What is Penicillin?
Penicillin was the first naturally occurring antibiotic discovered against gram-positive and negative bacteria. It was first discovered by a laboratory technician known as Alexandra Fleming in 1928. This was an accidental discovery as he had left cultured staphylococcus bacteria in an open petri dish.
On returning from a two-week vacation he found blue green mound/fungi known as Penicillium notatum had contaminated the culture. He noted a clear ring around the mould indicating lysis of the staphylococcus bacteria and had stopped growing. Since then a lot of work has gone into improving penicillin and coming up with various antibiotics in the penicillin class for general public use.
Penicillin works by causing the bursting or lysis of bacteria cells. It breaks the bonds that link proteins called petidoglycans together. Petidiglycans are a form of mesh work which strengthen the cell wall that surrounds the plasma membranes of bacteria. It also helps maintain the structure and prevents foreign materials both fluids and particles enter the bacterial cell.
During reproduction of bacteria, the cell wall forms holes which allow the multiplication of cells. After cell division, petidoglycans usually fill in these holes and strengthen the cell walls of the newly formed bacterial cells. Penicillin works by breaking the bonds that link the petidoglycans together preventing the holes from closing.
This allows water which is of higher concentration than the fluid within the cells to rush in bursting the bacterial cells open leading to cell death.
Penicillin is among the most widely used antibiotic worldwide both in human and veterinary medicine. It has low allergic rates though its misuse can lead to resistance of bacteria to the drug. Penicillin can be given intravenously (penicillin G), oral (penicillin V) and intramuscular use (procaine penicillin and benzathine penicillin).
Can you give a dog Penicillin?
Yes, penicillin is usually given to dogs and is among the first line of antibiotics to be prescribed. It’s used to treat infections caused by a variety of gram positive and gram negative bacteria i.e broad spectrum antibiotics. Such bacteria include: Streptococci, Staphylococci, Clostridium, Neisseria, and Listeria genera.
Penicillin in dogs is usually administered through injection and orally on rare occasions. Prescription of penicillin should be done after thorough physical examination and laboratory tests having been conducted.
Laboratory samples may be collected e.g. blood, aspirates from abscesses, stool, cerebral spinal fluid, sputum, vaginal swabs etc. for culture to identify the causative bacteria and to check if the isolated bacterium is susceptible to penicillin. It is discouraged to give your dog human forms of penicillin as the dosage and concentration vary in dogs.
It should, however, be used under the guidance and prescription of a veterinarian with forms specifically formulated for veterinary use. Penicillin is also prescribed after surgical operations to prevent secondary bacterial infections.
Penicillin can be given through deep intramuscular injection or intravenously. Oral forms are either given in tablet or capsule form or through syrup on an empty stomach. When giving penicillin to your pet be sure to finish the prescribed dose to avoid cases of bacterial resistance and to ensure the infection has cleared up. Overdosing should also be avoided. It is also important to check if your dog is allergic to penicillin to avoid the event of an anaphylactic shock.
What can Penicillin be used for with Dogs?
Penicillin in dogs is used to treat infections caused by gram positive and gram negative bacteria susceptible to penicillin. It is also prescribed postoperatively to prevent secondary bacterial infection.
The Gram stain is used in laboratory tests to classify bacteria into two broad categories i.e. gram positive and gram negative. The gram stain tests which bacteria peptidoglycans will take up the purple-colored gram stain even after washing in the decolorization stage when observed under a microscope.
Gram-positive bacteria return a positive test to the gram stain by taking up the purple color. Gram-negative bacteria, on the other hand, have a thin petidoglycan layer which is usually degraded by alcohol making it permeable during the decolorization stage. This makes it not take up the purple crystal violet stain but alternatively retain the pink-red color of the counterstain (surfranin).
Common bacteria susceptible to penicillin include:
- Clostridium: these are spore-forming, rod shaped gram-positive bacteria commonly found in soil and the intestinal tract in animals. These include:
- Clostridium botulinum– It causes a disease called botulism following ingestion of contaminated food and also found in wounds.
- Clostridium perfringens: This is a foodborne disease as a result of ingesting contaminated meat.
- Clostridium tetani: Causes tetanus.
- Streptococci: Isolated in the respiratory system, urinary tract, skin, and the intestines. It includes:
- agalactiae – Causes mastitis
- anginosus – Found in abcess in the brain and liver
- pneumonia – Causes pneumonia
- Staphylococci: Gram-positive bacteria isolated on the skin, intestines and bone and muscle infections.
- Neisseria – Gram-positive bacteria. Neisseria meningitides causes meningitis.
- Listeria- Gram-positive bacteria that grow well in refrigerated temperatures. Listeria monocytogenes causes food poisoning.
When to use Penicillin on Dogs
Common conditions treated with penicillin include:
- Bacterial skin infections: These are usually caused by staphylococcus and streptococcus bacteria affecting the top layers of the skin. It is among the most common cases documented in veterinary clinics. It can occur together with flea or mite infestation and allergies. Signs of infection include:
- Reddening of the skin
- Loss of hair
- Licking or biting the area
It is commonly found in pitbulls, bulldogs, American Cocker Spaniel, French bulldogs etc.
Treatment is usually given at an outpatient basis and recovery occurs within a week or so.
- Respiratory infections: These infections are caused by streptococcus and staphylococcus bacteria. They affect the throat, nasal cavity, bronchi, and the trachea. It commonly affects dogs found in shelters, kennels and crowded places. These infections are contagious and easily transmissible to other dogs.
Common signs of disease include;
- Mild fever
- Off food
- Nasal and eye discharge
- Nasal congestion
- In serious cases, the dog may experience difficulty breathing
Treatment should be instituted as soon as possible to prevent worsening of the condition leading to serious complications such as death.
- Urinary tract infections: This is painful in dogs caused by E.coli and staphylococcus bacteria. They travel up the urethral opening into the urethra from feces or a contaminated environment. Signs of infection include:
- Painful urination
- Blood in urine
- Licking the genital area
- Dribbling urine
- Frequent urination
- Gastrointestinal infections: These are usually caused by E.coli and staphylococcus bacteria. Occur as a result of ingestion of contaminated food. Common signs of infection include:
- Going off food
What are the side effects of Penicillin
Penicillin is a relatively safe drug to use due to its long margin of safety. Side effects of penicillin are the body’s immune reaction to the drug. It may also be the result of an allergic reaction. Allergic reactions usually cut across all classes of penicillin including amoxicillin, ampicillin, carbenicillin among others.
Resistance to penicillin is also a possible side effect of the drug. Other cases occur as a result of taking other medications concurrently with penicillin or in the case of an overdose or misuse of the drug.
Common side effects include:
- Injection site reaction e.g. redness, pain, swelling
- Black or hairy tongue
- Muscle pain
- Facial swelling
- Loss of appetite
- Difficulty breathing
- Painful joints
- Yeast infection due to disruption of the balance of normal flora in the body. Penicillin VK alters the intestinal flora in the gut leading to the proliferation of Clostridium difficile causing inflammation of the colon.
- Rash on the ventral aspect of the body
Intravenous penicillin can also cause serious side effects in dogs such as:
- cardiac arrest
- transient loss of vision
At high doses, it may lead to:
- Metabolic acidosis
- Decrease or increase in blood calcium levels
- Increase in nitrogen blood levels
Drug to drug reactions can also occur when penicillin is administered concurrently with other drugs. These drugs affect the absorption, metabolism, distribution, and excretion. Other drugs affect the concentration of the drug at the site of action. Drugs that should not be taken together with penicillin include:
- Tetracyclines i.e. doxycycline, oxytetracyclines
Misuse of penicillin can lead to resistance of bacteria to the drug. This causes such bacteria to survive and reproduce in the presence of antibiotics. This deems infections caused by drug-resistant bacteria hard to treat. Such bacteria adapt quickly and mutate to survive the effects of antibiotics. This can be through:
- Penicillinase: This is an enzyme produced by bacteria that enable them to breakdown penicillin. This can be spread during cell division of bacteria (conjugation) through their DNA, therefore, reproducing more drug-resistant bacteria.
- Susceptible bacteria can also alter the structure of their cell wall such that penicillin does not bind to the petidoglycan therefore not causing lysis of the microorganisms. This is usually through mutation of their DNA in an effort to adapt, survive and propagate other bacteria.
- Other forms of drug-resistant bacteria contain pumps within their cells that enable them to export penicillin’s out of the cell preventing cell death.
One of the most common drug-resistant bacteria is methicillin-resistant Staphylococcus aureus (MRSA) which is resistant to benzyl penicillin.
Antibiotic resistance can be prevented by:
- Completing the entire dose of your prescription even when the dog is back to his or her normal self.
- Avoiding misuse, overuse or taking antibiotics unnecessarily e.g. using antibiotics to treat viral infections or on infections whose causative bacteria is not susceptible or sensitive to penicillin. Before the prescription of any antibiotics, laboratory tests should be carried out to ensure that the causative bacterium is sensitive to the prescribed antibiotics.
- Practicing good hygiene practices such s disinfection to prevent transmission of drug-resistant bacteria.
Penicillin’s should be taken with care in pregnant and lactating bitches as they may affect the growing fetuses and puppies respectively.
How much Penicillin to give a dog?
Penicillin is commonly known as penicillin G, Pen G or procaine penicillin. It is usually administered as an injectable (through the muscle or vein), oral tablet or in liquid form as a syrup.
Oral formulations are rarely prescribed and should be given on an empty stomach as food prevents absorption of the drug through the gut. Syrups are usually formulated by mixing the penicillin powder with water. It should thereafter be refrigerated and disposed of after 14 days. Oral tablets, on the other hand, should be kept away from bright light.
Dosage for penicillin is given according to the weight of the dog. Amoxicillin should be given at a dosage rate of 5mg per pound every 12 hours, ampicillin at a rate of 10mg per lb every 12 hours, penicillin G of 150 000 units at a rate of 1 cc per 20 lbs every 48 hrs subcutaneously and procaine penicillin 300 000 units at a rate of 1ml per 30 lbs subcutaneously.
Penicillin should be used under the guidance of a licensed veterinarian after a thorough physical examination and laboratory tests. This helps proper prescription preventing an overdose or misuse which may lead to adverse side effects and drug resistance. He will also guide on whether to give dispensed oral tablets either before or after meals or without food to prevent malabsorption of the drug. In the case of a missed dose, the guardian should be keen to give the next dose.
When is it not safe to use Penicillin?
Penicillin though a safe drug due to its wide margin of safety can be contraindicated in certain situations. This includes:
- If the dog is allergic to all classes of penicillin such as amoxicillin (Amoxil), ampicillin (Omnipen, Principen), carbenicillin (Geocillin), dicloxacillin (Dycill, Dynapen), or oxacillin (Bactocill). This also includes allergic reactions to cephalosporins.
- Dogs with kidney and liver diseases should be given alternative medication or given under careful guidance of a veterinarian as such conditions can interfere with metabolism (liver) and excretion (kidney) of penicillin’s. This also includes dogs with bleeding and blood clotting disorders as this can worsen the condition. Long term use of penicillin’s often leads to bleeding disorders as it slows down clotting time by causing a decrease in the production of blood platelets by causing bone marrow depression. It is also contraindicated in dogs with asthma or one with a compromised respiratory system.
- Penicillin’s are also contraindicated in dogs under hormonal treatment as prevents absorption of the hormones in the body.
- Penicillin’s should not be administered in lactating bitches. Penicillin is usually passed in milk which may affect the puppies leading to toxicity.
- Penicillin’s should be given at the correct dose as an overdose can lead to an imbalance of normal flora in the gut leading to yeast infection.
- Penicillin G should not be administered intravenously, subcutaneously or intraperitoneally. This leads to death.
- Penicillin’s should not be indicated for the treatment of viral infections or to bacterial infections of which the causative agent is not susceptible to penicillin. This may lead to drug resistance.
- Human prescription of penicillin should also not be administered to dogs as it may lead to an overdose or adverse side effects.
- Concurrent use of penicillin’s with aspirin, warfarin etc. is contraindicated.
Natural Antibiotic Alternatives for Dogs
Commercially produced antibiotics are all derived from nature. Some of the natural alternatives to antibiotics include:
- Honey: It contains hydrogen peroxide which is a potent antiseptic as it hydrolyzes bacteria. It also forms a protective layer on wounds which helps to maintain a moist environment which fastens wound healing. It also inhibits the growth of over 60 types of bacteria.
- Oregano oil. This contains potent anti-inflammatory and antimicrobial properties which help to kill bacteria. It is usually given orally, topically and can be diffused. It should be diluted or given together with coconut oil.
- Colloidal silver: This is a suspension that has long been used to combat bacterial infections. It fights fungal, viral and bacterial infection by penetrating the cells and killing pathogens. It also boosts immunity to fight viral infections and repairs tissue damage in both wounds and burns.
- Plantain: It contains both antibacterial and anti-inflammatory properties. Allantoin found in plantain helps in wound healing and stimulates the growth of new tissue cells. Plantain also helps to relieve inflammation, especially in insect and snake bites.
- Tumeric is usually mixed together with manuka honey. They both contain strong antibacterial and anti-inflammatory properties. It stimulates wound healing and treats skin infections. It is also a potent antioxidant and also helps to relieve gastrointestinal problems when taken orally.
- Calendula (Calendula officinalis): Has antibacterial and antifungal properties. It helps to boost immunity as well as stimulate the liver. It has also been found to be beneficial in wound healing, and an effective disinfectant.
- Herbs such as garlic, ginger, and rosemary also contain powerful antibacterial properties.
- Essential oils such as lavender, sweet marjoram etc. can be used topically to treat wounds and skin infections as they have antibacterial properties.
Penicillin is among the most commonly used antibiotics in small animals. It works by interfering with the structure of the bacterial cell wall by breaking the bonds that link the petidoglycans together. This allows an influx of water of high concentration into the cell leading to cell lysis.
Penicillin’s are broad spectrum antibiotics that act against both gram-positive and gram negative bacteria such as staphylococcus, streptococcus, Listeria, clostridium, and Neisseria. These bacteria cause skin infections, gastrointestinal infection, meningitis respiratory infection, urinary tract infections among others.
Before treatment, a licensed veterinarian should carry out thorough physical examination and laboratory test to confirm if the causative bacterium is sensitive to penicillin. This helps to avoid misuse or overuse of the drug which can lead to drug resistance. It also allows the veterinarian to dispense the correct dosage depending on the weight of the dog. The pet owner should ensure to follow through with the medication until the last dose.
Penicillin is contraindicated in dogs that are allergic to any class of penicillin. They should also be avoided in nursing bitches, those on hormonal treatment, dogs with bleeding disorders, kidney and liver failure/ infection as it interferes with its excretion and metabolism.
- Medical News Today. How do penicillins work? https://www.medicalnewstoday.com/articles/216798.php
- Penicillin. https://www.petmd.com/pet-medication/penicillin
- Can Dogs and Cats be Allergic to Penicillin? https://www.canidae.com/blog/2015/02/can-dogs-and-cats-be-allergic-to-penicillin/
- Natural Canine Antibiotics. https://www.natural-dog-health-remedies.com/canine-antibiotics.html