Just as some people are prone to bladder infections, so too are some dogs. It is not uncommon for women with bladder infections, but without symptoms, to go untreated. Even without antibiotics, these women often experience very good long-term outcomes. It made researchers at the University of Wisconsin wonder: would withholding treatment also produce good results for symptom-free dogs with bladder infections? Their research begins to answer that question.
The study of canine bladder infections
The study, reported in the July, 2014 Journal of the American Veterinary Medical Association looked at 101 overtly healthy (symptom-free) female dogs screened for bladder infections.
The nine dogs with infection were then monitored for symptoms—no antibiotics were administered—over a three-month time period. At the end of the three months, eight of the dogs were reexamined.
At this three-month visit:
Do canine bladder infections require treatment?
While I find this study interesting, I am reluctant to draw any hard and fast conclusions based on the small number of dogs evaluated and the relatively short period of time over which they were followed. The results certainly lend support to the notion that, when it comes to dogs with bladder infections and no symptoms, leaving the antibiotics on the shelf is worthy of consideration.
My own clinical experience is consistent with the results cited in this study. I often test urine as part of routine health screening, particularly in older dogs.
When I discover a bladder infection in an asymptomatic patient, before I determine whether or not to treat with antibiotics, I consider several factors including:
Here are some examples of how my decision would be made:
Simply monitoring rather than treating dogs with asymptomatic bladder infections is certainly worthy of consideration. Such a decision warrants significant discussion between veterinarian and client. If antibiotics are withheld, careful monitoring for symptoms and urine testing are vital components of effective, ongoing care.
Questions to ask your veterinarian:
Tell us below:
Would you feel comfortable withholding antibiotics to treat your dog’s bladder infection if there were no symptoms?
If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.
1. Wan, SY, FA Hartmann, MK Jooss, and KR Viviano. "Prevalence and Clinical Outcome of Subclinical Bacteriuria in Female Dogs." Journal of the American Veterinary Medical Association (2014). National Center for Biotechnology Information. U.S. National Library of Medicine. Web. 05 Sept. 2014.
Friday, September 5, 2014
Urine culture is the “gold standard” for diagnosis of UTI. Indications to perform urine culture include visualization of bacteria during urine sediment examination, evidence of pyuria, dilute urine ( Amoxicillin and ampicillin are bactericidal and relatively nontoxic, with a spectrum of antibacterial activity greater than that of penicillin G. They have excellent activity against staphylococci, streptococci, enterococci, and Proteus, and may achieve urinary concentrations high enough to be effective against E coli and Klebsiella. Pseudomonas and Enterobacter are resistant. Amoxicillin is more bioavailable in dogs and cats (better absorbed from the GI tract) than ampicillin , hence the lower dosage. Absorption of ampicillin is also affected by feeding, so therapeutic success may be easier to achieve with amoxicillin . As penicillins, they are weak acids with a low volume of distribution, so they do not achieve therapeutic concentrations in prostatic fluid.
Amoxicillin -clavulanic acid has an increased spectrum of activity against gram-negative bacteria because of the presence of clavulanic acid. Clavulanic acid irreversibly binds to β-lactamases, allowing the amoxicillin fraction to interact with the bacterial pathogen. This combination usually has excellent bactericidal activity against β-lactamase–producing staphylococci, E coli, and Klebsiella. Pseudomonas and Enterobacter remain resistant. However, clavulanic acid undergoes some hepatic metabolism and excretion, so much of the antimicrobial activity in the bladder may be due to the high concentrations of amoxicillin achieved in urine. Thus, despite an unfavorable susceptibility report for amoxicillin , clinically amoxicillin alone may be as effective as amoxicillin -clavulanic acid to treat UTIs.
Cefadroxil and cephalexin are first-generation cephalosporins. Cefadroxil is a veterinary-labeled suspension product, whereas cephalexin is available in both human and veterinary formulations as tablets, paste, or suspension products. Like the penicillins, they are bactericidal, acidic drugs with a low volume of distribution and are relatively nontoxic. Vomiting and other GI signs may occur in dogs and cats treated with cephalosporins. Cephalosporins have greater stability to β-lactamases than penicillins, so they have greater activity against staphylococci and gram-negative bacteria. They have excellent activity against Staphylococcus spp, Streptococcus spp, E coli, Proteus, and Klebsiella. Pseudomonas, enterococci, and Enterobacter are resistant.
Cefovecin is an injectable, third-generation cephalosporin approved for treatment of dogs with a UTI due to E coli or Proteus. In cats, it is only approved for skin infections but may be used in an extra-label manner for UTIs. With SC dosing, therapeutic concentrations are achieved for 14 days, making this an attractive treatment choice for fractious animals.
Cefpodoxime is an oral, third-generation cephalosporin approved for use in dogs for skin infections (wounds and abscesses), but it is used extra-label for treatment of canine UTI. Cefpodoxime has a relatively long half-life in dogs, so it is dosed once daily.
Ceftiofur is an injectable cephalosporin approved for respiratory disease in horses, swine, and cattle and for treatment of canine UTI caused by E coli and Proteus. Ceftiofur has pharmacokinetic properties very different from those of other cephalosporins. After injection, ceftiofur is immediately metabolized to desfuroylceftiofur, which has different antimicrobial activity than the parent compound. Desfuroylceftiofur has equivalent activity to ceftiofur against E coli (MIC 4 mcg/mL) but is much less active against Staphylococcus spp and has variable activity against Proteus (MIC 0.5–16 mcg/mL). Because of the instability of desfuroylceftiofur, microbiology services use a ceftiofur disk when performing susceptibility testing, so a false expectation of therapeutic efficacy may result for some pathogens. Pseudomonas, enterococci, and Enterobacter spp are resistant to ceftiofur and desfuroylceftiofur. Ceftiofur is associated with a duration- and dose-related thrombocytopenia and anemia in dogs, which would not be expected with the recommended dosage regimen.
Chloramphenicol has a high volume of distribution, and high tissue concentrations can be achieved, including in the prostate of male dogs and cats. It is active against a wide range of gram-positive and many gram-negative bacteria, against which it is usually bacteriostatic. Chloramphenicol is typically active against enterococci, staphylococci, streptococci, E coli, Klebsiella, and Proteus. Pseudomonas are resistant. North American isolates of methicillin-resistant Staphylococcus aureus and Staphylococcus pseudintermedius are typically susceptible. Well known for causing idiosyncratic (non-dose-dependent) anemia in people and dose-dependent bone marrow suppression in animals, its use in both human and veterinary medicine is increasing because of resistance to other antimicrobial drugs.
Enrofloxacin, orbifloxacin, and marbofloxacin are all fluoroquinolones approved to treat UTIs in dogs although all are used in cats, only some are approved for this use. Pradofloxacin is only approved for skin infections in cats in North America, but it is approved for treatment of UTI in dogs in Europe and is used to treat feline UTI. The fluoroquinolones are bactericidal, amphoteric drugs. They possess acidic and basic properties but are very lipid soluble at physiologic pH (pH 6–8) and thus have a high volume of distribution. All fluoroquinolones usually have excellent activity against staphylococci and gram-negative bacteria, but they may have variable activity against streptococci and enterococci. The therapeutic advantages of these drugs are their gram-negative antimicrobial activity and high degree of lipid solubility. They are the only orally administered antimicrobials effective against Pseudomonas. Therefore, fluoroquinolones should be reserved for UTIs that involve gram-negative bacteria, especially Pseudomonas, and for UTIs in intact male dogs and cats because of their excellent penetration into the prostate gland and activity in abscesses. They are concentration-dependent killers with a long postadministration effect, so once daily, high-dose therapy for a relatively short duration of treatment is effective.
Fluoroquinolones should be avoided for chronic, low-dose therapy, because this encourages emergence of resistant bacteria that are cross-resistant to other antimicrobial drugs as well. Cases that involve Pseudomonas should be carefully investigated for underlying pathology, which must corrected if at all possible. Once Pseudomonas spp become resistant to the fluoroquinolones, there are no other convenient therapeutic options.
Gentamicin and the other aminoglycosides are very large, polar (water-soluble) molecules, so they have a low volume of distribution and do not penetrate the blood-prostate barrier. They are not absorbed orally and must be given by SC, IM, or IV injection. The aminoglycosides have a similar spectrum of activity to that of the fluoroquinolones, but their use for UTI is limited because of the necessity of parenteral injections and the risk of toxicity with anything but short-term use. Like the fluoroquinolones, the aminoglycosides are concentration dependent, bactericidal killers with a long postadministration effect, so once-daily therapy of short duration is effective and minimizes the risk of nephrotoxicity. They can be considered for in-hospital or outpatient treatment of UTI due to fluoroquinolone-resistant pathogens however, the importance of identifying and correcting underlying pathology must be emphasized.
Nitrofurantoin is a human product available as tablets, capsules, and a pediatric suspension. It is not commonly used in veterinary medicine. It is typically used only for treatment of UTI in people, because it has a very low volume of distribution, and therapeutic concentrations are attained only in urine. It is considered a carcinogen, so it is banned for use in food-producing animals, but its use in small animals is increasing with the rising rates of antimicrobial resistance to veterinary antimicrobials. Nitrofurantoin is used for infections caused by E coli, enterococci, staphylococci, Klebsiella spp, and Enterobacter spp. It is increasingly indicated for treatment of UTIs caused by multidrug-resistant bacteria, which are otherwise difficult to treat using conventional veterinary antimicrobial agents. The pharmacokinetics and adverse effect profile of nitrofurantoin have not been investigated in dogs, cats, or horses, and the need for multiple daily dosing makes it inconvenient for owners.
Tetracyclines are bacteriostatic, amphoteric drugs with a high volume of distribution. Tetracyclines are broad-spectrum antimicrobials, but because of plasmid-mediated resistance, susceptibility is variable in staphylococci, enterococci, Enterobacter, E coli, Klebsiella, and Proteus. In most tissues, Pseudomonas spp are resistant. However, the tetracyclines are excreted unchanged in urine, so high urinary concentrations may result in therapeutic efficacy. Doxycycline is a very lipid-soluble tetracycline better tolerated in cats and reaches therapeutic concentrations in the prostate, so it may be useful for some UTIs. Doxycycline may also be effective to treat methicillin-resistant staphylococcal UTIs. If capsules are administered, it is critical to have the animal drink afterward to ensure passage into the stomach. If capsules remain in the esophagus, severe local necrosis with subsequent esophageal stricture can occur.
Trimethoprim -sulfonamides (TMP-sulfas) are combinations of two very different drugs that act synergistically on different steps in the bacterial folic acid pathway. Trimethoprim is a bacteriostatic, basic drug with a high volume of distribution and a short elimination half-life, whereas the sulfonamides are bacteriostatic, acidic drugs with a medium volume of distribution and long half-lives (ranging from 6 to >24 hr). These drugs are formulated in a 1:5 ratio of TMP to sulfa, although the optimal bactericidal concentration is a ratio of 1:20 TMP:sulfa. Microbiology services use the 1:20 ratio in susceptibility testing however, the widely varying pharmacokinetic properties of this drug combination make it difficult to determine a therapeutic regimen that achieves the 1:20 ratio at the infection site. Although the combination does penetrate the blood-prostate barrier, sulfa drugs are ineffective in purulent material because of freely available para-aminobenzoic acid from dead neutrophils. The combination of TMP-sulfa is synergistic and bactericidal against staphylococci, streptococci, E coli, and Proteus. Activity against enterococci and Klebsiella is variable, and Pseudomonas is resistant. TMP-sulfas are associated with a number of adverse effects, and chronic low-dose therapy may result in bone marrow suppression and keratoconjunctivitis sicca in dogs.
Bringing pets into our families provides us with companionship, affection and love, but this relationship also requires rules for cohabitating. The first rule all dogs and cats need to understand when they live with humans is where they are allowed to “do their business”. When they get that one wrong, life becomes unpleasant very quickly for everyone! However, there can be situations when inappropriate urination is not a sign that your pet needs more training, but a symptom that your pet is sick.
The urinary system is comprised of the kidneys, ureters, bladder and urethra. The kidneys are a pair of small organs located on either side of an animal’s lumbar vertebrae. All of the normal metabolic processes necessary for life keep the body continuously active metabolizing food, utilizing nutrients and breaking down cells. These reactions result in by-products. Some by-products are reabsorbed into other uses in the body while others are simply waste and need to be removed. The most important route for waste elimination is through the urinary system. The kidneys filter the blood so that useful substances circulate back into the body where they can be used and waste materials are excreted as urine. The kidneys also maintain a healthy fluid balance by excreting excess water, regulating pH by eliminating unbalanced ions, and even support red blood cell production by producing hormones. Once all of these materials are filtered out of the blood stream by the kidneys, they travel down the ureters (tubes) to the bladder. The bladder holds all of these waste products until the animal is ready to urinate. When the cat or dog urinates, the urine is release from the bladder and travels down the urethra where it is excreted.
Urinary tract infections (UTIs) occur when bacteria is introduced and travels up the urethra. The most common type of UTI is called a “lower” urinary tract infection because the bacteria and inflammation is confined to just the urethra. Lower UTIs are the #1 reason cats are brought to the vet. However, the infection can spread up to the bladder, ureters and even the kidneys. The further up the tract that the infection goes the more serious it is.
Symptoms of Urinary Tract Infections
Normal dog and cat urine is on the slightly acidic side of neutral and should have a pH of around 6.0 to 7.0. When the pH of urine gets too high or too low, crystals occur. For example, when the pH is too high (alkaline) struvite crystals can form, which is the most common type in dogs and cats. Other debris found in urine includes minerals and proteins. When too much debris is present, it can form stones called uroliths. Crystals and uroliths irritate the urinary tract making it susceptible to bacterial infection. Larger uroliths can make urination difficult or block the urethra, requiring surgery. Researchers still do not have a solid understanding of exactly the hows & whys crystals and stones are formed, but believe they can be effected by a number of factors including diet, disease, intestinal absorption, medications, endocrine abnormalities and water intake. Stress from changes to a pet’s routine or environment is another common trigger for pets predisposed to UTIs. UTIs are typically a chronic affliction that needs long term management to prevent them from reoccurring. Cats in particular can suffer from chronic UTIs because their uroliths form as grains of sand instead of large stones, which makes them especially irritating to the lining of the urinary tract. Cats also can develop a condition where they are prone to inflammation which leads to reoccurring UTI problems.
If you see that your pet is having a very difficult time urinating and appears to be in distress you need to call the veterinarian immediately because they could be blocked. A blocked urethra is extremely painful and life-threatening so it must be treated as an emergency. Less serious cases still require a trip to the vet as soon as your animal can be seen. Your vet will want to do a series of laboratory tests on the urine so they may ask you to bring in a clean urine sample, but that is not always possible. Urine can also be collected via cystocentesis where the vet draws urine out of the bladder using a needle and syringe to collect an uncontaminated sample. (Cystocentesis is a very common procedure since it is difficult to get a dog or cat to pee in a cup!) The vet will usually prescribe antibiotics and pain medications to treat the infection. Extreme cases may require surgical removal of stones or blockages can be flushed back up the urethra where the stones can be dissolved. As mentioned, pets with a predisposition to UTIs will require continued vigilance to prevent reoccurring infections. Commercial veterinary diets are available to reduce urolith formation and help dissolve existing stones and crystals.
Because there are so many variables involved in urinary health, many natural supplements exist to help address the problem from different angles.
Humans with UTIs are often told to drink cranberry juice. Cranberry juice is a delicious and convenient option for people, but contains way too much sugar for it to be a good option for our pets. The main nutrient in cranberry juice that helps fight UTIs is called D-Mannose. D-Mannose is a non-metabolizable sugar that does not affect blood sugar or pH so it is safe for diabetics. When consumed, D-Mannose becomes part of the urine where it can collect bad bacteria out of the bladder. The bacteria binds to the D-Mannose instead of the lining of the urinary tract and is safely eliminated. It works particularly well on e coli, which is the most common bacteria to cause UTIs.
Methionine is an essential amino acid that helps support kidney health by chelating heavy metals and regulating the formation of ammonia. When it is metabolized, the resulting product is sulfuric acid, which helps to acidify urine. It is especially helpful for helping to regulate urine pH when the pH needs to come down. Be sure to talk to your vet before using Methionine because if the animal’s urine pH is already too low it would not be beneficial.
Glucosamine is most commonly used as a source of glycosaminoglycans (GAGs), which are the building blocks for connective tissue like cartilage in our joints. The N-Acetyl form of glucosamine specifically targets mucus membranes like those linking the urinary and digestive tracts. Supplying the body with extra N-Acetyl-Glucosamine helps keep the lining of the urinary tract healthy and strong, protecting it from irritating crystals and debris in the urine.
Infection occurs when bad bacteria gets into an already raw urinary tract lining. Providing your pet with healthy bacteria – probiotics – will help crowd out the pathogenic strains. Probiotics also produce short chain fatty acids which discourage the growth of bad bacteria. The most common treatment for a UTI is antibiotics. Antibiotic use will wipe out populations of healthy bacteria so it is great to reintroduce healthy strains to keep the system balanced.
Corn silk is a natural diuretic, which means it helps to increase water elimination from the body. Drinking lots of fluids and peeing them out is the best way to flush the urinary system of bacteria, crystals and debris. It is rich in soothing polysaccharides to help ease pain and inflammation.
The roots of this herb are rich in mucilage which is a viscous substance that helps to coat mucus membranes, protecting the delicate tissue. UTIs are very painful so the added mucilage sooths irritation and inflammation. Marshmallow root was originally used by the ancient Egyptians to make a sweet treat, but the recipe has since evolved to replace the marshmallow with gelatin to give them the squishy consistency so there is no actual marshmallow root or herb in the type of marshmallow you toast on a campfire.
MSM supports a healthy inflammatory response which again is very helpful while dealing with painful UTIs. Research supports MSM’s ability to help ease pain associated with arthritis and new evidence is emerging that it is helpful for bladder infections (aka cystitis).
After canine surgery, it is relatively common for the wound to become infected. However, it is not clear how often this occurs, what increases the risk, and how much it affects treatment costs. A new study looks for answers.
Share on Pinterest A new study takes a fresh look at infections following canine surgery.
Although scientists have invested a great deal of time in understanding surgical site infections (SSI) in humans, they know much less about these infections in animals.
Researchers have a good idea about which factors are likely to increase the risk of postsurgical infection in humans, but, again, the picture is not so clear in animals.
Recently, a group of veterinary scientists set out to understand how often surgical wounds in dogs become infected. They also asked what factors make it more likely and investigated the costs associated with these infections.
The authors of the study, which features in BMJ Vet Record, explain why this work is important:
“These infections are responsible for an increase in morbidity, mortality, prolonged hospital stay, increased costs, and a negative impact on the emotional state of the owner.”
Although only a few studies have investigated the prevalence of SSI in dogs, the authors of the research study note that current estimates range from 3% to 6.6%.
They explain that some of the previous results might have been open to errors. For instance, some studies could not differentiate between inflammation and infection, while others relied on diagnoses by people lacking training.
To investigate, the researchers used data from a veterinary teaching hospital. During the study, 184 male and female dogs of all ages underwent soft tissue surgery.
Alongside details on the dogs’ health following surgery, the researchers also collated information about each animal’s age, sex, reproductive status, underlying conditions, and breed.
They also looked at surgical factors, including the type of surgical scrub that the surgeons used, how many people participated in the procedure, whether undergraduates took part, the type of surgery, how long it took, and how the team sealed the wound.
Assessments of the animals took place in the hospital 5 days and 10 days after the procedure. The researchers also followed up at the 30 day mark with a telephone call.
Of the 184 procedures, SSI occurred in 16 cases, which equates to 8.7%. The age, sex, and breed of the dog did not influence the risk of SSI. However, as hoped, the authors did identify certain factors that were associated with an increased risk.
For instance, they found that steroidal anti-inflammatory drugs increased the risk of infection. According to the authors, this association — which is new to veterinary science — might be because steroidal anti-inflammatory drugs cause immunosuppression, making infection more likely.
The authors also found that SSI risk was greater for dogs with higher-than-normal blood glucose levels (hyperglycemia) before the operation. Although researchers have not shown this link in animals before, hyperglycemia is a known risk factor for SSI in humans.
According to the researchers, studies have shown that hyperglycemia reduces the ability of white blood cells to pass through the walls of capillaries, preventing them from reaching the site of infection.
Risk also increased for the dogs that underwent operations that lasted longer than 1 hour. The medical community also considers a long surgery time to be a risk factor for human SSI.
Similarly, animals that needed a urinary catheter had a higher risk of infection. Again, this is a new finding for veterinary science, which, the authors believe, the known link between catheters and urinary tract infections (UTIs) might explain. The authors note:
“ [T]he microorganisms responsible for the development of UTIs could easily be involved in the colonization of surgical wounds.”
The scientists also showed that if animals did not receive an Elizabethan collar (also called a dog cone) after surgery, the risk of infection increased. The authors write that this “could be explained by the existence of [a] certain degree of self-mutilation in veterinary patients when the healing surgical wound is not protected.”
Bacteria from the dog’s mouth can pass freely to the surgical site and cause an infection.
As for the cost of SSI, the researchers found that although presurgical and surgical costs did not increase in infected dogs, postsurgical costs rose by 142.2%. The authors outline the reason for the increased expense:
“This increase is mainly due to the need for a greater number of follow-up appointments, the cost of additional treatment, as well as the performance of culture and antibiotic sensitivity tests.”
In this study, the researchers used what they refer to as an “active surveillance system.” In other words, trained personnel checked the surgical wound at regular intervals.
The authors believe that this system helps explain why they reported a higher rate of infections than earlier studies that did not use such a system.
The authors conclude that “avoiding surgical infections is vital to preserve the patient’s overall health status and to avoid unnecessary expenses. In fact, the implementation of surveillance and control systems for SSIs could reduce the economic costs and improve the service offered to patient and owner.”
Despite a plausible and well-demonstrated theoretical mechanism by which cranberry might prevent UTI, clinical trial evidence in humans has failed to find a consistent, meaningful benefit in most populations. Due to the heterogeneity of human clinical trials, it is unclear which patient populations, if any, might benefit or how significant any preventive effect of cranberry supplements might be.
There is minimal research evidence in small-animal veterinary patients. The studies done so far do not show any evidence of efficacy for cranberry products in the prevention of UTI in dogs. These studies also do not show any apparent harm from such products, though the risks seen in humans may only be evident with long-term use. At this point, further research is warranted, but any recommendation for the use of cranberry supplements should be accompanied by a clear disclosure there is not yet convincing evidence they have any meaningful benefit.
Brennen McKenzie, MA, MSc, VMD, cVMA, discovered evidence-based veterinary medicine after attending the University of Pennsylvania School of Veterinary Medicine and working as a small animal general practice veterinarian. He has served as president of the Evidence-Based Veterinary Medicine Association and reaches out to the public through his SkeptVet blog, the Science-Based Medicine blog, and more. He is certified in medical acupuncture for veterinarians. Columnists’ opinions do not necessarily reflect those of Veterinary Practice News.