Chapters 25 and 26

Microbial Diseases of the Digestive System

Microbial Diseases of the Urinary and Reproductive Systems

Microbial Diseases of the Digestive System

• Diseases of the digestive system are the second most common illnesses in the United States.

• Diseases of the digestive system usually result from the ingestion of microorganisms or their toxins in food and water.

• The fecal–oral cycle of transmission can be broken by:

– Proper sewage disposal

– Disinfections of drinking water

– Proper food preparation and storage

The Digestive System

Figure 25.1

• >300 species in mouth

• Large numbers in large intestine, including:

– Bacteroides

– E. coli

– Enterobacter

– Klebsiella

– Lactobacillus

– Proteus

• Bacteria in the large intestine assist in degrading food and synthesizing vitamins.

• Up to 40% of fecal mass is microbial cells

Normal Microbiota

Dental Caries• Dental caries begin when tooth enamel and dentin are eroded and

the pulp is exposed to bacterial infection

• Streptococcus mutans, found in the mouth– adhere to teeth – uses sucrose

• form dextran from glucose - sticky dextran form dental plaque• lactic acid from fructose.

• Acid produced during carbohydrate fermentation destroys tooth enamel at the site of the plaque.

• Gram-positive rods and filamentous bacteria can penetrate into dentin and pulp.

• Caries are prevented by restricting the ingestion of sucrose and by the physical removal of plaque. Figure 25.4

Periodontal Disease• Caries of the cementum and gingivitis are caused by:

– Streptococci

– Actinomycetes

– Anaerobic gram-negative bacteria.

• Chronic gum disease (periodontitis) can cause bone destruction and tooth loss; – periodontitis is due to an inflammatory response to a variety of bacteria

growing on the gums.

• Prevotella intermedia • Acute necrotizing ulcerative gingivitis

Figure 25.5

1. A gastrointestinal infection is caused by the growth of a pathogen in the intestines.

• Incubation times range from 12 hours to 2 weeks.

• Symptoms of infection generally include a fever.

2. A bacterial intoxication results from the ingestion of preformed bacterial toxins.

• Symptoms appear 1–48 hours after ingestion of the toxin. Fever is not usually a symptom of intoxication.

• Infections and intoxications cause diarrhea, dysentery, or gastroenteritis.

• These conditions are usually treated with fluid and electrolyte replacement.

Bacterial Diseases of the Lower Digestive System

Staphylococcal Food Poisoning

Figure 25.6

Staphylococcus aureus enterotoxin

Shigellosis• Shigella spp.

– producing Shiga toxin – mucosal abscess

• Symptoms include – blood and mucus in stools, – abdominal cramps– fever.

• Infections by S. dysenteriae result in ulceration of the intestinal mucosa.

• Shigellosis is diagnosed by isolating and identifying the

bacteria from rectal swabs.

Figure 25.8

Salmonellosis• Food Poisoning

– Salmonella enterica serovars such as– S. enteritidis – S. enterica Typhimurium– Mortality (<1%) due to septic shock

caused by endotoxin– Cooking food will usually kill

Salmonella.– Laboratory diagnosis is based on

isolating and identifying Salmonella from feces and foods.

• Typhoid Fever– Salmonella enterica Typhi– Bacteria spread throughout body in

phagocytes– 1-3% recovered patients become carriers,

harboring Salmonella in their gallbladder

Figure 25.9

Cholera• Vibrio cholerae

– Gram negative comma shaped bacterium – Serotypes that produce cholera toxin– Toxin causes host cells to secrete Cl–, HCO–, and water

• Vibrio cholerae O:1 and O:139 produce an exotoxin that alters the membrane permeability of the intestinal mucosa

• vomiting • diarrhea • a loss of body fluids.

• The symptoms last for a few days. Untreated cholera has a 50% mortality rate.

• Fluid and electrolyte replacement provide effective treatment.• Ingestion of noncholera Vibrios can result in mild diarrhea. Usually from

contaminated crustaceans or mollusks

Figure 25.12

• Traveler’s diarrhea may be caused by enterotoxigenic or enteroinvasive strains of Escherichia coli. – The disease is usually self-limiting and does not require chemotherapy.– Enterohemorrhagic E. coli, such as E. coli O157:H7,

• Produces Shiga toxins cause – inflammation – bleeding of the colon, including – hemorrhagic colitis – affect the kidneys hemolytic uremic syndrome.

• Campylobacter is the second most common cause of diarrhea in the United States.

• Campylobacter is transmitted in cow’s milk.• Yersinia enterocolitica and Y. pseudotuberculosis

• Can reproduce at 4°C• Usually transmitted in meat and milk

• Clostridium perfringens • Grow in intestinal tract producing exotoxin

• Bacillus cereus • Ingestion of bacterial exotoxin produces mild symptoms

Gastroenteritis

Helicobacter Peptic ulcer disease• Helicobacter pylori

– Produces ammonia, which neutralizes stomach acid;

– The bacteria colonize the stomach mucosa and cause peptic ulcer disease.

• Bismuth and several antibiotics may be useful in treating peptic ulcer disease.

Figure 25.13

Viral Diseases of the Digestive System - Mumps• Mumps virus - The mumps virus is a paramyxovirus that

shares various epidemiological characteristics with other well-known viral pediatric diseases, such as measles and rubella.

• Enters through respiratory tract – contagious disease that is spread from person to person through

contact with respiratory secretions, such as saliva from an infected person

• Infects parotid glands

• Painful swelling of the salivary glands

• Prevented with MMR vaccine

Figure 25.14

Hepatitis

Table 25.1

Transmission Causative agent Chronic liver disease

Vaccine

Hepatitis A

subclinical

Fecal-oral Picornaviridae No Inactivated virus

Hepatitis B

Frequently serious

Parenteral, STD Hepadnaviridae Yes Recombinant

Hepatitis C

Usually mild

Parenteral Filoviridae Some Yes No

Hepatitis D Parenteral, HBV coinfection

Deltaviridae Yes HBV vaccine

Hepatitis E Fecal-oral Caliciviridae No No

•Inflammation of the liver

•Hepatitis may result from drug or chemical toxicity, EB virus, CMV, or the Hepatitis viruses

•Symptoms- abdominal pain or distention, fatigue, jaundice, loss of appetite, low-grade fever, nausea and vomiting, weight loss

Viral Gastroenteritis

• Rotavirus

– 3 million cases annually

– 1-2 day incubation, 1 week illness

• Norovirus

– 50% of U.S. adults have antibodies

– 1-2 day incubation. 1-3 day illness

• Treated with rehydration

Figure 25.17

Fungal Diseases of the Digestive System

• Mycotoxins are toxins produced by some fungi.

– affect the blood,

– nervous system

– kidneys or liver.

– Ergot Poisoning, or ergotism, is caused by the mycotoxin produced by Claviceps purpurea.

– Cereal grains are the crop most often contaminated with the Claviceps mycotoxin.

– Aflatoxin Poisoning or Aflatoxin is a mycotoxin produced by Aspergillus flavus.

– Peanuts are the crop most often contaminated with aflatoxin.

Protozoan Diseases of the Digestive System• Giardiasis -

– Giardia lamblia grows in the intestines of humans and wild animals and is transmitted in contaminated water.

– Symptoms of giardiasis are malaise, nausea, flatulence, weakness, and abdominal cramps that persist for weeks.

– Diagnosis is based on identification of the protozoa in the small intestine.

• Cryptosporidiosis – Crytosporidium hominis causes diarrhea; in immunosuppressed patients,

the disease is prolonged for months.

– The pathogen is transmitted in contaminated water.

– Diagnosis is based on the identification of oocysts in feces.

• Cyclospora Diarrheal -C. cayetanensis causes diarrhea; • It is transmitted in contaminated produce.

• Diagnosis is based on the identification of oocysts in feces.

Amoebic DysenteryEntamoeba histolyticaAmoeba feeds on RBCs and GI tract tissuesDiagnosis by observing trophozoites in fecesTreated with metronidazole

Learning objectives• Name the structures of the digestive system that contact food.• List examples of microbiota for each part of the gastrointestinal tract.• Describe the events that lead to dental caries and periodontal disease.• List the causative agents, suspect foods, signs and symptoms, and

treatments for staphylococcal food poisoning, shigellosis, salmonellosis, typhoid fever, cholera, gastroenteritis, and peptic ulcer disease.

• List the causative agents, modes of transmission, sites of infection, and symptoms for mumps.

• Differentiate between hepatitis A, hepatitis B, hepatitis C, hepatitis D, and hepatitis E.

• List the causative agents, mode of transmission, and symptoms of viral gastroenteritis.

• List the causes of ergot poisoning and aflatoxin poisoning.• List the causative agents, modes of transmission, symptoms, and

treatments for giardiasis, cryptosporidiosis, Cyclospora diarrheal infection, and amoebic dysentery.

Microbial Diseases of the Urinary and Reproductive Systems

• The urinary system regulates the chemical composition and volume of the blood and excretes nitrogenous waste and water.

• The flushing action of urine and the acidity of normal urine have some antimicrobial value

• The reproductive system produces gametes for reproduction and, in the female, supports the growing embryo.

• The urinary bladder and upper urinary tract are sterile under normal conditions.

• >1,000 bacteria/ml or 100 coliforms/ml of urine indicates infection

• Lactobacilli dominate the vaginal microbiota during the reproductive years.

• The male urethra is normally sterile.

Normal Microbiota

Microbial Diseases of the Urinary and Reproductive Systems

• Microbes usually enter the urinary system through the urethra• Opportunistic gram-negative bacteria from the intestines often

cause urinary tract infections.• Nosocomial infections following catheterization occur in the

urinary system. E. coli causes more than half of these infections.

• Treatment of urinary tract infections depends on the isolation and antibiotic sensitivity testing of the causative agents.

• Microbes usually enter the reproductive system through:– The vagina (females) or urethra (males)

Bacterial Diseases of the Urinary System

• Urethritis, cystitis, and ureteritis are terms describing inflammations of tissues of the lower urinary tract.

• Pyelonephritis inflammation of the kidney and its pelvis, caused by a bacterial infection – result from lower urinary tract infections or from systemic

bacterial infections.

• Inflammation of the urinary bladder, or cystitis, is common in females.

• Microorganisms at the opening of the urethra and along the length of the urethra, careless personal hygiene, and sexual intercourse contribute to the high incidence of cystitis in females.

• The most common etiologies are:– E. coli and Staphylococcus saprophyticus.

– May also be caused by• Proteus, Klebsiella, Enterococcus, Pseudomonas

• E. coli usually causes pyelonephritis• Antibiotic-sensitivity tests may be required before treatment

Cystitis

Leptospirosis

• Leptospira interrogans

• Reservoir: Dogs and rats

• Transmitted by skin/mucosal contact from urine-contaminated water

• Sometimes causes severe kidney or liver disease

• Diagnosis: Isolating bacteria or serological tests

Figure 26.4

• Prevented by condoms

• Treated with antibiotics

Sexually Transmitted Diseases (STDs )

Urethritis1. Gonorrhea

– Neisseria gonorrhoeae• Attaches to oral or urogenital mucosa by fimbriae

– Females may be asymptomatic;

– Males have painful urination and pus discharge

– Untreated may result in• Endocarditis

• Meningitis

• Arthritis

• Ophthalmia neonatorum

– Treatment with antibiotics

2. Nongonococcal Urethritis

– Chlamydia trachomatis• May be transmitted to newborn's eyes

• Painful urination and watery discharge

– Mycoplasma hominis

– Ureaplasma urealyticum

Lymphogranuloma Venereum (LGV)

• Primarily a disease of tropical and subtropical regions

• Cause by Chlamydia trachomatis

• The initial lesion appears on the genitals and heals without scarring.• The bacteria are spread in the lymph system and cause enlargement of

the lymph nodes, obstruction of lymph vessels, and swelling of the external genitals.

• The bacteria are isolated and identified from pus taken from infected lymph nodes.

• Treatment: doxycycline

• PID – extensive bacterial infection of the female pelvic organs- uterus, cervix, uterine tubes or ovaries

– N. gonorrhoeae

– C. trachomatis

– Can block uterine tubes

– Chronic abdominal pain

Pelvic Inflammatory Disease

• Treponema pallidum

• Invades mucosa or through skin breaks

• Direct diagnosis:

– Darkfield microscopic identification of bacteria

– Staining with fluorescent-labeled, monoclonal antibodies

• Indirect, serological diagnosis:

– VDRL, RPR, ELISA, FTA-ABS - tests for anti-treponemal antibodies

Figure 26.10

Syphilis

• Primary stage: chancre at site of infection

• Secondary: Skin and mucosal rashes

• Latent period: No symptoms

• Tertiary: Gummas on many organs

• Congenital: Neurological damage

• Primary & secondary stages treated with penicillin

Syphilis

• Gardnerella vaginalis– Diagnosis by clue cells

– Treatment: metronidazole

Figure 26.12

Bacterial Vaginitis

Viral Diseases of the Reproductive System

1. Genital Herpes - – Herpes simplex viruses (HSV-1 and HSV-2) cause genital herpes.

Suppression: acyclovir or valacyclovir

– Symptoms of the infection are painful urination, genital irritation, and fluid-filled vesicles.

– Neonatal herpes is contracted during fetal development or birth. It can result in neurological damage or infant fatalities.

• The virus might enter a latent stage in nerve cells. Vesicles reappear following trauma and hormonal changes.

2. Genital Warts -– Human papilloma viruses cause warts.

– Some human papillomaviruses that cause genital warts have been associated with cancer of the cervix or penis.

– Vaccination against HPV strains.

AIDS

• AIDS  is a sexually transmitted disease of the immune system

• It is the ultimate clinical consequence of infection with HIV.

• HIV is a retrovirus

• HIV is genetically variable and exists as different strains, which cause different rates of clinical disease progression

• Primarily infects vital organs of the human immune system such as CD4+ T cells (T helper cells), macrophages and dendritic cells.

• It directly and indirectly destroys CD4+ T cells.• HIV reduces the effectiveness of the immune system and leaves

individuals susceptible to opportunistic infections and tumors

• Candida albicans– Grows on mucosa of mouth, intestinal tract, genitourinary tract

– NGU in males

– Vulvovaginal candidiasis

– Diagnosis by microscopic identification and culture of yeast

• Treatment: clotrimazole or miconazole

Fungal Disease of the Reproductive Systems  - Candidiasis

• Trichomonas vaginalis– Found in semen or urine of males

carriers

– Vaginal infection causes irritation and profuse discharge

– Diagnosis by microscopic identification of protozoan

– Treatment: metronidazole

Figure 26.15

Protozoan Disease of the Reproductive System -Trichomoniasis

Learning objectives• List the antimicrobial features of the urinary system.• Identify the portals of entry for microbes into the reproductive system.• Describe the normal microbiota of the upper urinary tract, the male

urethra, and the female urethra and vagina.• Describe modes of transmission for urinary and reproductive system

infections.• List the microorganisms that cause cystitis, pyelonephritis, and

leptospirosis, and name the predisposing factors for these diseases.• List the causative agents, symptoms, methods of diagnosis, and

treatments for gonorrhea, NGU, PID, syphilis, LGV, and bacterial vaginosis.

• List reproductive system diseases that can cause congenital and neonatal infections, and explain how these infections can be prevented.

• Discuss the epidemiology of genital herpes and genital warts.• Discuss the epidemiology of candidiasis.• Discuss the epidemiology of trichomoniasis.