Urinary Tract Infections & Bacterial Meningitis

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

UTI top 3: E. coli (80% community-acquired), Klebsiella, Proteus. Catheter-associated = add Pseudomonas, Enterococcus, Candida.

Meningitis — Age-based pathogens (NEET PG high-yield):

• Neonates (0–1 mo): Group B Strep, E. coli, Listeria monocytogenes
• Infants/Children (1 mo–18 yr): S. pneumoniae, N. meningitidis, H. influenzae type b (now rare due to vaccine)
• Adults (18–50 yr): S. pneumoniae, N. meningitidis
• Elderly (>50 yr): S. pneumoniae, Listeria, Gram-negative bacilli

Lumber Puncture interpretation: Normal CSF glucose 40–70 mg/dL (2/3 of blood glucose); protein <45 mg/dL; <5 WBCs/µL

⚡ Exam tip: LP showing ↑protein, ↓glucose, ↑WBCs (neutrophilic in bacterial, lymphocytic in viral/TB/fungal) = meningitis until proven otherwise.

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Urinary Tract Infections

Classification

Type	Definition	Clinical features
Cystitis	Lower UTI, bladder inflammation	Dysuria, frequency, urgency, suprapubic pain
Pyelonephritis	Upper UTI, kidney parenchyma	Fever, flank pain, costovertebral angle tenderness
Urethritis	Urethral inflammation	Discharge, dysuria
prostatitis	Prostatic inflammation	Perineal pain, fever, tender prostate

Etiology

Uncomplicated cystitis (young, non-pregnant women): E. coli (75–95%), S. saprophyticus (5–15%), Klebsiella, Proteus

Complicated UTI (men, pregnant women, catheter, diabetes, structural abnormality):

• Gram-negatives: E. coli, Klebsiella, Proteus, Pseudomonas
• Gram-positives: Enterococcus faecalis, S. aureus (S. saprophyticus rare)

Recurrent UTI: Re-infection (new strain, most common) vs relapse (same strain, indicates anatomic/functional abnormality)

Pathogenesis

• Ascending infection is the most common route: uropathogenic E. coli (UPEC) colonize periurethral area → ascend urethra → bladder
• UPEC virulence factors: P-fimbriae (pyelonephritis-associated pili, bind P blood group antigen), type 1 pili (bind mannose on uroepithelium), adhesins, capsular K antigen, aerobactin (iron acquisition)
• H. influenzae and S. epidermidis can cause UTI in children

Predisposing Factors

Female anatomy (short urethra), sexual activity, pregnancy (hormonal changes + ureteral compression), urinary obstruction (stones, tumor, BPH), vesicoureteral reflux, catheterization, diabetes mellitus, immunosuppression

Diagnosis

• Urine routine: >10 WBCs/hpf (pyuria), bacteria (≥10⁵ CFU/mL in clean-catch midstream is significant)
• Urine culture: Gold standard; suprapubic aspirate (any bacteria = significant)
• Urine dipstick: Leukocyte esterase (+ in pyuria), nitrite (+ in Gram-negative bacteriuria, especially E. coli)
• Imaging: Ultrasound for obstruction, VCUG for reflux

Complications

• Pyelonephritis: Interstitial nephritis, papillary necrosis
• Chronic pyelonephritis: Scarring, reflux nephropathy
• Emphysematous pyelonephritis: Gas-forming organisms in diabetics
• Xanthogranulomatous pyelonephritis: Lipid-laden macrophages; associated with Proteus + obstruction + stones

Treatment

Condition	First-line Treatment
Uncomplicated cystitis	Nitrofurantoin 5–7d OR Fosfomycin single dose OR TMP-SMX 3d
Complicated UTI	Fluoroquinolone (CIP/COT) 7–14d
Pyelonephritis	CIP/OFX 7–14d OR Ceftriaxone IV → oral

Prophylaxis for recurrent UTI: Post-coital nitrofurantoin OR low-dose TMP-SMX

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Bacterial Meningitis

Clinical Features

Meningeal signs: Neck stiffness (nuchal rigidity), Kernig sign (pain on knee extension with hip at 90°), Brudzinski sign (hip flexion on neck flexion)

In neonates/infants: Poor feeding, irritability, lethargy, bulging fontanelle, seizures — meningeal signs may be absent

In elderly: Altered mental status predominates; fever may be low-grade

CSF Analysis in Meningitis

Parameter	Normal	Bacterial	Viral	TB	Fungal
Appearance	Clear	Turbid/purulent	Clear	Clear/fibrin web	Turbid
WBC (/µL)	<5	>1000 (neutrophil predominant)	50–1000 (lymphocyte)	50–500 (lymphocyte)	50–500 (lymphocyte)
Protein (mg/dL)	<45	>100–500	<100	100–300	>100
Glucose (mg/dL)	40–70	<40 (<2/3 blood glucose)	Normal	Low	Low
Gram stain	—	+ in 70–90%	—	— (AFB scanty)	India ink/KOH +

Critical: CSF glucose is LOW in bacterial, TB, and fungal meningitis; NORMAL in viral. Clue: If glucose is very low → think bacterial or Cryptococcus.

Specific Pathogens

Neisseria meningitidis (Meningococcal)

• Gram-negative diplococci; lancet-shaped
• Causes both meningitis and meningococcemia (septicemia with petechial rash)
• Waterhouse-Friderichsen syndrome: Bilateral adrenal hemorrhage → acute adrenal insufficiency; associated with DIC
• Vaccine: Meningococcal conjugate (MenACWY) for adolescents; MenB for high-risk
• Prophylaxis for close contacts: Rifampin OR ciprofloxacin OR ceftriaxone

Streptococcus pneumoniae (Pneumococcal)

• Gram-positive diplococci, alpha-hemolytic, optochin-sensitive
• #1 cause of bacterial meningitis in adults (>20 years)
• Source: Colonized nasopharynx (asymptomatic carrier state)
• Associated with otitis media, sinusitis, pneumonia, skull fracture (CSF leak)
• High mortality (30%); increased resistance to penicillin → use ceftriaxone + vancomycin empirically

Haemophilus influenzae type b

• Gram-negative coccobacillus
• Was #1 cause of childhood meningitis before Hib vaccine (introduced 1985)
• Now rare due to universal vaccination; still seen in unvaccinated children
• Associated with epiglottitis, pneumonia, septic arthritis

Group B Streptococcus (Streptococcus agalactiae)

• Gram-positive cocci in chains
• #1 cause of neonatal meningitis (early-onset, <7 days)
• Colonizes maternal vaginal/rectal flora; transmitted during delivery
• Also causes septicemia and pneumonia in neonates
• Late-onset (7–30 days): often meningitis; source may be nosocomial

Listeria monocytogenes

• Gram-positive bacillus, facultative intracellular pathogen
• Affects neonates, elderly, immunocompromised, pregnant women
• ” tumble gram-positive rod” — characteristic tumbling motility at 22–28°C
• Transmitted via contaminated food (soft cheese, deli meats, unpasteurized milk)
• Can cause bacteremia, meningitis, and perinatal infections (granulomatosis infantiseptica)
• Does NOT respond to cephalosporins — treat with ampicillin ± gentamicin

Treatment (Empirical — Before Culture)

Age Group	Empirical Antibiotics
0–1 month	Ampicillin + Cefotaxime (± Gentamicin for Listeria)
1 month–50 years	Ceftriaxone + Vancomycin
>50 years or immunocompromised	Ceftriaxone + Vancomycin + Ampicillin (for Listeria)

Add dexamethasone 15–30 min before or with first antibiotic dose in pneumococcal meningitis (reduces neurologic sequelae, not mortality).

Prevention

• Hib vaccine: Conjugate vaccine (Hib PRP-T) at 2, 4, 6 months + booster at 12–15 months
• PCV13: Pneumococcal conjugate vaccine at 2, 4, 6 months + booster at 12–15 months
• Meningococcal vaccine: MenACWY (conjugate) at 11–12 years + booster at 16; MenB (recombinant) for high-risk
• Chemoprophylaxis: Rifampin/ciprofloxacin/ceftriaxone for meningococcal contacts

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Meningitis with Special Presentations

Tuberculous Meningitis

• Subacute onset over 1–2 weeks
• CSF: lymphocytic pleocytosis, very high protein (>200 mg/dL), very low glucose
• Often with cranial nerve palsies (CN VI, VII most common)
• MRI: Basal meningeal enhancement, infarcts in MCA territory
• Treatment: RIPE (Rifampin, Isoniazid, Pyrazinamide, Ethambutol) + steroids
• Complications: Hydrocephalus,stroke, permanent neurologic deficits

Fungal Meningitis (Cryptococcus neoformans)

• Common in HIV/AIDS (CD4 <100)
• CSF: Opening pressure often very high, mild pleocytosis, low glucose, high protein
• India ink stain: Encapsulated yeasts with thick polysaccharide capsule (80% sensitivity in AIDS)
• Cryptococcal antigen: Very sensitive and specific (CrAg in CSF)
• Treatment: Amphotericin B + Flucytosine (induction), then Fluconazole (consolidation/maintenance)

Aseptic Meningitis

• Self-limiting; CSF lymphocytic
• Causes: Enteroviruses (most common), HSV-2, mumps, HIV seroconversion, partially treated bacterial meningitis, chemical meningitis
• Enteroviruses: Hand-foot-mouth disease, herpangina; PCR of CSF is diagnostic

Complication: subdural Empyema & Brain Abscess

• Subdural empyema: Infection in subdural space; most commonly from sinusitis (streptococci, staphylococci); surgical emergency
• Brain abscess: Hematogenous spread (cyanotic heart disease, dental infections) or direct extension (otitis media → temporal lobe; sinusitis → frontal lobe); causative organisms vary by source; CT/MRI with ring enhancement; treatment: antibiotics ± surgical drainage

Key NEET PG Pearls

1. E. coli is the #1 cause of uncomplicated UTI; also most common in pregnancy
2. UPEC uses P-fimbriae (bind P blood group antigen) to cause pyelonephritis
3. S. saprophyticus is the #2 cause of UTI in sexually active young women (right after E. coli)
4. Proteus mirabilis produces urease → alkaline urine → struvite kidney stones (staghorn calculi)
5. Klebsiella is notorious for causing lung abscesses and is a common nosocomial UTI pathogen
6. Group B Strep (S. agalactiae) = #1 cause of neonatal meningitis; screen all pregnant women at 35–37 weeks
7. Listeria in pregnant woman/neonate = ampicillin; remember cephalosporins don’t cover Listeria
8. Waterhouse-Friderichsen = bilateral adrenal hemorrhage in meningococcemia with DIC
9. Dexamethasone in bacterial meningitis: given before/with first antibiotic dose in pneumococcal meningitis; reduces hearing loss and neurologic sequelae
10. CSF in partially treated bacterial meningitis can look viral (lymphocytic, mildly elevated protein) — always correlate clinically

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