UTI Microbiology for MBBS 28

• The presentation covers the microbiology of urinary tract infections (UTIs).
• It includes learning objectives, an outline, hypothetical questions, and case studies.
• Dr. Patrick Orikiriza presented this on July 24th, 2023, for MBBS 28.

Learning Objectives

• Review clinical scenarios related to UTIs.
• Explain key clinical terms for identifying UTIs
• Identify common bacteria associated with UTIs.
• Associate clinical signs/symptoms with UTI conditions.
• Explain bacterial pathogenesis in causing UTIs.
• Describe sample collection procedures for UTI investigation.
• Describe laboratory diagnosis of UTI-causing bacteria.

Outline

• Covers case reviews and an introduction to UTI syndromes.
• Explores common UTI pathogens and sample collection methods for UTI analysis.
• Covers catheter-associated UTIs, and UTIs in pregnancy and children.

Hypothetical Questions

• A researcher finds gram-positive rods in urine samples of most female MBBS 28 students but not males, what could be the interpretation?
• A gram stain shows gram-negative rods in most urine samples from both male and female students
• A researcher finds 3% of pregnant mothers in the Kabyaza community have gram-positive cocci in chains

Case Review 1

• A 77-year-old surgical patient with delirium and elevated temperature (39.9°C) and low BP (90/60 mm Hg) developed a UTI.
• The patient had a mildly elevated peripheral WBC count and was living in a long-term care facility.
• Gram stain revealed gram-negative rods and few WBCs with 100,000 CFUs/ml of lactose-fermenting colonies.

Case Review 2

• A 23-year-old woman reports increased urinary frequency and dysuria; otherwise healthy and sexually active.
• She is afebrile with normal BP has mild suprapubic tenderness and no fever, chills, vaginal discharge, or flank pain.
• She uses spermicide-coated condoms for contraception and has no history of STDs.

Case Review 3

• A 43-year-old woman with diabetes complains of chills, nausea, and low back pain with increased urinary frequency and dysuria.
• She took TMP/SMX for two days but stopped due to nausea and vomiting. She is febrile to 101.2 and tachycardic to 100 with a BP of 100/60.
• Examinations show suprapubic tenderness and severe right flank and costovertebral tenderness.

Points to Consider

• There are different ways patients present with UTIs.
• The value of urinalysis and Gram stain for diagnosis.
• The common causative agents of UTIs.
• There are various methods for urine collection.

Normal Microbiota

• The urinary bladder and upper urinary tract is normally sterile.
• Women's flora is influenced by estrogen in reproductive years with Lactobacilli dominating.
• Men typically have sterile urethras.

• 1,000 bacteria/ml or 100 coliforms/ml of urine indicates infection.

Introduction to UTIs

• UTIs are bacterial infections affecting ~150 million people globally, though many go unreported.
• Management relies on symptoms and lab findings.
• Females are more affected than males, with 60% of women getting a UTI in their life.
• UTIs are common in pregnancy, transplant, and catheterized patients.
• Upper UTIs affect renal parenchyma (pyelonephritis) or ureters (ureteritis).
• Lower UTIs affect the urethra (urethritis), bladder (cystitis), or prostate (prostatitis).
• Uncomplicated UTIs occur in a "normal" urinary tract (simple cystitis of short duration).
• Complicated UTIs occur in a urinary tract with functional or structural abnormalities.

Prevalence of UTIs

• Women are more prone due to anatomical factors allowing easier bladder access for bacteria, poor hygiene, sexual intercourse, and contraceptive use.
• Hormonal changes like menopause and estrogen loss increase UTI prevalence in older women.
• UTIs in men are rare but usually severe and complicated.
• Uncircumcised men are more prone as a bacterial build-up in the extra fold of skin makes them vulnerable.
• Elderly men are at increased risk with kidney stones or prostate problems.
• Abnormalities in the urinary tract that interfere with urine flow increases risks.

Clinical Syndromes: Cystitis

• Involves inflammation of the bladder.
• Presents with dysuria, urinary frequency/urgency, and suprapubic pain.
• There is an absence of fever and flank pain.
• Acute cystitis may lead to pyuria and is commonly caused by gram-negative bacilli.
• More common in women due to anatomical design and the common risks come from sexual intercourse, history of UTI, and diaphragm use.

Clinical Syndromes: Pyelonephritis

• A complicated UTI that extends into the kidney.
• Untreated lower UTI can ascend into the kidney.
• Cardinal signs are fever (>38°c), chills, and flank pain.
• Other symptoms are possible, including nausea, vomiting, back pain, dysuria, and urinary frequency.
• It may lead to complications associated with bacteremia and kidney failure and pyuria is also common.

Clinical Syndromes: Cervicitis

• Involves inflammation of the cervix that may be acute or chronic, and is sexually transmitted bacterial infections.
• Symptoms of this issues are dysuria, urgency, vaginal discharge, and low back pain.

Clinical Syndromes: Urethritis

• It is an inflammation of the urethra that manifests as dysuria with a discharge, and it is sexually transmitted.
• Urethritis may also occur due to trauma, and allergic or chemical factors.

Clinical Syndromes: Bacteriuria

• Involves the presence of detectable bacteria in the urine
• Patients may be either symptomatic or asymptomatic.

Causes of UTIs

• 95% are due to bacterial infections particularly E. coli (79%).
• Other members of enterobacteriaceae (mostly Klebsiella spp, Proteus spp) are also involved.
• Others: Pseudomonas, Enterococcus & Staphylococcus
• Type of pathogen is determined by the host and the environment.
• Pseudomonas & Klebsiella are common in hospital care-associated infections.
• Increasing rates of resistance are being reported globally.

Transmission

• Bacteria mostly enter and cause UTI through the ascending route (via the urethra).
• Bacteria may also originate from gut commensals introduced sexually or via external objects and colonize perianal region with invasion of the urethra.
• A hematogenous route is less common and originates from bacteremia.

Bacterial Profile

• Relevant bacterium are Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, or Proteus vulgaris, Pseudomonas aeruginosa, Group B streptococcus, Enterococcus faecalis and Staphylococcus species.
• Lactobacillus is part of the normal flora and is generally ignored in asymptomatic non-pregnant women unless in high counts.

Escherichia Coli

• Are Gram-negative rods, facultative anaerobes, and capsulated.
• They are motile peritrichous flagella causing non-spore forming, lactose fermenting and binary fission.
• Oxidase and urease negative.

E. Coli Virulence Factors: Adhesion

• Bacterial adhesion to the urinary tract initiates infection.
• Uropathogenic E. coli (UPEC) has pili that mediate adhesion.
• Uses type 1 pili to attach to uroepithelium & stimulate mechanisms leading to apoptosis.
• Exfoliation of the uroepithelium occurs exposing underlying cells to further UPEC invasion.
• Bacteria can reside in these cells and cause recurrent infections.
• Other bacterial surface adhesins also recognize and attach to host molecules.
• Adhesins may trigger internalization of bacteria inside host cells which protects them from antibiotics.

E. Coli Virulence Factors: Entry into Urothelial Cells

• Organisms invade urothelial cells and replicate and are protected and can persist within epithelial cells.
• Internalization protects bacteria from host defenses and antibiotics and provides opportunities for recurrent infections.

E. Coli Virulence Factors: Biofilms

• Bacterial adhesion to cell surfaces contributes to formation and they adhere to biological/nonbiological surfaces like catheters and are resistant to antibiotics.
• Biofilms are extracellular, matrix-enclosed, microbial assemblies which provide a protective environment for the survival of bacteria.

Pathogenesis

• Virulence factors like pili/fimbriae allow bacteria to ascend into the bladder and kidney.
• Colonization is the 1st step and pathogens attach to uroepithelial cells via pili/fimbriae.
• Bacterial attachment causes recruitment of toll-like receptors (TLR), which recognizes pathogen-associated patterns.
• TLR binding triggers a cytokine response resulting is local inflammatory which generates exfoliation leading too further spread up the UTI.

Clinical Manifestation of E. Coli

• Most infections due to Uropathogenic E. coli (UPEC), which are part of the normal microbiota in the gut and can be introduced during defecation.
• UPEC mostly causes acute simple cystitis, causing dysuria, urinary frequency/urgency and suprapubic pain.
• Complicated UTI may result in polynephritis with cardinal symptoms: fever (>38°c), chills and flank pain with or without nausea, vomiting, back pain, dysuria, and urinary frequency.
• Shiga toxin-producing Escherichia coli (STEC): O157:H7 usually causes bloody diarrhea.
• Shiga toxins cause premature destruction of the red blood cells which damage small blood vessels in kidney causing failure.
• Signs of hemolytic uremic syndrome (HUS) caused by STEC includes decreased urination, lethargy, paleness and CNS damage.

Diagnosis of UTIs

• Via a urine microscopic examination: WBCs, RBCs and the presence of bacteria
• Rapid screening via the urine dipstick test: leukocyte esterase and Nitrate turning into nitrite.
• Urinalysis is indicated by Pyelonephritis, in children, in pregnant women and in PTs with structural abnormalities of the urinary tract
• Culture Media for diagnosis of UTIs includes CLED (Cystine Lactose Electrolyte Deficient) which ferments lactose and a normal Blood agar
• Lab diagnosis of HUS includes bloods tests testing for thrombocytopenia and microangiopathic hemolysis and abnormal urinalysis indicated with shiga toxins

Proetus Mirabilis Characteristics

• Gram negative rods, and motile.
• Facultative anaerobes with swarming motility and are non-capsulate, non-spore-forming.
• Grow on solid media forming swarming motility and it is commonly associated with CAUTIs.
• Non-lactose fermenter, Nitrite positive and produce Urease & H2S.

Transmission

• Largely distributed in soils and water are member of the Enterobacteriaceae.
• Migration accross solid mediums due to its swarming motility
• Mainly occur due to ascension from the gastrointestinal and it is linked to person-to-person contact especially in healthcare

Virulence Factors

• P. Mirabilis causes 90% of the proteus infections in humans and it produces over 4 types of fimbriae related to the colonzation of the urinary tract
• This is associated with differentiating cell known as swarm cells

Virulence Factors

• P. Mirabilis includes with hemolysin/flagella as well as IgA that are both protected by fimbriae as well as urease.
• P. Mirabilis produces Urease hydrolyzes, the end product is the creation of ammonia, it promotes precipitating in the urine

Clinical Manifestations and Diagnosis

• This can manifest in people with catheterization

Pseudomonas Aeruginosa: Characteristics

• Are Gram negative
• Are strict aerobes and can sustain with low nutriaes and disinfectants
• Only has a single polar flagellar for movement
• Are only encapsulated and produce different pigments that cause the infection to spread within the body
• The infection is a common in hospital mainly

Virulence Factors of Pseudomonas Aeruginosa:

• These include endotoxins that generate sepsis
• Exotoxins destroy tissues and and prevent protein synthesis
• It has a pyocyan pigment that damages cilia resulting in pneumonia
• It forms biofilms with amr
• And releases Type 3 that transfers toxins directly into the cells

Clinical Manifestations of Pseudomonas Aeruginosa

• The bacterium can cause cystitis and pyelonephritis

Klebsiella: Chararcteristics and Virulence

• Gram negative, non motiles.
• Normal flora within the mouth
• Antigen classification with LRTIs and compromised immune systems

Clinical Manifestations and Transmission with Klebsiella and Diagnosis

• High risks with hospitalized pt's
• Testing is conducted with gram stains and presence of bacterium

Staphylococcus: Characteristics and Clinical Manifestations and Virulence

• Are Gram-positive bacterium
• Negative catalyses
• Negative Nitrite test
• Are more prone to younger woman (16 y.o) and sexual transmitted related

Group B Streptococci

• Common in both genders as well as new borns
• New born infection is caused during the the birthing and Brest feeding processes

Sample Collection Method

• The ideal practice is Aspiration of the bladder however the practice isnt commonly used in practical application
• The test is best done with cleaning and processing the test at 4 degrees Celsius
• The sample should be conducted mid stream with sterile cleaners

Preventing UTIs

• Wiping front to back (if female)
• Sterilization of medical devices used during medical practices