Bacterial infection in dogs

Methicillin Resistant Staphylococcus aureus infections of dogs

Veterinarians have been lucky over the last decade or so in not having to deal with methicillin resistant staphylocccus aureus (MRSA) infections very often. It is likely that this situation will change over the next few years as MRSA infections are being reported more commonly in pets. In most cases these infections are thought to be contracted by the pet due to association with an infected human but it also appears that pets can be a reservoir for the infection in households and much more rarely a source of infection for previously uninfected humans. There are two forms of MRSA that are recognized in people, community acquired MRSA and hospital acquired MRSA. In general, hospital acquired MRSA is much worse and can lead to organ failure and death fairly rapidly, despite treatment, in some patients. So far, the pet cases that have been reported appear to be the community acquired form of MRSA. Cats infected with MRSA may have difficult to treat abscesses or lymph node swelling not explained by other diagnoses. Dogs have more of a tendency to have inapparent infections affecting the nasal passages but can have severe abscesses or other signs of an infectious process. At the present time the main thing to remember about MRSA and pets is that they are usually infected by a family member who has the disease but that it may be difficult to clear it from the household without treating pets who are infected. So if you or someone you have close contact with is diagnosed with MRSA and it is hard to eliminate, you may want to be sure that a pet is not harboring the Staph bacteria and keeping the infection going in the household. It is also important to keep in mind that most Staph infections in dogs and cats are caused by Staphococcus intermedius, so just the word "staph" should not set off alarm bells immediately. Dr Mike Richards, DVM 9/02/2006

Resistant Staph infection in Bull Mastiff

Question: Dr. Richards-- Any advice on how to treat a stubborn staph infection on a dog's head? A friend's young bullmastiff has had problems for wks that 3 rounds of ax haven't been able to clear up. She is looking into diet changes. Thanks. Shanna Answer: Shanna- It is helpful to try to obtain a culture of the bacteria causing the problem. If this is successful then it is possible to test that culture against various antibiotics to see which ones work best to kill the particular bacteria involved. There are scattered reports of methicillin resistant staph infections in dogs (these are the really resistant infections sometimes seen in humans) and if this is the case it can be quite difficult to treat the infection and it may be best if the dog is treated by a board certified dermatologist. Sometimes really resistant infections turn out not to be bacterial in origin. It is important to rule out Demodectic mange (if it hasn't been), ringworm (not likely but worth eliminating in really resistant cases). Skin biopsy can be helpful in ruling out other problems like fungal infections other than ringworm, pitysporum infections, mycobacterium infections, skin cancers, immune mediated diseases and other uncommon causes of skin disease. We just got done treating a patient for a really persistent skin infection which took two years of continuous antibiotic use to resolve. This dog had secondary Psuedomonas infection on top of a staph infection and it was just a really difficult infection to resolve. We did biopsies twice thinking that something else had to be going on but apparently not as she did finally get over this infection last month. Sometimes you just have to be really persistent to get these kinds of problems under control. Mike Richards, DVM 8/5/2005

Bacteria developing immunity to antibiotics

Question: Would you classify the possibility of a dog becoming immune to an antibiotic as being low, moderate or high, if the same drug (Cephalexin) is administered on a fairly routine basis -- for chronic dermatitis? Most underlying (possible) disorders have been ruled out for the cause of the superficial rashes, but my question is relative to immunity factors, not causes for the skin problem. FYI: Dose (for a giant breed dog): 2000 mg. daily, BID. Are there tests available to determine if dog have developed antibodies for certain drugs? Answer: This is probably a minor point, but the dog doesn't become immune to the antibiotic, the bacteria that reside on the dog become resistant to the antibiotic. The probability of this is low for cephalexin, for most of the organisms that it is used for. The only way to test for resistance that I know of is to grow the bacteria on a culture plate and then do sensitivity testing, in which antibiotics are applied to the culture plate to see which antibiotics inhibit bacterial growth or kill the bacteria. There may be dogs that actually develop antibodies against some antibiotics but I am not aware of this problem occurring.

Mike Richards, DVM 1/3/2001

Mixed bacterial infection and Cushing's

Question: Thanks, Dr. Richards. My lab had an ultrasound of her bladder on Monday -- everything looked normal so they do not think she has stones or a tumor. Also her kidney blood chemistries came back normal as well -- I'm guessing this means she doesn't have a kidney infection, especially since the bleeding has stopped and she's not running a fever. She is retaining urine; I have been manually expressing it several times a day and giving her bethanechol as well. The specialists (neurologist and orthopedist) do think there is a neurologic cause for this, but not disc disease or spinal tumors, since the X-rays came back normal. However, she does seem to be getting weaker, and she is still losing hair (appetite is great, though!). Since she has been on thyroid hormone for over 3 months now, I'm guessing that the lack of improvement suggests she is not hypothyroid -- but I guess we need to retest to be sure. Her urinalyses and blood work consistently rule out diabetes, so I think at this point Cushing's is a good bet. So it's time to test for Cushing's. Quick question, I hope -- will Anipryl interfere with any of the tests for Cushing's (ACTH, LDDS or HDDS)? She has been on it for about 5 weeks now, 30 mg./day. Also, another question -- the day we collected urine samples for the last culture -- the one that turned up the staph infection, we also sent a sample to a pathologist to look for evidence of epithelial cells that would suggest TCC (there were none). The pathologist's report stated that he saw numerous "rod-shaped bacteria". Doesn't this suggest that there is something other than staph present -- I did some research so I know staphylococcus (the official diagnosis on the culture)is round or ovoid-shaped. Are E.coli or Pseudomonas rod-shaped? Or are we dealing with something new? BTW -- I read somewhere that typical adult dogs (not older ones) sleep 13 hours a day. Mine however, sleep much more (close to 18 hours/day). Thanks. Carol

Answer: Carol- Staphylococcus bacteria are coccoid (sort of spherical) and both E. coli and Pseudomonas are both rod shaped. So it is very likely that this is a mixed bacterial infection, which is not unusual. Selegiline (Anipryl Rx) usually does not change the blood test results in dogs with Cushing's disease for a long time, if ever, even when it really seems to be working -- which is one of the reasons that some endocrinologists and veterinarians don't think that it works. So I don't think it will interfere with the testing. Mike Richards, DVM 9/19/2000

Rusty color under eyes and around mouth in Dalmatian

Question: Dr. Mike, My 8 1/2 year old Dalmatian "Mugs" recently started to "rust". His eyes are weepy and rusty under the eye area as well as around his mouth. Of course every where he licks becomes rusty from his saliva. He hasn't experienced any environmental changes which might have triggered an allergic reaction. Earlier this summer he was treated with antibiotic drops for an eye infection. His eyes were very mattery at the time of treatment but not "rusty". He has never experienced this type of rusty condition. I'd like to know if parasites or mites of some type could be the cause. He is otherwise in healthy condition. He does take daily doses of soloxine for his thyroid condition. Please reply with any info you may have. Thank you, Kathleen Answer: Kathleen- The bronze or rust color in the tears and around the mouth are due to bacteria breaking down porphyrins, which are part of the heme molecule that carries the iron in the blood stream. This can happen in tears or in saliva. For this reason, tetracyclines will often help to control the staining. This is probably not the best use of an antibiotic, though. When there is discoloration around the mouth, it is important to look for dental problems, for infections in the folds around the mouth and for disorders that cause generalized itchiness and lead to secondary bacterial infections. Allergies are very common in dalmatians. Most commonly these are inhaled allergies (atopy) but dalmatians also get food allergies and they seem to be more prone to this than many breeds. For discoloration around the eyes, it is best to look for changes in the anatomy of the eyelids that sometimes occur with age and allow tear flow over the eyelids, disorders that irritate the eyes, such as glaucoma, allergies and uveitis and to also check for tear deficiency which can actually cause periods of increased tearing early in the disorder. Since allergies appear on both of these lists, they have to be strongly considered. I do not know how common allergies are in Alaska, though. Sometimes, resistance to bacterial infection drops with hypothyroidism. If it has been awhile since thyroxine levels have been checked, to be sure they are in the normal range with the supplement, it might be a good idea to check on those levels. Hope this helps some. Mike Richards, DVM 10/18/2000

Nocardia organisms

Question: Mike -

What do you know of Nocardia? It seems reasonably prevalent in the Midwest Bird dog world, although that's no more than a vague impression. The 1998 Brittany National Champion, who is also a dual, just contracted it. I had planned to breed to him on Bonnie's next cycle in January. Bob Answer: Bob- There are three species of Nocardia organisms that can cause disease in dogs but as far as I know, the organisms can all cause any of the forms of the disease and respond to similar treatment. Nocardiosis is acquired by contamination of a wound with the organism, by inhaling it from the soil or by eating dirt contaminated with the organism. It is most common in the South and Southwest, although it can occur in other areas. Due to the relationship with inhaling or ingesting contaminated soil it may be more common in hunting dogs. When nocardiosis occurs as a contaminated wound, the usual history is a wound that has been unresponsive to antibiotics and has resulted in a draining tract or a non-healing ulcer of the skin. Nocardiosis can also occur as a severe infection of the chest cavity (pyothorax). This usuallyresults in the product of pus that can be aspirated from the chest and examined. It is supposed to look like cream of tomato soup. There are also some dogs in which the infection is spread throughout the body (disseminated nocardiosis), which causes respiratory signs, fevers, weigh loss, neurological disease and exudates from the nose or eyes. This makes it look a lot like distemper virus infection or a generalized fungal infection such as coccidioidomycosis. It is possible to culture the bacteria or to identify it in smears from the wound or of the pus in the chest. Sometimes it is necessary to use special stains (acid-fast) in order to see Nocardia organisms in tissue samples. This can be a really hard infection to control. When pyothorax is present, it may be necessary to surgically implant a drainage tube into the chest, requiring hospitalization and monitoring. If there are internal abscesses they may have to be opened and drained through surgical exploration. Antibiotics are usually given for a month beyond the time any clinical signs of the disease are present. Sulfa and sulfa/trimethoprim antibiotics are the most commonly successful but using antibiotics based on culture and sensitivity results is probably best. I do not think that nocardiosis is considered to be contagious from dog to dog. This is a serious illness and not all dogs recover from it, even with appropriate and intensive care. I have not read of effects on reproductive capability but it seem logical that there may be some if a dog has the disseminated form or high fevers from the other forms of nocardiosis. Mike Richards, DVM 9/23/2000

Escherichia coli (E. coli)

Question: Dr. Mike I have a 9 year old Lhaso Apsa named Duffy. My vet has told me that he has E-coli as well as bladder stones (crystals). Duffy was previously on Primor antibiotics for 7 days but his urine shows that the inflamation is still present. He is now on orbifloxacin for the next 7 days. After that, the vet plans to put him on 14 more days of another type of antibiotic. He said Duffy needs to stay on antibiotics until the crystals either shrink naturally (he is on u/d Hill's Diet) or the stones in the bladder will have to be removed surgically. He also wants to run a test for cushing since the blood work has come back with a problem on one of the test cells (for liver). After reading your web site I am still confused as to what causes E.coli and is this contagious to other animals in our house? We have three dogs. Can they catch E.coli from Duffy (either thru drinking out of the same water or some other way)? How long should a person wait to see if the stones will shrink or go away on their own before the decision is make to remove surgically? I am anxious to do everything to help the E.coli go away. Also, do you know of a web site for canine nutrition or any books that address feeding dogs with heart and kidney problems? My Missy (who is in heart failure and also has kidney problems) is a very fussy eater who prefers people food. She is a 7 lb toy poodle....and I am getting very frustrated trying to find food that she will eat and at the same time will be good for her. Thanks for all your help. Your web site is the best! Sharon

Answer: Sharon- To answer your questions in reverse order, there is a web site at which you may obtain individualized nutritional advice (for a fee) for pets with special dietary needs. The site is run by a Dr. Remillard, who is a veterinary nutritional specialist. The site is www.petdiets.com Bladder infections most commonly involve bacteria that are already normal residents on (or in) the dog or cat. The most common infectious agent is Escherichia coli (E. coli) which is present in almost half of urinary tract infections in dogs and cats. This bacteria is a normal inhabitant of the gastrointestinal tract but it does not belong in the urinary tract. It is very good at invading the urinary tract if given any opportunity at all, though. So any fecal contamination of the vulva or prepuce can lead to an infection. Due to anatomy, this is more common in females than in males (infection occurs more often). It is very hard to clear up a bacterial infection when there are persistent crystals or stones in the bladder, since these serve as a place for acteria to hide, as well as irritating the bladder and urethra, making it easier for the bacteria to invade tissues. There are no hard and fast guidelines for how long dietary control of stones should be attempted prior to giving up. The answer partly depends on whether the type of stone is known with reasonable certainty. I usually give up after about 3 weeks in dogs in which we have never recovered or removed a stone and had it analyzed. If we have had stone analysis from a previous problem and the stones were struvite, the only ones that can be dissolved well through dietary means, then I would be willing to try longer, perhaps six to eight weeks. Another factor is the amount of pain the patient is experiencing. I think that surgical removal of stones is the appropriate treatment when the patient is in a great deal of discomfort and it is not alleviated very rapidly through dietary treatment. Often, when dietary control is working, the patient will be much more comfortable within 3 to 5 days. If we do not see an increase in comfort rapidly, we usually advise an earlier surgery. Hope this helps. Mike Richards, DVM 7/28/2000

E. coli and death of a pet

Question: Dr. Mike - I appreciate your quick response to my E-mail and I do feel somewhat better about the events of that entire week and the end result. I am considering looking into a pet grieving support group as I am having such a hard time coming to terms with the loss of Buster. I could accept his passing easier if I hadn't had to make the decision to put him to sleep. There will always be that nagging feeling that I did it too soon and maybe his treatment was mismanaged. At the end, his back hind quarters had begun to quiver as well as his gum area. Is this indicative of anything? I do have a couple of questions regarding E-coli. Does E-coli not respond to anti-biotics or just not to the anti-biotics that Buster received? Also, am I clear that you believe that there could have been an underlying problem in the intestines which precipitated the out of control growth of E-coli? Since Buster never ran a fever, is E-coli not considered an infection? We live on 40 acres and have cows. Buster spent 95% of his time in the house and never allowed out of the fenced yard unless accompanied by myself or my husband. He loved to sneak some bites of cow dung. Do you think this is how he got it? How long does it take for E-coli to grow and become severe? Buster was out in the field about 2 weeks before he got sick. It was a nice day and we were on the 4-wheeler and the dogs were following along. They got hot and swam in the creek for a bit and drank the water. Could this have been the culprit? Also, I didn't mention that the Clinic kept mentioning torsion and ileus. What is your opinion of these two conditions? Where can I find the article in the AVMA concerning E-coli? Again, I thank you for your time and your patience in trying to help me better understand what happened to Buster.

Kelley

Answer: Kelley- It is very common for pet owners to have lingering questions after the death of a pet, and especially after having to make the difficult decision to allow euthanasia. It would be a really good idea to find people who you can talk with who are going through the same emotional process. Pet loss support groups are a good way to find this kind of help. I have had the same feelings about pets when I have made the decision to euthanize, even though I deal with this issue very frequently. It is much harder to put emotions aside when it comes to your own friends and family. E. coli is a normal inhabitant of the digestive tract of pets, or at least it is found frequently when it does not appear to be the cause of any problem. However, certain strains of E. coli do consistently cause problems and other strains can cause problems when the conditions are right. Cattle sometimes carry the strains of E. coli that are more dangerous and they do sometimes shed these organisms in their feces. So they would be a possible source of an E. coli infection. However, E. coli infections are pretty common in dogs and most of them don't have a source of cow chips, so there are obviously other transmission methods, as well. When E. coli is pathogenic (a disease causing strain) there is a strong tendency for it to be resistant to most antibiotics. Usually the fluoroquinolones (Baytril Rx, Dicural Rx, others) are a good choice, as are trimethoprim-sulfas and amoxicillin-clavulinic acid combinations. An antibiotic sensitivity test may indicate that other antibiotics should work, too. It is important to remember that antibiotics need help in order to kill bacteria. It is very difficult for antibiotics to kill infectious agents without the proper conditions being present in the body for the antibiotic to get to the area of the infection and without the help of the patient's immune system. Bacterial infections sometimes occur in situations in which the body is not functioning well enough to aid in its own defense. In the intestine, a torsion (twisting) of the intestine can compromise the blood supply to an area of the intestine. When this happens, the bacteria that are present have the upper hand. Without blood flow, antibodies can't get to the site easily. White blood cells have to travel farther after leaving the blood system to make it to an inflamed or infected area. This can also happen with blood clots affecting small vessels in the intestine and when there is inflammation severe enough to cause local swelling, which decreases blood flow. In some situations the nutrition of the tissues is affected enough that they can't repair themselves adequately and the situation worsens because there is tissue death in addition to the original problem. Ileus is stoppage of the normal intestinal contractions and it is an indication that the intestines are not faring well. It can occur in almost any severe intestinal problem. When conditions cause eating to stop or decrease, there may be a lack of important nutrients for cell repair, as well. These things all add up to make it harder for an antibiotic to work. To me, this situation is a little bit like fighting a battle with bullet proof glass between the armies. The temptation when the usual bullet won't penetrate the glass is to get a bigger bullet -- or in this case a "stronger" antibiotic. But perhaps a better approach would be to remove the glass ---- to figure out what is inhibiting healing and make it possible for the body to heal, rather than to rely on a super antibiotic. The problem with this approach in a situation like you experienced is that it is really expensive to try to provide intravenous nutritional support and to find and identify all the possible underlying causes that might lead to a secondary E. coli infection. If this type of care always worked, despite expense, I think that more veterinary hospitals would offer it. But even with really aggressive nutritional support and with early exploratory surgery, biopsy, culture and sensitivity and other lab testing, a fair number of patients die in human medicine, so it is reasonable to assume vets would have similar success rates. This problem, in combination with the great expense of stocking and using intravenous feeding materials and the equipment to allow it, keeps total parenteral nutrition (intravenous feeding to meet all the body's needs) impractical for most veterinary hospitals. I found the a summary of the article I referenced on the PubMed web site (there is a link from our link page). If you use the search term "E. coli" canine I think you will find it. The parentheses around the E. coli are necessary. E. coli can be passed from one animal to another through the water (that is how the outbreak that killed some people at a county fair last year occurred). I am not at all sure that is what happened in Buster's case but it is a possibility. If I didn't answer your questions fully, or clearly, please feel free to write again. Mike Richards, DVM 4/18/2000

Leptospirosis (zoonotic)

Question: I don't understand what Leptospirosis is so this article is not clear for me. Can you tell me what it is? Fort Dodge Animal Health has updated its Duramune line of vaccines to include the serovars (types) of leptospirosis that have been incriminated in most of the recent outbreaks. If you live in an area in which leptospirosis is a concern (the latest outbreaks were on Long Island and in California), it would be worthwhile to ask your vet if vaccination with these new vaccines would be prudent. These vaccines are manufactured using "sub-unit" technology that should help reduce reactions to the vaccines, which has previously been a problem with leptospirosis vaccinations. The two serovars added to the vaccine are grippotyphosa and pomona. Answer: Your question is a good one. In one of the older issues of the VetInfo Digest, available in the subscriber area (October 1998), this article explains leptospirosis: Leptospirosis Leptospirosis is a hot topic at dog shows and other competitions now. There has been an epidemic of leptospirosis in Long Island, NY now for a couple of years. It seems like there is an upward trend in the number of diagnosed cases across the country, although that isn’t certain since no one really keeps statistics on the number of cases of diseases in dogs and cats. This has occurred concurrently with recognition among veterinarians that leptospirosis is the portion of the combined canine vaccines that is most likely to cause reactions. So many vets are not vaccinating for this disease. That sounds pretty bad but the new cases of leptospirosis being reported are from Leptospirosis species that the vaccines do not protect against. At present there is no vaccine for the two strains causing most of the current problems, L. grippotyhosa and L. pomona. A third type (serovar) of Leptospira, L. bratislava is reported to be on the rise as well. Leptospirosis is a water-borne bacteria. It is spread most commonly by contamination of water sources by infected urine of wildlife and domestic animals. It can live in the environment long enough to spread effectively. Leptospirosis is most commonly associated with kidney disease but some of the strains of the organism can cause liver damage, induce bleeding disorders, cause neurologic signs or uveitis (eye inflammation). Leptospirosis is difficult to diagnose with certainty because the organism doesn’t grow well in cultures. Serum titers are useful in making a diagnosis but it often takes paired samples to demonstrate a rise in titer. In the meantime, it is important to treat for the organism to try to limit the damage that it does. Leptospirosis organisms are susceptible to penicillins, which should be used for at least two weeks if infection is suspected. It is also important to treat for any damage that is occurring to organs and to control any developing bleeding disorders. Kidney damage and bleeding disorders often require very aggressive treatment in order to achieve a successful outcome so this is a situation in which long-term hospitalization may be appropriate and necessary. Leptospirosis is especially scary because the bacteria can infect humans. It is important to observe good rules of hygiene, such as hand washing after handling the pet and even wearing latex or vinyl gloves when cleaning up urine or other body fluids. Pets suspected of having this illness should be quarantined from contact with other pets or any household members incapable of maintaining good hygienic practices. People who own pets that congregate in spots such as parks, dog shows, sporting competitions and other events should be careful about exposing their pets to places where water may be contaminated with urine or where there may be enough urine contamination to pose a risk. This can be very difficult to manage. It would be nice if there were an effective vaccine for the current crop of leptospirosis infections but there is not. If the older strains of this disease begin to reappear as vaccinations are no longer given it may be necessary to reconsider the risk/benefit ratio of those vaccines as well. It is very likely that one of the vaccine manufacturers is working on a new leptospirosis vaccination but I have no way of knowing whether that is the case. It would be worthwhile to check with your vet occasionally to see if there is a vaccination available if your pet fits the "high risk" profile of a dog or cat that is exposed to potentially contaminated water sources or is frequently in contact with large numbers of pets from all over the country. All in all, leptospirosis is still pretty rare. It is still a good idea to consider it whenever kidney disease occurs in a young to middle aged pet or when uveitis (ocular inflammation) occurs for no known reason. The new vaccines do protect against the two strains causing most of the recently recognized cases of leptospirosis. Leptospirosis should also be considered when signs of liver disease are present. Due to the water-borne nature of this bacteria, it is especially important to remember it as a cause of problems after flooding or extraordinarily heavy rains. Hope this clears things up a little. Mike Richards, DVM 3/2/2000

Pasteurella multocida

Q: Could you please let me know what causes this type of vaginal bacterial infection? Can it be contracted during breeding? If so, what are the symptoms, if any? What is the treatment of choice? Thank you

A: Dear "D" Pasteurella multocida, a bacteria, is a normal inhabitant of the reproductive tract of both male and female dogs, based on studies done by Drs. Bjurstrom and Linde-Forsberg of the Swedish University. On the other hand, some veterinarians do believe that pasteurellosis can cause problems with fertility. If this seems to be the case, the Swedish doctors also studied the effect of antibiotic therapy on bacterial flora and were able to demonstrate that a single dose of antibiotics to which the bacteria are susceptible will usually result in nearly complete clearance of the "infection". In another study of chronic vaginitis reported by Dr. Johnson in the Vet Clinics of North America it is important to rule out urinary tract infections and anatomical problems of the vagina or reproductive tract because these problems often enable the chronic infection noted. To sum up, a culture of the reproductive tract that shows Pasteurella sp. bacteria in an otherwise normal dog should probably be ignored. If signs of reproductive tract infection, such as vaginal discharge, are present, it is important to look for urinary tract infections and anatomical abnormalities in the reproductive tract before attempting treatment for the pasteurellosis. Hope this helps. Mike Richards, DVM

Beta Hemolytic Strep

Question: Please could you help with some information ? My friends dog has got Beta Haemolytic Strep Canis... Can you tell me what this is ? How serious is it ? What can be done to cure it ? How would it effect mating with this dog? Thank-you Answer: Strep canis is probably short for Streptococcus canis which would be a gram positive bacteria. Beta hemolytic streptoccal infections are resistant to penicillin in most cases but are responsive to other antibiotics such as cephalosporins or chloramphenicol in many instances. Bacterial sensitivity testing can be done to determine an appropriate antibiotic. From memory, I think that some dogs with streptococcal infections have been shown to have larger litters if they are treated with an appropriate antibiotic at the time of mating. There is some confusion over whether or not strep species bacteria are just a normal part of the vaginal flora or whether they are pathogenic. If this was found on a routine culture, with no clinical signs of disease, it is particularly tough to decide whether it is important. There have been reports that this bacteria can cause abortions, infertility and that it can infect the male if a female is infected. There is not much question that it is found when there are no visible problems and no history of reproductive problems in some bitches. That makes it really hard to tell you how serious the problem is -- or even if there is a problem when this bacteria is cultured. One way of being cautious and still breeding the female is artificial insemination. Sorry I can't be more definitive. Mike Richards, DVM