Why why do cuts from coral, oyster shells and fish spines always seem to get infected? Other than not getting cut in the first place, are there ways of preventing infection? - M.
Corals are hard, sharp and brittle, which means they create irregular wounds with lots of crevices and injured tissue with poor bloodflow where bacteria flourish.
Coral scrapes also deposit calcium dust in the skin, which causes inflammation and pain. Like most marine animals, including fish, corals are covered in slime. Surprisingly, slime is actually mostly sugar with some proteins and bacteria mixed in. Even white blood cells and antibodies find it hard to cope with and bacteria gain a strong foothold.
Two tips for coral wound care: use a safety-pin to pluck out embedded bits of coral; and use hydrogen peroxide, diluted with water, to apply to the fresh wound. The resulting foam will help lift out coral dust. Combine that with an immediate washout with soap and running water. You may still get infected, but it's more likely to be minor.
Opposite to corals, oyster shells inflict scalpel-like wounds with no debris. So why do they get infected? One reason could be because they are so good at filtering and concentrating bacteria. Shellfish can contain one million bacteria in each gram of oyster meat.
With that many bacteria in a wound the goal is to immediately reduce their number.
As soon as possible wash the wound with soap, then spread the wound open (painful but necessary) and flush it out with running water - right to the bottom of the cut - for a few minutes.
Your aim is just to reduce the numbers of bacteria to levels your immune system can cope with.
Fish spines, similar to cat bites and rose thorns, cause puncture wounds where bacteria are pushed deep into the skin where they can't be flushed out by bleeding or tap water irrigation, and where they grow in the ideal dark, moist, and oxygen-poor conditions. See a doctor if you think a spine has broken off in the wound. For all these infections, if you develop an abscess, antibiotics will often be useless, and an old-fashioned incision and drainage by your doctor may be required.