Multidrug-resistant Escherichia coli causing canine pyometra and urinary tract infections are genetically related but distinct from those causing prostatic abscesses.

Despite extensive characterisation of uropathogenic Escherichia coli (UPEC) causing urinary tract infections (UTIs), the genetic background of non-urinary extraintestinal pathogenic E. coli (ExPEC) in companion animals remains inadequately understood. In this study, we characterised virulence traits of 104 E. coli isolated from canine pyometra (n = 61) and prostatic abscesses (PAs) (n = 38), and bloodstream infections (BSIs) in dogs (n = 2), and cats (n = 3). A stronger association with UPEC of pyometra strains in comparison to PA strains was revealed. Notably, 44 isolates exhibited resistance to third-generation cephalosporins and/or fluoroquinolones, 15 were extended-spectrum ß-lactamase-producers. Twelve multidrug-resistant (MDR) strains, isolated from pyometra (n = 4), PAs (n = 5), and BSIs (n = 3), along with 7 previously characterised UPEC strains from dogs and cats, were sequenced. Genomic characteristics revealed that MDR E. coli associated with UTIs, pyometra, and BSIs belonged to international high-risk E. coli clones, including sequence type (ST) 38, ST131, ST617, ST648, and ST1193. However, PA strains belonged to distinct lineages, including ST12, ST44, ST457, ST744, and ST13037. The coreSNPs, cgMLST, and pan-genome illustrated intra-clonal variations within the same ST from different sources. The high-risk ST131 and ST1193 (phylogroup B2) contained high numbers of ExPEC virulence genes on pathogenicity islands, predominating in pyometra and UTI. Hybrid MDR/virulence IncF multi-replicon plasmids, containing aerobactin genes, were commonly found in non-B2 phylogroups from all sources. These findings offer genomic insights into non-urinary ExPEC, highlighting its potential for invasive infections in pets beyond UTIs, particularly with regards to high-risk global clones.

The presence of virulence factor genes downregulates uterine AQP3 and alters glutathione peroxidase activity and uterine histopathology in canine pyometra.

Present study was designed to evaluate the role of virulence factor genes (papG, cnf1 and hylA) in the pathogenesis of canine pyometra. Antimicrobial susceptibility test and detection of virulence genes were performed Escherichia coli (E. coli) detected in uterine swab samples. Animals were divided into two groups based on the presence (VF+, n:14) or absence (VF-, n:7) of the virulence factor genes papG, cnf1 and hylA. Blood and tissue glutathione peroxidase activity, uterine histopathologic analysis and AQP3, ESR1, PGR, OXTR gene expressions were determined in both groups. Statistical analyses were performed using Stata version 15.1. All E. coli isolates were susceptible to amikacin, whereas resistant to ampicillin, amoxicillin/clavulanic acid and lincomycin. None of the isolates were susceptible to cefotaxime. E. coli isolates had at least one virulence gene. The most prevalent gene was fimH (100%), followed by fyuA (95.8%), usp (83.3%), sfa (75%), cnf1 and hlyA (70.8%) genes. Blood GPx activity was greater in VF+ animals. On the other hand, uterine tissue GPx activity was lower in VF+ group compared to the control group. Expression levels of AQP3 were upregulated more than fivefold in VF-dogs compared to the control group. In addition, AQP3 expression levels were found approximately threefold higher in VF (-) than VF (+) group (p < .05). Varying degree of inflammation noted for all animals with pyometra, but the presence of bacteria noted only in VF+ animals. In conclusion, the presence of virulence factor genes does not play a role in the histopathological degree of inflammation, the presence of bacteria was found to vary. Serum GPx activity increased in VF+ animals. While the hormone receptor expressions were similar, AQP expression was upregulated in the absence of virulence factor genes.

Escherichia coli isolated from pyometra and cystitis in the same animal exhibit a wide phenotypic similarity.

AIMS: Pyometra and cystitis caused by Escherichia coli are common diseases identified in canine or feline females. The origin of pyometra infection remains uncertain, and effective prevention strategies for this disease are still unknown. This study aimed to provide a phenotypic characterization, including antimicrobial resistance and virulence profiles, of endometrial pathogenic (EnPEC) and uropathogenic (UPEC) E. coli strains isolated simultaneously from the same animal. METHODS AND RESULTS: Sixteen E. coli strains, from eight different animals, were analyzed in this study. The antimicrobial susceptibility profile of EnPEC and UPEC strains was determined using the disc diffusion method, which showed a similar susceptibility profile among strains (EnPEC and UPEC) from the same animal. The virulence profile of the strains was assessed through biofilm formation, as well as serum resistance abilities. EnPEC and UPEC strains from the same animal exhibited slight variations in their virulence and antimicrobial resistance capabilities. Overall, most of the strain pairs showed a high similarity in their ability to establish biofilms and survive in serum complement activity. CONCLUSIONS: Overall, strains of E. coli isolated from both pyometra and cystitis in the same animal, despite presenting distinct clinical diseases, exhibit a wide phenotypic similarity, suggesting a common origin for the strains.

Comparative genetic and pathogenic approaches of Escherichia coli isolated simultaneously from pyometra and urine of bitches.

Escherichia coli (E. coli) are widely related to pyometra and cystitis in dogs, and these infections can occur simultaneously. The goal of this study was to determine genetic and pathogenic insights of 14 E. coli isolated simultaneously from pyometra content and bladder urine of seven bitches. To achieve this, in silico and in vitro comparative analyses were conducted. Whole-genome comparisons demonstrated that E. coli isolated from pyometra and urine of the same animal were predominantly genetic extraintestinal E. coli clones belonging to the same Sequence Type and phylogroup. The E. coli clones identified in this study included ST372, ST457, ST12, ST127, ST646, and ST961. Five isolates (35.7%) belonged to the ST12 complex. Except for two E. coli, all other isolates belonged to the B2 Clermont phylogroup. Interestingly, some genomes of E. coli from urine carried more virulence genes than those E. coli from pyometra. Both pyometra and urine E. coli isolates demonstrated a strong affinity for adhering to HeLa and T24 cells, with a low affinity for invading them. However, certain isolates from urine exhibited a greater tendency to adhere to T24 cells in qualitative and quantitative assays compared to isolates from pyometra. In conclusion, this study revealed the high genomic similarity between pyometra and urine E. coli isolates, as well as the virulent capacity of both to colonize endometrial and urothelial cells. The findings of this study underscore the importance of concurrently managing both infections clinically and could potentially contribute to future resources for the prevention of cystitis and pyometra.

Successful Treatment of Pyometra Caused by Pseudomonas aeruginosa Infection in a Rabbit.

This article reports an unusual presentation of pyometra in a pet rabbit. A 2-year-old mixed-breed female rabbit with pelvic limb paralysis was referred for abdominal distension associated with prolonged depression and decreased appetite. Clinical examination and diagnostic imaging (radiographs and ultrasound) led to the provisional diagnosis of pyometra that was caused by the presence of an enlarged organ containing fluid material and occupying most of the caudal abdomen. Exploratory laparotomy was performed under general anesthesia. After abdominal wall incision along the linea alba, the uterus was immediately evident and the uterine wall was over-distended and damaged, with purulent material free in the abdominal cavity. Ovariohysterectomy was performed and uterine wall samples were sent for microbiological examination and antimicrobial susceptibility testing. The agent causing the pyometra was found to be Pseudomonas aeruginosa, which was resistant to enrofloxacin and ceftazidime. This is the first report of pyometra caused by P. aeruginosa in a pet rabbit, based on a literature search. Furthermore, a peculiarity of the present case is the occurrence of pyometra in a rabbit with no history of mating or parturition.

The endometrium histopathology and cell ultrastructure in bitches with pyometra induced using progesterone and Escherichia coli.

BACKGROUND: We investigated uterine histopathological and ultrastructural changes in female dogs with pyometra induced by Escherichia coli (E. coli) inoculation using progesterone and/or estradiol. METHODS: Dogs were ovariectomized and classified into six groups: Groups 1-6 corresponding to estradiol treatment followed by progesterone supplementation, progesterone supplementation only, estradiol supplementation only, simultaneous treatment using estradiol and progesterone, similar to Group 1 but with a double dose, and control group, respectively. RESULTS: Pyometra was successfully induced in Groups 1, 2, 4, and 5, but not in Group 3. An uneven endometrial surface was observed, along with a purulent discharge, bleeding, inflammatory lesions, cystic endometrial hyperplasia (CEH) or cystic endometrial atrophy. Endometrial thickness percentage, uterine wall thickness, and the percentage of endometrial cyst area increased. Endometrial epithelial mushroom-like hyperplasia and the honeycomb-like structure exposed under the epithelium after flaky exfoliation were found, and the glandular epithelial villi became longer or shorter. Mitochondria expansion and increased lysosome were observed. Endoplasmic reticulum dilation and swelling and many inflammatory cells, especially plasma cell infiltration in the stroma, were found. CONCLUSIONS: Endometrial histopathology and ultrastructural changes in affected dogs were accompanied by induction of pyometra, and they were affected by different hormonal patterns and E. coli.

Insights on the genetic features of endometrial pathogenic Escherichia coli strains from pyometra in companion animals: Improving the knowledge about pathogenesis.

Endometrial pathogenic E. coli (EnPEC) isolates are involved in endometrial infections in animals and humans. Besides the high aggressiveness of the endometrial infections, the EnPEC virulence profile and pathogenesis are still little known. In this study, we have sequenced and analyzed an EnPEC strain from canine pyometra (E. coli_LBV005/17), following a molecular characterization of the virulence profile and phylogenetic evolution of an EnPEC collection from canines and felines (45 strains). Most of the strains belonged to phylo-group B2, and display a high virulence profile. In particular we highlight the classification of the E. coli_LBV005/17 as sequence type 131 (ST131), in addition to other five strains, as observed by gyrB phylogenetic analysis. Also, the phylogenetic position of EnPEC strains from pyometra in companion animals suggests that their origins are from both extraintestinal and commensal E. coli strains. Accordingly to Principal Coordinates Analysis (PCoA) and phylogenetic analysis we can propose that EnPEC strains have neither the same genetic profile, nor a unique common ancestral. In summary, the present work characterize an EnPEC genome from bitch pyometra and the genetic profile of 45 EnPEC strains from companion animals pyometra, being the commonest virulence pattern: fimA, papC, hlyA, hlyE, cnf1, entB, iroN, irp1, bssS, bssR, and hmsP. These data improving the background knowledge of this E. coli pathotype related to pyometra in companion animals and may support new methods to prevent the disease evolution.

Evaluation of Biofilm Production by Escherichia coli Isolated From Clinical Cases of Canine Pyometra.

Many Escherichia coli (E. coli) strains produce biofilm that confers antimicrobial resistance. However, studies of biofilm production by E. coli from canine pyometra are lacking. Objectives were to elucidate the role of biofilm production by E. coli in pyometra by: (1) assessing the ability of E. coli to produce biofilm in vitro, and (2) confirming biofilm in situ. Endometrial biopsies were obtained from bitches with pyometra and preserved for microscopic analysis (n = 25). An endometrial swab was submitted for aerobic culture. Samples with confirmed E. coli were evaluated further for biofilm production in vitro and in vivo. Seventy percent of cases (16/23) resulted in pure growth of 1 or 2 E. coli strains, totaling 20 isolates. Fifteen isolates (15/20, 75%) had higher optical densities then negative controls (P < .05). On histopathology, all tissues exhibited endometrial inflammation and mucus was located within endometrial glands and occasionally overlying epithelium on 14 slides (14/16, 88%). Bacteria was noted in 50% of slides (8/16). During FISH acellular debris within the uterine lumen consistent with biofilm was noted on 94% of samples (15/16) and E coli was positively identified on all samples (15/15). Areas suggestive of the presence of biofilm were observed on all samples on scanning electron microscopy; but, bacteria consistent with E. coli were only visualized in 9 samples (9/16, 56%). In conclusion, we demonstrated that relevant strains of E. coli produce biofilm in vitro and in vivo, which may be considered in the development of new pyometra treatments aimed at disrupting these E. coli biofilm.

Bacteria causing pyometra in bitch and queen induce neutrophil extracellular traps.

Neutrophils are capable of releasing their DNA in response to infectious agents to form neutrophil extracellular traps (NETs) to destroy pathogens. Even though pyometra in queens and bitches is a common disease, its pathogenesis is not fully understood. The aim of this study was to assess the presence of NETs in the endometrium of queens and bitches suffering from pyometra. Pyometra and normal uteri were obtained after ovariohysterectomy from adult queens and bitches in diestrus. Uterine contents were evaluated for bacterial isolation and identification and for NETs presence. Escherichia coli were isolated in 5/5 queens and 4/5 bitches, and Streptococcus spp in one bitch. Sterile glass coverslips were placed on the endometrium surface to obtain material for NETs that were evaluated by immunocytochemistry (histone, neutrophil elastase or myeloperoxidase), fluorescence microscopy or scanning electron microscopy. NETs in endometrium content were positively stained by DNA histone DAPI, myeloperoxidase and by neutrophil elastase. NETs were spread in all observed queen and bitch endometria of pyometra cases. Ultrastructure images of NETs depicted clusters of globular material with fine filaments deposited on or around thick filaments and trapped bacteria. To the best of our knowledge these are the first findings confirming NETs endometrial presence in queen and bitch pyometra. Nevertheless, the precise role of NETs in pyometra in the bitch and queen, either to contribute to the defeat of infection or to its persistence remains to be unraveled.

Bacterial invasion of the uterus and oviducts in bovine pyometra.

Pyometra is a common disease of cattle that causes infertility and thereby financial losses to the cattle industry. Bacteria involved in the development and progression of pyometra have been investigated by microbial culture but their tissue invading abilities, which is an important aspect of bacterial pathogenicity and development of lesions, have not been investigated. Bacterial invasion of the uterus and oviducts was studied in 21 cows diagnosed with pyometra at the time of slaughter by applying fluorescence in situ hybridization using probes targeting 16S ribosomal RNA of Fusobacterium necrophorum, Porphyromonas levii, Trueperella pyogenes and the overall bacterial domain Bacteria. Fusobacterium necrophorum and P. levii were found to invade the endometrium, especially if the endometrium was ulcerated, and penetrated deep into the lamina propria. These species co-localized within the tissue thus indicating a synergism. Trueperella pyogenes did not invade the uterine tissue. In addition to endometrial lesions, most cows with pyometra also had salpingitis but without significant bacterial invasion of the oviductal wall.

A case of pyometrocolpos with Bifidobacterium species.

Bifidobacterium species, a normal commensal of the human gastrointestinal tract, female genitourinary tract and vagina is usually considered non-pathogenic and is being used therapeutically as probiotic due to its beneficial effects. However, there are several case reports implicating Bifidobacteria as the causative agent in various infectious conditions. Infections with Bifidobacteria are often ignored or underreported as they are part of the normal gut microbiome. Here we discuss a case of pyometrocolpos with Bifidobacterium species. Clinical outcome of the patient was good after emergency drainage and antibiotic treatment with Cefoperazone sulbactam and Metronidazole.

Immunomodulation in the canine endometrium by uteropathogenic Escherichia coli.

This study was designed to evaluate the role of E. coli α-hemolysin (HlyA) in the pathogenesis of canine pyometra, and on the immune response of canine endometrial epithelial and stromal cells. In Experiment 1, the clinical, hematological, biochemical and uterine histological characteristics of ß-hemolytic and non-hemolytic E. coli pyometra bitches were compared. More (p < 0.05) metritis cases were observed in ß-hemolytic E. coli pyometra uteri than in non-hemolytic E. coli pyometra uteri. ß-hemolytic E. coli pyometra endometria had higher gene transcription of IL-1ß and IL-8 and lower gene transcription of IL-6 than non-hemolytic E. coli pyometra endometria (p < 0.01). In Experiment 2, the immune response of endometrial epithelial and stromal cells, to hemolytic (Pyo18) and non-hemolytic E. coli strains (Pyo18 with deleted hlya-Pyo18ΔhlyA- and Pyo14) were compared. Following 4 h of incubation, Pyo18 decreased epithelial cell numbers to 54% (p < 0.001), and induced death of all stromal cells (p < 0.0001), whereas Pyo18ΔhlyA and Pyo14 had no effect on cell numbers. Compared to Pyo18ΔhlyA and Pyo14, respectively, Pyo18 induced a lower transcription level of IL-1ß (0.99 vs 152.0 vs 50.9 fold increase, p < 0.001), TNFα (3.2 vs 49.9 vs 12.9 fold increase, p < 0.05) and IL-10 (0.4 vs 3.6 vs 2.6 fold increase, p < 0.001) in stromal cells, after 1 h of incubation. This may be seen as an attempt of hemolytic E. coli to delay the activation of the immune response. In conclusion, endometrial epithelial and stromal cell damage induced by HlyA is a potential relevant step of E. coli virulence in the pathogenesis of pyometra.

Emphysematous pyometra secondary to Enterococcus avium infection in a dog.

A 5-year-old female intact Mastiff dog was presented with a history of vaginal discharge for 1 day. Physical examination revealed a sanguineo-purulent vaginal discharge and systemic inflammatory response syndrome. Abdominal radiographs showed several dilated and gas- filled tubular loops. The differential diagnoses included emphysematous pyometra or small intestinal mechanical ileus. Surgical exploration of the abdomen demonstrated a severely dilated and gas-filled uterus, and emphysematous pyometra was confirmed. The patient's clinical signs resolved after ovariohysterectomy. Histopathology revealed mild endometrial cystic hyperplasia with infiltration of inflammatory cells in the superficial endometrial epithelia. Enterococcus avium, an α-hemolytic gram-positive coccus, was isolated from the uterus. This paper highlights the radiographic features of emphysematous pyometra and a pathogen that has never been reported to be associated with canine pyometra previously.

Multiplex cytokine analyses in dogs with pyometra suggest involvement of KC-like chemokine in canine bacterial sepsis.

Clinical diagnostic criteria for sepsis (systemic inflammatory response syndrome caused by infection) are unspecific and, therefore, biomarkers for sepsis diagnosis are needed for appropriate treatment and patient survival. Pyometra, a common disease caused by bacterial infection of the uterus, results in sepsis in nearly 60% of cases in dogs. We used dogs with pyometra as a natural model for sepsis and collected serum samples from 39 dogs, of which 22 with pyometra and 17 healthy controls. Dogs with pyometra were further grouped into dogs with sepsis (n=18) and without sepsis (n=4). Serum concentrations of a panel of cytokines, including keratinocyte-derived chemokine (KC)-like, granulocyte-macrophages colony stimulating factor (GM-CSF), interleukin (IL)-2, IL-4, IL-6, IL-7, IL-8, IL-10, IL-15, IL-18, chemokine C-X-C motif ligand (CXCL)10 and tumor necrosis factor (TNF)-α, were measured using multiplex analyses. Serum C-reactive protein (CRP) levels were determined using an automated immunoturbidimetric assay. In addition to physical examination hematological and serum biochemical analyses were performed to evaluate the overall status of the dogs. Significantly higher concentrations of KC-like (757 vs 304 pg/ml) were detected in dogs with pyometra as compared to healthy dogs. Within the pyometra group, dogs with sepsis compared to dogs without sepsis had a higher KC-like concentration (873 vs 300 pg/ml). Hemoglobin levels were significantly lower in dogs with pyometra compared to healthy dogs, regardless of the presence or absence of sepsis, and correlated negatively with KC-like. KC-like concentrations correlated positively with CRP, number of hospitalization days, number of monocytes, concentrations of IL-8, and percentage band neutrophils. Our data suggest that bacterial infection triggers the expression of KC-like and further studies are warranted of KC-like as a possible biomarker for diagnosing sepsis and uterine bacterial infection in dogs.

Clinical Significance of Pyometra.

OBJECTIVE: To review the clinical profiles and management outcomes of patients with pyometra. STUDY DESIGN: A retrospective review of all women admitted with a confirmed diagnosis of pyometra over an 8-year period (January 2003 to December 2010). The medical records, including operation notes, histological and microbiological results, were reviewed. RESULTS: A total of 57 patients accounting for 76 admissions were identified. The mean patient age was 82.0 ± 11.3 years. The most common presenting symptom was postmenopausal bleeding (59.2%), followed by vaginal discharge (40.8%), fever (6.6%), and abdominal pain (5.3%). Drainage of pyometra was either by uterine Foley catheter insertion (48 patients [84.2%]) or repeated endometrial aspiration (2 patients [3.5%]). Antibiotics were prescribed to 49 patients (86.0%). Diagnostic hysteroscopy with mechanical cervical dilation was performed in 6 patients (10.5%). Gynecological malignancy was identified in only 1 patient, while colorectal cancer was identified in 2 patients. No patient had spontaneous uterine perforation or sepsis. Sixteen patients had recurrent pyometra within a mean follow-up period of 5.1 ± 5.8 months (range, 0.5-23 months). CONCLUSION: Pyometra usually presents with postmenopausal bleeding and can be treated with drainage and antibiotics treatment. In contrast to previous reports, our study indicates that spontaneous uterine perforation and gynecological malignancies are not commonly associated with pyometra.

Serum IL-6 and IL-10 concentrations in bitches with pyometra undergoing ovariohysterectomy.

BACKGROUND: Pyometra is a serious bacterial infection of the uterus affecting female dogs and manifests as an accumulation of pus in the uterine lumen. The aim of the study was to assess changes in serum interleukin (IL)-6 and IL-10 concentrations in bitches with pyometra undergoing ovariohysterectomy. FINDINGS: Blood samples were collected from healthy bitches (controls) and bitches with pyometra before surgery, and 3 and 10 days after ovariohysterectomy. Before surgery, bitches with pyometra had significantly higher serum concentrations of IL-6 and IL-10 than the controls. After surgery, the serum concentration of IL-6 and IL-10 decreased significantly. In healthy dogs, the concentration of IL-6 and IL-10 showed a significant increase 3 days after surgery followed by a decrease on day 10. CONCLUSION: An increase in serum concentrations of IL-6 and IL-10 was present before surgery in bitches with pyometra and 3 days after ovariohysterectomy in healthy controls. Concentrations decreased after ovariohysterectomy and/or proper healing, suggesting that these cytokines can be useful for assessment of the postoperative period in bitches.

Phylo-typing of clinical Escherichia coli isolates originating from bovine mastitis and canine pyometra and urinary tract infection by means of quadruplex PCR.

BACKGROUND: Escherichia coli is one of the major causative agents of bovine mastitis worldwide, and is typically associated with acute, clinical mastitis. Besides this, E. coli strains which belong to the extra-intestinal pathogenic group are also the major cause of urinary tract infections and pyometra in dogs. OBJECTIVES: In this study, it was aimed to investigate phylo-groups/subgroups in 155 E. coli isolates obtained from acute bovine mastitis, 43 from urinary tract infections of dogs and 20 from canine pyometra by a formerly described triplex PCR and recently described new quadruplex polymerase chain reaction (PCR) method. RESULTS: Group A1 (n = 118; 76%) and B1 (n = 71; 46%) were found to be the most prevalent groups by triplex and quadruplex PCR assays in mastitis isolates, respectively. Phylo-typing of 43 urinary tract isolates also revealed that most of the isolates belonged to A1 (n = 23; 54%) by triplex and B2 (n = 36; 84%) by quadruplex PCR assays. The isolates assigned as group A1 (n = 17; 85%) by triplex PCR could not be classified by quadruplex PCR in pyometra isolates. CONCLUSIONS: The results support the hypothesis that E. coli strains isolated from bovine mastitis cases are environmental. Also, groups C, E and F were identified as new phylo-groups for the first time in acute bovine mastitis cases. The comparison of triplex PCR with quadruplex PCR results revealed that most of the groups assigned in triplex PCR were altered by quadruplex PCR assay.

Pathogenic Escherichia coli and lipopolysaccharide enhance the expression of IL-8, CXCL5, and CXCL10 in canine endometrial stromal cells.

Chemokines play a central role in cellular communication in response to bacterial infection. However, the knowledge of the chemokine responses to bacterial infections in dogs remains limited. Uterine bacterial infection (pyometra) is one of the most common bacterial diseases in dogs and causes sepsis in most of the cases. We have shown previously that dogs with pyometra have higher messenger RNA (mRNA) levels of chemokines in uterus. To assess whether the stromal part of the endometrium expresses chemokines in response to bacterial infection, we cultured endometrial stromal cells isolated from healthy dogs and exposed them to either live pathogenic Escherichia coli, isolated from the uterus of a dog with pyometra, or lipopolysaccharide. Changes in the mRNA expression of ELR(+) CXC chemokines, IL-8, CXCL5, CXCL7, and ELR(-) CXC chemokine, CXCL10, were measured after 24 hours using quantitative real-time polymerase chain reaction. Levels of IL-8, CXCL5, and CXCL10 were upregulated in endometrial stromal cells exposed to E coli and lipopolysaccharide, whereas the level of CXCL7 was decreased or unaffected. In addition, levels of IL-8 and CXCL5, but not CXCL7 or CXCL10, were significantly higher in dogs with pyometra than those in healthy dogs. Our findings show that pathogenic uterine-derived E coli induces a CXC chemokine response both in cultured endometrial stromal cells within 24 hours and in pyometra-affected uteri from dogs. Stromal cells could therefore play an important role in early neutrophil and T cell recruitment to the site of inflammation during gram-negative bacterial infection of the uterus. Further studies are needed to clarify the role of chemokines in host response to bacterial infection in dogs and the possibility of using chemokines as diagnostic parameters for bacterial infection in this species.