The role of selective decontamination of the digestive tract in acute stroke

BACKGROUND

following a stroke, morbidity and mortality is high, with aspiration pneumonia being a common complication.

OBJECTIVES

to determine the levels of colonisation by and isolation of aerobic Gram-negative bacteria (AGNB) in acute stroke patients and determine the effect of selective decontamination of the digestive tract (SDD) on oral flora and whether it reduces both morbidity and mortality after an acute stroke.

DESIGN

a prospective, randomised, placebo-controlled double blind trial.

SETTING

acute stroke assessment units of three hospitals in the northwest of England.

SUBJECTS

203 patients admitted to hospital following a first acute stroke.

METHODS

participants were randomised to SDD oral gel or placebo. Swallow was assessed on admission to hospital, and oral swabs were obtained thrice weekly. Demographic and clinical data were recorded.

RESULTS

203 patients (106 males and 97 females) participated, of whom 20 died during their hospitalisation, 19 withdrew and full follow-up was obtained for the remaining 164. A total of 122 AGNB were isolated in 105 samples from 48 patients. Abnormal swallow on admission was found in 58 patients (29%). A total of 34 patients carried a single gram-negative micro-organism that was present on one or more occasions. More than one AGNB was carried in 14 patients, and organisms were significantly more likely to be isolated from the placebo group than the active group during weeks 2 and 3 of treatment (P = 0.034, chi-squared). Seven patients in the placebo group and one in the treatment group developed pneumonia (P = 0.029, Fisher's exact test).

CONCLUSIONS

high carriage of and colonisation by AGNB was found within this study, which was reduced by the addition of SDD. Although SDD reduced the presence of both organisms and documented episodes of pneumonia, mortality remained unchanged.

Clindamycin and dentistry

Clindamycin is an antimicrobial agent that dentists use in the UK for infective endocarditis prophylaxis but rarely for other clinical situations that require antimicrobial intervention. This has been largely due to its association with acute pseudomembranous colitis. Up to date information on the efficacy and safety of this antimicrobial agent should be known before prescription.

Antibiotic prophylaxis and third molar surgery

The issue of prophylactic antibiotic therapy in third molar surgery is highly controversial. The current evidence questions the benefits of routine prophylactic antibiotic therapy which does not appear to overcome the risk of undesirable outcomes after third molar removal. In our opinion there is no justification for routine antibiotic prophylaxis for third molar surgery.

An investigation of the efficacy of super–oxidised (Optident/Sterilox) water for the disinfection of dental unit water lines

AIMS

To determine the efficacy of super-oxidised water (Optident/Sterilox) in the decontamination of dental unit water lines.

METHODS

Dental units (10) were first purged with concentrated super-oxidised water. After purging, a 5% (v/v) super-oxidised water was used as a maintenance dose. Samples for microbiology were taken after 0,1,2,3,4,5,6,7 d, and each week for a further 13 weeks.

RESULTS

After purging, 5% (v/v) super-oxidised water was successful in reducing the microbial counts to zero, although in three of the units some bacteria were intermittently isolated in the first week of treatment.

CONCLUSIONS

Super-oxidised water was successful in the removal of bacteria from dental unit water supplies. Complete removal required the treatment with a purge phase of concentrated disinfectant and a maintenance phase of at least two weeks.

An investigation of therapeutic antibiotic prescribing for children referred for dental general anaesthesia in three community national health service trusts

OBJECTIVE

To investigate antibiotic prescribing for paediatric dental patients requiring general anaesthesia.

DESIGN

A prospective clinical study of children referred for dental treatment under general anaesthesia.

METHOD

Information was collected by way of a two-stage questionnaire for children attending three community NHS trusts for dental extractions under general anaesthesia between July 2001 and January 2003.

RESULTS

A total of 360 questionnaires were analysed. There was wide variation in the waiting times (0-278 days) between referral and treatment under general anaesthesia. Most children (53%) attended with dento-alveolar abscess, 46% with caries only and 1% for orthodontic extractions. Antibiotics were prescribed to 52% of patients with an abscess and 32% with caries only. Only 16% of patients presented with moderate to severe pain, 5.5% with diffuse swelling and 12% with a raised temperature. Antibiotics were prescribed for patients with diffuse swelling (63%) and raised temperature (50%) but also for patients with pain only (39%) and localised swelling (52%). Amoxicillin was the most frequently prescribed antibiotic (82%), with wide variation in all antibiotic regimens.

CONCLUSION

This study provides evidence of inappropriate prescribing of antibiotics to children referred for treatment under general anaesthesia with wide variations in the regimens employed. There was no conclusive evidence that long waiting times for definitive treatment influenced antibiotic prescribing. In some areas the delay for definitive treatment for this group of vulnerable patients was unacceptably long.

A comparison of decontamination methods used for dental burs

OBJECTIVES

This study investigated the bacterial and fungal contamination of used dental burs. A novel assay system for comparison of efficacy of pre-sterilisation cleaning techniques for dental burs was used to evaluate manual scrubbing, enzymic agents and washer-disinfectors.

METHODS

Thirty dental burs contaminated during cavity preparation were analysed for micro-biological total viable counts and species of bacteria and fungi present. To simulate clinically contaminated burs, a culture of Streptococcus sanguis NCTC 7863 was used to inoculate unused dental burs, alone and combined with blood, saliva or a mixture of blood and saliva. Contaminated burs were subjected to six pre-sterilisation cleaning techniques and the log reduction in contamination achieved by each method was assessed.

RESULTS

The microbial count from used dental burs ranged from 0 to 6.92 x 10(4) CFU ml(-1). Many potentially pathogenic species were identified. The decontamination assay demonstrated that autoclaving alone was not sufficient to sterilise dental burs. Manual scrubbing in air was less efficacious than manual scrubbing under water (p<0.001). The most effective method of pre-sterilisation cleaning for dental burs was a washer-disinfector.

CONCLUSIONS

Enzymic agents are suitable for soaking contaminated dental burs immediately after use. Washer-disinfectors are recommended as the method of choice for pre-sterilisation cleaning of contaminated dental burs.

Azithromycin and dentistry - a useful agent?

OBJECTIVES

Azithromycin has recently replaced clindamycin oral suspension for prop hylaxis of infective endocarditis (IE) in children. It is also currently recommended by the American Heart Association as an alternative to penicillin, along with clindamycin for prophylaxis of infective endocarditis in adults. The objectives of this paper were to firstly, review the current literature on the efficacy of azithromycin as a suitable prophylactic agent in the prevention of infective endocarditis; and secondly, to review its pharmacological properties as a suitable therapeutic agent in the management of odontogenic infections.

DESIGN

A review of the literature.

CONCLUSIONS

The available evidence from animal models on infective endocarditis supports the efficacy of this drug as a prophylactic agent against oral streptococci. The pharmacological properties of this agent would make it a very promising therapeutic adjunct in the management of odontogenic infections. At present there are only a small number of studies available with valuable data on the efficacy of this relatively new drug. Further investigations comparing this compound with other commonly used adjuncts would be of great benefit.

Aryl hydrocarbon receptor response to indigoids in vitro and in vivo

Indigo and indirubin have been reported to be present at low levels in human urine. The possibility that indigoids are physiological ligands of the aryl hydrocarbon receptor (AhR) has been suggested by initial studies in yeast, where indirubin was found to be 50 times more potent than 2,3,7,8-tetrachlorodibenzo[p]dioxin (TCDD), and indigo was found to be equipotent. To demonstrate that these indigoids are bona fide agonists in mammalian systems, we employed a number of in vitro and in vivo measures of AhR agonist potency. In a hepatoma cell reporter system, indigo yielded an EC50 of approximately 5x10(-6)M (indirubin 3' -oxime EC50 approximately 5x10(-7)M, indirubin EC50 approximately 1x10(-7)M). A comparison of these EC50 values with that of 2,3,7,8-tetrachlorodibenzofuran (TCDBF) ( approximately 3x10(-9)M) indicated that these compounds are less potent than classic halogenated-dibenzofurans or -dibenzo-p-dioxins. Competitive binding assays for AhR occupancy showed similar IC50 values for indirubin and TCDBF ( approximately 2x10(-9) and 5x10(-9)M), with the IC50 values of indigo and indirubin 3' -oxime being approximately 10-fold higher. When rats were treated with these indigoids in the range of 1.5-50mg/kg, induction of hepatic cytochrome P450 1A1 was detected. Differences in the rank-order of potency observed in vivo and in vitro could, in part, be explained by metabolism. Although their biological potencies are not as high as has been previously suggested, collectively the results show that these indole-derived pigments are agonists of AhR in vivo. The in vivo results suggest that solubility, distribution, and metabolism influence the response to the compounds.

Total viable counts, ATP, and endotoxin levels as potential markers of microbial contamination of dental unit water systems

OBJECTIVES

To determine if either ATP or endotoxin concentrations in water supplied by dental unit water systems (DUWS) correlated with total viable counts (TVC), and therefore could be used as a rapid, chairside measure of levels of microbial contamination.

DESIGN

A prospective trial.

METHOD

Fifty-seven water samples were taken from the 'triple spray', air rotor and source water supplies from 25 dental units in eight practices. The samples were assayed for endotoxin concentration, total ATP and TVC. A pilot study was performed to assess the relationship between TVC and total cell counts, as determined by flow cytometry.

RESULTS

ATP concentrations ranged from 22 to 958 relative light units (RLU) and free endotoxin ranged from 25 to 600 EU ml(-1). TVC varied from not detected to 2.16 x 10(4) CFU ml(-1). The ATP method proved to be a simple and rapid method that could be used at the chairside. However, there was no correlation between ATP or endotoxin concentrations and TVC in DUWS. TVC generally underestimated the total cell count by 50 to 500 fold.

CONCLUSION

Half of the water samples from DUWS exceeded recommended levels of TVC. However, ATP and endotoxin concentrations in DUWS water samples did not correlate with these TVC data and therefore could not be recommended as an alternative assay to TVC for measuring bacterial contamination or for monitoring water treatment efficacy.

Formation and Mass Spectrometric Analysis of DNA and Nucleoside Adducts by S-(1-Acetoxymethyl)glutathione and by Glutathione S-Transferase-Mediated Activation of Dihalomethanes

The dihalomethane CH(2)Cl(2) is an industrial solvent of potential concern to humans because of its potential genotoxicity and carcinogenicity. To characterize DNA damage by dihalomethanes, a rapid DNA digestion under acidic conditions was developed to identify alkali labile DNA-dihalomethane nucleoside adducts using HPLC-electrospray mass spectrometry. DNA digestion worked best using pH 5.0 sodium acetate buffer, a 30 min incubation with DNase II and phosphodiesterase II, and a 2 h acid phosphatase digest. DNA was modified with S-(1-acetoxymethyl)glutathione (GSCH(2)OAc), a reagent modeling activated dihalomethanes. Adducts to G, A, and T were detected at high ratios of GSCH(2)OAc/DNA following digestion of the DNA with the procedure used here. The relative efficacy of adduct formation was G > T > A >> C. The four DNA nucleosides were also reacted with the dihalomethanes CH(2)Cl(2) and CH(2)Br(2) in the presence of glutathione (GSH) and GSH S-transferases from bacteria (DM11), rat (GST 5-5), and human (GST T1-1) under conditions that produce mutations in bacteria. All enzymes formed adducts to all four nucleosides, with dGuo being the most readily modified nucleoside. Thus, the pattern paralleled the results obtained with the model compounds GSCH(2)OAc and DNA. CH(2)Cl(2) and CH(2)Br(2) yielded similar amounts of adducts under these conditions. The relative efficiency of adduct formation by GSH transferases was rat 5-5 > human T1-1 > bacterial DM11, showing that human GSH transferase T1-1 can form dihalomethane adducts under the conditions used. Although the lability of DNA adducts has precluded more sophisticated experiments and in vivo studies have not yet been possible, the work collectively demonstrates the ability of several GSH transferases to generate DNA adducts from dihalomethanes, with G being the preferred site of adduction in both this and the GSCH(2)OAc model system.

Systemic antimicrobials in the treatment of chronic periodontal diseases: a dilemma

The use of systemic antimicrobials in the treatment of acute and chronic periodontal diseases must be viewed as a dilemma. On the one hand, the approach is attractive because of the microbial nature of periodontal diseases but, on the other hand, evidence of benefit of these agents is equivocal for the majority of periodontal diseases and antimicrobials have the potential to cause harm. The disadvantages of systemic antimicrobials can be grouped under the headings of allergic reactions, superinfection, toxicity, drug interactions, patient compliance and, perhaps of most widespread importance, bacterial resistance. Mechanical debridement methods, including drainage of pus for acute periodontal abscesses, should be considered the first line treatment for most periodontal diseases. Systemic antimicrobials should be considered as adjuncts to mechanical debridement methods and, in chronic disease, never used alone as they can predispose to abscess formation. Adjunctive systemic antimicrobials may be considered in acute disease where debridement or drainage of pus is difficult, where there is local spread or systemic upset. In chronic periodontal diseases, adjunctive antimicrobials should be considered in early onset or rapidly progressive disease or in advanced chronic adult disease where mechanical therapies have failed or surgery is not a preferred option. Inadequate oral hygiene and tobacco smoking are contraindications to the use of antimicrobials. The value of systemic antimicrobials, where other systemic risk factors co-exist, has still to be established. The role of microbial diagnosis and sensitivity testing for antimicrobial selection at this time must be questioned.

A study to assess the effects of a new detergent-free, olive oil formulation dentifrice in vitro and in vivo

OBJECTIVE

To determine the effects of a detergent-free dentifrice containing olive oil using in vitro microbiological tests and an in vivo plaque re-growth model.

METHOD

A total of 20 subjects took part in a double blind, single-centre, crossover study in which slurry rinses were the only form of plaque control over a 5-day period. Following a washout and prophylaxis the subjects used 2x daily rinses in the absence of all other plaque control methods. Subjects returned to the clinic on the afternoon of day 5 when plaque was disclosed and assessed by plaque index and area. A further 9-day washout was carried out and the rinse period repeated to ensure that each subject had used both experimental and control slurries. In vitro microbiological experiments were conducted to examine the effects of olive oil alone and in the new dentifrice on bacterial growth and adhesion.

RESULTS

20 subjects completed the trial. The olive oil product showed a significant inhibition of plaque re-growth (17.2%) compared with a fluoride-matched control using the Turesky index (p<0.0001) and also using the planimetric technique (22.0%) (p<0.0001). Significant decreases in bacterial growth and adhesion (measured as total viable count) were detected in the presence of olive oil and the new dentifrice.

CONCLUSION

The results suggest that the experimental olive oil containing paste has potential value in the inhibition of plaque.

Acute stroke predisposes to oral gram-negative bacilli -- a cause of aspiration pneumonia?

OBJECTIVES

To assess any change in the oral flora in the mouths of stroke patients during the acute and rehabilitation phases and to determine whether this is related to episodes of aspiration pneumonia and clinical outcome.

MATERIALS AND METHODS

This observational study was carried out in hospital wards in a University teaching hospital. The subjects were patients immediately post-stroke and during the rehabilitation period, acute admissions and a group of healthy volunteers. An assessment of dentition and swallow in the presence or absence of oral aerobic gram-negative bacilli (AGNB) was correlated.

RESULTS

Of the acute stroke patients 52% had an unsafe swallow. AGNB carriage was documented in 34% of the acute stroke group. Of the 11 patients who died 55% had AGNB, 73% had an unsafe swallow and 36% had a combination of both.

CONCLUSION

AGNB is a common finding in acute stroke patients. It is not a consequence of age or acute hospitalisation and is associated with an unsafe swallow and a higher mortality.

Role of glutamic acid 216 in cytochrome P450 2D6 substrate binding and catalysis

Human cytochrome P450 (P450) 2D6 is an important enzyme involved in the metabolism of drugs, many of which are amines or contain other basic nitrogen atoms. Asp301 has generally been considered to be involved in electrostatic docking with the basic substrates, on the basis of previous modeling studies and site-directed mutagenesis. Substitution of Glu216 with a residue other than Asp strongly attenuated the binding of quinidine, bufuralol, and several other P450 2D6 ligands. Catalytic activity with the substrates bufuralol and 4-methoxyphenethylamine was strongly inhibited by neutral or basic mutations at Glu216 (>95%), to the same extent as the substitution of Asn at Asp301. Unlike the Asp301 mutants, the Gln216 mutant (E216Q) retained 40% enzyme efficiency with the substrate spirosulfonamide, devoid of basic nitrogen, suggesting that the substitutions at Glu216 affect binding of amine substrates more than other catalytic steps. Attempts to induce catalytic specificity toward new substrates by substitutions at Asp301 and Glu216 were unsuccessful. Collectively, the results provide evidence for electrostatic interaction of amine substrates with Glu216, and we propose that both of these acidic residues plus at least another residue(s) is (are) involved in binding the repertoire of P450 2D6 ligands.

A practical guide for patients undergoing exodontia following radiotherapy to the oral cavity

Dental extractions or minor oral surgery in patients who have undergone radiation therapy for cancer in the head and neck carry the risk of one of the most serious and devastating complications of head and neck radiotherapy, that of osteoradionecrosis (ORN). A totally unified approach to dental extractions following radiotherapy is lacking. The role of the general dental practitioner in management of patients following radiotherapy is crucial. Contrary to clinical impression, the risk of ORN does not decrease with time. When contemplating exodontia or minor oral surgery in the irradiated patient, special consideration should be given to issues such as radiotherapy history, surgical assessment, surgical procedure and the role of antibiotics and hyperbaric oxygen.

Oxidation of methoxyphenethylamines by cytochrome P450 2D6. Analysis of rate-limiting steps

Cytochrome P450 (P450) 2D6 is involved in the oxidation of a large fraction ( approximately 30%) of drugs used by humans and also catalyzes the O-demethylation of the model substrates 3- and 4-methoxyphenethylamine followed by subsequent ring hydroxylation to dopamine. Burst kinetics were not observed; rate-limiting step(s) must occur prior to product formation. Rates of reduction of ferric P450 2D6 were stimulated by 3- or 4-methoxyphenethylamine or the inhibitor quinidine; reduction is not the most rate-limiting step. The non-competitive intramolecular deuterium isotope effect, an estimate of the intrinsic isotope effect, for 4-methoxyphenethylamine O-demethylation was 9.6. Intermolecular non-competitive deuterium isotope effects of 3.1-3.8 were measured for k(cat) and k(cat)/K(m) for both O-demethylation reactions, implicating at least partially rate-limiting C-H bond breaking. Simulation of steady-state kinetic data yielded a catalytic mechanism dominated by the rates of (i) Fe(2+)O(2)(-) protonation (plus O-O bond scission) and (ii) C-H bond breaking, consistent with the appearance of the spectral intermediates in the steady state, attributed to iron-oxygen complexes. However, all the rates of individual steps (or rates of combined steps) are considerably higher than k(cat), and the contributions of several steps must be considered in understanding rates of the P450 2D6 reactions.

Diversity in the oxidation of substrates by cytochrome P450 2D6: lack of an obligatory role of aspartate 301-substrate electrostatic bonding

Cytochrome P450 (P450) 2D6 was first identified as the polymorphic human debrisoquine hydroxylase and subsequently shown to catalyze the oxidation of a variety of drugs containing a basic nitrogen. Residue Asp301 has been characterized as being involved in electrostatic interactions with substrates on the basis of homology modeling and site-directed mutagenesis experiments [Ellis, S. W., Hayhurst, G. P., Smith, G., Lightfoot, T., Wong, M. M. S., Simula, A. P., Ackland, M. J., Sternberg, M. J. E., Lennard, M. S., Tucker, G. T., and Wolf, C. R. (1995) J. Biol. Chem. 270, 29055-29058]. However, pharmacophore models based on the role of Asp301 in substrate binding are compromised by reports of catalytic activity toward substrates devoid of a basic nitrogen, which have generally been ignored. We characterized a high-affinity ligand for P450 2D6, also devoid of a basic nitrogen atom, spirosulfonamide [4-[3-(4-fluorophenyl)-2-oxo-1-oxaspiro[4.4]non-3-en-4-yl]benzenesulfonamide], with K(s) 1.6 microM. Spirosulfonamide is a substrate for P450 2D6 (k(cat) 6.5 min(-)(1) for the formation of a syn spiromethylene carbinol, K(m) 7 microM). Mutation of Asp301 to neutral residues (Asn, Ser, Gly) did not substantially affect the binding of spirosulfonamide (K(s) 2.5-3.5 microM). However, the hydroxylation of spirosulfonamide was attenuated in these mutants to the same extent (90%) as for the classic nitrogenous substrate bufuralol, and the effect of the D301N substitution was manifested on k(cat) but not K(m). Analogues of spirosulfonamide were also evaluated as ligands and substrates. Analogues in which the sulfonamide moiety was modified to an amide, thioamide, methyl sulfone, or hydrogen were ligands with K(s) values of 1.7-32 microM. All were substrates, and the methyl sulfone analogue was oxidized to the syn spiromethylene carbinol analogue of the major spirosulfonamide product. The D301N mutation produced varying changes in the oxidation patterns of the spirosulfonamide analogues. The peptidometic ritonavir and the steroids progesterone and testosterone had been reported to be substrates for P450 2D6, but the affinities (K(s)) were unknown; these were estimated to be 1.2, 1.5, and 15 microM, respectively (cf. 6 microM for the classic substrate bufuralol). The results are consistent with a role of Asp301 other than electrostatic interaction with a positively charged ligand. H-Bonding or electrostatic interactions probably enhance binding of some substrates, but our results show that it is not required for all substrates and explain why predictive models fail to recognize the proclivity for many substrates, especially those containing no basic nitrogen.

A survey of antibiotic prescribing by maxillofacial consultants for dental extractions following radiotherapy to the oral cavity

OBJECTIVES

To analyse the antibiotic prescribing trends for exodontia and minor oral surgery in patients with a history of radiotherapy. Also, to evaluate the use of hyperbaric oxygen as a separate modality in the prevention of osteoradionecrosis.

DESIGN

A survey of antibiotic prescribing involving the analysis of a questionnaire which included the management of three patients with a history of head and neck malignancy.

METHOD

The heads of the departments in each unit in the UK were sent a closed-response questionnaire. Antibiotic prescribing was assessed in three case scenarios. Case one referred to a patient that had surgery alone as part of the management of head and neck cancer, who needed the surgical removal of second molar roots. Case two referred to a patient that had surgery and adjuvant radiotherapy as part of the management of head and neck cancer, and needed the same procedure as in case one. Case three included a patient with a history of surgery and adjuvant radiotherapy, who required the extraction of three mobile and periodontally-involved lower incisors. Consultants were also asked about the use of hyperbaric oxygen in the patients who had radiotherapy as part of their treatment strategy.

RESULTS

A total of 109 questionnaires were sent to all the Maxillofacial Units in the UK. The response rate was 73%. In patients with a history of radical surgery alone for the management of head and neck cancer, 20% of the surgeons advocated pre-operative antibiotics for the surgical removal of lower posterior teeth. In contrast, in the patient with a history of adjuvant radiotherapy 86% supported pre-operative antimicrobial use for the surgical removal of the same teeth. In the extraction of mobile and periodontally involved lower incisors in the previously irradiated patient, 63% of the clinicians supported pre-extraction antibiotics. Postoperative antibiotics were advocated in 52% in the first case, 89% in the second case and 71% in the third case. 34% of the clinicians advocated hyperbaric oxygen for surgical removal of posterior teeth and 15% for the extraction of mobile anterior teeth.

CONCLUSIONS

The use of peri-extraction antibiotics was favoured among oral and maxillofacial surgeons. There was little enthusiasm towards the use of hyperbaric oxygen as a prophylactic measure, alone or in conjunction with an antimicrobial regime. Control randomised trials that will measure the effectiveness of hyperbaric oxygen and the appropriate use of antibiotics for prophylaxis in pre- and post-operative regimes are necessary to evaluate the use of these modalities.

Purification of cytochrome P-450 enzymes

Among the liver P-450 xenobiotic-metabolizing enzymes, P450-2E1 is of interest because of its activation of potent carcinogens, and P-450 1A2 is of interest because of its role in oxidation of drugs and carcinogens. This unit describes column chromatography protocols for purification of recombinant forms of these enzymes expressed in a bacterial expression system.

A preliminary investigation of the microbiology and endotoxin content in the water reservoirs of benchtop non-vacuum autoclaves

To determine the microbial content and endotoxin concentration in the water reservoirs of benchtop autoclaves used in general dental practice.

DESIGN

The study was done in two stages. Firstly water samples were taken daily from the reservoirs of 20 autoclaves used in general dental practices for six days. The microbial content and endotoxin concentration was determined. Second the practitioners were instructed to wash and clean the reservoirs of the autoclaves each morning prior to refilling with fresh water. The reservoirs were sampled in the evenings after a day's use and the microbial content and endotoxin concentration determined.

RESULTS

The total viable count of bacteria before cleaning varied from 2,300 - 8 x 10(4) cfu/ml and after from 0-40 cfu/ml. The endotoxin concentrations before cleaning varied from 360-2,200 EU/ml and after 0-80 EU/ml.

CONCLUSIONS

The reservoirs of non-vacuum benchtop autoclaves can become severely contaminated with micro-organisms particularly Gram-negative bacteria. The endotoxin content of the reservoirs can get to high and unacceptable concentrations. Draining the water reservoir and cleaning on a daily basis reduces the microbial content and the endotoxin concentration to acceptable levels.

Random mutagenesis of human cytochrome p450 2A6 and screening with indole oxidation products

Cytochrome P450 (P450) 2A6 mutants from randomized libraries generated in the substrate recognition sequence (SRS) regions were screened in Escherichia coli on the basis of indole metabolism. SRS 3 and 4 libraries yielded colonies that produced indigo at least as well as wild-type (WT) P450 2A6, and some colonies were consistently more blue upon replating. One mutant, F209T, showed indole 3-hydroxylation <WT but had a k(cat) for coumarin 7-hydroxylation 13-fold >WT. The double mutant L240C/N297Q consistently produced very blue colonies. Five mutants yielded mixtures of pigments from indole different than WT, as judged by visible spectra and HPLC of products. When bacteria expressing the mutants were grown in the presence of each of 26 substituted indoles, a variety of patterns of formation of different dyes was seen with several of the mutants. This approach has potential value in understanding P450 2A6 function and generating new dyestuffs and other products.