Dietary L-glutamine supplementation increases Pasteurella multocida burden and the expression of its major virulence factors in mice.

This study was conducted to determine the effects of graded doses of L-glutamine supplementation on the replication and distribution of Pasteurella multocida, and the expression of its major virulence factors in mouse model. Mice were randomly assigned to the basal diet supplemented with 0, 0.5, 1.0 or 2.0 % glutamine. Pasteurella multocida burden was detected in the heart, liver, spleen, lung and kidney after 12 h of P. multocida infection. The expression of major virulence factors, toll-like receptors (TLRs), proinflammatory cytokines (interleukin-1 beta, interleukin-6, and tumor necrosis factor alpha) and anti-oxidative factors (GPX1 and CuZnSOD) was analyzed in the lung and spleen. Dietary 0.5 % glutamine supplementation has little significant effect on these parameters, compared to those with basal diet. However, results showed that a high dose of glutamine supplementation increased the P. multocida burden (P < 0.001) and the expression of its major virulence factors (P < 0.05) as compared to those with a lower dose of supplementation. In the lung, high dose of glutamine supplementation inhibited the proinflammatory responses (P < 0.05) and TLRs signaling (P < 0.05). In the spleen, the effect of glutamine supplementation on different components in TLR signaling depends on glutamine concentration, and high dose of glutamine supplementation activated the proinflammatory response. In conclusion, glutamine supplementation increased P. multocida burden and the expression of its major virulence factors, while affecting the functions of the lung and spleen.

Dual infection with Pneumocystis carinii and Pasteurella pneumotropica in B cell-deficient mice: diagnosis and therapy.

BACKGROUND AND PURPOSE: The clinical presentation, diagnosis, histopathologic findings, and elimination of dual respiratory tract infection with Pasteurella pneumotropica and Pneumocystis carinii were studied in 100 adult barrier-reared C.B17 and MRL- lpr mice homozygous for a targeted mutation of the JH region of the immunoglobulin heavy chain. METHODS: Necropsy, aerobic bacteriologic culture of hematogenous and pulmonary tissues, histochemical staining of pulmonary tissues, polymerase chain reaction analysis of pulmonary tissues and feces, and viral serologic testing were performed on 19 clinically affected mice and 8 clinically normal mice, then later on antibiotic-treated and caesarian re-derived mice. Therapeutic strategies included sequential administration of trimethoprim/ sulfamethoxazole and enrofloxacin or enrofloxacin administration and caesarian rederivation. RESULTS: Clinically affected mice had diffuse, nonsuppurative, interstitial pneumonia with superimposed pyogranulomatous lobar pneumonia that was detected microscopically. Affected lung tissue yielded pure culture of P. pneumotropica. Aged-matched, clinically normal mice of both genotypes had interstitial histiocytic pneumonia without lobar pneumonia, and P. pneumotropica was not isolated. Histochemical staining of lung tissues from normal and clinically affected mice revealed scattered cysts consistent with P. carinii, principally in the interstitium. Treatment with sulfamethoxazole/trimethoprim and enrofloxacin eliminated bacteriologic detection of P. pneumotropica, decreased mortality from 50% to 6%, and improved breeding performance. CONCLUSION: A successful antibiotic therapy and rederivation approach, incorporating enrofloxacin, cesarian section, and isolator rearing, was developed for B cell-deficient mice with opportunistic infections.

Species selectivity of new siderophore-drug conjugates that use specific iron uptake for entry into bacteria.

Siderophores selectively bind ferric iron and are involved in receptor-specific iron transport into bacteria. Several types of siderophores were synthesized, and growth-promoting or inhibitory activities when they were conjugated to carbacephalosporin, erythromycylamine, or nalidixic acid were investigated. Overall, 11 types of siderophores and 21 drug conjugates were tested against seven different bacterial species: Escherichia coli, Bordetella bronchiseptica, Pasteurella multocida, Pasteurella haemolytica, Streptococcus suis, Staphylococcus aureus, and Staphylococcus epidermidis. In some species, the inhibitory activities of the drug conjugates were associated with the ability of the bacteria to use the siderophore portion of the molecules for growth promotion in disc diffusion tests (0.04 mumol of conjugate or siderophore per disc). E. coli used catechol-based siderophore portions as well as hydroxamate-based tri-delta-OH-N-OH-delta-N-acetyl-L-ornithine ferric iron ligands for growth under iron-restricted conditions achieved by supplemental ethylenediamine di (O-hydroxyphenylacetic acid) (100 micrograms/ml) and was sensitive to carbacephalosporin conjugated to these siderophore types (up to a 34-mm-diameter inhibition zone). B. bronchiseptica used desferrioxamine B and an isocyanurate-based or trihydroxamate in addition to catechol-based siderophore portions for promotion but was not inhibited by beta-lactam conjugates partly because of the presence of beta-lactamase. P. multocida and P. haemolytica did not use any of the synthetic siderophores for growth promotion, and the inhibitory activities of some conjugates seemed partly linked to their ability to withhold iron from these bacteria, since individual siderophore portions showed some antibacterial effects. Individual siderophores did not promote S. suis growth in restrictive conditions, but the type of ferric iron ligands attached to beta-lactams affected inhibitory activities. The antibacterial activities of the intracellular-acting agents erythromycylamine and nalidixic acid were reduced or lost, even against S. aureus and S. epidermidis, when the agents were conjugated to siderophores. Conjugate-resistant E. coli mutants showed the absence of some iron-regulated outer membrane proteins in gel electrophoresis profiles and in specific phage or colicin sensitivity tests, implying that the drugs used outer membrane receptors of ferric complexes to get into cells.