5 Vital Issues to Know About Stenotrophomonas maltophilia – The Nosocomial Nightmare Or A Complacent Colonizer?

On this article an infectious illnesses pharmacist discusses 5 issues to learn about Stenotrophomonas maltophilia.

Authored by way of: Hunter O. Rondeau, Pharm.D

Article posted 9 July 2022

I consider the primary time listening to the title Stenotrophomonas. In the beginning, I assumed a dialogue a couple of Greek thinker or new dinosaur was once going down. The scientific crew was once suffering to decide what and the right way to way the scientific conundrum this is Stenotrophomonas maltophilia. So who’s “Stenotrophomonas”, and why are discussions surrounding them full of many “neatly, it is dependent”?

Species of Stenotrophomonas are Gram damaging, non-lactose fermenting micro organism. Stenotrophomonas are ubiquitous within the setting, basically because of their position within the nitrogen and sulfur cycle. The most typical species of the genus is Stenotrophomonas maltophilia, and is the one recognized pathogenic species. Title adjustments have happened a couple of instances within the final century, with at one level in its historical past being referred to as Pseudomonas maltophilia. Curiously, Pseudomonas aeruginosa  and Stenotrophomonas maltophilia had been steadily recovered from medical institution sinks upon appearing environmental trying out. In scientific apply, Stenotrophomonas maltophilia is relatively affectionately known as “Steno”. 

After I say ubiquitous, I imply this organism is all over. Steno has been recovered in soil, plant roots, water remedy facilities, dialysate answer, faucet water, bottled water, ice machines – you title it. Steno’s skill to shape biofilms lets in it to stick to and colonize scientific apparatus temporarily and steadily. 

Because of Steno’s ubiquitous presence and biofilm functions, it’s related to many kinds of infections. Experiences of osteomyelitis, endocarditis, meningitis exist, however extra steadily Steno seems the place there may be {hardware} to dangle to. Bring to mind urinary restoration within the presence of a urinary catheter, bacteremia within the presence of a central line catheter, and sputum restoration within the presence of an endotracheal tube.

Mortality related to Steno infections may also be extremely prime. In bacteremic sufferers, as much as 69% mortality has been noticed. Top mortality is particularly observed in immunocompromised sufferers. A lung an infection because of Steno may also be deadly, because the pathogen can create proteins that let for tissue necrosis and hemorrhage of pulmonary tissue. The query of: “Is the Steno provide as a result of they’re significantly sick, or did the Steno lead them to develop into significantly sick?” – makes the verdict to regard Steno tougher, because the few antibiotic choices we now have to be had may also be restricted by way of their tolerability. 

Some of the difficult hindrances when encountering Steno is its spectacular antibiotic resistance profile. Because of it’s harboring of 2 β-lactamases, L1 (metallo-β-lactamase) and L2 (cephalosporinase), Steno is unphased by way of not unusual broad-spectrum regimens like vanc-zosyn, vanc-cefepime or vanc-meropenem. Even more recent remedies like TOL/TAZ, CAZ/AVI and MERO/VAB are not any fit for this mixture of β-lactamases. Intrinsic resistance to aminoglycosides and macrolides may be observed. With out diving into the remainder of its mechanisms of resistance, the frontline antibiotics with essentially the most knowledge to reinforce their use are TMP/SMX, levofloxacin and minocycline. Even with those brokers, Steno has confirmed it could broaden resistance to they all, albeit, some extra temporarily than others.

On this article, I can determine and speak about 5 key questions well being care practitioners must ask when encountering Stenotrophomonas maltophilia….

Query #1: Is that this a Stenotrophomonas an infection or a Stenotrophomonas colonization?

Simply since you get better a micro organism in tradition, does no longer at all times imply you have got an an infection. Take into accout that Steno LOVES to colonize {hardware}. You’ll steadily in finding Steno in cultures the place catheters are concerned, particularly central strains. A steadily mentioned chance issue for Stenotrophomonas an infection and mortality is the use, and failure to take away a central venous catheter. 

Query #2:. Must I exploit TMP/SMX to regard Stenotrophomonas?  What dose and system must I exploit?

TMP/SMX is the most popular agent, however there are lots of problems that can save you its use. Hyperkalemia, bone marrow suppression, hepatotoxicity and nephrotoxicity at Steno treating doses (i.e., upper doses) are extra not unusual.

With the IV system, TMP/SMX calls for a great amount of diluent with D5W which is able to exceed 1.5 liters in line with day. You’ll simply fluid overload a affected person with prime doses of IV TMP/SMX if no longer cautious! Additionally beware it has a brief expiration date after blending. Some establishments cap particular person doses at 500 mg because of the fluid quantity and brief steadiness as soon as blended within the pharmacy.

The every year up to date IDSA pointers for treating resistant Gram damaging rods discusses TMP/SMX intimately, in addition to the newer, decrease dose advice of 8-12mg/kg/day divided q8-q12h (up to now 15-20mg/kg/day).

Whilst IV or PO is advisable, the use of the oral system must be thought to be when 4 key standards are met:

i. The Steno isolate is prone to TMP/SMX

ii. The affected person is hemodynamically solid

iii. Cheap supply keep an eye on has been accomplished / the sufferers scientific trajectory is appropriate for oral treatment

iv. The affected person can soak up orally administered medicines

Query #3: When must I no longer use SMX/TMP for Stenotrophomonas? What drug must I exploit as a substitute?

If resistance or different problems save you SMX/TMP use, different brokers reminiscent of levofloxacin, tetracyclines or cefiderocol is also thought to be for gentle infections. Ceftazidime+avibactam and aztreonam in combination are advisable by way of the IDSA pointers for average to critical infections when TMP/SMX or minocycline can’t be used, as this mixture is in a position to inhibit each β-lactamases (avibactam inhibits L2 to permit aztreonam to inhibit L1). Minocycline, at upper than conventional doses, has restricted, however promising effects. Cefiderocol has very restricted scientific knowledge, however may also be thought to be to be used on my own for gentle treatment, or as an adjunctive for average to critical infections.

No RCT’s had been finished on this house, and lots of the wisdom of Steno comes from small learn about populations of retrospective knowledge. On the other hand, some of the greatest research about Steno was once printed previous this yr, discovering similar results between TMP/SMX and levofloxacin for bacteremias and pneumonia. Watch out with the use of levofloxacin, as Stenotrophomonas uncovered to fluoroquinolones could cause resistance not to simplest fluoroquinolones, however different frontline brokers, like sulfonamides and tetracyclines.

Ceftazidime is now not advisable for Stenotrophomonas, because the breakpoints most likely don’t correctly constitute the affect of the β-lactamases in vivo. It might be argued that Steno “infections” handled “effectively” with ceftazidime had been most likely colonizations and no longer true infections.

Query #4: How am I going to get supply keep an eye on?

As up to now discussed, Steno LOVES to colonize scientific apparatus.

Trade your catheters until you need Steno to stay waving hi each time you acquire a tradition tradition

Query #5: How lengthy do I deal with Stenotrophomonas infections for?

Trials comparing periods with Steno haven’t been carried out and there may be numerous uncertainty within the length of treatment, as sufferers in most cases obtain longer classes of treatment (>14 days). Steno steadily seems attributable to over the top antibiotic use, so much more antibiotics appear counterintuitive. In response to the site of the an infection, respective pointers can assist information periods (i.e. 7-10 days for HAP/VAP and 7-14 days for bacteremia).

Are you strolling away with extra questions than solutions? As with many stuff within the ID global, black and white solutions are very unusual. As Stenotrophomonas is without doubt one of the organisms integrated within the every year up to date IDSA’s resistant GNR pointers, be in search of updates there!

Stenotrophomonas Readings and Sources

1. Microbiology of Stenotrophomonas

2. Taxonomy of Stenotrophomonas

3. Possibility Elements for Stenotrophomonas Infections

4. IDSA Steerage at the Remedy of Antimicrobial-Resistant Gram-Adverse Infections: Model 2.0

5. Fluoroquinolone Resistance in Stenotrophomonas

6. TMP/SMX vs. Fluoroquinolone vs Minocycline

7. TMP/SMX vs Levofloxacin

Further Recommended Studying:

Heil EL, Bork JT, Abbo LM, et al. Optimizing the Control of Straight forward Gramnegative Bloodstream Infections: Consensus Steerage The usage of a Changed Delphi Procedure [In press]. Open Discussion board Infect Dis 2021; 8: ofab434.


Hunter O. Rondeau, Pharm.D is a Kansan local who gained their Pharm.D.from the College of Kansas (Wichita, KS) in 2021. He these days is a PGY-2 pharmacy resident on the College of MN Clinical Middle – M Well being Fairview in Minneapolis, MN. His pursuits come with antimicrobial stewardship, Gram damaging resistance, and educating infectious illnesses via FOAMed.

In his spare time, he creates uniqueness cocktails.

You’ll in finding him on Twitter @Floralquinolone.


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