This document summarizes several infections of the digestive system, genitourinary system, reproductive system, and eyes. It outlines the typical causative agents, symptoms, modes of transmission, diagnosis, and treatment for various conditions including peptic ulcers, cholera, salmonellosis, typhoid fever, shigellosis, traveler's diarrhea, Campylobacter infections, urinary tract infections, gonorrhea, syphilis, chlamydia, trachoma, and Acanthamoeba keratitis. The document provides an overview of the normal microbiota of the small intestine and colon and describes several common bacterial, viral and parasitic pathogens involved in infections of different parts of the digestive and

1. Infections of the digestive system
Overview
 Normal microbiota of small
intestine and colon
includes
 Bacteroides
 Lactobacillus
 Enterobacteriaceae
such as
 Escherichia coli
 Enterobacter
 Proteus
 Klebsiella
 Yeast
 Candida albicans
 Protozoa
 Entamoeba

2.  Caused by Helicobacter pylori
 It burrows through the mucous lining the
stomach
Peptic Ulcers
 Fecal-oral transmission
 Diagnosis: detection of ulcers in the stomach/H. pylori in clinical specimens
 Treatment: Antimicrobials and drugs that inhibit acid production

3. Cholera is caused by Vibrio cholerae
 Cholera toxin causes loss of fluid and
electrolytes, leading to dehydration,
acidosis, severe watery diarrhea
(“rice-water stool”)
 Associated with poor sanitation, contaminated water or raw,
undercooked food (seafood)
 Treatment: replacement of fluids/electrolytes, and antimicrobials
 Preventive measures: boiling water, eat cooked food, washing hands
Gram
negative
curved rod

4. Salmonellosis and typhoid fever
 Salmonella enterica
 Serotypes Enteritidis, and
Typhimurium cause salmonellosis
 Salmonella attack intestinal
cells, killing them
 Fever, abdominal cramps,
diarrhea (salmonellosis - often
from contaminated eggs)

5. Salmonellosis and typhoid fever
 Salmonellosis (self-limiting): fluid/electrolytes replacement
 Typhoid fever (poor countries): treated with antimicrobial drugs
 Salmonella typhi multiply within
phagocytic cells
 Typhoid fever: High fever,
headache, diarrhea (ulceration or
perforation of intestinal wall can
occur)
 Serotypes
Typhi, Paratyphi
cause typhoid fever
 Establish infection in
the gallbladder
 Asymptomatic
carriers release
Salmonella in the feces
causing contamination of
food/water

6. Shigellosis (Bacillary dysentery)
 Fever, abdominal cramps, diarrhea (can involve bloody stool)
 Shigella species colonize cells of the small intestine producing
enterotoxins that trigger diarrhea
 S. boydii
 S. dysenteriae
 S. flexneri
 S. sonnei
 S. dysenteriae secretes Shiga-toxin
 The Shiga-toxin stops protein synthesis

7. Shigellosis
 Shigella invades cells of the large
intestine
 Diagnosis
 Symptoms
 Presence of Shigella in the stool
 Treatment
 Supportive care and
antimicrobials
Rare bacteremia

8. Traveler’s diarrhea
 Escherichia coli strains - most
common cause of diarrhea in
travelers
 Produce enterotoxins
 E. coli O157:H7 - Shiga-like toxin kills cells, causes kidney failure,
and can lead to death – it can be found in ground meat
 Supportive care (fluids/electrolytes)
 Antidiarrheal drugs prolong symptoms delaying elimination
of the bacterium

9. Campylobacter jejuni is the leading cause of
gastrointestinal infections in US
 Campylobacter jejuni is a Gram
negative bacterium
 Causes diarrhea, bleeding
lesions, inflammation
 Major source - undercooked
contaminated poultry (chicken)
 Campylobacter is found in the
stool
 Supportive care
 Antibiotic treatment
 About 1 million people
have Campylobacter
diarrhea each year

10. Infections of the genitourinary system - Overview
 Distal tract of urethra is
colonized by some microbiota,
including Staphylococcus and
Streptococcus
 The rest of the
urinary organs and urine
are axenic
 Most common cause of urinary tract infections are enteric bacteria:
Escherichia coli, Proteus, Klebsiella;
 Pseudomonas and Enterococcus species are also involved

11.  Urinary tract infections (UTIs) are named according to the site of
infection
 Urethritis (urethra)
 Cystitis (bladder)
 Pyelonephritis (kidneys)
 Associated with frequent, urgent, or painful urination. This
condition is called dysuria
 Cloudy urine with a strong foul odor
 UTIs are more common in women (urethra is shorter and closer to
the anus)
Urinary tract infections

12. Bacterial infections of the reproductive system
Major infections of the reproductive system are sexually transmitted
(STDs)
 Most common pathogens
 Neisseria gonorrhoeae, Chlamydia trachomatis
 Papilloma virus, Herpes simplex type 2, HIV
 Haemophilus ducreyi, Treponema pallidum, Candida albicans,
Trichomonas vaginalis

13. Neisseria gonorrhoeae (gonococcus)
causes gonorrhea – bacterial STD
 In men - usually symptomatic
 It involves
 inflammation of the urethra
 painful urination
 purulent discharge

14. Neisseria gonorrhoeae (gonococcus)
causes gonorrhea – bacterial STD
 In women: (often
asymptomatic) infects the
cervix. Can cause Pelvic
Inflammatory Disease (PID)
 There is no long-term immunity
or vaccine against multiple
strains – antimicrobials are
used
 Abstinence, faithful mutual
monogamy, condoms properly
used!

15. The human pathogen Treponema pallidum
1. Primary syphilis
 Transmitted by sexual contact
Infectious lesion at the
site of infection called
chancre
Treponema enters the
bloodstream, contagious
widespread rash
2. Secondary syphilis
3. Latent (~10 years)
clinically inactive phase
of the disease
~ One third of patients
enter this phase
Painful, rubbery lesions,
dementia, blindness,
paralysis, heart failure
4. Tertiary syphilis

16. The human pathogen Treponema pallidum
 Remains active in sex
workers, gay people,
users of illegal drugs
 Spread from mother to
fetus (congenital
syphilis)
 Antimicrobial drug
(penicillin)
 More than 12 million new victims/year (WHO)
 Diagnosis of primary, secondary,
congenital syphilis is done detecting
antibodies against Treponema

17. Chlamydia trachomatis
 Chlamydia trachomatis is the most common sexually transmitted
bacterium – Gram negative intracellular bacterium
 Chlamydia strains can be
associated with
 Pelvic inflammatory disease
(PID)
 Trachoma (babies)
 Lymphogranuloma venereum
Transient genital lesions at the
site of infections followed by the
formation of a bubo

18. Infectious disease of the eye
 Chlamydia trachomatis - trachoma
 Neisseria gonorrhoeae - ophthalmia neonatorum
 Acanthamoeba keratitis
 Infections cause inflammation
of the
 conjunctiva (conjunctivitis)
 cornea (keratitis)

19. Trachoma is caused by Chlamydia trachomatis
Humans are the only reservoir
 Infects babies’ eyes as they pass through an infected vagina at birth
 Trachomatis strains infect and
kill cells of the conjunctiva
 Purulent discharge scars the
conjunctiva
 Eyelashes turn inward, scratch
and scar the cornea
 Scarred cornea is filled with blood vessels and is no longer transparent,
leading to blindness

20. Trachoma is caused by Chlamydia trachomatis
 Infections of the eyes of newborns are treated with antimicrobials
 Surgical correction of the eyelid abnormalities may prevent
scratching, scarring, and blindness
 Diagnosis involves
detecting Chlamydia
within cells from the
site of infection
 Antibiotics
(erythromycin or
sulfonamides) are
used to treat pregnant
women

21. Acanthamoeba keratitis
 Acanthamoeba is found in freshwater, tap water, soil
 Many cases have been associated with the wearing of contact
lenses, overnight or while swimming
 Inflammation and severe
pain
 Diagnosis
 Trophozoites and cysts
in stained scrapings of
the cornea
 Treatment
 Eye drops and topical
applications Damage may lead to corneal transplant