Bacterial Infections
Protecting Yourself From Common Pathogens

The fight against bacterial infection represents one of the high points of modern medicine. The development of antibiotics in the 1940s offered physicians a powerful tool against bacterial infections that has saved the lives of millions of people. However, because of the widespread and sometimes inappropiate use of antibiotics, strains of bacteria have begun to emerge that are antibiotic-resistant. These new, stronger bacteria pose a significant threat to general welfare and health—and a challenge to researchers.

Bacterial infections can be caused by a wide range of bacteria, resulting in mild to life-threatening illnesses (such as bacterial meningitis) that require immediate intervention. In the United States, bacterial infections are a leading cause of death in children and the elderly (Howard BJ et al 1994). Hospitalized patients and those with chronic diseases are at especially high risk of bacterial infection (Murray et al 1998). Common bacterial infections include pneumonia, ear infections, diarrhea, urinary tract infections, and skin disorders.

Under normal circumstances, people are protected from bacterial infection by a healthy immune system. Thus, maintaining the healthiest immune profile possible will help reduce the risk of bacterial infection. For more comprehensive information on the immune system and general nutritional strategies to support healthy immune function, please see Maintaining a Healthy Immune System. The present chapter will focus more specifically on bacteria and approaches to staving off bacterial illness.

Risk Factors for Bacterial Infection

Although every human being is exposed to innumerable bacteria, some of us are at higher risk of infection than others. Besides a weakened immune system, there are other risk factors for bacterial infection and illness.

Age. Individuals at either end of the age spectrum (neonates and the elderly) are at increased risk of bacterial infections (Chandra RK 1989; Chandra RK 1992a). Neonates are most susceptible to infections by pathogens such as Escherichia coli (Chandra RK 2002; Chandra RK 2004). People older than age 60 years are susceptible to lower respiratory tract infections caused by Streptococcus pneumoniae.

Nutritional status. The human body requires a balanced diet that provides nutrients, minerals, and vitamins for a functional and effective immune response (Chandra RK 2004). Immune function is impacted by factors including hormonal status, age, and nutritional status (Hedlund J 1995). Malnutrition results in a depressed immune system that raises the risk of infection.

Genetic predisposition. Scientists have long known that some people have a genetic predisposition to bacterial infection (Hill AV 2000). The Human Genome Project, which recently completed a map of the entire human genome, increased our ability to locate specific genes related to infectious disease susceptibility ( Bentley DR 2000). Ultimately, researchers hope to use genetic testing to identify people who are at increased risk of infectious diseases, then design drug therapies that target specific genetic defects that are expressed in conjunction with diseases (Cariou A et al 2002).

Forms of Bacterial Infection

Bacteria are associated with many illnesses and conditions. Some of the more common ones are listed below.

Respiratory Infections

Upper respiratory tract infections. Upper respiratory tract infections are a leading cause of time lost from work and school (Madoff LC et al 2004). Bacteria account for up to 25 percent of upper respiratory tract infections. Group A streptococci are responsible for 95 percent of the cases of strep throat in the United States (Goldmann O et al 2003; O'Brien KL et al 2002). Strep throat is most common in children and adolescents (aged 3 years to 18 years). Other pathogens include Haemophilus influenzae (Echave P et al 2003; Robinson KA et al 2001).

Otitis media. Middle ear infections are the most common bacterial infections in children in the United States. By the age of 3 years, two-thirds of American children have had at least one episode of otitis media, and the other third has had three or more episodes. S. pneumoniae is the most frequent cause (Leibovitz E et al 2004).

Lower respiratory tract infections. Common lower respiratory tract infections include acute, chronic, and health care–associated pneumonia and bronchitis (Garcia Ordonez MA et al 1999; Hedlund J 1995). S. pneumoniae is the most frequent cause of community-acquired lung infections and pneumonia. Lower respiratory tract infections can occur in both healthy and immunocompromised individuals.

Tuberculosis (TB). An estimated 15 million people in the United States are infected with Mycobacterium tuberculosis (Dai G et al 1998; Skamene E 1991). Of these, however, far fewer will actually develop clinically evident disease. Whether TB infection will progress to disease depends on a person's nutritional status. TB occurs disproportionately in poorer populations. Infection is more likely to occur in people aged 15 to 25 years, those older than age 60 years, people with HIV, or people who have been incarcerated for longer than 6 months ( Fleischmann RD et al 2002). In prisons in particular, overcrowding and the frequent movement of prisoners between cells is a factor in the spread of infection (Lobacheva T et al. 2005). It is important to note that the antibiotics used as first-line treatments in TB, such as Isoniazid, are known to cause deficiencies in vitamin B6 (NIH 2005).

Gastrointestinal Infection

Infectious diarrhea is a leading cause of morbidity and mortality worldwide (Marignani M et al 2004; Reinert P 1993). In the United States, 100 million people are affected by acute diarrhea every year. Most diarrhea is viral (not bacterial) in origin, but bacteria remain an important cause. Nearly half of patients with acute diarrhea must restrict activities, 10 percent consult physicians, 250,000 require hospitalization, and approximately 3000 die. Common bacterial pathogens that cause diarrhea include Campylobacter species, salmonella, shigella, and E. coli O157:H7.

Campylobacter jejuni. C. jejuni is the most common cause of bacterial diarrhea in the United States. The Centers for Disease Control and Prevention (CDC) estimates that more than 1 million Americans are affected yearly. Previously, most cases of bacterial diarrhea were caused by salmonella, but the increased use of antibiotics in poultry- and cattle-feed has been linked to the increasing incidence of drug-resistant C. jejuni (Butzler JP 2004; Moore JE et al 2005; Takkinen J et al 2003). Transmission is via exposure to contaminated food (especially chicken) and water, or contact with infected animals (especially cats and puppies) (Kasper DL et al 2004).

Salmonella. Salmonellosis is the second most frequent cause of bacterial disease in the United States. In 2002, more than 44,000 cases were reported to the CDC. Mild infections often are undiagnosed or unreported, so incidence may be 30 or more times greater than reported (Gold HS et al 2000). Infections with Salmonella species include diarrhea, fever, and abdominal cramps (Murray et al 1998). The elderly, infants, and people with impaired immune systems are at greater risk of severe disease. Transmission is via exposure to contaminated food (especially eggs) or water, or contact with infected animals (reptiles) (Conte JE Jr 2002; Howard BJ et al 1994).

Shigella. Shigella species infection causes a watery or bloody diarrhea with abdominal pain, fever, and malaise. An estimated 448,240 cases occur in the United States yearly. Groups at highest risk in the United States are children in child care centers, individuals in custodial institutions, and international travelers (Gold HS et al 2000; Madoff LC et al 2004).

Escherichia coli O157:H7. E. coli O157:H7 is associated with a severe diarrheal disease called hemolytic uremic syndrome. It has caused several nationally prominent outbreaks of food poisoning. An estimated 73,000 cases are reported in the United States annually (Conte JE Jr 2002). Transmission is through contaminated hamburger meat, apple cider, and fruits and vegetables (Madoff LC et al 2004).

Helicobacter pylori. H. pylori is the most common chronic infection in humans (Basso D et al 2004; Go MF 2002). Acute infection causes abdominal pain, weight loss, nausea, and vomiting. H. pylori is the major cause of gastritis and peptic ulcers in adults and children (Zambon CF et al 2002). H. pylori impairs absorption of nutrients, altering the balance of iron, vitamin B12, folic acid, alpha-tocopherol, vitamin C, and beta-carotene.

Skin Infection

Skin infections include impetigo, boils, carbuncles, cellulitis, and complications from burns (Gelfand JA 1984; Gold HS et al 2000). Common pathogens include Staphylococcus aureus, group A streptococci, and Pseudomonas aeruginosa (Baggett HC et al 2004; Toshkova K et al 2001; Wysocki AB 2002). Impetigo, a skin infection caused mostly by group A streptococci, can cause severe kidney inflammation, sometimes resulting in kidney failure.

Health Care–Associated Infection

Hospital-acquired and health care–related infections are an increasing threat to patient safety and health in the United States (Weinstein RA 1991; Weinstein RA 1998). In the United States, infections encountered in the hospital or a health care facility affect more than 2 million patients, cost $4.5 billion, and contribute to 88,000 deaths in hospitals annually (Malone DL et al 2002; Tasota FJ et al 1998).

Urinary tract infections are the most common, followed by pneumonias, skin and soft tissue infections, and invasive bloodstream infections. Surgical wound infections account for 20 percent to 30 percent of cases, but contribute to as many as 57 percent of extra hospital days and 42 percent of extra costs. Staphylococcus epidermidis, S. aureus, Enterococcus faecium, Enterococcus faecalis, E. coli, Enterobacter species, and P. aeruginosa are common pathogens in wound infections (Goldmann DA et al 1996; Weinstein RA 1991).

Conventional Treatment of Bacterial Infection: Antibiotics and Resistant Bacteria

Antibiotics are the mainstay of bacterial treatment (Archer GL et al 2004). The goal of these drugs is to kill invading bacteria without harming the host. Antibiotic effectiveness depends on mechanism of action, drug distribution, site of infection, immune status of the host, and resistance factors of bacteria (Archer GL et al 2004; Roden DM 2004).

Antibiotics work through several mechanisms. Some (such as vancomycin and penicillin) inhibit formation of bacterial cell walls. Erythromycin, tetracycline, and chloramphenicol interrupt protein synthesis. Still others inhibit bacterial metabolism (sulfa drugs) or interfere with DNA synthesis (ciprofloxacin, rifampin) and/or cell membrane permeability (polymyxin b) (Conte JE Jr 2002).

When antibiotics were discovered in the 1940s, they were incredibly effective in bacterial infection treatment. Over time, however, many antibiotics have lost effectiveness against common bacterial infections because of increasing drug resistance (Barie PS 1998; Domin MA 1998). Bacteria may be naturally resistant to different classes of antibiotics or may acquire resistance from other bacteria through exchange of resistant genes. Indiscriminate, inappropriate, and prolonged use of antibiotics have selected out the most antibiotic-resistant bacteria (Petrosillo N et al 2002; van der Waaij D et al 2000). Antibiotic-resistant strains have emerged in hospitals, long-term care facilities, and communities worldwide (Flaherty JP et al 1996; Jacobs MR 1999; Levin AS et al 2003).

For example, S. aureus is a common bacterial pathogen that causes pneumonia, skin and urinary tract infections, and blood and surgical site infections. Some strains that are resistant to all current antibiotics, including vancomycin, have emerged in the United States and Japan. Antibiotic-resistant organisms lead to increased hospitalizations, health costs, and mortality (Amsden GW 2004; Apfalter P 2003; Austin DJ et al 1999; Baggett HC et al 2004; Barie PS 1998; Bonten MJ et al 2001; Borer A et al 2002; Tasota FJ et al 1998).

Besides increased drug resistance, high-dose and prolonged antimicrobial therapy can eliminate helpful bacterial flora and predispose people to infection (Carson CF et al 2003; Guarner F et al 2003). A common adverse effect of antibiotics is diarrhea, which can lead to loss of essential vitamins and minerals, especially vitamin K, magnesium, and zinc (Briend A 1988; Brunser O 1977; Fontaine O 1996; Guerrant RL et al 2000). Other adverse effects of antibiotic therapy include vitamin deficiencies, seizures, allergic shock (in people who are allergic to antibiotics), autoimmune disease, decreased platelets, kidney injury, drug/drug interaction, and death (Roden DM 2004).

Nutritional Approaches to Bacterial Infection: A Healthy Immune System

Nutritional deficiencies can affect immune response and increase susceptibility to infection. In turn, infection further aggravates nutritional deficiencies by increasing metabolic demands, decreasing nutrient intake, or blocking absorption from the gut (Calder PC et al 2002; Scrimshaw NS et al 1997; Scrimshaw NS 2003). Nutritional and dietary supplements stimulate immune response and may result in fewer infections, particularly in the elderly and in malnourished, critically ill individuals (Chandra RK 1999).

Some dietary supplements have been shown to enhance immune function.

Phytonutrients. Phytonutrients are plant-derived, naturally occurring compounds thought to have curative, preventative, and nutritive value (Balentine DA et al 1999; Craig W et al 1999). The major immune-boosting components in fruits, vegetables, and herbs are flavonoids and carotenoids, which are antioxidants that protect cells from oxidative damage (Craig WJ 1999; Craig W et al 1999). Flavonoids have a number of powerful complementary and overlapping effects, including modulation of detoxification enzymes, stimulation of the immune system, reduction of platelet aggregation, modulation of cholesterol synthesis, reduction of blood pressure, and antioxidant and antibacterial effects (Craig W et al 1999; Lampe JW 1999). Carotenoids may boost the immune system to fight bacteria by increasing the number of white blood cells (Balentine DA et al 1999; Craig W et al 1999).

Alkylglycerols. Alkylglycerols are found in shark liver oil as well as cow, sheep, and human breast milk. They are thought to act as immune boosters against infectious diseases. They have no known adverse effects at relatively high dosages of 100 milligrams (mg) three times daily (Pugliese PT et al 1998). For more safety information on shark liver oil, especially for people with atherosclerosis, see the Safety Caveats section.

Fighting Bacteria

In addition to immune-boosting supplements, a number of nutrients have shown antibacterial activity, especially when it comes to inhibiting bacterial infection. While large-scale human studies have yet to be conducted on many antibacterial nutrients, the existing animal studies show considerable promise with these agents.

Bee propolis and honey. Before antibiotics, honey was used to treat bacterial wound infections ( Lusby PE et al 2002; Miorin PL et al 2003; Molan PC 2002). Bee propolis has antibacterial and anti-inflammatory properties. In vitro laboratory studies have shown activity against TB, H. pylori, skin ulcers, and colitis (Boyanova L et al 2003; Dobrowolski JW et al 1991; Grange JM et al 1990).

Bromelain. Bromelain (a digestive enzyme derived from the pineapple plant) has been used for centuries as a folk remedy for digestive problems and to promote wound healing. It has been proposed as a digestive aid and also has shown immunomodulatory properties (Engwerda CR et al 2001). In animal studies, bromelain has been effective against E. coli by disrupting the bacteria's ability to adhere to the mucosal lining in the digestive wall (Mynott TL et al 1996, 1997).

Cranberry juice. Cranberry juice can be an effective therapy for bacterial urinary tract infections, both to manage infection and to reduce recurrence (Fleet JC 1994; Kontiokari T et al 2001). Cranberry supplements are also available.

Oil of oregano. Oregano oil has been used for centuries in Far Eastern and Middle Eastern cultures to treat respiratory infections, chronic inflammation, urinary tract infections, dysentery, and jaundice. Laboratory studies in which the oil was applied directly to food-borne pathogens showed that oregano oil has strong antibacterial properties (Dadalioglu I et al 2004). Medicinal oregano grows wild in the mountainous areas of Greece and Turkey. It has a high mineral content that enhances its therapeutic benefits, including calcium, magnesium, zinc, iron, potassium, copper, boron, and manganese. This oil is considered safe for humans and may be used in conjunction with antibiotics to fight bacterial infection (Preuss HG et al 2005).

Thyme. Thyme, another essential herbal oil, has shown antibacterial properties. For example, thyme has been demonstrated to inhibit many strains of E. coli, including E. coli 0157:H7 (Marino M et al 1999). It has also been very effective in preventing the growth of listeria (Faleiro L et al 2005).

Ginger. The characteristic odor and flavor of ginger root come from a volatile oil composed of shogaol and gingerols. Gingerols have been investigated for analgesic, sedative, antipyretic, antibacterial, and gastrointestinal tract motility effects. They have been found to inhibit gram-positive and gram-negative bacteria (Chrubasik S et al 2005; Mascolo N et al 1989; Thongson C et al 2004).