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Patient context: 88-year-old man with bronchiectasis and chronic P. aeruginosa infection.
Isolates (as reported):
Purpose: GP/clinic reference for long-term suppression strategy, nebulised regimens, exacerbation antibiotics, evidence, guidelines, and age-related cautions.
Not a substitute for respiratory specialist initiation and shared care.
Preferred approach for chronic P. aeruginosa with frequent exacerbations:
1. Optimise airway clearance (and treat reversible contributors).
2. Start long-term inhaled (nebulised) antipseudomonal antibiotic under respiratory specialist care.
3. Formally review response (exacerbation rate, sputum, tolerance) at about 3–6 months, then at least 6-monthly. Stop if ineffective or poorly tolerated.
4. Do not use long-term oral ciprofloxacin for suppression when isolates are intermediate — unpredictable efficacy, rapid resistance selection, and high fluoroquinolone toxicity risk at age 88.
5. Oral macrolide (e.g. azithromycin three times weekly) is an alternative if inhaled therapy is not tolerated, or as add-on if exacerbations remain frequent (after ECG/QTc, LFTs, and exclusion of NTM).
How this susceptibility profile steers choice:
| Finding | Implication |
|---|---|
| Tobramycin-susceptible strain | Nebulised **tobramycin** is microbiologically reasonable (and often PBS-accessible in Australia). |
| Meropenem-susceptible strain | Reserve **IV meropenem** for moderate–severe **exacerbations**, not long-term outpatient suppression. |
| Intermediate ciprofloxacin | Avoid chronic fluoroquinolone suppression (oral or inhaled ciprofloxacin programmes). |
| Intermediate ceftazidime (if confirmed) | Do not rely on ceftazidime as sole empiric IV agent for severe exacerbations without specialist/micro input; consider based on full antibiogram (e.g. meropenem-susceptible strain). |
Guideline-aligned first choices for suppression:
| Item | Detail |
|---|---|
| **Indication** | Long-term suppression of chronic *P. aeruginosa* in non-CF bronchiectasis with frequent exacerbations (usually off-label for non-CF). |
| **Dose** | **1–2 million IU (MU) twice daily**, continuous (not month-on/month-off). Many protocols start at **1 MU BD**. |
| **Diluent** | Reconstitute with **0.9% sodium chloride** (plastic ampoules preferred for no-needle technique). Typical: **1 MU in ~2.5–3 mL**; **2 MU in ~4 mL**. Water for injection is an alternative where protocols allow. |
| **Mixing** | Add diluent to powder; **gently swirl/roll — do not shake** (frothing impairs nebulisation). Allow to stand briefly; solution may be slightly hazy. |
| **Nebuliser** | Jet nebuliser (e.g. **PARI LC Plus**, Sidestream) with suitable compressor, **or** **I-neb** Adaptive Aerosol Delivery (used in PROMIS / Promixin pathways). |
| **Order of therapies** | Bronchodilator → airway clearance / hypertonic saline (if used) → **antibiotic last**. Mouth rinse after. |
| **First dose** | **Supervised** (risk of bronchospasm); consider pre-dose bronchodilator and pre/post spirometry where feasible. |
| **Duration** | Long-term while beneficial; specialist review of efficacy/toxicity. Some services use alternate-month cycling with another inhaled agent — only if specified by the initiating clinician. |
| **AU note** | Colistin (e.g. Tadim) is often **off-label** for non-CF BE and may need hospital/specialist supply pathway. |
| Item | Detail |
|---|---|
| **Rationale here** | At least one strain **susceptible to tobramycin**; PBS Authority listing for proven *P. aeruginosa* often makes this the most accessible funded inhaled option in Australia. |
| **Dose** | **Tobramycin 300 mg / 5 mL** nebuliser solution **twice daily**. |
| **Cycle** | Typical CF-style cycle extrapolated to non-CF BE: **28 days on / 28 days off**, ongoing while beneficial. |
| **Nebuliser** | Dedicated jet nebuliser (commonly **PARI LC Plus** or equivalent); do not mix with other nebulised drugs in the same chamber unless the product information allows. |
| **Monitoring (esp. age 88)** | Baseline and periodic **renal function**; watch for **ototoxicity / vestibular** symptoms; supervised first doses for bronchospasm. Prefer **colistin or macrolide** if significant CKD or hearing impairment. |
| **Evidence note** | Supportive smaller RCTs (bacterial density ± hospitalisation benefit); exacerbation-reduction evidence is weaker than PROMIS for colistin. |
Meropenem is for exacerbations, not chronic outpatient suppression.
| Use | Guidance |
|---|---|
| **When** | Moderate–severe exacerbation, failed oral options, inability to take oral therapy, or when susceptibility / severity favours an IV antipseudomonal β-lactam. |
| **Why relevant here** | One strain is **meropenem-susceptible** — useful IV choice for that isolate when IV therapy is needed. |
| **How** | Specialist/hospital-directed IV course (often ~14 days for *Pseudomonas* exacerbations per BTS/TSANZ-style practice); duration individualised. |
| **Not for** | Long-term home “suppression,” continuous outpatient IV without a clear plan, or replacement of inhaled maintenance therapy. |
| **Elderly** | Adjust for renal function; monitor for cytopenias, seizures risk at high doses/renal impairment, *C. difficile*. In frail elderly, β-lactam monotherapy is often preferred over adding systemic aminoglycoside unless multi-resistant organism or specialist advice says otherwise (TSANZ). |
After the IV course, resume / continue the inhaled maintenance strategy and airway clearance.
(Haworth et al., Lancet Respir Med 2024)
| PROMIS-I | PROMIS-II | |
|---|---|---|
| **Population** | Non-CF bronchiectasis, chronic *P. aeruginosa*, ≥2 exacerbations requiring oral antibiotics or ≥1 requiring IV in prior year | Same |
| **Intervention** | Colistimethate via **I-neb**, BD, 12 months | Same |
| **Primary endpoint** | Mean annual exacerbation rate | Same |
| **Main finding** | **0.58 vs 0.95** (rate ratio **0.61**, 95% CI 0.46–0.82, p=0.0010); fewer severe exacerbations; QoL improved | Overall **no difference** (0.89 vs 0.89); trial disrupted/terminated early due to COVID; pre-pandemic period more consistent with PROMIS-I |
| **Takeaway** | Strongest modern phase 3 support for nebulised colistin; supports guideline use despite PROMIS-II inconsistency. |
Earlier: Haworth et al., AJRCCM 2014 — colistin 1 MU BD via I-neb; primary time-to-exacerbation not met in ITT; benefit in adherent subgroup; reduced bacterial density.
(Haworth et al., Lancet Respir Med 2019) — poor fit for intermediate ciprofloxacin
| Detail | |
|---|---|
| **Drug** | Nebulised liposomal + free ciprofloxacin (ARD-3150), once daily, **28 on / 28 off** × 48 weeks |
| **Population** | Non-CF BE + chronic *P. aeruginosa* |
| **Primary** | Time to first pulmonary exacerbation |
| **ORBIT-4** | Median 230 vs 158 days, HR 0.72, p=0.032 |
| **ORBIT-3** | 214 vs 136 days, HR 0.99, p=0.97 (NS) |
| **Status** | Not approved/marketed; **not preferred** when isolates are ciprofloxacin-intermediate |
(Related: RESPIRE-1/2 ciprofloxacin DPI — mixed results; not marketed.)
(Barker et al., Lancet Respir Med 2014) — failed to establish a role
| Detail | |
|---|---|
| **Regimen** | AZLI 75 mg TID, two cycles of 4 weeks on / 4 weeks off |
| **Primary** | QOL-B respiratory symptoms at 4 weeks |
| **AIR-BX1** | +0.8, p=0.68 (NS) |
| **AIR-BX2** | +4.6, p=0.011 but below clinically meaningful MID (~8); more AEs/discontinuations with AZLI |
| **Takeaway** | Not recommended as standard long-term therapy in non-CF BE. |
| Trial | Findings |
|---|---|
| **Barker 2000** (*AJRCCM*) | Tobramycin 300 mg BD × 28 days — significant ↓ sputum *P. aeruginosa* density; clinical improvement reported |
| **Drobnic 2005** (*Ann Pharmacother*) | 300 mg BD, cyclic — ↓ hospitalisations/hospital days and bacterial density; no clear reduction in exacerbation rate / FEV1 / QoL; bronchospasm in some |
| **Overall** | Supports microbiological effect and possible healthcare-use benefit; **weaker exacerbation-prevention evidence** than PROMIS colistin |
| Guideline | Position relevant to this patient |
|---|---|
| **BTS 2019** (*Thorax* 2019;74 Suppl 1) | If ≥3 exacerbations/year and chronic *P. aeruginosa*: **inhaled colistin first (B)**; inhaled gentamicin second-line; macrolide as alternative or add-on. Eradication regimens for *new* growth differ from chronic suppression. Prophylaxis should be specialist-initiated; 6-monthly review. |
| **ERS (updated clinical practice guideline, Eur Respir J 2025)** | **Strong recommendation** for long-term inhaled antibiotics in chronic *P. aeruginosa* at high exacerbation risk (≥2 exacerbations/year **or** ≥1 severe **or** 1 exacerbation + severe daily symptoms). Conditional against routine long-term oral **non-macrolide** antibiotics. Define treatment period and reassess response. |
| **TSANZ 2023** (*Respirology* 2023;28:339–349) | Do **not** routinely use long-term inhaled antibiotics in *stable* disease. **Consider** inhaled antibiotics (aminoglycosides or colistin) in adults with *P. aeruginosa* and ≥3 exacerbations/year; specialist advice; individualise. |
1. Nephrotoxicity / ototoxicity (tobramycin, gentamicin, systemic aminoglycosides): check baseline eGFR/creatinine; recheck periodically; ask about hearing, tinnitus, imbalance. Prefer colistin or macrolide if significant renal impairment or known hearing loss.
2. Bronchospasm: common with nebulised antibiotics — first dose supervised; pre-treat with bronchodilator if reactive; stop if severe.
3. Fluoroquinolones: avoid long courses — tendon, CNS, QT, aortic, hypoglycaemia risks; intermediate MIC further argues against chronic cipro.
4. Meropenem IV: renal dose adjustment; C. difficile; not a maintenance drug.
5. Macrolide fallback: ECG for QTc; exclude NTM before long-term azithromycin; drug interactions.
6. Polypharmacy / cognition / dexterity: assess ability to reconstitute and nebulise BD; involve carers/pharmacy support; simpler PBS tobramycin ampoules may be easier than reconstituting colistin powder for some patients.
7. Monitoring plan: sputum culture periodically (in vitro resistance may not equal clinical failure for inhaled agents); exacerbation count; weight/nutrition; vaccine status; 6-monthly specialist review while on long-term inhaled antibiotics.
1. Confirm full lab report (exact MICs; clarify “restrazol/ceftazidime”).
2. Refer / confirm with respiratory: start long-term nebulised suppression + airway clearance.
3. Agent choice:
- Colistin 1 MU BD continuous (dilute in 0.9% NaCl; jet nebuliser or I-neb; supervised first dose), or
- Tobramycin 300 mg BD, 28 on / 28 off if PBS access and renal/hearing acceptable (isolate susceptible).
4. Do not use long-term oral ciprofloxacin for suppression.
5. For exacerbations needing IV therapy: use susceptibility-guided IV agents (e.g. meropenem for the meropenem-susceptible strain); then return to inhaled maintenance.
6. If inhaled therapy fails/intolerable: consider azithromycin thrice weekly after QTc/NTM screen.
7. Review efficacy and toxicity at 3–6 months, then at least 6-monthly.
Prepared for clinic reference. Verify local PBS/hospital formulary and specialist protocol before prescribing.