WEEK 2: Microbiology of the urinary tract Flashcards
Urine is normally sterile- flushing of the urinary tract.
The anterior urethra inhabited by normal flora.
Outline them.
Staphylococcus epidermidis
Enterococcus faecalis
Alpha-hemolytic Streptococci
Lactobacillus spp.
State the examples of Enteric bacteria, contaminants from the skin, vulva or rectum.
E. coli
Proteus
Corynebacteria
The epidemiology of UTI
A urinary tract infection (UTI) is an infection in any part of the urinary system.
State the 4 main parts of the urinary system.
Most infections involve what part of the urinary system?
What is Urinary tract infection (UTI) defined as in terms of significant bacteriuria?
State signs and symptoms of UTI.
kidneys
ureters
bladder
urethra
Most infections involve the lower urinary tract — the bladder and the urethra.
Urinary tract infection (UTI) is defined as significant bacteriuria ( >105 organisms / ml) in the presence of a constellation of symptoms such as
dysuria (painful urination)
increased urinary frequency and urgency
suprapubic discomfort
costovertebral angle tenderness
Who is bacterial infection most common among?
Affect up to 150 million individuals annually.
Occur in two general settings:
Which are?
State the common causes of hospital acquired UTI and community acquired UTI.
Most common bacterial infection among young, sexually active women.
Affect up to 150 million individuals annually.
Occur in two general settings: community-acquired and hospital (nosocomially)-acquired, associated with catheterization.
Most common hospital-acquired infection- 35-40% of nosocomial infections
Total annual direct and indirect cost due to UTIs in the US alone is estimated to be greater than US$ 1.6 billion
Hospital-Acquired UTI (HAUTI) Bacteria:
*Escherichia coli (E. coli): E. coli is a common cause of UTIs and is frequently implicated in HAUTIs, especially those associated with catheter use.
Enterococcus spp.: Enterococcus bacteria, particularly Enterococcus faecalis and Enterococcus faecium, can cause HAUTIs, often in patients with urinary catheters.
Pseudomonas aeruginosa: This opportunistic pathogen is known to cause infections in hospitalized patients, including UTIs associated with catheterization.
Klebsiella pneumoniae: This bacterium is associated with healthcare settings and can cause UTIs, particularly in patients with compromised immune systems.
Proteus mirabilis: Proteus mirabilis is known for its role in catheter-associated UTIs and can form biofilms, contributing to the persistence of infections.
Escherichia coli (E. coli): E. coli is the most common cause of community-acquired UTIs, particularly in women. It is a normal part of the intestinal flora but can cause infection when introduced into the urinary tract.
Staphylococcus saprophyticus: This bacterium is a common cause of community-acquired UTIs, especially in young women. It is less common in healthcare settings.
Klebsiella pneumoniae: While more commonly associated with healthcare settings, Klebsiella pneumoniae can also be a cause of community-acquired UTIs.
Enterococcus faecalis: While more prevalent in healthcare-associated infections, Enterococcus faecalis can occasionally be implicated in community-acquired UTIs.
Proteus mirabilis: Proteus mirabilis is capable of causing both hospital-acquired and community-acquired UTIs.
Describe the trend of UTI’S and males and females and also according to age.
Epidemiology- Incidence and prevalence
Incidence
Females: 1,200 cases per 100,000 persons annually
Males: 30 cases per 100,000 persons annually
Gender
Most prevalent in sexually active women.
1 in 3 sexually active women develop a urinary tract infection before the age of 24 years.
Women over age 65, or any women without estrogen
Age
More common in boys up to 6 months of age- lack of circumcision, anatomical
and structural abnormalities
Between 1 and 65 years of age, UTI predominantly occurs in female patients -
anatomy of the female urethra
Over age 65, bacteriuria affects men and women roughly equally
Genetics
Patients who do not secrete A,B, H blood group antigens are three to four times more likely to have recurrent UTIs
State the risk factors of UTI’s according to age and gender.
Check slides
Describe the different routes of UTI.
1.Hematogenous Route:
o Infection of the renal parenchyma by blood-borne organisms
o Gram positive organism, Staphylococcus aureus, Salmonella, Mycobacterium tuberculosis
o Infections with Gram negative bacilli rarely occur by the hematogenous route
2.Ascending Route:
o Fecal flora colonize the vaginal introitus and displace the normal flora
(diphtheroid, lactobacilli, coagulase-negative staphylococci, and streptococcal species).
Describe the different Antibacterial Host Defenses in the Urinary tract.
Urine flow and micturition
Urine osmolality
pH
Organic acids
Urinary inhibitors of bacterial adherence:
Bladder mucopolysaccharides
Secretory immunoglobulin A (SIgA)
Inflammatory response (PMNs, and cytokines-IL, TNF,)
Prostatic secretions
Humoral and cell-mediated immunity
Describe the Bacterial Virulence factors.
Fimbrae / Pili
Capsular antigens ie.. K1, K5 - Protects bacterium from
phagocytic engulfment
Lipopolysaccharide - Endotoxin which is an integral part of
Gram-ve bacteria cell wall
Flagella - Allow bacteria to ascend from bladder & initiate kidney
infection
Alpha hemolysin (HlyA)
Secreted autotransporter toxin (SAT)
Cytotoxic necrotizing factor 1 (CNF1)
Iron chelating factors & siderophores
Secretion of urease
Biofilm formation
State the 3 main lower UTI diseases.
State the Upper UTI diseases.
Lower UTI: cystitis, urethritis, prostatitis
Upper UTI: pyelonephritis, intra-renal abscess, perinephric abscess (usually late complications of
pyelonephritis)
Define complicated and uncomplicated UTI.
Uncomplicated UTI – Infection in a structurally and neurologically normal urinary tract. Simple cystitis of short (1-5 day) duration.
Complicated UTI – Infection in a urinary tract with functional or structural abnormalities (ex. indwelling catheters and renal calculi). Cystitis of long duration or hemorrhagic cystitis.
Define urethritis.
Swelling and irritation (inflammation) of the urethral mucosa.
Common manifestation of sexually transmitted disease
Outline causes of urethritis.
Causes
Bacteria that cause Urinary tract infections (E. coli)
Sexually transmitted diseases (Chlamydia
trachomatis, N. gonorrhoea, Mycoplasma
genitalium, Ureaplasma urealyticum,
Trichomonas vaginalis)
Viruses - herpes simplex virus and cytomegalovirus.
Sensitivity to the chemicals used in
spermicides or contraceptive jellies,
creams, or foams
State Risks for urethritis.
Risks for urethritis
Females in the reproductive years
Males, ages 20 - 35
Having many sexual partners
High-risk sexual behaviour (such as anal sex without a condom)
History of sexually transmitted diseases
State the symptoms of urethritis in males.
In men
Burning pain while urinating (dysuria)
Discharge from penis
Frequent or urgent urination
Itching, tenderness, or swelling in penis or groin area
Pain with intercourse or ejaculation
Blood in the urine or semen
State the symptoms of urethritis in females.
Abdominal pain
Burning pain while urinating
Frequent or urgent urination
Pelvic pain
Vaginal discharge
Fever (rare
State the tests used for diagnosis of urethritis.
Tests
Urinalysis and urine cultures
Tests for gonorrhea, chlamydia, and other sexually transmitted illnesses
(STI
Describe the treatment plan for urethritis.
What is the goal?
Treatment
The goals of treatment are to:
Eliminate the cause of infection
Improve symptoms
Prevent the spread of infection
Antibiotics.
➢ Ceftriaxone / Azithromycin
➢ Doxycycline
➢ Metronidazole
Sexual partner must also be treated.
Urethritis caused by trauma or chemical irritants is treated by avoiding the source of injury or irritation.
Prognosis
➢With the correct diagnosis and treatment, urethritis usually clears up without any complications.
➢Can lead to permanent damage to the urethra (urethral stricture) and other urinary organs in both men and women
State the complications of urethritis in males and females.
Complications
Men
Bladder infection (cystitis)
Epididymitis
Infection in the testicles (orchitis)
Prostate infection (prostatitis)
Urethral stricture
Women with urethritis
Bladder infection (cystitis)
Cervicitis
Pelvic inflammatory disease
Define cystitis.
Cystitis is an inflammation of the mucous membrane of the bladder, caused by bacteria that enter the urethra and then the bladder.
The infection can spread to the kidneys.
State some differential diagnosis associated with cystitis.
Differential diagnosis
Vulvo vaginitis
Pelvic inflammatory disease
(In males: Cystitis rare, associated with stones ,prostatitis or chronic urinary retention. Urethritis, prostatitis)
State the risk factors for cystitis.
Procedures that involve the urinary tract, e.g.,: urinary catheter inserted in your bladder
Enlarged prostate, narrowed urethra, or anything that blocks the flow of urine.
Loss of bowel control (bowel incontinence)
Older age (especially in people who live in nursing homes)
Pregnancy, Diabetes
Problems fully emptying your bladder (urinary retention)
Staying still (immobile) for a long period of time
Most cases are caused by Escherichia coli (E. coli),
Most common cause of UTI
Caused by serogroups of E. coli such as :
➢ O (cell wall LPS) serotypes (e.g. O1, O2, O4,
O6, O7 and O75)
➢ K (capsular polysaccharide) serotypes (e.g.
K1, K2, K3, K5, K12 and K13).
Type 1 fimbrae : Promote attachment to
epithelial cells within urinary tract
P fimbrae: Encoded by pap (pyelonephritisassociated pili)
Strongest association with acute disease
~90% UPEC strains causing acute
pyelonephritis & ~20% strains causing
asymptomatic bacteriuria express P fimbriae
Gram Negative Rods
Motile
Capsules and fimbriae
Hemolytic on blood agar
Lactose fermenter
Indole positive
Citrate negative
Urease Negative
Catalase positive
Name the bacteria.
E.coli
Second most common cause of
cystitis in young women.
Sexual intercourse promotes
colonization and infection.
Alterations in the genital flora by
spermicides or candida infection
favor colonization by S.
saprophyticus.
Anal intercourse may play a role in
infection in homosexual men
Gram positive cocci
Coagulase negative
Non motile
Catalase positive
Lactose fermenter
Novobiocin resistant
Name the bacteria.
Staphylococcus saprophyticus
Hospital associated UTI
Develop plasmid mediated multi drug resistance.
▪ Capsulated Gram negative rods
Non motile
Large mucoid colonies
Lactose fermenting
Indole negative
Citrate positive
Urease positive
Catalase positive
Name the bacteria.
Klebsiella spp.
Proteus mirabilis most frequent cause of UTI
Secretion of urease :
➢ Hydrolysis of urea to ammonia & CO2 (pH >7, up
to 9)
➢ Alkaline urine- precipitates phosphate,
carbonate & magnesium
➢ Resulting in formation of Struvite stones &
eventually large Stag horn calculi (stones)
Gram negative rods
Motile-swarming growth
Lactose nonfermenters
Urease positive
Indole positive (P.mirabilis –
negative)
Citrate positive
H2S production in SIM
medium
Fishy/seminal odour
Name the bacteria.
Proteus
Nosocomial UTIs
Gram-negative rods with (polar) flagella
Not Enterobacteriaceae
Natural habitat – outside environment i.e. soil,
water, moist surfaces
Naturally resistant to many antibiotics - Due to ‘Rplasmid’
P. aeruginosa form biofilms on surface of urinary
catheters
Biofilms difficult to eradicate, resistant to
antimicrobial agents & host defense mechanisms
Often lead to persistent & recurrent infections.
Non lactose fermenting
Mucoid colonies
Musty ,earthy smell
Catalase positive
Oxidase positive
Citrate positive
H2S negative
Indole Negative
Pigment production-
-Pyocyanin and pyoverdin
Name the bacteria.
Pseudomonas aeruginosa
Discuss the treatment of cystitis and uncomplicated UTI.
Treatment:
Cystitis and uncomplicated UTI
Short course treatment- 3days
Amoxicillin
Nitrofurantoin
Fluoroquinolones-Ciprofloxacin
Cephalosporins
Trimethoprim-Sulfamethoxazole
Prophylactic therapy
Continuous
First choice Trimethoprim 100 mg at night
Second choices Nitrofurantoin 50 mg at night
Co-amoxiclav 250/125 mg at night
Define pyelonephritis.
Etiology?
Pyelonephritis - urinary tract infection (UTI) that affects one or both kidneys.
* Caused by a bacterium or virus infecting the kidneys
* Escherichia coli is often the cause.
* Bacteria and viruses can move to the kidneys from the bladder or can be carried through the bloodstream from other parts of the body.
State the risk factors for pyelonephritis.
Risk factors
* Structural, or anatomic, problem in the urinary tract
* Pregnant women and people with diabetes or a weakened immune system
State some complications of pyelonephritis.
Complications
Renal scarring
Hypertension
End stage Kidney disease
State some investigations done to diagnose pyelonephritis.
➢ Urinalysis and Urine culture
➢ Digital rectal examination (DRE). swollen prostate obstructing the neck of
the bladder.
➢ Ultrasound -who do not respond to treatment within 72 hours.
➢ Computerized tomography (CT) scan - obstructions in the urinary tract.
➢ Voiding cystourethrogram (VCUG) - abnormalities of the inside of the
urethra and bladder -used to detect VUR in children.
➢ Dimercaptosuccinic acid (DMSA) scintigraphy. show the severity of kidney
infection or kidney damage, such as scarring
Describe the treatment plan for pyelonephritis.
Pyelonephritis and complicated UTI (i.e. with associated
systemic toxicity)
First choices Co-amoxiclav 500/125mg 8-hourly x 10 days
Ciprofloxacin 500 mg 12-hourly
Second choices In seriously ill patients start i.v treatment, e.g.
Cefuroxime 750 mg 8-hourly 7-14 days
Gentamicin (Dose adjusted to renal function)
Most people with pyelonephritis do not have complications if
appropriately treated with antibiotics
SUMMARY
❖UTIs are among the commonest bacterial infections, especially
in women.
❖Usually endogenously acquired, with colonizing bacteria
ascending the urinary tract from the periurethral area.
❖E. coli is the predominant pathogen; other Gram-negative rods
are also responsible, especially in hospitalized patients.
❖Structural or mechanical factors in the host, or catheterization,
predispose to infection.
❖ Bacterial attributes such as adhesions and capsular
polysaccharides important in the development of UTI. Specific
toxins are not implicated.
Summary…
❖Asymptomatic infection is common in pregnancy,elderly and in
children. Infection is recurrent in a significant proportion .
❖ Pyelonephritis has a more severe presentation than lower UTI,
with fever and loin pain; recurrent infection results in renal
damage.
❖ Short-course treatment with oral antibacterials is effective for
lower UTI; pyelonephritis needs longer treatment, with
systemically administered drugs.
❖Hospital-acquired UTI is often caused by multiple-resistant
Gram-negative bacteria, and treatment should be based on
the results of antibiotic susceptibility tests
