mefE is necessary for the erythromycin-resistant M phenotype in Streptococcus pneumoniae

Recently, it was shown that a significant number of erythromycin-resistant Streptococcus pneumoniae and Streptococcus pyogenes strains contain a determinant that mediates resistance via a putative efflux pump. The gene encoding the erythromycin-resistant determinant was cloned and sequenced from three strains of S. pneumoniae bearing the M phenotype (macrolide resistant but clindamycin and streptogramin B susceptible). The DNA sequences of mefE were nearly identical, with only 2-nucleotide differences between genes from any two strains. When the mefE sequences were compared to the mefA sequence from S. pyogenes, the two genes were found to be closely related (90% identity). Strains of S. pneumoniae were constructed to confirm that mefE is necessary to confer erythromycin resistance and to explore the substrate specificity of the pump; no substrates other than 14- and 15-membered macrolides were identified.

Detection of erythromycin-resistant determinants by PCR

Erythromycin resistance determinants include Erm methylases, efflux pumps, and inactivating enzymes. To distinguish the different mechanisms of resistance in clinical isolates, PCR primers were designed so that amplification of the partial gene products could be detected in multiplex PCRs. This methodology enables the direct sequencing of amplified PCR products that can be used to compare resistance determinants in clinical strains. Further, this methodology could be useful in surveillance studies of erythromycin-resistant determinants.

Glycylcyclines bind to the high-affinity tetracycline ribosomal binding site and evade Tet(M)- and Tet(O)-mediated ribosomal protection

N,N-dimethylglycylamido (DMG) derivatives of 6-demethyl-6-deoxytetracycline and doxycycline bind 5-fold more effectively than tetracycline to the tetracycline high-affinity binding site on the Escherichia coli 70S ribosome, which correlates with a 10-fold increase in potency for inhibition of E. coli cell-free translation. The potencies of DMG-doxycycline and DMG-6-demethyl-6-deoxytetracycline were unaffected by the ribosomal tetracycline resistance factors Tet(M) and Tet(O) in cell-free translation assays and whole-cell bioassays with a conditional Tet(M)-producing E. coli strain.

Streptococcus pneumoniae and Streptococcus pyogenes resistant to macrolides but sensitive to clindamycin: a common resistance pattern mediated by an efflux system

Macrolide-resistant Streptococcus pyogenes isolates from Finland, Australia, and the United Kingdom and, more recently, Streptococcus pneumoniae and S. pyogenes strains from the United States were shown to have an unusual resistance pattern to macrolides, lincosamides, and streptogramin B antibiotics. This pattern, referred to as M resistance, consists of susceptibility to clindamycin and streptogramin B antibiotics but resistance to 14- and 15-membered macrolides. An evaluation of the macrolide-lincosamide-streptogramin B resistance phenotypes among our streptococcal strains collected from 1993 to 1995 suggested that this unusual resistance pattern is not rare. Eighty-five percent (n = 66) of the S. pneumoniae and 75% (n = 28) of the S. pyogenes strains in our collection had an M phenotype. The mechanism of M resistance was not mediated by target modification, as isolated ribosomes from a pneumococcal strain bearing the M phenotype were fully sensitive to erythromycin. Further, the presence of an erm methylase was excluded with primers specific for an erm consensus sequence. However, results of studies that determined the uptake and incorporation of radiolabeled erythromycin into cells were consistent with the presence of a macrolide efflux determinant. The putative efflux determinant in streptococci seems to be distinct from the multicomponent macrolide efflux system in coagulase-negative staphylococci. The recognition of the prevalence of the M phenotype in streptococci has implications for sensitivity testing and may have an impact on the choice of antibiotic therapy in clinical practice.

Clinical strain of Staphylococcus aureus inactivates and causes efflux of macrolides

Searching through a collection of 124 Staphylococcus aureus clinical strains, we found one isolate, strain 01A1032, that inactivates 14- and 16-membered macrolides. The products of inactivation were purified from supernatant fluids of cultures exposed to erythromycin for 3 h and were found to be identical to products of inactivation from Escherichia coli strains that encode either an EreA or EreB esterase. Further, strain 01A1032 was shown to be resistant to azithromycin, a 15-membered macrolide, by an alternate mechanism, efflux. Thus, strain 01A1032 harbors determinants encoding an esterase activity that hydrolyzes 14- and 16-membered macrolides and a macrolide efflux system.

Doctors, nurses, and training in the administration of intravenous drugs

To assess the knowledge of staff and the effect of formal training on house officers we conducted telephone questionnaires of 40 house officers and 18 nurses. The following points were assessed: knowledge of dilution of drugs; knowledge of the rate at which drugs should be given; and the rate at which drugs were given. Appropriately trained nurses had greater knowledge than 'untrained' house officers. In all, 17/18 (94%) nurses compared with 9/18 (50%) house officers knew the correct rate at which to give ampicillin (P = 0.0036, Fisher's exact test); 14/18 (78%) nurses and 1/18 (6%) house officers said they gave ampicillin at the correct rate (P < 0.001); 13/18 (72%) nurses and 7/18 (39%) house officers said they gave ranitidine at the correct rate (P = 0.037). Only 1 of the 10 house officers who knew how rapidly to administer ampicillin said they took the correct length of time; 6 of the 10 who knew how rapidly to give ranitidine said they gave it at the correct rate. Training improves the knowledge of house officers, but other factors besides lack of knowledge (possibly lack of time) adversely affect delivery of intravenous drugs.

No more 'routine' chest radiographs in patients with proximal femoral fractures?

The proportion of abnormal chest radiographs in patients admitted following a femoral neck fracture was assessed. Significant abnormalities were found in 14%. In all these cases chest radiography was indicated. No abnormality was unexpected clinically.

Dehydration: burden or benefit to the dying patient?

Significant numbers of patients die each year from malignant disease. The question of whether or not to administer artificial hydration therapy to the patient who is in the last few days of life has been discussed for some time. Some health care professionals contend that a reduced fluid intake, which often accompanies the dying process, may result in a potentially painful and distressing state of dehydration, requiring preventative measures of fluid replacement therapy. In contrast, other clinicians suggest that artificial hydration is often of no proven benefit in the context of the dying and may impose additional physical and psychological burdens on the patient. This paper investigates the advantages and disadvantages of artificial hydration therapies in terms of the symptom distress experienced by the terminally ill cancer patient. Its aim is to promote discussion about this vital aspect of patient care.

A comparison of four commercial systems used to measure whole-body electrical impedance

Four commercial whole-body impedance measuring systems (Holtain, RJL, Bodystat and EZcomp) were compared on two separate occasions for a group of normal subjects. The first set of readings in 21 subjects demonstrated a significant difference of approximately 6% between the Holtain measurement and the higher readings from the Bodystat or RJL systems. The differences between the RJL and Bodystat readings were much less (mean difference 0.6%). Similar differences between the Holtain and EZcomp or Bodystat measurements were demonstrated on a second occasion for a group of 11 subjects. Given that these devices operate by supplying a constant current, the differences may be explained by the results from a series of measurements on a whole-body resistance simulator in which it appears that for skin contact resistance > 200 omega the Holtain device is unable to sustain a constant current and therefore records a lower impedance than the true value.

Quality of life: verification and use of a self-assessment scale in two patient populations

The study described further evaluates the use of the Holmes & Dickerson linear analogue self-assessment scale in assessing the quality of life of both in-patients and out-patients undergoing radiotherapy for the treatment of malignant disease. The scale is shown to be feasible for use in both clinical settings and to be both reliable and valid. It is quick to use, easy to score and demonstrates marked differences between the patient populations. These differences are discussed and supported on clinical grounds. The results emphasize the fact that cancer patients cannot be regarded as a homogeneous group and highlight the need for care to be planned on an individual basis. Similarly, the need for a means by which individual response can be assessed is demonstrated. It is suggested that this self-assessment technique may be of considerable value in such assessment.

Traumatically intruded permanent incisors: a study of treatment and outcome

Twenty-nine traumatically intruded permanent maxillary incisors from 20 patients were examined, treated and monitored for 2 years. There was a higher proportion of males than females. The teeth intruded furthest were more frequently extracted. Those which were surgically repositioned were more frequently retained and were associated with marginal bone loss significantly less frequently than those which were passively observed, while external root resorption occurred in similar proportions in both groups. A significantly higher proportion of those teeth that were delayed in presentation were subsequently extracted, and a similar trend was found for those with immature roots at the time of the initial examination.

Isotope computed tomography using cone-beam geometry: a comparison of two reconstruction algorithms

A CT scanner has been constructed specifically to determine the three-dimensional distribution of bone mineral in the medullary cavities of the radius, ulna and femur. A source of x-rays (153Gd) and a multiwire proportional counter (MWPC) are mounted at opposite ends of a diameter of an annular mounting. The limb is placed on the axis of rotation of the annulus and a series of two-dimensional transmission projections are obtained at equal angular spacings over 360 degrees. The distribution of bone mineral is reconstructed from the projections either by the method of maximum entropy (ME) or by convolution and back projection (CBP). These two methods have been evaluated by reconstructing a single slice of a phantom, representing the forearm, from projections simulated by computer. With a clinically acceptable exposure time, the mean medullary densities of the ulna and radius were determined with systematic errors of less than 3.5% (ME) and 11% (CBP), although for the latter method of reconstruction the systematic error was reduced to less than 2% by increasing the number of views. The mean medullary densities of the ulna and radius were determined with precisions better than 2.5% (ME) and 3.5% (CBP).

Tomographic reconstruction from experimentally obtained cone-beam projections

Direct reconstruction in three dimensions for two-dimensional projection data has been achieved by cone-beam reconstruction techniques. In this paper explicit formulas for a cone-beam convolution and back-projection reconstruction algorithm are given in a form which can be easily coded for a computer. The algorithm is justified by analyzing tomographic reconstructions of a uniformly attenuating sphere from simulated noisy projection data. A particular feature of this algorithm is the use of a one-dimensional rather than two-dimensional convolution function, greatly speeding up the reconstruction. The technique is applicable however large the cone angle of data capture and correctly reduces to the pure fan-beam reconstruction technique in the central section of the cone. The method has been applied to data captured on a cone-beam CT scanner designed for bone mineral densitometry.

Escherichia coli outer membrane protein K is a porin

Protein K is an outer membrane protein found in pathogenic encapsulated strains of Escherichia coli. We present evidence here that protein K is structurally and functionally related to the E. coli K-12 porin proteins (OmpF, OmpC, and PhoE). Protein K was found to cross-react with antibody to OmpF protein and to share 8 out of 17 peptides in common with the OmpF protein. Strains that are OmpC porin- and OmpF porin- and contain protein K as their major outer membrane protein have increased rates of uptake of nutrients and a faster growth rate relative to the parental porin- strain. The protein K-containing strains are at least 1,000-fold more sensitive to colicins E2 and E3 than is the porin -deficient strain. These data suggest that protein K is a functional porin in E. coli. The porin function of protein K was also demonstrated in vitro, using black lipid membranes. Protein K increased the conductance in these membranes in discrete, uniform steps characteristic of channels with a size of about 2 nS.

Shwachman's syndrome. A review of 21 cases

21 patients (10 male, 11 female) aged between 11 months and 29 years with Shwachman's syndrome are reviewed. All patients had exocrine pancreatic insufficiency. Haematological features included neutropenia in 19 (95%), anaemia in 10 (50%), and thrombocytopenia in 14 (70%); one patient developed erythroleukaemia. Severe infections occurred in 17 (85%) from which 3 (15%) died. Only one child exceeded the 3rd centile for height, and growth retardation was particularly evident in the older patients. All had skeletal abnormalities or delayed skeletal maturation, or both. Metaphyseal dyschondroplasia affected 13 of the older patients and was associated with skeletal deformities. Eight of 9 children under 2 1/2 years had rib abnormalities. Respiratory function tests in children under 2 years demonstrated reduced thoracic gas volume and chest wall compliance. Older patients had reduced forced expiratory volume and forced vital capacity. Neurological assessment showed developmental retardation or reduced IQ assessments, or both, in 85% of patients studied. Other neurological abnormalities included hypotonia, deafness, and retinitis pigmentosa. Neonatal problems had been present in 16 (80%) of the patients and 5 were of low birthweights. Hepatomegaly with biochemical evidence of liver involvement occurred in the younger patients and resolved with age. Other associated features included dental abnormalities, renal dysfunction, an icthyotic maculopapular rash in 13 (65%), delayed puberty, diabetes mellitus, and various dysmorphic features. These findings stress the diverse manifestations of the syndrome and extend knowledge on a number of aspects. Sibship segregation ratios support an autosomal mode of inheritance and an hypothesis for the pathophysiological basis of this syndrome is advanced.

Thenar hypoplasia with associated radiologic abnormalities

We report on five patients who presented with unilateral or bilateral hypoplasia of the thenar eminence. X rays of the affected limbs showed varying degrees of malformation and underdevelopment of the thumb phalanges and first metacarpal bone, and of the carpal bones at the base of the thumb, indicating a developmental abnormality. Our electrodiagnostic findings were compatible with this interpretation. We suggest that this condition is part of the clinical spectrum of radial club hand (radial dysplasia) and that when seen in adults, its recognition is important in the differential diagnosis of carpal tunnel syndrome.

Hypophosphatasia. Review of 24 cases

Radiographic analysis of 24 cases of hypophosphatasia (H) from 9 Paediatric Centres was performed. 3 cases were of neonatal (lethal), 18 cases of infantile (severe) and 3 cases of late (benign) type. Some of the patients were in reality borderline cases between these groups. In the authors' material all the patients showed radiographic signs of the disease. These were divided into diagnostic, characteristic and suggestive features. All of the patients had in common generalised (usually irregular) osteoporosis, generalised (usually irregular) metaphyseal changes, craniostenosis (13 of 18 infantile cases) or widened cranial sutures and ofter bowing of the long bones. Besides the well know radiographic features of hypophosphatasia some less well known, rare or 'new' ones such as, 1. spurs of the long bones (Bowdler sign), 2. distal femoral central metaphyseal defects and epiphyseal defects, 3. S-like deformities of the tibiae, 4. abnormal shape of the distal phalanges of the fingers, 5. multiple rib fractures and slender bones, 6. wedging of the lower thoracic and upper lumbar vertebrae, 7. partial premature fusion of the epiphyses, 8. nephrocalcinosis, 9. loss of lamina dura around the teeth, 10. variation in radiographic appearances of a pair of siblings with lethal form, and, 11. rapid changes in roentgen appearances. are discussed. In two of our patients (siblings) phosphoethanolamine was undetectable in the urine. The authors doubt if a normal skeletal survey may be present at any stage in any of the three major types of hypophosphatasia.