Contributors of Campbell-Walsh-Wein, 12th edition

Kimberly L Cooper, Gina M. Badalato, Matthew P. Rutman, Kristy Mckiernan Borawski, Alicia H. Chang, Brian G. Blackburn, Michael Hsieh, Robert M Moldwin, Phillip M. Hanno, Michael Pontari, Richard Edward Link, and Nikki Tang

Urinary tract infections

An uncomplicated urinary tract infection (UTI) is an infection in a healthy patient with a structurally and functionally normal urinary tract. Most of these infections resolve with a short course of oral therapy. A complicated UTI is associated with factors that increase the chance of acquiring bacteria and decrease the efficacy of therapy ( Box 12.1 ). Here, the urinary tract is structurally or functionally abnormal, the host is compromised, and the bacteria have increased virulence or antimicrobial resistance.

Escherichia coli is the most common pathogen , accounting for 85% of community-acquired and 50% of hospital-acquired infections. An important step in the uropathogenisis of E. coli is the bacterial adherence with appendages (pili or fimbriae) to the surface urothelium of the host ( Fig. 12.1 ). Type 1 pili are mannose sensitive because their adhesion ability is inhibited by mannose. Type P pili exhibit tropism to the kidney and are found in most strains of E. coli that cause pyelonephritis. Type P pili are mannose resistant since mannose does not affect their adhesion ability.

Excretory urogram demonstrates focal, coarse scarring in the right kidney of an 18-year-old girl with a history of many recurrent fevers between 2 months and 2 years of age. A cystogram when the patient was 2 years old established an atrophic left kidney with marked reflux up to the left kidney and slight reflux up to the right kidney. Excretory urography at the age of 6 years established severe atrophy of the left kidney. She had no infections between the ages of 6 and 15 years. Several reinfections occurred at the age of 15 years, and they ceased with prophylactic therapy. Her blood pressure has remained normal, and her serum creatinine level was 0.9 mg/dL at the age of 18 years. At 21 years of age, she stopped antimicrobial prophylaxis for 18 months without infections or introital colonization with Enterobacteriaceae. Note that all calyces are blunted and that one extends to the capsule (arrowhead) because of atrophy of the overlying cortex.

Cystitis is associated with symptoms of dysuria, frequency, and/or urgency; suprapubic pain; hematuria; and fever. Acute pyelonephritis is associated with fever, chills, flank pain, costovertebral-angle tenderness, nausea, vomiting, and malaise. Painless gross hematuria, or microhematuria in the absence of a positive culture, should always raise the suspicion for urologic malignancy, and a hematuria evaluation must be initiated. Imaging studies are not required in most cases of UTI; however, some clinical scenarios may warrant imaging to identify underlying abnormalities requiring procedural intervention or modification of medical management ( Boxes 12.2 and 12.3 ).

Diagnosis of UTI is dependent on a properly collected urine sample ( Box 12.4 ). Urine dipsticks are most helpful in ruling out a UTI. Positive nitrites, leukocyte esterase, and blood most accurately diagnose a UTI. Multiple aspects of the complete urinalysis may indicate an acute inflammatory response. Pyuria is defined as >5 white blood cells (WBCs)/high-power field (HPF). Moderate pyuria (>50 WBCs/HPF) in conjunction with urinary symptoms may indicate a UTI. The mere presence of WBCs in the urine, however, is not diagnostic of a UTI because pyuria can be found in several common urologic conditions. Leukocyte esterase is produced by the breakdown of WBCs in urine. Its presence is an indication of pyuria but not bacteria specifically. Nitrites are present when bacteria reduce dietary nitrates via the bacterial enzyme nitrate reductase. Not all bacteria produce nitrites, so the absence of nitrites does not mean bacteria are not present. All Enterobacteriaceae produce nitrites, including E. coli, Klebsiella, Enterobacter, Proteus, Citrobacter, Morganella, and Salmonella. Nonnitrite producing bacteria include all gram positives and pseudomonads ( Pseudomonas and Acinetobacter ) ( Fig. 12.2 ). Urine culture is the gold standard for identifying bacteriuria, which supports a diagnosis of UTI in the symptomatic patient. Urine culture results are reported as negative, commensal flora, or positive. Commensal flora includes coagulase-negative staphylococci, α- and nonhemolytic streptococci, diphtheroids, nonpathogenic Neisseria spp., and yeast. In dysuric patients, an appropriate threshold value for defining significant bacteriuria is 10 ² colony-forming unit (CFU)/mL of a known pathogen.

Relevant bacteria for urological infections. ^a Anaerobic bacteria not considered (see Grabe et al., 2015, p. 60 for clarification).

(From Grabe M, Bartoletti R, Bjerklund Johansen TE, et al. Guidelines on urological infections . 2015. https://uroweb.org/wp-content/uploads/19-Urological-infections_LR2.pdf .)

Asymptomatic bacteriuria (AB)

AB occurs when a person has no signs or symptoms of UTI, yet bacteria are identified in a urine sample. In women, the term is used when the same bacteria are identified in quantitative counts of ≥100,000 CFUs in two consecutive voided samples that are obtained in a fashion that minimizes contamination. In men, only one positive, clean-catch sample is necessary. AB should not be treated in most patients , but treatment is recommended in pregnant women and in patients undergoing procedures in which transmucosal bleeding is anticipated ( Box 12.5 ).

Box 12.5

Decision to Treat Asymptomatic Bacteriuria

• 
  

  Do not treat: premenopausal women, nonpregnant patients, patients with diabetes, older community dwellers, older adult institutionalized patients, patients with spinal cord injuries; patients with indwelling catheters, and patients with pyuria with asymptomatic bacteriuria

  
  
• 
  

  Treat: pregnant women and those undergoing procedures in which transmucosal bleeding is anticipated

Antimicrobial therapy.

Antimicrobial selection should be influenced by efficacy, safety, cost, and compliance. The choice of agent and duration of therapy are critical in preventing the perpetuation of antimicrobial resistance as well as treatment-related adverse effects. The mechanism of action, reliable coverage, common adverse reactions, precautions, and contraindications for antimicrobial agents used in the treatment of UTIs are summarized in Tables 12.1 to 12.4 .

Table 12.1

Bacteriostatic Versus Bactericidal Agents

BACTERIOSTATIC	BACTERICIDIAL
Chloramphenicol	Aminoglycosides
Clindamycin	Quinolones
Macrolides	β-Lactams
Sulfonamides	Vancomycin
Tetracycline
Trimethoprim

 

Table 12.2

Mechanism of Action of Common Antimicrobials Used in the Treatment of Urinary Tract Infections

DRUG OR DRUG CLASS	MECHANISM OF ACTION	MECHANISMS OF DRUG RESISTANCE
β-Lactams (penicillins, cephalosporins, aztreonam)	Inhibition of bacterial cell wall synthesis	Production of β-lactamase Penicillin-binding protein altercation Changes in cell wall porin size
Aminoglycosides	Inhibition of ribosomal protein synthesis	Downregulation of bacterial drug uptake Aminoglycoside-modifying enzymes
Quinolones	Inhibition of bacterial DNA gyrase	Mutation in DNA gyrase-binding site Changes in cell wall porin size, active efflux
Fosfomycin	Inhibition of bacterial cell wall synthesis	Novel amino acid substitutions or the loss of function of transporters
Nitrofurantoin	Inhibition of several bacterial enzyme systems	Not fully elucidated
Trimethoprim- sulfamethoxazole	Antagonism of bacterial folate metabolism	Draws folate from environment
Vancomycin	Inhibition of bacterial cell wall synthesis (at β-lactams)	Enzymatic alteration of peptidoglycan

 

Table 12.3

Reliable Coverage of Antimicrobials Used in the Treatment of Commonly Encountered Pathogens

ANTIMICROBIAL AGENT OR CLASS	GRAM-POSITIVE PATHOGENS	GRAM-NEGATIVE PATHOGENS
Amoxicillin or ampicillin	Streptococcus Enterococci	Proteus mirabilis
Amoxicillin with clavulanate	Streptococcus Enterococci	P. mirabilis, Klebsiella spp.
Ampicillin with sulbactam	Staphylococcus (not MRSA) Enterococci	P. mirabilis, H. influenzae, Klebsiella spp.
Antistaphylococcal penicillins	Streptococcus Staphylococcus (not MRSA)	None
Antipseudomonal penicillins	Streptococcus Enterococci	Most, including Pseudomonas aeruginosa
First-generation cephalosporins	Streptococcus Staphylococcus (not MRSA)	Escherichia coli, P. mirabilis, Klebsiella spp.
Second-generation cephalosporins (cefamandole, cefuroxime, cefaclor)	Streptococcus Staphylococcus (not MRSA)	E. coli, P. mirabilis H. influenzae, Klebsiella spp.
Second-generation cephalosporins (cefoxitin, cefotetan)	Streptococcus	E. coli, Proteus spp. (including indole-positive) H. influenzae, Klebsiella spp.
Third-generation cephalosporins (ceftriaxone)	Streptococcus Staphylococcus (not MRSA)	Most, excluding P. aeruginosa
Third-generation cephalosporins (ceftazidime)	Streptococcus	Most, including P. aeruginosa
Aztreonam	None	Most, including P. aeruginosa
Aminoglycosides	Staphylococcus (urine)	Most, including P. aeruginosa
Fluoroquinolones	Streptococcus a	Most, including P. aeruginosa
Nitrofurantoin	Staphylococcus (not MRSA), enterococci	Many Enterobacteriaceae (not Providencia, Serratia, Acinetobacter ) Klebsiella spp.
Fosfomycin	Enterococci	Most Enterobacteriaceae (not P. aeruginosa )
Pivmecillinam	None	Most, excluding P. aeruginosa
Trimethoprim-sulfamethoxazole	Streptococcus, Staphylococcus	Most Enterobacteriaceae (not P. aeruginosa )
Vancomycin	All, including MRSA	None

 

MRSA , Methicillin-resistant Staphylococcus aureus

a May be given with an initial one-time intravenous dose of a long-acting parenteral antimicrobial such as 1 g of ceftriaxone or a consolidated 24-hour dose of an aminoglycoside. See IDSA recommendations.

Table 12.4

Common Adverse Reactions, Precautions, and Contraindications for Antimicrobial Agents Used in the Treatment of Urinary Tract Infections

DRUG OR DRUG CLASS	COMMON ADVERSE REACTIONS	PRECAUTIONS AND CONTRAINDICATIONS
Amoxicillin or ampicillin	Hypersensitivity (immediate or delayed) Gastrointestinal (GI) upset	Increased risk of rash with concomitant viral disease, allopurinol therapy
Amoxicillin with clavulanic acid
Ampicillin with sulbactam
Antistaphylococcal penicillins	Same as with amoxicillin/ampicillin Acute interstitial nephritis (especially methicillin)
Antipseudomonal penicillins	Same as with amoxicillin/ampicillin Hypernatremia (these drugs are given as sodium salt)	Use with caution in patients very sensitive to sodium loading
Cephalosporins	Hypersensitivity GI upset (with oral agents) Positive Coombs test Decreased platelet aggregation	Should not be used in patients with immediate hypersensitivity to penicillins; may use with caution in patients with delayed hypersensitivity reactions
Aztreonam	Hypersensitivity (less than with penicillins)	<1% incidence of cross-reactivity in penicillin or cephalosporin allergic patients
Aminoglycosides	Ototoxicity Nephrotoxicity: nonoliguric azotemia Neuromuscular blockade with high levels	Avoid in pregnant patients and patients with severely impaired renal function, diabetes, or hepatic failure Use with caution in patients with myasthenia gravis Use with caution with other potentially ototoxic and nephrotoxic drugs
Fluoroquinolones	Mild GI effects; dizziness, lightheadedness; photosensitivity Central nervous system effects, including dizziness, tremors, confusion, mood disorder, hallucinations Tendon rupture	Avoid in children or pregnant patients Concomitant antacid, iron, zinc, or sucralfate use dramatically decreases oral absorption Can significantly increase theophylline plasma levels; avoid quinolones or monitor theophylline levels closely. Can lower seizure threshold Monitor glucose levels in patients taking antidiabetic agents because hypoglycemia and hyperglycemia have been reported Can enhance warfarin effects; closely monitor coagulation tests
Fosfomycin	Headache, GI upset, vaginitis	Hypersensitivity to fosfomycin
Pivmecillinam	Rash, GI upset	Use with caution in patients with penicillin hypersensitivity
Nitrofurantoin Peripheral polyneuropathy	GI upset Hemolysis with G6PD deficiency Pulmonary hypersensitivity reactions	Do not use in patients with low creatinine clearance (<50 mL/min) because adequate urine concentrations will not be achieved Monitor long-term patients closely Avoid concomitant probenecid use, which blocks renal excretion of nitrofurantoin Avoid concomitant magnesium or quinolones, which are antagonistic to nitrofurantoin
Trimethoprim- sulfamethoxazole	Hypersensitivity, rash GI upset Photosensitivity Hematologic toxicity (patients with AIDS)	Higher incidence of all adverse reactions occurs in patients with AIDS and in older adults Avoid in pregnant patients Avoid in patients receiving warfarin; concomitant use can significantly elevate prothrombin time
Vancomycin	“Red-man syndrome” Nephrotoxicity and/or ototoxicity when combined with other nephrotoxic and/ototoxic drugs	Use with caution with other potentially ototoxic and nephrotoxic drugs

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related posts:

Lower urinary tract dysfunction and anomalies in children Principles of endourology and fundamentals of laparoscopic and robotic urologic surgery Principles of urologic surgery: Perioperative management Congenital anomalies of the upper urinary tract: UPJ obstruction, duplication anomalies, ectopic ureter, ureterocele, and ureteral anomalies Management of pediatric kidney stone disease Conditions of the external genitalia

Stay updated, free articles. Join our Telegram channel

Join