Infections of implantable cardioverter defibrillators: approach to management

Implantable cardioverter defibrillators are being used with increasing frequency for the treatment of life-threatening ventricular arrhythmias. Nevertheless, no guidelines exist for the management of infections of these devices. We report our experience with infections of these devices and review the English-language literature. In all cases, patients presented with local signs of generator infection; systemic signs of infection and bacteremia were often absent. Most infections are due to staphylococcus. Risk factors for the development of infection include placement of the device via median sternotomy during another cardiac surgical procedure, reoperation, and intercurrent infection at another site. Infections are most reliably treated with full explantation of the device and antibiotics. In rare cases, patients may respond to a combination of intravenous antibiotics and removal and replacement of only the generator.

Endovascular infection and septic arthritis caused by Gemella morbillorum

Streptococcus morbillorum was transferred to the genus Gemella in 1988. Infections caused by G. morbillorum are unusual. We report a case of endovascular infection and presumptive septic arthritis caused by G. morbillorum. Previous cases of infection caused by G. morbillorum and G. haemolysans are reviewed.

Pneumonia caused by Nocardia nova and Aspergillus fumigatus after cardiac transplantation

Nocardia nova, a newly established species of the Nocardia asteroides complex, has recently been characterized as a human pathogen. This report of a case of pneumonia caused by Nocardia nova and Aspergillus fumigatus in a patient after cardiac transplantation is the first reported infection caused by Nocardia nova following its detailed description. Accurate identification and susceptibility testing of the Nocardia nova isolate allowed successful oral therapy with clarithromycin when therapy with sulfisoxazole was not tolerated.

Cefuroxime versus cefazolin as prophylaxis in vascular surgery

Although cefazolin prophylaxis has proven efficacy in vascular surgery, Staphylococcus aureus wound infections are still an important postoperative complication. In cardiac surgery, cefazolin's susceptibility to hydrolysis by staphylococcal beta-lactamase has been proposed to account for some prophylaxis failures. To determine whether the incidence of vascular wound infections can be reduced by administering a more beta-lactamase-stable cephalosporin, we undertook a prospective, randomized trial of cefuroxime versus cefazolin. Cefuroxime was administered as a 1.5 gm dose before operation and 750 mg every 3 hours during operation. Cefazolin was given as 1 gm before operation and 500 mg every 4 hours during operation. Both agents were continued every 6 hours after operation for 24 hours. Deep wound infections developed in seven of 272 (2.6%) cefuroxime and three of 287 (1.0%) cefazolin recipients (p = 0.2). Staphylococcus aureus wound infections occurred in five cefuroxime versus two cefazolin recipients. In vitro evaluation of six of the study isolates plus an additional eight S. aureus strains from vascular wound infections showed greater susceptibility of the strains to cefazolin than cefuroxime (median minimal inhibitory concentrations of 0.5 and 2.0 micrograms/ml, respectively, p less than 0.05). Furthermore, despite its more frequent intraoperative redosing, cefuroxime exhibited lower trough serum concentrations than cefazolin. Among cefuroxime recipients, infection-associated procedures were significantly longer than infection-free procedures (p less than 0.05), suggesting that low tissue antibiotic concentrations may have contributed to the pathogenesis of these infections. In contrast, the length of the procedure was not a risk factor for infection among cefazolin recipients.(ABSTRACT TRUNCATED AT 250 WORDS)

Pneumonia and chronic obstructive pulmonary disease. What special considerations does this combination require?

Patients with chronic obstructive pulmonary disease are at increased risk for both community- and hospital-acquired pneumonia, most often through aspiration. Community-acquired pneumonia often manifests with acute onset of chills, fever, cough, and pleuritic chest pain. Atypical pneumonia syndromes are characterized by subacute onset over several days and constitutional complaints. Hospital-acquired pneumonia may be contracted during altered consciousness or after intubation, ventilation, or exposure to pathogens. Knowledge of the disease process and the means to accurately diagnose these infections allows physicians to prescribe effective antibiotic therapy. Stable patients may receive oral therapy, but with severe or hospital-acquired pneumonia, parenteral therapy is required. Combinations of agents may be needed to cover the variety of pathogens that may be present.

The role of interference and task similarity on the acquisition, retention, and transfer of simple motor skills

The aim of the present study was to determine if two levels of task similarity influenced acquisition, retention, and transfer performance of three simple motor skills. Sixty right-handed subjects were randomly assigned to one of five (n = 12) experimental conditions. Each subject performed 72 trials during acquisition. Twenty-four trials were recorded for each movement task. Following a 5-min unfilled retention interval, subjects performed 4 trials on each task before completing 12 transfer trials of a novel movement. Contextual interference effects for acquisition and retention were supported for low but not high similarity tasks. Further, the results suggest that a different memory representation exists for high and low similarity tasks.

Effects of normal and mutant ras genes on inositol lipid metabolism in Dictyostelium

Dictyostelium cells transformed with multiple copies of a mutant Dictyostelium ras gene (ras-Thr12 that gave a Gly to Thr substitution at position 12 of the ras protein, showed 2 to 3 times greater incorporation of 32P into PtdInsP and PtdInsP2 (without changing the specific radioactivity) compared to the untransformed strain or a strain transformed with multiple copies of the normal ras-Gly12 gene. The ratio of labelled PtdInsP2/PtdInsP, however, was not affected by the ras-Thr12 gene. Stimulation with the chemoattractant, cyclic AMP, caused a rapid but transient decrease in the levels of labelled PtdInsP and PtdInsP2 in the normal and ras-Gly12-transformed strains but ras-Thr12-transformed strains failed to respond. In untransformed cells a small, very rapid rise in the level of labelled PtdInsP and PtdInsP2 was seen immediately after stimulation of the cells with cyclic AMP (before the transient decrease) and this rise was greatly accentuated in cells transformed with multiple copies of the normal ras-Gly12 gene. Agents that induce prolonged activation of phosphoinositidase C such as AlF4- or GTPYS gave a lowered steady-state level of incorporation of 32P into PtdInsP and PtdInsP2 in all strains. The results indicate that the enzyme in the inositol phosphate pathway that is affected by the ras gene is not phosphoinositidase C, but is an enzyme before PtdInsP kinase, possibly PtdIns kinase.

Failure of treatment with teicoplanin at 6 milligrams/kilogram/day in patients with Staphylococcus aureus intravascular infection. The Infectious Diseases Consortium of Oregon

Patients with blood cultures positive for gram-positive cocci were enrolled in a prospective randomized double-blind comparative trial of vancomycin at 15 mg/kg every 12 h versus teicoplanin at 6 mg/kg every 12 h for three doses and then 6 mg/kg every 24 h. A total of 54 patients were randomized, and 40 were evaluable. Of the 40, 9 had infection of indwelling vascular catheters. Four infections were due to Staphylococcus aureus, and five were due to Staphylococcus epidermidis. In concert with catheter removal, all patients were treated successfully, regardless of which drug they were taking. Of 31 patients without an indwelling catheter, 19 were infected with S. aureus, and 12 of the 19 had either endocarditis or mycotic aneurysm. Six of eight patients given teicoplanin failed treatment, as opposed to one of four patients given vancomycin (P = 0.14). Of greater concern, four of four patients with left-sided endocarditis or mycotic aneurysm failed to recover when given teicoplanin, as opposed to one of three patients given vancomycin (P = 0.07). Although not quite statistically significant, the unexpectedly high number of treatment failures with teicoplanin resulted in a decision to discontinue patient enrollment. It is suggested that future trials explore the efficacy of larger doses of teicoplanin.

Signal transduction for chemotaxis in Dictyostelium amoebae

The signal for chemotaxis in D. discoideum is cyclic AMP. This molecule binds to cell surface receptors and triggers the production of inositol (1,4,5)trisphosphate which releases Ca2+ from non-mitochondrial stores. The subsequent chain of signal transduction events brings about the polymerization of cytoskeletal actin (associated with pseudopodium formation) within five seconds and the formation of a peak of cyclic GMP within 10 s. Evidence from streamer F mutants indicates that the cyclic GMP regulates the association of myosin with the cytoskeleton that occurs at 25-50 s and that this phenomenon is concerned with elongation of the amoebae during chemotactic movement.

The effect of acetylcholine on inositol lipid metabolism and intracellular calcium concentrations in bovine anterior pituitary cells

Acetylcholine (ACh) increased the intracellular calcium concentration in bovine anterior pituitary cells. In the presence of the calcium channel antagonists verapamil (20 microM) or nitrendepine (1 microM) the increase in calcium was partially inhibited but showed both transient and sustained components. In the presence of EGTA (2.5 mM) only the transient component was observed. ACh also decreased inositol radioactivity in phosphatidylinositides and increased it in inositol phosphates. It is concluded that the increase in calcium caused by acetylcholine requires both the entry of external calcium and mobilisation of internal calcium. Replacement of external sodium by N-methyl-D-glucamine inhibited the rises in calcium and inositol phosphate labelling in response to ACh. Tetrodotoxin (3 microM) or ouabain (50 microM) did not affect either response to ACh. Verapamil did not affect the calcium rise induced by ACh in the absence of external sodium. The phorbol ester PMA (10 nM) caused a transient rise in calcium and inhibited the calcium rise caused by acetylcholine: it did not modify the effect of acetylcholine on inositol phosphates. The dependence of the stimulation of external calcium entry and inositol phosphate production on external sodium ions and protein kinase C is discussed.

The effects of thyrotropin-releasing hormone and potassium depolarization on phosphoinositide metabolism and cytoplasmic calcium in bovine pituitary cells

Addition of thyrotropin-releasing hormone (TRH) (10 nM to 10 microM) to bovine anterior pituitary cells labelled with [3H]inositol decreased the radioactivity in inositol-containing lipids and increased it in inositol phosphates. TRH also increased the cytoplasmic calcium concentration biphasically. At TRH concentrations below 10 nM, the increase was sustained and sensitive to inhibitors of calcium influx through voltage-gated channels, whereas concentrations over 10 nM elicited in addition a rapid transient increase in calcium, which was relatively insensitive to such inhibition. Incubation of the cells in medium containing 25 mM KCl increased the cytoplasmic calcium concentration by stimulating influx through voltage-gated channels, and markedly enhanced the initial transient increase of calcium seen at TRH concentrations above 10 nM. It did not affect the generation of InsP3 and it also enhanced the calcium response to ionomycin. It is suggested that stimulation of calcium entry through voltage-gated channels can increase the amount of calcium available for mobilisation by TRH.

Inositol tris- and polyphosphate formation during chemotaxis of Dictyostelium

Using the technique of HPLC with Partisil SAX columns, we have found that stimulation of amoebae of Dictyostelium discoideum with the chemoattractant cyclic AMP induces the rapid accumulation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), with a peak at 5 s. A smaller HPLC peak (designated P3) that elutes just after the Ins(1,4,5)P3 peak accumulates more slowly to a maximum at 20 s. In control studies, the changes in Ins(1,4,5)P3 were shown not to be due to varying recovery from the cell extracts and a comparison of reverse-phase and Partisil SAX HPLC columns showed similar values for determinations by either method. The involvement of a G-protein in this chemotactic system was confirmed by the finding that accumulation of Ins(1,4,5)P3 was elicited by the addition of GTP gamma S (5′-[gamma-thio]triphosphate) to saponin-permeabilized amoebae. A study of the changes in the lipid-soluble phosphatidyl inositol phosphates demonstrated that cyclic AMP also stimulated a rapid loss of radioactivity from 32P-labelled phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), which corresponded in its timing to the rise in Ins(1,4,5)P3, indicating that a phosphoinositidase C (phospholipase C) is present that can be stimulated by occupation of the cell surface cyclic AMP receptors.

Influence of daptomycin on staphylococcal abscesses and experimental tobramycin nephrotoxicity

The antibacterial efficacies of daptomycin and vancomycin were compared in male Fischer rats with subcutaneous abscesses caused by either methicillin-susceptible Staphylococcus aureus (MSSA) or methicillin-resistant S. aureus (MRSA). The influence of daptomycin on tobramycin nephrotoxicity was also assessed. MSSA or MRSA abscesses were treated with subcutaneous daptomycin (10 mg/kg every 12 h), vancomycin (125 mg/kg every 12 h), or diluent (every 12 h) for 5 to 10 days. Rats in both antibiotic treatment groups had lower abscess bacterial counts than did controls at days 5 and 10 (P less than 0.0025). The daptomycin treatment groups had lower abscess bacterial counts than did the vancomycin treatment groups for MSSA at day 5 (P less than 0.0025) and day 10 (P less than 0.025) and for MRSA at day 10 (P less than 0.0025). Nephrotoxicity treatment groups included animals treated for 3, 7, 10, 14, and 17 days with subcutaneous diluent (every 12 h), daptomycin (20 mg/kg every 12 h), tobramycin (40 mg/kg every 12 h), and the combination of daptomycin and tobramycin. Compared with controls, animals treated with daptomycin alone exhibited no detectable nephrotoxicity. Rats given tobramycin alone developed functional and histopathologic abnormalities from days 7 through 17. Animals treated with daptomycin and tobramycin for 14 days had a lower mean concentration of creatinine in serum (P less than 0.005), higher mean creatinine clearance values (P less than 0.05), and less cortical tubular cell regeneration (P less than 0.05) than did rats treated with tobramycin alone. In rats with staphylococcal subcutaneous abscesses, daptomycin was superior to vancomycin in treating both MSSA and MRSA. Daptomycin alone caused no detectable renal injury, and in rats given daptomycin combined with tombramycin, there was less histologic and functional renal injury than in animals given tobramycin alone.

Polyaspartic acid prevents experimental aminoglycoside nephrotoxicity

The influence of the polyamino acid polyaspartic acid (PAA) on experimental aminoglycoside nephrotoxicity was determined. PAA prevented all measured functional and pathologic evidence of gentamicin nephrotoxicity for less than or equal to 27 d of study. All the animals given PAA, either alone or with gentamicin, developed prominent cytoplasmic vacuoles in the cells of the renal proximal convoluted tubules; the vacuoles in rats given just PAA differed from those observed in rats given PAA plus gentamicin. Rats given PAA plus gentamicin accumulated roughly 10 times more renal aminoglycoside as did rats given gentamicin alone. Immunohistochemical localization studies confirmed the presence of increased amounts of gentamicin in the cytoplasm of the tubular cells of animals given gentamicin plus PAA. PAA did not alter the in vitro antimicrobial activity of gentamicin versus Escherichia coli or Pseudomonas aeruginosa. These studies demonstrate the ability of PAA to prevent experimental gentamicin nephrotoxicity.

Vertebral osteomyelitis and native valve endocarditis caused by Staphylococcus warneri

Coagulase-negative staphylococci almost invariably cause significant clinical infections in the setting of prosthetic devices or severely compromised host defenses. Hematogenous osteomyelitis and native valve endocarditis due to these pathogens in any setting is rare. We report a case of community-acquired vertebral osteomyelitis and native valve endocarditis due to Staphylococcus warneri in a patient with none of the usual risk factors.

The influence of tobramycin dosage regimens on nephrotoxicity, ototoxicity, and antibacterial efficacy in a rat model of subcutaneous abscess

The influence of dosage regimen on the nephrotoxicity, ototoxicity, and antibacterial efficacy of tobramycin was assessed in Fisher rats with Pseudomonas aeruginosa subcutaneous abscesses. A subcutaneous tobramycin dose of 10 mg/kg every 4 h resulted in peak and trough serum concentrations that approximated those currently recommended for patients. Subsequently, the influence of this subcutaneous dosage regimen was compared with three other regimens that administered the same total daily dose: 20 mg every 8 h, 30 mg every 12 h, and 60 mg every 24 h. Renal injury was assessed by measuring inulin clearance and in vivo synthesis of renal DNA and by histopathology. Cochlear histology was also assessed. The number of P. aeruginosa per abscess was quantitated. In animals with infected abscesses, there was a consistent trend of greater kidney injury with the more-frequent dosage regimens. There was no evidence of cochlear toxicity in any group. All regimens were equally effective in reducing the number of P. aeruginosa in subcutaneous abscesses.

The relative predictive performance of two theophylline pharmacokinetic dosing programs

The predictive performance of 2 theophylline pharmacokinetic dosing programs (Abbott and Simkin) was evaluated using a group of 44 inpatients who had 2 serum concentrations (TSC) measured during hospitalization. Bias was assessed with the median prediction error (PE) and precision was assessed with the median absolute PE. The Abbott program was significantly less biased than the Simkin program in predicting the first TSC (PEs 0.1 and -1.3 micrograms/ml, respectively; p less than 0.05). No significant difference in bias was observed in predicting the second TSC, or in precision in predicting either the first or second TSC. Both programs exhibited small improvements in prediction precision when the first TSC was used to predict the second. Correlations of predicted versus measured TSC also improved with the second prediction. These programs may be useful in dosing theophylline; however, TSC monitoring and the application of sound clinical judgment are warranted.