Efficacy of trovafloxacin, a new quinolone antibiotic, in experimental staphylococcal endocarditis due to oxacillin-resistant strains

Therapeutic options for severe infections caused by strains of oxacillin-resistant Staphylococcus aureus (ORSA) and coagulase-negative staphylococci (ORSE) are very limited. With the increasing resistance of such strains to aminoglycosides, rifampin, and currently available quinolone agents, as well as the recent documentation of increasing resistance of ORSA to vancomycin (VANCO), new treatment alternatives are imperative. The in vivo efficacy of trovafloxacin (TROVA), a new quinolone agent with excellent antistaphylococcal activity in vitro, against experimental endocarditis (IE) due to beta-lactamase-producing ORSA and ORSE strains (ORSA and ORSE IE) was evaluated. TROVA (25 mg/kg of body weight intravenously [i.v.] twice daily [b.i.d]) was compared to VANCO (20 mg/kg i.v. b.i.d.) and two regimens of ampicillin-sulbactam (AMP-SUL; 200 mg/kg intramuscularly [i.m.] three times a day [t.i.d.] and 20 mg/kg i.m. b.i.d.), with all agents given for 3 or 6 days. AMP-SUL was included as a comparative treatment regimen because of its proven efficacy against experimental ORSA and ORSE IE. For both ORSA and ORSE IE, TROVA, AMP-SUL, and VANCO each reduced staphylococcal densities in vegetations compared to untreated controls (P < 0.01). For ORSA IE, TROVA was the most rapidly bactericidal agent--although not to a statistically significant degree--correlating with its superior bactericidal effect in vitro compared to those of VANCO and AMP-SUL.     

Oxacillin- and quinolone-resistant Staphylococcus aureus in Sao Paulo, Brazil: a multicenter molecular epidemiology study

OBJECTIVE: To investigate the possibility of interhospital spread of multiresistant Staphylococcus aureus in Sao Paulo, Brazil. DESIGN: We evaluated 13 nosocomial S aureus strains selected because of resistance to oxacillin and ciprofloxacin. SETTING: The strains were collected between March 1991 and September 1991 from four different hospitals in Sao Paulo. Two were teaching hospitals, and two were private hospitals. PATIENTS: Each strain was isolated from a different patient. All patients were hospitalized when the strains were isolated. INTERVENTIONS: The strains were typed by restriction endonuclease analyses of plasmid DNA (REAP) using EcoRI, HindIII, RsaI, and AluI and by extended antibiogram profile (34 drugs). RESULTS: All strains had identical plasmid and antibiogram profile. They demonstrated the same plasmid pattern as previously described in one of the hospitals studied. CONCLUSIONS: Our results suggest the dissemination of a unique oxacillin- and quinolone-resistant strain of S aureus in several hospitals of Sao Paulo, Brazil.     

Levofloxacin versus ciprofloxacin, flucloxacillin, or vancomycin for treatment of experimental endocarditis due to methicillin-susceptible or -resistant Staphylococcus aureus

Levofloxacin is the L isomer of ofloxacin, a racemic mixture in which the L stereochemical form carries the antimicrobial activity. Levofloxacin is more active than former quinolones against gram-positive bacteria, making it potentially useful against such pathogens. In this study, levofloxacin was compared to ciprofloxacin, flucloxacillin, and vancomycin for the treatment of experimental endocarditis due to two methicillin-susceptible Staphylococcus aureus (MSSA) and two methicillin-resistant S. aureus (MRSA) isolates. The four test organisms were susceptible to ciprofloxacin, the levofloxacin MICs for the organisms were low (0.12 to 0.25 mg/liter), and the organisms were killed in vitro by drug concentrations simulating both the peak and trough levels achieved in human serum (5 and 0.5 mg/liter, respectively) during levofloxacin therapy. Rats with aortic endocarditis were treated for 3 days. Antibiotics were injected with a programmable pump to simulate the kinetics of either levofloxacin (350 mg orally once a day), ciprofloxacin (750 mg orally twice a day), flucloxacillin (2 g intravenously four times a day), or vancomycin (1 g intravenously twice a day). Levofloxacin tended to be superior to ciprofloxacin in therapeutic experiments (P = 0.08). More importantly, levofloxacin did not select for resistance in the animals, in contrast to ciprofloxacin. The lower propensity of levofloxacin than ciprofloxacin to select for quinolone resistance was also clearly demonstrated in vitro. Finally, the effectiveness of this simulation of oral levofloxacin therapy was at least equivalent to that of standard treatment for MSSA or MRSA endocarditis with either flucloxacillin or vancomycin. This is noteworthy, because oral antibiotics are not expected to succeed in the treatment of severe staphylococcal infections. These good results obtained with animals suggest that levofloxacin might deserve consideration for further study in the treatment of infections due to ciprofloxacin-susceptible staphylococci in humans.     

Bacteriological activity of trovafloxacin, a new quinolone, against respiratory tract pathogens

BACKGROUND: Corpus callosum (CC) morphology has recently been investigated in schizophrenia using refined imaging and analytic techniques; however, methodological problems and small sample sizes have led to inconsistent findings. METHODS: This study used a large sample of male schizophrenics (n = 79) and male controls (n = 65) to investigate size and shape of the CC on midsagittal magnetic resonance images. Size was determined by tracing the area of the CC, and shape was determined using a landmark-based analysis. In addition, the relationship between CC morphology and phenomenologic variables such as age of onset, length of illness, exposure to medications, and symptom severity was explored. RESULTS: After controlling for age, height, and parental socioeconomic status, there was a main effect of diagnosis on CC size (F = 5.05, df = 1,139, p < .03), with patients' CCs being significantly smaller. No difference was found between patients and controls in CC shape (F = 1.07, df = 18,125, p > .38) or orientation (F = 0.79, df = 18,125, p > .70), using a landmark-based technique. Finally, there was a significant inverse correlation between size of CC and severity of negative symptoms. CONCLUSIONS: These findings support previous studies that have found a decrease in size of the CC in patients with schizophrenia. Moreover, the decrement in volume is generalized, not regional, and is related to the severity of negative symptoms.     

In vivo efficacy of silver-coated (Silzone) infection-resistant polyester fabric against a biofilm-producing bacteria, Staphylococcus epidermidis

OBJECTIVE: To study the characteristics of birthweight and gestational age of third trimester fetal deaths which occurred before the onset of labour. DESIGN: Review of computerised confidential perinatal mortality records. Data originated from the 1992 Trent Region Perinatal Mortality Survey. SAMPLE: One hundred and forty-nine antepartum stillbirths of at least 24 weeks of gestation confirmed by early ultrasound scan. Congenital abnormalities and multiple pregnancies were excluded. MAIN OUTCOME MEASURES: Reported causes of stillbirth; weight-for-gestational age centiles based on a standard derived from normal pregnancies; pregnancy characteristics compared with the local maternity population. RESULTS: Of 149 stillbirths, 83 (56%) were preterm and 66 were at term, and the majority (126; 85%) occurred from 31 weeks. Most of the deaths (97; 65%) were reported as 'unexplained' even though post-mortems had been carried out in 60% of all cases. Using a gestational age-specific fetal weight standard derived from normal, term live births, 41% of all cases of stillborn infants were small-for-gestational age (< 10th centile; OR 6.2; 95% CI 3.3-11.5); 39% of which had been classified as unexplained were small for gestational age (OR 5.6; 2.6-12.0). This excess of small stillbirths was most pronounced between 31 and 33 weeks, where the weights of 63% of all stillbirths and 72% of unexplained fetal deaths were < 10th centile. Overall, a higher proportion of preterm (< 37 weeks) than term stillbirths were small for gestational age: 53% vs 26% (OR 3.3; 1.6-6.5). However, at term there were also more subtle differences in weight deficit, with more fetuses with a weight between the 10th and 50th centiles than between 50th and 90th (36 vs 11; OR 3.3; 1.4-7.8). Mothers of pregnancies ending in stillbirth were similar in age, size, parity and ethnic group to mothers of live born babies, but were more likely to be smokers (37 vs 27%, OR 1.6; 1.2-2.3). CONCLUSIONS: Many stillborn babies are small for gestational age. In the absence of significant differences in physiological pregnancy characteristics, this is unlikely to be a constitutional smallness, but represents a preponderance of intrauterine growth restriction. For a full appreciation of the strength of this association, appropriate weight standards and classifications need to be applied in perinatal mortality surveys. Many antepartum stillbirths which are currently designated as unexplained may be avoidable if slow fetal growth could be recognised as a warning sign.     

Antibacterial activity of gatifloxacin (AM-1155, CG5501, BMS-206584), a newly developed fluoroquinolone, against sequentially acquired quinolone-resistant mutants and the norA transformant of Staphylococcus aureus

Alternate mutations in the grlA and gyrA genes were observed through the first- to fourth-step mutants which were obtained from four Staphylococcus aureus strains by sequential selection with several fluoroquinolones. The increases in the MICs of gatifloxacin accompanying those mutational steps suggest that primary targets of gatifloxacin in the wild type and the first-, second-, and third-step mutants are wild-type topoisomerase IV (topo IV), wild-type DNA gyrase, singly mutated topo IV, and singly mutated DNA gyrase, respectively. Gatifloxacin had activity equal to that of tosufloxacin and activity more potent than those of norfloxacin, ofloxacin, ciprofloxacin, and sparfloxacin against the second-step mutants (grlA gyrA; gatifloxacin MIC range, 1.56 to 3.13 microg/ml) and had the most potent activity against the third-step mutants (grlA gyrA grlA; gatifloxacin MIC range, 1.56 to 6.25 microg/ml), suggesting that gatifloxacin possesses the most potent inhibitory activity against singly mutated topo IV and singly mutated DNA gyrase among the quinolones tested. Moreover, gatifloxacin selected resistant mutants from wild-type and the second-step mutants at a low frequency. Gatifloxacin possessed potent activity (MIC, 0.39 microg/ml) against the NorA-overproducing strain S. aureus NY12, the norA transformant, which was slightly lower than that against the parent strain SA113. The increases in the MICs of the quinolones tested against NY12 were negatively correlated with the hydrophobicity of the quinolones (correlation coefficient, -0.93; P < 0.01). Therefore, this slight decrease in the activity of gatifloxacin is attributable to its high hydrophobicity. Those properties of gatifloxacin likely explain its good activity against quinolone-resistant clinical isolates of S. aureus harboring the grlA, gyrA, and/or norA mutations.     

In vitro and in vivo antibacterial activities of T-3761, a new quinolone derivative

T-3761, a new quinolone derivative, showed broad and potent antibacterial activity. Its MICs for 90% of the strains tested were 0.20 to 100 micrograms/ml against gram-positive bacteria, including members of the genera Staphylococcus, Streptococcus, and Enterococcus; 0.025 to 3.13 micrograms/ml against gram-negative bacteria, including members of the family Enterobacteriaceae and the genus Haemophilus; 0.05 to 50 micrograms/ml against glucose nonfermenters, including members of the genera Pseudomonas, Xanthomonas, Acinetobacter, Alcaligenes, and Moraxella; 0.025 micrograms/ml against Legionella spp.; and 6.25 to 25 micrograms/ml against anaerobes, including Bacteroides fragilis, Clostridium difficile, and Peptostreptococcus spp. The in vitro activity of T-3761 against these clinical isolates was comparable to or 2- to 32-fold greater than those of ofloxacin and norfloxacin and 2- to 16-fold less and 1- to 8-fold greater than those of ciprofloxacin and tosulfoxacin, respectively. When administered orally, T-3761 showed good efficacy in mice against systemic, pulmonary, and urinary tract infections with gram-positive and gram-negative bacteria, including quinolone-resistant Serratia marcescens and Pseudomonas aeruginosa. The in vivo activity of T-3761 was comparable to or greater than those of ofloxacin, ciprofloxacin, norfloxacin, and tosufloxacin against most infection models in mice. The activities of T-3761 were lower than those of tosufloxacin against gram-positive bacterial systemic and pulmonary infections in mice but not against infections with methicillin-resistant Staphylococcus aureus. The activities of T-3761 against systemic quinolone-resistant Serratia marcescens and Pseudomonas aeruginosa infections in mice were 2- to 14-fold greater than those of the reference agents.     

Impact of the high-affinity proline permease gene (putP) on the virulence of Staphylococcus aureus in experimental endocarditis

Staphylococcus aureus causes a wide variety of invasive human infections. However, delineation of the genes which are essential for the in vivo survival of this pathogen has not been accomplished to date. Using signature tag mutagenesis techniques and large mutant pool screens, previous investigators identified several major gene classes as candidate essential gene loci for in vivo survival; these include genes for amino acid transporters, oligopeptide transporters, and lantibiotic synthesis (W. R. Schwan, S. N. Coulter, E. Y. W. Ng, M. H. Langhorne, H. D. Ritchie, L. L. Brody, S. Westbrock-Wadman, A. S. Bayer, K. R. Folger, and C. K. Stover, Infect. Immun. 66:567-572, 1998). In this study, we directly compared the virulence of four such isogenic signature tag mutants with that of the parental strain (RN6390) by using a prototypical model of invasive S. aureus infection, experimental endocarditis (IE). The oligonucleotide signature tag (OST) mutant with insertional inactivation of the gene (putP) which encodes the high-affinity transporter for proline uptake exhibited significantly reduced virulence in the IE model across three challenge inocula (10(4) to 10(6) CFU) in terms of achievable intravegetation densities (P, <0.05). The negative impact of putP inactivation on in vivo survival in the IE model was confirmed by simultaneous challenge with the original putP mutant and the parental strain as well as by challenge with a putP mutant in which this genetic inactivation was transduced into a distinct parental strain (S6C). In contrast, inactivation of loci encoding an oligopeptide transporter, a purine repressor, and lantibiotic biosynthesis had no substantial impact on the capacity of OST mutants to survive within IE vegetations. Thus, genes encoding the uptake of essential amino acids may well represent novel targets for new drug development. These data also confirm the utility of the OST technique as an important screening methodology for identifying candidate genes as requisite loci for the in vivo survival of S. aureus.     

Efflux pump-mediated quinolone resistance in Staphylococcus aureus strains wild type for gyrA, gyrB, grlA, and norA

Fluoroquinolone efflux was studied in 47 Staphylococcus aureus clinical strains with MICs of ciprofloxacin (CFX) of < or = 2 micrograms/ml. Forty-three strains were wild type for gyrA, gyrB, and grlA quinolone resistance-determining regions and for norA and its promoter region. Forty of these strains (MICs of CFX, 0.1 to 0.2 microgram/ml) did not show efflux of fluoroquinolones. Three strains (MICs of CFX, 1 to 2 micrograms/ml) showed efflux. These results suggest that efflux can appear in S. aureus clinical strains in the absence of mutations in norA and its promoter.     

Reconsideration of the role of fibronectin binding in endocarditis caused by Staphylococcus aureus

The adherence characteristics in vivo and virulence of two isogenic strains of Staphylococcus aureus differing in fibronectin binding were compared in a rat model of catheter-induced infective endocarditis. No differences were found between the two strains. The results strongly point to the multifactorial nature of bacterial adherence to damaged heart valves and suggest that other binding functions can compensate for the lack of fibronectin binding in S. aureus.     

Effects of mutations in GrlA of topoisomerase IV from Staphylococcus aureus on quinolone and coumarin activity

The grlA genes of Staphylococcus aureus ISP794 (wild type), MT5224c4 (grlA [Phe-80]), MT5224c2 (grlA [Pro-116]), and MT111 (grlA [Glu-116]) were cloned in pSK950, a shuttle vector, and introduced into S. aureus strains derived from strain RN4220. The mutations at position 116 of GrlA (Ala-->Pro or Glu) caused an increase in the level of fluoroquinolone resistance and a decrease in the level of coumarin susceptibility, whereas the mutation at position 80 (Ser-->Phe) caused only an increase in the level of fluoroquinolone resistance. In multicopy alleles, both types of mutations were codominant for fluoroquinolone resistance, and mutations at position 116 were also codominant for coumarin resistance.     

Effects of DU-6859a, a new quinolone antimicrobial, on theophylline metabolism in in vitro and in vivo studies

In vitro and in vivo studies were conducted to investigate the drug interaction between a new quinolone antimicrobial, DU-6859a, and theophylline (TP). The effect of DU-6859a on TP metabolism was evaluated in vitro by measuring the rate of TP metabolite formation by using human liver microsomes. DU-6859a inhibited the metabolism of TP, especially the formation of 1-methylxanthine, in vitro, but to a lesser extent than other drugs that are known to interact with TP. TP was administered alone (200 mg twice a day [b.i.d.] for 9 days) or in combination with DU-6859a (50 or 100 mg b.i.d. for 5 days) to six healthy subjects. DU-6859a administered at a dose of 50 mg resulted in no changes in serum TP concentrations, and slight increases in serum TP concentrations were observed at a dose of 100 mg. Moreover, the administration of 100 mg of DU-6859a resulted in decreases in all urinary TP metabolites, with significant differences. It appears that although DU-6859a has a weak inhibitory effect on TP metabolism in vitro, its concomitant use with TP at clinical dosage levels does not cause any adverse effects, showing only a slight increase in blood TP concentrations and a decrease in urinary metabolites.     

A comparative study on the efficacy of the new quinolone alatrofloxacin in the treatment of experimental legionellosis in guinea pigs

The in vivo efficacy of trovafloxacin, intraperitoneally administered as alatrofloxacin (CP-116,517), was assessed and compared with that of erythromycin, alone or in combination with rifampicin, in a model of Legionella pneumophila pneumonia in guinea pigs. Trovafloxacin (5 mg/kg administered as alatrofloxacin once daily for 7 days) gave a survival rate of 100% in infected animals. Clearance of bacteria and of bacteria-induced lesions from lungs was achieved by day 6 post-inoculation. The lungs of trovafloxacin-treated animals remained free of bacteria at day 28 post-challenge. Trovafloxacin proved as effective as erythromycin administered intraperitoneally, but was superior to erythromycin alone. or in combination with rifampicin, when given orally.     

The genome of Staphylococcus aureus: a review

The genome of Staphylococcus aureus consists of a single circular chromosome (2.7-2.8 mbp) plus an assortment of extrachromosomal accessory genetic elements: conjugative and nonconjugative plasmids, mobile elements (IS, Tn, Hi), prophages and other variable elements. Plasmids (1-60 kbp) are classified into 4 classes and there are 15 known incompatibility groups. Mobile elements of the genome (0.8-18 kbp) appear in the chromosome or in plasmids of classes II and III. Prophages (45-60 kbp) are integrated in the bacterial chromosome, and they are UV- or mitomycin-inducible. Temperate bacteriophages of S. aureus are members of the Siphoviridae and the serological groups A, B and F occur most frequently. In the paper presented, the characteristics of chromosome, plasmids, transposons and other genetic elements of S. aureus genome are given and an alphabetical list of known genes of this species is included.     

Autoinducer of virulence as a target for vaccine and therapy against Staphylococcus aureus

Staphylococcus aureus causes pathologies ranging from minor skin infections to life-threatening diseases. Pathogenic effects are largely due to production of bacterial toxin, which is regulated by an RNA molecule, RNAIII. The S. aureus protein called RAP (RNAIII activating protein) activates RNAIII, and a peptide called RIP (RNAIII inhibiting peptide), produced by a nonpathogenic bacteria, inhibits RNAIII. Mice vaccinated with RAP or treated with purified or synthetic RIP were protected from S. aureus pathology. Thus, these two molecules may provide useful approaches for the prevention and treatment of diseases caused by S. aureus.     

Structural and dynamical characterization of a biologically active unfolded fibronectin-binding protein from Staphylococcus aureus

A 130-residue fragment (D1-D4) taken from a fibronectin-binding protein of Staphylococcus aureus, which contains four fibronectin-binding repeats and is unfolded but biologically active at neutral pH, has been studied extensively by NMR spectroscopy. Using heteronuclear multidimensional techniques, the conformational properties of D1-D4 have been defined at both a global and a local level. Diffusion studies give an average effective radius of 26.2 +/- 0.1 A, approximately 75% larger than that expected for a globular protein of this size. Analysis of chemical shift, 3JHNalpha coupling constant, and NOE data show that the experimental parameters agree well overall with values measured in short model peptides and with predictions from a statistical model for a random coil. Sequences where specific features give deviations from these predictions for a random coil have however been identified. These arise from clustering of hydrophobic side chains and electrostatic interactions between charged groups. 15N relaxation studies demonstrate that local fluctuations of the chain are the dominant motional process that gives rise to relaxation of the 15N nuclei, with a persistence length of approximately 7-10 residues for the segmental motion. The consequences of the structural and dynamical properties of this unfolded protein for its biological role of binding to fibronectin have been considered. It is found that the regions of the sequence involved in binding have a high propensity for populating extended conformations, a feature that would allow a number of both charged and hydrophobic groups to be presented to fibronectin for highly specific binding.     

Substrate specificity of Staphylococcus hyicus lipase and Staphylococcus aureus lipase as studied by in vivo chimeragenesis

Staphylococcus hyicus lipase (SHL) and Staphylococcus aureus lipase (SAL) are highly homologous enzymes, yet they show remarkable differences in their biochemical characteristics. SHL displays a high phospholipase activity, hydrolyses neutral lipids, and has no chain length preference, whereas SAL only degrades short-chain fatty acid esters. To identify the regions in the primary sequence of SHL responsible for phospholipase activity and chain length selectivity, a set of histidine-tagged SAL/SHL chimeras was generated by in vivo recombination in Escherichia coli. Several classes of chimeric enzymes were identified on the basis of restriction site analysis. All chimeras were well-expressed as active enzymes. They were characterized for their specific activities on both phospholipids and p-nitrophenyl esters of various chain lengths. Phospholipase activity appeared to be determined by three regions, all located in the C-terminal domain of SHL. Testing of the enzymatic activity of the chimeras toward p-nitrophenyl esters showed that chain length selectivity is defined by elements within the region of residues 180-253. Moreover, also residues along the stretch 275-358 contribute to the binding of acyl chains. Interestingly, several chimeras were even more active than the parent enzymes on long-chain p-nitrophenyl esters.     

Correlation of in vitro resistance of Staphylococcus aureus to tetracycline, doxycycline, and minocycline with in vivo use

A study was carried out to investigate the errors involved in obtaining volumes by means of ultrasound echograms and a small computer. The work was done on live pigs' kidneys (130-200 cm3). The errors include those associated with the scanner itself, those invloved in the interpretation of the contour boundaries, and those relating to the algorithms used to determine the volumes from the contours. An average deviation of 25.4 cm3 from actual volumes was found, while 58% of the measurements were within +/-10%. Computer programs allowing for the display of contours and intercepts of corresponding orthogonal scan planes were used to reanalyze the data resulting in an average deviation of 14.7 cm3 with 78% of the data resulting inan average deviation of 14.7 cm3 with 78% of the measurements with "/-10%.