60. Nobbling the Nonfermentors: Pseudomonas Part 2 - Treatment & Resistance

In part 2, we discuss the limited treatment options for pseudomonas infection, some wildcard options and the resistance mechanisms that make Pseudomonas such a tricky bugger to treat! 

Transcript

Callum: 0:01

Hello and welcome to this part 2 of our conversation on Pseudomonas. Part 1 covers the basics of the Pseudomonas genus and in this episode we focus on treatment and Pseudomonas resistance mechanisms. Hope you enjoy it.

Jame: 0:17

Soon may the editing come to discontinue the Tezo Sun, one day when the Seerpiece done will take our leave and go.

Callum: 0:30

So this horrible organism, pseudomonas, that we're having our Pseudomon episode about James, how do we get rid of it? How do we treat it?

Jame: 0:38

Well, this is about to become a real moan and not a Pseudomon callum, because this is absurdly difficult to kill. And Pseudomonas I think of my day job, I think of an infection specialist has two great enemies in life in the bacteria space. This is One of them is Staph aureus in the blood and the other Pseudomonas wherever it is, because it's got loads of intrinsic resistances and loads of required resistance mechanisms for the few drugs that we can use. So what are they? Well, there are basically three classes of drug that we can use Betalatams, quinolones and Amnibuloxides, and that's it.

Jame: 1:27

So, taking the Betalatams first, the Penicillins, you only start to acquire antiseminal activity once you get to the Antisudomonal Penicillin. So that's Pipericillin and Tisarsillin. So Tisarsillin was the Betalatam ingredient of Tisarsillin, clavilanator Taimentin that's not available in Europe at the moment, and Piptas, pipericillin, tisarbatam or Tisarsin or Zosin in America, is the combination that we use. So you could use Pipericillin on its own, and apparently in France they do have Pipericillin on its own, but the UK, and I'm pretty sure the US and Australasia too, only have Pipericillin in combination with the Tisarbatam.

Callum: 2:14

Which is probably quite useful in Pseudomonas. Yeah, even if it's sensitive to just Pipericillin.

Jame: 2:21

And then for the Keflosporins, you, going up the generations, you acquire antiseminal activity, somewhat confusingly, half way through the third generation. So Keftazidine is a third gen, so is Keftraaxon and Keftaxim, but they don't have antiseminal activity, but Keftazidine does. I think that the Taz is a bit like the Taz of Tazosin, that's how I remember it.

Callum: 2:47

So for anyone who wants a mnemonic.

Jame: 2:50

Chocolate bar Taz, yeah. And then, as Trinam is AZT, which is just Tazmyspelt, so anything that has an AZT in it has antiseminal activity.

Jame: 2:58

I can get that logic. And then your fourth gen's, your Kefapeme it's got antiseminal activity also. And then when you're up to the Carbopenems, airtapenem doesn't have antiseminal activity, but Merapenem and Immapenem, silastatin and Dodapenem, which we don't use very much but does have antiseminal activity, and then as Trinam, the Monobatam on its own as well. So that's a pretty limited set of the kind of things that you would normally want to use In the UK we focus. Our main ones that we would use there I think would be Piptaz and Merapenem. Also, a lot of you know Nutripeinic sepsis protocols will use Piptaz as their broad spectrum beta-lactam because it's got antiseminal activity. And if you know the patient deforestation and you don't identify pseudomonas, you will step down to Comossoclav because it's broad spectrum but you have ensured that they don't have pseudomonas on board. First, when it comes to the quinolones, your gets antiseminal activity with the second gens, so Cyprophloxacin and Ophloxacin, and the third gen, so Levophloxacin. But you lose it when you go up to Moxie. So Moxie doesn't have pseudomonal activity but has strep, staphorius and anerobe.

Callum: 4:37

Yeah, that's the anerobe that we always forget about with Moxie Fox.

Jame: 4:41

So that's you know. It's got its own uses, but pseudomonal treatment is not one of them. So it's just Cyprophon Levo that we would use widespread in the UK and then for the aminoglycosides. This is a bit of a revolving field.

Callum: 4:56

We love that you do a whole different episode on this, I know.

Jame: 4:59

I tell you what, though, if I can briefly big up another podcast Sid Farm, the Society for ID Pharmacists, have a podcast called Breakpoints, which is all about sort of drug pharmacokinetics, pd and changes.

Callum: 5:14

Wait, can you like that sort of stuff?

Jame: 5:16

I'm passingly familiar with it.

Callum: 5:18

I can not even mention the elephant in the room, which is, which is that James is here in the north, so I continue.

Jame: 5:25

Cal, your three big aminoglycosides that are used very commonly are Gentamys and Tobramys and Anamocason. And obviously in Scotland we use a lot of Gentamys and it's in our empirical therapy, it's our gram negative backbone. There are other bits of the UK where it's used much less and I know that there's kind of reluctance for their fields to use it, based on toxicity issues mostly. So Breakpoints have recently done a mini series called Breakpoints Talks Breakpoints where they talk about updates to the CLSI and US CAST Breakpoints. So there are two separate Breakpoint setting organisations in the US Cal and, believe it or not, the FDA also sets their own Breakpoints, which is important because you can't really register a diagnostic test until you know what the FDA Breakpoints are going to be, because that's what they'll be tested against. In the EU we've only got UCAST to work with, but US CAST recently did a deep dive into the Breakpoints for pseudomonas, for amnoglycosides oh, great, okay that's good, so we don't need to record that.

Callum: 6:31

We can just point people towards that.

Jame: 6:34

But the long and the short of it is that Gentamys and the Gent pseudo Breakpoint has been dropped and it was dropped from UCAST a couple of years ago and I'm not sure who started looking into this first US CAST or UCAST but UCAST dropped it in the, I think, the 2021 Breakpoints release, as they release on the 1st of January each year.

Callum: 7:00

There was an update on the 29th of June 2023. Oh, was there? Yeah, what for?

Jame: 7:05

You'll have to go check it out yourself. Oh right, I suppose I will. But the CLSI are also dropping their Breakpoints and the reason for it is so all of these bug drug Breakpoints for the older drugs, a lot of them are historical and based on, you know, a paper here and a paper there, and US CAST went back and sort of looked at all the data they've got and when you're setting a microbiological Breakpoint, what you do is you look at the MIC distribution of the wild type population. So if you imagine that as a bell curve, your e-cough is at the sort of top end of the bell curve and your MIC is at or above that. So, above all, what you don't want is you don't want your Breakpoint by setting the wild type population, because if you've got, if you know, if you do some testing on a sample and the MIC is above that, you don't know if that is acquired resistance or if that's just a member of the wild type population. That was above your Breakpoint to begin with.

Jame: 8:11

So anyway, when they looked at the GENT Breakpoints for pseudomonas, it was basically in the middle of the wild type distribution, and so the both UCAST and CLSI have come to the conclusion that you can use gentamicin-street pseudomonas. They've dropped it, so you can use Tobra and it's probably the one that they would recommend, and you can use amicacin and I think the current status is that CLSI say that you can use amicacin for urine or is it UScast but not systemic infections. The UCAST have put breakpoints out for urine and systemic, but for systemic they've put the breakpoints in brackets, which is a sort of new code that UCAST have introduced, saying that they've rejected or passed the highlighting, because UCAST have already missed some of the Thunder1000 current status signs for black systems and they have been服. Thank you for watching. We know some countries use this for systemic infections and some don't. Just do whatever your country recommends and in the meantime this is the breakpoint that we would recommend.

Callum: 9:11

Yeah, so UCAS 13,. We're on, we're 13.1 now, I guess. So they've got breakpoints set for Tobromycin, amicacin, for pseudomonas infections are radiating from the urinary tract and then for both drugs for systemic infections they've got the breakpoints and brackets. There's a link to a document in UCAS 13.1, breakpoint tables and what that means. We won't go into too much detail. And for gentomycin they've just got insufficient evidence and I think there's a big debate there about you know where that leaves places where there are. You know, I think Scotland, where there are, there is very widespread use of gentomycin and a wealth of clinical experience in using gentomycin to treat pseudomonas infections with good clinical outcomes. So you know, just because there's no breakpoint, this is a mean country.

Jame: 9:58

I wonder if a lot of those treatments with good clinical outcomes were urinary tract infections, because you don't get great plasma levels in a lot of the kinds of places where pseudomonas is infecting and usually you would be using a second agent.

Callum: 10:16

Yeah, although we use it for pneumonia and you know, I don't know. I think there's a big debate about like obviously the you know UCAS do great work in producing scientifically robust guidelines. But sometimes, when we're particularly in something like pseudomonas, where there are such limited treatment options, it's really difficult to say there's not enough evidence. And I just thinking from a general perspective of in medicine we're constantly balancing uncertainty and risk and the risk of different things. And if you're reliant on one organisation and they say like oh, you know, can't be scientifically exact, therefore we won't give you any recommendation, I actually think that's not very helpful and it'd be more helpful to say like, okay, well, there's no enough evidence to say specifically, this is the exact right answer, but this is probably good enough or just about right or something to guide decision making, rather than just withdrawing, than dropping it.

Jame: 11:14

What I wonder is why they didn't maintain a urine break point.

Jame: 11:18

Yeah, interesting they do that with Pibmasilam they do it with Fosomison. There's precedent for saying you can only use this thing in urine. But here's the break point for that, because Gentamicin, you know, you get urine concentrations of about 100 times your plasma concentration. So if you get plasma Cmax of maybe 8 to 10, then you will get close to a thousand. And I would be willing to bet that, whatever the wild type distribution of Pseudomonas is, I don't know, I'm guessing it's not a thousand. Do you know what I mean? Yeah, and, but they dropped it and in their defence you can just swap out Tobromycin, swap, swap in Tobromycin for Gent in almost every situation and be safer. And it would be, you know, safer than it is.

Jame: 12:08

There's probably I don't know what's going to happen in Scotland, but what that's based but I think, yeah, are there any other things, any other things that you want to mention about treating Pseudomonas, particularly perhaps in the urinary tract, callum?

Callum: 12:23

No, nothing else, let's move on. I don't know what you're talking about.

Jame: 12:27

Well, maybe I'll mention a couple of things, so um, wait, do we not?

Callum: 12:32

I listened to this podcast recently and I'm sure that someone mentioned in a urine drug episode something about using antibiotics that we don't normally think work against Pseudomonas, for urinary tract infections of Pseudomonas, and I think it was Phosphamycin and Doxycycline.

Jame: 12:56

Yeah, we have mentioned this in urine drug pensions, but I thought I'd just mention it in the bug episode itself, because not everybody will have listened to it. Why not? But yes, phosphamycin. So there are issues with Phosphamycin resistance. Pseudomonas can acquire PhosA, which is the resistance mechanism, fairly easily, but Phosphamycin can be used for urinary drug infections as long as the ECOF is below 256, or 256 itself.

Callum: 13:33

So as long as the MIC is less than the ECOF, which is 256, not that the ECOF is. The ECOF doesn't change.

Jame: 13:41

Yeah sorry, ecof is always the same as long as the MIC is less than the ECOF, which is 256. So your lab needs to do some extra testing for that or else you're just using it blind, which we do sometimes, and just see how the patient does if it's the only option. And then the other thing that you can use is it's Doxycycline. So Doxy's you get a plasma Cmax of about four and the MIC for Pseudomonas is about 115. So you wouldn't be able to use it for systemic infections. But Doxycycline is 60% concentrated in the urine and you get a urine Cmax of about 300. And because your half life of Doxy's like in a 16 hours, that there means that 16 out of 24 hours you've got a Doxy urine concentration that's above the Pseudomonas MIC, the average Pseudomonas MIC. So that's one option that you've got specifically for urinary tract infections that there's papers published on it. It's not a widespread practice. Ucas don't issue any breakpoints for Doxycycline.

Callum: 14:48

It's quite hard as a laboratory to issue guidance saying use this as a potential option, and we don't really have the robust way of testing the organisms exactly.

Jame: 14:55

Yeah, but because there's, the only other oral option is quinolones and in some people that's, you know, clearly not appropriate. Then it is possible to consider it. So I consider it. Last month I was had a an old guy who was in his late 80s. He had a stone in his renal tract and it had become colonized with Pseudomonas, like the last five UTIs were all Pseudomonas, and urology were going to remove that stone in about six weeks time. So do I empirically treat infections as they arise? Do I put them on suppressive quinolone therapy or do I try putting them on suppressive doxycycline therapy, which would be much less likely to cause you know drug side effects and things like that, and in the end we opted for phosphomycin with with doxy as the backup plan. But you know that that's. You can imagine, listener, situations in which you don't want to give long-term quinolone therapy, not least because you're just. You know, in cases where the urinary tract has some sort of ni-dys infection, you'll just get a simple resistant yeah, and then you lost it.

Callum: 16:08

For any way, you did it. Yeah, yeah, yeah, no, it's yeah. Go back and listen to the urinary drug penance episode. I think that Jane talks about that quite well when you're treating Pseudomonas, what doses are you using?

Jame: 16:22

just the standard doses or no.

Callum: 16:25

So Pseudomonas, as we talked about briefly, I'm going to more detail next is it's got lots of resistance mechanisms and and some of those drugs you need to use a higher dose and what you'll often see the laboratory reporting is that you, that there'll be some drugs. So Pipera Cilante is a Bactam we reported as I, so usually we say S, I or R. S is susceptible or sensitive. By debate, r is resistant and I used to mean intermediate and now it generally means increased dose.

Jame: 16:59

That's what I stands for, so susceptible at increased dose I, so you can see you should, susceptible, dose dependent or SDD. We found that a lot of people didn't really know what that meant. So we, we, we say sensitive at higher doses, yeah, so not susceptible at higher doses, no, no, we've. We've flag in the ground there. But that then means that you know what's a higher dose. Will you cast have a list on their website of what they consider to be the standard dose and what they consider to be the higher dose?

Callum: 17:34

Yeah, it's what they're saying. The breakpoints table 13.1 is a tab on there for dosing.

Jame: 17:40

So what they're saying is use that higher dose in these infections and actually for for pseudomonas there's, they always want you to use the higher doses. So what they've done is for some drugs they have set the S breakpoint at point zero, zero one. So that means that you know that's just an arbitrarily low number. You'll never get a breakpoint that low. So that basically means that if you are below the R breakpoint so let's say for PIP ties, the R breakpoint is 16. So if you're eight, four, two, one, point five or point two five, it doesn't matter, you're still in the intermediate range.

Callum: 18:22

So, you always recommend to use it at the higher doses. So, for example, that's four point five grams IV every six hours, or ideally, you know, use a continuous infusion or something like that. It's another way of doing it. Yeah, and use it.

Jame: 18:34

So what are the other things where you are using the higher dosage?

Callum: 18:40

So most of them actually. So keftazidine, higher dose kephapine, dorapenem, imapenem, salastatin, astronam, ciprofloxidine, levofloxidine, phosphomycin, and then the rest of them are you can use a certain standard dosing, yeah. So what about if it's resistant to all the drugs that we've talked about already, which is unfortunately not that unusual for pseudomonas? It's not, you know, like most organisms, it's not unusual. To get a biogram back and actually you've got no treatment options or, in particular, no oral treatment options, is very common.

Jame: 19:16

Yeah, or limited at least. Yeah, there are a few. I mean obviously there's. There's colostin, and you cast a viscidibrate point, a bracket of breakpoint for colostin. But then the new kids on the block, the new beta latin, beta latin mesonibritters, which I sort of covered briefly in the the basics of beta latin mesonibritters episode and we talked about in the in the MDR episodes two.

Jame: 19:38

So Keftolazine with Tazobactam, keftazine with Avabactam, kefederical the Trojan horse, and then Meropen and Vaborbactam in Pemsylostatin, in Pemsylostatin with Rehla Bactam. They all have anti-seudomonal activity. Some are considered more for use with with pseudomonas than others. So I think Keftolazine and Tazobactam was developed specifically for trying to treat anti-seudomonal infections. I think I think in the UK at least, because Keftazine, avie and Kefederical the Trojan horse are available on the subscription model that NHS England has kind of brought in, then we would tend to favour using those two as opposed to the other three. I know we can get Meropen and Vaborbactam because we've used it in Nadosh, northern Firmeray South, but I've never used Immapen and Rehla Bactam or Keftolazine Tazobactam in anger, so I'm not too sure about the specifics of using those really.

Callum: 20:48

It's just great to have these new drugs, although I don't think it's unusual to see resistance to them as well. So it's maybe you know, I guess it's just it's going to continue to be, and will always be, a really problematic organ to try and treat. So we've kind of hinted at this a lot. So why is it so difficult to treat James? What are the sort of, what is it that pseudomonas is doing to make it such a pain? Why are we wanting to have a pseudomon about it?

Jame: 21:17

Well, it's because it's got loads of natural or intrinsic resistance mechanisms which you can then upregulate if it encounters an environment, in which case, you know, antibiotics are a significant kind of hindrance to its growth. So people tend to divide these mechanisms into intrinsic, adaptive and acquired. And before I go on, I should probably promote breakpoints for the second time in this podcast. I mean, if this podcast is telling you anything, it's that you should just go and subscribe to breakpoints podcast right away. But their episode 59 was all about pseudomonas resistance mechanisms and they had an expert on.

Jame: 22:04

I have to say the audio quality of the the guest that they had on was was kind of poor, so it's not one to listen to in the gym, but it certainly was very extensive. It was about an hour and a half of really detailed explanation of how bad a pseudomonas is. And there's on Twitter, which again we will link to in the show notes, there's a really good infographic about the various different resistance mechanisms that that pseudomonas has, because they're really difficult to remember and I'm not sure that there's much value in remembering all of them. But at least knowing roughly how pseudomonas does what it does is kind of worth knowing about. So, in terms of intrinsic resistance. Do you want to take this Cal?

Callum: 22:46

Yes, so I think that's something that I remember learning about at medical school. So pseudomonas it's got. The three main ones are lower outer membrane permeability, so the drugs just can't get.

Jame: 22:58

This is the outer membrane of the gram negative cell.

Callum: 23:00

Yeah, yeah, so the outer membrane. So it's just, you know a lot of drug action into the cell. You know there's going to be passive and active transport and it's just developed a way to stop that permeability. Compared to E Coli pseudomonas, the outer membrane is about 12 to 100 fold less easy to get across. The second one is E Fox pumps. So these are sort of mechanisms within the cell membrane where they specifically pump out.

Jame: 23:27

We'll talk about them below. So they get to get, to get, to get to get out.

Callum: 23:30

And then the third one is intrinsic beetle atomases, so they tend to call carry enzyme, called oxa 50 and also amp C, which you've talked about in the beetle atomases episode.

Jame: 23:42

Yeah, there's a pseudomonas, specific one that's that's kind of always on at a low level, which sort of confers resistance to. You know just about everything. Yeah, it's not active against peptidicillin, though it's interesting.

Callum: 23:54

Oh, because I was thinking when you combine peptidicillin with taseobactam and you.

Jame: 23:58

Apparently the taseobactam is for other ESBLs which they can also carry.

Callum: 24:03

Well, that's your free intrinsic lower outer membrane permeability, E Fox pumps and intrinsic beetle atomases. What about adaptive?

Jame: 24:11

Well, adaptive is the these are adapted and required blend into each other a bit. But the adaptive resistance is usually transient, which is why it's not a good idea to expose people with pseudomonal infection to antibiotics over a prolonged period of time, unless you have to like, for CF patients for example. But the mutations, they are unstable and when the stimulants is removed they tend to revert to the, to the wild type pattern, so that that will be suppression of genes, a gene expression which would kind of result in reduced susceptibility to the antimicrobial. But by far and away the most important section here is acquired resistance to the stuff that actually does treat pseudomonas. So they are. They're some which target lots and lots of different drugs and they're some that are specific to amnibic lichocytes and quinolones and Baylactam. So I'll talk about them later. Let's talk about a couple of things which pseudomonas does which can reduce susceptibility to lots of different things, and they are porins and efflux pumps. So porins first. So they, you know, as you said, the outer membrane is not very permeable. Porins sit on the outer membrane and facilitate transport of nutrients from the environment into the, into the transmembrane domain, and some antibiotics go there as well. They've got other functions. They kind of contribute to the stability of the membrane. Some of them are involved in signaling. Pseudomonas has about 26 of them, but the main one example that is important for us is OprD. So OPR is outer porin receptor and then D is just specify which one it is. And OprD can be lost by pseudomonas and that contributes to Baylactam but in particular carbapenem resistance. So if you lose OprD you become resistant to imapenem, silo statin, and then your Mero-MIC might go up. So it doesn't. Meropenem is more able to get around OprD loss than imapenem because it gets transported into other OPR receptors like OPRF, which is generally not lost with pseudomonas. It kind of has to be there a lot of the time.

Jame: 26:47

And then, talking about eflux pumps, just to give a bit of an overview of it, there are five families of eflux pumps that have that bacteria have. Now you don't need to remember all this, but it's just interesting. I thought it was interesting because I didn't really know what this, all this stuff meant. But there are two super families which are ABC, which stands for ATP binding cassette, an MFS major facilitator super family. So they're two big eflux pumps which most bacteria have. And then there are three smaller families, all of which are present in pseudomonas.

Jame: 27:20

There's mate, multidrug and toxic compound extrusion family, smr, small NDR family and RND resistance nodulation cell division family. So the RND eflux pumps are the main ones that can be upregulated, and they're actually upregulated by default in stressful situations. So the pseudomonas encounters an environment that doesn't like like an inflamed lung of a CF patient, it will just upregulate these eflux pumps by default, which means that you will get increased resistance almost by default as well. So that makes them very tricky to deal with because it's not like it's almost not related to the antibiotic that you're giving. So they'll be upregulated to a smaller amount and then you can make that worse by giving antibiotics and then the pseudomonas will respond accordingly. There are 12 eflux pumps in pseudomonas RND eflux pumps in pseudomonas but four are clinically relevant. Before I go on, I should say I've not rememeorised this.

Callum: 28:27

Yeah, you've kind of lost me a bit already, so what I need to remember is there's eflux pumps and the four clinically relevant ones are Max AB oper M, max CD oper J, max EF, oper N and Max XY, oper M. So what does Max AB mean for the first one?

Jame: 28:49

So these are the individual components of the eflux pumps. It's made up of three proteins. I should say all of this information is from a brilliant paper that came out in 2021 and frontiers and cellular and infection microbiology, which has very pretty pictures Gallum, which I think you should look at because it would explain it better. I can try. I hope that we didn't infringe copyright. It's by a guy called Langendonk Neil and Father Gill. Those are the authors and it goes through in a lot of detail all the ways that pseudomonas can acquire resistance in a few other ways that I'm not mentioning. So I'm just picking out the clinically important bits, but say, mechs A, b, operand that'll be mechs A, mechs B, proteins on top of each other and OPRM is at the top. So it's in the outer membrane, it's what throws the thing out into the environment, and mechs A will be maybe in the.

Callum: 29:53

It'll start in the cytosol and go to the trans membrane space. Yeah, you see pictures of this and they're like really complicated machines almost yeah, and mechs.

Jame: 30:00

B will start in the trans membrane space and it will take stuff from mechs A, but it will also be able to take stuff from the trans membrane domain, from the trans membrane space. So no matter where the antibiotic is, it can be picked up by the efflux pump and thrown out via OPRM into the environment. So they're very complex machines. The mechs A, b operand is constitutively active, so it's always working and it extrudes most balel atoms except imipenem and quinolones. So that's, you know, that's two out of the three. Really. Mechs C, d, oprj just works with quinolones and it's only in some mutant pseudomonas. Mechs EF operand is working on quinolones and imipenem. And then the interesting fact about that is that it's upregulated by something called mext T which also downregulates OPRD. So OPRD is the porin which confers carbapenem resistance. So you can see that it's got. You know, it's got two resistance mechanisms happening in one if it's MEXT transcription factor, and then the last one is mechs XY operand which extrudes aminoglycosides and also kephapenem, the fourth generation kephalosporin.

Callum: 31:16

So was it like? That's really complicated and even though I'm reading it off a piece of paper and talking to you about it right now and listening, I'm still struggling with this.

Jame: 31:25

So I don't think that you need to remember this stuff. I think it's worthwhile reading the front ears thing but I think the take home message from the loyal listeners that pseudomonas is terrifying and it's got loads of different resistance mechanisms and at the moment there are no drugs to treat E-flux pump mediated resistance. We've got your beta-lactamase inhibitors for beta-lactamases, but they're not a significant bit of pseudomonal resistance. It's all this stuff, this kind of porin loss and E-flux pumps. They all contribute to, you know, moderate to high level resistance against loads of different things. And then the beta-lactamases. You know you've got your amp-C which is comparing resistance, you know, to most beta-lactamases and is induced by exposure to aminopenicylins but also kephalosporins. It will just, if it goes into environment, even if you're using antibiotics which don't treat pseudomonas, it will detect that and it will kick up expression of amp-C regardless.

Callum: 32:32

Oh, is that a problematic when we're using things to combination like amoxicillin, gentamicin, that?

Jame: 32:37

we use. I think it's an I think actually it's an argument to not rely on broad spectrum beta-lactamase like kephalosporins and comoxclav as your sort of backbone, because that will drive resistance not only to in intrabacterialis but also things like pseudomonas. But I mean, it's always there anyway, so there's not a lot you can do about it. They can acquire things like ESBL and carbapenemies. They're not very, it's not as common and they don't seem to acquire it as often as, say, the intrabacterialis which are swapping them on transposons. So we often.

Callum: 33:19

We sometimes think about you know we're used to thinking about carbapenemies, production, intrabacterialis and like we'll screen for it, and we've talked about that quite a lot before, about how you do that and you know it's really important to pick up from that patient's management but also from an infection control perspective, from public health, and I think we talk about this in pseudomonas quite a lot but, as mentioned by Jane there, like it's not the most important cause of resistance, not the most common. So we have a bit of a higher threshold for sending these organisms off to reference labs to do PCR for carbapenemies or doing that locally.

Jame: 33:53

Because you know that the carbapenem resistance might be immediate. So I see myrapenem resistance I'm like.

Callum: 33:57

Well, it's much more likely to be sort of the other resistance mechanisms rather than the carbapenemies.

Jame: 34:02

Like accommodation of all three labs.

Callum: 34:03

You see something that's like if it's resistant to carbapenem and PIPTAZ and Keft has a daemonic, probably will check for PCR because it will help with your management options and infection control Sure.

Jame: 34:16

Then, when it comes to amnoglucide resistance, the main resistance mechanism would be kind of efflux and reduced permeability, but they can also have amnoglucide modifying enzymes.

Callum: 34:32

Yeah, and we've talked about them a lot in the Idiots Guide to Amnoglucide.

Jame: 34:35

Yeah, so we did yeah. Amnoglucide.

Jame: 34:41

So, they count them with a rate of between 6 and 50 percent. So maybe you know, maybe call it 25 percent. They can also do stuff like methylate 16s RNA. That's not very common, but what that then does is it protects the 16s against binding of amnoglucides. And there is something else called Fuse A1, so that codes for elongation, factor G, which is involved in translation of proteins, and that mutation will confer a four to eight fold increase in resistance against amnoglucides. And if you combine that with Mexxy OPERA-M efflux pump, then you get high level resistance against amnoglucides, and that could be universal as well. So as opposed to an AIM, which might confer resistance against one amnoglucide and not the other, you can get global resistance there.

Callum: 35:40

That's not good.

Jame: 35:41

No, and then what about?

Jame: 35:42

quinolin resistance or last group yeah so there are three main ways that you can get resistance to quinolins. One is through mutation of DNA gyrase, so either through the GYRA or B subunits, and then a risk factor for that is prolonged exposure of the patient to Cipro, for example CNF patients, and that the how they work is they just reduce binding of Ciproflux into DNA gyrase and then topoisomerase. They've got a couple of subunits called PAR-C or PAR-D and so that mutation can happen as well, and then efflux pumps is the main way, and then you can get variable resistance depending on what combination of these mutations you have. So high level resistance would be you usually need GYRA mutation and if you combine GYRA with PAR-C you get high level resistance. Low level would be GYRB, par-c, par-d or efflux pump, but on their own without anything else. And then you can get an intermediate level with the combination of any of the two, of GYRA or B, par-c or PAR-D or an eFlex pump, as long as it's not the combination GYRA with Parsi.

Callum: 37:04

So you said that usually we think about Quinolones having quite a high barrier to resistance and things like intramaturalities, but in in Pseudomonas you said it was lower. So why is that?

Jame: 37:13

Well, I think it's because it's I don't know exactly, I just but the paper that I'm basing on this, on, kind of makes the point that Pseudomonas has loads of different weapons. You know, that's five resistance mechanisms right there, and it can use them in any combination and it can acquire them, you know, fairly, fairly quickly, and maybe that's not something that the other targets of Cypherflex can necessarily do.

Callum: 37:44

I guess linking up the sort of resistance aspects with the infection control aspects is that if you've got an organism that's really great at forming biofilms and sticking in the air, built environment or on, you know, prosthetic material and it forms biofilms, you know you end up with a situation. We've got loads of organisms surviving in the presence of antibiotics, particularly within. You know a perfect example of a drain. You know it's hardly surprising that the Pseudomonas is able to to swap and talk to each other and, you know, be exposed to antibiotics and pass it along. So it kind of it kind of makes sense, isn't it?

Callum: 38:22

That is such a pain because you know it's kind of two things go together the fact that it can survive in the environment, and then you know all these and it makes sense evolutionary, before we came along using antibiotics for human. You know that bacteria are constantly fighting, competing with each other environment. So if you've got an organism, it's really good in a moist environment. Of course it's going to try and, you know, resist antibiotics. But that's a real pain for us. Yeah.

Jame: 38:48

I suppose we haven't even talked about biofilm formation, which Pseudomonas is excellent at, and we'll have to have a biofilm episode yeah, I think just to draw together some, some points on this.

Callum: 39:00

I think for me the main things that with Pseudomonas that are important is that it's the infection control aspects and water and the resistance difficult to treat in the special population of people that have a degree of compromise or prosthetic material or sort of disrupted barrier and that's the sort of the sort of free corners of this triangle of danger that Pseudomonas poses to people in hospitals and it's. It is a definite heart-sync moment when you see the culture result as a Pseudomonas there. So what?

Jame: 39:35

what stop them getting it?

Callum: 39:37

source control judicious use of of the few weapons, and and and and and you know the good laboratory work getting this susceptibility testing done right and and figuring out what you can use. But, yeah, real, real problematic stuff. And so I think, yeah, we've, we've been away from our bacteria episodes. Hopefully we'll come back to them a more consistent thing. I think we were both kind of putting off Pseudomonas because it is so complicated and jame, thanks for having done all the prep work there to to talk me through that, because that was, um, I'm struggling to get my head around there and every time I talk about it and think about it it's reminds me how complicated it is.

Jame: 40:19

Well, I did you know, before I? Um had done a deep dive into this, I didn't really realize how complex the non-bedal atomase resistance mechanisms that that Pseudomonas has where, and that's you know. Um, it'll all be in the prep notes. Um, for the, for the loyal listeners, it's still way more than I think you need, but I I think if you come out of this episode with a healthy respect, if not fear, for Pseudomonas, then we'll have done our jobs right, yeah we're maybe the hub of Pseudomonas and we're linking out to all our esteemed colleagues in in much more like established podcasts break points and the infection control ones, and we'll put, I'll, maybe we'll collect some episodes if you are, you know, really wanting to to dig your teeth into Pseudomonas because you know, as a, as an infection, an infectionologist, you, you will be dealing with this and it'll be causing problems.

Callum: 41:16

So good to know as much as you can about it.

Jame: 41:18

Yeah, I think knowing how to deal with that is um, particularly if you've got any exposure to ITU. It's time we'll spend yep. Questions, comments, suggestions why don't you send them in to idiotspodcasting at gmailcom? Have a five star review in your pocket, callum, and I would love to have it. Please drop it in your podcast player of choice. We tweet at idiots underscore pod and if you want to support the show, there is a link to do so. Uh, in the description. But until next time, I'm Callum uh, oh no what?

Jame: 41:49

what have I done? It's because I'm live and I'm looking at you, I'm like oh no, this is okay, he's so smooth.

Callum: 41:55

No, we're keeping that in.

Jame: 41:56

I'm James, goodbye, bye now that the episode's done, we hope you learn and had lots of fun. So go forth and treat people with some of what you now know.