Resistance of some capsular serotype D strains of Pasteurella multocida to rabbit polymorphonuclear neutrophil phagocytosis.

The mechanism of resistance of Capsular Type D strains of Pasteurella multocida to killing by rabbit polymorphonuclear neutrophils (PMN) was studied using an in vitro assay that differentiates intra- from extracellular bacteria. Two Capsular Type D strains (3761 and 3766), resistant to killing by rabbit PMN, and one Type A strain (R1), susceptible to PMN destruction, were compared. After combining opsonized bacteria and PMN, the Capsular Type D Strains 3761 and 3766 remained extracellular while the Capsular Type A Strain R1 was internalized by PMN. Thus, both Type D strains were resistant to phagocytosis by rabbit PMN.

A method to detect rabbit neutrophil phagocytosis of Pasteurella multocida.

A method was developed to detect neutrophil phagocytosis of bacteria by determining whether neutrophil-associated bacteria were intra- or extracellular. Neutrophils were treated with 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride to inhibit degranulation and, consequently, killing of bacteria. Treated neutrophils and opsonized Pasteurella multocida were combined. Following phagocytosis, the suspensions were centrifuged and the pellets were washed to remove non-cell-associated bacteria. The pellets were resuspended and heparin was added to prevent further phagocytosis. Samples were removed, and the number of viable bacteria was determined by a dilution and plate count technique. Streptomycin, an antibiotic that is poorly taken up by neutrophils, was added to kill extracellular bacteria, and the suspensions were incubated for 20 minutes at 37 C, and samples were removed again and bacterial numbers were determined. Percentage killing of bacteria by streptomycin was calculated. Phagocytosed bacteria were protected from the bactericidal action of streptomycin.

Strain differences in the susceptibility and resistance of Pasteurella multocida to phagocytosis and killing by rabbit polymorphonuclear neutrophils.

The interactions of 2 capsular serotype A and 4 serotype D strains of Pasteurella multocida with rabbit polymorphonuclear neutrophils (PMN) were compared in vitro, using a PMN phagocytic and bactericidal assay. Bacteria and rabbit PMN were incubated for 15 minutes. The suspensions were subjected to differential centrifugation and the percentage of phagocytosis (cell association) was determined from the number of viable noncell-associated bacteria. The cell pellets and the associated bacteria were resuspended and PMN bactericidal activity was calculated from the number of remaining viable cell-associated bacteria at 45 and 75 minutes after the start of the assay. Test bacteria were not opsonized or were opsonized with immune serum containing active complement. One type A strain was ingested and killed by PMN in the presence and absence of opsonins. The 5 remaining strains were resistant to PMN killing, but only the type A strain resisted phagocytosis. Resistance of the type A strain was attributed to the hyaluronic acid capsule, since pretreatment of the bacteria with hyaluronidase rendered opsonized bacteria susceptible to ingestion and killing. The pattern of resistance of the 4 type D strains was different from that of the resistant type A strain. Both opsonized and nonopsonized type D bacteria became cell associated, but none were killed by PMN. The mechanism of resistance of these 4 strains to PMN bactericidal activity is currently unknown.

In vitro killing of Pasteurella multocida: the effect of rabbit granulocyte and specific antibody source.

In vitro granulocyte-killing assays were performed to examine the ability of granulocytes from pasteurella-free or immunized rabbits, the in combination with specific immune serum, to kill Pasteurella multocida. Granulocytes from healthy rabbits and from rabbits with P multocida infections were equally competent. Granulocyte source, serum source, and specific antibody titer had no effect on granulocyte phagocytic activity. Moreover, serum containing specific antibody and complement supported the growth of the bacterium. These data suggest that chronic P multocida infections are not attributable to defective granulocytes or lack of serum antibody production.

Resistance of Pasteurella multocida to rabbit neutrophil phagocytosis and killing.

The susceptibilities of several Pasteurella multocida strains to serum bactericidins and to killing by rabbit polymorphonuclear neutrophils (PMN) were investigated, using in vitro assays. Strain Bunia II (serotype 5,12:E) was killed by both immune and normal rabbit sera containing active complement, and strains R1 (serotype 3,12:A) and 656 (serotype 12:B) were serum resistant. Strain R1 opsonized with immune or normal rabbit serum with complement or with immune antibody alone was phagocytized by neutrophils, and strain 656 was ingested only after opsonization with immune antibody in the presence or absence of complement. Complement alone was ineffective as an opsonin for the last 2 serotypes. Neither isolate was resistant to PMN killing. Growth of strain R1 in subcutaneously implanted chambers in rabbits did not increase the resistance of this organism to PMN. Comparison of phagocytosis and killing of this isolate with 2 virulent rabbit strains of P multocida--strains L-A (serotype 12:A) and 7228 (serotype 14:D)--demonstrated that strain L-A was resistant to destruction by neutrophils, whereas strains 7228 and R1 were killed. Resistance of strain L-A was not associated with the hyaluronic acid capsule.

Pseudomonas aeruginosa infection in a Chinchilla lanigera.

This report describes a case of Pseudomonas aeruginosa infection in a chinchilla. The affected animal displayed a variety of clinical signs including genital swelling, conjunctivitis, anorexia, weight loss, corneal and oral ulcerations and, most unusually, intradermal pustules which developed 8 days after recovery from the initial illness. The occurrence of these pustules has not been documented previously.

Management of septicemia in rhesus monkeys with chronic indwelling venous catheters.

Twenty venous-catheterized, septicemic rhesus monkeys from two laboratories were studied. The most common isolates from the bloodstream were Klebsiella oxytoca from the monkeys in one laboratory and Staphylococcus aureus from those in the other. Five septicemic monkeys from the two laboratories, each with a central venous catheter, received repeated courses of antibiotics to which the infecting organisms were sensitive. Their catheters, however, were not removed. All five monkeys improved clinically, permitting continued use of the catheters. However, until the catheters were removed, bacteria were isolated repeatedly from the bloodstream. Two therapeutic regimens for the management of bacterial septicemia then were compared. Under both regimens, animals with positive blood cultures were treated for 10 days with appropriate antibiotics based on bacterial sensitivity testing. In one group of 10 monkeys, the indwelling venous catheters remained in situ during treatment. In a second group of 10 monkeys, catheters were removed at the time antibiotic therapy was initiated. When catheters were not removed, septicemia recurred 3 to 5 days after antibiotics were discontinued. In contrast, when catheter removal accompanied antibiotic therapy, resolution of the septicemia occurred within 3 to 5 days. Thus, catheter removal was required for elimination of bacteria from the bloodstream of septicemic monkeys with long-term indwelling central venous catheters.

Infection of white carneaux pigeons (Columbia livia) with Mycobacterium avium.

Avian tuberculosis, caused by Mycobacterium avium, occurred in three White Carneaux pigeons. Clinical signs varied and included anorexia, lameness, torticollis, and the development of cutaneous nodules. Lesions at necropsy consisted of caseating hepatic, pulmonary, and cutaneous granulomas. In one animal, the marrow in several bones was replaced with caseous material. Histopathologically, the granulomas contained necrotic material and acid fast bacilli surrounded by epitheloid cells, giant cells, and lymphocytes. Treatment of affected animals was not attempted. False positive and false negative reactions occurred when intradermal tuberculin skin testing was done.

Dermatophilosis in the marble lizard (Calotes mystaceus).

Dermatophilus congolensis was isolated from cutaneous hyperkeratotic nodules of two marble lizards. The organism was similar to strains of D congolensis previously characterized as mammalian pathogens. The isolate was experimentally transmitted to other marble lizards and to Spb:(SW)BR mice by subcutaneous inoculation and by topical application after skin scarification.

An enzyme-linked immunosorbent assay to detect serum IgG to Pasteurella multocida in naturally and experimentally infected rabbits.

An enzyme-linked immunosorbent assay (ELISA) was evaluated for efficacy in detecting serum IgG against Pasteurella multocida in both naturally and experimentally infected rabbits. Blood samples and nasal cultures were taken concurrently from 58 rabbits from four conventional rabbitries. Nine rabbits from a pasteurella-free colony served as negative controls. Fifty-six rabbits were ELISA positive. Of these, 46 were P. multocida culture positive, 10 were culture negative. Two rabbits were ELISA negative, culture negative. There were no ELISA negative, culture positive animals. Serotyping by the gel diffusion precipitin test demonstrated that of the 44 typed P. multocida isolates, 57% were serotype 4, 27% were serotype 12 and 16% were serotype 3. In rabbits experimentally infected intranasally with P. multocida, serum IgG against P. multocida began to rise 21 to 33 days after infection and remained elevated until the animals were euthanized 90 days post infection. Two enzyme-linked immunosorbent assays were compared which used potassium thiocyanate extracts of different serotypes of P. multocida as antigen. The results obtained were similar, suggesting the presence of antigens common to both serotypes.

Nephrotoxicity of tiletamine in New Zealand white rabbits.

Tiletamine and zolazepam, the two constituents of Telazol, were evaluated independently to determine which agent was responsible for the nephrotoxicity caused by Telazol in New Zealand White rabbits. Five rabbits were injected i.m. with 32 mg/kg of tiletamine, four animals received 7.5 mg/kg of tiletamine, and five rabbits received 32 mg/kg of zolazepam. Urinalysis was performed and blood urea nitrogen and serum creatinine were monitored for 7 days postinjection. In all five rabbits injected with the high dose of tiletamine, blood urea nitrogen and creatinine rose by 3 days postinjection and increased steadily throughout the week. By 4 days postinjection, urine protein and glucose were elevated and cellular and protein casts were present. No serum chemistry or urine abnormalities were detected in rabbits receiving low doses of tiletamine, zolazepam, or in the four control rabbits. All animals were euthanized and necropsied at 7 days postinjection. Histopathology showed severe renal tubular necrosis in all five rabbits injected with 32 mg/kg tiletamine. Mild nephrosis was present in three of four rabbits injected with 7.5 mg/kg of tiletamine. No lesions were present in the zolazepam-injected or control rabbits. The results of this study show that tiletamine is the constituent responsible for the nephrotoxicity of Telazol in rabbits. They further demonstrate that doses commonly used for anesthetic induction or restraint can produce renal lesions in rabbits.

Pasteurella associated rhinitis of rabbits: efficacy of penicillin therapy.

Thirty adult New Zealand white rabbits with chronic rhinitis were obtained from a commercial breeding colony. Penicillin sensitive strains of Pasteurella multocida were isolated from the upper respiratory tract of 28 (93%) of these rabbits. The diseased rabbits were treated with either intramuscular penicillin or penicillin nasal spray for 10 days and monitored for clinical signs of rhinitis and for the presence of Pasteurella multocida in the nasal passages. Rabbits receiving penicillin therapy by either route showed significant remission of the clinical signs of rhinitis during the study period; however, following treatment there was not significant difference in the prevalence of rhinitis between the treated groups and the untreated group. This was due in part to the considerable but non-significant improvement shown by the untreated group. This improvement which was not due to penicillin therapy may have been due to stabilization of environmental factors. The prevalence of Pasteurella multocida in the upper respiratory tracts of either the treated or untreated rabbits did not change significantly during the study period.

Anesthetic and nephrotoxic effects of Telazol in New Zealand white rabbits.

Telazol was evaluated as an anesthetic for rabbits. Two groups of five rabbits each were injected intramuscularly with 32 or 64 mg/kg of Telazol, and the depth and duration of anesthesia period monitored. At both doses, the righting reflex was lost within 2 minutes postinjection. Animals in both groups responded to noxious stimuli for the duration of the anesthesia. Hematology and urinalyses were performed daily for 7 days postinjection. Hematologic parameters remained unchanged in both groups. In the high-dose group, blood urea nitrogen and serum creatinine levels increased 1 day postinjection and continued steadily throughout the week. Elevations in urine protein and the presence of casts correlated with this increase. In the low-dose group, blood urea nitrogen and creatinine levels increased and protein was present in the urine of four of five rabbits beginning approximately 5 days postinjection. Histologically, severe renal tubular necrosis was evident 7 days postinjection in all high-dose rabbits and in three rabbits in the low-dose group. Our results indicate that Telazol does not produce analgesia in rabbits and is nephrotoxic at both 32 and 64 mg/kg. We conclude that Telazol is contraindicated for use in rabbits.

Adhesion of type A Pasteurella mulocida to rabbit pharyngeal cells and its possible role in rabbit respiratory tract infections.

Pasteurella multocida serotype A was found in association with the mucosal epithelium of the nasopharynges of rabbits with respiratory tract infections. The bacteria specifically attached to squamous epithelial cells of the pharyngeal mucosa both in vivo and in vitro and to some tissue culture cell lines such as HeLa. All strains with serotype A capsules were adhesive. With the exception of one serotype D strain, strains with capsular serotypes B, D, and E were at least 10-fold less adhesive. Bacterial adhesiveness was much reduced after pronase digestion, heat treatment, and homogenization, but removal of the hyaluronic acid capsule increased adhesion. Electron microscopy revealed that fimbriae were produced by an adhesive pasteurella strain, but not by two nonadherent strains. The attachment of the former strain to pharyngeal and HeLa cells was inhibited by N-acetyl-D-glucosamine. Together, these findings suggest that this amino sugar may be a component of the receptor on both animal cell surfaces and that the fimbriae may be the adhesions. It is proposed that bacterial attachment has a role in colonization and infection of rabbit upper respiratory mucosae.

Cryptosporidiosis in guinea pigs: an animal model.

Cryptosporidia from natural cryptosporidiosis in guinea pigs were experimentally transmitted to both adult and juvenile guinea pigs. Cryptosporidia were associated with the villi of the ileum, jejunum, and duodenum. Both juveniles and adults were equally susceptible to cryptosporidia, as determined by decreases in villus height, increases in crypt depth, and decreases in villus height/crypt depth ratios, when compared with uninoculated animals. When multiple paired comparisons were made between 2 and 10 days postinoculation, there were significant decreases in villus height/crypt depth ratios with time. A dose study showed that 6-week-old guinea pigs were all infected with doses as low as 325 oocysts per animal. When sampled at weekly intervals postinoculation, guinea pigs had significant evidence of infection up to 2 weeks but had recovered completely by 4 weeks. Guinea pigs mounted a specific humoral immune response against cryptosporidia, as measured by an immunoperoxidase technique. Guinea pigs challenged by reinoculation with cryptosporidial oocysts were completely refractory to reinfection. These studies show that cryptosporidiosis in guinea pigs is a useful small animal model of this disease.

Oxytetracycline-induced nephrotoxicosis in dogs after intravenous administration for experimental bone labeling.

Tetracyclines have been used as in vivo indicators of new bone formation because they form complexes with mineral at bone-forming surfaces. Four of 12 dogs in a bone-labeling study developed clinical signs of renal disease (vomiting, diarrhea, dehydration, and azotemia) within 1 to 2 days of receiving oxytetracycline at a bone-labeling dose of 25 mg/kg of body weight, once daily for 2 consecutive days. To delineate the relationship between oxytetracycline administration and renal damage, six dogs were given the bone-labeling dose intravenously and were subsequently evaluated by determination of clinical signs, serum biochemical analysis, urinalysis, and histologic examination (experiment 1). Drug administration was modified in the five dogs remaining in the bone-labeling orthopedic study. These dogs received the oxytetracycline dose as a slow intravenous infusion diluted with 250 ml of lactated Ringer's solution (experiment 2). All six dogs of experiment 1 developed persistent isosthenuria within 2 days of receiving the bone-labeling dose of oxytetracycline. Clinical illness (three of six dogs) was associated with azotemia, creatinemia, and hyperphosphatemia. All dogs had multifocal, mild to moderate flattening of renal tubular epithelium, characteristic of nephrosis. None of the dogs of experiment 2 developed any clinical indications of renal disease, and the only biochemical abnormality was isosthenuria in two of the five dogs. Thus the development of clinical signs and biochemical abnormalities associated with the intravenous administration of oxytetracycline was obviated by the slow administration of a dilution of the calculated bone-labeling dose of the antibiotic.