Post by samantha on Mar 29, 2014 16:10:35 GMT -5
Hi,
As I mentioned in the introductions thread, I'm a student doing an honours project. I saw the pages Carl had written on antibiotic treatments on the American Aquarium products page, and was thoroughly impressed with his in-depth knowledge of the topic. I'll outline the project for you, and then ask my question. Hopefully this makes things clear
I'm working with Dr. Louis Gosselin as my supervisor. The bulk of his work is on marine invertebrate mortality during the juvenile phase. During this period, most species of marine invertebrates undergo a significant bottleneck event, where often 90% or more of the juveniles die before they reach adulthood. For a variety of reasons, the ecology of the juveniles is different than that of the adults, and so the factors that cause juvenile mortality are different than the factors which cause adult mortality. However, the bulk of research done on marine invertebrates is often done on the adult forms of various species. This means that relatively little is understood about what causes the massive mortality event at the beginning of the juvenile phase. Louis' research revolves around figuring out why so many juveniles die before they reach adulthood, often within days of metamorphosis and settlement.
My project attempts to figure out if juvenile mortality (of a variety of representative species found off the coast of B.C.) is caused in part by bacterial infection. The experimental design will involve taking juveniles collected from the field, splitting them into antibiotic and control groups, and soaking them in an antibiotic bath (or control bath) for about an hour per day once (or twice) a day for three days. They will then be taken out of the antibiotic/control baths (in their enclosures or on settlement plates) and replaced into the field - i.e. hanging off of docks or attached to a rock surface. At the end of each day, mortality will be recorded in each group. At the end of the experiment, hopefully some difference in survivorship is seen between the control and treatment groups.
The species that will be used are Mytilus trossulus (Mussels), Serpula columbiana (tubeworms), and Balanus glandula (barnacles).
My question is about what, in your opinion, would be appropriate antibiotics to use. I was leaning towards Oxytetracycline and a mixture of Trimethoprim / Sulfamethoxazole based on a few studies I had seen with live adult marine invertebrates, where these had seemed to work alright and produce some results (and most importantly had not killed the animals). I'm looking for a mix of broad spectrum antibiotics which will hopefully act on a wide range of potentially pathogenic bacteria (there is also incredibly little information in this field, as pathogens of juveniles are rarely the same as pathogens of adults). The only problem is that many of the studies I have looked at are incredibly vague and nonspecific in their methods, with some basic information left out such as how the antibiotcs were applied. Were they fed? Were they soaked? What concentrations were used and for how long? There seems to be no answers. I then came across the page Carl had written on marine antibiotic usage, which mentioned that oxytetracycline chelates strongly with dissolved calcium, and furthermore would probably not work in a saltwater pH range. I'm currently refocusing my efforts on Chloramphenicol, and Kanamycin sulfate combined with either oxytetracycline or nitrofurazone. Do those seem appropriate?
Another issue that has become apparent is that it may be difficult to get these antibiotics to stay within the organisms. Anything water soluble can be put into a soak, but once the juveniles are replaced in the field, these will have the tendency of rapidly dissolving into the ocean. Lipid soluble antibiotics may work best, but then it becomes difficult to create a soak. Alcohol can be used to dissolve lipid soluble antibiotics in, but even small amounts will kill the invertebrates. I have seen one study where a small amount of dissolve NaOH was used to aid the solubility of an antibiotic, and that did not seem to kill the marine invertebrates. That may be a potential route to use lipid soluble antibiotics.
I would greatly appreciate any input you have on this topic. Anything successfully used on marine fish will likely be appropriate, and any advice or insight you have after so many years of experience would be greatly appreciated. References to papers, journals, or any other relevant literature would also be great. This project has been a lot of work, but I hope it will be well worth it.
Thank you for taking the time to read such a long post! It means a lot to me.
Sam
As I mentioned in the introductions thread, I'm a student doing an honours project. I saw the pages Carl had written on antibiotic treatments on the American Aquarium products page, and was thoroughly impressed with his in-depth knowledge of the topic. I'll outline the project for you, and then ask my question. Hopefully this makes things clear
I'm working with Dr. Louis Gosselin as my supervisor. The bulk of his work is on marine invertebrate mortality during the juvenile phase. During this period, most species of marine invertebrates undergo a significant bottleneck event, where often 90% or more of the juveniles die before they reach adulthood. For a variety of reasons, the ecology of the juveniles is different than that of the adults, and so the factors that cause juvenile mortality are different than the factors which cause adult mortality. However, the bulk of research done on marine invertebrates is often done on the adult forms of various species. This means that relatively little is understood about what causes the massive mortality event at the beginning of the juvenile phase. Louis' research revolves around figuring out why so many juveniles die before they reach adulthood, often within days of metamorphosis and settlement.
My project attempts to figure out if juvenile mortality (of a variety of representative species found off the coast of B.C.) is caused in part by bacterial infection. The experimental design will involve taking juveniles collected from the field, splitting them into antibiotic and control groups, and soaking them in an antibiotic bath (or control bath) for about an hour per day once (or twice) a day for three days. They will then be taken out of the antibiotic/control baths (in their enclosures or on settlement plates) and replaced into the field - i.e. hanging off of docks or attached to a rock surface. At the end of each day, mortality will be recorded in each group. At the end of the experiment, hopefully some difference in survivorship is seen between the control and treatment groups.
The species that will be used are Mytilus trossulus (Mussels), Serpula columbiana (tubeworms), and Balanus glandula (barnacles).
My question is about what, in your opinion, would be appropriate antibiotics to use. I was leaning towards Oxytetracycline and a mixture of Trimethoprim / Sulfamethoxazole based on a few studies I had seen with live adult marine invertebrates, where these had seemed to work alright and produce some results (and most importantly had not killed the animals). I'm looking for a mix of broad spectrum antibiotics which will hopefully act on a wide range of potentially pathogenic bacteria (there is also incredibly little information in this field, as pathogens of juveniles are rarely the same as pathogens of adults). The only problem is that many of the studies I have looked at are incredibly vague and nonspecific in their methods, with some basic information left out such as how the antibiotcs were applied. Were they fed? Were they soaked? What concentrations were used and for how long? There seems to be no answers. I then came across the page Carl had written on marine antibiotic usage, which mentioned that oxytetracycline chelates strongly with dissolved calcium, and furthermore would probably not work in a saltwater pH range. I'm currently refocusing my efforts on Chloramphenicol, and Kanamycin sulfate combined with either oxytetracycline or nitrofurazone. Do those seem appropriate?
Another issue that has become apparent is that it may be difficult to get these antibiotics to stay within the organisms. Anything water soluble can be put into a soak, but once the juveniles are replaced in the field, these will have the tendency of rapidly dissolving into the ocean. Lipid soluble antibiotics may work best, but then it becomes difficult to create a soak. Alcohol can be used to dissolve lipid soluble antibiotics in, but even small amounts will kill the invertebrates. I have seen one study where a small amount of dissolve NaOH was used to aid the solubility of an antibiotic, and that did not seem to kill the marine invertebrates. That may be a potential route to use lipid soluble antibiotics.
I would greatly appreciate any input you have on this topic. Anything successfully used on marine fish will likely be appropriate, and any advice or insight you have after so many years of experience would be greatly appreciated. References to papers, journals, or any other relevant literature would also be great. This project has been a lot of work, but I hope it will be well worth it.
Thank you for taking the time to read such a long post! It means a lot to me.
Sam