Diseases of the Gastrointestinal and Genitourinary Systems
CST: Clinical Significance
An open total abdominal hysterectomy (TAH) involves removing the entire uterus through an incision in the lower abdomen and pelvis.
The cervix is dissected, creating an opening between the pelvic floor and the vagina.
The peritoneal cavity is considered sterile, while the vagina is relatively contaminated due to its opening to the external environment.
Instruments used during closure of the pelvic floor are considered contaminated and should be isolated to prevent cross-contamination.
Even with preoperative antimicrobial prepping, resident microbiota remain in the vagina.
Isolating contaminated instruments reduces the risk of surgical site infection (SSI).
Gastrointestinal System
The GI system, also called the GI tract , is responsible for the digestion and absorption of nutrients, as well as the elimination of waste.
Transient microbes can be potential pathogens but are kept in check by the resident microflora.
Enzymes in the mouth, strong acids, and low pH in the stomach and duodenum also control microbial populations.
Digestion and elimination mediate the size of the normal population of resident GI bacteria.
Ingested substances like alcohol can kill resident microbes, while sugars can feed unfavorable bacteria.
Antibiotics can destroy resident microbial inhabitants.
Most intestinal flora are obligate anaerobes like Bacteroides and Fusobacterium species.
Facultative anaerobes like Escherichia, Enterobacter, Proteus, and Klebsiella species are less abundant but easier to isolate.
Diseases of the Gastrointestinal System
All GI bacteria can become pathogenic if they escape their normal environment or over-multiply.
Microorganisms attach to the intestinal epithelium to survive and multiply.
The large intestine contains the majority of bacteria due to slower peristalsis.
Oral disease involves bacteria proliferating on teeth surfaces (dental plaque), converting sugars into lactic acid, causing enamel erosion and decay (dental caries).
Streptococcus mutans is the bacterium that causes the most damage and creates stubborn polymicrobial biofilms.
Infection of the gums (gingivitis) is characterized by bleeding and soreness of the gums from an assortment of streptococci, actinomycetes, and anaerobic Gram-negative bacteria.
Untreated gingivitis progresses to chronic periodontitis.
Pus pockets form around teeth, destroying bone and tissues, caused primarily by Porphyromonas gingivalis.
Fusobacterium and spirochetes (Treponema) synergistically cause acute necrotizing ulcerative gingivitis (ANUG), also called “trench mouth” or Vincent’s angina/infection.
ANUG is a serious, non-contagious periodontal disease causing ulceration and necrosis of gum tissue.
Infected individuals may experience fever, bone and tissue destruction, and a foul odor due to tissue necrosis.
Tissue necrosis results from lactic acid and endotoxin production due to poor oral hygiene, influenced by overcrowded living conditions and malnutrition.
Gastric ulcer disease was once believed to be caused by spicy foods, hectic lifestyles, and stress until the discovery of Helicobacter pylori (H. pylori).
H. pylori produces urease, which neutralizes gastric acidity, converting gastric urea to ammonium ions.
Flagella help H. pylori pass from the acidic gastric lumen into the stomach mucus.
The body’s immune system cannot attack H. pylori within the mucous lining.
H. pylori infection progresses in the following order:
Chronic gastritis
Atrophic gastritis
Intestinal metaplasia
Dysplasia
Gastric adenocarcinoma
H. pylori is transmitted by the oral–oral or fecal–oral routes through contaminated water or food or from unwashed hands.
Treatments have shifted from H2 acid blockers to effective antibiotics.
Campylobacteriosis is a GI disease caused by Campylobacter bacteria, with Campylobacter jejuni being the primary cause of diarrheal disease in humans.
Campylobacteriosis is a zoonotic disease transmitted to humans by animals or animal products, mainly through the ingestion of raw or undercooked meats, unpasteurized milk, or contaminated water.
It is rarely fatal, except in infants, older adults, or immunocompromised persons.
Proper cooking or pasteurization is the only effective method of eliminating Campylobacter from contaminated foods.
Clostridioides difficile (formerly Clostridium difficile) is considered one of the most common healthcare-associated infections (HAIs).
HAIs are seen mainly in individuals who have had antibiotic therapy for other infections or those treated in healthcare settings.
Community-acquired C. difficile infections have developed as well.
In 2017, there were an estimated 224,000 infections, resulting in 12,800 deaths and in excess medical costs in the United States.
Escherichia coli is often identified as the agent of urinary tract infections, sepsis, diarrheal disease, and neonatal meningitis. The five types of pathogenic strains are:
Enteropathogenic (EPEC): Affects infants and is responsible for diarrheal disease outbreaks in nurseries.
Enterotoxigenic (ETEC): Referred to as “traveler’s diarrhea”, bacterial cells adhere to the epithelial cells of the small bowel and produce one or two exotoxins responsible for the diarrheal symptoms.
Enterohemorrhagic (EHEC): Severe form of bloody diarrhea known as hemorrhagic colitis, listed biologically as E. coli O157:H7.
EHEC causes disease by producing a toxin called Shiga toxin or Shiga toxin–producing E. coli (STEC), also called verocytotoxic E. coli (VTEC).
STEC disease includes bloody diarrhea and hemolytic uremic syndrome (HUS).
Enteroaggregative (EAEC): A recognized cause of diarrhea in children in developing and industrialized countries, associated with persistent diarrhea (14 days or more), a major cause of illness and death.
Enteroinvasive (EIEC): Causes a type of dysentery similar to shigellosis, but is not as virulent; it invades epithelial cells of intestinal mucosa and produces mild infection.
The most common method of identifying E. coli is detecting bacterial cells in the stool of the patient.
Sudden diarrhea with bloody stools should immediately be tested for E. coli O157:H7.
Treatment of E. coli diseases includes replacement fluids in cases of dehydration and appropriate antibiotic therapy if indicated.
Shigellosis, also known as bacillary dysentery, is an acute bacterial infection that affects the lining of the small and large intestines, characterized by bloody diarrhea with mucus and pus, nausea and vomiting, fever, and convulsions.
It is caused by serotypes of Shigella dysenteriae, Shigella flexneri, Shigella boydii, and Shigella soneii.
Another virulence factor is the number of individual organisms required for causing detectable signs and symptoms of infection.
S. dysenteriae requires only 10 bacteria to cause disease.
The infectivity dose (ID) is extremely low in comparison to the 100 to 200 organisms of S. flexneri or S. sonnei required to cause disease.
The genus Salmonella is the most common cause of enterocolitis due to the ingestion of contaminated foods.
Salmonella bacterium is a Gram-negative facultative anaerobe that lives in the intestines of humans and other animals.
Salmonella bacteria are the cause of 1.35 million infections annually, and most infections are food-borne.
A serious disease caused by Clostridium botulinum has four categories:
infant
wound
iatrogenic
food-borne
The toxin, a deadly bacterial toxin, may be released in the GI system after ingestion of food-borne bacteria; once ingested, toxins enter the bloodstream, where they act to block neurotransmission of peripheral nerve synapses.
Flaccid paralysis results and leads to muscle weakness and respiratory failure, but timely intubation and respiratory support have reduced mortality significantly.
Yersiniosis is a GI infection manifested by severe diarrhea with necrosis of the Peyer’s patches, liver and splenic abscesses, and chronic lymphadenopathy.
The causative bacterium, Yersinia enterocolitica, has been isolated from wounds, feces, mesenteric lymph nodes, and sputum of infected patients.
Yersinia pseudotuberculosis is a pathogen of rodents and birds, but can also infect humans; it is easily distinguished from the other Yersinia species because of its motility.
It causes fever and acute abdominal pain in the right lower quadrant due to mesenteric lymphadenitis that can also be mistaken for appendicitis, leading to incidental appendectomy or misdiagnosed as Crohn’s disease.
Y. pseudotuberculosis can cause severe enterocolitis, producing large nodules in the Peyer’s patches and intestinal abscesses; it may require intestinal resection, if it causes permanent damage.
Secondary manifestations of Y. pseudotuberculosis infections include erythema nodosum and reactive arthritis.
Post-infection complications include reactive arthritis (2–3%) and bacteremia (rare). Arthritis may occur in the absence of symptoms.
Yersinia enterocolitica is a pleomorphic, Gram-negative bacillus in the genus Yersinia and family Enterobacteriaceae.
In some countries, Y. enterocolitica has become a more prominent pathogen in cases of bacterial gastroenteritis over Shigella and is almost as prevalent as Salmonella and Campylobacter.
A known pathogen in pigs, cattle, sheep, horses, dogs, cats, rabbits, and rodents, the infection of the small bowel can cause superficial necrosis of the mucosa with ulceration.
The infected animal recovers and becomes a healthy carrier for life, potentially contaminating water supplies, and milk or meat consumed from infected animals.
Bacteria grow even in refrigerator-range temperatures and are more prevalent in countries of cooler climates, such as Scandinavia, northern Europe, and Japan.
Vibriosis is a GI infection caused by species of genus Vibrio, most commonly V. parahaemolyticus; most cases are brief (3 days) and do not require antibiotic therapy.
A more widely known disease and serious public health threat is cholera, caused by Vibrio cholerae.
Infections from the classical O1 strain of V. cholerae are rare and seen mainly in Bangladesh and parts of India.
The route of transmission is the fecal–oral route through ingestion of cholera-contaminated water in areas with insufficient or compromised water sanitation facilities.
The bacteria are shed in feces of infected individuals, then released back into the environment and spread through the water supply.
The signs are indicative of severe dehydration, and the most critical treatment is rehydration with either large amounts of liquids taken orally or intravenous fluids with electrolytes in more severe cases.
Infection from Bacteroides typically occurs when trauma to the GI tract permits the bacteria to escape from the wound and contaminate surrounding tissues.
The infection is a polymicrobial process that involves synergism and is from GI surgery, perforated appendix or intestinal ulcer, blunt and sharp trauma, diverticulitis, and inflammatory bowel disease (IBD).
After the intestinal wall is compromised, normal microflora spill into peritoneal cavity.
A potentially fatal GI infection in neonates is necrotizing enterocolitis (NEC), in which intestinal and intraperitoneal organs become ischemic from a drop in blood flow for unknown reasons, and bacteria likely exacerbate tissue damage due to an undeveloped immune system capability to fight off the bacterial proliferation.
Untreated, abscess will grow and rupture, releasing infectious material and causing peritonitis that can lead to septic shock and death.
S. aureus produces enterotoxins that, when ingested from contaminated foods, cause acute episodes of food poisoning.
Many foods can be contaminated by S. aureus and include meats and poultry, prepared deli meats, salads prepared with mayonnaise, milk and other dairy products, and egg products, including custard and cream-filled pastries.
Food can also be contaminated by the skin of preparers who fail to keep hands clean with proper hand hygiene.
Hepatitis Infections involve the liver and are caused by various viruses such as Hepatitis A (HAV), Hepatitis B (HBV), Hepatitis C (HCV), Hepatitis D (HDV), and Hepatitis E (HEV).
Chronic infections may go undiagnosed for years until signs of serious liver damage, such as cirrhosis or liver cancer, develop.
Treatment for the most severe cases of hepatitis is usually liver transplantation.
Genus Lactobacillus has several species, and most are part of the normal resident microbiome of the gastrointestinal and female genitourinary systems.
Other than L. delbrueckii, which is a cause of some urinary tract infections, most species of Lactobacillus are considered “friendly” bacteria.
The intestinal tract can be home to many species of protozoa and worms, mainly acquired through the fecal–oral route.
Worm larvae require time to incubate outside of the host and are then ingested through contaminated food, and some worm larvae can penetrate directly through the skin and make their way to the intestinal tract through various routes.
Protozoan pathogens include Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum; the diseases they cause are characterized by cysts and trophozoites (the active, motile feeding stage of a sporozoan parasite) in the feces.
Infections can be chronic or acute and life-threatening if the parasites make their way to other parts of the body, such as the brain, lungs, or liver.
Diseases of the Genitourinary System
The anatomy of the genitourinary (GU) system predisposes it to potential infection from opportunistic resident microbes of the skin or GI tract and through mechanical means, such as invasive surgical procedures or during sexual relations.
Infections of the GU system include the following types:
Parasites
Fungi
Bacteria
Viruses
Trichomoniasis is a sexually transmitted disease (STD) caused by the protozoan parasite Trichomonas vaginalis.
When symptoms are present, they typically include itching, burning, discharge, or redness of genitalia.
Pregnant females with this STD are at risk for pre-term labor.
Treatment with a single dose of oral anti-infective medication (metronidazole or tinidazole) is prescribed.
Individuals can become reinfected if all sexual partners are not treated.
Vulvovaginal candidiasis (VVC) is commonly known as a “yeast infection” and is caused by Candida albicans, a member of the vaginal microbiome.
Occurs when the normal balance of acidity or hormone levels in the vagina is altered.
Symptoms include itching, burning, odor, and “cottage cheese–like” discharge.
Treatment consists of oral or vaginal suppository anti- fungal medications.
Cryptococcus neoformans can also become a source of GU infection in immunocompromised individuals.
Many bacteria, whether resident or transient, can become the source of opportunistic GU infections.
Chlamydia trachomatis is transmitted through vaginal, anal, and oral sex, often with no symptoms for males or females.
When there are symptoms, they include itching, burning, painful urination, and possible vaginal discharge and minor bleeding.
Major risk of undiagnosed Chlamydia is pelvic inflammatory disease (PID) or non-viable ectopic pregnancy due to blockage of fallopian tubes.
E. coli is the common cause of urinary tract infections (UTIs) in infants who wear diapers, individuals with indwelling urinary catheters, and females in general.
Responsible for more than 80% of community-acquired UTIs and most HAI UTIs.
Gardnerella vaginalis is a pleomorphic, non-motile, facultative anaerobic bacterium that does not possess a capsule and cannot form spores, and whose shape resembles a Gram-negative bacillus, but the cell wall structure resembles Gram-positive organisms, adhering to the surfaces of epithelial cells in the vagina and vaginal fluids.
Haemophilus ducreyi is the causative agent of chancroid infections that are STDs characterized by painful, open, draining sores on genitalia.
Neisseria gonorrhoeae is the bacterium responsible for gonorrhea, a serious STD in both males and females.
Treponema pallidum are spirochetes responsible for venereal syphilis, and are characterized by phases of disease progression.
Viruses that primarily affect the GU system include herpes simplex virus 2 (HSV-2) and human papillomavirus (HPV).
HSV-2 is associated with lesions of the genitals and anus.
Herpetic lesions begin as fluid-filled blisters that rupture and cause pain until resolved in approximately 1 week.
Human papillomavirus (HPV) is the most common sexually transmitted infection, and according to the CDC, nearly all sexually active males and females will become infected with HPV at some time during their lives.
Condyloma is more commonly known as genital warts; a sexually transmitted infection caused by human papilloma virus (HPV) and found in the perineal region.
Types of Urinary Tract Infections
Urinary tract infections (UTIs) occur frequently in the humans but affect females more than males, partly due to the length of the female urethra and its proximity to the anus.
Gram-negative Escherichia coli is the most common pathogen that causes ascending UTI (ascending from the urethra to the bladder to the kidney).
HAI UTIs are often caused by Klebsiella, Enterobacter, Serratia spp., and Pseudomonas aeruginosa because these microbes tend to be antibiotic resistant.
UTIs are diagnosed as either upper or lower UTIs, depending on the structure or organ affected.
Upper UTIs include ureteral infections (ureteritis) or kidney infections (pyelonephritis).
Lower UTIs include urethral infections (urethritis) or bladder infections (cystitis).
Acute lower UTIs can cause dysuria (pain when passing urine), urgency (an urgent need to pass urine), increased frequency, and urine may be cloudy from pus present.
Upper UTIs can only be distinguished from lower UTIs by examining urine from the ureter through catheterization.
Pyelonephritis patients become febrile and show lower UTI signs and symptoms.
These types of recurrent infections can damage the kidneys, resulting in renal failure or hypertension.
Complicated and uncomplicated urinary tract infections – UTIs are also divided into complicated or uncomplicated infections.
A complicated UTI is one in which a patient has trouble with normal urination because of mechanical or neurological problems related to the infection (usually pyelonephritis).
Cystitis- most bladder infections (called cystitis) are from bacteria entering the urethra and occur more frequently in females.
Pyelonephritis- kidney infections can result from cystitis, especially in females.
Bacteria (usually E. coli) travel up the ureter from the bladder, infect the kidney, and subsequently cross into the bloodstream, causing septicemia.