Enhanced adherence of methicillin-resistant Staphylococcus pseudintermedius sequence type 71 to canine and human corneocytes

The recent worldwide spread of methicillin-resistant Staphylococcus pseudintermedius (MRSP) in dogs is a reason for concern due to the typical multidrug resistance patterns displayed by some MRSP lineages such as sequence type (ST) 71. The objective of this study was to compare the in vitro adherence properties between MRSP and methicillin-susceptible (MSSP) strains. Four MRSP, including a human and a canine strain belonging to ST71 and two canine non-ST71 strains, and three genetically unrelated MSSP were tested on corneocytes collected from five dogs and six humans. All strains were fully characterized with respect to genetic background and cell wall-anchored protein (CWAP) gene content. Seventy-seven strain-corneocyte combinations were tested using both exponential- and stationary-phase cultures. Negative binomial regression analysis of counts of bacterial cells adhering to corneocytes revealed that adherence was significantly influenced by host and strain genotype regardless of bacterial growth phase. The two MRSP ST71 strains showed greater adherence than MRSP non-ST71 (p < 0.0001) and MSSP (p < 0.0001). This phenotypic trait was not associated to any specific CWAP gene. In general, S. pseudintermedius adherence to canine corneocytes was significantly higher compared to human corneocytes (p < 0.0001), but the MRSP ST71 strain of human origin adhered equally well to canine and human corneocytes, suggesting that MRSP ST71 may be able to adapt to human skin. The genetic basis of the enhanced in vitro adherence of ST71 needs to be elucidated as this phenotypic trait may be associated to the epidemiological success and zoonotic potential of this epidemic MRSP clone.     

In vitro adherence of Staphylococcus pseudintermedius to canine corneocytes is influenced by colonization status of corneocyte donors

The current knowledge of in vitro adherence of Staphylococcus pseudintermedius to canine corneocytes is limited to comparative analyses between strains, staphylococcal species or corneocytes collected from different breeds, body sites and hosts. However, the role played by colonization status of corneocyte donors remains unknown. The aim of this study was to evaluate the adherence properties of commensal S. pseudintermedius strains to corneocytes collected from dogs with different colonization status. For this purpose, corneocytes were collected from five dogs that were classified as persistently colonized (D1 and D2), intermittently colonized (D3 and D4) or non-colonized (D5) on the basis of the results of a previous longitudinal study. Adherence to corneocytes originating from each of the five dogs was assessed by an in vitro adhesion assay using four genetically unrelated strains isolated from the colonized dogs (S1 to S4). Irrespective of their host of origin, all strains adhered significantly better to corneocytes from D1 and D2 than to corneocytes from D3, D4 and D5 (P < 0.0001). The mean count of cells adhering to corneocytes from persistently colonized dogs was on average three times higher than the mean count using corneocytes from the other dogs. A significant difference between strains was only observed for one strain-corneocyte combination (S2-D4), indicating that S. pseudintermedius adherence to corneocytes is driven by host factors and only marginally influenced by strain factors. This finding has important implications for understanding and preventing S. pseudintermedius skin colonization and infection.     

Reduced in vitro adherence of Staphylococcus species to feline corneocytes compared to canine and human corneocytes

It is apparent that in-contact humans and animals exchange commensal staphylococci. Previous in vitro studies, however, indicate that staphylococci preferentially adhere to corneocytes from host species. This study compared adherence of meticillin-sensitive and -resistant Staphylococcus aureus (MSSA/MRSA), S. intermedius, S. felis and S. hominis to feline, canine and human corneocytes acquired from 10 healthy subjects using adhesive tape discs. Adherent bacteria were counted using an image processing and analysis programme. Mean adherence of MSSA (P = 0.0009), MRSA (P = 0.0162) and S. intermedius (P = 0.0117), but not S. felis or S. hominis, to feline corneocytes was significantly lower than that to canine and human corneocytes. All the isolates had similar adherence to both human and canine corneocytes. S. felis was the most adherent species to feline corneocytes followed by S. intermedius, and then MSSA, MRSA and S. hominis. For dogs and humans, S. intermedius and S. felis were the most adherent, followed by MRSA and MSSA, and then S. hominis. These results do not reveal any preferential adherence of staphylococci to canine or human corneocytes. Poor adherence to feline corneocytes could suggest that cats are relatively resistant to pyoderma and cross-species transmission of staphylococci.     

Monosaccharide inhibition of adherence by Pseudomonas aeruginosa to canine corneocytes

The effect of d -galactose, d -mannose, l -rhamnose and dextrose on the adhesion to canine corneocytes by three strains of Pseudomonas aeruginosa was studied in six healthy dogs. Canine corneocytes were collected from the inner aspect of the pinna using adhesive discs (D-Squame®). Half millimetre of bacterial suspension in phosphate-buffered saline (PBS) with or without the addition of a monosaccharide was placed over the corneocyte layer and incubated in moist chambers. Image analysis was used to quantify bacterial adherence to corneocytes. The three strains of Pseudomonas adhered well to canine corneocytes. All monosaccharides tested inhibited the adherence of Pseudomonas to canine corneocytes. The mean reduction in adhesion for individual sugars at a concentration of 0.1% was 40.2% (dextrose), 30.8% ( l -rhamnose), 25.6% ( d -galactose) and 19.4% ( d -mannose). When d -galactose, d -mannose and l -rhamnose were used in combination at 0.1% concentration, the mean reduction in adherence was 52.9%. The monosaccharides studied may have a potential role in the management of Pseudomonas infections in dogs.     

Factors affecting the adherence of Malassezia pachydermatis to canine corneocytes in vitro

Abstract Suspensions of Malassezia pachydermatis adhered to canine corneocytes attached io adhesive tape in a dose (P < 0.001) and time-dependent (P < 0.01) manner; adherence was maximal after 2 h. M. pachydermatis cells were approximately 10 times more adherent than Saccharomyces cerevisiae (P < 0.001) cells after 2 h incubation. The adherence of formalin-treated and frozen-thawed M. pachydermatis cells was comparable with untreated controls. Stationary-phase cells adhered better (P < 0.05) than exponential-phase cells. Pretreatment of the yeasts, or corneocytes, with 0.1% trypsin for 30 min reduced (P < 0.01) the adherence of four, and two, out of five strains, respectively, whereas incubation with 300 mM solutions of D(+) mannose, sucrose and N-acetyl D-glucosamine had no consistent effect. These results suggest that trypsin-sensitive proteins or glycoproteins on the yeast cell wall, and on the corneocyte surface, play an important role in the adherence of M. pachydermatis to canine corneocytes in vitro, whereas a role for carbohydrate receptors was not demonstrated. Résumé— Des suspensions de Malassezia pachydermatis adhérant à des cornéocytes des chiens sont attachées à des rubans adhésifs de façon significative en function du nombre (P < 0,001) et de la durée (P < 0,01). L'adhérence est maximale après 2 heures. Les levures du genre Malassezia pachydermatis sont approximativement dix fois plus adhérentes que les levures du genre Saccharomyces cerevisiae (P < 0,001) après une incubation de 2 heures. L'adhérence des Malassezia pachydermatis traitées par le formol et congelées - décongelées, est comparable à celle des témoins. Les levures qui ne sont pas en phase de croissance adhérent mieux (P < 0,05) que celles qui le sont. Le traitement préalable des levures ou des cornéocytes avec une solution de trypsine pendant 30 minutes réduit (P < 0,01) l'adhérence tandis que l'incubation avec des solutions à 300 mM de D + mannose, sucrose et de N acétyl D glucosamine n'a pas d'effets. Ces résultats suggèrent que des protéines sensibles à la trypsine ou des glycoprotéines sur la paroi des levures et à la surface des cornéocytes jouent un rôle important in vitro dans l'adhérence des Malassezia pachydermatis aux cornéocytes du chien, alors que le rôle des récepteurs glucidiques n'a pas été démontré. [Bond, R., Lloyd, D. H. Factors affecting the adherence of Malassezia pachydermatis to canine cornéocytes in vitro (Facteurs influençant l'adhérence de Malassezia pachydermatis aux cornéocytes du chien in vitro). Veterinary Dermatology 1996; 7 : 49–56.] Resumen Las suspensiones de Malassezia pachydermatis se adherian a cinta adhesiva de forma dependiente de la dosis (P < 0.001) y del tiempo (P < 0.01); su adherencia fue máxima a las 2 h. Las células de M. pachydermatis fueron aproximadamente 10 veces más adherentes que las de Saccharomyces cerevisiae (P < 0.001) a las 2 h de incubación. La adherencia de células de M. pachydermatis tratadas con formalina y congeladas-descongeladas fue comparable con los controles no tratados. Las células en estadio estacionario se adherian mejor (P < 0.05) que las de fase exponencial. El tratamiento previo de las levaduras o los corneocitos con 0.1% de tripsina durante 30 min redujo (P < 0.01) la adherencia de cuatro, y dos, de cinco cepas, respectivamente, mientras que su incubación con soluciones 300 mM de D(+) manosa, sucrosa y N-acetil D-glucosamina no tuvieron un efecto constante. Estos resultados sugieren que proteinas o glieoproteinas sensibles a la tripsina en la pared de la levadura, y en la superficie del corneocito, juegan un papel importante en la adherencia de M. pachydermatis a los corneocitos caninos in vitro, mientras que no se pudo demostrar un papel por parte de los receptores de carbohidratos. [Bond, R., Lloyd, D. H. Factors affecting the adherence of Malassezia pachydermatis to canine corneocytes in vitro (Facto res que afectan la adherencia de Malassezia pachydermatis a los corneocitos caninos in vitro). Veterinary Dermatology 1996; 7 : 49–56.] Zusammenfassung— Suspensionen von Malassezia pachydermatis zeigten eine Adhärenz an kanine Korneozyten, die an einem Klebeband befestigt waren, in dosisabhängiger (P < 0,001) und zeitabhängiger Weise (P < 0,01). Die Adhärenz erreichte ein maximum nach 2 Stunden. M. pachydermatis-Zellen waren ungefähr 10 mal stärker adhärent als Saccharomyces cervisiae-Zellen nach Zstündiger Inkubation (P < 0,001). Die Adhärenz von formalinbehandelten und gefrorenen/aufgetauten M. pachydermatis-Zellen war vergleichbar mit unbehandelten Kontrollzellen. Zellen der stationären Phase waren besser adhärent (P < 0,05) als Zellen der exponentiellen Phase. Eine Vorbehandlung der Hefen oder Korneozyten mit 0,1% igem Trypsin über 30 Minuten reduzierte die Adhärenz (P < 0,01) von 4 bzw. 2 aus 5 Linien, während eine Inkubation mit 300 mm Lösungen von D(+)Mannose, Sucrose und N-Acetyl-D-Glukosaminen keinen entsprechenden Effekt hatte. Diese Ergebnisse legen nahe, daß Trypsin-sensible Proteine oder Glykoproteine an der Zellwand der Hefe und auf der Korneozytenoberfläche eine wichtige Rolle für die Adhärenz von M. pachydermatis an kanine Korneozyten in-vitro spielen, während eine Bedeutung für Kohlenhydrat-Rezeptoren nicht demonstriert werden konnte. [Bond, R., Lloyd, D. H. Factors affecting the adherence of Malassezia pachydermatis to canine corneocytes in vitro (Einflußfaktoren auf die Adhärenz von Malassezia pachydermatis an kanine Korneozyten in vitro). Veterinary Dermatology 1996; 7 : 49–56.]     

Species specificity in the adherence of staphylococci to canine and human corneocytes: a preliminary study

Staphylococcal pyoderma is rarely contagious between dogs and humans, or humans and dogs. This study investigated the hypothesis that there are species differences in adherence of Staphylococcus intermedius (the most common isolate from dogs) and Staphylococcus aureus (the most common isolate from humans) to canine and human corneocytes. Sheets of corneocytes were collected from the ventral abdomen of 10 dogs and the medial forearm of 10 humans (all healthy and without any history or physical signs of skin disease) using double-sided tape. Staphylococcus intermedius from a case of canine bacterial pyoderma and a human strain of S. aureus were prepared in phosphate buffered saline (PBS) and applied in duplicate, respectively, to the canine and human corneocyte-covered tapes using PBS as negative control. After incubation, rinsing, and staining with crystal violet, quantification of the adherent bacteria was carried out blindly by computerized image analysis. Staphylococcus intermedius was found to adhere significantly more to canine corneocytes than S. aureus (P = 0.0006), whereas S. aureus showed greater adherence to human corneocytes than S. intermedius (P < 0.0001). In addition, the pattern of adherence differed between the two organisms, with S. intermedius adhering to the entire surface and S. aureus adhering mainly to the periphery of both canine and human corneocytes. Preference for adherence to these two hosts may explain, in part, why S. intermedius and S. aureus are uncommonly isolated from human and canine skin infections, respectively.     

Staphylococcal and micrococcal adherence to canine and feline corneocytes: quantification using a simple adhesion assay

In this paper a simple adhesion assay suitable for the assessment of bacterial adhesion to both canine and feline corneocytes is described. Using this assay Staphylococcus intermedius, Staphylococcus aureus and Staphylococcus chromogenes were shown to adhere well to both canine and feline corneocytes. The numbers of adherent bacteria were, however, generally lower for feline corneocytes. Both Staphylococcus hominis and a Micrococcus species adhered poorly to canine and feline corneocytes. This is the first report documenting bacterial adhesion to feline corneocytes.     

Studies on the role of carbohydrates in the adherence of Malassezia pachydermatis to canine corneocytes in vitro

A panel of four lectins was used to investigate the role of carbohydrates in the adherence of Malassezia pachydermatis to canine corneocytes in vitro . Pretreatment of canine corneocytes with concanavalin A (10 μg ml⁻¹) inhibited ( P < 0.01) the adherence of one out of six M. pachydermatis strains. This effect was abrogated by pre-incubating concanavalin A with its hapten inhibitor (6% methyl α- d -mannopyranoside), suggesting that mannosyl-bearing carbohydrate residues on the epithelial cells serve as ligands for adhesins expressed by this strain. However, treatment of corneocytes with soybean, wheat germ and gorse lectin, and pretreatment of the yeast cells with either of the four lectins had no reproducible effect on the adherence of two strains.     

Adherence of Staphylococcus intermedius to canine corneocytes in vitro

This study investigated the in vitro adherence of Staphylococcus intermedius to canine corneocytes, collected from a healthy dog using double-sided adhesive tape. Adherence was shown to depend on duration (P < 0.001) and temperature of incubation (P < 0.001) and the concentration of bacteria (P < 0.001). Isolates of S. intermedius from lesions of pyoderma were not generally more adherent to healthy canine skin than were isolates from healthy dogs. Significant differences in adherence were demonstrated between individual isolates within both groups (P < 0.001). The study suggests that among S. intermedius there is no correlation between virulence and adherence to canine corneocytes in vitro. The finding may be important for the potential use of avirulent variants of S. intermedius as antagonistic strains against canine pyoderma. However, more studies are needed to compare the adherence of the isolates to skin cells obtained from dogs with diseases predisposed to pyoderma.     

Adherence by Staphylococcus intermedius to canine corneocytes: a preliminary study comparing noninflamed and inflamed atopic canine skin

The adherence by three strains of Staphylococcus intermedius to corneocytes collected from healthy dogs was compared to the adherence to corneocytes collected from the inflamed (erythematous) and noninflamed (normal appearing) skin of dogs suffering from atopic dermatitis. All three strains of S. intermedius adhered in greater numbers to corneocytes from both inflamed and noninflamed atopic skin than to corneocytes from healthy dogs. Adherence was greatest to corneocytes from inflamed atopic skin but one strain showed no statistical difference for adherence to inflamed and noninflamed atopic skin. These findings suggest that S. intermedius adheres extensively to both inflamed and noninflamed canine atopic skin. This may be important in the colonization of atopic skin by this microorganism. Strain variation in the ability of S. intermedius to adhere to canine atopic corneocytes is probable.     

A comparison of adherence by four strains of Staphylococcus intermedius and Staphylococcus hominis to canine corneocytes collected from normal dogs and dogs suffering from atopic dermatitis

The aim of this study was to compare the adherence of four strains of Staphylococcus intermedius and a single strain of Staphylococcus hominis to corneocytes from both normal dogs and dogs suffering from atopic dermatitis. Cells from the skin surface, corneocytes, were collected from 10 normal dogs and 10 dogs suffering from atopic dermatitis. Four strains of S. intermedius, three isolated from canine pyoderma skin lesions (strains A, B and C), and one isolated form from canine synovial membrane sample from a case of septic arthritis (strain D) were compared. S. hominis, which is not normally associated with canine disease, was also evaluated for its ability to adhere to canine corneocytes. S. hominis did not adhere to canine corneocytes. All four strains of S. intermedius adhered well to canine corneocytes collected from both normal and atopic dogs. All strains of S. intermedius showed statistically greater adherence to corneocytes collected from atopic dogs compared with those collected from normal dogs. It was concluded that the adherence assay employed here showed that S. hominis does not adhere to canine corneocytes, S. intermedius adheres preferentially to atopic corneocytes.     

Effects of bilateral arytenoid cartilage stenting on canine laryngeal resistance ex vivo

Objective: To evaluate the effect of Nitinol stents for bilateral arytenoid lateralization on canine laryngeal resistance. Study Design: Ex vivo experimental study. Animals: Canine cadaver larynges (n=7). Methods: Laryngeal resistance was calculated in all specimens with the epiglottis in open and closed positions. Bilateral arytenoid stenting was performed, rima glottidis width measured, and laryngeal resistance calculated. The effects of stenting on laryngeal resistance were evaluated by repeated measures ANOVA. Results: Calculated laryngeal resistance in the 3 stented groups, 2 cm (0.034±0.059 cmH₂O/L/s), 3 cm (0.034±0.059 cmH₂O/L/s), and 4 cm (0.034±0.059 cm H₂O/L/s), was significantly decreased versus the control (unstented) group (0.947±0.624 cmH₂O/L/s; P=.0098) with an epiglottis in the normal position. Calculated laryngeal resistance in the 3 stented groups, 2 cm (43.407±17.348 cm H₂O/L/s), 3 cm (70.659±34.705 cmH₂O/L/s), and 4 cm (92.637±44.509 cm H₂O/L/s), was significantly increased versus the control (unstented) group (29.561±14.499 cm H₂O/L/s) (P=.0185) with an epiglottis in the closed position. The width of the rima glottidis correlated with the size of the stent (r=0.95, P<.001). Conclusions: Bilateral arytenoid stenting significantly reduced calculated laryngeal resistance with an open epiglottis. Stenting resulted in a significant increase in laryngeal resistance versus the control with a closed epiglottis. Use of bilateral arytenoid stenting in clinical cases of laryngeal paralysis may provide an adequate decrease in open‐epiglottis airway resistance to alleviate clinical signs, while increasing closed‐epiglottis airway resistance. This could potentially lead to a decrease in the risk of postoperative aspiration pneumonia.     

Staphylococcus pseudintermedius exfoliative toxin EXI selectively digests canine desmoglein 1 and causes subcorneal clefts in canine epidermis

Staphylococcal exfoliative toxins are known to digest desmoglein (Dsg) 1, a desmosomal cell–cell adhesion molecule, thus causing intraepidermal splitting in human bullous impetigo, staphylococcal scalded skin syndrome and swine exudative epidermitis. Recently, a novel exfoliative toxin gene (exi), whose sequence shares significant homology with previously identified exfoliative toxins, was isolated from Staphylococcus pseudintermedius. Little is known about the pathogenic involvement of this toxin in canine pustular diseases such as impetigo. The aim of this study was to determine whether EXI, the product of the exi gene, digests canine Dsg1 and causes intraepidermal splitting in canine skin. An exi gene was isolated from chromosomal DNA of an S. pseudintermedius strain obtained from a pustule of a dog with impetigo, and was used to produce a recombinant EXI by Escherichia coli expression. When purified recombinant EXI was injected intradermally into normal dogs, it caused the development of vesicles or erosions with superficial epidermal splitting. In addition, the EXI abolished immunofluorescence for Dsg1, but not for Dsg3, at the injection sites. Moreover, the EXI directly degraded baculovirus‐secreted recombinant extracellular domains of canine Dsg1, but not that of canine Dsg3, in vitro. The EXI also degraded mouse Dsg1α and swine Dsg1, but not human Dsg1, mouse Dsg1β and Dsg1γ. Conversely, recombinant SIET, previously designated as S. intermedius exfoliative toxin, did not cause intraepidermal splitting or degradation of any Dsgs. These findings indicate that EXI has a proteolytic activity that digests canine Dsg1, and this characteristic might be involved in the pathogenesis of intraepidermal splitting in canine impetigo.     

In vitro and ex vivo inhibition of canine cyclooxygenase isoforms by robenacoxib: A comparative study

In vitro whole blood canine assays were used to quantify the inhibitory actions of the novel non-steroidal anti-inflammatory drug (NSAID) robenacoxib on the cyclooxygenase (COX) isoenzymes, COX-1 and COX-2, in comparison with other drugs of the NSAID class. COX-1 activity was determined by measuring serum thromboxane (Tx)B₂ synthesis in blood samples allowed to clot at 37 °C for 1 h. COX-2 activity was determined by measuring prostaglandin (PG)E₂ synthesis in blood samples incubated at 37 °C for 24 h in the presence of lipopolysaccharide. The rank order of selectivity for inhibition of COX-2 versus COX-1 (IC₅₀ COX-1:IC₅₀ COX-2) for veterinary drugs was highest with robenacoxib (128.8) compared to deracoxib (48.5), nimesulide (29.2), S+ carprofen (17.6), meloxicam (7.3), etodolac (6.6), R? carprofen (5.8) and ketoprofen (0.88). Selectivity expressed as the clinically relevant ratio IC₂₀ COX-1:IC₈₀ COX-2 was highest for robenacoxib (19.8) compared to deracoxib (2.3), S+ carprofen (2.5), R? carprofen (2.1), nimesulide (1.8), etodolac (0.76), meloxicam (0.46) and ketoprofen (0.21).An in vivo pharmacokinetic ex vivo pharmacodynamic study in the dog established dosage and concentration–effect relationships for single oral doses of robenacoxib over the dosage range 0.5–8.0 mg/kg. Values of C_max and AUC were linearly related to dosage over the tested range. Robenacoxib did not inhibit serum TxB₂ synthesis (COX-1) ex vivo at dosages of 0.5–4.0 mg/kg and produced only transient inhibition (at the 1 h and 2 h sampling times) at the 8 mg/kg dosage. All dosages of robenacoxib (0.5–8 mg/kg) produced marked, significant and dose related inhibition of PGE₂ synthesis (COX-2) ex vivo.The data demonstrate that in the dog robenacoxib is a highly selective inhibitor of the COX-2 isoform of COX, and significantly inhibits COX-2 and spares COX-1 in vivo when administered orally over the dosage range 0.5–4.0 mg/kg.     

The role of rituximab in the treatment of canine lymphoma: an ex vivo evaluation

Targeting the CD20 receptor that is common to many B-cell Non-Hodgkin's Lymphoma subtypes in people, rituximab is a chimeric monoclonal antibody which has significantly improved disease-free survival rates compared with the use of cytotoxic agents alone. This study evaluated ex vivo canine B cell binding and depletion by rituximab with flow cytometric technique as possible proof of concept for treatment of canine lymphoma. Despite immunohistochemistry supporting CD20 expression, rituximab did not bind or deplete canine B cells and it is unlikely that it will be added to the armamentarium of treatment options for canine lymphoma.     

Development of an ex vivo model to study adherence of Mannheimia haemolytica serovar 1 to mucosal tissues of the respiratory tract of cattle

OBJECTIVE: To develop and validate an ex vivo model for study of adherence of Mannheimia haemolytica (formerly Pasteurella haemolytica) to respiratory tract mucosa of cattle and to use this model to confirm adherence of M haemolytica serovar 1 (Mh1) to several relevant respiratory mucosal surfaces. SAMPLE POPULATION: Excised nasal, nasopharyngeal, turbinate, and tonsillar mucosal tissue from the bovine upper respiratory tract. PROCEDURE: Mh1 was radiolabeled by use of tritiated leucine. Various concentrations of labeled bacteria were incubated with bovine upper respiratory tract tissues for various times. Tissue was washed to remove nonadherent bacteria, and percentage of bacteria adhered (percentage of adherence) was estimated using radioactivity. Using an optimal inoculum concentration and incubation time, percentage of Mh1 adherence was compared on nasal, nasopharyngeal, turbinate, and tonsillar mucosal tissue, and adherence to nasopharyngeal tissue was confirmed by scanning and transmission electron microscopy. RESULTS: The optimal Mh1 inoculum concentration was 1 X 10(7) colony forming units/ml and incubation time was 3 hours. Percentage of adherence of Mh1 to nasopharyngeal tissue was greater than adherence to other tissue types. CONCLUSIONS AND CLINICAL RELEVANCE: The ex vivo model maintained the functional and structural integrity of bovine upper respiratory tract mucosa, as confirmed by light and electron microscopy. Electron microscopy revealed participation of epithelial cell cilia and surface mucus in adherence of Mh1 to nasopharyngeal tissue. Adherence of Mh1 was confirmed in repeated assays, indicating that this organism adheres to upper respiratory tract mucosa of cattle.