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Pharmacy Times - July 2005

Antibiotics, Probiotics, and Microflora

Ross Pelton, RPh, PhD, CCN

Approximately 300 million prescriptions for antibiotics are filled in the United States every year.1 Although antibiotics play a crucial role in the health care system, their widespread use is increasingly causing some serious health consequences. This article will explain the benefits of the beneficial or "good"bacteria that populate the gastrointestinal (GI) tract, and the multiple problems that can develop when the intestinal microflora is upset. It also will cover a simple yet critically important patient counseling opportunity for pharmacists with regard to antibiotics.

The human intestinal microflora contains >100 trillion living bacteria, comprising from 100 to 400 bacterial species.2 These organisms regulate important functions in the body, such as the digestion and absorption of nutrients, and aspects of the immune system.

A healthy human GI tract contains ~85% to 90% good bacteria. Everyone's GI tract harbors some "bad"bacteria and yeast organisms, but when they are present in small numbers (10%-15% of the GI population) they do not cause problems. When the balance between the good and bad bacteria is upset, however, dysbiosis can develop. Dysbiosis refers to the symptoms and problems resulting from an unbalanced or dysfunctional intestinal microflora.

The primary cause of dysbiosis is the use of antibiotics, which kill >99% of the good bacteria.3 Other factors that can cause or contribute to the development of dysbiosis include stress, birth control pills, and junk foods.

With dysbiosis, toxin-producing intestinal bacteria can cause a wide variety of symptoms. Digestive complaints are most common, including gas, bloating, intestinal pain and inflammation, and constipation and/or diarrhea. Unfortunately, the cause of these symptoms is frequently misunderstood and misdiagnosed.

The 2 most important species of beneficial bacteria are Lactobacillus acidophilus, which primarily colonizes the small intestine, and Bifidobacterium bifidum, which inhabits the large intestine. Lactobacillus bacteria produce lactic acid, which creates a slightly acidic pH in the upper GI tract. This environment is favorable for the beneficial bacteria, but it inhibits the growth of acidsensitive pathogenic bacteria.4 The lactobacilli have another important immune system-enhancing feature, which is their ability to produce a variety of natural antibiotics in the intestines, such as lactocidin, lactobicillin, lactobreven, and acidolin.5 L acidophilus bacteria also produce the enzyme lactase, which aids in the digestion of lactose, or milk sugar. Many lactose-intolerant people benefit by taking acidophilus with a meal containing milk or dairy products.

In the large intestine, bifidobacteria produce short-chain fatty acids (SCFAs), including acetic, propionic, butyric, lactic, and formic acids. The most plentiful SCFA produced by bifidobacteria is acetic acid, which exerts a wide range of antimicrobial activity against yeasts, molds, and bacteria.6 Healthy intestinal microflora actively produce organic acids and natural antibiotics, which are an important part of the immune system. Other studies suggest that the beneficial bacteria provide protection against cancer. Various strains of beneficial bacteria reportedly aid in the detoxification and elimination of carcinogens, modulation of procarcinogenic enzymes, and suppression of tumor growth rates.7,8

A study has revealed that beneficial bacteria in the GI tract also play an important role in whole-body immunity. Researchers initially measured the phagocytic index in 2 groups of participants. The phagocytic index is a measure of how effectively neutrophils and macrophages (types of white blood cells) attack and destroy bacteria, viruses, and other foreign invaders throughout the body. The pretest phagocytic index was 38.9% in group 1 and 46.3% in group 2. After supplementing with bificobacteria for 3 weeks, the phagocytic index in group 1 increased to 86.5%. After supplementing with L acidophilus for 3 weeks, the phagocytic index in group 2 increased to 84.4%. These results represent a dramatic increase in the strength of the immune system in these participants.9

The quality and potency of probiotic products varies greatly. After finishing the course of antibiotics, counsel your patients to take a probiotic twice daily for 2 weeks. Each dose should contain at least 1 to 2 billion live bacteria.

Dr. Pelton is director of education at Integrative Health Resources Inc.

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