Recombinant production of serine hydroxymethyl transferase from Streptococcus thermophilus and its preliminary evaluation as a biocatalyst

The glyA gene encoding a serine hydroxymethyl transferase (SHMT) with threonine aldolase activity was isolated from Streptococcus thermophilus YKA-184 chromosomal DNA. This aldolase is a pyridoxal 5'-phosphate-dependent enzyme that stereospecifically catalyzes the interconversion of L-threonine to glycine and acetaldehyde. The enzyme was overexpressed in Escherichia coli M15 as a recombinant protein of 45 kDa with a His6-tag at its N-terminus. The recombinant enzyme was purified to homogeneity by a single chromatographic step using Ni-nitrilotriacetic acid affinity, obtaining a high activity-recovery yield (83%). Lyophilized and precipitated enzymes were stable at least for 10 weeks when stored at -20 degrees C and 4 degrees C. It was observed that the Km for L-allo-threonine was 38-fold higher than that for L-threonine, suggesting this enzyme can be classified as a specific L-allo-threonine aldolase. The optimum pH range of threonine aldolase activity for the recombinant SHMT was pH 6-7. When tested for aldol addition reactions with non-natural aldehydes, such as benzyloxyacetaldehyde and (R)-N-Cbz-alaninal, two possible beta-hydroxy-alpha-amino acid diastereoisomers were produced, but with moderate stereospecificity. The enzyme showed potential as a biocatalyst for the stereoselective synthesis of beta-hydroxy-alpha-amino acids.

Ultrastructural and quantitative age-related changes in capillaries of the dorsal lateral geniculate nucleus

An ultrastructural and quantitative study of age-related changes in the capillaries of the dorsal lateral geniculate nucleus was carried out using male Wistar rats aged 3, 24, and 28 months. The most important structural changes were found in the basal lamina: thickenings either homogeneously distributed or in specific points; spurs towards the astrocyte sheath; and osmiophilic membrane-like inclusions located within the basal lamina. Endothelial cells and pericytes showed an increase in inclusions and dense bodies in the cytoplasm. The quantitative study showed that the most pronounced alteration was the thickening of the basal lamina, which existed at 24 months. Later, at 28 months, thinning of the endothelial cells was observed together with an increase in mitochondria size and the number of pinocytic vesicles. These changes could be an endothelial cell response to compensate for the increasing transport difficulties caused by the thickening of the basal lamina. The progressive age-related changes observed in the structure of the capillaries might have an effect on the regulation of blood and brain tissue exchanges, and thus might contribute to the development of degenerative alterations in surrounding aging neurones.

Oral versus intravenous antibiotic treatment for febrile neutropenia in cancer patients

BACKGROUND

Fever occurring in a neutropenic patient remains a common life-threatening complication of cancer chemotherapy. The common practice is to admit the patient to hospital and treat empirically with intravenous broad-spectrum antibiotics. Oral therapy could be an alternative approach for selected patients.

OBJECTIVES

To compare the efficacy of oral antibiotics versus intravenous (IV) antibiotic therapy in febrile neutropenic cancer patients.

SEARCH STRATEGY

We searched the Cochrane Cancer Network Register of trials (November 2002), the Cochrane Library (issue 2, 2002), MEDLINE (1966 to 2002), EMBASE (January 1980 to 2002) and LILACS (1982 to 2002). We searched several databases for ongoing trials. We checked the conference proceedings of the Interscience Conference of Antimicrobial Agents and Chemotherapy (ICAAC) 1995 to 2002 and all references of included studies and major reviews were scanned.

SELECTION CRITERIA

Randomised controlled trials comparing oral antibiotic/s to intravenous antibiotic/s for the treatment of neutropenic cancer patients with fever. The comparison between the two could be started initially (initial oral), or following an initial course of intravenous antibiotic treatment (sequential).

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial eligibility, methodological quality and extracted data. Data concerning mortality, treatment failures and adverse events were extracted from included studies assuming an "intention-to-treat" basis for the outcome measures whenever possible. Relative risks (RR) with 95% confidence intervals (CI) for dichotomous data were estimated.

MAIN RESULTS

Fifteen trials (median mortality 0, range 0 to 8.8%) were included in the analyses. The mortality rate was similar comparing oral to intravenous antibiotic treatment (RR 0.91, 95% CI 0.51 to 1.62, 7 trials, 1223 patients). Treatment failure rates were also similar (RR 0.94, 95% CI 0.84 to 1.05, all trials). No significant heterogeneity was shown for all comparisons but adverse events. This effect was stable in a wide range of patients. Quinolones alone or combined with another antibiotics were used with comparable results. Adverse reactions, mostly gastrointestinal were more common with oral antibiotics.

REVIEWERS' CONCLUSIONS

Based on the present data, oral treatment is an acceptable alternative to intravenous antibiotic treatment in febrile neutropenic cancer patients (excluding patients with acute leukaemia) who are haemodynamically stable, without organ failure, not having pneumonia, infection of a central line or a severe soft-tissue infection. The wide confidence interval for mortality allows the present use of oral treatment in groups of patients with an expected low risk for mortality, and further research should be aimed at clarifying the definition of low risk patients.

Crystal growth rates of diblock copolymers in thin films: influence of film thickness

Using optical and atomic force microscopy we determined the growth rate of polymer crystals in thin films of low molecular weight poly(styrene-ethyleneoxid) block copolymers. We focused in particular on films either thinner or slightly thicker than the thickness of a crystalline lamella (L). At a given temperature, three distinctly different growth rates were observed for i) crystals grown from adsorbed monolayers thinner than L, ii) "primary" compact lamellar crystals in films thicker than L and iii) "secondary" crystals formed from molecules remaining on top of ii). The growth rate of primary crystals did not indicate a dependence on film thickness. Crystals from monolayers grew by a factor of 30 more slowly than primary crystals. Secondary crystals grew faster than crystals from monolayers but slower than primary crystals and the degree of deviation from the growth rate of primary crystals was found to depend on the value of L, which varied with temperature. The mechanisms responsible for the differences in growth rate are discussed in terms of the amount of available polymers and the controlling influence of diffusion towards the crystal front.

[The Ditrame (ANRS 049) clinical trial aimed at reducing the mother-child transmission of HIV in Abidjan. Participants' understanding of the trial principles]

OBJECTIVE

The HIV vaccine attempts in developing countries have underlined many ethical questions on the informed consent of the participants. These problems have already been encountered in the context of studies on the prevention of mother-child transmission (MCT) of HIV in Africa. This study is aimed at describing the level of understanding and interpretations that these women have of the clinical trial, randomisation and placebo, as well as their motivations for participating in the study.

METHODS

This was a qualitative study conducted in 1997 by a sociologist in the form of in-depth, structured interviews among 57 women participating in a clinical trial on the prevention of MCT of HIV. The interview included a section on the representation of MCT then questions on the eventual sharing of information concerning the HIV-infection status, the motivations for participating in the study and the understanding of the randomIsation and the placebo.

RESULTS

Nearly half of the women had not shared the result of their blood test with anyone. Their isolation enhanced the difficulties in getting information on the study. The notion of a probability of transmission was not easy to explain in terms adapted to the level of education of the women. The randomisation was understood as a number pulled out of a hat during a lucky draw. The women did not really understand the pictures used to describe the placebo. They claimed that they wanted to participate in the study essentially to protect their child and to have access to treatment.

CONCLUSION

The correct information of patients participating in clinical trials requires repeated interventions throughout the research period. When there is no social protection, the notion of freedom of choice itself, including the idea of informed consent, is relative and the pragmatic choices made by the women clearly show this. These elements must be taken into consideration in the projects of vaccination trials.

Ultrastructural changes in thyroid perifollicular capillaries during normal postnatal development and after infrared laser radiation

This study was carried out on the perifollicular capillaries of the thyroid gland during postnatal (PN) development in normal conditions and after irradiation (46.8 J/cm(2)) with an infrared (IR) laser (904 nm). This was done using 11-, 21-, and 35-day-old Wistar rats. The changes in the capillaries were determined using quantitative methods as well as electron microscopy. During normal PN development the most relevant changes were an increase in the size of the capillaries, especially the lumen, thinning of the endothelium and an increase in the size of pinocytotic vesicles. Our results suggest that during PN development, the capillaries undergo some growth and maturation processes until they reach the optimal morphological conditions for their exchange functions. IR laser irradiation seems to stimulate the growth and maturation of endothelial cells in the youngest rats, while in older ones it causes irregular thickening of the endothelium and a reduction of the capillary lumen. These changes could be a sign of functional alterations in follicular cells caused by exposure to IR laser.

[AIDS and social situations of women in Africa: from notions to research methods]

When researchers or actors intend to analyse women's situations in the context of AIDS in Africa, they are conducted to take into account the whole context these women live in: their access to care and prevention, their ability to make choices in their emotional, sexual and marital life, their access to education and to a gainful employment. It is also important in such an approach to define precisely the notions used. This paper proposes first to describe the several realities existing under the notions of vulnerability, autonomy, negotiation, sexuality, prostitution, motherhood and mother and child health. Through examples from researches conducted in Côte d'Ivoire and in other African countries, we enlighten how stereotypes are still used to describe women's situations in Africa. We insist on the need to propose fine-tuned and balanced analyses, in order to avoid sweeping generalisations that are harmful to women themselves. Secondly, we describe the methodological tools that can be used in this kind of analysis of notions and contexts in gender relations. We describe qualitative and quantitative survey techniques. For each one, we emphasise their requirements but also their effects on our research process on women's experiences facing AIDS.

Meloxicam in acute episodes of soft-tissue rheumatism of the shoulder

OBJECTIVE

This double-blind, randomised trial compared the efficacy and safety of meloxicam vs piroxicam in patients with soft-tissue rheumatism of the shoulder.

SUBJECTS

599 outpatients at 88 centres in 9 countries.

TREATMENT AND METHODS

Oral meloxicam 7.5 mg, meloxicam 15 mg or piroxicam 20 mg, once-daily for 14 days. The primary efficacy endpoint was the assessment of pain on day 7 relative to day 1.

RESULTS

Once-daily treatment with meloxicam 7.5 or 15 mg was comparable to piroxicam. A significantly higher proportion of meloxicam-treated patients had pain relief within day 1 or day 3. The incidence and intensity of adverse events was comparable between the treatment groups, although fewer patients in the meloxicam groups withdrew due to adverse events. There were no apparent differences between the two meloxicam doses.

CONCLUSIONS

Treatment with meloxicam was at least as effective as treatment with piroxicam, with a favourable global tolerability for both doses of meloxicam.

Angiosarcoma arising on rhinophyma

We report an 82-year-old man who presented with a tumor which had developed over the previous year on the right nasal ala of a rhinophyma. Histopathological, immunohistochemical, and electron microscopic study confirmed the diagnosis of angiosarcoma on the head and neck. He was treated with radiotherapy of the tumor and cervical adenopathy, which developed later. The possible etiological and pathogenetic role of lymphedema due to inflammatory flares of rosacea on the nose is discussed, together with the histological and immunohistochemical data leading to the diagnosis of this tumor.

The tau gene A0 allele and progressive supranuclear palsy

BACKGROUND

Recent studies have shown an association between a polymorphic tandem repeat allele, located in intron 9, of the tau gene and progressive supranuclear palsy (PSP).

OBJECTIVE

To investigate this tau polymorphism in individuals with a clinical diagnosis of sporadic or familial PSP as well as in cases confirmed by pathology.

METHODS

We analyzed the frequency of tau intronic polymorphism, the presence of linkage in two families with multiple cases of PSP, the splicing of exon 10, and direct sequence of the tau gene.

RESULTS

We found that patients with a clinical diagnosis of sporadic or familial PSP and individuals with PSP confirmed by neuropathology have greater prevalence of the A0 allele and A0/A0 genotype than controls. This finding, however, was also true for asymptomatic relatives of individuals with PSP. Linkage analysis in familial PSP excluded the location of the gene in the region 17q21. Furthermore, no significant differences were found in the level of expression of exon 10 in PSP, A0/A0 brain with respect to Alzheimer A3/A3 brain. We found no mutations in the tau gene in individuals with familial PSP.

CONCLUSIONS

A mutation in the tau gene was not the primary cause of familial PSP. The role of tau and the tau A0 allele in white PSP patients remains unknown, although it may represent a genetic risk factor for several neurodegenerative disorders.

A quantitative investigation of microvascular changes in the thyroid gland after infrared (IR) laser radiation

We present an ultrastructural study of thyroid capillaries in which 50-day-old rats Wistar rats, were irradiated with an infrared (IR) laser, (total dose, 46.80 J/cm2), the tissue quantified 1 day after ending treatment and a quantitative capillary analysis carried out by light and electron microscopy. Light microscopy was used to calculate capillary volume density revealing a significant increase in the irradiated rats. The quantitative measurement of parameters by electron microscopy required a two stage analysis: Level I, Electron Microscopy (Magnification x5,000); and Level II, Electron Microscopy (Magnification x26,000). At Level I, the following parameters were measured in each capillary: capillary area, capillary diameter, luminal area, luminal diameter, endothelial area, nuclear area and mean endothelial thickness. At Level II, pinocytotic vesicle diameter and their numerical density in endothelial cells were evaluated. Electron microscopic analysis revealed an increased luminal area in the capillaries of the irradiated rats. They also presented a decrease in endothelial cell thickness and vesicular diameter and an increase in vesicle numerical density. This latter increase is indicative of presumptive changes in capillary permeability, but the possible functional significance of these morphological changes in the endothelial cells requires further investigation.

[Behavioral evaluation of the unilateral lesion model in rats using 6-hydroxydopamine. Correlation between the rotations induced by D-amphetamine, apomorphine and the manual dexterity test]

INTRODUCTION

Evaluation of rotatory activity induced by dopaminergic agonists is the most widely used test of conduct for the measurement of dopaminergic depletion of a unilateral lesion of the striatonigral pathway caused by 6-hydroxydopamine (6-OHDA) in rats, since it is quantitatively related to the extension of the dopaminergic denervation.

OBJECTIVE

The objective of this study was to evaluate, from different angles, the changes in conduct seen in the model of unilateral lesion with 6-OHDA and to establish correlation with the rotation induced by D-amphetamine and by apomorphine and the ladder test.

MATERIAL AND METHODS

Male Wistar rats were used. Lesions were produced in the SNpc by stereotactic injection of 6-OHDA into the right hemisphere and the effectiveness of the lesions was studied using the rotary conduct induced by D-amphetamine and apomorphine. The motor ability of the front legs was measured by the ladder test, carried out under standard and forced conditions.

RESULTS

All the animals with lesions had difficulty in reaching food with both legs, although the most pronounced deficit was in the leg contralateral to the lesion. The ladder test correlated better with rotatory activity induced by apomorphine than by D-amphetamine.

CONCLUSION

The animals with most dopamine loss showed most deficient use of their front legs.

[Factors that lead to death of neurons in neurodegenerative diseases]

OBJECTIVE

The objective of this paper was to review information related to the various factors which may trigger the mechanisms of cell death, induced or programmed, which take place in the nervous system and their relationship with the aetiopathogenesis of the neurodegenerative diseases.

DEVELOPMENT

In recent years it has been recognized that cell death may be not only the consequence of accidental damage but also a sign of a suicide programme. This form of death is currently known as apoptosis. It is a process which is morphologically distinct from accidental cell death or necrosis. It does not cause an inflammatory response. This type of death is not only involved in the development and haemostasis of tissues, but also in setting off neuronal degeneration in experimental models of Parkinson's disease, Huntington's chorea, etc.

CONCLUSIONS

In the cell death occurring in neurodegenerative diseases there is more than one induction mechanisms. Understanding the factors which trigger cell death, and the chain of events leading to this, gives grounds for the design of new pharmacological strategies for the treatment of these diseases.

[Simultaneous transplantation of fetal mesencephalic cells to the striatum and globus pallidus of rats with lesions induced by 6-hydroxydopamine]

INTRODUCTION

Studies of neural transplants in experimental models of Parkinson's disease have concentrated their attention on ectopic transplants of foetal mesencephalic cells to denervated striatum. However, the external globus pallidus has recently been shown to play an important part in the physiopathology of this disease.

OBJECTIVE

Bearing in mind the importance of loss of extra-striatal dopamine in the genesis of the clinical signs found in parkinsonism, the objective of this study was to evaluate the effect of foetal mesencephalic transplantation to the globus pallidus of hemiparkinsonian rats.

MATERIAL AND METHODS

Following conventional transplantation methodolgy, suspensions of cells from the ventral mesencephalum of rat embryos (E-14) were implanted. The tissue was grafted into the striatum, pallidum-striatum and pallidum areas of rats with unilateral lesions of the striatonigral bundle. One, two, three and six months after transplantation, the rotatory activity induced by D-amphetamine was evaluated. The rotatory behaviour induced by apomorphine was evaluated at three months. Motor ability of the front legs was evaluated in all experimental groups three months after transplantation using the 'ladder test'.

RESULTS

In the experimental groups in which a transplant was made to the globus pallidus there was a significant reduction (p < 0.01) in rotatory activity induced by D-amphetamine and by apomorphine as compared with the non-transplanted groups.

CONCLUSIONS

Transplants of foetal dopaminergic cells survive in the globus pallidus of hemiparkinsonian rats and can improve the rotational activity induced by dopaminergic agonists.

Evaluation of persistence and distribution of Salmonella serotype isolation from poultry farms using drag-swab sampling

The consistency and persistence of isolation of specific serotypes of Salmonella were evaluated on a 31-farm broiler complex following four complete sampling periods. A total of 25 different serotypes were isolated, with multiple serotypes and were frequently isolated simultaneously from individual farms. When the serotypes recovered from individual farms were further examined, common serotypes were isolated from individual farms on only seven occasions. Furthermore, on only five occasions were multiple serotypes recovered from individual farms on consecutive samplings. A casual association of common serotype isolations among farms with similar flock placement dates was observed in one sampling period. These results indicate little predictability or consistency of Salmonella serotype isolation on individual farms over time.

Quantitation of dopaminergic neurons in 3-dimensional reaggregate tissue culture by computer-assisted image analysis

Three-dimensional (3D) reaggregate tissue culture provides a means of quantitatively assessing neuronal cell survival under a variety of experimental conditions. A method is presented for estimation of, and comparison between, the total numbers of cells of a given neurochemical type within individual experimental flasks. The method involves cell counting from random reaggregate sections, determination of sectional volumes, and of 3D reaggregate volumes by a novel image-analysis computer system.

Predictive value of multiple drag-swab sampling for the detection of Salmonella from occupied or vacant poultry houses

The results of four independent complete drag-swab samplings of a 31-farm broiler-production complex are described. Samplings of vacant poultry farms (i.e., between flocks) and occupied farms (i.e., containing chickens) were completed in four 3-day intervals beginning in July 1992 and ending in May 1993. During the first two sampling periods, two drag-swab assemblies were dragged through each individual house and pooled into one sample to evaluate overall incidence of Salmonella detection among vacant and occupied houses. During the second two sampling periods, four drag-swab assemblies were dragged through houses to evaluate frequency of Salmonella detection on individual assemblies within each house. Over the four sampling periods, mean isolation frequencies were 42.2% for vacant poultry farms and 76.2% for occupied poultry farms. When four assemblies were dragged in vacant houses and cultured separately, the probability of detecting salmonellae contamination increased with increasing numbers of assemblies, indicating that multiple drag-swab assemblies should be used for sampling either vacant or occupied broiler houses for the presence of Salmonella. On vacant farms, 89.5% of the total isolations occurred in only one house of two-house farms; the remaining 10.5% of farms were positive in both houses. Salmonella isolation from occupied farms occurred in 54.2% of the samplings in only one house, whereas 45.8% of occupied farms were positive in both houses. These data show a higher frequency of Salmonella isolation on multiple swabs in occupied poultry houses, possibly indicating a quantitatively greater presence of Salmonella in these houses.

Application of morphometric methods to the cytologic study of intradermal nevi

Twenty-one intradermal nevi were studied by morphometric methods in an attempt to morphologically characterize the two types of nevus cell--epithelioids, type A, and fusiforms, type C--and to quantify the differences between them. Morphometric parameters of the intradermal nevi were compared with similar parameters of melanocytes and melanoma cells so that the maturation rates of the nevi cells could be established and to see if the parameters might indicate the degree of malignancy. Superficial nevus cells were differentiated from deep cells by their larger size and larger nuclear area. Nuclear area appeared to have potential for differentiating benign from malignant tumors. Decrease in cellular area appeared to indicate maturation rather than atrophy. Melanoma cells were differentiated by their larger size. Cell nuclear perimeter appeared to have confirmatory value, while cell perimeter was inconclusive.

[Acquired cystic renal disease. Association with hypernephroma]

Emergence of multiple bilateral renal cysts observed in patients undergoing periodic haemodialysis is 40%. The pathology, known as Acquired Cystic Renal Disease (A.C.R.D.) presents a high association to renal cancer. Two cases of A.C.R.D. and their association with hypernephroma, one resulting in secondary retroperitoneal haemorrhage and the other in intracystic haemorrhage, are presented. Forms and diagnosis are analyzed, insisting upon the need of monitoring the patients in haemodialysis from the point of view of tumour emergence.

Incidence and features of liver disease in patients on chronic hemodialysis

We examined the incidence and features of liver disease and the presence of serologic markers of hepatitis B virus (HBV) infection in 134 patients on hemodialysis for 2 to 14 years. Twenty-three patients (17%) had had a single episode of acute hepatitis while on dialysis and two patients had had two episodes, which were attributed to infection by hepatitis B virus in 7 instances and by hepatitis non-A, non-B virus in 20. Chronicity supervened in 4 cases of hepatitis B (57%) and in 14 cases of hepatitis non-A, non-B (70%). A prolonged rise of serum aminotransferases, which was not preceded by acute hepatitis, was detected in 23 additional patients (17%). Acute hepatitis and prolonged hypertransaminasemia were more frequent in patients dialyzed at a hospital unit than in patients dialyzed outside the hospital or at home. These observations indicate that development of acute and chronic liver disease, mainly hepatitis non-A, non-B, is frequent in patients on chronic hemodialysis, particularly in those dialyzed in hospital. Serologic evidence of current or past infection by HBV was detected in 57 patients (42%) with sustained positivity of HBV serum markers. Transient positivity for anti-HBc, anti-HBs, or both, possibly related to passive transmission of antibodies by blood transfusion, was observed in 20 patients (15%). These findings indicate that periodic, repeated testing for HBV serum markers is necessary only in a minority of patients on long-term hemodialysis.

[Ascites and pleural effusion. Study and follow-up of 79 patients]

We reviewed 79 patients with a picture of pleural effusion (EP) and ascites, who represented 8% of a total of 982 pleural effusions studied. Liver cirrhosis (CH), 37 cases (47%), disseminated carcinomatosis, 31 cases (39.5%), and congestive heart failure, 6 cases (7%), were the main causes. We made two groups of liver cirrhosis: A) liver cirrhosis with hydropic decompensation, 12 patients (15%), and B) liver cirrhosis with an additional complication added to the above, 25 patients (31.5%), this being infectious in 88% of the cases. In the B group there were cases of left hydrothorax, more features of effusion and a lower survival at 3 months of follow-up than in tha A group. Effusions of neoplastic origin were most frequently seen in tumors of the ovary, digestive system, lymphomas and undetermined origin. In malignant effusions, the cytology was positive in pleura in 60% and in ascites in 55%. Twenty percent of peritoneal fluids and 47% of pleural effusions were serohemorrhagic and 100% and 88%, respectively, were of exudative nature. In liver cirrhosis the ascites was serofibrinous and transudated (100% in group A and 85.5% in B) and the pleural effusion was a serofibrinous transudate except in the cases in which there was an added infection. We confirm the ominous prognosis of the coexistence of pleural effusion and ascites.

The parascapular flap: a new cutaneous microsurgical free flap

We present the anatomic study and the clinical free transfer of a new donor site. This new flap is called the parascapular flap. It is under the dependence of a direct cutaneous artery that is a vertical terminal branch of the circumflex scapular artery, itself a branch of the subscapular artery. The flap is outlined along the free lateral border of the scapula, and it provides large surface coverage with easy primary closure of the donor site. The surface can even be extended by association of the flap with the latissimus dorsi muscle flap. With this flap, both skin and muscle areas are under the dependence of a single pedicle that is the subscapular artery.

Penicillin and tetracycline resistance plasmids in Staphylococcus epidermidis

The genetic nature of penicillin (Pc) and tetracycline (Tc) resistance plasmids in Staphylococcus epidermidis were studied and compared with those in S. aureus. Of 10 S. epidermidis strains transduced for penicillin resistance, we could isolate Pc plasmids from only 3. One of these plasmids also encoded for cadmium resistance and another encoded for resistance to ethidium bromide, traits also associated with S. aureus Pc plasmids. Endonuclease fingerprinting of the Pc plasmids from the two species revealed extensive heterogeneity. Two S. epidermidis strains were also transduced for tetracycline resistance. Both harbored plasmids indistinguishable from S. aureus Tc plasmids as judged by endonuclease fingerprinting. These data suggest that genetic exchange between S. aureus and S. epidermidis occurs in vivo.

Nature of the genetic determinant controlling encapsulation in Staphylococcus aureus Smith

Two strains of Staphylococcus aureus, Smith and M, were studied for the elimination of encapsulation. For S. aureus M, encapsulation was stable. For S. aureus Smith, spontaneous loss of encapsulation was 1.3% and increased markedly in medium containing surface-active agents. In the presence of sodium dodecyl sulfate, unencapsulated cells had a considerable selective advantage. Attempts to demonstrate covalently closed circular plasmid deoxyribonucleic acid were unsuccessful. In cultures of unencapsulated cells, encapsulated cells were observed occasionally. These data argue against a plasmid location for the determinants controlling encapsulation in this organism in spite of a high spontaneous loss of this character.

Location of the coagulase gene in Staphylococcus aureus

Evidence is presented for the chromosomal location of the coagulase determinant in most strains of Staphylococcus aureus. By the use of a pour-plate technique, transduction of the capacity to produce coagulase to a coagulase-negative mutant of S. aureus was studied. The frequencies of transduction were low unless the transducing phage was exposed to ultraviolet irradiation and the recipient was lysogenised with the transducing phage. Attempts to transfer the coagulase gene from S. aureus to S. epidermidis were not successful.