Observational study to estimate the proportion of surgical site infection following excision of ulcerated skin tumours (OASIS study)

BACKGROUND

Ulceration is a recognized risk factor for surgical site infection (SSI); however, the proportion of patients developing SSI after excision of an ulcerated skin cancer is unknown.

AIM

To determine the proportion of participants with SSI after surgical excision of an ulcerated skin cancer. A secondary aim was to assess feasibility outcomes to inform the design of a randomized controlled trial to investigate the benefits and harms of perioperative antibiotics following excision of ulcerated tumours.

METHODS

This was a multicentre, prospective, observational study of patients undergoing excision of an ulcerated skin cancer between March 2019 and March 2020. Prior to surgical excision, surface swabs of the ulcerated tumours of participants recruited from one centre were undertaken to determine organism growth. At 4 weeks after surgery, all participants were e-mailed or posted the Wound Healing Questionnaire (WHQ) to determine whether they had developed SSI.

RESULTS

In total, 148 participants were recruited 105 (70.9%) males; mean ± SD age 77.1 ± 12.3 years. Primary outcome data were available for 116 (78.4%) participants, of whom 35 (30.2%) were identified as having an SSI using the WHQ with a cutoff score of 8, and 47 (40.5%) were identified with a cutoff score of 6. Using the modified WHQ in participants with wounds left to heal by secondary intention, 33 (28.4%) and 43 (37.1%) were identified to have SSI respectively.

CONCLUSION

This prospective evaluation of SSI identified with the WHQ following excision of ulcerated skin cancers demonstrated a high proportion with SSI. The WHQ was acceptable to patients; however, further evaluation is required to ensure validity in assessing skin wounds.

Occurrence and chemical characteristics of microplastic paint flakes in the North Atlantic Ocean

Non-fibrous microplastics sampled by the Continuous Plankton Recorder (CPR) Survey throughout the North Atlantic Ocean during 2018 have been recorded and a selection (n = 17, or 16.7%) physically and chemically characterised. The average abundance of non-fibrous particles captured by the plankton silks and detectable by microscopy was estimated to be around 0.01 m^-3, with the highest concentrations evident in shelf seas of northwest Europe. Amongst the samples analysed, median size was 180 μm and, based on visible properties (e.g., brittleness, layering) and infra-red spectra, all but one were identified as flakes of paint. Semi-quantitative analysis by energy-dispersive X-ray fluorescence spectrometry with a collimated beam revealed that six flakes from European shelf seas were Cu-based antifouling formulations (without evidence of organo-Sn compounds), and five with a broader geographical distribution were Pb-based formulations of likely marine origin. Other elements regularly detected included Cr, Fe, Ti and Zn that were present in pigments or as contaminants from the underlying substrate. After fibres, paint flakes appear to be the most abundant type of microplastic in the oceans that, because of the abundance and mobility of metallic additives, deserve closer scientific attention.

Can a key boreal Calanus copepod species now complete its life-cycle in the Arctic? Evidence and implications for Arctic food-webs

The changing Arctic environment is affecting zooplankton that support its abundant wildlife. We examined how these changes are influencing a key zooplankton species, Calanus finmarchicus, principally found in the North Atlantic but expatriated to the Arctic. Close to the ice-edge in the Fram Strait, we identified areas that, since the 1980s, are increasingly favourable to C. finmarchicus. Field-sampling revealed part of the population there to be capable of amassing enough reserves to overwinter. Early developmental stages were also present in early summer, suggesting successful local recruitment. This extension to suitable C. finmarchicus habitat is most likely facilitated by the long-term retreat of the ice-edge, allowing phytoplankton to bloom earlier and for longer and through higher temperatures increasing copepod developmental rates. The increased capacity for this species to complete its life-cycle and prosper in the Fram Strait can change community structure, with large consequences to regional food-webs.

Rapid detection and differentiation of mobile colistin resistance (mcr-1 to mcr-10) genes by real-time PCR and melt-curve analysis

BACKGROUND

The emergence of multi-drug-resistant (MDR) micro-organisms prompted new interest in older antibiotics, such as colistin, that had been abandoned previously due to limited efficacy or high toxicity. Over the years, several chromosomal-encoded colistin resistance mechanisms have been described; more recently, 10 plasmid-mediated mobile colistin resistance (mcr) genes have been identified. Spread of these genes among MDR Gram-negative bacteria is a matter of serious concern; therefore, reliable and timely mcr detection is paramount.

AIM

To design and validate a multiplex real-time polymerase chain reaction (PCR) assay for detection and differentiation of mcr genes.

METHODS

All available mcr alleles were downloaded from the National Center for Biotechnology Information Reference Gene Catalogue, aligned with Clustal Omega and primers designed using Primer-BLAST. Real-time PCR monoplexes were optimized and validated using a panel of 120 characterized Gram-negative strains carrying a wide range of resistance genes, often in combination. Melt-curve analysis was used to confirm positive results.

FINDINGS

In-silico analysis enabled the design of a 'screening' assay for detection of mcr-1/2/6, mcr-3, mcr-4, mcr-5, mcr-7, mcr-8 and mcr-9/10, paired with an internal control assay to discount inhibition. A 'supplementary' assay was subsequently designed to differentiate mcr-1, mcr-2, mcr-6, mcr-9 and mcr-10. Expected results were obtained for all strains (100% sensitivity and specificity). Melt-curve analysis showed consistent melting temperature results. Inhibition was not observed.

CONCLUSIONS

The assay is rapid and easy to perform, enabling unequivocal mcr detection and differentiation even when more than one variant is present. Adoption by clinical and veterinary microbiology laboratories would aid the surveillance of mcr genes amongst Gram-negative bacteria.

Impact of rapid microbial identification on clinical outcomes in bloodstream infection: the RAPIDO randomized trial

OBJECTIVES

Bloodstream infection has a high mortality rate. It is not clear whether laboratory-based rapid identification of the organisms involved would improve outcome.

METHODS

The RAPIDO trial was an open parallel-group multicentre randomized controlled trial. We tested all positive blood cultures from hospitalized adults by conventional methods of microbial identification and those from patients randomized (1:1) to rapid diagnosis in addition to matrix-assisted desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) performed directly on positive blood cultures. The only primary outcome was 28-day mortality. Clinical advice on patient management was provided to members of both groups by infection specialists.

RESULTS

First positive blood culture samples from 8628 patients were randomized, 4312 into rapid diagnosis and 4136 into conventional diagnosis. After prespecified postrandomization exclusions, 2740 in the rapid diagnosis arm and 2810 in the conventional arm were included in the mortality analysis. There was no significant difference in 28-day survival (81.5% 2233/2740 rapid vs. 82.3% 2313/2810 conventional; hazard ratio 1.05, 95% confidence interval 0.93-1.19, p 0.42). Microbial identification was quicker in the rapid diagnosis group (median (interquartile range) 38.5 (26.7-50.3) hours after blood sampling vs. 50.3 (47.1-72.9) hours after blood sampling, p < 0.01), but times to effective antimicrobial therapy were no shorter (respectively median (interquartile range) 24 (2-78) hours vs. 13 (2-69) hours). There were no significant differences in 7-day mortality or total antibiotic consumption; times to resolution of fever, discharge from hospital or de-escalation of broad-spectrum therapy or 28-day Clostridioides difficile incidence.

CONCLUSIONS

Rapid identification of bloodstream pathogens by MALDI-TOF MS in this trial did not reduce patient mortality despite delivering laboratory data to clinicians sooner.

The rise in ocean plastics evidenced from a 60-year time series

Plastic production has increased exponentially since its use became widespread in the 1950s. This has led to increased concern as plastics have become prevalent in the oceanic environment, and evidence of their impacts on marine organisms and human health has been highlighted. Despite their prevalence, very few long-term (>40 years) records of the distribution and temporal trends of plastics in the world's oceans exist. Here we present a new time series, from 1957 to 2016 and covering over 6.5 million nautical miles, based on records of when plastics have become entangled on a towed marine sampler. This consistent time series provides some of the earliest records of plastic entanglement, and is the first to confirm a significant increase in open ocean plastics in recent decades.

Genetic & virulence profiling of ESBL-positive E. coli from nosocomial & veterinary sources

CTX-M genes are the most prevalent ESBL globally, infiltrating nosocomial, community and environmental settings. Wild and domesticated animals may act as effective vectors for the dissemination of CTX-producing Enterobacteriaceae. This study aimed to contextualise blaCTX-M-14-positive, cephalosporin-resistant Enterobacteriaceae human infections and compared resistance and pathogenicity markers with veterinary isolates. Epidemiologically related human (n=18) and veterinary (n=4) blaCTX-M-14-positive E. coli were fully characterised. All were typed by XbaI pulsed field gel electrophoresis and ST. Chromosomal/plasmidic locations of blaCTX-M-14 were deduced by S1-nuclease digestion, and association with ISEcp1 was investigated by sequencing. Conjugation experiments assessed transmissibility of plasmids carrying blaCTX-M-14. Presence of virulence determinants was screened by PCR assay and pathogenicity potential was determined by in vitro Galleria mellonella infection models. 84% of clinical E. coli originated from community patients. blaCTX-M-14 was found ubiquitously downstream of ISEcp1 upon conjugative plasmids (25-150 kb). blaCTX-M-14 was also found upon the chromosome of eight E. coli isolates. CTX-M-14-producing E. coli were found at multiple hospital sites. Clonal commonality between patient, hospitals and livestock microbial populations was found. In vivo model survival rates from clinical isolates (30%) and veterinary isolates (0%) were significantly different (p<0.05). Co-transfer of blaCTX-M-14 and virulence determinants was demonstrated. There is evidence of clonal spread of blaCTX-M-14-positive E. coli involving community patients and farm livestock. blaCTX-M-14 positive human clinical isolates carry a lower intrinsic pathogenic potential than veterinary E. coli highlighting the need for greater veterinary practices in preventing dissemination of MDR E. coli among livestock.

Analytic laboratory performance of a point of care urine culture kit for diagnosis and antibiotic susceptibility testing

Currently available point-of-care (POC) diagnostic tests for managing urinary tract infections (UTIs) in general practice are limited by poor performance characteristics, and laboratory culture generally provides results only after a few days. This laboratory evaluation compared the analytic performance of the POC UK Flexicult(™) (Statens Serum Institut) (SSI) urinary kit for quantification, identification and antibiotic susceptibility testing and routine UK National Health Service (NHS) urine processing to an advanced urine culture method. Two hundred urine samples routinely submitted to the Public Health Wales Microbiology Laboratory were divided and: (1) analysed by routine NHS microbiological tests as per local laboratory standard operating procedures, (2) inoculated onto the UK Flexicult(™) SSI urinary kit and (3) spiral plated onto Colorex Orientation UTI medium (E&O Laboratories Ltd). The results were evaluated between the NHS and Flexicult(™ )methods, and discordant results were compared to the spiral plating method. The UK Flexicult(™) SSI urinary kit was compared to routine NHS culture for identification of a pure or predominant uropathogen at ≥ 10(5) cfu/mL, with a positive discordancy rate of 13.5% and a negative discordancy rate of 3%. The sensitivity and specificity were 86.7% [95% confidence interval (CI) 73.8-93.7] and 82.6% (95% CI 75.8-87.7), respectively. The UK Flexicult(™) SSI urinary kit was comparable to routine NHS urine processing in identifying microbiologically positive UTIs in this laboratory evaluation. However, the number of false-positive samples could lead to over-prescribing of antibiotics in clinical practice. The Flexicult(™) SSI kit could be useful as a POC test for UTIs in primary care but further pragmatic evaluations are necessary.

Detection and characterization of pCT-like plasmid vectors for blaCTX-M-14 in Escherichia coli isolates from humans, turkeys and cattle in England and Wales

OBJECTIVES

To detect and characterize Escherichia coli strains and pCT-like plasmids implicated in the dissemination of the CTX-M-14 gene in animals and humans, in England and Wales.

METHODS

UK CTX-M-14-producing E. coli (n=70) from cattle (n=33), turkeys (n=9), sheep (n=2) and humans (n=26) were screened using multiplex PCR for the detection of a previously characterized plasmid, pCT. Isolates found to be carrying two or more pCT genetic markers were further analysed using PFGE. Their antimicrobial-resistance genes and virulence genes were also determined. These plasmids were transferred to Salmonella enterica serotype Typhimurium 26R and further examined for incompatibility type, genetic environment of the bla(CTX-M-14) gene, size, restriction fragment length polymorphism (RFLP) and nikB sequence.

RESULTS

The 25 E. coli isolates carrying pCT genetic markers generated 19 different PFGE profiles, and 23 isolates had different virulence and antimicrobial-resistance gene patterns. One isolate from cattle was a verotoxigenic E. coli ('VTEC'); the rest were commensal or extra-intestinal pathogenic E. coli. pCT-like plasmids with similar molecular characteristics (size, replicon type, RFLP pattern, pCT markers and genetic environment of the bla(CTX-M-14) gene) were detected in 21/25 of the field isolates, which comprised those from cattle (n=9), turkeys (n=8) and humans (n=4). All pCT-like plasmids were conjugative, and most were IncK (n=21) and had the same local genetic environment flanking the bla(CTX-M-14) gene (n=23). RFLP analysis demonstrated ≥ 75% similarity among most plasmids (n=22).

CONCLUSIONS

pCT-like plasmids were common vectors for horizontal dissemination of 30% of the bla(CTX-M-14) genes to different E. coli isolates from humans, cattle and turkeys.

Expression of tcaA and mprF and glycopeptide resistance in clinical glycopeptide-intermediate Staphylococcus aureus (GISA) and heteroGISA strains

Two genes recently associated with glycopeptide intermediate resistance in Staphylococcus aureus (GISA) are mprF and tcaA, with inactivation causing shifts in vancomycin resistance. This study reveals that expression levels of both genes are similar in groups of clinical GISA, heteroGISA and glycopeptide susceptible strains, suggesting no association with clinical isolates.

Ventriculitis due to a hetero strain of vancomycin intermediate Staphylococcus aureus (hVISA): successful treatment with linezolid in combination with intraventricular vancomycin

A 67-year male presented with relapse 14 days after treatment with vancomycin for a MRSA ventriculitis. CSF samples taken at the time of relapse grew MRSA with a MIC for vancomycin of 4 mg/L by E-test and therapy with linezolid (600 mg bd) and intraventricular vancomycin (20 mg od) was initiated. Using the macrodilution E-test, the isolate was found to have sub-populations with a MIC for vancomycin of 8 mg/L and teicoplanin of 12 mg/L and a population analysis profile almost identical to the hVISA strain MU3, indicative of a hVISA strain. Concentrations of vancomycin in the CSF over the period of therapy ranged from 25.6-192.5 mg/L after intraventricular administration and those of linezolid ranged from 3.4-6.7 mg/L after intravenous administration, exceeding the MICs for this isolate. The patient made a successful recovery, with no further episodes of ventriculitis at 1-year follow-up. We report the first case of ventriculitis due to hVISA. It was successfully treated with intrathecal vancomycin and intravenous linezolid. We also believe this to be the first documented case of clinical infection due to hVISA in South Africa.

Development of a novel assay method for colistin sulphomethate

Increased use of colistin therapy for infections caused by Pseudomonas aeruginosa has indicated a need for a more robust microbiological assay technique. This report describes a quick and simple microbiological assay for quantifying levels of colistin sulphomethate in serum and urine samples from cystic fibrosis patients. The technique uses no specialised or costly equipment and is suitable for use in all routine diagnostic microbiology laboratories.

Potential of capillary electrophoresis for identification of Australian triticale varieties

Ethanol soluble proteins were extracted from 5 different triticale varieties grown at 2 different sites in South Australia, and from single samples of wheat and rye. Separation of these proteins using capillary electrophoresis (CE) showed different patterns for different varieties but similar patterns for the same varieties grown at the 2 sites. The main differences between electropherograms for wheat and triticale were attributed to the presence of rye secalins, higher levels of α-gliadins, and lower levels of β-gliadins in those from the latter. These results indicate the potential of CE of ethanol-soluble proteins for identification of triticale varieties.

Cefuroxime resistance in non-beta-lactamase Haemophilus influenzae is linked to mutations in ftsI

The penicillin binding protein (PBP) genes dacA, dacB and ftsI from 14 cefuroxime-resistant (CXM(R)) isolates and three clinical isolates with low CXM MIC for non-beta-lactamase-producing Haemophilus influenzae type b were molecularly characterized. One strain, 5788, was used to transform H. influenzae Rd to CXM(R) for direct comparison of the pbps in the same genetic background. No obvious mutations in the dacA and dacB gene products could be associated with CXM(R). One amino acid substitution in the ftsI gene product in particular, S357N, could give rise to CXM(R). Sequence analysis from the CXM(R) transformants also implicated FtsI; in this case, the substitutions were V511A and R517H. To verify S357N substitution, the protein sequence of H. influenzae FtsI was threaded through the S. pneumoniae PBP 2X structure giving an average root mean square deviation of the alpha-carbon chains of 0.5 A. The S357N substitution alters both the residue size and charge. One explanation for the contribution of S357N to CXM(R) is that the asparagine side-chain produces unfavourable steric hindrance with the side chain of Val-362 changing the torsion angles of the asparagine residue, which in turn may influence the position of the loop V362-P366 adjacent to the active site. Whilst other groups have examined the contribution of H. influenzae PBPs in ampicillin resistance, this is the first report analysing their role in CXM(R).

BAL 9141, a new broad-spectrum pyrrolidinone cephalosporin: activity against clinically significant anaerobes in comparison with 10 other antimicrobials

The in vitro potency of BAL 9141, a new pyrrolidinone cephalosporin, was tested against non-duplicate strains of anaerobic bacteria. The MIC(50) was 1 mg/L against Actinomyces species, Clostridium species, Gram-positive anaerobic cocci, Porphyromonas species, Fusobacterium species, Lactobacillus species, Prevotella species and Veillonella species. The MIC(50) was 16 mg/L for Bacteroides fragilis and other Bacteroides species. BAL 9141 was not active against cefoxitin-resistant Bacteroides fragilis.

The activity of vancomycin against heterogeneous vancomycin-intermediate methicillin-resistant Staphylococcus aureus explored using an in vitro pharmacokinetic model

Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) may account for treatment failure with vancomycin and act as a precursor of vancomycin-intermediate or -resistant S. aureus. The activity of vancomycin was assessed against vancomycinsusceptible, hVISA and VISA strains in a dilutional pharmacokinetic model. Over a 48 h period, total bacteria and cells with a vancomycin-intermediate phenotype were quantified. Total counts of hVISA were reduced by vancomycin in a similar way to a vancomycin-susceptible control. The vancomycin-intermediate sub-population was eradicated from the model within one dose interval. Exposure to low vancomycin concentrations did not result in an increase in the proportion of cells which were vancomycin intermediate. Short-term exposure of hVISA to vancomycin at gradient concentrations did not increase the proportion of cells with vancomycin-intermediate phenotype.

Pharmacodynamics of gemifloxacin against Streptococcus pneumoniae in an in vitro pharmacokinetic model of infection

The pharmacodynamics of gemifloxacin against Streptococcus pneumoniae were investigated in a dilutional pharmacodynamic model of infection. Dose fractionation was used to simulate concentrations of gemifloxacin in human serum associated with 640 mg every 48 h (one dose), 320 mg every 24 h (two doses), and 160 mg every 12 h (four doses). Five strains of S. pneumoniae for which MICs were 0.016, 0.06, 0.1, 0.16, and 0.24 mg/liter were used to assess the antibacterial effect of gemifloxacin. An inoculum of 10(7) to 10(8) CFU/ml was used, and each experiment was performed at least in triplicate. The pharmacodynamic parameters (area under the concentration-time curve [AUC]/MIC, maximum concentration of drug in serum [C(max)]/MIC, and the time that the serum drug concentration remains higher than the MIC [T > MIC]) were related to antibacterial effect as measured by the area under the bacterial-kill curve from 0 to 48 h (AUBKC(48)) using an inhibitory sigmoid E(max) model. Weighted least-squares regression was used to predict the effect of the pharmacodynamic parameters on AUBKC(48), and Cox proportional-hazards regression was used to predict the effect of the three pharmacodynamic parameters on the time needed to kill 99.9% of the starting inoculum (T99.9). There was a clear relationship between strain susceptibility and clearance from the model. The simulations (160 mg every 12 h) were associated with slower initial clearance than were the other simulations; in contrast, bacterial regrowth occurred with the 640-mg simulation when MICs were > or =0.1 mg/liter. The percentage coefficient of variance was 19% for AUBKC(48), and the inhibitory sigmoid E(max) model best fit the relationship between AUBKC(48) and AUC/MIC. C(max)/MIC and T > MIC fit less well. The maximum response occurred at an AUC/MIC of >300 to 400. In weighted least-squares regression analysis, there was no evidence that C(max)/MIC was predictive of AUBKC(48), but both AUC/MIC and T > MIC were. A repeat analysis using only data for which the T > MIC was >75% and for which hence regrowth was minimized indicated that AUC/MIC alone was predictive of AUBKC(48). Initial univariate analysis indicated that all three pharmacodynamic parameters were predictive of T99.9, but in the multivariate model only C(max)/MIC reached significance. These data indicate that gemifloxacin is an effective antipneumococcal agent and that AUC/MIC is the best predictor of antibacterial effect as measured by AUBKC(48). However, C(max)/MIC is the best predictor of speed of kill, as measured by T99.9. T > MIC also has a role in determining AUBKC(48), especially when the dose spacing is considerable. Once-daily dosing seems most suitable for gemifloxacin.

Evaluation of current methods for detection of staphylococci with reduced susceptibility to glycopeptides

The sensitivity and specificity of seven methods (agar dilution, broth microdilution, Etest at 0.5 and 2.0 McFarland (McF) inocula, two agar screening methods, and population studies [PS]) were evaluated in a double-blind study involving 284 methicillin-resistant Staphylococcus aureus (MRSA) strains and 45 Staphylococcus strains with reduced susceptibilities to vancomycin (SRSV). The results were compared to the population analysis profile-area under the curve ratio method (PAP-AUC ratio compared to that of Mu3) as described by Wootton et al. The agar screening method using brain heart infusion agar (6 microg of vancomycin per ml) gave a sensitivity of 22% and a specificity of 97%. A similar method using Mueller-Hinton agar (5 microg of vancomycin per ml) gave a sensitivity of 20% and a specificity of 99%. The PS method detected 34 false positives (12%) and gave a sensitivity of 71% and a specificity of 88%. Etest using 0.5 and 2.0 McF inocula gave sensitivities and specificities of 82 and 93% and of 96 and 97%, respectively. The best Etest interpretative criteria for the 2.0 McF inoculum was > or =8 mg of vancomycin per liter and > or =8 microg teicoplanin per ml or > or =12 microg of teicoplanin per ml. The direct colony suspension inoculum for this method was found to be equally accurate in detecting (hetero-)glycopeptide-intermediate S. aureus compared to the overnight broth inoculum preparation method. Agar dilution and broth microdilution using the NCCLS breakpoint criteria for vancomycin gave sensitivities and specificities of 20 and 100% and of 11 and 100%, respectively. Using the Etest with a 2.0 McF inoculum, six different media were assessed against a selection of SRSV (n = 48) and MRSA (n = 12). Brain heart infusion agar yielded the highest sensitivity and specificity values: 88 and 88%, respectively.

A modified population analysis profile (PAP) method to detect hetero-resistance to vancomycin in Staphylococcus aureus in a UK hospital

One hundred methicillin-resistant Staphylococcus aureus (MRSA) strains, isolated between 1983 and 1999, were tested alongside the vancomycin hetero-resistant S. aureus (hVRSA) strain Mu 3, and vancomycin-resistant S. aureus (VRSA) strain Mu 50, for their resistance to vancomycin. This was achieved using the screening method described by Hiramatsu, gradient plates, agar incorporation, standard Etest, macrodilution Etest and a modified population analysis. Using Hiramatsu's screening method, 5% of the 100 MRSA were identified as VRSA and 5% identified as hVRSA, the gradient plates identified 7% hVRSA, and the standard and macrodilution Etests identified no hVRSA. Mu 3 appeared to be vancomycin-susceptible using both the agar incorporation and standard Etest methods, but was classified as hVRSA using the macrodilution Etest. The modified population analysis reliably detected vancomycin hetero-resistance in Mu 3 and identified no hVRSAs within the 100 MRSA sample.

Differentiating embryonal stem cells are a rich source of haemopoietic gene products and suggest erythroid preconditioning of primitive haemopoietic stem cells

The difficulties associated with studying molecular mechanisms important in hemopoietic stem cell (HSC) function such as the problems of purifying homogeneous stem cell populations, have prompted us to adapt the murine ES cell system as an in vitro model of HSC generation and function. We now report that careful analysis of the time course of HSC generation in differentiating ES cells allows them to be used as a source of known and novel hemopoietic gene products. We have generated a subtracted library using cDNA from ES cells collected just prior to and just following the emergence of HSCs. Analysis of this library shows it to be a rich source of known hemopoietic and hemopoietic related gene products with 44% of identifiable cDNAs falling into these camps. We have demonstrated the value of this system as a source of novel genes of relevance to HSC function by characterizing a novel membrane protein encoding cDNA that is preferentially expressed in primitive hemopoietic cells. Intriguingly, further analysis of the known components of the subtracted library is suggestive of erythroid preconditioning of the ES cell-derived HSC. We have used dot-blot and in situ analysis to indicate that this erythroid preconditioning is probably restricted to primitive but not definitive HSC.

Grain proteins as markers of genetic traits in wheat

Different protein fractionation techniques were used to define differences between a set of 8 wheat lines used in genetic mapping studies in Australia. A proteomics approach was used to establish the feasibility of identifying new protein polymorphisms for mapping purposes. Detailed analysis confirmed differences in the glutenin subunits, gliadin proteins, and 10–20 other proteins, between the mapping population parents, Cranbrook, Halberd, CD87, and Katepwa. Differences were particularly evident in the low molecular weight classes of protein. Alternative technologies were used to determine the differences in various protein classes in order to screen doubled haploid lines derived from crosses between the wheat lines. Polyacrylamide gel electrophoresis analysis allowed the mapping of loci encoding high molecular weight (HMW) and low molecular weight (LMW) glutenin subunit proteins. Reversed phase high performance liquid chromatography also allowed several loci encoding LMW glutenin subunit proteins to be mapped, as well as a new protein on chromosome 6A. Capillary electrophoresis provided a high-resolution system that was used to map several gliadin-type proteins. The studies showed that proteins provide useful genetic markers and the data are discussed from the point of view of the advantages that protein-based markers offer in providing both genotypic and phenotypic data.

Capillary electrophoresis of wheat gliadin proteins and its potential for wheat varietal identification using pattern matching software

Gliadins from 11 wheat flours were extracted with 30% ethanol and fractionated by capillary electrophoresis on a 20-µm i.d. untreated fused silica capillary using 0.1 M phosphate buffer (pH 2.5) containing polymer modifier. Capillary electrophoresis conducted at a constant current provided very good resolution and reproducibility (relative standard deviation <0.5) in mp;lt;15 min. Pattern matching of the profiles was performed with the PatMatch program to provide quantitative comparisons, using the relative mobility and intensity data for each gliadin protein. Data processing parameters, including the integration of the electrophoregram, were optimised for separation of gliadins extracted from either whole-grain or flour samples. The reproducibility and repeatability were compared using peak height and/or area percentages. The optimal window width for identifying matching gliadin peaks was 0.80–1.20% relative mobility units. Using these conditions, it was concluded that unknown varieties could be identified with a confidence level of 90–95%.

Changes in protein composition during grain development in wheat

Changes in glutenin, gliadin, glutenin subunit composition, and polymer size distribution were monitored for 4 cultivars of wheat (Triticum aestivum L.) throughout grain filling in an irrigated and non-irrigated environment over 2 seasons. The synthesis of glutenin and gliadin was modelled using a logistic function to determine the rate and duration of synthesis in response to environmental conditions. The maximum rate of synthesis of glutenin occurred approximately 6–8 days after the maximum rate of gliadins, with the duration extended by a similar period. High molecular weight glutenin subunits (HMWGS) were detected earlier than low molecular weight glutenin subunits (LMWGS). After the initial synthesis of HMWGS, there was a period at approximately mid grain filling when the rate of synthesis was reduced, followed by a period of more rapid synthesis in the latter stages of grain filling. In contrast, once detected, LMWGS increased at a faster rate than, and were in excess with respect to, HMWGS. Cultivar and environmental differences were observed, but in all cases the average molecular weight of polymeric glutenin increased throughout grain filling. Large polymers (>400 kD) increased continuously during grain filling, whereas polymers in the range 150–400 kD remained relatively constant and smaller polymers <150 kD decreased. As grain filling approached physiological maturity, there was a rapid increase in the synthesis of large polymers. The gliadin to glutenin ratio was almost the same in grain from adjacent irrigated and non-irrigated environments subjected to high temperatures at mid grain f illing, but the proportion of highly polymeric glutenin was greater from the non-irrigated environment.

Safety and tolerability of bolus intravenous colistin in acute respiratory exacerbations in adults with cystic fibrosis

OBJECTIVE

To assess the safety and tolerability of bolus intravenous doses of colistin during acute respiratory exacerbations in adults with cystic fibrosis and chronic Pseudomonas aeruginosa infection.

METHODS

Twelve patients with acute exacerbations of cystic fibrosis were enrolled in a Phase I open-label study. On day 1, patients received three doses of colistin 2 mega-units (160 mg), reconstituted in 50 mL of NaCl 0.9%, by infusion over 30 minutes three times daily. On days 2, 3, and 4, the same dose of colistin was administered by bolus injection three times a day over five minutes after reconstitution in 20, 15, and 10 mL of NaCl 0.9%, respectively. The injection was given by a nurse or physician using a hand-held syringe. If the latter dose was tolerated, it was continued for the remaining eight days of the study. If any dose was not tolerated, treatment reverted to the previously tolerated concentration, which was continued throughout the remainder of the study.

RESULTS

No serious adverse events occurred during the course of the trial. Patients without total indwelling venous access systems experienced mild to moderate injection pain. There were no clinically significant changes in renal function.

CONCLUSIONS

This study indicates that the administration of bolus intravenous colistin as 2 mega-units (160 mg) in 10 mL of NaCl 0.9% three times a day is safe. It is well-tolerated by patients with total indwelling venous access systems.

Assessment of different antibacterial effect measures used in in vitro models of infection and subsequent use in pharmacodynamic correlations for moxifloxacin

A dilutional culture in vitro pharmacodynamic model of infection was used to assess the best measure of antibacterial effect for moxifloxacin at simulated human doses of 400 mg 24 hourly for 48 h. This was then related to two pharmacodynamic parameters, the drug area under curve: MIC ratio (AUC/MIC) and the length of time that the drug concentration remained above the MIC of the bacterium (T > MIC). Twenty-one bacterial strains (Streptococcus pneumoniae n = 6; Haemophilus influenzae n = 6; Moraxella catarrhalis n = 3; beta-haemolytic streptococci n = 3; Staphylococcus aureus n = 3; MIC range 0.06-3.6 mg/L) were tested in 69 individual simulations. The measures or parameters of antibacterial effect considered were log change in viable count in the initial inoculum at 12 h (triangle up12), 24 h (triangle up24), 36 h (triangle up36), 48 h (triangle up48), maximum reduction in count (triangle up(max)); time for bacterial counts to reduce by 100-fold from the initial density (T99) or 1,000-fold (T99.9); and area under the bacterial kill curve from 0 to 24 h (AUBKC(24)) or from 0 to 48 h (AUBKC(48)). triangle up12, triangle up24, triangle up36, triangle up48, triangle up(max), T99, T99.9 did not vary over the complete range of MICs; at high MICs, especially with Gram-positive bacteria the T99 and T99.9 values were >48 h while at low MICs, especially with Gram-negative bacteria, bacterial counts were reduced below the limit of detection with triangle up12, triangle up24, triangle up36, triangle up48 and triangle up(max) exceeding >6.5 log reduction. AUBKC(24) and AUBKC(48) varied more completely over the range of MICs and more importantly had the best within-strain reproducibility (median percentage coefficient of variation <15%). The relationship between the transformed AUBKC(24) and AUC/MIC could be described by a sigmoid Emax model but the relationship with T > MIC could not. Use of weighted least squares regression to examine the combined effect of AUC/MIC and T > MIC on AUBKC(24) indicated that AUC/MIC provided a good fit to the data (r(2) = 0.94) and adding T > MIC did not improve the model fit. Cox proportional hazards regression indicated that AUC/MIC was predictive of T99 and in a multivariate model although AUC/MIC predicted outcome after fitting AUC/MIC, T > MIC was not significant. AUBKC was thus shown to be the optimum measure of antibacterial effect to use in pharmacodynamic studies of moxifloxacin and AUC/MIC the best predictor of antibacterial effect as measured by AUBKC(24) or T99. These results are in good agreement with animal data on moxifloxacin pharmacodynamics and human data for some other fluoroquinolones.

Exploration of the in-vitro pharmacodynamic activity of moxifloxacin for Staphylococcus aureus and Streptococci of lancefield groups A and G

The serum concentrations associated with the oral administration of 400 mg moxifloxacin every 24 h over 48 h in man were simulated in an in-vitro dilutional, continuous bacterial culture model of infection. The initial inoculum was 5 x 10(7)-5 x 10(8) cfu/mL and all strains were tested on at least three occasions. Two strains of Staphylococcus aureus (one methicillin susceptible, the other resistant) with moxifloxacin MICs 0.14 mg/L and 0.06 mg/L and two strains of beta-haemolytic streptococci, Lancefield Group A, MIC 0. 16 mg/L and Group G, MIC 0.4 mg/L were used. In addition, two laboratory-generated mutants with raised moxifloxacin MICs were also employed: methicillin-sensitive S. aureus (MSSA) MIC 1.0 mg/L and Group A streptococcus MIC 1.8 mg/L. The antibacterial effect of moxifloxacin was judged by changes in viable count over time, and the area under the bacterial-kill curve (AUBKC) after 24 and 48 h. For S. aureus MIC 0.14 mg/L the AUBKC(24) (log cfu/mL.h) was 77.8 +/- 4.6 and AUBKC(48) 92.0 +/- 6.9. For its mutant, moxifloxacin MIC 1.0 mg/L, the AUBKC(24) was 116.1 +/- 15.6 and AUBKC(48) 211.9 +/- 23.1, indicating decreased killing. AUBKC(24) and AUBKC(48) values of 110.7 +/- 10.3 and 130.9 +/- 21.3, respectively, were noted for the MRSA strain. The Group A streptococcus, MIC 0.16 mg/L, had an AUBKC(24) of 91.4 +/- 19.4 and AUBKC(48) of 157.0 +/- 70.9. The mutant, MIC 1.8 mg/L, had an AUBKC(24) of 127.0 +/- 1.9 and AUBKC(48) of 205.1 +/- 6.4. Despite a lower MIC (0.4 mg/L) the single strain of Group G streptococcus tested was killed poorly, AUBKC(24) 139.9 +/- 3.6 and AUBKC(48) 252.3 +/- 18.6. The pharmacodynamic parameters AUC/MIC, T > MIC, (AUC > MIC)/MIC (AUC = area under the curve, T = time) and WAUC ((AUC/MIC) (T > MIC/100)) (WAUC = weighted area under the curve) were related to AUBKC(24) and AUBKC(48) using an inhibitory sigmoid E(max) model. T > MIC was poorly related to AUBKC (r = 0.36) while AUC/MIC, (AUC > MIC)/MIC and WAUC were strongly related to AUBKC(24) (r = 0.75-0.79) and AUBKC(48) (r = 0.78-0.84). The maximum antibacterial effect was achieved with an AUC/MIC ratio of 150-200. AUC-related pharmacodynamic parameters predicted antibacterial effect better than T > MIC.

Expression and detection of hetero-vancomycin resistance in Staphylococcus aureus

Isolates of Staphylococcus aureus resistant to vancomycin have been reported but appear to be extremely rare. However, isolates displaying hetero-resistance to vancomycin (hVRSA) are reportedly common in parts of Japan (9.3% of MRSA isolated from a group of university hospitals). We have investigated the reliability of the proposed method for detection of hetero-resistant isolates and the ability of clinical S. aureus isolates to express vancomycin resistance. The original method for identification of hVRSA was found to have poor reproducibility and may select for, rather than detect, vancomycin resistance. There appears to be a spectrum of heterogeneity in the expression of resistance to vancomycin among S. aureus. Until there is a clearer understanding of the mechanism and control of vancomycin resistance in S. aureus, and reliable tests are devised, the clinical relevance of different degrees of hetero-resistance cannot be assessed.

Comparison of in-vitro pharmacodynamics of once and twice daily ciprofloxacin

The pharmacodynamics of ciprofloxacin were explored in an in-vitro continuous bacterial culture model of infection, by simulating two oral dosing regimens; 0.5 g 12-hourly (bd) and 1 g 24-hourly (od). Three strains of Escherichia coli (ciprofloxacin MICs 0.03, 0.5 and 2 mg/L); two strains of Pseudomonas aeruginosa (MICs 0.09 and 1.5 mg/L), two strains of Staphylococcus aureus (MICs 0.12 and 1 mg/L) and two strains of Streptococcus pneumoniae (MICs 0.5 and 2 mg/L) were used. Three pharmacodynamic parameters, T > MIC, C(max)/MIC and AUC/MIC (T = time, C(max) = peak serum concentration, AUC = area under the curve), were compared with area under the bacterial-kill curve (AUBKC) (after transformation of the AUBKC) using a simple E(max) or sigmoidal E(max) model. AUBKC was taken to be the main antibacterial effect measure. The models were compared by inspection of residuals and Akaike information criterion. E(max) models adequately described the relationship between AUC/MIC and AUBKC and between C(max)/MIC and AUBKC, but not between T> MIC and AUBKC. All three pharmacodynamic parameters are related to each other but multiple regression analysis indicated that AUC/MIC was the best individual predictor of AUBKC. Despite this, comparison of od and bd regimens indicates some advantage to od in terms of early antibacterial effect. Serum concentration-time curve shape has some importance in determining antibacterial effect. These data indicate that for ciprofloxacin AUC/MIC ratio is not the sole determinant of antibacterial effect.

In-vitro activity of HMR 3647 against Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and beta-haemolytic streptococci

The in-vitro activity of HMR 3647 and seven comparators (azithromycin, clarithromycin, erythromycin A, roxithromycin, penicillin G, ciprofloxacin and levofloxacin) were tested against 207 Streptococcus pneumoniae and 200 beta-haemolytic streptococci. Ten comparators (azithromycin, clarithromycin, erythromycin A, roxithromycin, ampicillin, co-amoxiclav, cefuroxime, cefotaxime, ciprofloxacin and levofloxacin) were tested against 143 Haemophilus influenzae and 58 Moraxella catarrhalis. The MIC50 of HMR 3647 for S. pneumoniae was < or =0.008 mg/L, less than that for the macrolides or quinolones tested. Pneumococci with an erythromycin A MIC of 0.06 mg/L (n = 23) had an MIC50 of HMR 3647 < or =0.008 mg/L, whereas isolates with an erythromycin A MIC > or =1 mg/L (n = 34) had an MIC50 of HMR 3647 of 0.03 mg/L, a four-fold increase. In contrast, the difference in macrolide MIC50s for the two groups was > or =64-fold. The MIC50s foro beta-haemolytic streptococci, classified by Lancefield group, were in the range 0.015 to 0.06 mg/L for HMR 3647. H. influenzae were categorized into three groups according to cefuroxime MIC: <1 mg/L (n = 72); 2-4 mg/L (n = 29); and >4 mg/L (n = 42). The MIC50 of HMR 3647 increased two-fold with increasing cefuroxime MICs; beta-lactam MICs increased much more markedly. The MIC50 of HMR 3647 for M. catarrhalis was 0.03 mg/L. HMR 3647 has good activity against respiratory tract pathogens but in-vitro susceptibility is affected by erythromycin A susceptibility in S. pneumoniae and beta-haemolytic streptococci.

Interactions between methicillin and vancomycin in methicillin-resistant Staphylococcus aureus strains displaying different phenotypes of vancomycin susceptibility

Vancomycin-sensitive, -intermediate, and -heterointermediate methicillin-resistant Staphylococcus aureus isolates were tested by using E-tests to explore the interaction of methicillin and vancomycin. For the vancomycin-intermediate and -heterointermediate strains both drugs showed antagonism at concentrations below their MICs but synergy at methicillin concentrations near the MIC. This property could be used to screen for heterointermediate S. aureus strains.

Activity of moxifloxacin, administered once a day, against Streptococcus pneumoniae in an in vitro pharmacodynamic model of infection

The antibacterial effect of moxifloxacin was studied by using an in vitro pharmacodynamic model of infection with dosing simulations of 400 mg every 24 h for 48 h. Streptococcus pneumoniae was tested by using four wild-type strains for which the moxifloxacin MICs were 0. 008, 0.12, 0.14, and 3.6 mg/liter. In addition, two isogenic mutants, generated from the strains for which the moxifloxacin MICs were </=0.12 mg/liter and for which the MICs were 1.0 and 1.6 mg/liter, were also used. Antibacterial efficacy was measured by the following indices: log change in viable count at 12, 24, 36, and 48 h; area under the bacterial kill curve (AUBKC); and time to kill 99.9% of the initial inoculum. With the three strains for which the moxifloxacin MICs were </=0.14 mg/liter, there was a marked reduction in viable count over 12 to 36 h; in contrast, with strains for which the MICs were >/=1.0 mg/liter, little killing occurred over 48 h. A sigmoid dose-response model indicated that the area under the curve/MIC ratio was strongly related to the log change in viable count at 24 and 48 h and to the AUBKC. These data indicate that moxifloxacin may have a role in management of S. pneumoniae infection.

B-cell antigens within normal and activated human T cells

In this study we compared cell surface staining for human peripheral blood lymphocyte (PBL) CD antigens by flow cytometry, with staining obtained following permeabilization of PBL using the Cytoperm method (Serotec). Six CD antigens (CD20, CD21, CD22, CD32, CD35 and major histocompatibility complex class II antigen) normally found on the surface of B cells, were also found to be expressed within T cells. We also showed, by immunoelectron microscopy, that these inappropriately expressed ('occult') CD antigens are located within cytoplasmic vesicles or within the rough endoplasmic reticulum. Following in vitro activation of T cells a distinct increase in expression of all of these cytoplasmic antigens was observed but staining at the cell surface was, by comparison, weak. We therefore propose that up-regulation of various B-cell CD antigens occurs within the cytoplasm of T cells following activation and that these antigens may be synthesized and released into the fluid-phase as soluble immunoregulatory molecules.

The antibacterial efficacy of levofloxacin and ciprofloxacin against Pseudomonas aeruginosa assessed by combining antibiotic exposure and bacterial susceptibility

Ciprofloxacin has a four-fold greater in-vitro activity than levofloxacin against Pseudomonas aeruginosa, but levofloxacin has a four-fold higher area under the serum concentration-time curve (AUC) for an equivalent dose. It has been proposed that the AUC/MIC ratio is a general predictor of antibacterial efficacy for quinolones. Using an in-vitro kill curve technique, performed in quadruplicate, with nine antibiotic concentrations and three strains of P. aeruginosa with varying quinolone susceptibility, we constructed sigmoidal dose-response curves for AUC(0-6.5)/MIC and area under the bacterial kill curve (AUBKC) or AUC(0-24)/MIC and log change in viable count at 24 h (delta24). For levofloxacin the log AUC(0-6.5)/MIC ratio to produce 50% of the maximal effect was 0.74 +/- 0.13 (r2 = 0.9435) for levofloxacin and 0.82 +/- 0.06 (r2 = 0.7935) for ciprofloxacin. The log AUC(0-24)/MIC ratio to produce 50% maximal effect was 1.58 +/- 0.13 (r2 = 0.7788) for levofloxacin and 1.37 +/- 0.12 (r2 = 0.7207) for ciprofloxacin. An AUC(0-24)/MIC ratio of 125 produced 85.4% of the maximal response with levofloxacin and 81.5% with ciprofloxacin. These data suggest that levofloxacin and ciprofloxacin have equivalent activity against P. aeruginosa at equivalent AUC/MIC ratios.

Wheat spike temperatures in relation to varying environmental conditions

Most field studies investigating the effect of temperature on growth processes use temperatures recorded within a Stevenson screen. These are likely to deviate from temperatures within the plant. This investigation reports a comparative study of methodologies and applications for measuring temperatures in the field during grain development by comparing Stevenson screen, ambient (air temperatures within the crop canopy), and wheat spike temperatures. Miniature sensors were inserted into wheat spikelets located midway on the spike of a primary tiller at anthesis. Located also within the crop canopy, and at the same height as the spike sensors, were sensors to measure ambient temperatures. Stevenson screen temperatures were also recorded at the site. Temperatures were recorded automatically every 12 min during grain filling from anthesis to maturity. Plants were grown in dryland and irrigated conditions within the same location, with the aim of determining differences in plant temperatures between stressed and non-stressed plants. Stevenson screen temperatures did not relate closely to ambient or spike temperatures. Plants growing in adequate soil moisture conditions had spike temperatures lower than ambient temperatures, but in some dryland trials, where soil moisture was limiting, spike temperatures equalled ambient temperatures, indicating that the plants were under moisture stress. Temperature differences of up to 5˚C were observed between the spikes of irrigated and non-irrigated crops on a hot day. Neither ambient nor screen temperatures gave an accurate measurement of spike temperature on hot days. Spike temperature differences between 2 cultivars, awned and awnless, were investigated. Trends were not consistent over both years; however, in 3 of the 4 environments, the maximum spike temperatures were higher for the awned cultivar (Hartog) than the awnless cultivar (Halberd). On very hot days, when ambient temperatures exceeded 40˚C, spikes of Hartog were cooler than those of Halberd.