you all right so for their third category I'm going to talk about plasma membrane injury and there's just a couple here to mention in fact when we buy antibiotics to use in the lab for our antibiotic lab we only have polymyxin B that's the only option I've been able to find there's another one called lipopeptide that's good for gram positives but these are fairly unusual I mean it makes sense that they would be hard to develop because you also have plasma membrane so finding drugs that are only bother hurting the bacteria and not cause problems for you or touch the neosporin it actually contains several different antibiotics but one of them is polymyxin B the fourth category are nucleic acid synthesis inhibitors there's some important drugs here rifampin or Ripa myosin that's the same thing they inhibit the synthesis of mRNA same hibbett transcription and then the quinolones and the fluoroquinolones inhibit DNA gyrase so they inhibit DNA replication so ciprofloxacin is really famous people call it cipro when people there was a how many years back it was that they were somebody was mailing Congress anthrax spores and in envelopes and so they would give the people who were exposed to pros a prophylactic to prevent them from getting sick then ciprofloxacin is used very commonly for urinary tract infections it's fairly non-toxic resistance can develop rapidly so that's the downside of it but it is useful in a lot of different situations so Ripa myosin and ciprofloxacin those are the two big categories of nucleic acids and business inhibitors and then the last group are the competitive inhibitors of metabolism and we've talked about these before because we talked about competitive inhibition so this is actually our second run through this but we're thinking about it from another angle now which is how these particular drugs how they make good antibiotics and so so far might bind to enzymes that are used in a pathway to make folic acid and ultimately nucleotides so if it blocks early in the pathway this I should say that so far oh my block early in the pathway because sulfonamide look just like para amino benzoic acid so they look so similar to the normal molecule that that this enzyme works on that they can bind and then prevent parrot I mean of benzoic acid from from working and then there's trimethoprim trimethoprim inhibits the the it basically looks a lot like da hydrofluoric acid so it competitively inhibited inhibits another enzyme in the pathway but they both work to prevent the bacteria making folic acid and then preventing it from making nucleotides so that's how those work so you can see the last three mechanisms don't take very much time to go through at all and I'm going to end on this slide this is the one of my favorite cartoons Robin is telling Batman that he thinks he needs antibiotics for it's cold and famines like you silly it's a virus and I'm hoping that we can just spend a moment thinking about what this means people always frequently not always but very common people to go and ask doctors for antibiotics I have they're runny nose it'll make me feel better the last time I got sick I got antibiotics and that's when I got better so first thing to know is that cold typically lasts seven to fourteen days and if you go in after a week and you feel like you're not getting better and you get given antibiotics and then you start to feel better a few days later the reality is you would have anyway because that's just how long it takes for your immune system to come back virus typically so people often mistake correlation which as they began taking the antibiotics and about the time they got better with causation which would mean that antibiotics cause causes them to get better and in the case that viruses antibiotics do not cause people to get better the other thing is thinking about this particular cartoon is you know why don't antibiotics help with a cold well you know viruses that think about what they are they're they're capsid with some DNA or RNA inside and sometimes they have an envelope you know they don't have a cell wall they don't make their own protein so they don't undergo protein synthesis they don't have plasma brains right they don't make DNA or RNA and they don't make folic acid so those were our big categories so none of the mechanisms when you understand how antibiotics work it starts to make sense why antibiotics don't work for Kol's so that is why we make you understand this at least once in this class because someday you'll have patients and they're going to want to have antibiotics because they have a cold and you'll now know what to say to them right that antibiotics don't work for colds and the reason why is viruses don't have the structures that bacteria have that caused antibiotics to be effective when did we give someone who has a viral infection at naina biotic we would do it if they had a pre-existing health condition let's say they had a virus and they were at risk of developing a bacterial pneumonia it might make sense to give them the antibiotic in advance to prevent that bacterial pneumonia because their health was frail already so there are cases where we do give antibiotics prophylactically but in general you know that your common person you go this comes in with a cold and wants antibiotics you know they really should be told though and it's a lot of work to tell them no it's a lot faster to just give them a prescription than it is to explain why the answer is no and then have them complain and everything else so by my I'm sending it was supportive thoughts when you work with patients down the road be strong and make sure that people don't get antibiotics when they're gonna cause more harm than good and in our next lecture we're going to talk about how the presence of antibiotics in the environment to cause this tremendous problem of antibiotic resistance and are basically taking away these amazing tools that we said at the very beginning of this lecture you know reduced infant mortality rates by a tremendous amount and increase our life expectancy rates as well