SipA, SopA, SopB, SopD and SopE2 effector proteins of Salmonella enterica serovar Typhimurium are synthesized at late stages of infection in mice

Salmonella pathogenicity island (SPI)-1 is essential for invasion of non-phagocytic cells, whereas SPI-2 is required for intracellular survival and proliferation in phagocytes. Some SPI-1 effectors, however, are induced upon invasion of both phagocytic and non-phagocytic cells, suggesting that they may also be required post-invasion. In the present work, the presence was analysed of SipA, SopA, SopB, SopD and SopE2 effector proteins of Salmonella enterica serovar Typhimurium in vitro and in vivo during murine salmonellosis. Tagged (3xFLAG) strains of S. enterica serovar Typhimurium were inoculated intraperitoneally or intragastrically to BALB/c mice and recovered from the spleen and mesenteric lymph nodes of moribund mice. Tagged proteins were detected by SDS-PAGE and immunoblotting with anti-FLAG antibodies. In vitro experiments showed that SPI-1 effector proteins SipA, SopA, SopB, SopD and SopE2 were secreted under SPI-1 conditions. Interestingly, it was found that S. enterica serovar Typhimurium continued to synthesize SipA, SopB, SopD and SopE2 in colonized organs for several days, regardless of the route of inoculation. Together, these results indicate that SPI-1 effector proteins may participate in the late stages of Salmonella infection in mice.

Nitric oxide and apoptosis induced in Peyer's patches by attenuated strains of Salmonella enterica serovar Enteritidis

Nitric oxide (NO) is a toxic molecule of the immune system which contributes to the control of microbial pathogens. Additional functions of NO in innate and adaptive immunity have recently been described; these functions include the modulation of the cytokine response of lymphocytes and the regulation of immune cell apoptosis. In addition to direct microbicidal actions, NO has immunoregulatory effects relevant to the control of infections. In turn, infected macrophages and macrophage-regulating lymphocytes may undergo apoptosis during infection by Salmonella spp. In this work we investigated the ability of attenuated strains of Salmonella enterica serovar Enteritidis with different protective capacities to induce intestinal inducible nitric oxide synthase (iNOS) and apoptosis in Peyer's patches (PP) in mice. Results showed that the intestinal iNOS activity correlated with increased apoptosis in PP. Furthermore, the ability to induce intestinal NO production and apoptosis within the first few hours after immunization seemed to correlate with the protective capacity of mutant E/1/3 of S. enterica serovar Enteritidis. It was found that nonprotective mutant C/2/2, which was unable to induce intestinal NO production, also failed to induce apoptosis in PP. Moreover, aminoguanidine treatment at the time of immunization resulted in inhibition of the NO production and apoptosis induced by protective mutant E/1/3 and completely abolished protection against challenge. These results suggest that the induction of iNOS in the intestinal mucosa by attenuated mutant E/1/3 of S. enterica serovar Enteritidis at the time of immunization is necessary to generate a protective immune response.

Salmonella enteritidis temperature-sensitive mutants protect mice against challenge with virulent Salmonella strains of different serotypes

The protection conferred by temperature-sensitive mutants of Salmonella enteritidis against different wild-type Salmonella serotypes was investigated. Oral immunization with the single temperature-sensitive mutant E/1/3 or with a temperature-sensitive thymine-requiring double mutant (E/1/3T) conferred: (i) significant protection against the homologous wild-type Salmonella strains; (ii) significant cross-protection toward high challenge doses of S. typhimurium. Significant antibody levels against homologous lipopolysaccharide and against homologous and heterologous protein antigens were detected in sera from immunized mice. Moreover, a wide range of protein antigens from different Salmonella O serotypes were recognized by sera from immunized animals. Besides, primed lymphocytes from E/1/3 immunized mice recognized Salmonella antigens from different serotypes. Taken together, these results indicate that temperature-sensitive mutants of S. enteritidis are good candidates for the construction of live vaccines against Salmonella.

Orally administered attenuated Salmonella enteritidis reduces chicken cecal carriage of virulent Salmonella challenge organisms

Chickens were immunized orally with 10(9)cfu of the temperature-sensitive (T(s)) mutant E/1/3 of Salmonella enteritidis at 1, 2, 3 and 7 days of age. The animals were challenged with wild-type strains of Salmonella of different serotypes 7 or 14 days following immunization. Chickens receiving multiple oral doses of the vaccine strain showed no signs of disease. Immunized animals shed the vaccine strain for at least 2 weeks after the last inoculation; on the other hand, colonization by the attenuated mutant of internal organs such as spleen and liver was limited. Early exposure of the immunized animals to the virulent bacteria resulted in a reduced cecal colonization by the pathogen. Visceral invasion by the wild-type strain of S. enteritidis or S. gallinarum was drastically diminished in birds challenged 14 days after immunization. Significant differences in the number of these Salmonella were found in the cecal contents, spleen and liver of immunized birds compared with the control animals. In addition, cecal colonization by the virulent strain was reduced in birds challenged with S. typhimurium. These results demonstrate that immunization of newly hatched chickens with live attenuated T(s) mutant E/1/3 of S. enteritidis is safe and reduces Salmonella shedding.

Vaccination of chickens with a temperature-sensitive mutant of Salmonella enteritidis

One-day old chickens were inoculated with temperature-sensitive mutant E/1/3 of S. enteritidis. Two routes of inoculation were used: oral and intraperitoneal (ip). One group of chickens were given two oral inoculations (oral-oral). A second group received two ip inoculations (ip-ip). A third group received the first dose orally and the second ip (oral-ip) and the fourth group was given the first dose ip and the second dose orally (ip-oral). The vaccine strain was safe even when inoculated at high doses, and induced strong protection against virulent S. enteritidis strain after oral challenge. Results show that vaccination with mutant E/1/3 reduced the number of animals shedding the pathogen after challenge. Furthermore, animals immunized oral-oral and oral-ip showed a significant reduction in cecal and spleen colonization by virulent Salmonella.

Attenuated mutants of Staphylococcus aureus with two temperature-sensitive lesions: isolation and characterization

The feasibility of constructing attenuated mutants of Staphylococcus aureus with two temperature-sensitive (ts) lesions for ultimate development of a live-attenuated strain was investigated. Temperature-sensitive S. aureus strain G/1/2, which grows well at 31 degrees C but does not replicate at 37 degrees C, was subjected to chemical mutagenesis. After two enrichment cycles, fifteen mutants able to grow at 25 degrees C but unable to grow at 31 degrees C, were identified. Growth curves with temperature shifts from 25 to 31 degrees C, and from 31 to 37 degrees C confirmed that these were mutants with two lesions (dts), each with a different cut-off temperature. The reversion frequency of mutant G/1/2 at 37 degrees C was 2 x 10(-6) whereas those of several dts mutants were much lower (dts7: 7 x 10(-9) and dts12: 1 x 10(-9)). There was no increase in ts mutation reversion rate in response to prolonged incubation at 37 degrees C. The data support the further development of these mutants for use as a stable attenuated vaccine.

A temperature-sensitive DNA adenine methyltransferase mutant of Salmonella typhimurium

A temperature-sensitive mutant of Salmonella typhimurium was isolated earlier after transposon mutagenesis with Tn10d Tet. The mutant D220 grows well at 28 degreesC but has a lower growth rate and forms filaments at 37 degreesC. Transposon-flanking fragments of mutant D220 DNA were cloned and sequenced. The transposon was inserted in the dam gene between positions 803 and 804 (assigned allele number: dam-231 : : Tn10d Tet) and resulted in a predicted ten-amino-acid-shorter Dam protein. The insertion created a stop codon that led to a truncated Dam protein with a temperature-sensitive phenotype. The insertion dam-231 : : Tn10d Tet resulted in a dam "leaky" phenotype since methylated and unmethylated adenines in GATC sequences were present. In addition, the dam-231 : : Tn10d Tet insertion rendered dam mutants temperature-sensitive for growth depending upon the genetic background of the S. typhimurium strain. The wild-type dam gene of S. typhimurium exhibited 82% identity with the Escherichia coli dam gene.

Intramammary immunization with live-attenuated Staphylococcus aureus protects mice from experimental mastitis

Female mice were immunized by the intramammary route with live-attenuated Staphylococcus aureus according to different schedules and challenged with virulent S. aureus. Immunization in late pregnancy or early lactation induced a significant decrease (P <0.05) in the number of S. aureus CFU recovered from glands after the challenge and a significant increase (P <0.05) in the levels of milk and serum specific IgG and IgA antibodies. Mice immunized before pregnancy were not protected from S. aureus challenge. Immunization did not increase the number of somatic cells in milk when compared with control mice. Protection from S. aureus intramammary infection may be achieved if mice are locally immunized during late pregnancy or early lactation.

Intramammary immunization with live-attenuated Staphylococcus aureus: microbiological and immunological studies in a mouse mastitis model

Mammary infection was induced in lactating mice by intramammary injection of Staphylococcus aureus. Histopathological analysis revealed infiltration and lesions of varying magnitude that were still apparent 21 days after the challenge. Concomitantly, viable S. aureus was recovered from infected mammary glands. Mice were immunized by the intramammary route with 5 x 10(6) colony forming units of a temperature-sensitive mutant of S. aureus and subsequently received a boosting injection seven days later. On day 14 mice were challenged by the intramammary route with the wild-type strain. Intramammary immunization induced a significant increase in milk IgA (P < 0.05), serum IgG (P < 0.05) and serum IgA (P < 0.05) on the day of the challenge, when compared with non-immunized mice. Immunization decreased significantly (P < 0.01) the number of S. aureus colony forming units recovered 96 h after intramammary challenge. In conclusion, the feasibility of immunizing locally with temperature-sensitive S. aureus to induce immunity in the mouse mammary gland was demonstrated. The mouse model of mastitis is proposed as a useful system for screening temperature-sensitive S. aureus strains to be utilized in the development of a vaccine.

Fts insertional mutant of Salmonella typhimurium

A temperature-sensitive filamentation (fts) Salmonella typhimurium mutant was isolated after transposon mutagenesis with mini-Tn 10dTc. The mutant was unable to form colonies after 20 h incubation at 37 degrees C on LB agar. Colonies appeared, however, after longer incubation at the restrictive temperature. Filamentation affected only part of the bacterial population. Rapid mapping using Mu dP22 hybrid phages revealed that the mutation, ftsD220, lies within minutes 68.5 and 73.6 on the genetic map. Further analysis revealed that the ftsD220 mapped at min 73 and that it is linked to cysG (6%) and to aroB (39%). Complementation tests suggested that the ftsD220 mutation is not homologous to a Escherichia coli ftsH mutation.

Interaction between granulocytes and antibodies in the enhancement of lung defenses against Staphylococcus aureus after intranasal immunization of mice with live-attenuated bacteria

Immunization with live-attenuated Staphylococcus aureus induced measurable levels of specific IgG and IgA in the lungs, but the pulmonary clearance of S. aureus in immunized mice did not differ from that of control mice. Aerosol exposure of mice to Pseudomonas aeruginosa induced a significant recruitment of polymorphonuclear leukocytes (PMNL) to the lungs in both immunized and control mice, whereas S. aureus challenge did not. However, challenge with a mixture of P. aeruginosa-S. aureus or exposure to an aerosol of Escherichia coli lipopolysaccharide (LPS) before S. aureus challenge induced PMNL migration and a significant enhancement of pulmonary clearance of S. aureus in immunized mice. The presence of both antibodies and PMNL was required for enhancement of S. aureus pulmonary clearance.

Genetically stable temperature-sensitive mutants of Salmonella typhi induce protection in mice

Temperature-sensitive (ts) mutants of Salmonella typhi were isolated following treatment with nitrosoguanidine, and characterized with respect to cut-off temperature, ts phenotype and reversion frequency. Linkage of the ts mutations to selectable chromosomal markers was established by generalized transduction with bacteriophage phage Vi I, and the appropriate antibiotic resistances were transduced into the ts mutants. Multiple mutant S. typhi were then constructed by combining three independent ts mutations in one strain, utilizing linkage of three of the mutations to erythromycin-, streptomycin- and methylglyoxal-resistance. Several recombinants are genetically stable, with calculated reversion rates of less than 10(-22), and induce both protection from intraperitoneal challenge with the virulent parental wild-type S. typhi in mice and the formation of antibodies to the somatic O-9 and O-12, the flagellar H and the capsular Vi antigens.

Vi I typing phage for generalized transduction of Salmonella typhi

Salmonella typhi Vi typing phages were used to transduce temperature-sensitive (Ts) mutants of Salmonella typhi. Antibiotic resistance and Ts+ markers were transduced at high frequency (> 10(-4) per virulent phage). Several markers were cotransduced by phage Vi I, suggesting that it may be useful for mapping studies of the S. typhi genome.

Differential persistence, immunogenicity and protective capacity of temperature-sensitive mutants of Salmonella enteritidis after oral or intragastric administration to mice

The persistence of Salmonella enteritidis temperature-sensitive (ts) mutants of different phenotypes in Peyer's patches (PP) and the spleen, and their immunogenicity after intragastric (i.g.) and peroral (p.o.) administration to mice was investigated. After p.o. administration the ts mutant C/2/2 colonized PP, but was not recovered from the spleen. After i.g. administration the ts mutant E/1/3 colonized both the spleen and PP for at least 2 weeks. Mutant C/2/2 persisted in PP up to 8 days but was not found in the spleen. Mutant H/2/26, although it poorly colonized the PP, was recovered from the spleen up to day 15 after i.g. administration. Immunization with E/1/3 by either the i.g. or the p.o. routes protected mice from challenge with 100 LD50 of the virulent wild-type (wt) strain. Immunization with either C/2/2 or H/2/26 did not confer protection. The three ts mutants induced the production of local IgA after i.g. administration regardless of their protective capacity.

Local and systemic immunity against Streptococcus pneumoniae: humoral responses against a non-capsulated temperature-sensitive mutant

Temperature-sensitive mutants of Streptococcus pneumoniae were isolated after chemical mutagenesis. Intranasal immunization with temperature-sensitive mutant J/3 induced higher levels of circulating antibody than those obtained after immunization with the heat-killed parental wild type. Moreover, local immunization with mutant J/3 induced high levels of anti-S. pneumoniae IgG and IgA in the lower respiratory tract, whereas only moderate IgG (and no IgA) antibodies were detected in lung lavage fluids from mice immunized intranasally with the heat-killed strain.

Protective capacity of a temperature-sensitive mutant of Salmonella enteritidis after oral and intragastric inoculation in a murine model

Temperature-sensitive (ts) mutant E/1/3 of Salmonella enteritidis was selected to evaluate its capacity to induce protective responses after peroral (p.o.) or intragastric (i.g.) inoculation to mice. This ts mutant of coasting phenotype was detected in Peyer's patches until day 4, and in spleen by days 3 and 4 after the mice were inoculated by the p.o. route with 10(10) colony forming units. Peroral immunization induced significant protection from oral challenge with 240 LD50 of the wild-type (wt) strain. Higher protection was achieved when the animals were boosted intraperitoneally after p.o. immunization. Intragastric inoculation with the same dose of the ts mutant increased both the level of protection, and colonization and persistence of the micro-organism in Peyer's patches and spleen. Immunization with a single i.g. inoculation induced 70% protection from p.o. challenge of the animals with the wt S. enteritidis. Two i.g. immunizations with E/1/3 raised the level of protection to 90%. Specific IgG, IgM and IgA antibodies, measured in plasma using a micro-ELISA method, were detected after i.g. immunization with ts mutant E/1/3. In addition, specific antibody-secreting cells were detected by means of an ELISPOT assay in spleen and mesenteric nodes of mice immunized with the ts mutant.

Preliminary characterization of Pseudomonas aeruginosa peptide chemotactins for polymorphonuclear leukocytes

In a previous report, we showed that supernatants of Pseudomonas aeruginosa cultures exhibit chemotactic activity for polymorphonuclear leukocytes (PMNL). In this study, P. aeruginosa chemotactins were isolated, purified, and partially characterized. The organisms were cultured in Vogel-Bonner defined medium, and cultures were stopped in late log phase. Chemotactins withstood heating, remained unaltered after acid or alkali treatment in a pH range from 4 to 10, and resisted digestion by trypsin or carboxypeptidase, but chemotactic activity was decreased by 73% after incubation with pronase. Only 2% of the total chemotactic activity of culture supernatants could be extracted with chloroform. Chemotactins with molecular sizes less than 3 kDa constituted the largest contribution to the chemotactic activity of culture supernatants. Pretreatment of PMNL with 10(-5) M formylmethionyl-leucyl-phenylalanine (FMLP) inhibited chemotaxis towards FMLP and P. aeruginosa culture supernatants but not towards complement component C5a. In conclusion, the total chemotactic activity for PMNL of P. aeruginosa culture supernatants was due, almost exclusively, to chemotactins that have properties similar, if not identical, to those exhibited by formylmethionyl peptides.

Oral immunization of mice with temperature-sensitive Pseudomonas aeruginosa enhances pulmonary clearance of the wild-type

DBA/2J mice were immunized daily for 3 days per os with 10(8)-10(9) colony forming units (c.f.u.) of two different temperature-sensitive (TS) mutants of Pseudomonas aeruginosa. At varying times after the final immunization the animals were exposed to aerosols of the parental immunotype 1, and the ability of the immunized and control mice to clear their lungs of the wild-type (WT) challenge was measured 4 h later. The number of c.f.u. remaining in the lungs of mice immunized with one mutant, D/1/8, was significantly less (p less than 0.01) than the number remaining in the lungs of control mice and mice immunized with a second TS mutant, E/9/9.

Immunization with temperature-sensitive mutants of Salmonella typhi induces protection in mice

Temperature-sensitive (TS) mutants of Salmonella typhi were isolated following mutagenesis with nitrosoguanidine and two cycles of enrichment with penicillin and D-cycloserine. Several of the TS mutants were characterized with respect to growth profiles at permissive (29 degrees C) and non-permissive (36 degrees C) temperatures, reversion rates, and the potential for inducing protection against challenge in an animal model. All three TS mutants tested were immunogenic in mice; antibodies measured by enzyme-linked immunosorbent assay were produced following intraperitoneal (i.p.) immunization with three different doses of each of the mutants; i.p. immunization with the same mutants also induced highly significant protection (100%) from i.p. wild-type challenge; and oral immunization with one of the mutants significantly reduced shedding of the wild-type following oral challenge.

Piroxicam treatment protects mice from lethal pulmonary challenge with Pseudomonas aeruginosa

The effect of treatment with the nonsteroidal anti-inflammatory agent piroxicam on leukocyte migration to the lungs was investigated after aerosol administration of sublethal doses of Pseudomonas aeruginosa to mice. Piroxicam decreased, in a dose-related fashion, the polymorphonuclear leukocyte recruitment to, and the degree of perivascular and peribronchial infiltration in, the lungs. Piroxicam treatment also protected the animals in a dose-dependent manner from challenge with lethal doses of P. aeruginosa. The effect of piroxicam was not related to direct action of the drug on the microorganisms. Piroxicam treatment maintained the animal's pulmonary defenses against infection while diminishing inflammatory responses against P. aeruginosa, an occurrence decreasing the potential for tissue damage due to phagocytes migrating from circulation.

Specific pulmonary defences against Pseudomonas aeruginosa after local immunization with temperature-sensitive mutants

The specificity of the enhancement in lung defences after local immunization of mice with three temperature-sensitive (ts) mutants of Pseudomonas aeruginosa was investigated. The three selected mutants display altered growth characteristics when transferred from 29 degrees C to mammalian body temperature. Mice immunized with the live ts mutants by aerosol exposure or multiple intranasal inoculations were challenged with aerosols containing wild-type (wt) P. aeruginosa. Aerosol immunization with ts mutant A/10/25 significantly enhanced the lung clearance of the wt but did not enhance the clearance of either Klebsiella pneumoniae or Staphylococcus aureus. Aerosol immunization with ts mutants D/1/8 or E/9/9 enhanced the lung defences against the parental wt (of identical immunotype 1) but not against immunotype 4; similarly, intranasal immunization enhanced the lung defences against the parental wt but not against immunotypes 4 or 5. We conclude that local immunization with ts mutants of P. aeruginosa enhances lung defences against the wt in a genus- and immunotype-specific fashion. It is suggested that local immunity may play a central role in immunoprophylaxis against P. aeruginosa lung infection.

Differential growth characteristics and immunogenicity of tight and coasting temperature-sensitive mutants of Pseudomonas aeruginosa

Genetically attenuated vaccines capable of limited replication in the vaccinate may elicit stronger, longer-lasting immunity than that induced by component, killed whole-cell, or nonreplicating live vaccines. We have isolated and partially characterized temperature-sensitive Pseudomonas aeruginosa mutants of two different phenotypes: a tight mutant, which ceases all growth immediately after its transfer to 36 degrees C, and a coaster, which continues to replicate for five generations at 36 degrees C. The growth profiles of the two temperature-sensitive phenotypes were compared both in vitro and in vivo; maintenance of the coasting phenotype in vivo was confirmed. The immunogenicity of the two phenotypes was compared in two models. In model 1, ICR mice were immunized intraperitoneally (i.p.) with graded doses of either mutant and challenged 3 weeks later i.p. with lethal doses of the wild-type strain. In model 2, DBA/2J mice were immunized intranasally with either mutant and subsequently challenged with an aerosolized inoculum of the wild-type strain, and lung clearance was measured over 4 h. In both models, the coaster demonstrated slightly higher immunogenic potential and, in addition, induced significantly higher levels of immunotype-specific serum immunoglobulin G after i.p. immunization.

Lung defenses against Pseudomonas aeruginosa in C5-deficient mice with different genetic backgrounds

Lung defenses against Pseudomonas aeruginosa were investigated in C5-deficient strains of mice with different genetic backgrounds. We studied pulmonary clearance and cell responses after aerosol exposure to P. aeruginosa in C5-deficient B10.D2/oSnJ and DBA/2J mice and their closest C5-sufficient counterparts, B10.D2/nSnJ and DBA/1J mice. Different patterns of lung clearance and pulmonary cell responses were found for the two C5-deficient strains. C5-deficient B10.D2/oSnJ mice showed defective lung clearance of P. aeruginosa 4 h after challenge compared with C5-sufficient B10.D2/nSnJ animals. This finding was associated with a decreased number of polymorphonuclear leukocytes recruited into the airways during the same time. Interestingly, C5-deficient DBA/2J mice recruited higher numbers of polymorphonuclear leukocytes than did C5-sufficient DBA/1J mice by 4 h after aerosolization. Nevertheless, lung clearance of P. aeruginosa in DBA/2J mice was not as effective as in C5-sufficient DBA/1J mice, suggesting that other functions of C5 besides chemotaxism could be involved. Lung clearance of P. aeruginosa was also investigated in C5-deficient and -sufficient hybrids sharing the same genetic background (DBA/2J X B10.D2). The results suggested that murine lung clearance of P. aeruginosa is markedly affected by lack of C5 in a specific genetic background (B10.D2).

Replication rate of Pseudomonas aeruginosa in the murine lung

Using a method recently developed at our laboratory, we determined the initial rate of Pseudomonas aeruginosa replication in the lung under different experimental conditions. Mice were exposed to aerosols containing mixtures of a temperature-sensitive (ts) mutant of P. aeruginosa and its parental wild type (wt). The changes in the ratio of ts:wt were determined by quantitatively culturing homogenates of lungs from animals sacrificed over different time periods. The doubling time (DT) was calculated as the reciprocal of the slope of the linear portion of the curve generated by plotting n = (log [r0/rt])/log 2 against time where r is the ratio of ts:wt at a given time. The DTs measured in both outbred ICR mice and F1 hybrids (DBA/2J X B10.D2/nSnJ) were 32 and 30 min, respectively. These DTs were higher than that determined in the peritoneal cavities of ICR mice (20 min). The DT in the lungs of ICR mice rendered granulocytopenic by treatment with cyclophosphamide was 16 min. Experiments performed with inocula of different sizes showed that DTs tended to be higher in animals aerosolized with low doses of the ts-wt mixture.

Enzyme-linked immunosorbent assay antibody responses to a temperature-sensitive mutant of Pseudomonas aeruginosa

The serum immunoglobulin G and M responses induced by immunization of mice with temperature-sensitive mutant A/10/25 of Pseudomonas aeruginosa were evaluated by enzyme-linked immunosorbent assay. These antibody responses were immunotype specific, and the immunoglobulin G antibody level, although low, was still significant by day 52 after vaccination.

Effect of chemotactins released by Staphylococcus aureus and Pseudomonas aeruginosa on the murine respiratory tract

Staphylococcus aureus, the Pseudomonas aeruginosa temperature-sensitive (ts) mutant A/10/25, and the P. aeruginosa parental wild type were aerosolized to C5-deficient mice, and the total number of polymorphonuclear leukocytes (PMN) recovered by lung lavage was determined 4 h after aerosol exposure. S. aureus induced a slight but significant recruitment of PMN, as compared with the effect of a saline aerosol. Both wild-type P. aeruginosa and the ts mutant induced a significant PMN recruitment of a magnitude ca. 180 times higher than that produced by S. aureus. Gentamicin-killed ts P. aeruginosa induced a PMN recruitment of a magnitude similar to that produced by live ts P. aeruginosa. Thorough washing of the bacteria, however, removed ca. 90% of the chemotactic activity. Exposure of the animals to a ts P. aeruginosa culture supernatant aerosol induced significant PMN recruitment into the lower airways. The same culture supernatants were chemotactic for mouse PMN in a dose-dependent fashion when tested in vitro in the absence of serum. Culture supernatants of S. aureus exhibited weak chemotactic activity in vitro and did not induce PMN recruitment in the lungs when aerosolized to DBA/2J mice. The results suggest that chemotactins released by P. aeruginosa may be an important virulence factor and play a significant role in lung tissue damage.

Quantitative determination of bacterial replication in vivo

A new methodology which permits the quantitative measurement of absolute bacterial replication in vivo is proposed. Mice were inoculated with mixtures of temperature-sensitive mutants and parental wild types, and the changes in the ratios of the two strains were measured. The number of wild-type generations was calculated from the declining ratios over time with the formula n = log (r0/rt)/log 2; n is the number of generations, and r0 and rt are the ratio of temperature-sensitive mutants to the parental wild type at time zero and at the times sampled throughout the experiment. The replication rate was determined by regression analysis. A mathematical argument for the formula is presented. Using this technique, we determined the mean generation times of Escherichia coli (33 min) and Pseudomonas aeruginosa (20 min) in the peritoneal cavities of mice, in the face of host clearance mechanisms during the first stages of infection.

Ibuprofen modifies the inflammatory response of the murine lung to Pseudomonas aeruginosa

In chronic P. aeruginosa infection, lung tissue damage is induced by either the microorganism or the inflammatory response. We investigated, in an animal model, whether a non-steroidal anti-inflammatory drug, ibuprofen, reduced lung inflammation produced by P. aeruginosa. Lung lavages, pulmonary clearance of P. aeruginosa and lung pathology were studied in CD-1 mice injected with sodium ibuprofenate. A single dose of the drug, injected immediately after 30 min exposure to the P. aeruginosa aerosol, decreased the recruitment of granulocytes into airways in a dose-dependent manner. Pretreatment with 2 doses of the drug 18 and 6 h before the P. aeruginosa challenge was even more effective. The kinetics of changes in prostaglandin E2, 6-keto-prostaglandin F1 alpha and thromboxane B2 concentrations in lung lavage fluids after P. aeruginosa aerosol were also modified by ibuprofen. Moreover, ibuprofen treatment did not impair lung clearance of the challenge microorganisms, and the animals had less inflammation of the lungs.

Inflammatory responses to Pseudomonas aeruginosa and Staphylococcus aureus in the murine lung

The changes in pulmonary cell population in response to aerosols containing either Pseudomonas aeruginosa or Staphylococcus aureus were studied in a murine model. The lungs of inbred DBA/2J mice received an inoculum of 2 X 10(5) colony-forming units of the microorganism and lung lavages were performed at various time intervals thereafter. P. aeruginosa aerosols produced an immediate decrease in the number of resident alveolar macrophages (AM), followed by a two-waved recruitment of cells into the respiratory tract; the first wave was composed of polymorphonuclear leukocytes (PMN) and the second of monocyte-like peroxidase-positive AM. The change in cell populations was transient and returned to baseline values within a week after aerosolization. In contrast, aerosolized S. aureus initially induced a slight increase in mononuclear cells, and by 60 min after aerosol exposure, the cell population was not different from that of control animals.

Short communication. Role of agar beads in the pathogenicity of Pseudomonas aeruginosa in the rat respiratory tract

Sterile agar beads plus Pseudomonas aeruginosa injected intratracheally produced local infection in rats, similar to that described for the injection of agar beads containing the same pathogen. It is suggested that it is not necessary for P. aeruginosa to be inside the beads to induce lung infection.

Impaired lung defenses against Staphylococcus aureus in mice with hereditary deficiency of the fifth component of complement

Mice of the C5-deficient DBA/2J and B10.D2/oSnJ inbred strains were aerosolized with Staphylococcus aureus, and the pulmonary clearance of bacteria was determined 4 h later. Both C5-deficient strains had a significantly decreased lung clearance of S. aureus compared with their genetically closest C5-sufficient relatives, DBA/1J and B10.D2/nSnJ strains, respectively. Serum hemolytic activity and pulmonary clearance of S. aureus were also investigated in F1 and F2 progenies (DBA/1J X DBA/2J and DBA/2J X B10.D2/oSnJ). Serum hemolytic activity was present in all F1 (DBA/1J X DBA/2J) mice, and their pulmonary clearance of S. aureus was no different from that of the C5-sufficient parents (DBA/1J). The absence of serum hemolytic activity (absence of C5) in all mice from F1 and F2 (DBA/2J X B10.D2/oSnJ) and 20% of the F2 (DBA/1J X DBA/2J) was related to a decreased lung clearance of S. aureus. These results are consistent with an autosomal recessive pattern of heredity for the murine abnormality in pulmonary clearance of S. aureus.

Pulmonary clearance of Staphylococcus aureus and plasma angiotensin-converting enzyme activity in hydrocarbon pneumonitis

Pulmonary clearance of Staphylococcus aureus and plasma angiotensin-converting enzyme (ACE) activity were investigated in an experimental mouse model of kerosene aspiration. Twenty-four hours after acute kerosene aspiration, mice were exposed for 30 min to an aerosol containing the pathogen, and the uncleared bacteria ratio (UBR) determined 4 h after nebulization. The results showed a significant increase (P = 0.004) in UBR in animals with severe pneumonitis (0.44 +/- 0.05) when compared with controls (0.24 +/- 0.03). This impairment in lung clearance correlated with the increase in lung weight and the decrease in plasma ACE levels. Mice with kerosene pneumonitis had zones of lung injury, and areas with no gross signs of tissue damage. Lung clearance of S. aureus was significantly impaired in damaged areas whereas it was no different from controls in the non-affected areas. It is suggested that the measurement of plasma ACE activity may be an adjunct in the assessment of the extent of lung injury in hydrocarbon aspiration in children.

Enhancement of Pseudomonas aeruginosa lung clearance after local immunization with a temperature-sensitive mutant

We investigated the capacity of the temperature-sensitive mutant strain A/10/25 of Pseudomonas aeruginosa (ts-Psa) to induce enhancement of lung defenses against wild type P. aeruginosa (wt-Psa). Mice of the DBA/2J inbred strain were immunized by aerosolization with a single dose of 2 x 10(5) to 4 x 10(5) CFU of ts-Psa and were challenged 7, 14, and 21 days later with wt-Psa. The uncleared bacteria ratio was determined 4 h after aerosol exposure; significant enhancement in lung clearance of wt-Psa (P less than 0.01) was evident as early as 7 days after immunization and detectable for at least 21 days. Aerosol immunization with Staphylococcus aureus did not enhance lung clearance of wt-Psa; however, slight but significant enhancement in S. aureus clearance was observed in mice immunized 7 days before with ts-Psa. No enhancement of S. aureus clearance was seen in ts-Psa immunized animals after 14 and 21 days. Analysis of the cell composition of lung lavage fluids revealed a transient cell response characterized by rapid increase in the absolute number of polymorphonuclear leukocytes, followed later by an increase in alveolar macrophages. The characteristics of lung lavages returned to base-line values 6 days after aerosol immunization, and a second exposure to a ts-Psa aerosol produced a response of similar magnitude and quality. We conclude that aerosol immunization with a temperature-sensitive mutant of P. aeruginosa enhances specific pulmonary defense mechanisms against the parental pathogen in mice.

Defective mononuclear phagocytic function in mice homozygous for the cribriform degeneration autosomic recessive mutation

Decreased lung clearance of Staphylococcus aureus has been reported in mice homozygous for the cribriform degeneration (cri) autosomal recessive mutation. In the present study, the phagocytic capacities of alveolar and peritoneal macrophages were quantitated by applying kinetics of the first order reaction criteria. The characteristics of the pulmonary and peritoneal mononuclear cell populations from mutant and control mice were indistinguishable. The kinetic assays revealed decreased phagocytosis work in both alveolar and peritoneal macrophages from cri/cri mice. The results lend support to this mutation as a possible model system to study the early stages of lung disease physiopathology in cystic fibrosis.