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PubMedDate not supplied

Combined aztreonam and gentamicin therapy for pseudomonal lower respiratory tract infections.

A multicenter, open-label study was performed to assess the efficacy and safety of aztreonam plus gentamicin in the treatment of lower respiratory tract infections due to Pseudomonas aeruginosa. Patients with documented P aeruginosa infections were given aztreonam 2 g every 8 hours (q8h) plus gentamicin 3 to 5 mg/kg per day in three equal doses. Clindamycin, 600 mg q8h, was added to the regimen for patients with infections also involving gram-positive and/or anaerobic bacteria. Therapy was continued for at least 5 days or until obvious failure to respond to treatment. Of 64 patients with suspected P aeruginosa infections, 57 were eligible for clinical evaluation and 51 for microbiologic evaluation. At entry, impaired host defense was present in 35% of patients, and chronic obstructive pulmonary disease in 28%, in addition to other predisposing conditions such as emphysema, history of tuberculosis, and pneumothorax. The clinical response rate for the combination regimen was 48/57 (84%), which included 27 (47%) cures and 21 (37%) partial responses. The microbiologic response rate was 35/51 (69%), of which 25 (49%) outcomes were classified as eradication and 10 (20%) as eradication with relapse. Superinfection was observed in 3 (6%) patients. The combination of aztreonam and gentamicin was synergistic in the initial isolates obtained from 33 (72%) patients. A total of 16 patients died of pulmonary or other underlying disease, for a mortality rate of 28%. The monobactam-aminoglycoside combination was generally well tolerated. Two other patients were withdrawn because rashes emerged on treatment. This study demonstrates that aztreonam can be administered as one component of a synergistic monobactam-aminoglycoside therapy in the treatment of nosocomial lower respiratory tract infections involving P aeruginosa.

Adult↗
PubMed1996

Peptidoglycan synthesis and structure in Staphylococcus haemolyticus expressing increasing levels of resistance to glycopeptide antibiotics.

The structures of cytoplasmic peptidoglycan precursor and mature peptidoglycan of an isogenic series of Staphylococcus haemolyticus strains expressing increasing levels of resistance to the glycopeptide antibiotics teicoplanin and vancomycin (MICs, 8 to 32 and 4 to 16 microg/ml, respectively) were determined. High-performance liquid chromatography, mass spectrometry, amino acid analysis, digestion by R39 D,D-carboxypeptidase, and N-terminal amino acid sequencing were utilized. UDP-muramyl-tetrapeptide-D-lactate constituted 1.7% of total cytoplasmic peptidoglycan precursors in the most resistant strain. It is not clear if this amount of depsipeptide precursor can account for the levels of resistance achieved by this strain. Detailed structural analysis of mature peptidoglycan, examined for the first time for this species, revealed that the peptidoglycan of these strains, like that of other staphylococci, is highly cross-linked and is composed of a lysine muropeptide acceptor containing a substitution at its epsilon-amino position of a glycine-containing cross bridge to the D-Ala 4 of the donor, with disaccharide-pentapeptide frequently serving as an acceptor for transpeptidation. The predominant cross bridges were found to be COOH-Gly-Gly-Ser-Gly-Gly-NH2 and COOH-Ala-Gly-Ser-Gly-Gly-NH2. Liquid chromatography-mass spectrometry analysis of the peptidoglycan of resistant strains revealed polymeric muropeptides bearing cross bridges containing an additional serine in place of glycine (probable structures, COOH-Gly-Ser-Ser-Gly-Gly-NH2 and COOH-Ala-Gly-Ser-Ser-Gly-NH2). Muropeptides bearing an additional serine in their cross bridges are estimated to account for 13.6% of peptidoglycan analyzed from resistant strains of S. haemolyticus. A soluble glycopeptide target (L-Ala-gamma-D-iso-glutamyl-L-Lys-D-Ala-D-Ala) was able to more effectively compete for vancomycin when assayed in the presence of resistant cells than when assayed in the presence of susceptible cells, suggesting that some of the resistance was directed towards the cooperativity of glycopeptide binding to its target. These results are consistent with a hypothesis that alterations at the level of the cross bridge might interfere with the binding of glycopeptide dimers and therefore with the cooperative binding of the antibiotic to its target in situ. Glycopeptide resistance in S. haemolyticus may be multifactorial.

Amino Acid Sequence↗
PubMed1991

T helper cell-dependent, microbial superantigen-induced murine B cell activation: polyclonal and antigen-specific antibody responses.

Microbial superantigens (SA), bound to human B cell surface MHC class II molecules, have been shown to promote direct, "cognate" interaction with SA-reactive autologous Th cells, resulting in polyclonal Ig production. To investigate the potential for microbial SA to support Th cell-dependent, Ag-specific antibody responses, we have extended our studies to the murine system. BALB/c Th cell lines (TCL), specific for either the Mycoplasma arthritis-derived SA or the Staphylococcus aureus-derived toxic shock syndrome toxin-1) were generated. These TCL cells are SA-specific, functionally noncross-reactive, and utilize distinct TCR V beta gene families. Coculture of SA-reactive TCL cells and syngeneic B cells bearing the relevant SA results in B cell proliferation and polyclonal IgM and IgG production. In contrast, Ag-specific (SRBC-specific) antibody-forming cells are only generated in cultures that also contain SRBC. Thus, microbial SA-mediated Th-B cell interactions induce both polyclonal B cell activation and provide selective help for the proliferation and/or differentiation of B cells that have encountered specific Ag. In additional studies, we determined that the in vivo administration of toxic shock syndrome toxin-1 to young, athymic (nude) BALB/c mice results in SA binding to splenic B cells, rendering these B cells effective stimulators of and targets for SA-reactive helper TCL cells. Taken together, these results demonstrate that microbial SA mediate productive Th-B cell interactions analogous to those that occur during allospecific Th-B cell interactions in vitro and GVHD in vivo. These findings are consistent with the hypothesis that microbial SA represent environmental factors that may trigger autoimmune disease in the genetically susceptible host.

Animals↗
PubMed1992

Sch 42137, a novel antifungal antibiotic from an Actinoplanes sp. Fermentation, isolation, structure and biological properties.

A novel polycyclic xanthone, Sch 42137, related to the albofungin family of compounds was isolated from culture broth. Its structure was determined by detailed spectroscopic studies and comparison of circular dichroic studies to related compounds albofungin and simaomicin. Sch 42137 exhibited MIC values less than 0.125 micrograms/ml against yeasts and dermatophytes. Details are presented herein.

Actinomyces↗
PubMed1995

Mutational analysis of the redox-sensitive transcriptional regulator OxyR: regions important for oxidation and transcriptional activation.

OxyR is a redox-sensitive transcriptional regulator of the LysR family which activates the expression of genes important for the defense against hydrogen peroxide in Escherichia coli and Samonella typhimurium. OxyR is sensitive to oxidation and reduction, and only oxidized OxyR is able to activate transcription of its target genes. Using site-directed mutagenesis, we found that one cysteine residue (C-199) is critical for the redox sensitivity of OxyR, and a C-199-->S mutation appears to lock the OxyR protein in the reduced form. We also used a random mutagenesis approach to isolate eight constitutively active mutants. All of the mutations are located in the C-terminal half of the protein, and four of the mutations map near the critical C-199 residue. In vivo as well as in vitro transcription experiments showed that the constitutive mutant proteins were able to activate transcription under both oxidizing and reducing conditions, and DNase I footprints showed that this activation is due to the ability of the mutant proteins to induce cooperative binding of RNA polymerase. Unexpectedly, RNA polymerase was also found to reciprocally affect OxyR binding.

Amino Acid Sequence↗
PubMedDate not supplied

Evaluation of poly(styrene-4-sulfonate) as a preventive agent for conception and sexually transmitted diseases.

A commercial preparation of a sodium polystyrene sulfonate (designated as N-PSS; its molecular weight is 500000 daltons) was tested as an inhibitor of sperm function and as a preventive agent for conception and the transmission of sexually transmitted diseases. The polymer is an irreversible inhibitor of hyaluronidase and acrosin; its IC50 values are 5.7 microg/mL and 0.5 microg/mL, for hyaluronidase and acrosin, respectively. N-PSS is also a stimulus of human sperm acrosomal loss. It produces maximal acrosomal loss at 2.5 microg/mL. Contraception in rabbits is nearly complete when rabbit spermatozoa are pretreated with 0.5 mg/mL of N-PSS before artificial insemination; however, N-PSS does not immobilize spermatozoa at concentrations as high as 50 mg/mL. N-PSS has broad spectrum antiviral and antibacterial activities. Infection by human immunodeficiency virus and herpes simplex virus are inhibited by N-PSS; 3-log reductions are produced by 7 microg/mL and 3 microg/mL, respectively. N-PSS is active against Chlamydia trachomatis and Neisseria gonorrhoeae. At 1 mg/mL, N-PSS inhibits chlamydial infectivity by more than 90%. N-PSS produces a 3-log reduction in gonococcal growth at 15 microg/mL. In contrast, N-PSS (5 mg/mL) does not affect the growth of Lactobacillus (normal component of the vaginal flora). N-PSS can be classified as a noncytotoxic contraceptive antimicrobial agent. These properties justify bringing a polystyrene sulfonate into clinical trials for its evaluation as a preventive agent for conception and several sexually transmitted diseases.

Animals↗
PubMed2006

[Optimizing delayed reconstruction of complex pressure sores by V.A.C. therapy].

V.A.C.-therapy has improved the treatment of extended pressure sores, because of its beneficial effect on the wound surface and the safe microbial barrier. Definitive reconstructive surgery can be performed earlier. Using modern aids fixation of the device will be possible even in difficult locations as the perianal area. This is important for immobile and multi-morbid patients. On the other hand, this area still shows limitations of the method. In recurrent cases it is difficult to use classical methods of reconstruction. Long-term-treatment is necessary, which is economically difficult. It is important for hospitals to cooperate with specialised wound therapeutics so that these patients can be dismissed earlier. This may allow reconstructive procedures, even if this takes several hospital stays over a long period of time.

Buttocks↗
PubMed1994

Comparative mutagenicity of chemicals selected for test in the International Program on Chemical Safety's collaborative study on plant systems for the detection of environmental mutagens.

A review has been made for the four compounds (maleic hydrazide, methyl nitrosourea, sodium azide, azidoglycerol) tested in the International Program on Chemical Safety's collaborative study on plant systems. Maleic hydrazide (MH) is a weak cytotoxic/mutagenic chemical in mammalian tissues and is classified as a class 4 chemical. In contrast, with few exceptions such as Arabidopsis, MH is a potent mutagen/clastogen in plant systems. The difference in its response between plant and animal tissue is likely due to differences in the way MH is metabolized. MH appears to be noncarcinogenic and has been given a negative NCI/NTP carcinogen rating. Methyl nitrosourea (MNU) is a toxic, mutagenic, radiomimetic, carcinogenic, and teratogenic chemical. It has been shown to be a mutagen in bacteria, fungi, Drosophila, higher plants, and animal cells both in vitro and in vivo. MNU is a clastogen in both animal and human cell cultures, plant root tips and cell cultures inducing both chromosome and chromatid aberrations as well as sister-chromatid exchanges. Carcinogenicity has been confirmed in numerous studies and involves the nervous system, intestine, kidney, stomach, bladder and uterus, in the rat, mouse, and hamster. MNU produces stage-specific teratogenic effects and also interferes with embryonic development. The experimental evidence that strongly indicates the mutagenic effects of MNU underlines the possible hazard of this compound to human beings. The experimental evidence for the stringent handling of this compound is clear. Sodium azide (NaN3) is cytotoxic in several animal and plant systems and functions by inhibiting protein synthesis and replicative DNA synthesis at low dosages. It is mutagenic in bacteria, higher plants and human cells and has been used as a positive control in some systems. In general, tests for clastogenicity have been negative or weakly positive. No evidence of carcinogenicity has been reported in a 2-year study seeking carcinogenic activity in male and female rats. Its advantages in comparison to other efficient mutagens are claimed to be a high production of gene mutations accompanied by a low frequency of chromosomal rearrangements and safer handling because of its nonclastogenic and noncarcinogenic action on humans. Azidoglycerol (AG) is a very potent mutagen in bacteria, yeast and higher plants including Arabidopsis and Tradescantia; however, it only slightly enhances the frequencies of recessive lethals in Drosophila. AG is at best a weak clastogen and is without effect in inducing chromosomal aberrations and SCEs in human peripheral lymphocytes in vitro. In microbial and plant systems, AG is considerably more potent than sodium azide in the maximal frequencies of mutation induced. In particular, in Saccharomyces cerevisae, AG is 3000-fold more mutagenic than sodium azide. Its carcinogenic and teratogenic properties are unknown.

Animals↗
PubMed2006

Modular determinants of antimicrobial activity in platelet factor-4 family kinocidins.

Mammalian platelets contain an array of antimicrobial peptides, termed platelet microbicidal proteins (PMPs). Human and rabbit PMPs include known chemokines, such as platelet factor-4 (hPF-4); PMP-1 is the rabbit orthologue of hPF-4. Chemokines that also exert direct antimicrobial activity have been termed kinocidins. A consensus peptide domain library representing mammalian PF-4 family members was analyzed to define structural domains contributing to antimicrobial activity against a panel of human pathogens. Secondary conformations were assessed by circular dichroism spectrometry, and molecular modeling was employed to investigate structural correlates of antimicrobial efficacy. Antimicrobial activity against isogenic peptide-susceptible or -resistant Staphylococcus aureus, Salmonella typhimurium, and Candida albicans strain pairs mapped to the C-terminal hemimer (38-74) and modular domains thereof (49-63 and 60-74). Increasing electrostatic charge and steric bulk were general correlates of efficacy. Structural data corroborated spatial distribution of charge, steric bulk and putative secondary structure with organism-specific efficacy. Microbicidal efficacies of the cPMP antimicrobial hemimer and C-terminal peptide (60-74) were retained in a complex human-blood biomatrix assay. Collectively, these results suggest that modular determinants arising from structural components acting independently and cooperatively govern the antimicrobial functions of PF-4 family kinocidins against specific target pathogens.

Amino Acid Sequence↗
PubMed2006

Dual detection of fungal infections in Drosophila via recognition of glucans and sensing of virulence factors.

The Drosophila immune system discriminates between various types of infections and activates appropriate signal transduction pathways to combat the invading microorganisms. The Toll pathway is required for the host response against fungal and most Gram-positive bacterial infections. The sensing of Gram-positive bacteria is mediated by the pattern recognition receptors PGRP-SA and GNBP1 that cooperate to detect the presence of infections in the host. Here, we report that GNBP3 is a pattern recognition receptor that is required for the detection of fungal cell wall components. Strikingly, we find that there is a second, parallel pathway acting jointly with GNBP3. The Drosophila Persephone protease activates the Toll pathway when proteolytically matured by the secreted fungal virulence factor PR1. Thus, the detection of fungal infections in Drosophila relies both on the recognition of invariant microbial patterns and on monitoring the effects of virulence factors on the host.

Animals↗
PubMed1975

Factors affecting the time course of decay of end-plate currents: a possible cooperative action of acetylcholine on receptors at the frog neuromuscular junction.

1. End-plate currents have been studied in gylcerol-treated frog sartorius nerve-muscle preparations with the voltage-clamp technique. 2. Adding the anticholinesterase prostigmine (3 muM) to the solution bathing the muscle caused a 2-7 (mean 3-3) times increase in the time constant of decay of end-plate currents. The anticholinesterase edrophonium (15 muM) also prolonged the time course of end-plate currents. 3. Pre-treatment of the preparation with collagenase, which leads to the removal of acetylcholinesterase in the synaptic cleft, prolongs the time course of end-plate currents. 4. Curare (1-2 muM), cobratoxin (0-13 muM), or alpha-bungarotoxin (0-13-0-26 muM) decreased the time constant of decay of end-plate currents in the presence of prostigmine. 5. These observations are consistant with the suggestion that repeated binding of acetylcholine (ACh) molecules to receptors as the ACh escapes from the synaptic cleft can contribute to the prolongation of end-plate currents which occurrs when acetylcholinesterase activity is eliminated. 6. Increasing the amount of transmitter released from the presynaptic nerve terminal leads to a prolongation of end-plate currents in the presence of prostigmine. 7. In the presence of prostigmine, the second of two end-plate currents (interval 2-10 msec) decays more slowly than the first. 8. ACh (1-40 muM) or carbachol (40 muM) applied in the solution bathing the muscle prolongs end-plate currents in the presence of prostigmine. 9. It is suggested on the basis of the observations described in paragraphs 6 to 8 that the time constant of decay of end-plate currents in the presence of prostigmine increases with increasing concentrations of ACh in the synaptic cleft. In the absence of prostigmine, increasing the concentration of ACh in the synaptic cleft did not change the time constant for decay of end-plate currents. 10. We interpret these results to suggest that ACh can have a cooperative action on receptors such that the association of ACh with one receptor (defined as binding a single ACh molecule) favours the binding or retention of ACh at other receptors. This implies that receptors can interact.

Acetylcholine↗
PubMedDate not supplied

[Air purification aboard space vehicles].

Air purification unit POTOK 150MK has been designed to clean air of space vehicles from microbial contaminant. Comparison of the data of analysis of air samples collected in different periods of operation of the space station MIR and ISS reconfirmed efficiency of the unit.

Air Microbiology↗
PubMed1997

The clinical microbiology laboratory and infection control: emerging pathogens, antimicrobial resistance, and new technology.

The clinical microbiology laboratory is an essential component of an effective infection control program. Laboratory personnel have a broad range of technologies, from traditional methods of detecting and identifying organisms to modern molecular typing methods, that they can use to support and enhance the efforts of the infection control staff. If the infection control team applies these technologies appropriately, it can prevent problems and solve nosocomial mysteries efficiently. In this era of cost-containment, staff members in the laboratory and in the infection control program must work hard to communicate their unique and shared goals, needs, and problems. If the laboratory and infection control personnel cooperate and collaborate rather than compete, both programs will be successful and the patients and the hospital will benefit because the risk of nosocomial infections and the frequency of resistant organisms will be reduced.

Bacterial Typing Techniques↗
PubMed2004

Paradoxical effect of caspofungin: reduced activity against Candida albicans at high drug concentrations.

Resistance problems with caspofungin, an echinocandin inhibitor of fungal cell wall glucan synthesis, have been rare. We noted paradoxical turbid growth of Candida albicans isolates in broth in some high (supra-MIC) concentrations. Among isolates submitted for susceptibility testing and screened at drug concentrations up to 12.5 microg/ml, the frequency was 16%. Analysis of the turbid growth indicated slowing of growth in the presence of drug but with numbers of CFU up to 72% those of drug-free controls. Clearing of growth again by the highest drug concentrations produced a quadriphasic pattern in a tube dilution series. Cells growing at high drug concentrations were not resistant on retesting but showed the paradoxical effect of the parent. Among a selected series of isolates tested at concentrations up to 50 microg/ml, an additional 53% showed a "mini-paradoxical effect": no turbid growth but incomplete killing at high concentrations (supra-minimum fungicidal concentration). These effects were reproducible; medium dependent in extent; noted in macro- and microdilution, in the presence or absence of serum, and on agar containing drug (but not when drug concentrations were not constant, as in agar diffusion); not seen with other echinocandins and less commonly in other Candida species; and not due to destruction of drug in tubes showing the effect. Cooperative enhancement of inhibition by a second drug could eradicate the effect. We postulate that high drug concentrations derepress or activate resistance mechanisms. The abilities of subpopulations to survive at high drug concentrations could have in vivo consequences.

Antifungal Agents↗
PubMed1992

Repression of the E. coli lactose operon by cooperation between two individually unproductive "half-operator" sites.

Two remote and weak lac regressor binding sites can be used jointly to repress the synthesis of beta-galactosidase in E. coli, while they cannot separately. When this result is discussed in reference to the various modes of cooperation between the sites, it supports with a new approach a model implying the simultaneous binding of lac repressor to both sites with the formation of a DNA loop. In connection with this point, we present a new strategy to detect cooperative interactions in vivo, based on the asymmetry of the DNA binding site, formally equivalent here to a half-site, heterodimerization of the protein, and influence of orientation of the sites on repression at short and long distance.

DNA, Bacterial↗
PubMed2000

Triple therapy for Helicobacter pylori eradication: a comparison of pantoprazole once versus twice daily.

BACKGROUND: Proton pump inhibitor-based triple therapy is recommended as treatment for Helicobacter pylori eradication. The proton pump inhibitor may be given once or twice daily. However, little information is available on how these two treatment strategies compare. METHODS: H. pylori-positive patients (two positive test results) with endoscopy-proven healed duodenal ulcer or non-ulcer dyspesia were randomly allocated to 1 week of double-blind treatment with pantoprazole 40 mg once or twice daily, plus clarithromycin 250 mg and metronidazole 400 mg twice daily. Eradication was defined as a negative 13C-urea breath test (13C-UBT) and histology, 4-5 weeks post-treatment. The follow-up phase comprised 12 months off therapy, with 13C-UBT at 6 and 12 months. RESULTS: Two hundred and four patients received treatment: pantoprazole once daily (x1), n=104; twice daily (x2), n=100. Eradication rates were 84% in both the pantoprazole x1 and pantoprazole x2 groups by modified intention-to-treat analysis and 89% and 87%, respectively, by per protocol analysis. Metronidazole resistance was found in 44% of pre-treatment cultures of H. pylori. Eradication rates were similar in susceptible (72%) and resistant (75%) strains. During follow-up, recrudescence of infection occurred in 3/118 patients. CONCLUSION: When using pantoprazole plus clarithromycin and metronidazole, the proton pump inhibitor can be used once daily without loss of efficacy.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed2001

Novel macrolide-specific ABC-type efflux transporter in Escherichia coli.

In the Escherichia coli genome, five putative open reading frame (ORF) clusters, mdlAB, ybjYZ, yddA, yojHI, and yhiH, have been assumed to be possible genes for ABC drug efflux transporters (I. T. Paulsen, M. K. Sliwinski, and M. H. Saier, Jr., J. Mol. Biol. 277:573-592, 1998). We cloned all of these ORFs in multicopy plasmids and investigated the drug resistance of drug-supersensitive host cells lacking constitutive multidrug efflux transporter genes acrAB. Among them, only ybjYZ gave significant erythromycin resistance and significantly decreased the accumulation of [(14)C]erythromycin. Therefore, ybjYZ was renamed macAB (macrolide-specific ABC-type efflux carrier). Plasmids carrying both the macA and -B genes conferred resistance against macrolides composed of 14- and 15-membered lactones but no or weak resistance against 16-membered ones. Neither of the two genes produced resistance alone. The DNA sequence suggests that MacB is an integral membrane protein with four transmembrane segments and one nucleotide-binding domain, while MacA belongs to a membrane fusion protein (MFP) family with a signal-like sequence at its N terminus. The expression of the histidine-tagged proteins confirmed that MacB is an integral membrane protein and MacA is a peripheral membrane protein. In addition, MacAB required TolC for its function in a way similar to that of most of the MFP-dependent transporters in E. coli. MacB is thus a novel ABC-type macrolide efflux transporter which functions by cooperating with the MFP MacA and the multifunctional outer membrane channel TolC. This is the first case of an experimentally identified ABC antibiotic efflux transporter in gram-negative organisms.

ATP-Binding Cassette Transporters↗
PubMed1975

[Genetic study of Escherichia coli K-12 mutants resistant to 2,6-diaminopurine].

Mutants, resistant to the inhibitory effect of 2,6-diaminopurine and incapable of utilizing adenine as a purine source, are obtained from purinenucleoside phosphorylase-defective purine-dependent Escherichia coli K-12 strains. The mutations obtained (apt) disturb the uptake of adenosine and inosine only in the presence of a mutation for purinenucleoside phosphorylase (pup gene) in the genome of purine-dependent bacteria. The introduction of pup+ allele into the genome of mutants obtained (genotype purDpup apt) results in the restoration of the ability to uptake adenine and purine ribosides. Strains of purDpup+apt genotype are characterized by more short generation time under the growth in the presence of adenine as compared with purDpup apt+ strains which indicates the existance of an efficient pathway of adenine utilization in E. coli with the cooperation of purinenucleoside phosphorylase. Mutations apt have revealed a combined transfer with purE marker under the transduction frequency of approximately 5%. The gene order on E. coli K-12 chromosome is apt-purE-gal, as estimated from the data on conjugation crosses.

Drug Resistance, Microbial↗