Microbial Diseases of GI, Urinary & Reproductive Tract PDF

Microbial Diseases of GI, Urinary and Reproductive Tract  Structure and Function of the Digestive System The gastrointestinal (GI) tract, or alimentary canal, consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. In the GI tract, with mechanical and...

Microbial Diseases of GI, Urinary and Reproductive Tract  Structure and Function of the Digestive System The gastrointestinal (GI) tract, or alimentary canal, consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine. In the GI tract, with mechanical and chemical help from the accessory structures, large food molecules are broken down into smaller molecules that can be transported by blood or lymph to cells. Feces, the solids resulting from digestion, are eliminated through the anus.  Normal Microbiota of the Digestive System Each milliliter of saliva can contain millions of bacteria. In the stomach there are few microorganisms The large intestine has enormous microbial populations, mostly of anaerobes and facultative anaerobes. These bacteria assist in the enzymatic breakdown of foods, especially many polysaccharides that would otherwise be indigestible.  Bacterial Diseases of the Mouth Dental Caries Streptococcus mutans, found in the mouth, uses sucrose to form dextran from glucose and lactic acid from fructose. Bacteria adhere to teeth by the sticky dextran, forming dental plaque, type of biofilm. Acid produced during carbohydrate fermentation destroys tooth enamel at the site of the plaque.  Periodontal Disease Caries of the cementum and gingivitis are caused by streptococci, actinomycetes, and anaerobic gram-negative bacteria. Gingivitis – inflammation of gingivae, characterized by bleeding of the gums 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. Acute necrotizing ulcerative gingivitis, also termed Vincent’s disease is often caused by Prevotella intermedia. Vincent’s disease  Bacterial Diseases of the Lower Digestive System A bacterial intoxication results from ingesting preformed bacterial toxins. Incubation times range from 12 hours to 2 weeks. Symptoms of infection generally include a fever. Symptoms appear 1 to 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 Staphylococcal food poisoning is caused by the ingestion of an enterotoxin produced in improperly stored foods. S. aureus is inoculated into foods during preparation. The bacteria grow and produce enterotoxin in food stored at room temperature. Boiling for 30 minutes is not sufficient to denature the exotoxin. Foods with high osmotic pressure and those not cooked immediately before consumption are most often the source of staphylococcal enterotoxicosis. Laboratory identification of S. aureus isolated from foods is used to trace the source of contamination. Staphylococcal Food Poisoning  Shigellosis Shigellosis is caused by any of four species of Shigella. Most of the cases are caused by S. sonnei S. dysenteriae causes severe dysentery. Symptoms include blood and mucus in stools, abdominal cramps, and fever. Infections by S. dysenteriae result in ulceration of the intestinal mucosa. Virulent factor – Shiga toxin Small infectious dose is required to cause disease  Salmonellosis Salmonellosis, or Salmonella gastroenteritis, is caused by many Salmonella enterica serovars. Gram-negative, facultatively anaerobic rods Foodborne pathogen Symptoms include nausea, abdominal pain, and diarrhea and begin 12 to 36 hours after eating large numbers of Salmonella. Mortality is lower than 1%, and recovery can result in a carrier state Treatment - oral rehydration therapy Prevention - good sanitation practices  Cholera Vibrio cholerae O:1 and O:139 produce an exotoxin cholera toxin that alters the membrane permeability of the intestinal mucosa; the resulting vomiting and diarrhea cause loss of body fluids. The symptoms last for a few days. Untreated cholera has a 50% mortality rate. Treatment – Rehydration therapy Cholera may be treated with doxycycline. Noncholera Vibrios Ingestion of other V. cholerae serotypes can result in mild diarrhea. Vibrio gastroenteritis can be caused by V. parahaemolyticus. These diseases are contracted by eating contaminated crustaceans or contaminated mollusks.  Escherichia coli Gastroenteritis Several E. coli strains cause Gastroenteritis Enteropathogenic E. coli (EPEC) - major cause of diarrhea in developing countries and is potentially fatal in infants. Enteroinvasive E. coli (EIEC) - has the same pathogenic mechanisms as Shigella. This invasion results in inflammation, fever, and a Shigella-like dysentery. Enteroaggregative E. coli (EAEC) - produce an enterotoxin causing a watery diarrhea. Enterohemorrhagic E. Coli (EHEC), such as E. coli O157:H7, produces Shiga toxins that cause inflammation and bleeding of the colon, including hemorrhagic colitis and hemolytic uremic syndrome. Some E. coli strains that produce Shiga-like toxins are termed Shiga-toxin-producing E. coli (STEC). Unlike Shigella, these E. coli bacteria don’t invade the intestinal wall. Complication - hemolytic uremic syndrome (HUS). Characterized by blood in the urine, often leading to kidney failure. Enterotoxigenic E. coli (ETEC) secretes enterotoxins that cause diarrhea. The most common causes of traveler’s diarrhea are enterotoxigenic and enteroaggregative E. coli. Infections are spread by contaminated food or water. The infectious dose is estimated to be very small, probably fewer than 100 bacteria.  Campylobacteriosis Campylobacter are gram-negative, microaerophilic bacteria Campylobacter is the most common cause of diarrhea. Campylobacter is transmitted in chicken and unpasteurized milk. It is characterized by fever, cramping abdominal pain, and diarrhea or dysentery. Complication of campylobacterial infection is the neurological disease Guillain-Barré syndrome, a temporary paralysis. Infections may be treated with azithromycin Prevention - thoroughly cooking food products and pasteuring milk.  Helicobacter Peptic Ulcer Disease Helicobacter is a spiral-shaped, microaerophilic bacterium Helicobacter pylori produces ammonia, which neutralizes stomach acid; the bacteria colonize the stomach mucosa and cause peptic ulcer disease. This syndrome includes gastric and duodenal ulcers. H. pylori can grow in the highly acidic environment of the stomach Bismuth and several antibiotics may be useful in treating peptic ulcer disease. The most reliable diagnostic test requires a biopsy of tissue and culture of the organism. Urea breath test Tests of stools to detect antigens (not antibodies) for H. pylori Bacterial Diseases of the Lower Digestive System  Viral Diseases of the Digestive System Mumps Mumps virus causes inflammation of the parotid glands The parotids are one of the three pairs of salivary glands of the digestive system 16 to 18 days after virus exposure fever, and pain during swallowing. About 4 to 7 days later, orchitis may occur. After onset of the symptoms, the virus is found in the blood, saliva, and urine. A measles, mumps, rubella (MMR) vaccine is available.  Hepatitis Inflammation of the liver is called hepatitis. Symptoms include loss of appetite, malaise, fever, and jaundice. Viral causes of hepatitis include hepatitis viruses, Epstein-Barr virus (EBV), and cytomegalovirus (CMV). Hepatitis A virus (HAV) is transmitted via the fecal–oral route. Hepatitis B virus (HBV) is transmitted via blood and semen. Hepatitis C virus (HCV) is transmitted via blood. Hepatitis D virus (HDV) occurs as a superinfection or coinfection with hepatitis B virus. Hepatitis E virus (HEV) is spread by the fecal–oral route. Hepatitis  Fungal Diseases of the Digestive System Mycotoxins are toxins produced by some fungi. Mycotoxins affect the blood, nervous system, kidneys, or liver. Peanuts are the crop most often contaminated with aflatoxinproducing Aspergillus flavus.  Protozoan Diseases of the Digestive System Giardiasis Giardia intestinalis 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. Treatment with metronidazole  Amebic Dysentery (Amebiasis) Amebic dysentery is caused by Entamoeba histolytica growing in the large intestine. Spread mostly by food or water contaminated by cysts of the protozoan. The ameba feeds on red blood cells and GI tract tissues. Severe infections result in abscesses. Diagnosis identifying pathogen by several serological tests Metronidazole is the drug of choice in treatment  Structure and Function of the Urinary System The urinary system consists of two kidneys, two ureters, a single urinary bladder, and a single urethra. Urine is transported from the kidneys through ureters to the urinary bladder and is eliminated through the urethra. Valves prevent urine from flowing back to the urinary bladder and kidneys. The flushing action of urine and normal urine itself have some antimicrobial value. Normal Microbiota of the Urinary and Reproductive Systems  Bacterial Diseases of the Urinary System Cystitis Inflammation of the urinary bladder, or cystitis, is common in females. Symptoms often include dysuria (difficult, painful, urgent urination) and pyuria. The female urethra is less than 2 inches long, it’s closer than the male urethra to the anus and its contaminating intestinal bacteria. The most common etiologies are E. coli and Staphylococcus saprophyticus. Diagnosis – isolation and identification of bacteria Treatment with antibacterial drugs  Pyelonephritis Inflammation of the kidneys, or pyelonephritis, is usually a complication of lower urinary tract infections. Symptoms are fever and flank or back pain. About 75% of pyelonephritis cases are caused by E. coli. Pyelonephritis generally results in bacteremia Diagnosis - blood cultures and a Gram stain of the urine for bacteria Treatment –broad spectrum antibiotics such as a second- or third-generation cephalosporin.  Leptospirosis Leptospirosis is primarily a disease of domestic or wild animals, but it can be passed to humans and sometimes causes severe kidney or liver disease. The spirochete Leptospira interrogans is the cause of leptospirosis. The disease is transmitted to humans by contact with urine-contaminated water. Leptospirosis is characterized by chills, fever, headache, and muscle aches. An emerging form of leptospirosis, pulmonary hemorrhagic syndrome, with fatality rate of 50%. Diagnosed by a serological test Leptospira interrogans Doxycyline (tetracycline) is the recommended antibiotic for treatment.  Structure and Function of the Reproductive Systems The female reproductive system consists of two ovaries, two uterine tubes, the uterus, the cervix, the vagina, and the external genitals. The ovaries produce female sex hormones and ova (eggs). ovum is released during the process of ovulation, it enters a uterine tube, where fertilization may occur if viable sperm are present. The fertilized ovum (zygote) descends the tube and enters the uterus. It implants in the inner wall of the uterus and remains there while it develops into an embryo and, later, a fetus. The male reproductive system consists of two testes, ducts, accessory glands, and the penis; seminal fluid leaves the male body through the urethra.  Bacterial Diseases of the Reproductive Systems Gonorrhea Gram-negative diplococcus Neisseria gonorrhoeae causes gonorrhea. N. gonorrhoeae attaches to mucosal cells of the oral-pharyngeal area, genitals, eyes, and rectum by means of fimbriae. Symptoms in men are painful urination and pus discharge. Blockage of the urethra and sterility are complications of untreated cases. Women might be asymptomatic unless the infection spreads to the uterus and uterine tubes. Gonorrheal endocarditis, gonorrheal meningitis, and gonorrheal arthritis are complications that can affect both sexes if gonorrheal infections are untreated. Ophthalmia neonatorum is an eye infection acquired by infants during passage through the birth canal of an infected mother. Gonorrhea is diagnosed by ELISA or Nucleic acid amplification tests (NAATs). Treatment with antibiotics  Nongonococcal Urethritis Most cases of nongonococcal urethritis (NGU), or nonspecific urethritis (NSU), are caused by Chlamydia trachomatis. C. trachomatis infects the same columnar epithelial cells as the gonococcus. Symptoms include painful urination and a watery discharge. C. trachomatis can be transmitted to infants’ eyes at birth. Diagnosis is based on detection of chlamydial DNA in urine. Ureaplasma urealyticum and Mycoplasma genitalium also cause NGU.  Syphilis Syphilis is caused by Treponema pallidum, gram-negative spirochete. The organisms rapidly enter the bloodstream and invade deeper tissues. Primary Stage Syphilis - initial sign is a small, hard-based chancre, or sore. During this stage, bacteria enter the bloodstream and lymphatic system, which distribute them widely in the body. Secondary Stage Syphilis - oral sores and skin rashes visible on the palms, the loss of patches of hair, malaise, and mild fever. Tertiary stage, or late stage, affecting many tissues and organs. Congenital syphilis, resulting from T. pallidum crossing the placenta during the latent period, can cause neurological damage in the newborn. Stages of Syphilis Syphilis is transmitted by sexual contact Treatment with antibiotics  Bacterial Vaginosis Bacterial vaginosis is an infection caused by Gardnerella vaginalis. Decreases the number of vaginal Lactobacillus allows bacteria, G. vaginalis, to proliferate Diagnosis of G. vaginalis is based on the presence of clue cells. Treatment is primarily by metronidazole  Viral Diseases of the Reproductive Systems Genital Herpes Herpes simplex viruses (HSV-1 and HSV-2) cause genital herpes. Symptoms of the infection are painful urination, genital irritation, and fluid-filled vesicles. The virus might enter a latent stage in nerve cells. Vesicles reappear following trauma and hormonal changes. Neonatal herpes is contracted during fetal development or birth. It can result in neurological damage or infant fatalities. Diagnosis – culture of the virus from a vesicle, PCR There is no cure for genital herpes Treatment – antiviral drugs acyclovir, famciclovir and valacyclovir  Genital Warts Human papillomaviruses cause warts. Some human papillomaviruses that cause genital warts cause cancer. Disease is transmitted sexually Visible genital warts are most often caused by serotypes 6 and 11. Types 16 and 18 cause cervical cancer The available methods used for warts, such as surgery or cryotherapy, are not as effective against genital warts. Genital Warts  Fungal Disease of the Reproductive Systems Candidiasis Candida albicans causes nongonococcal urethritis in men and vulvovaginal candidiasis, or yeast infection, in women. Vulvovaginal candidiasis is characterized by lesions that produce itching and irritation. Predisposing factors are pregnancy, diabetes, and broad-spectrum antibacterial chemotherapy. Diagnosis is based on observation of the fungus and its isolation from lesions. Treatment - topical application of antifungal drugs such as clotrimazole and miconazole.  Protozoan Disease of the Reproductive Systems Trichomoniasis Anaerobic protozoan Trichomonas vaginalis causes trichomoniasis. The infection is often accompanied by a coinfection with gonorrhea. Symptoms include greenish yellow discharge with a foul odor, irritation and itching. Diagnosis is based on observation of the protozoa in purulent discharges from the site of infection. Treatment is by oral metronidazole References Gerard J. Tortora, Berdell R. Funke, Christine L. Case - Microbiology_ an introduction-Pearson (2018), Chapters 25 and 26