Survival of pathogenic bacteria in various freshwater sediments

Four human-associated bacteria, Pseudomonas aeruginosa, Salmonella newport, Escherichia coli, and Klebsiella pneumoniae, were tested for survival in five freshwater sediments. Bacterial survival in continuous-flow chambers was monitored over 14-day periods on sediments ranging from organically rich high-clay fractions to organically poor sandy fractions. Bacterial die-off ranged from 1 to 5 orders of magnitude in sediments. E. coli survived as long as or longer than S. newport. P. aeruginosa and K. pneumoniae tended to survive longer than E. coli. Survival of E. coli and S. newport was greater in sediments containing at least 25% clay. Good reproducibility allowed the development of linear models to describe die-off rates.     

Survival of pathogenic bacteria in various freshwater sediments.

Four human-associated bacteria, Pseudomonas aeruginosa, Salmonella newport, Escherichia coli, and Klebsiella pneumoniae, were tested for survival in five freshwater sediments. Bacterial survival in continuous-flow chambers was monitored over 14-day periods on sediments ranging from organically rich high-clay fractions to organically poor sandy fractions. Bacterial die-off ranged from 1 to 5 orders of magnitude in sediments. E. coli survived as long as or longer than S. newport. P. aeruginosa and K. pneumoniae tended to survive longer than E. coli. Survival of E. coli and S. newport was greater in sediments containing at least 25% clay. Good reproducibility allowed the development of linear models to describe die-off rates.     

临床和非临床分离沙门菌的菌型分布及对抗生素的耐药性研究

目的：探讨沙门菌在腹泻病人粪便、外环境污水和部分动物标本中的菌型分布及其对抗生素的耐药性。方法：采用血清学方法对沙门菌进行分群和分型,采用K—B法进行抗生素耐药性测定。结果：410份临床腹泻病人标本和514份非临床标本共检出沙门菌93株,检出率为10．1％,其菌型分布为：腹泻病人粪便中检出的均为B群鼠伤寒沙门菌(6／93),非临床标本中的菌型主要为C2群纽波特沙门菌(72／93),还有E1群伦敦沙门菌(7／93)、B群鼠伤寒沙门菌(2／93)和未定型(6／93)。87株沙门菌对青霉素的耐药率最高(96．5％),其次为SMZ TMP(73．6％),未发现对新霉素、链霉素、四环素和阿米卡星的耐药株。结论：实验结果可为研究我省沙门菌的菌型分布及其对抗生素的耐药性提供参考;临床上应加强对鼠伤寒沙门菌引起腹泻的监测。     

Paw oedema test for detection of Salmonella enterotoxin : modification and standardization

Paw oedema test (POT) was standardized with modifications for the detection of Salmonella enterotoxin. Instead of measuring the weight of the inoculated paws after amputating the limbs at 48 hr post-inoculation, percent relative thickness of the order of 121 +/- 3.8% at 24-48 hr was found to be a better index. This test yielded parallel results to rabbit ligated ileal loop (RLIL) technique. The test was positive with enterotoxic crude cell lysates (CL) and cell free-culture-supernatants (CFCS) of S. newport and S. typhimurium, partially purified and purified enterotoxin of S. newport and purified cholera toxin. The test was found to be specific in that non-enterotoxic CFCS did not cause significant increase in the thickness. Minimum detection level of purified S. newport enterotoxin was estimated to be as low as 20 micrograms. Thus, the modified POT was considered to be an effective and economical bioassay model for the detection of Salmonella enterotoxin.     

Antibiotic resistance in coagulase-negative staphylococci isolated from Cope''s gray treefrogs (Hyla chrysoscelis)

Microcin J25 (MccJ25) is a cyclic peptide of 21 unmodified amino acid residues produced by a fecal strain of Escherichia coli. It has previously been shown that the antibiotic activity of this peptide is mainly directed to Enterobacteriaceae, including several pathogenic E. coli, Salmonella and Shigella strains. In this paper we show that MccJ25 acts on the cytoplasmic membrane of Salmonella newport cells producing alteration of membrane permeability, and the subsequent gradient dissipation, that initiate the inhibition of process, such as oxygen consumption. These results, taken together with our in vitro observations [Rintoul et al. (2000) Biochim. Biophys. Acta 1509, 65-72], strongly suggest that the disruption of the cytoplasmic membrane gradient is closely related to the bactericidal activity of MccJ25 in S. newport.     

Serotypes,virulence factors,antibiotic sensitivity,beta-lactamase activity and plasmid analysis of Salmonella from children with diarrhea in Tripoli (Libya)

A total of 21 Salmonella strains isolated in Libya (16 from children with diarrhea and 5 from healthy controls) were serotyped and studied for their cell invasive ability, production of cytotoxin, antibiotic susceptibility, beta-lactamase activity and plasmid profiles. Eight different serotypes of Salmonella were identified: 6 S. saintpaul, 4 S. wien (1 from control), 2 S. newport, 2 S. muenchen (1 from control), 2 S. typhimurium (1 from control), 2 S. hadar (1 from control), 2 S. reading (1 from control), 1 S. kottbus. Twenty (95%) were positive in the invasiveness assay using HeLa cells, and all (100%) were negative for cytotoxin production in HT29 cells. More than 40% were resistant to ampicillin, cefalexin, cefamandole, cefoperazone, chloramphenicol, gentamicin, mezlocillin and trimethoprimsulphamethoxazole and 100% were susceptible to the new quinolones. Most (67%) of the strains harbored plasmids and 43% produced beta-lactamase. A strong association was observed between the presence of more than one plasmid, beta-lactamase activity, and multiple-resistance to antimicrobial agents and serotypes S. saintpaul and S. wien. Curing experiments with acridine orange showed that 2 plasmids (33 and 1.4 megadaltons) might be responsible for the resistance to chloramphenicol and gentamicin. The present study demonstrated that multiple-resistant salmonellae are widespread in Libya and the resistance is mainly plasmid mediated.     

Specific assays for bacteria using phage mediated release of adenylate kinase

A sensitive and rapid assay method for the specific detection of bacteria was developed using Escherichia coli and Salmonella newport as the test organisms. Bacteriophages were used to provide specific lysis of the bacteria and then the release of cell contents was measured by ATP bioluminescence. Increased sensitivity was obtained by focusing on the bacteria's adenylate kinase (AK) as the cell marker instead of ATP as conventionally used. Fewer than 10³ E. coli cells could be readily detected in less than 1 h. Salmonella newport assays, although as sensitive, were slower and took up to 2 h. The effects of the culture medium, the phage, and the presence of non-specific bacteria were examined.     

Effects of Various Gases on the Survival of Dried Bacteria During Storage

Salmonella newport and Pseudomonas fluorescens were dried together in papain digest broth and sucrose-glutamate, and stored in several gases at various water activities (a(w)) between 0.00 and 0.40 at 25 C for various periods up to 81 weeks. Both S. newport and P. fluorescens, dried in papain digest broth and stored in air, died rapidly if the conditions were very dry (0.00 a(w)) or moist (0.40 a(w)). Storage in carbon dioxide and argon gave greater survival than storage in air but lower survival than did storage in nitrogen or in vacuo. When the organisms were dried in a sucrose-glutamate mixture the differences between the gases were very small, and variations in residual water were less important. Of the inert gases, argon gave the best survival when the organisms were dried in papain digest broth, especially at 0.00 a(w); the survival in neon and krypton was lower and in xenon and helium it was much lower.     

Frequency and duration of paratyphoid organism shedding by experimentally infected bobwhite quail (Colinus virginianus)

Four-week old bobwhite quail (Colinus virginianus) were experimentally infected with Salmonella urbana, S. infantis, S. newport, S. gaminara, S. braenderup, and S. litchfield. Rates of mortality varied from 0 to 50%. The rate of shedding of paratyphoid organisms varied from 14 to 100% for 18 or more days after infection. The maximum duration of shedding was 53 days by 12% of the quail infected with S. braenderup and the minimum duration was 18 days by 14% of the quail infected with S. litchfield.     

Bacteriophages mediating somatic antigenic conversion in Salmonella cholerae-suis: their isolation from sewage and other Salmonella serotypes possessing the somatic 6 antigen

Bacteriophages which mediate the conversion of the O somatic antigen of Salmonella cholerae-suis from the 6(2)7 to the 6(1)7 phenotype have been isolated from two strains of S. newport and one of S. muenchen, and also from sewage collected from two areas where there have been no reports of S. cholerae-suis infection for several years. The phages differed from each other by cross-resistance tests.     

Salmonella serotypes isolated from human enteric processes in Recife, Pernambuco, during 1978-1980

From 13,196 faecal cultures made in Recife-Pernambuco during the period from 1978 to 1980, 1,720 strains of Salmonella were isolated. Serological typing on 1,387 of the isolates recognized 63 serotypes, 73.18% of which belonged to group B. The prevalent serotypes adding up to 1,231 strains (88.75% of the total of the isolates) were: S. typhimurium, S. saint-paul, S. poona, S. derby, S. agona, S. newport, S. oranienburg, S. infantis, S. tshiongwe and S. ndolo.     

E-cadherin mediates aggregation-dependent survival of prostate and mammary epithelial cells through the retinoblastoma cell cycle control pathway

E-cadherin and the retinoblastoma tumor suppressor (Rb) are traditionally associated with diverse regulatory aspects of cell growth and differentiation. However, we have discovered new evidence, which suggests that these proteins are functionally linked in a physiologic pathway required for cell survival and programmed cell death. Pharmacological activation of protein kinase C (PKC) or inducible overexpression and activation of the alpha isozyme of PKC (PKCalpha) resulted in approximately 60% apoptosis of mammary and prostate epithelial cells. Interestingly, the surviving cells had undergone dramatic aggregation concurrent with increased E-cadherin expression. When aggregation was inhibited by the addition of an E-cadherin-blocking antibody, apoptosis increased synergistically. We hypothesized that survival of the aggregated population was associated with contact-inhibited growth and that apoptosis might result from aberrant growth regulatory signals in non-aggregated, cycling cells. This hypothesis was confirmed by experiments that demonstrated that E-cadherin-dependent aggregation resulted in Rb-mediated G1 arrest and survival. Immunoblot analysis and flow cytometry revealed that hypophosphorylated Rb was present in non-aggregated, S phase cultures concurrent with synergistic cell death. We have also determined that the loss of membrane E-cadherin and subsequent hypophosphorylation of Rb in luminal epithelial cells preceded apoptosis induced by castration. These findings provide compelling evidence that suggests that E-cadherin-mediated aggregation results in Rb activation and G1 arrest that is critical for survival of prostate and mammary epithelial cells. These data also indicate that Rb can initiate a fatal growth signal conflict in non-aggregated, cycling cells when the protein is hypophosphorylated as these epithelial cells enter S phase.     

Chemico-enzymatic synthesis of branched O-specific polysaccharides of Salmonella serotype C2 and C3]

The possibility of chemical-enzymatic synthesis of branched polysaccharides was demonstrated with the enzymes from Salmonella newport and S. kentucky using synthetic polyprenyl pyrophosphate oligosaccharides. Formation of polymers with alpha 1-2-, beta 1-2-alpha 1-4- and beta 1-4-linkages between glucose residues in the branch and galactose residues of the main chain was shown.     

Dose fractionation effects in plateau-phase cultures of C3H 10T1/2 cells and their transformed counterparts

A comparison of gamma-ray dose fractionation effects was made using plateau-phase cultures of C3H 10T1/2 cells and their transformed counterparts in an attempt to simulate basically similar populations of cells that differ primarily in their turnover rates. The status of cell populations with respect to their turnover rates may be an important factor influencing dose fractionation effects in early- and late-responding tissues. In this cell culture system, the rate of cell turnover was approximately three times higher for the plateau-phase transformed cultures. While the single acute dose survival curves for log-phase cells were indistinguishable, there were significant differences between the survival curves for plateau-phase cultures of the two cell types. These differences were qualitatively similar to the differences recently postulated for the survival of target cells governing early and late tissue responses. Both cell lines had a similar capacity for repair of sublethal damage, but untransformed cells had a much greater capacity to repair potentially lethal damage in plateau phase. Further, untransformed plateau-phase cultures were much more sensitive to a radiation-induced G1 (or G0 to G1) delay than transformed cultures. Multifraction survival curves were determined for both cell lines for doses per fraction ranging from 9.0 to 0.8 Gy, and from these isoeffect curves of log total dose versus dose per fraction were derived. The isoeffect curve for the slowly cycling, untransformed cells was found to be appreciably steeper than that for the more rapidly cycling transformed cells, a finding consistent with previously reported differences in dose fractionation isoeffect curves for early- and late-responding tissues in vivo.     

The regulation of mononuclear phagocyte entry into S phase by the colony stimulating factor CSF-1

CSF-1 is a hemopoietic growth factor that specifically regulates the survival, proliferation, and differentiation of mononuclear phagocytic cells. Populations of adherent bone marrow-derived macrophages (BMM) devoid of CSF-1 producing cells were used to study regulation by CSF-1 of macrophage entry into S phase. More than 95% of BMM possess the CSF-1 receptor. It was shown that 93-98% of BMM are cycling (S phase 8-9 hr, doubling time 24-28 hr) when cultured in the presence of CSF-1. BMM incubated with 15% FCS in the absence of CSF-1 or in the presence of CSF-1 concentrations inducing survival without proliferation enter a quiescent state. This state is characterized by a reduction in the synthesis of DNA (98%), total protein (35%), ribosomal protein (76%), and histone (96%) compared with the synthetic rate of these components in exponentially growing cells. Addition of CSF-1 to BMM rendered quiescent by removal of CSF-1 stimulated entry into S phase with a lag period of approximately 12 h. This lag period is reduced to 8 hr in BMM made quiescent at concentrations of CSF-1 inducing survival without proliferation, an effect which may be related to the expected higher protein content of these cells (Tushinski and Stanley, J. Cell. Physiol., 116:67-75). Neutralization of CSF-1 by antibody at different times during the lag period indicates that CSF-1 is required for almost the entire lag period for the entry of any cells into S phase. In BMM rendered quiescent by removal of both serum and CSF-1, purified CSF-1 without serum stimulated entry of cells into S phase, whereas serum alone was ineffective. The results are consistent with a primary regulatory role of CSF-1 in mononuclear phagocyte proliferation, survival, and function.     

Salmonella typhi vaccine strain in vitro; low infectivity in human cell line U937

Salmonella typhi strain Ty21a has been used for live oral vaccine. The infectivity of Ty21a, in comparison with S. typhi Ty2, was evaluated using the human monocyte-macrophage cell line U937. Assays were performed by quantitative microscopy and viable count technique. Ty2 infected approximately 100% of the cells, multiplied extensively within these cells and caused cell death. The same dose of Ty21a infected only about 15% of the cells, resulting in a low number of intracellular bacilli and cell survival. The use of gentamicin in the test confirmed intracellular multiplication of Ty2 but not Ty21a. The system described may be suitable as a test system for characterization of the degree of virulence of Ty21a and other live, oral typhoid vaccines.     

Sensitivity of planktonic and biofilm-associated Salmonella spp. to ionizing radiation

Salmonella enterica forms biofilms that are relatively resistant to chemical sanitizing treatments. Ionizing radiation has been used to inactivate Salmonella on a variety of foods and contact surfaces, but the relative efficacy of the process against biofilm-associated cells versus free-living planktonic cells is not well documented. The radiation sensitivity of planktonic or biofilm-associated cells was determined for three food-borne-illness-associated isolates of Salmonella. Biofilms were formed on sterile glass slides in a coincubation apparatus, using inoculated tryptic soy broth, incubated at 37 degrees C for 48 h. Resulting biofilms were 18 to 24 microm in height as determined by confocal scanning laser microscopy. The planktonic and biofilm cultures were gamma irradiated to doses of 0.0 (control), 0.5, 1.0, 1.5, 2.0 and 2.5 kGy. The D(10) value (the dose of radiation required to reduce a population by 1 log(10), or 90%) was calculated for each isolate-culture based on surviving populations at each radiation dose. The D(10) values of S. enterica serovar Anatum were not significantly (P < 0.05) different for biofilm-associated (0.645 kGy) and planktonic (0.677 kGy) cells. In contrast, the biofilm-associated cells of S. enterica serovar Stanley were significantly more sensitive to ionizing radiation than the respective planktonic cells, with D(10) values of 0.531 and 0.591 kGy, respectively. D(10) values of S. enterica serovar Enteritidis were similarly reduced for biofilm-associated (0.436 kGy) versus planktonic (0.535 kGy) cells. The antimicrobial efficacy of ionizing radiation is therefore preserved or enhanced in treatment of biofilm-associated bacteria.     

Prevalence of Salmonella in chicken carcasses in Portugal

During 1986-87 57% of 300 chicken carcasses yielded salmonellas where tested by a swabbing method. Serotypes isolated were Salmonella enteritidis (66%), Salm. agona (12%), Salm. newport (6%), Salm. saintpaul (6%), Salm. derby (4%), Salm. typhimurium (3%), Salm. bardo (1%), Salm. ohio (1%) and untypable (2%). The results are compared with those of avian and human salmonellosis registered in Portugal during the same period.     

Characterization of two Salmonella newport bacteriophages

Salmonella newport phages 16--19 and 7--11 have very long heads and are members of two rare and so far little-known phage groups. Both produce various morphological aberrations. Preparations of phage 7--11 contain numerous polyheads and about 0.4% short heads belonging to nine size classes. In addition, one giant phage particle was observed. The head of phage 7--11 seems to be an icosahedron which became elongated by adding successive rows of subunits. Phages 16--19 and 7--11 have buoyant densities in CsCl of 1.43 and 1.48 g/mL and particle weights of 103 and 204 x 10(6) respectively. Both viruses contain double-stranded DNA, internal proteins, and sugars. Phage 16--19 contains 46.5% DNA of 35 x 10(6) molecular weight, and glucose. Phage 7--11 contains 47.5% DNA of 108 x 10(6) molecular weight, and mannose. Base compositions of phage and S. newport DNAs were determined from buoyant densities, melting point, and acid hydrolysis. Phage 16--19 contains 5.4% 5-methylcytosine.     

Prevalence of Salmonella in chicken carcasses in Portugal

M achado , J. & B ernardo , F. 1990. Prevalence of Salmonella in chicken carcasses in Portugal. Journal of Applied Bacteriology 69 , 477–480.
During 1986–87 57% of 300 chicken carcasses yielded salmonellas where tested by a swabbing method. Serotypes isolated were Salmonella enteritidis (66%), Salm. agona (12%), Salm. newport (6%), Salm. saintpaul (6%), Salm. derby (4%), Salm. typhimu-rium (3%), Salm. bardo (1%), Salm. ohio (1%) and untypable (2%). The results are compared with those of avian and human salmonellosis registered in Portugal during the same period.