Hypophosphataemia in Septicaemia: Higher Incidence in Gram-negative Than in Gram-positive Infections

Phosphataemia has been investigated in 54 patients with Gram-negative septicaemias; either absolute (serum phosphate <2 mg./100 ml.) or relative (P./B.U.N. 0·04) hypophosphataemia was found in 69% of all determinations. In 37 patients with Gram-positive septicaemias hypophosphataemia was present in only 24%, many of whom had additional Gram-negative bacteriuria and possible Gram-negative septicaemia suppressed by antibiotics. The mechanism of this phenomenon is not known. This new sign of Gram-negative septicaemia has some diagnostic importance.     

Polymethyl-methacrylate-sorbitol-based capsules as local drug delivery vehicles: an in vitro antibiotic elution study

A PMMA (polymethyl-methacrylate)-sorbitol-based capsule system was recently developed, and the permeability of 16 types of capsules with different wall thicknesses and sorbitol contents tested. By optimizing these two parameters, we showed that capsule permeability could be controlled. Promising preliminary data obtained using BPB (Bromophenol Blue) as diffusion marker prompted us to further investigate the antibiotic release of capsules showing the most appropriate release characteristics. PMMA-sorbitol capsules were prepared with wall thickness of 0.5 or 0.6 mm and 60 or 70 w/w% (weight percent) of sorbitol content. In vitro gentamicin, amikacin, tobramycin releases were determined by using a microbiological agar plate diffusion assay. Capsules released 70-100% of their gentamicin load, substantially superior to Septopal, and showed preferable, extended release profiles when compared with the beads. The release kinetics of amikacin and tobramycin closely resembled those of gentamicin. PMMA-sorbitol capsules have been developed and tested, which make them promising devices for local antibiotic delivery.     

广州地区儿童血培养病原菌的分布及耐药性研究

目的探讨儿童血培养病原菌的分布特点及其耐药情况,为临床诊疗提供参考。方法对广州市儿童医院2005年至2006年临床各科室送检血液标本所分离病原菌的分布及药敏结果进行回顾性分析。结果共检出385株病原菌,其中革兰阳性菌208株,占54．0％,革兰阴性菌164株,占42．6％,真菌13株,占3．4％。分离率前6位的病原菌依次为凝固酶阴性葡萄球菌（CNS,35．8％）、肺炎克雷伯菌（8．8％）、不动杆菌（5．5％）、大肠埃希菌（4．9％）、铜绿假单胞菌（4、7％）、金黄色葡萄球菌（4．4％）。病原菌的病区分布特点：儿科重症监护病房以不动杆菌等非发酵菌为主要分离菌（占41．7％）,新生儿重症监护病房以CNS为主（40．5％）,血液病区以肠杆菌科细菌为主（35．7％）,新生儿病房及传染病房均以CNS为主要分离菌。CNS对青霉素、氨苄西林、红霉素耐药率均超过80％,但对万古霉素、替考拉宁和阿米卡星敏感,MRCNS检出率达72.5％。肠杆菌科细菌对哌拉西林、氨苄西林、头孢噻肟及头孢哌酮的耐药率为50％～100％,但对亚胺培南、阿米卡星和诺氟沙星耐药率较低。不动杆菌对广谱青霉素、第3代头孢菌素、氨曲南及庆大霉素的耐药率较高而对亚胺培南、头孢哌酮／舒巴坦较为敏感。结论凝固酶阴性葡萄球菌是广州地区儿童败血症最主要的病原菌。不同病区检出病原菌种类有较大差异。根据病原菌种类及药敏结果合理应用抗菌药是有效控制感染和减少耐药菌株产生的重要手段。     

Antibiotic use optimization program in the largest Croatian university hospital--benefits of restrictions on unlimited antibiotic use

The aim of this study was to obtain the relevant information on antibiotic use in a 750-bed Croatian university hospital. The study has been designed as a 2-point prevalence interventional analysis. For each patient on antibiotic therapy, diagnosis, indication for treatment, antibiotic therapy, dosage and route of administration together with the results of microbiological studies (if available) were obtained. After the first prevalence analysis in 2001, a restriction on unlimited antibiotic use was introduced. The second analysis, performed in 2002, after restrictions on antibiotic use, revealed reductions in the rates of restricted release antibiotics and overall antibiotic use with decreases from 38.6% to 36.9% and 23.4% to 23.2% respectively (p = 0.87). The first survey showed that the 5 most often prescribed antibiotics in the therapy of bacterial infections were: gentamicin, other aminoglycosides, carbapenems, amoxycillin +clavulanate and vancomycin with proportions of 14.8%, 10.3%, 8.2%, 7% and 7% respectively. In the year 2002, the most prescribed antimicrobial drugs in the therapy of bacterial infections were: gentamicin, quinolones, vancomycin, carbapenems and cefuroxime with proportions of 18.6%, 11.4%, 9.7%, 9.3% and 8% respectively. A reduction in the proportions of doubtful antibiotic therapy, from 24.6% before the intervention, to 24.2% after the restrictions, accompanied by a 0.4% rise in the rates of indicated antibiotic therapy was also observed (p = 0.93). Our study shows that restrictions on formerly unlimited use of antimicrobials, even when leading to an improvement in their prescribing, do not necessarily cause rapid and significant reduction in the overall use of antibiotics or explicit positive financial effects.     

Optimizing breast pocket irrigation: an in vitro study and clinical implications

Subclinical infections have been implicated in the etiology of capsular contracture. Intraoperatively, breast pocket irrigation with povidone-iodine or other antibiotic solutions has been popularized; however, detrimental effects on wound healing for these agents have been reported and their efficacy against common organisms found around breast implants has not been studied. The purpose of this study was to compare the in vitro efficacy of serial dilutions of povidone-iodine and two double antibiotic solutions DAB-1 (gentamicin/polymyxin B) and DAB-2 (gentamicin/cefazolin), against organisms most commonly found around breast implants. In phase I trials, serial dilutions of povidone-iodine and DAB were combined 1:1 with cultures of five common organisms found around implants. In phase II, povidone-iodine was serially diluted in DAB-1 rather than saline. In phase III, povidone-iodine was serially diluted with DAB-2. Efficacy for all phases was determined by plating the mixture onto agar plates and incubating at 37 degrees C for 48 hours. Povidone-iodine was 100 percent effective at a dilution of 12.5% against Staphylococcus epidermidis and 25% against Staphylococcus aureus but relatively ineffective against Escherichia coli and Pseudomonas, DAB-1 was found to be ineffective against S. epidermidis but effective against S. aureus, Propionibacterium acnes, E. coli, and Pseudomonas. In phase II trials, a concentration of 12.5% povidone-iodine in DAB was effective at killing all experimental bacteria. In phase III trials, 10% povidone-iodine in DAB-2 was effective at killing all bacteria tested. In conclusion, to maximize bacterial control of common breast implant organisms and to minimize the detrimental effects on wound healing, 10% povidone-iodine in gentamycin/cefazolin may be used with excellent results and its use clinically may reduce the incidence of capsular contracture.     

Kiwifruit ameliorates gentamicin induced histological and histochemical alterations in the kidney of albino mice

Gentamicin is an antibiotic used worldwide for treating Gram-negative bacterial infections. Gentamicin causes nephrotoxicity in up to 25% of therapeutic cases owing to increased production of free radicals. Kiwifruit are nutrient-dense fruits that have proven effective for ameliorating many pathological conditions caused by oxidative stress. We investigated the possible prophylactic and therapeutic effects of kiwifruit on the changes in renal histology and histochemistry caused by gentamicin. Intramuscular injection of mice with gentamicin for 10 consecutive days was nephrotoxic as indicated by epithelial vacuolization, glomerular atrophy and tubular necrosis. Necrotic tubule cells lost most of their polysaccharides and structural proteins. Co-administration of kiwifruit with gentamicin prevented nephrotoxic changes to a modest degree. When administered subsequent to gentamicin intoxication, kiwifruit ameliorated significantly the histological and histochemical alterations caused by gentamicin. Our findings support the use of kiwifruit in cases of acute renal injury due to gentamicin.     

Potent In Vitro Bactericidal Activity of Polymyxin B against Methicillin-Resistant Staphylococcus aureus (MRSA)

Eradication of methicillin-resistant Staphylococcus aureus (MRSA) carried by inpatients or healthy hospital personnel by topical use of antibiotics is an important step for preventing outbreak of MRSA nosocomial infection. In the screening of the antibiotic best suited for this purpose, we have found that polymyxin B, a commonly used antibiotic for gram-negative infection, had an unexpected strong cytokilling activity towards MRSA clinical strains, which was more potent than that of vancomycin or gentamicin. The data suggested that polymyxin B could be an antibiotic of choice in the treatment of topical carriage of or infection caused by MRSA.     

Experience in Monitoring Gentamicin Therapy during Treatment of Serious Gram-Negative Sepsis

This paper reports our experience in monitoring gentamicin therapy during the treatment of 68 episodes of serious Gram-negative sepsis in 65 hospital patients. Most of the patients had major underlying disease. Of those who were adequately treated (peak serum concentrations of 5 μg/ml or more in 72 hours for septicaemia, urinary tract infection, and wound infection; and 8 μg/ml or more at some time during the course of treatment for pneumonia) 84% (46 out of 55) were cured. These serum concentrations could be achieved only by starting with a regimen of 5 mg/kg/day in three divided doses in all adult patients, subsequent dosage being determined by the results of rapid serum assay. The incidence of nephrotoxicity and symptomatic ototoxicity was no greater than in previous series. The main reason for assaying serum gentamicin is to ensure that an adequate dosage is achieved as soon as possible. In patients with impaired renal function or receiving prolonged high dosage assays also serve to guard against an excessive accumulation of gentamicin and an increased risk of toxicity.     

Phenotypic switching of antibiotic resistance circumvents permanent costs in Staphylococcus aureus.

Bacterial antibiotic resistance is often associated with a fitness cost in the absence of the antibiotic [1,2]. We have examined a resistance mechanism in Staphylococcus aureus that negates these costs. Exposure to gentamicin both in vitro and in vivo has been reported to result in the emergence of a gentamicin-resistant small colony variant (SCV)[3-8]. We show that the emergence of SCVs following exposure to gentamicin results from a rapid switch and that bacteria exposed to cycles of gentamicin followed by antibiotic-free medium repeatedly switched between a resistant SCV and a sensitive parental phenotype (revertants). The fitness of revertants relative to S. aureus with stable gentamicin resistance was greater in drug-free media, which suggests that S. aureus has evolved an inducible and reversible resistance mechanism that circumvents a permanent cost to fitness.     

Effects of gentamicin sulfate on the contractility of myometrium isolated from non-pregnant cows

Gentamicin sulfate, an aminoglycoside antibiotic known to cause depression of neuromuscular function, is a drug of choice in intrauterine antibiotic treatment of bovine chronical or subclinical uterine infections but its effects on the contractility of the cow uterus have not been studied. The aim of this study was to characterize, in vitro, the effect of gentamicin sulfate on spontaneous as well as prostaglandin F2alpha (PGF2alpha) and oxytocin-induced contractility of the non-pregnant cow uterus. Myometrial strips were isolated from non-pregnant cows in follicular phase and suspended in a jacketed organ bath filled with Krebs solution at 37 degrees C (pH 7.4) continuously bubbled with 95% oxygen and 5% carbon dioxide and isometric contractions were recorded using isometric force displacement transducer. After manifestation of the spontaneous contractions during equilibration period the test substances PGF2alpha (1 microM), oxytocin (2.5 mIU/ml bath fluid) and gentamicin sulfate (150-600 microm) were added to the bath. The effects of gentamicin sulfate on amplitude (g) and frequency of spontaneous and the agonist-induced contractions were evaluated by 20 min intervals. Data were statistically analyzed using the Student's t-test and Wilcoxon signed-rank test where appropriate. P <0.05 was considered to be significant. Gentamicin sulfate inhibited spontaneous, as well as oxytocin or PGF2alpha-induced contractions in a dose-dependent manner. Although both the frequency and amplitude of contractions were significantly inhibited by gentamicin sulfate, the effect on the frequency of the spontaneous and agonist-induced contractions were more prominent than on the amplitude. The result from this in vitro study indicated that gentamicin sulfate inhibits spontaneous as well as oxytocin and PGF2alpha-induced contractions of myometrium isolated from non-pregnant cows. This may be of importance considering the potentially negative effect of gentamicin sulfate on uterine involution in cows with puerperal endometritis, resulting in impairment of fertility performance.     

Targeting of Antibiotics in Bacterial Infections Using Pegylated Long-Circulating Liposomes

Abstract

PEGylated long-circulating liposomes were used as a delivery system of antibiotics providing enhancements in antibiotic pharmacokinetics and penetration to infected sites. Pharmacokinetic and therapeutic efficacy studies were performed in the model of unilateral pneumonia/septicemia caused by Klebsiella pneumoniae in rats with intact host defense or leukopenic rats. Gentamicin was encapsulated in PEGylated liposomes designed to achieve delivery of antibiotic to the infected left lung tissue. Our data show that the efficacy of liposomal gentamicin was superior to free gentamicin particularly in difficult to treat infection due to impaired host defense (leukopenia) or low antibiotic susceptibility of the infectious organism. In leukopenic rats infected with a high gentamicin-susceptible bacterial strain, free gentamicin must be administered at the maximum tolerated dose to be therapeutically effective. The addition of a single dose of liposome-encapsulated gentamicin on the first day of treatment with free gentamicin leads to full therapeutic efficacy while keeping the antibiotic doses low. In even more difficult to treat infection due to both an impaired host defense (leukopenia) and low gentamicin-susceptibility of the bacterial strain, free gentamicin is not effective, and the addition of the liposome-encapsulated form of gentamicin is needed to achieve full therapeutic efficacy. In this respect, the lipid composition of the liposomes is an important determinant in establishing both sufficient antibiotic levels in blood and sufficient release of antibiotic from the liposomes at the infectious focus.

Ciprofloxacin was encapsulated in PEGylated liposomes designed to serve as a microreservoir of antibiotic during circulation in blood. Our data show that the administration of ciprofloxacin in the liposomal form resulted in slow release of ciprofloxacin from the liposomes over time in blood. Delayed ciprofloxacin clearance, as well as increased and prolonged ciprofloxacin concentrations in blood and tissues was observed. The therapeutic efficacy of liposomal ciprofloxacin was superior to that of free ciprofloxacin. PEGylated liposomal ciprofloxacin was well tolerated in relatively high doses (increasing the maximum tolerated dose for free ciprofloxacin), permitting the administration on a once-a-day schedule without loss in therapeutic efficacy.     

Optimal Combination and Concentration of Antibiotics in Media for Isolation of Pathogenic Fungi and Nocardia asteroides

Strains of Blastomyces dermatitidis, Sporothrix schenckii, Histoplasma capsulatum, Cryptococcus neoformans, Nocardia asteroides, and Coccidioides immitis were tested for in vitro susceptibility to polymyxin, gentamicin, kanamycin, chloramphenicol, and neomycin at concentrations of 1, 2, 4, 8, and 16 mug/ml. Polymyxin was the most inhibitory and gentamicin was the least inhibitory of the five antibiotics. Two Histoplasma mycelial strains were partially inhibited by 2 and 8 mug of gentamicin per ml and showed at least a 2+ growth at the higher antibiotic concentration. Kanamycin and neomycin produced significant inhibition of N. asteroides but otherwise were noninhibitory. A combination of chloramphenicol and kanamycin, each at 16 mug/ml, and gentamicin, at 4 mug/ml, was noninhibitory to the strains tested except for N. asteroides. Chloramphenicol at 16 mug/ml was not inhibitory for N. asteroides. The results suggest that the optimal antibiotic combination to use in the isolation of fungi and higher bacteria is chloramphenicol, 16 mug/ml, and gentamicin, 4 mug/ml. Addition of sheep blood (5%) had no effect on antibiotic susceptibility of the organisms studied.     

Rapid and quantitative detection of blood Serratia marcescens by a real-time PCR assay: its clinical application and evaluation in a mouse infection model

Large-scale nosocomial outbreaks of Serratia marcescens septicaemia in Japan have had a fatality rate of 20-60% within 48 h. As a countermeasure, a real-time PCR assay was constructed for the rapid diagnosis of S. marcescens septicaemia. This assay indeed detected S. marcescens in clinical blood specimens (at ca. 10(2)CFU ml(-1)), at a frequency of 0.5% in suspected cases of septicaemia. In mice, the assay provided estimates of blood S. marcescens levels at various infectious stages: namely, 10(7) to 10(8)CFU ml(-1) at a fatal stage (resulting in 100% death), 10(4)-10(5)CFU ml(-1) at a moderately fatal stage (resulting in 50% or more death), and <10(3)CFU ml(-1) at a mild stage (resulting in 100% survival), consistent with actual CFU measurements. Blood bacterial levels could be an important clinical marker that reflects the severity of septicaemia. The simultaneous detection of S. marcescens and the carbapenem resistance gene was also demonstrated.     

Resistance of urinary tract infection pathogens and choice of antibacterial therapy in pediatric urologic practice]

The data on antibiotic resistance of the main uropathogens isolated from patients with urinary tract infection in an urologic department (319 isolates) and outpatient and diagnostic units (360 isolates) are presented. It was shown that by the antibiotic resistance the Escherichia coli isolates from the urologic department patients and outpatients did not practically differ: 44.1 and 47.8% of the isolates were resistant to ampicillin, 26.7 and 23.4% were resistant to amoxycillin/clavulanate, 28.9 and 24.9% were resistant to co-trimoxazole and 26.5% was resistance to cefuroxime (outpatients). The basic differences referred to Pseudomonas aeruginosa: resistance to ceftazidime in 38.5% of the isolates and resistance to gentamicin in 36.2% of the isolates. The activity against P. aeruginosa could be arranged as follows in the decreasing order: amikacin = meropenem > imipenem > cefepime = cefoperazone/sulbactam > gentamicin = ceftazidime. Resistance of P. aeruginosa to fluoroquinolones (ciprofloxacin and levofloxacin) remained low (7.4 and 8.0% respectively). No ampicillin resistance was revealed in the isolates of Enterococcus faecalis.     

Action of aminoglycosides on platelet aggregation in vitro

The authors tested the influence of gentamicin, spectinomycin dihydrostreptomycin on the ADP and epinephrine in vitro induced platelet aggregation. Our aim was to demonstrate if platelet aggregation in vitro had some influences by antibiotics. A reduction in platelet aggregability, strictly dependent from the used antibiotic dose was observed. We have studied platelet function thanks to Born's method, adding to PRP gradual therapeutics doses of antibiotics. The results showed a reduction of platelet function which was dose-depended, and, particularly, gentamicin seemed to be the most effective among aminoglycosides. An interference between these drugs and the ADP and epinephrine binding to specific platelet receptor sites is proposed.     

Medium-Dependent Activity of Gentamicin Sulfate Against Enterococci

Routine disc diffusion susceptibility tests (Bauer-Kirby technique), employing 5% sheep blood-Mueller-Hinton agar and 10-mug gentamicin sulfate discs, disclosed that a significant number of clinical enterococcal isolates were sensitive to the antibiotic, as also revealed by the agar dilution technique. With few exceptions, the isolates proved resistant to this antibiotic when tested for susceptibility in Brain Heart Infusion and Trypticase soy broth or agar. The addition of 5% sheep blood to Trypticase soy and Brain Heart Infusion agars resulted in markedly enhanced activity of the antibiotic, indicating medium-dependent activity of gentamicin against enterococci. Human serum and urine failed to support optimal growth of enterococci. Thus, it was not possible to correlate the activity of gentamicin in any of the media examined with that in serum or urine.     

On the interaction between heparin and some aminoglycoside antibiotics

An interaction between the aminoglycoside antibiotics and heparin wherein charge transfer complexes are formed has been investigated to determine the degree of inhibition of antibacterial function of the antibiotic in the complexed form.Minimum inhibitory concentration (MIC) values have been obtained for the action of the aminoclycoside antibiotics tobramycin, gentamicin, amikacin, kanamycin, and streptomycin, on a sensitive strain ofE. coli. Growth curves ofE. coli determined at concentrations of these antibiotics just below the MIC demonstrated significant lengthening of the lag phase relative to control growth curves generated in the absence of antibiotic. Heparin (1 U ml^–1 and 10 U ml^–1) had no effect on control growth curves; however, particularly at the higher concentration, it reduced the effect on the lag phase produced by the aminoglycoside antibiotics. Thus kanamycin, gentamicin, and tobramycin were most affected, while amikacin and streptomycin were least affected. The rank order of inhibition of antibiotic activity by interaction with heparin was in qualitative agreement with previously published figures for the degree of complexation between antibiotics and heparin.     

1-N-(S-3-amino-2-hydroxypropionyl) gentamicin B (Sch 21420): A collaborative in vitro susceptibility comparison with amikacin and gentamicin against 12,984 clinical bacterial isolates

Schering Compound Sch 21420 is an aminoglycoside with antibacterial activity similar to amikacin but with a potential for renal toxicity lower than that of gentamicin. The in vitro activity of Sch 21420, amikacin, and gentamicin was compared with 12,984 bacterial isolates from six clinical laboratories. Agar dilution and broth microdilution techniques were both used with comparable results. Against most of the Enterobacteriaceae, Sch 21420 had equal or only slightly greater activity than amikacin.Proteus species were generally more susceptible to amikacin and gentamicin. Gentamicin was more active against most isolates included in this study.Pseudomonas aeruginosa recovered in the different institutions showed marked variations in susceptibility to gentamicin; amikacin and Sch 21420 were effective against most gentamicin-resistant strains that produce inactivating enzymes: but all three drugs were ineffective against permeability mutants. If diminished renal- and ototoxicity are confirmed, Sch 21420 promises to be a welcome addition to the antibiotic armamentarium.     

Acridine orange as an indicator of bacterial susceptibility to gentamicin

We have studied the response of Escherichia coli NCTC10418 to gentamicin with flow cytometry. The susceptibility of individual bacterial cells to the antibiotic was assessed by differential staining using the metachromatic dye, acridine orange. Exponential phase cultures were exposed to the minimum bactericidal concentration of gentamicin and analysed at regular intervals over 90 min. Within 60 min of exposure to the drug, two sub-populations of organisms could be distinguished in cultures by their different acridine orange-associated fluorescence emissions of <550 nm and >550 nm. The number of bacteria exhibiting acridine orange-associated fluorescence at >550 nm corresponded to counts of colony forming units.     

Local antibiotic delivery with demineralized bone matrix

A method of care for these infected nonunions is prolonged intravenous systemic antibiotic treatment and implantation of methyl methacrylate antibiotic carrier beads to delivery high local doses of antibiotics. This method requires a second surgery to remove the beads once the infection has cleared. Recent studies have investigated the use of biodegradable materials that have been impregnated with antibiotics as tools to treat bone infections. In the present study, human demineralized bone matrix (DBM) was investigated for its ability to be loaded with an antibiotic. The data presented herein demonstrates that this osteoinductive and biodegradable material can be loaded with gentamicin and release clinically relevant levels of the drug for at least 13 days in vitro. This study also demonstrates that the antibiotic loaded onto the graft has no adverse effects on the osteoinductive nature of the DBM as measured in vitro and in vivo. This bone void filler may represent a promising option for local antibiotic delivery in orthopedic applications.