Susceptibility of irradiated B6D2F1/J mice to Klebsiella pneumoniae administered intratracheally: a pulmonary infection model in an immunocompromised host

Bacteria such as Klebsiella pneumoniae can invade and colonize an immunocompromised host and complicate clinical recovery. In the study reported here, an experimental model of induced pneumonia was developed in 60Co gamma-photon-irradiated mice for the purpose of evaluating efficacy of therapeutic agents. The model was characterized by use of probit analysis of bacterial dose, and microbiologic, and histopathologic results. Bacterial colony-forming-unit (CFU) values producing 50% mortality within 30 days (LD50/30) and their 95% confidence intervals were 4.0 x 10(4) [1.7 x 10(4) - 8.9 x 10(4)] for 0-Gray (Gy)-irradiated mice, 1.9 x 10(4) [7.0 x 10(3) - 4.8 x 10(4)] for 5-Gy-irradiated mice, and 1.0 x 10(3) [2.8 x 10(2) - 3.3 x 10(3)] for 7-Gy-irradiated mice. Probit regression line fits calculated by use of an iterative, weighted least-squares fit, were used to assess a dose-modifying factor (DMF). The DMFs for mortality, compared with that for the 0-Gy dose, with their 95% confidence intervals, were 2.2 [0.63 - 7.7] for the 5-Gy and 38.9 [9.6 -165.0] for 7-Gy doses. The 5-Gy probit line did not significantly differ (P = 0.21) from the 0-Gy probit line (dose ratios did not significantly differ from 1), whereas the 7-Gy probit line differed significantly from the 0-Gy probit line (P < 0.001). These results demonstrate that 7-Gy 60Co gamma-photon radiation in combination with intratracheal K. pneumoniae challenge induces a valid pulmonary infection model in immunocompromised female B6D2F1/J mice.     

Experimental chronic pulmonary infection in mice caused by Klebsiella pneumoniae

Examination of mouse strain differences in susceptibility to experimental respiratory tract infection with Klebsiella pneumoniae 27 revealed that a chronic pulmonary infection model could be established using CBA/J mice. After 6 X 10(5) colony-forming units of K. pneumoniae 27 were inoculated into the lung, the bacterial counts in the lungs changed with time showing four different phases: initial decrease, regrowth, steady-state, and final increase leading to death. Throughout the course of the infection, the challenge bacteria were isolated mainly from the respiratory organs. Pulmonary gross lesions appeared on day 2 after infection and persisted thereafter. Lobar consolidation was the primary lesion and occurred mainly in the anterior and middle lobes of the right lung, and the median lobe. Mice began to die from 4 weeks after aerosol exposure. This model may be useful for investigating the pathogenesis of chronic pulmonary infection by Klebsiella and its therapy.     

The role of Klebsiella oxytoca in utero-ovarian infection of B6C3F1 mice

A disease consisting of suppurative endometritis, salpingitis, perioophoritis and/or peritonitis has been an important problem in aging B6C3F1 mice on some chronic chemical carcinogenicity studies. Klebsiella oxytoca was identified as the most likely causative agent based on cultural isolations from lesions. A study was done to determine prevalence of K. oxytoca in the "normal" flora of mice from different breeding facilities. In a survey of 684 retired female breeder mice from 10 National Institutes of Environmental Health Sciences (NIEHS) and National Cancer Institute (NCI) production facilities, K. oxytoca was isolated from only 1% of nasopharynxes, vaginas and ceca in mice from 7 of 10 facilities. Epizootiology of the natural infection was investigated using the capsular and biochemical typing methods on 97 isolates of K. oxytoca from mice of 11 NIEHS and NCI production facilities and sentinel mice from three National Toxicology Program testing facilities. A few capsular types were associated with either lesions, nonlesion isolation sites, or certain facilities but the capsular typing method was not reproducible. No associations were found for any biotypes. A K. oxytoca isolate (capsular type 20, biotype A) from a typical case of perioophoritis was used in attempts to reproduce the natural disease in Klebsiella-free B6C3F1 female mice. Mice were inoculated at 6 months of age by the intravaginal, intrauterine or intraperitoneal route with one of four doses of K. oxytoca and killed at 4, 7 or 10 months post-infection. Some mice given high doses (10(6) or 10(8) colony forming units) of K. +oxytoca died of septicemia and a few developed mild inflammatory lesions in the uterus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antigraft responses to the H-28c antigen by B6 and B6D2F1 mice

The survival of minor H antigen-bearing skin grafts from donors congenic with C57BL/6 (B6) was compared in B6, B6D2, and AB6 hybrid recipients. In a case singled out for further study, B6 mice were found to reject HW 110 skin (H-28^c antigen) rapidly, whereas B6D2 mice rejected HW110 skin much more slowly and variably. Both major histocompatibility complex (MHC)-linked and non-MHC genes appeared to affect the survival of HW110 strain skin grafts on B6 and B6D2 recipients. Results of several experiments appear to rule out the sharing of H-28° epitopes between donors and recipients as an explanation for the relatively poor response of B6D2 mice to HW 110 skin grafts. Experiments involving bone marrow chimeras produced by the reciprocal exchange of bone marrow between irradiated B6 and B6D2 mice suggest that bone marrow-derived donor cells and non-bone-marrow-derived host cells each contribute to the immune response phenotype with respect to the H-28° antigen. An attempt was made to determine whether B6D2 mice that failed to reject HW110 strain skin grafts possessed suppressor cells specific for the H-28^c antigen. Spleen cells from poorly responsive B6D2 mice failed to suppress the rejection of HW 110 skin grafts when assayed in immunodeficient mice that were provided with cells from immune 136132 donors that were highly responsive to HW110 skin grafts.     

Utero-ovarian infection in aged B6C3F1 mice

An unusually high number of ovarian masses and cysts with purulent material were observed in the B6C3F1 mice on 2 year chemical carcinogenicity studies sponsored by the National Cancer Institute-National Toxicology Program. To determine possible etiology, some of these lesions were cultured for bacteria and a majority yielded Klebsiella sp. Necropsy records of 14,029 female mice in 91 chronic studies necropsied from 1979 to 1983 at six toxicology testing laboratories were reviewed to determine the incidence of lesions and distribution of this disease. Animals for these studies were obtained from barrier production colonies of six suppliers. The incidence of this lesion was low in animals less than 14 months of age, increased with age and reached a peak in 24-26 month old mice. Most animals having this lesion either died or were sacrificed in moribund condition, indicating that this is a life shortening disease of aged B6C3F1 mice. The incidence of lesions ranged from less than 1% to 70% in different chronic studies. There was a marked difference in the incidence in mice from different suppliers and the incidence rate was 2.6 to 15% depending on the source of the animals. The incidence of this lesion in some testing laboratories was several-fold higher than in others and ranged from 0.9 to 20%. The proportion of mice with this lesion was low in some laboratories irrespective of the source of the animals, whereas in other laboratories the incidence was several-fold higher with animals from some, but not all suppliers, indicating testing laboratory-supplier interaction.(ABSTRACT TRUNCATED AT 250 WORDS)     

The DTH effector response and IL-2 are unaffected by cyclosporine A in autoimmune B6D2F1 mice

Delayed-type hypersensitivity (DTH) is classically defined as inflammation involving activated Th1 cells and cytokine production. DTH paw swelling, along with the cytokines IL-2, IFNγ, MCP-1 and TNFα, were inhibited in Balb/c mice by cyclosporine A (CsA). Surprisingly, the DTH response in the B6D2F1 mice was unaffected by CsA, despite a decrease in TNFα and IFNγ levels. IL-2 levels, however, were not decreased. To determine if the IL-2 production in the B6D2F1 strain is occurring through CD28-mediated costimulation, both CsA and CTLA-4Ig were administered. Paw swelling and IL-2 levels were decreased, indicating a role for costimulation. Co-administration of temsirolimus and CsA also reduced DTH and IL-2 levels in B6D2F1 mice, demonstrating involvement of the mTORC1 pathway. These results indicate that the cell activation pathways responsible for DTH differ with mouse strain. It is important to understand these differences in order to accurately interpret the results using potential therapeutic agents.     

More on the circadian melatonin rhythm in pineals from domesticated B6D2F1 mice

For melatonin (a chronomodulator of adrenal cortical function, immune phenomena and carcinogenesis), a circadian rhythm is demonstrated in aqueous pineal homogenate of domesticated B6D2F1 mice. Domestication as such does not eliminate a mechanism of cephalo-adrenal coordination.     

Androgen- and estrogen-independent regulation of copulatory behavior following castration in male B6D2F1 mice

Male reproductive behavior is highly dependent upon gonadal steroids. However, between individuals and across species, the role of gonadal steroids in male reproductive behavior is highly variable. In male B6D2F1 hybrid mice, a large proportion (about 30%) of animals demonstrate the persistence of the ejaculatory reflex long after castration. This provides a model to investigate the basis of gonadal steroid-independent male sexual behavior. Here we assessed whether non-gonadal steroids promote mating behavior in castrated mice. Castrated B6D2F1 hybrids that persisted in copulating (persistent copulators) were treated with the androgen receptor blocker, flutamide, and the aromatase enzyme inhibitor, letrozole, for 8 weeks. Other animals were treated with the estrogen receptor blocker, ICI 182,780, via continual intraventricular infusion for 2 weeks. None of these treatments eliminated persistent copulation. A motivational aspect of male sexual behavior, the preference for a receptive female over another male, was also assessed. This preference persisted after long-term castration in persistent copulators, and administration of ICI 182,780 did not influence partner preference. To assess the possibility of elevated sensitivity to sex steroids in brains of persistent copulators, we measured mRNA levels for genes that code for the estrogen receptor-α, androgen receptor, and aromatase enzyme in the medial preoptic area and bed nucleus of the stria terminalis. No differences in mRNA of these genes were noted in brains of persistent versus non-persistent copulators. Taken together our results suggest that non-gonadal androgens and estrogens do not maintain copulatory behavior in B6D2F1 mice which display copulatory behavior after castration.     

Spontaneous, asymmetrical microphthalmia in C57B1/6J mice

An investigation was undertaken to evaluate ocular size and shape by objective and subjective criteria to establish the incidence and laterality of spontaneous microphthalmia in the C57B1/6J mouse strain. The purpose was to provide useful information of normal and abnormal ocular development in a laboratory strain frequently used for teratogenic studies. Ten-week-old C57B1/6J mice were time mated and sacrificed at gestational day 14. Eye normality was evaluated subjectively using veterinary ophthalmology methods, and objectively by a computer derived method. A distinct laterality was noted in the right eye when compared to the left eye. Degree of laterality varied with assessment methodology (19.0% vs. 6.9% and 8.9% vs. 4.0% for the subjective and objective methods respectively). Mean eye area and histogram distributions for the right eye were consistently smaller than the left eye for all anatomical rating groups, thereby suggesting that asymmetry found in the C57B1/6J may be due to an inherent discrepancy in eye size in the strain. The data from this study suggest that when C57B1/6J mouse eyes are used as end points for teratological testing each eye should be treated as an independent unit of measure.     

Adoptive transfer of natural killer cell activity in B6D2F1 mice challenged with Salmonella typhimurium

The purpose of this study was to extend our previous findings as to the role of murine NK cells in host protection to a challenge infection with virulent Salmonella typhimurium SR-11. B6D2F1 mice were depleted of NK cells with anti-asialo GM1 or a monoclonal antibody, anti-NK 1.1, followed by a salmonellae challenge. Significantly decreased numbers of splenic bacteria (P less than 0.005) in the NK cell-depleted mice were note at 12, 24, and 48 hr postchallenging, compared to the sham-injected control animals. When Percoll gradient-enriched large granular lymphocytes (NK cells) were adoptively transferred to NK cell-depleted mice followed by challenging, the splenic bacterial numbers were comparable to those present in NK cell-intact, control mice. These data indicate that large granular lymphocytes (NK cells) are responsible for the down-regulation of the protective host response in mice challenged with the facultative intracellular parasite. S. typhimurium.     

Reduced adrenal response and increased mortality after systemic Klebsiella pneumoniae infection in interleukin-6-deficient mice.

During bacterial infections, both the immune system and the hypothalamus-pituitary-adrenal (HPA) axis are activated. The role of IL-6 in the activation of the HPA axis during bacterial sepsis is not fully understood. The aim of the present study was to investigate the role of endogenous IL-6 in a potentially lethal infection with Klebsiella pneumoniae and the concomitant activation of the HPA axis. We examined the mortality of IL-6-/- and IL-6+/+ mice after intravenous (i.v.) infection with K. pneumoniae as well as the bacterial outgrowth in several organs. Subsequently, the influence of endogenous IL-6 on the effect of i.v. administration of K. pneumoniae on the plasma levels of corticosterone and the pro-inflammatory cytokines TNF-alpha and IL-1alpha was investigated in these mice. The present study demonstrates that IL-6-/- mice are more susceptible than IL-6+/+ mice to a systemic Gram-negative infection with K. pneumoniae, leading to increased outgrowth of microorganisms in the organs of the mice. Moreover, this infection is associated with a reduced adrenal response in IL-6-/- mice. We conclude that IL-6-/- mice are more susceptible to Gram-negative bacterial infections, which is mainly due to an impaired recruitment of granulocytes to the site of infection in the absence of IL-6. Furthermore, the reduced adrenal response may be an explanation for the strong inflammatory response with higher TNF-alpha plasma levels in IL-6-/- mice.     

2014—2016年大连地区血流感染肺炎克雷伯菌的耐药性特征分析

目的 分析肺炎克雷伯菌所致血流感染患者的科室分布及其病原菌耐药性特征,为指导临床合理应用抗菌药物,有效控制感染提供依据。方法 选择2014—2016年大连医科大学附属第一医院送检血液标本中分离得到的289株肺炎克雷伯菌,对其进行细菌鉴定、药敏试验及ESBL确认试验,分析肺炎克雷伯菌所致血流感染的科室分布特征及其病原菌耐药性变迁。结果 患者血液中肺炎克雷伯菌检出率以急诊科（24.91%）和ICU为最高（23.88%）。3年中肺炎克雷伯菌对碳青霉烯类抗生素和阿米卡星耐药率较低,均在20.00%左右。产ESBL肺炎克雷伯菌共135株,占46.71%,对常用抗生素的耐药率均显著高于非产ESBL菌株（P<0.01）。碳青霉烯类抗生素耐药菌株对常用抗生素耐药率均高于敏感菌株（P<0.01）,对四环素、复方新诺明和阿米卡星耐药率相对较低,分别为66.10%、66.10%、71.19%。结论 我院2014—2016年患者血液中肺炎克雷伯菌检出率以急诊科和ICU为最高。该菌对碳青霉烯类抗生素及阿米卡星的耐药率较低,碳青霉烯类抗生素耐药菌株对四环素、复方新诺明和阿米卡星尚有一定敏感性。     

Protective activity of a cell-free Klebsiella vaccine in infection in mice caused by Streptococcus pneumoniae serotypes

The capacity of dried Klebsiella cell-free vaccine, obtained from strain No. 204 by the disintegration of microbial mass with hydroxylamine, for protecting mice from pneumococcal infection caused by S. pneumoniae, serotypes 3, 4 and 9N, has been studied. Klebsiella vaccine has been found to possess immunostimulating potency with respect to the S. pneumoniae serotypes under study. On day 5 this potency is manifested to a greater extent than 24 hours after immunization. The combination of Klebsiella vaccine with Proteus vulgaris, Staphylococcus aureus and Escherichia coli K-100 antigens enhances the stimulation of nonspecific resistance.     

Relationship of atypical melatonin rhythm with two circadian clock outputs in B6D2F(1) mice

Circadian rhythms in body temperature, locomotor activity, and the circadian changes of plasma and pineal melatonin content were investigated in B6D2F(1) mice synchronized by 12 h of light and 12 h of darkness. During 8 wk continuous recording, activity and temperature displayed a marked stable and reproducible circadian rhythm, with both peaks occurring near the middle of darkness. Both 24- and 12-h rhythmic components were also significantly detected. Mean plasma melatonin concentration rose steadily during the light span and reached a maximum (30.6 +/- 10.0 pg/ml) at 11 h after light onset (HALO), then gradually decreased after the onset of darkness to a nadir (4.7 +/- 0.4 pg/ml) at 20 HALO. Mean pineal content followed a pattern parallel to that of plasma concentration (peak at 11 HALO: 17.7 +/- 1.0 pg/gland; trough at 17 HALO: 4.7 +/- 1.0 pg/gland). In addition, a second sharp peak was observed at 21 HALO (20.2 +/- 3.5 pg/gland). Plasma and pineal contents displayed large and statistically significant circadian changes, with a composite rhythm of period (24 + 12 h). This mouse model has predominant production and secretion of melatonin during the day. This possibly contributes to a similar coupling between chronopharmacology mechanisms and the rest-activity cycle in these mice and in human subjects.     

Examination of host defense factors responsible for experimental chronic respiratory tract infection caused by Klebsiella pneumoniae in mice.

We have studied the host defense factors that operate during the course of chronic respiratory tract infection caused by Klebsiella pneumoniae 27 in CBA/J mice. A large number of polymorphonuclear leukocytes (PMNs) rapidly infiltrated the alveolar spaces after infection. Treatment with cyclophosphamide (CY) before infection greatly reduced the infiltration of PMNs and caused an increase in bacterial counts. CY treatment of mice in the chronic phase also caused bacterial proliferation in the lungs. The administration of a high titer immune serum efficiently reduced the bacterial counts in the lungs during the early phase but not during the chronic phase. The proliferation of bacteria induced by CY treatment was not suppressed by the administration of the immune serum in either phase. When the mice were exposed to an aerosol containing Pseudomonas aeruginosa P9 in the chronic phase, the organisms from the secondary infection were eliminated from the lungs in the same manner as in the case of primary infection with P. aeruginosa. Thus, PMNs seem to play an important role in the suppression of bacterial proliferation in the early and chronic phases, and the specific antibody might have a supplementary effect on the defensive action of PMNs in the chronic phase. It is also presumed that the bacteria in the chronic phase of infection are sequestered at sites hardly accessible to PMNs.     

The gut microbiota modulates differential adenoma suppression by B6/J and B6/N genetic backgrounds in ApcMin mice

Mammalian Genome - Tumor multiplicity in the ApcMin (Min) mouse model of CRC is a classic quantitative trait that is subject to complex genetic and environmental factors, and therefore serves as an...     

Protective effect of recombinant human interleukin-2 against lethal infection caused by Klebsiella pneumoniae

The effects of recombinant human interleukin-2 (rIL-2) administered prophylactically on the death of CBA/J mice challenged with Klebsiella pneumoniae 27 intraperitoneally were examined. rIL-2 administered subcutaneously at 20 micrograms per mouse for 7 days enhanced survival after a lethal challenge. The injection of anti-asialo GM1 antibody did not influence the effect of rIL-2. In mice given rIL-2, the number of peritoneal macrophages increased, and the infiltration of polymorphonuclear leukocytes (PMN) into the peritoneal cavity after the bacterial challenge was enhanced. In addition, adoptive transfer of sera and peritoneal exudate cells (PEC), consisting of an approximately equal number of macrophages and PMN, obtained from mice given rIL-2 enhanced resistance to a K. pneumoniae infection, compared with adoptive transfer of sera and PEC obtained from mice not given rIL-2. These results indicate that rIL-2 protects mice from a lethal challenge with K. pneumoniae, and suggest that the protective effect is due to an increase in the number of phagocytic cells and in the cooperative activity of the sera and the phagocytic cells.     

Immune response of (C57BL/6xA/Sn)F1 mice in mycoplasm-virus infection

Mixed Rauscher leukemia virus (RLV) and M. arthritidis infection of (C57BL/6xA/Sn)f1 mice-hybrids, highly resistant to RLV, was accompanied by a progressive inhibition of rosette-forming cells (RFC) and plaque-forming cells (PFC), resulting in the induction of malignant erythroblastosis identical by cytology to Rauscher leukemia. The mice-hybrids infected with A. laidlawii and RLV developed significant splenomegaly on the 21st day of the infection, and their immune response was almost entirely suppressed, but both RFC and PFC populations as well as the spleen weight returned to the initial level by the 62d day the infection. A possible role of mycoplasm in the induction and development of Rauscher leukemia is discussed.