Antibiotic treatment

Since the discovery of penicillin by Alexander Fleming in 1928, antibiotics have saved millions of lives, in both human and veterinary medicine. They’re an invaluable tool used against many diseases and constantly evolving, but whilst antibiotics are incredibly useful and invaluable, they can pose a significant challenge when used in guinea pig medicine.

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Antibiotics are important medicines used to treat infections caused by bacteria. They work by slowing the growth of or killing the bacteria. There are many types of antibiotics. Some of the more common ones include:

• Penicillins, eg penicillin G, amoxicillin.
• Cephalosporins, eg cefaclor, cefadroxil, cefalexin.
• Tetracyclines, eg tetracycline, doxycycline.
• Aminoglycosides, eg gentamicin, however these are contraindicated and dangerous to use in guinea pigs.
• Clindamycin.
• Sulphonamide and trimethoprim, eg so-trimoxazole.
• Metronidazole and tinidazole.
• Quinolones, eg ciprofloxacin, enrofloxacin, levofloxacin, norfloxacin.

Guinea pigs are hindgut fermenters and rely on microbial digestion. This means that they have literally millions of ‘friendly’ bacteria within their digestive system.

Antibiotics are by their very nature designed to ‘kill’ bacteria, and some types of antibiotics are not selective about what bacteria they invade and kill off. This means that certain types (notably aminoglycosides) must never be given to guinea pigs as they are highly likely to kill off the ‘friendly’ bacteria within their digestive system, leading to potentially and often fatal diarrhea.

Other antibiotics, eg penicillins and clindamycin may be given to guinea pigs via injection rather than orally to minimize the risk of digestive upsets. Nutritional support should be given to guinea pigs undergoing antibiotic treatment, in the form of probiotics, for a minimum of 10 days afterwards. Your veterinarian will discuss the risks to benefit ratio with you to help decide if this is the best option for your guinea pig.

Your veterinarian can guide you on what antibiotics are suitable for your guinea pig. It’s worth noting that no antibiotics are licensed for use in guinea pigs, so all use of these is classed as being given ‘off label’. This means there is no alternative drug that has a license for that species or for that particular condition, so your veterinarian is prescribing the ‘off label’ drug based on evidence of its use in other species for similar conditions. This is common practice in guinea pig medicine since so few drugs are licensed for guinea pigs. Often, the results of a culture and sensitivity test will indicate a particular antibiotic is needed, invariably this will not be licensed for guinea pigs. Your veterinarian should always discuss this with you first.

Adverse reactions can occur to any medication and to any animal. There are always risk involved with any drug, and no one drug can ever be 100% safe in all situations. Adverse reactions can occur, but by selecting appropriate antibiotics that are generally safe to use in guinea pigs giving the correct dose for the correct amount of time, and if possible, using injectable antibiotics, the risks are minimized. It’s important to watch closely for any side-effects and stay in contact with your veterinarian. If you are concerned you should speak to your veterinarian immediately.

Adverse reactions are likely to be related to the digestive tract and will include liquid diarrhea, collapse and potentially death in the most serious of reactions. Other reactions may include lethargy, increased heart rate and GI stasis. If you’re concerned about your guinea pig, you must speak to your veterinarian immediately.

Antibiotics have a very useful and important role in the veterinary treatment of guinea pigs, and without the option of using them, we wouldn’t be able to treat many conditions very successfully.

Antibiotics don’t work against viral infections and, as in human medicine, we must not overuse antibiotics. Antibiotic resistance is becoming more of a problem in human and veterinary medicine.

Antibiotics are useful in cases of bacterial infection, eg abscesses, respiratory infection, urinary infections, and to prevent infection in wounds which are at risk of becoming infected.

Antibiotics work according to the type of bacteria; some have a broad spectrum (effective against several bacteria), and others have a narrow spectrum (may only work against one or two types of bacteria).

Ideally, a culture and sensitivity test should be carried out before starting antibiotic treatment. The test involves taking a sample of any discharge from the affected area, eg a wound, bodily fluid or from an orifice, although this isn’t always possible. The sample is then sent away to a laboratory so they can ‘grow’ the bacteria and decipher which is the best antibiotic to use.

Antibiotic resistance is fast becoming a serious problem in human medicine. The same antibiotics are used in human medicine that are used in animals.

Bacteria are living organisms and can adapt and find ways to survive the effects of an antibiotic. They become ‘antibiotic resistant’, meaning that the antibiotic no longer works against that strain of bacteria. This happens the more often we use an antibiotic. Potentially a situation can arise whereby a bacterium is resistant to all known antibiotics.

By using antibiotics less often, and correctly, we can slow down the development of resistance, and antibiotics should never be used unnecessarily. It’s imperative to always use the correctly prescribed antibiotics, at the correct dosage, and for the correct length of time.