Transcript Lecture 24

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
Normal Microbiota
• >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
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
Bacterial Diseases of the Lower Digestive System
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.
Staphylococcal Food Poisoning
Staphylococcus aureus
enterotoxin
Figure 25.6
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
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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
Gastroenteritis
• 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
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– 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
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
•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
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
Table 25.1
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 Dysentery
Entamoeba histolytica
Amoeba feeds on RBCs and GI tract tissues
Diagnosis by observing trophozoites in feces
Treated with metronidazole
Learning objectives
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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.
Normal Microbiota
• 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.
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.
Cystitis
• 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
Leptospirosis
• Leptospira interrogans
• Reservoir: Dogs and rats
• Transmitted by skin/mucosal contact from urinecontaminated water
• Sometimes causes severe kidney or liver disease
• Diagnosis: Isolating bacteria or serological tests
Figure 26.4
Sexually Transmitted Diseases (STDs )
• Prevented by condoms
• Treated with antibiotics
Urethritis
1. 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
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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
Pelvic Inflammatory Disease
• 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
Syphilis
• 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
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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
Bacterial Vaginitis
• Gardnerella vaginalis
– Diagnosis by clue cells
– Treatment: metronidazole
Figure 26.12
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 fluidfilled 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
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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
Fungal Disease of the Reproductive Systems Candidiasis
• Candida albicans
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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
Protozoan Disease of the Reproductive System Trichomoniasis
• 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
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.