STEPTRACKERMICROBIOLOGY + NEPHROLOGY + GYNECOLOGY | INFECTIONS BY SYSTEM | HIGH-YIELD REVIEW

Urinary Tract & Sexually Transmitted Infections

Ascending bowel flora cause most UTIs; STIs are sorted by discharge, ulcer or systemic picture — and one STI should always prompt testing for the others.

FOCUS ON
UTI organisms: E coli (most), S saprophyticus (sexually active young women), Klebsiella, Proteus (struvite stones), Enterococcus, Pseudomonas (catheters). Risks: female urethra, sex, obstruction, catheters, pregnancy, diabetes. Labs: ⁺ leukocyte esterase (WBCs), ⁺ nitrite (gram-negative reduction of nitrate), WBC casts = pyelonephritis. STIs: urethritis/cervicitis — C trachomatis (most common bacterial STI) and N gonorrhoeae (NAAT; ceftriaxone ± doxycycline); ulcers — syphilis (painless), HSV and chancroid (painful), LGV; vaginitis — trichomonas, BV, Candida; systemic — HIV, HBV, HCV. Screen sexually active women ≤ 24 for chlamydia/gonorrhea.
INFECTION
ORGANISMS · RISK
CLINICAL PICTURE
DIAGNOSIS · TREATMENT
Acute cystitis
E coli (P fimbriae), S saprophyticus, Klebsiella, Proteus
Dysuria, frequency, urgency, suprapubic pain, no fever
UA: ⁺ esterase ± nitrite · nitrofurantoin, TMP-SMX, fosfomycin
Pyelonephritis
Ascending infection; vesicoureteral reflux, obstruction
Fever, flank pain, CVA tenderness, nausea
WBC casts · culture · fluoroquinolone or ceftriaxone
Catheter-associated UTI
E coli, Pseudomonas, Enterococcus, Candida; biofilm
Fever, often few local symptoms
Remove or replace catheter
UTI in pregnancy
Asymptomatic bacteriuria → pyelonephritis, preterm labor
Screen at first visit
Treat even if asymptomatic (nitrofurantoin, cephalexin)
Sterile pyuria
Chlamydia/gonorrhea urethritis, renal TB, interstitial nephritis, recent antibiotics
WBCs without growth on routine culture
NAAT, AFB culture
Chlamydia trachomatis (D–K)
Obligate intracellular; often asymptomatic
Urethritis, cervicitis, PID, epididymitis, reactive arthritis; neonatal conjunctivitis/pneumonia
NAAT · doxycycline (azithromycin in pregnancy)
Gonorrhea
N gonorrhoeae
Purulent discharge, PID, disseminated arthritis-dermatitis
NAAT · ceftriaxone IM
Pelvic inflammatory disease
Chlamydia, gonorrhea, anaerobes
Lower abdominal pain, cervical motion tenderness, fever; → infertility, ectopic, Fitz-Hugh–Curtis
Ceftriaxone + doxycycline + metronidazole
Mycoplasma genitalium
No cell wall
Persistent urethritis/cervicitis after standard therapy
Moxifloxacin (macrolide resistance)
Lymphogranuloma venereum
C trachomatis L1–L3
Painless ulcer → painful inguinal buboes, proctocolitis in MSM
Doxycycline 3 weeks
Genital ulcers
T pallidum, HSV, H ducreyi, K granulomatis
Painless indurated vs painful vesicles vs painful ragged
See 4.08
Vaginitis
Gardnerella (BV), Trichomonas, Candida
Fishy gray · frothy green · thick white
See 4.09
Anogenital warts
HPV 6, 11
Cauliflower lesions
HPV vaccine prevents

Mechanism — reading the dipstick

Neutrophils in urine
→
Leukocyte esterase ⁺
Gram-negative rodsNitrate reductase
→
Nitrite ⁺
→
Usually EnterobacteralesEnterococcus, S saprophyticus are nitrite −
Urease (Proteus, Klebsiella)
→
Alkaline urine → struvite

Discharge syndromes

SYNDROME
ORGANISMS
TREATMENT
Urethritis / cervicitis
Chlamydia, gonorrhea, M genitalium, Trichomonas
Ceftriaxone + doxycycline
PID
Chlamydia, gonorrhea, anaerobes
+ metronidazole
Epididymitis < 35
Chlamydia, gonorrhea
Ceftriaxone + doxycycline
Epididymitis > 35
E coli (enteric)
Fluoroquinolone

How it's tested

COMMON CONFUSIONA young woman with dysuria, pyuria and a negative culture may have chlamydia urethritis, not cystitis — test with NAAT.
THE TRAPNitrofurantoin doesn't reach kidney tissue — don't use it for pyelonephritis.
YOUR APPROACHLower vs upper tract → host (pregnant, catheter, male) → organism → drug that reaches the site. For STIs: syndrome → organism → treat partner → screen for HIV, syphilis, HBV, HCV.

If you see… think…

Most common cause of UTI → E coli
Sexually active 20-year-old woman with nitrite-negative UTI → S saprophyticus
Fever, flank pain, WBC casts → pyelonephritis
Staghorn calculus, alkaline urine → Proteus
Pyuria with negative routine culture in a young adult → chlamydia urethritis
Most common bacterial STI → C trachomatis
Cervical motion tenderness and adnexal pain → PID
Painful inguinal buboes after a painless ulcer → LGV (L1–L3)
Pregnant woman with asymptomatic bacteriuria → treat it
Testicular pain in a 60-year-old with BPH → E coli epididymitis