsofphrase/tp-pro2.htm

PROBIOTIC

This word has been around since the beginning of the nineties, but has only slowly started to appear outside technical contexts. It refers to the use of microorganisms in a positive way to benefit health. They are usually consumed in specially designed foods that are variously called nutraceuticals, functional foods or FoSHUs ("Foods for Specified Health Uses"). An example is the way some people ingest bacteria in live yoghurt to enhance their intestinal flora and so aid digestion. Such harmless bacteria colonies are also being introduced into various environments to take up available resources and prevent harmful ones multiplying, a technique known as competitive exclusion. For example, a recent proposal to maintain healthy teeth involves populating the mouth with harmless bacteria that prevent those which cause decay from gaining a hold. A similar technique has been used in fish farming to prevent bacteria that cause disease from attacking stocks. Probiotic is not entirely new, as it has appeared on occasion in the past as another word for prebiotic, but that sense seems to be obsolete.The value of "competitive exclusion" is becoming widely accepted, and [one] company is now marketing a product that farmers can use to ensure the development of a protective flora of microbes in their chickens' intestines ... Several so-called probiotics, consisting of individual strains of lactobacilli, are now available for this purpose.[Bernard Dixon, Power Unseen, 1994]Probiotics have been reported to enhance the digestion and absorption of protein, fat, calcium and phosphorus. They produce their own lactase and may help overcome lactose intolerance.[Pharmacy Post, May 1997]

For a longer article on this topic:

http://www.courses.ahc.umn.edu/pharmacy/6124/handouts/probiotics.pdf

At the beginning of the last century, the Russian immuno-logist Elie Metchnikoff argued that life-long intake of yoghurt containing lactic acid-producing microorganisms could ex-plain the differences in length of life between ethnic groups. The idea was that the bacteria in the fermented products competed with microorganisms that are injurious to health.1 Today it is known that the normal human microflora is important as a barrier against colonization by exogenous pathogenic microorganisms and potentially pathogenic bacteria already present in small numbers in the microflora.2 The normal microflora influence several biochemical, physiological and immunological features of the host, particularly the gastro-intestinal flora, which consists of the most dense and diverse collection of bacteria.3 Disturbances in the normal microflora can be caused by several things, one being the administration of antimicrobial agents.4 Probiotic microorganisms are thought to counteract disturbances and thereby reduce the risk of colonization by pathogenic bacteria.5 Studies on strains of microorganisms used in probiotic dietary supplements have demonstrated that several strains produce antimicrobial sub-stances such as organic acids, bacteriocins and peptides. In vitro and animal studies have further shown inhibitory effects of probiotic bacteria to be mediated by their interference with the adhesion of gastrointestinal pathogens or with toxins produced by the pathogenic microorganisms. Studies suggest that Lactobacillus strain GG and Saccharo-myces boulardii are the two most promising species in the prevention of diarrhoea. Lactobacillus GG has been effective in reducing the frequency and duration of rotavirus-induced diarrhoea in children. Recently, it was shown that in children admitted to hospital the risk of acquiring nosocomial diarrhoea was reduced from 33% to 7% in the group receiving prophylactic therapy with Lactobacillus GG.7 However, the same strain was used in the prevention of diarrhoea in under-nourished children with inconsistent results. Only for non-breast-

fed children in one of three age groups was the probiotic strain of any advantage.8 Lactobacillus GG has further been shown to have a preventive effect on antibiotic-associated diarrhoea (AAD) in children.