Comparison of inherently essential genes of Porphyromonas gingivalis identified in two transposon-sequencing libraries.

Porphyromonas gingivalis is a Gram-negative anaerobe and keystone periodontal pathogen. A mariner transposon insertion mutant library has recently been used to define 463 genes as putatively essential for the in vitro growth of P. gingivalis ATCC 33277 in planktonic culture (Library 1). We have independently generated a transposon insertion mutant library (Library 2) for the same P. gingivalis strain and herein compare genes that are putatively essential for in vitro growth in complex media, as defined by both libraries. In all, 281 genes (61%) identified by Library 1 were common to Library 2. Many of these common genes are involved in fundamentally important metabolic pathways, notably pyrimidine cycling as well as lipopolysaccharide, peptidoglycan, pantothenate and coenzyme A biosynthesis, and nicotinate and nicotinamide metabolism. Also in common are genes encoding heat-shock protein homologues, sigma factors, enzymes with proteolytic activity, and the majority of sec-related protein export genes. In addition to facilitating a better understanding of critical physiological processes, transposon-sequencing technology has the potential to identify novel strategies for the control of P. gingivalis infections. Those genes defined as essential by two independently generated TnSeq mutant libraries are likely to represent particularly attractive therapeutic targets.

Mapping the Burkholderia cenocepacia niche response via high-throughput sequencing.

Determining how an organism responds to its environment by altering gene expression is key to understanding its ecology. Here, we used RNA-seq to comprehensively and quantitatively assess the transcriptional response of the bacterial opportunistic cystic fibrosis (CF) pathogen and endemic soil dweller, Burkholderia cenocepacia, in conditions mimicking these 2 environments. By sequencing 762 million bases of cDNA from 2 closely related B. cenocepacia strains (one isolated from a CF patient and one from soil), we identified a number of potential virulence factors expressed under CF-like conditions, whereas genes whose protein products are involved in nitrogen scavenging and 2-component sensing were among those induced under soil-like conditions. Interestingly, 13 new putative noncoding RNAs were discovered using this technique, 12 of which are preferentially induced in the soil environment, suggesting that ncRNAs play an important role in survival in the soil. In addition, we detected a surprisingly large number of regulatory differences between the 2 strains, which may represent specific adaptations to the niches from which each strain was isolated, despite their high degree of DNA sequence similarity. Compared with the CF strain, the soil strain shows a stronger global gene expression response to its environment, which is consistent with the need for a more dynamic reaction to the heterogeneous conditions of soil.

Selected controversies in cardiopulmonary resuscitation.

Cardiopulmonary resuscitation (CPR) is performed frequently by paramedics, emergency department personnel, and inpatient physicians. Unfortunately, after more than 40 years of practice and study, there are still many controversies and unresolved treatment issues. This article focuses on four current controversies in CPR: (1) the role of end-tidal CO2 (ETCO2) detection, (2) the use of bicarbonate, (3) whether epinephrine is the optimal alpha agonist, and (4) whether amiodarone should replace lidocaine as the initial antiarrhythmic of choice in the treatment of ventricular fibrillation.

Essential role of BETA2/NeuroD1 in development of the vestibular and auditory systems.

BETA2/NeuroD1 is a bHLH transcription factor that is expressed during development in the mammalian pancreas and in many locations in the central and peripheral nervous systems. During inner ear ontogenesis, it is present in both sensory ganglion neurons and sensory epithelia. Although studies have shown that BETA2/NeuroD1 is important in the development of the hippocampal dentate gyrus and the cerebellum, its functions in the peripheral nervous system and in particular in the inner ear are unclear. Mice carrying a BETA2/NeuroD1 null mutation exhibit behavioral abnormalities suggestive of an inner ear defect, including lack of responsiveness to sound, hyperactivity, head tilting, and circling. Here we show that these defects can be explained by a severe reduction of sensory neurons in the cochlear-vestibular ganglion (CVG). A developmental study of CVG formation in the null demonstrates that BETA2/NeuroD1 does not play a primary role in the proliferation of neuroblast precursors or in their decision to become neuroblasts. Instead, the reduction in CVG neuron number is caused by a combination both of delayed or defective delamination of CVG neuroblast precursors from the otic vesicle epithelium and of enhanced apoptosis both in the otic epithelium and among those neurons that do delaminate to form the CVG. There are also defects in differentiation and patterning of the cochlear duct and sensory epithelium and loss of the dorsal cochlear nucleus. BETA2/NeuroD1 is, thus, the first gene to be shown to regulate neuronal and sensory cell development in both the cochlear and vestibular systems.

Protein-calorie malnutrition and involuntary weight loss: the role of aggressive nutritional intervention in wound healing.

Protein-calorie malnutrition and involuntary weight loss continue to be prevalent among hospitalized and long-term care patients, particularly the elderly. Studies on nutritional intervention have established a correlation between nutritional status, body weight, and rate of wound healing. Nutritional intervention, however, must be provided early enough to prevent a catabolic-induced decline in lean muscle mass, which can further impair wound healing. Chronic, nonhealing wounds are particularly difficult to treat and contribute to significant morbidity, mortality, and hospitalizations. More aggressive nutritional management and a greater understanding of the role of nutrition and weight gain in wound healing can result in more effective patient care. This article discusses the role of protein-calorie malnutrition and involuntary weight loss in hindering the wound-healing process, and the need to establish an optimal anabolic environment for weight gain and improved wound healing.

Nutritional supplements in the treatment of pressure ulcers: practical perspectives.

Because a pressure ulcer may be related to malnutrition, clinicians should assess patients' nutritional status and ensure that patients receive adequate nutrition to support healing. The Agency for Health Care Policy and Research's guideline Treatment of Pressure Ulcers outlines recommended calorie and protein levels for patients at risk for pressure ulcers and with pressure ulcers. This article focuses on practical aspects of providing adequate nutrition to patients with pressure ulcers, using a variety of products available for oral supplementation.

Absence of ototoxicity of teichomycin A2 in guinea pigs.

Teichomycin A2 is a new antibiotic that is similar to vancomycin. Because vancomycin is reported to be ototoxic, teichomycin A2 was tested for ototoxicity. No evidence of ototoxicity was found. Furthermore, ethacrynic acid, a diuretic that augments the ototoxicity of many drugs, did not enhance ototoxicity with teichomycin A2.

Dissociation of maximum concentration of kanamycin in plasma and perilymph from ototoxic effect.

Kanamycin was administered in total daily doses of 0 (vehicle), 100, 200 or 300 mg/kg to different groups of guinea pigs for two weeks. These total daily doses were administered according to three different dosing schedules, either as a single injection given once a day, divided into two equal doses and given twice a day, or divided into four equal doses and administered four times a day. It was found that the magnitude of the ototoxicity resulting from kanamycin administration was related to the total daily dose alone and not the dosing schedule. This lack of relationship between the dosing schedule and the magnitude of the ototoxicity due to kanamycin is the reverse of that reported for the nephrotoxicity resulting from gentamicin, tobramycin and netilmicin.

The ototoxic interaction of viomycin, capreomycin and polymyxin B with ethacrynic acid.

The ototoxic interaction between the aminoglycoside antibiotics (streptomycin, kanamycin, etc.) and the loop-inhibiting diuretics (ethacrynic acid, furosemide and bumetanide) has been well documented. This interaction causes extensive destruction of the hair cells of the cochlea. Brummett et al. (1974) demonstrated that this interaction did not occur with the non-loop-inhibiting diuretics and kanamycin. The present study was undertaken to determine if antibiotics other than the aminoglycosides could produce the ototoxic interaction when combined with a loop-inhibiting diuretic. Three antibiotics-viomycin, capreomycin, and polymyxin B- when given with ethacrynic acid were found to produce cochlear hair cell damage that was similar to that produced by aminoglycoside antibiotics administered with ethacrynic acid. Therefore, the interaction appears to be specific to the loop-inhibiting diuretics but not specific for the aminoglycoside antibiotics.

Comparative ototoxicity of bumetanide and furosemide when used in combination with kanamycin.

The ototoxicity of bumetanide and furosemide was compared in Topeka strain guinea pigs pretreated with kanamycin. The animals, anesthetized with pentobarbital, received a single dose of 400 mg/kg kanamycin subcutaneously and the diuretics via indwelling catheter in the jugular vein 2 hours later. Ototoxic drug effects were determined by measuring the electrophysiological responses of the cochlea to sound stimuli and by determining the presence or absence of cochlear sensory hair cells from the organ of Corti. Both bumetanide and furosemide produced permanent alteration of cochlear activity in the kanamycin-pretreated animals. The ototoxic effect of bumetanide is five times that of furosemide on a milligram-for-milligram basis. The ototoxic potential of bumetanide is one eighth that of furosemide when the doses are adjusted for diuretic potency difference between the two diuretics.

A comparative study of the ototoxicity of gentamicin and gentamicin C1.

Dose-response experiments comparing the ototoxic liability of the aminoglycoside antibiotics gentamicin sulfate and gentamicin C1 sulfate were conducted on guinea pigs. Measures of cochlear electrophysiology, histology, and the pharmacokinetic disposition of the drugs in the plasma and perilymph were made. Electrophysiological and histological measures indicated that gentamicin is more ototoxic than is gentamicin C1.

Quantitative relationships of the ototoxic interaction of kanamycin and ethacrynic acid.

We determined the range of doses of kanamycin sulfate and ethacrynic acid that results in an ototoxic interaction in guinea pigs. In addition, we determined the time interval between the administration of the two drugs that is needed to produce this interaction. In all cases, the magnitude of the ototoxic lesion was determined by measuring the cochlea's ability to generate both the sensitivity and intensity functions of the ac cochlear potential. In addition, the cochlear pathologic conditions, as determined by counting the number of missing hair cells in the organ of Corti, was found to correlate highly with the ac cochlear potential data. The dosage range of ethacrynic acid during which the interaction occurs is very narrow, while the dose range of kanamycin is very large.

Comparative ototoxic liability of netilmicin and gentamicin.

Netilmicin sulfate is a new aminoglycoside antibiotic currently undergoing clinical investigation. All of the aminoglycoside antibiotics now in clinical use are ototoxic. This study was done to determine the ototoxic liability of netilmicin when it is compared directly with gentamicin sulfate. Groups of ten guinea pigs each were given doses of 0, 50, 100, or 150 mg/kg of either gentamicin or netilmicin daily for four weeks. After a two-week stabilization period, the Preyer pinna reflex, the cochlea's ability to generate the ac cochlear potential, and the missing hair cells from the cochleas were determined. Additionally, the pharmacokinetics of both drugs in the plasma and perilymph were determined. Little or no cochlear damage was detected with netilmicin, even at the highest dose, while even the smallest dose of gentamicin produced measurable changes in cochlear function.

Cochlear damage resulting from kanamycin and furosemide.

Permanent cochlear damage has been shown to occur in guinea pigs following the combined administration of kanamycin and furosemide. At the doses used, only a transient effect was measured with furosemide alone and no effect was detectable with kanamycin alone. This interaction results when a single subcutaneous dose of 400 mg/kg of kanamycin is followed in 2 hours by a single intravenous dose of furosemide. The dosage range for furosemide was 50 mg/kg for a just-detectable effect to 100 mg/kg for a very severe effect. Damage to the cochlea was ascertained by measures of the a.c. cochlear potential as well as surface preparation histology.