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PubMed2001

Antibiotic resistance with particular reference to soil microorganisms.

Evidence of increasing resistance to antibiotics in soil and other natural isolates highlights the importance of horizontal transfer of resistance genes in facilitating gene flux in bacteria. Horizontal gene transfer in bacteria is favored by the presence of mobile genetic elements and by the organization of bacterial genomes into operons allowing for the cooperative transfer of genes with related functions. The selective pressure for the spread of resistance genes correlates strongly with the clinical and agricultural overuse of antibiotics. The future of antimicrobial chemotherapy may lie in developing new antimicrobials using information from comparative functional microbial genomics to find genetic targets for antimicrobials and also to understand gene expression enabling selective targeting of genes with expression that correlates with the infectious process.

Anti-Bacterial Agents↗
PubMed2003

Rates of transmission of antiretroviral drug resistant strains of HIV-1.

BACKGROUND: It is clear that transmission of drug resistant HIV-1 is possible and occurs regularly. However, there is a lack of clarity concerning the true rate of this transmission in a given population, the impact of combination therapies on this rate, and the contribution of transmitted resistant virus to treatment failure either in an individual or on a population basis. OBJECTIVES: To provide a review of our current understanding of rates of transmission of drug resistant HIV-1 in various populations and to report the results of a study conducted to determine this rate in Sydney, Australia in the years 1992-2000. STUDY DESIGN: A review of the literature combined with a prospective study of antiretroviral drug resistance in 130 individuals who were diagnosed with symptomatic primary infection at St. Vincent's Hospital, Sydney, Australia between 1992 and 2000. Sequencing of reverse transcriptase (RT) and protease (PR) was performed by the TruGene HIV-1 genotyping kit (Visible Genetics Inc.). RESULTS: The results found in the Sydney population contrast with much of the literature. The prevalence of mutations that conferred primary resistance to protease inhibitors (PIs) was only 0.8% at position V82I. Secondary mutations/polymorphisms were seen in the PR at position L10I/V, K20R, M36I, L63P, A71T/V, or V77I in 60%. L63P was the most frequently found mutation (46.3%). The incidence of protease-resistant strains of HIV in primary HIV-1 infection did not change after the introduction of PIs in 1996. The distribution of the most common resistance mutations in the RT was as follows; M41L (8.5%) and T215Y (8.5%) and K70R (4.8%). The frequency of mutations associated with NRTI resistance was significantly lower in the post 1995 samples (43.9 vs. 19.1%, P < 0.05). Moreover, both M41L and K70R, but not T215Y, occurred with significantly decreased frequency in the post 1995 samples. CONCLUSIONS: In contrast to other studies we found no increase in the rate of PR resistance and a decrease in the rate of RT resistance in recently transmitted virus over the period 1992-2000. The reasons for the differences between these results and those reported from elsewhere may relate to treatment regimens used in the transmitting population and may have implications for treatment policies in this country.

Anti-HIV Agents↗
PubMed1976

An outbreak of shigellosis in laboratory marmosets and tamarins (Family: Callithricidae).

An outbreak of shigellosis due to Shigella sonnei, is reported in laboratory maintained marmosets (Callithrix jacchus) and tamarins (Saguinus nigricollis). The clinical signs and pathological lesions are described and the microbiological findings discussed. Control of the disease was based upon hygiene and antibiotic therapy and the consequences of this approach are described in detail.

Animals↗
PubMed2000

Strategies for study of the role of cycling on antimicrobial use and resistance.

Resistant bacteria usually are seen first in the intensive care unit and other acute-care areas. Thus, strategies to control these organisms often are first tested in these healthcare settings. Frequent among these strategies are attempts to improve antimicrobial use. One proposed method to decrease resistance in special settings like the intensive care unit is the cycling or rotation of antimicrobials. This intervention must be evaluated in the context of other concomitant attempts to improve antimicrobial usage and must take into account other factors influencing resistance. Until such studies are done, the value of cycling and other efforts to limit prescribers' choices of drugs in endemic settings will be unclear. Studies to evaluate cycling will have to be of large scale to produce useful data. It is unlikely that many hospitals or healthcare systems will have sufficient resources on their own to develop studies of sufficient power to be applied widely. Thus, cooperative studies to provide data on this important issue should be an international priority.

Anti-Bacterial Agents↗
PubMed1992

In-vitro activity of tosufloxacin, a new quinolone antibacterial agent.

The in-vitro activity of tosufloxacin (A-61827) was compared with that of temafloxacin, ciprofloxacin and selected members of other groups of antimicrobial agents, against 684 recent distinct clinical isolates and strains with known mechanisms of resistance. Against members of the Enterobacteriaceae, ciprofloxacin was slightly more active than tosufloxacin, which was more active than temafloxacin. The MIC90 of tosufloxacin for all species of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter spp. was less than or equal to 1 mg/L. Tosufloxacin was slightly more active than temafloxacin, and four to eight fold more active than ciprofloxacin, against the Gram-positive species tested. The MIC90 of tosufloxacin for Staphylococcus aureus was 0.12 mg/L, and for Streptococcus pneumoniae was 0.5 mg/L. All strains of Neisseria spp., Haemophilus influenzae and Moraxella catarrhalis were inhibited by tosufloxacin at a concentration of less than or equal to 0.12 mg/L. Tosufloxacin was the most active quinolone against the anaerobic organisms tested. Cross resistance between quinolones was seen, but not between quinolones and other groups of antimicrobials. The protein binding of tosufloxacin across a range of concentrations averaged 60%. Human serum at a concentration of 70% decreased the bactericidal activity of tosufloxacin by about four-fold.

4-Quinolones↗
PubMed1998

Pneumococci causing invasive disease in Britain 1982-1990.

A total of 5348 isolates of Streptococcus pneumoniae was serotyped and screened for insusceptibility to tetracycline, penicillin, erythromycin and chloramphenicol. Of these, 4238 (79%) were isolated from patients who had pneumonia or meningitis or were bacteraemic. Altogether, 3948 (74%) of the isolates belonged to one or other of the serotypes 1, 3, 4, 6, 8, 9, 14, 19 or 23 with serotypes 6, 14, 18, 19 and 23 being frequent causes of invasive disease in young children. Many isolates of type 1 were isolated from pneumonia and few from meningitis. Some 768 (14%) isolates were insusceptible to one or more antibiotic and 591 of these belonged to serotypes 6, 9, 14, 19 or 23. Representatives of type 14 resistant to erythromycin were prominent from 1986 onwards. There was an increase in the number of multi-resistant pneumococci from 1985. Among these were isolates of type 23 insusceptible to penicillin, chloramphenicol and tetracycline and cultures of type 6 resistant additionally to erythromycin.

Adolescent↗
PubMed1996

Cooperative anti-Candida effects of lactoferrin or its peptides in combination with azole antifungal agents.

The effects of lactoferrin (LF), an antimicrobial protein secreted in body fluids, and its peptides in combination with azole antifungal agents were investigated by the micro-broth-dilution method in a study of Candida albicans. In the case of LF, its pepsin hydrolysate (LFhyd) or the LF-derived antimicrobial peptide Lactoferricin B (LF-B), the concentrations required to inhibit the growth of Candida decreased in the presence of relatively low concentrations of clotrimazole (CTZ). The minimum inhibitory concentration (MIC) of all azole antifungal agents tested was reduced by 1/4-1/16 in the presence of a sub-MIC level of each of these LF-related substances. Polyene and fluoropyrimidine antifungal agents did not show such a combined effect with these LF-related substances. The anti-Candida activity of LF or LF-B in combination with CTZ was shown to be synergistic by checkerboard analysis. These results indicate that LF-related substances function cooperatively with azole antifungal agents against C. albicans.

Antifungal Agents↗
PubMed1983

Analysis of tetracycline resistance encoded by transposon Tn10: deletion mapping of tetracycline-sensitive point mutations and identification of two structural genes.

Deletions in the tet genes derived from Tn10 were formed from different tet::Tn5 insertion mutations by removing DNA sequences located between a HindIII site in Tn5 and a HindIII site adjacent to the tet genes. Tetracycline-sensitive point mutations were mapped in recombination tests with the deletions and were thus aligned with the genetic and physical map of the tet region. Plasmids carrying point mutations were tested for complementation with derivatives of pDU938, a plasmid carrying cloned tet genes derived from Tn10 which had been inactivated by Tn5 insertions. Complementation occurred between promoter-proximal tet point mutations and distal tet::Tn5 insertions, suggesting the existence of two structural genes, tetA and tetB. These results, together with the analysis of polypeptides in minicells harboring pDU938tet::Tn5 mutants, suggested that tetA and tetB are expressed coordinately in an operon. The tetB gene encodes the previously characterized 36,000-dalton cytoplasmic membrane TET protein, but the product of tetA was not identified. Point mutations in either tetA or tetB led to the defective expression of the resistance mechanism involving tetracycline efflux. It is suggested that the tetA and tetB products interact cooperatively in the membrane to express resistance.

Biological Transport↗
PubMed2005

Complexity and complementarity of outer membrane protein A recognition by cellular and humoral innate immunity receptors.

Outer membrane protein A (OmpA) is a conserved major component of the outer membrane of Enterobacteriaceae. Here, we report that OmpA from Klebsiella pneumoniae (KpOmpA) activates macrophages and dendritic cells (DCs) in a TLR2-dependent way. However, TLR2 does not account for binding of KpOmpA to innate immune cells. KpOmpA binds the scavenger receptors (SRs) LOX-1 and SREC-I, but not other members of the same family. LOX-1 colocalizes and cooperates with TLR2 in triggering cellular responses. The TLR2-activated functional program includes production of the long pentraxin PTX3, a soluble pattern recognition receptor involved in resistance against diverse pathogens. PTX3, in turn, binds KpOmpA but does not affect recognition of this microbial moiety by cellular receptors. KpOmpA-elicited in vivo inflammation is abrogated in TLR2(-/-) mice and significantly reduced in PTX3(-/-) mice. Thus, SR-mediated KpOmpA recognition and TLR2-dependent cellular activation set in motion a nonredundant PTX3-mediated humoral amplification loop of innate immunity.

Animals↗
PubMed1984

Increased phagocytosis and killing of Escherichia coli treated with subinhibitory concentrations of cefamandole and gentamicin in isolated rat livers.

Our purpose was to study whether treatment of Escherichia coli with subinhibitory concentrations of either cefamandole or gentamicin could change bacterial susceptibility to the serum bactericidal effect and to the phagocytic and killing activity of the rat liver reticuloendothelial system. Bacteria were grown overnight with 1/5 or 1/10 of the MIC of each antibiotic. At one-fifth of the MIC, cefamandole induced filamentous elongated bacteria whose viability was decreased by 75%. The susceptibility of control and antibiotic-treated bacteria to serum was tested by measuring the survival of organisms exposed to different concentrations of rat serum in vitro. Susceptibility of bacteria to hepatic macrophage activity was tested by following the hepatic clearance of bacteria after they were added to the perfusate of the isolated rat liver. E. coli treated with subinhibitory concentrations of cefamandole or gentamicin appeared somewhat more resistant to the lytic activity of serum at a concentration of 4%, but not at 20%. Bacteria treated with 1/5 or 1/10 of the MIC of cefamandole or with 1/5 of the MIC of gentamicin were significantly more susceptible to phagocytosis and to the bactericidal activity of liver macrophages. Cefamandole appeared more potent than gentamicin in inducing these effects. The results suggest that subinhibitory levels of antibiotics may alter bacterial cell surface (cefamandole) or may impair the expression of antiphagocytic material (gentamicin), thus favoring phagocytosis and killing by macrophages. Our study provides evidence that antibiotics at subinhibitory concentrations may cooperate with host defence mechanisms against bacterial infections.

Animals↗
PubMed1994

[Diagnostic possibility in neonatal bacterial infections].

Bacterial infections in neonates may be acquired in utero, as is the case in congenital syphilis, or after delivery, such as late onset B streptococcal meningitis. Although some infections remain localized and may even be self-limiting, the majority of neonatal bacterial infections require speedy diagnosis and immediate and appropriate treatment. Severe invasive bacterial infections are rare but catastrophic; they are more common in intensive care wards. Neonatal, maternal, and environmental factors favoring bacterial infections are discussed together with their main clinical features. Useful diagnostic parameters are examination of the placenta, leukocyte counting, erythrocyte sedimentation rate, and C-reactive protein. If a bacterial infection is suspected in a baby that is sick or in poor general condition (low birth weight, therapies, environmental conditions) a "septic therapeutic approach" must be adopted which includes examination and culture of blood, cerebrospinal fluid, and urine, as well as of any other suitable material according to clinical and laboratory findings. Pathogens most frequently involved in neonatal infections (streptococci, staphylococci, Listeria, gram-negative enteral bacteria) can be presumptively identified by comparatively simple laboratory tests. The valid interpretation of the results of these tests is dependent upon the degree to which the laboratory personnel is familiar with techniques of identification and assessment of sensitivity, as well as on the close cooperation between clinical department and laboratory from the start and all along the course of the disease.

Bacterial Infections↗
PubMed1985

Potential food safety problems in genetic engineering.

The rapid development of gene technology, exemplified by the recombinant DNA technique and the hybridoma technique, will heavily influence our food supply in the years to come. Fermentation products from genetic-engineered microbials, the microbials themselves and new plant products will create a number of questions concerning the possible pathogenicity, toxicity, and changed nutritional values of such foodstuffs. This is a great challenge not only to the development of new approaches in nutritional toxicology but also to international cooperation in the field because genetic-modified organisms are not expected to recognize human-made trade barriers or borders. Therefore the initiative of OECD establishing an ad hoc group on safety and regulations in biotechnology is greatly acknowledged.

DNA, Recombinant↗
PubMed2004

Herpesviral-bacterial coinfection in periapical pathosis.

Two members of the herpesvirus family, human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV), seem to be important putative pathogens of human periodontitis and symptomatic periapical lesions, causing pathosis either by inducing immunosuppression with a subsequent risk of aggressive bacterial infections or by infecting of periodontal cells directly. This study aimed to relate periapical occurrence of HCMV, EBV, and herpes simplex virus active infections to clinical characteristics of periapical lesions and periapical bacterial flora. Microbial samples were collected from 34 periapical lesions in conjunction with periapical surgery. Part of the periapical specimen was frozen for virologic examination, and another part was transferred to anaerobic transport medium for bacteriologic examination. RNA was isolated by means of a guanidinium isothiocyanate-acid phenol procedure, and cDNA was produced using herpesvirus-specific primers and reverse-transcription polymerase chain reaction amplification. Bacteriologic examination was performed according to established anaerobic culture methods. Of the 34 periapical lesions studied, 20 showed both HCMV and EBV, seven showed only HCMV, one showed only EBV, and six showed neither HCMV nor EBV. Herpes simplex virus was detected in two lesions. Higher occurrence of herpesvirus was detected in large versus small periapical lesions (p < 0.001) and in symptomatic versus asymptomatic periapical lesions (p < 0.001). A total of 18 microbial groups and an average of 2.1 to 3.0 bacterial groups were isolated from various categories of periapical lesions. The important finding of this study was that most teeth with necrotic pulp and periapical lesions harbored herpesviruses in periapical granulomatous tissue. Herpesvirus species in cooperation with endodontopathic bacteria may play major roles in the etiopathogenesis of aggressive types of periapical pathosis in humans.

Adult↗
PubMed1994

An ABC-transporter from Streptomyces longisporoflavus confers resistance to the polyether-ionophore antibiotic tetronasin.

Streptomyces longisporoflavus produces the polyketide-polyether antibiotic, tetronasin, which acts as an ionophore and depolarizes the membrane of bacteria sensitive to the drug. A genomic library of S. longisporoflavus DNA was cloned in Streptomyces lividans and screened to identify tetronasin-resistance determinants. The inclusion of 0.2M NaCl in the growth medium with tetronasin markedly improved the sensitivity of the screen. Two different resistance determinants, designated tnrB (ptetR51) and tnrA (ptetR11) respectively, were identified. The determinant tnrB (ptetR51) but not tnrA (ptetR11), also conferred resistance to tetronasin when cloned into Streptomyces albus. The tnrB determinant was further localized, by subcloning, to a 2.8 kb KpnI fragment. DNA sequence analysis of this insert revealed one incomplete and two complete open reading frames (ORFs 1, 2 and 3). The deduced sequence of the gene product of ORF2 (TnrB2) revealed significant similarity to the ATP-binding domains of the ABC (ATP binding cassette) superfamily of transport-related proteins. The adjacent gene, ORF3, is translationally coupled to ORF2 and would encode a hydrophobic protein (TnrB3) with six transmembrane helices which probably constitutes the integral membrane component of the transporter. The mechanism of tetronasin resistance mediated by tnrB is probably an ATP-dependent efflux system.

Amino Acid Sequence↗
PubMed1999

Bile salts: natural detergents for the prevention of sexually transmitted diseases.

The development of new, safe, topical microbicides for intravaginal use for the prevention of sexually transmitted diseases is imperative. Previous studies have suggested that bile salts may inhibit human immunodeficiency virus infection; however, their activities against other sexually transmitted pathogens have not been reported. To further explore the potential role of bile salts in preventing sexually transmitted diseases, we examined the in vitro activities and cytotoxicities of select bile salts against Chlamydia trachomatis, herpes simplex virus (types 1 and 2), Neisseria gonorrhoeae, and human immunodeficiency virus in comparison to those of nonoxynol-9 and benzalkonium chloride using both primary cells and cell lines derived from the human female genital tract. We found that taurolithocholic acid 3-sulfate and a combination of glycocholic acid and taurolithocholic acid 3-sulfate showed excellent activity against all of the pathogens assayed. Moreover, taurolithocholic acid 3-sulfate alone or in combination was less cytotoxic than nonoxynol-9 and benzalkonium chloride. Thus, taurolithocholic acid 3-sulfate alone or in combination warrants further evaluation as a candidate topical microbicidal agent.

Bile Acids and Salts↗
PubMed1989

Successive steps in the process of immortalization identified by transfer of separate bovine papillomavirus genes into rat fibroblasts.

Transfer of neor and bovine papillomavirus type 1 (BPV1) DNA into rat embryo fibroblasts led to colony formation in G418-containing medium, with no detectable background in controls with neor DNA alone. More than 50% of the drug-resistant clones could be further propagated in culture. The genetic functions of BPV1 involved in colony formation and in long-term immortalization were investigated by both translation termination mutations in the full-length genome, which inactivate individual open reading frames, and constructs in which these open reading frames were separately expressed under control of long terminal repeat promoter enhancers. Expression of either open reading frame E2 or E5 was sufficient for formation of a drug-resistant colony, but long-term growth in culture required that of E6. No significant cooperative effect was observed upon cotransfection of BPV1 and ras oncogene DNAs. Expression of the early region of the human papillomavirus type 16 also led to immortalization of rat embryo fibroblast cells in the same assay, and, unlike what was previously reported in baby rat kidney cells, it required neither activation by a heterologous promoter, nor a cooperating ras oncogene.

Animals↗
PubMed1984

Bacteriological assistance for optimal antibiotic therapy of endocarditis.

The specific anatomical changes of the infected valvular tissue demand the best bactericidal antibiotic therapy of endocarditis. However, quantitative antibiotic sensitivity testing and determination of the bactericidal effectiveness is not sufficiently routinely practised. It is presented how appropriate bacteriological assistance to achieve the optimum antibiotic therapy for endocarditis leads to favourable clinical results. Establishment of reference laboratories for quantitative antibiotic sensitivity testing in every case of endocarditis is proposed. Active cooperation between these centres would provide excellent data for method and result comparison.

Anti-Bacterial Agents↗