Arbekacin - A Novel Antibiotic for Critical Infections

Antibiotic resistance is one of the biggest menace to global health. Deaths from Drug-resistant infections is set to escalate exponentially. Pipeline for new antibacterials is almost empty. The World Health Organization has reinforced its warning that to tackle growing threat of antimicrobial resistance, development of a new antibiotics is seriously lacking. Arbekacin is a novel aminoglycoside primarily used in the treatment of infections caused by resistant Staphylococcus Aureus i.e. Methicillin Resistant Staphylococcus Aureus (MRSA). Besides MRSA it also demonstrates activity against Enterococci and several Gram negative pathogens such as Klebsiella pneumonia, Pseudomonas aeruginosa, Acinetobacter baumannii including resistant strain. Arbekacin which has been used in Japan and Korea since more than two and half decades has been recently approved in India. This review will examine how Arbekacin evades the common mechanisms of antibiotic resistance, the pharmacokinetics of Arbekacin, and the various pharmacological properties and its spectrum of in vitro activity. The results of clinical trials on Arbekacin are also described, as is the patient safety and tolerability observed during these studies.

A Multicentre, Open label, Randomized, Comparative, Parallel Group, Active-controlled, Phase III Clinical Trial to Evaluate Safety and Efficacy of Arbekacin Sulphate Injection versus Vancomycin Injection in Patients Diagnosed with MRSA Infection

BACKGROUND

Increasing resistance to currently available antimicrobials has led to the development of new agents. Arbekacin is aminoglycoside antibiotic currently used in Japan and Korea for the treatment of infections caused by multi-resistant bacteria including MRSA. Currently there is no published data available for use of Arbekacin in Indian patient population, thus the present study was conducted to evaluate the safety and efficacy of Arbekacin in Indian population.

MATERIAL AND METHODS

The study was a phase III, multi-centre, open-label, randomised comparative, active control study. Subjects with microbiologically confirmed MRSA infection were randomized in the study to receive either Arbekacin sulphate 200 mg OD or Vancomycin hydrochloride 1000 mg BD for a period of 7 to 14 days. The primary endpoint was to evaluate the overall cure rate i.e. Clinical and microbiological cure during the study.

RESULTS

A total of 162 patients were randomized in 2 treatment groups (i.e. 81 patients in each group). Out of these microbiologically confirmed MRSA patients, 153 patients were admitted for SSTI while 9 patients were admitted for CAP. Overall cure rate of MRSA infection (clinical as well as microbiological cure) was comparable in both the treatment groups i.e. 97.5% (79/81) in Arbekacin group and 100 % (79/79) in Vancomycin group (p value: 0.159). Both Arbekacin and Vancomycin were well tolerated by the patients during the study period.

CONCLUSION

Arbekacin can be considered as safe and effective alternative to vancomycin in the management of MRSA infections.

[Genetic Diagnosis and Molecular Therapies for Duchenne Muscular Dystrophy]

Duchenne muscular dystrophy (DMD) is the most common form of inherited muscle disease and is characterized by progressive muscle wasting, ultimately resulting in the death of patients in their twenties or thirties. DMD is characterized by a deficiency of the muscle dystrophin as a result of mutations in the dystrophin gene. Currently, no effective treatment for DMD is available. Promising molecular therapies which are mutation-specific have been developed. Transformation of an out-of-frame mRNA into an in-frame dystrophin message by inducing exon skipping is considered one of the approaches most likely to lead to success. We demonstrated that the intravenous administration of the antisense oligonucleotide against the splicing enhancer sequence results in exon skipping and production of the dystrophin protein in DMD case for the first time. After extensive studies, anti-sense oligonucleotides comprising different monomers have undergone clinical trials and provided favorable results, enabling improvements in ambulation of DMD patients. Induction of the read-through of nonsense mutations is expected to produce dystrophin in DMD patients with nonsense mutations, which are detected in 19% of DMD cases. The clinical effectiveness of gentamicin and PTC124 has been reported. We have demonstrated that arbekacin-mediated read-through can markedly ameliorate muscular dystrophy in vitro. We have already begun a clinical trial of nonsense mutation read-through therapy using arbekacin. Some of these drug candidates are planned to undergo submission for approval to regulatory agencies in the US and EU. We hope that these molecular therapies will contribute towards DMD treatment.

[Evaluation of six cases of arbekacin inhalation for pneumonia]

Arbekacin (ABK) is one of aminoglycosides which has indications for septicemia and pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA) in Japan. ABK shows good clinical and microbiological efficacies also against Gram-negative bacteria (GNB), including Pseudomonas aeruginosa. In addition, furthermore, ABK would be sometimes effective also against antimicrobial-resistant GNB. We investigated ABK inhalation, which showed good pulmonary drug delivery, for the treatment of pneumonia caused by multidrug-resistant Gram-negative organisms and MRSA. Six patients with pneumonia were treated with ABK inhalation therapy (50 mg x three times/day). We observed clinical effect for multidrug-resistant organisms in 6/6 patients. Although routine use of aerosolized antibiotics might not be able to be recommended for multidrug-resistant organisms, we might be able to adopt the ABK inhalation therapy for pneumonia especially caused by multidrug-resistant Gram-negative organisms in some situations where systemic therapy alone might be failure or inadequate, or where intravenous access is not available because of systemic toxicity. Further studies would be needed for ABK inhalation therapy for pneumonia.

[Clinical investigation of arbekacin sulfate based on Cmax/MIC]

We examined the peck concentration (Cmax)/minimal inhibitory concentration (MIC) and the clinical efficacy in methicillin-resistant Staphylococcus aureus (MRSA) pneumonia and Gram-positive cocci bacteremia. We evaluated arbekacin (ABK) on 22 cases of pneumonia and 10 cases of bacteremia in Aichi Medical University Hospital between August 2008 and July 2011, retrospectively. In pneumonia cases, Cmax/MIC was 16.4 +/- 2.8 in the effective group, and was 17.6 +/- 4.5 in the not effective group, the significant differences were not accepted (p = 0.8). The dosage of ABK was 4.7 +/- 1.4 mg/kg/dose in the effective group and was 4.3 +/- 0.7 mg/kg/dose in the not effective group. In bacteremia cases, Cmax/MIC was 24.2 +/- 13.9 in the effective group and 12.9 +/- 3.9 in the not effective group about clinical efficacy, and the high tendency was accepted by the effective group (p < 0.05). The dosage of ABK was 3.4 +/- 1.1 mg/kg/dose in the effective group, and 3.0 +/- 0.6 mg/kg/dose in the not effective group. In this examination, the significant difference was not observed in clinical efficacy and Cmax/MIC in the pneumonia cases. Although it was reported that clinical efficacy of ABK was given Cmax/MIC at eight or more, in this examination, all cases was eight or more at Cmax/MIC, and the clinical effect was 40.9%. On Cmax/MIC of ABK, clinical effective group was higher than not effective group in bacteremia cases, it was suggested that the administration design should make that Cmax/MIC at least about 14 or more would be necessary.

MRSA-pyomyositis in a patient with acute myelogenous leukemia after intensive chemotherapy

BACKGROUND

A case of methicillin-resistant Staphylococcus aureus (MRSA)-pyomyositis in association with acute myelogenous leukemia (AML) is reported. MRSA-sepsis developed in a 51-year-old Japanese man with AML, during the neutropenic period after high-dose 1-beta-d-arabinofuranosylcytosine (Ara-C). Although the MRSA-sepsis initially improved with arbekacin sulfate (ABK) administration, a high fever recurred with left thigh pain despite recovery of the neutrophil count after ABK was stopped. A computed tomographic (CT) scan showed a low-density area in the left quadriceps femoris muscle, which led to a diagnosis of pyomyositis. MRSA was cultured from the abscess aspirates. The fever and thigh pain disappeared after administration of ABK and minocycline hydrochloride (MINO), and the abscess completely disappeared with the oral administration of levofloxacin (LVFX) for about 3 months.

CONCLUSION

If an immunocompromised patient complains of fever and muscle pain after intensive chemotherapy, MRSA-pyomyositis should be considered.

Pharmacokinetic-pharmacodynamic relationship of arbekacin for treatment of patients infected with methicillin-resistant Staphylococcus aureus

Arbekacin is widely used in Japan for the treatment of patients infected with methicillin-resistant Staphylococcus aureus (MRSA). In this study, we have determined the optimal concentration targets of arbekacin for both efficacy and safety. A pharmacokinetic-pharmacodynamic analysis was performed to relate exposure to the drug and clinical cure/improvement or nephrotoxicity. Since we have reported the population pharmacokinetic parameters for arbekacin in the preceding paper (Y. Tanigawara, R. Sato, K. Morita, M. Kaku, N. Aikawa, and K. Shimizu, Antimicrob. Agents Chemother. 50:3754-3762, 2006), individual exposure parameters, such as area under the concentration-time curve (AUC), peak concentration (C(max)), AUC/MIC, C(max)/MIC, and trough concentration (C(min)) were estimated by the Bayesian method. Logistic regression was used to describe the relationship between exposure to the drug and the probability of clinical cure/improvement or nephrotoxicity. For the clinical efficacy analysis, 174 patients confirmed to have an MRSA infection were evaluated. The C(max), C(min), and AUC of arbekacin were associated with the probability of clinical cure/improvement during monotherapy. It was shown that the probability of cure/improvement rose when the C(max) of arbekacin was increased, with an odds ratio of 6.7 for a change in C(max) from 7.9 to 12.5 microg/ml (P = 0.037). For the nephrotoxic risk analysis, 333 patients were included, regardless of whether a pathogen was identified. Logistic regression analysis revealed C(min) and AUC as risk factors of nephrotoxicity (P < 0.005). The estimated probabilities of arbekacin-induced nephrotoxicity were 2.5, 5.2, and 13.1% when the C(min) values were 1, 2, and 5 microg/ml, respectively. The present findings are useful for optimizing the individual dose of arbekacin for the treatment of MRSA-infected patients.

Factors influencing neonatal therapeutic effect of anti-MRSA drugs

OBJECTIVE

Factors influencing the neonatal therapeutic effect of anti-MRSA (methicillin-resistant Staphylococcus aureus) drugs are investigated.

METHODS

This study took place over a two-year period from April 1998 to March 2000. We calculated the non-adjusted odds ratio for each influential factor to determine the therapeutic effect of anti-MRSA drugs.

RESULTS

Significant factors for therapeutic effect were found to be platelet count, urea nitrogen, creatinine, and CRP, each measured before starting administration of anti-MRSA drugs; whether blood drug concentration was measured; and whether pneumonia or septicemia was present. There was a tendency where a better therapeutic effect was gained when the total protein and albumin values were high. We applied multivariate logistic regression analysis to these factors, and found the following independent significant factors: CRP (odds ratio (OR) = 1.582), albumin (OR = 3.079), Cre (OR -0.213), whether blood drug concentration was measured (OR = 3.767), and presence of pneumonia or septicemia (OR = 0.216). This result suggests that consideration should be given to these five important factors when treating MRSA patients.

[Combined effects of arbekacin with biapenem against in vitro and in vivo model of a mixture of MRSA and Pseudomonas aeruginosa]

Combined effects of arbekacin (ABK) with biapenem (BIPM) were examined on both in vitro and in vivo model of a mixture of MRSA and Pseudomonas aeruginosa. As a result, significant effect in vitro was observed in combined use of ABK (1/2 MIC) with BIPM (1/4 and 1/2 MIC) against MRSA as compared with ABK or BIPM alone. Against P. aeruginosa combined effect was also observed, showing reduction of viable cells to the limitation of detection within 2 hours. Moreover, with respect to the protective effect on mixed systemic infection of MRSA and P. aeruginosa, the combined treatment with ABK and BIPM showed more excellent efficacy as compared with the single use of each drug.

Application of artificial neural network modelling to identify severely ill patients whose aminoglycoside concentrations are likely to fall below therapeutic concentrations

OBJECTIVE

Identification of ICU patients whose concentrations are likely to fall below therapeutic concentrations using artificial neural network (ANN) modelling and individual patient physiologic data.

METHOD

Data on indicators of disease severity and some physiologic data were collected from 89 ICU patients who received arbekacin (ABK) and 61 who received amikacin (AMK). Three-layer ANN modelling and multivariate logistic regression analysis were used to predict the plasma concentrations of the aminoglycosides (ABK and AMK) in the severely ill patients.

RESULTS

Predictive performance analysis showed that the sensitivity and specificity of ANN modelling was superior to multivariate logistic regression analysis. For accurate modelling, a predictable range should be inferred from the data structure before the analysis. Restriction of the predictable region, based on the data structure, increased predictive performance.

CONCLUSION

ANN analysis was superior to multivariate logistic regression analysis in predicting which patients would have plasma concentrations lower than the minimum therapeutic concentration. To improve predictive performance, the predictable range should be inferred from the data structure before prediction. When applying ANN modelling in clinical settings, the predictive performance and predictable region should be investigated in detail to avoid the risk of harm to severely ill patients.

Effect of arbekacin on a methicillin-resistant Staphylococcus aureus-induced biofilm in a rat model

Biofilms are a major concern for clinicians in the treatment of infectious disease because of their resistance to a wide range of antibiotics. Arbekacin, an aminoglycoside antibiotic, is the drug of choice for the treatment of infection caused by methicillin-resistant Staphylococcus aureus (MRSA). However, it has not yet been defined whether arbekacin tends to penetrate into the biofilm structure induced by MRSA infection. In this study, we treated a biofilm mode of MRSA growth with arbekacin, using a rat air-pouch model. The model has the advantage of permitting frequent sampling of exudates for bacterial counts and antibacterial activity. A clear dose-dependent bactericidal effect was detected in rats treated with arbekacin at concentrations between 0.3 and 10 mg/kg, but 0.1 mg/kg of arbekacin was ineffective against the experimental MRSA infection in rats. Morphological studies using scanning electron microscopy and histochemical staining demonstrated that an effective dosage of arbekacin induced dramatic changes in the biofilm membranous structure as well as in the inflammatory response, resulting in eradication of the biofilm structure and resolution of inflammation.

Efficacy and safety of arbekacin for staphylococcal infection in the NICU

BACKGROUND

This is a retrospective study on the efficacy and safety of arbekacin (ABK), an aminoglycoside antibiotic, for acquired staphylococcal infection in the neonatal intensive care nursery.

PATIENTS AND METHODS

Subjects were 29 infants treated with ABK in a tertiary care neonatal center. They were 23-39 (median 28) weeks' gestation, 530-3334 (median 930) grams at birth, and 3-157 (median 17) days of age. Diagnosis of staphylococcal infection was made by clinical signs and laboratory findings. Sensitivity of the isolated organisms to ABK was tested by the microliquid dilution method. Serum ABK level was monitored to achieve the therapeutic range during the treatment. Effectiveness was defined by improving clinical signs and laboratory findings within 3 days. Effectiveness was studied in relation to type of infection and other antibiotics administered. Auditory brainstem response and serum creatinine changes were studied for ototoxicity and nephrotoxicity assessment, respectively.

RESULTS

Twenty-seven (93.1%) cases of infection were attributed to methicillin-resistant Staphylococcus aureus (MRSA) and two (6.9%) were attributed to coagulase-negative staphylococci (CNS). The rate of in vitro sensitivity to ABK was 85.2% for MRSA and 100.0% for CNS. The overall clinical effeciveness rate was 79.3% (23/29) with no difference associated with types of infection. Combination of ABK with sulbactam/ampicillin showed greater effectiveness (100.0%) than with other antibiotics (64.3%) (P < 0.05). There was no abnormal auditory brainstem response or serum creatinine change associated with ABK treatment.

CONCLUSION

ABK is an effective and safe antibiotic for the treatment of acquired staphylococcal infection in the neonatal intensive care nursery.

Methicillin-resistant Staphylococcus aureus and methicillin-resistant Staphylococcus epidermidis infections in the cornea

PURPOSE

To describe the incidence and clinical management of corneal infections with methicillin-resistant Staphylococcus aureus (MRSA) or methicillin-resistant Staphylococcus epidermidis (MRSE).

METHODS

The incidence of methicillin-resistant Staphylococcus (MRS) at the Department of Ophthalmology, Kyoto Prefectural University of Medicine, was reviewed during the 5-year period from January 1996 to December 2000. Clinical aspects of MRS colonization or infection in the eye were investigated.

RESULTS

Methicillin-resistant S. aureus or MRSE was detected from 30 eyes with ocular diseases; post-keratoplasty (11 eyes), ocular surface disorders without operation (9 eyes), and others (10 eyes). Among the 30 eyes, 12 manifested keratitis. Eight cases (8 eyes) occurred after keratoplasty, including four postoperative cases in patients with Stevens-Johnson syndrome, and two bilateral cases (4 eyes) in patients with acute-phase Stevens-Johnson syndrome. The degree of MRS keratitis was classified into 4 groups: asymptomatic carrier or conjunctivitis, intraepithelial infiltrations, superficial keratitis, and severe keratitis leading to corneal perforation. All cases of keratitis were treated successfully with topical ofloxacin (OFLX), vancomycin (VCM), or arbekacin (ABK).

CONCLUSION

Factors associated with ocular MRS colonization were long-term use of antibiotics and/or steroids, and hospitalization. Patients who had undergone keratoplasty or who had Stevens-Johnson syndrome were at increased risk of MRS keratitis. Superficial stromal infiltrations, minimal melting, and minimal stromal scarring are characteristic of MRS keratitis. Therapy for MRS keratitis is summarized. Ofloxacin, VCM, and ABK are effective in the treatment of MRS keratitis. Vancomycin eye ointment is effective as the final choice in serious cases.

[Effect of arbekacin on the production of toxic shock syndrome toxin 1 by methicillin-resistant Staphylococcus aureus]

The effect of arbekacin (ABK), vancokmycin (VCM) and teicoplanin (TEIC) on the production of toxic shock syndrome toxin-1 (TSST-1) by methicillin-resistant Staphylococcus aureus was examined. In logarithmic-phase cultures, ABK, VCM and TEIC inhibited TSST-1 production by 85, 10 and 25%, respectively, at the concentration of one-fourth the each MIC. In stationary-phase cultures, ABK inhibited TSST-1 production by 50% or 90% compared with the control at the concentration of 4.0 micrograms/ml or 5.0 micrograms/ml respectively. VCM and TEIC did not inhibit TSST-1 production at the concentration of 8.0 micrograms/ml or lower. In human blood cultures, TSST-1 production was inhibited by ABK by 50% at 0.04 microgram/ml (1/256 of Cmax), but not inhibited by VCM and TEIC at the concentration of 1/16 of Cmax or lower. It has been already known that ABK has higher bactericidal activity than VCM and TEIC. ABK combined the inhibition of TSST-1 production with high bactericidal activity in both bacterial growth phases, and therefore ABK should be considered for the treatment of TSST-1-mediated MRSA-infection.

Efficacy of ampicillin plus arbekacin in experimental rabbit endocarditis caused by an Enterococcus faecalis strain with high-level gentamicin resistance

Enterococcus faecalis LC40 is an ampicillin-susceptible clinical isolate with high-level gentamicin resistance due to the aac(6')-Ie-aph(2")-Ia aminoglycoside resistance gene. The combination of ampicillin plus arbekacin reduced mean bacterial vegetation counts significantly more than ampicillin alone or ampicillin plus gentamicin in a rabbit model of aortic-valve endocarditis caused by E. faecalis LC40.

[MRSA septicemia caused by an infected pacemaker lead: a case report with a review of Japanese literatures]

A 50-year-old woman was admitted to our hospital because of MRSA septicemia caused by a contaminated permanent pacemaker lead. A pacemaker system was successfully removed under cardiopulmonary bypass support. Postoperative antibiotics was administered for 7 weeks. Total removal of a pacemaker system under cardiopulmonary bypass support is the treatment of choice in a case with pacemaker infection associated with MRSA septicemia.

In vitro susceptibility and molecular analysis of gentamicin-resistant enterococci

Enterococci with gentamicin MICs of 256 to 1,024 micrograms/mL were evaluated for susceptibility to ampicillin plus gentamicin synergism. Sixteen of eighteen enterococcal isolates were not susceptible to synergistic killing by ampicillin plus gentamicin; 11 possessed aac(6')-aph(2"), and 4 possessed aph(2")-Ic. A gentamicin MIC of 512 or 1,024 micrograms/mL predicted lack of ampicillin/gentamicin synergism, but a gentamicin MIC of 256 micrograms/mL did not. For six enterococcal strains possessing the gentamicin-resistance gene aph(2")-Ic, ampicillin plus dibekacin, ampicillin plus netilmicin, and ampicillin plus amikacin produced synergistic killing in five, three, and two strains, respectively.

[Emergence of hetero-VRSA strains in Japanese hospitals and its countermeasure]

Vancomycin-resistant MRSA (VRSA with MIC > or = 8 mg/L) has been described, recently. Although the incidence of VRSA has been low in Japanese MRSA strains, hetero-VRSA (heterogeneously resistant VRSA with MIC levels of 2-4 mg/L) is found in considerable abundance in Japanese hospitals, that may explain fairly frequent therapeutic failure in the vancomycin treatment of MRSA infection. Hetero-VRSA may also serve as precursor for VRSA in some clinical settings where it is exposed to high concentrations (8 mg/L or above) of vancomycin.

Antibiotic-loaded hydroxyapatite blocks in the treatment of experimental osteomyelitis in rats

A novel drug delivery system for osteomyelitis was developed in which a porous hydroxyapatite block (HAB) is loaded with antibiotic by a centrifugation method. In this study, implantation of HABs loaded with the aminoglycoside antibiotic, arbekacin, were tested in established Staphylococcus aureus osteomyelitis in the proximal tibia of rats after debridement of the marrow cavity. The animals were observed for radiographic signs of infection and tissue was examined histologically. The infections were also evaluated by bone cultures. Bacterial counts were statistically lower in rats implanted with an antibiotic-loaded HAB than in those given a drug-free HAB. Radiographical and histological observations also showed beneficial effects of the antibiotic-loaded implant. The results suggest that the centrifugation method for loading HABs provides a simple drug delivery system. These antibiotic-loaded HABs may be useful for filling grafts in osteomyelitis.

Experimental study on bacterial colonization of fibrin glue and its prevention

To assess the possibility of bacterial colonization of fibrin glue and the effects of adding local sustained-release antibiotics, we conducted in vivo and in vitro preliminary studies. The in vitro experiments revealed that, although there was no colonization of the fibrin glue plates by the eight strains of bacteria tested, the fibrin mesh can serve as a culture medium when blood mingles with it, as is the case in clinical use. Adding dibekacin sulfate (DKB; 3570 micrograms/mL) to fibrin glue decreased the likelihood of colonization of the fibrin mesh. The pharmacokinetics of the added DKB were investigated by adding DKB-supplemented fibrin glue directly to muscle and vascular tissue in male rats. The DKB rapidly eluded from the fibrin glue (less than 0.2% remained after 24 hours). Because the amount remaining after 7 days (2.03 micrograms/mL) was greater than the minimum inhibitory concentration for most clinical pathogens, a 7-day preventive effect against colonization of the fibrin glue and the surrounding tissue can be anticipated at the concentration used in the present experiments. Experiments using the dermis layer of porcine skin strips showed that the added DKB did not affect the adhesive strength of the fibrin glue.

[Laboratory and clinical studies on combined effects of fosfomycin plus sulbactam/cefoperazone for mixed infections of MRSA and Pseudomonas aeruginosa]

The time-lag/sequential/step by step chemotherapy by fosfomycin plus sulbactam/cefoperazone including a short time small dose of steroid was done for 27 severely infected patients suffered from various cancer or other severe basal diseases. And the staggered "intensive" chemotherapy with added arbekacin or vancomycin to the previous staggered chemotherapy was done against 13 severely infected patients having MRSAs among their infecting pathogens. 1. Bacteriological effects Pseudomonas aeruginosa 6/8, Staphylococcus epidermidis 5/5, Enterococcus faecalis 3/6, Acinetobacter calcoaceticus 2/2, Klebsiella pneumoniae 2/2, MRSA 2/2, Xanthomonas maltophilia 2/3 and other 10/10 were eradicated (84.2%) by the staggered chemotherapy and MRSA 7/13, P. aeruginosa 3/4, E. faecalis 3/5, A. calcoaceticus 2/2, X. maltophilia 1/1 and others 2/2 were eradicated (53.8% in MRSA, 78.6% in others and 66.7% in total) and 3 of MRSAs were colonized. 2. Clinical effects 1) Staggered chemotherapy: Excellent 18/27, good 8/27, fair 1/27, poor 0/27 (96.3%). 2) Staggered "intensive" chemotherapy: Excellent 6/13, good 4/13, fair 2/13, poor 1/13 (76.9%) in total: excellent 60.0%, efficacy rate 90.0%.

Combined therapy with arbekacin and fosfomycin for methicillin-resistant Staphylococcus aureus infections

We examined the clinical efficacy of a combination of arbekacin and fosfomycin in the treatment of various methicillin-resistant Staphylococcus aureus (MRSA) infections. The combination of arbekacin plus fosfomycin displayed 65.4% (17/26) clinical efficacy and 65.4% (17/26) bacteriological efficacy. This combination thus appeared to be an effective regimen for the treatment of MRSA infections. However, its bacteriological efficacy against concomitant Pseudomonas aeruginosa strains was only 16.7% (1/6). In addition, in 4 episodes of superinfection involving P. aeruginosa strains developed during the combination therapy.

[Clinical efficacy of arbekacin in patients with methicillin-resistant Staphylococcus aureus infections. Research Group of MRSA Forum]

We investigated the clinical efficacy of arbekacin (ABK) in patients with methicillin-resistant Staphylococcus aureus (MRSA) infections, and also studied coagulase types, beta-lactamase producing activity and drug sensitivity of MRSA isolated from various clinical specimens. A total of 23 patients with MRSA infections (13 cases of pneumonia, 1 case of sepsis, 1 case of pneumonia and sepsis and 8 cases of the others) who were hospitalized from April 1992 to September 1993 were enrolled in this study. They were 14 males and 9 females, and the mean age was 66.9 years (range, 18-91 years). All patients had underlying diseases (mainly malignant tumors and cerebrovascular diseases). ABK was given intravenously at doses ranging from 75 to 100 mg twice daily. The clinical efficacy rate was 90%; 8 cases showed excellent responses, 10 cases good, 1 case fair, 1 case poor and 3 cases were unevaluable. The eradication rate of MRSA was 81.8%; 16 cases were judged as eradicated, 3 cases decreased, 2 cases replaced, 1 case unchanged and in 1 case the bacteriological response was unknown. Side effects were not observed, but S-GPT was elevated in 1 case. Coagulase types of MRSA (123 strains) isolated at the institutes involved in the study were type II (56 strains), type IV (12 strains), type VII (13 strains) and other types (2 strains), but coagulase types of 40 strains could not be determined. Eighty-four strains (68.3%) produced beta-lactamases. MICs of ABK were 0.5 microgram/ml against 43 strains and 1 microgram/ml against 37 strains, and all of the MICs were under 4 micrograms/ml. In summary, ABK showed high antimicrobial activity against MRSA and clinical usefulness in the infections investigated.

[Nationwide investigation in Japan of the status of MRSA infections and usefulness of arbekacin]

A clinical investigation on MRSA infections, and the determination of the efficacy and usefulness of arbekacin (ABK) were performed an "MRSA Forum" composed of 18 groups including 115 institutions in Japan. Patients with infectious diseases clearly related with MRSA, a total of 348 (males: 237, females: 111), were evaluated, 74/274 patients were treated with ABK alone/combination with ABK. Most of them (94.6%/96.4%) had underlying diseases and they had pneumonia (38/175), sepsis (6/35) or other infections (30/64). Infections by MRSA alone were noted in 41/159 and polymicrobial infections including with MRSA were in 33/115. 53.6%/56.4% of MRSA were eradicated and bacteriological clinical efficacies were 75.6%/67.9% in single infections and 63.6%/71.3% in polymicrobial infections. The clinical efficacies were obtained in 70.3%/69.3% of total and in 60.5%/72.0% of pneumonia and in 90.0%/80.8% of the patients pretreated with other drugs within 3 days previously. Efficacy rates were 78.6%/71.4% in 30 minute's div and 63.2%/66.4% in 60 minute's div. Adverse effects were found in 4.76%/5.70% including renal function disorder (2/11) but no case was serious. Abnormal laboratory test results were noted in 15.4%. ABK is effective against MRSA infections.

[Clinical analysis of MRSA pneumonia. Niigata Research Group of MRSA.ABK]

Aged or immuno-compromised patients were mostly affected, by pneumonia caused by infection of MRSA, and more than half of the cases were superinfected with glucose-nonfermentative Gram-negative rods including Pseudomonas aeruginosa. These patients were treated with a monotherapy of arbekacin (ABK) by intravenous drip administration or with a combination of ABK and imipenem/cilastatin, ceftazidime or antifungals. The clinical efficiencies were 55.6% in 11 monotherapy cases and 83.3% in combined therapy. MRSA was eradicated in 31.9% of the patients. These results are comparable with, or superior to the vancomycin therapy in the treatment of MRSA pneumonia. When MRSA is isolated from sputum of pneumonia patients, the discrimination between colonization and infection is important, but the diagnosis is very difficult in many clinical cases before the initiation of chemotherapy. The number of bacteria and the grade of inflammation should be carefully scored before starting a chemotherapy.

[Treatment with arbekacin of surgical infections by resistant strains of Staphylococcus aureus. Arbekacin Study Group]

The frequency of infection by methicillin-resistant Staphylococcus aureus (MRSA) is high in Japan and control of such strains is urgently needed. Arbekacin (ABK), a semisynthetic aminoglycoside, has potent activity against S. aureus, including resistant strains, and against Gram-negative bacteria as well. For this reason, in surgical infections (which are often caused by more than one bacterium), this drug might be particularly effective. We calculated the MIC and the decrease in the MIC when cultures of 59 resistant strains of S. aureus isolated in our wards at Osaka City University Hospital, contained arbekacin in the medium. We also used the drug to treat 12 infections caused by resistant strains of S. aureus. The MICs of vancomycin had a single peak at 0.5 microgram/ml, and those for ABK had double peaks at 0.5 and 4.0 micrograms/ml. The effect of arbekacin in lowering the MIC of minocycline (MINO) was slight because of the low MIC of MINO. Effects on fosfomycin (FOM), ampicillin, clavulanic acid/ticarcillin, cefotiam, cefuzonam, flomoxef, and imipenem/cilastatin were strong; the peaks were lowered by 1/2(7)-1/2(11). When 1.0 micrograms/ml ABK was present in the medium, the efficacy of FOM was increased enough that, by prediction from the pharmacokinetics of FOM (blood level when given at the usual dose), all but one (2%) of the 47 resistant strains would be eradicated clinically. If 2.0 micrograms/ml ABK were in the medium, all strain would be eradicated, by our calculations. We treated 11 infections and one colonization by resistant strains of S. aureus with ABK and evaluated the response in these cases of infection. Four infections were treated with FOM as well. The clinical efficacy was good in four infections (three patients), fair in four, and poor in three, for an efficacy rate of 36%. All presumed causative bacteria were eradicated in two (18%) of the 11 infections and S. aureus strains were eradicated in three (27%) of the 11 infections. No symptoms of side effects were reported, but blood urea nitrogen and creatinine rose in a 72-year-old woman with duodenal perforation and peritonitis. The MIC levels of ABK were satisfactory, but clinical efficacy for staphylococcal infections caused by resistant strains was unsatisfactory.

[Clinical efficacy of arbekacin on MRSA infections with hematopoietic disorders. The Hanshin Study Group of Hematopoietic Disorders and Infections]

Arbekacin (ABK) was administered to 17 patients with MRSA infections that complicated underlying hematopoietic disorders, and the efficacy and safety were evaluated. The underlying diseases included acute myelocytic leukemia (8 cases), acute lymphocytic leukemia (1) myelodysplastic syndrome (3), chronic myelocytic leukemia (1), non-Hodgkin's lymphoma (2), Hodgkin's disease (1) and adult T cell leukemia (1). The infections consisted of septicemia (5 cases), pneumonia (4), upper respiratory tract infections (6) and urinary tract infections (2). ABK was administered by i.v. drip infusion in daily doses of 150-200 mg, given in two divided dosages. The therapeutic efficacies were: excellent in 2 (2 septicemias), good in 7 (1 septicemia, 4 upper respiratory infections, 2 urinary tract infections), fair in 2 (septicemia and pneumonia) and poor in 6 (1 septicemia, 3 pneumonias, 2 upper respiratory infections). As a side effect, reversible renal dysfunction was detected in four cases. Causative bacteria were isolated from six cases. They were all coagulase type II and MIC's of ABK were from 0.25 microgram/ml to 4.0 micrograms/ml. Arbekacin therapy was found to be effective even in patients with hematopoietic disorders accompanied by MRSA infections.

[Antibacteriological activities of arbekacin and vancomycin against strains of MRSA]

The activities of arbekacin (ABK) and vancomycin (VCM) against MRSA were compared, and the results are as follows. 1. In antibacterial activities (MIC value) against 142 strains of MRSA, MIC50 of ABK was two times less than that of VCM. MIC90's were both 1.56 micrograms/ml. 2. ABK was also superior to VCM in bactericidal activities within a short time against 100 strains of MRSA. After 4 hours, 42 strains were killed to below 10(-2) by 2 MIC of ABK, but 6 strains were killed to 10(-2) by 4 MIC of VCM. 3. Against the MRSA 1936 strain, neither ABK nor VCM was active, when an inoculum size of about 10(8) CFU/ml was used. At an inoculum size of 10(5) CFU/ml, ABK showed strong bactericidal activity in a dose dependent manner, while bacteria killing activity of VCM was time dependent. 4. In experimental infections with the MRSA 1936 strain, ABK showed high bactericidal activity rapidly, and area of body that showed bacterial inhibition appeared to be large compared to that obtained with VCM. 5. As to protection from MRSA infections, ABK was significantly superior to VCM in activities against 3 out of 4 strains of MRSA tested. ABK showed more pronounced efficacy when administered in a single dose than in divided doses. These results indicated that ABK would exhibit therapeutic efficacy in a short time.

[Clinical efficacy of arbekacin on MRSA infections]

Clinical efficacy of arbekacin (ABK) was examined on patients with MRSA infection during hospitalization in Nagoya University Hospital. A total of 15 analysed cases of 5 sepsis, 3 pneumonias, 6 wound infections and one abdominal abscess. ABK was administered intravenously by drip infusion of 200 mg per day divided into 2 doses with or without other antibiotics. Overall clinical efficacy rate was 76.9%, and eradication rate for the MRSA was 54.5%. Adverse effects were noted in 3 cases (one each case of urticaria, disorder of liver function, and renal disorder). The renal disorder was found in the case where ABK was used in combination with vancomycin.

[An evaluation study on arbekacin for MRSA-infectious diseases including pneumonia, septicemia and others]

Availability of arbekacin (ABK) was analyzed in the chemotherapy of 24 MRSA-infected patients with symptoms of pneumonia (12), sepsis (6) and others (6). Most patients had background diseases such as malignant tumors or cerebrovascular disorders. 47% (7/15) of them were immunologically abnormal. 17 of them had been previously treated with cephems, imipenem, minocycline or fosfomycin. The ABK therapy was performed with doses ranging 50-400 mg a day, divided into 1-3 times (mostly 100 mg x 2), and for 5-24 days. (18 patients were treated between 5 and 14 days). 14 patients (58%) received combined therapy with other antibiotics (mostly with beta-lactams, 12). The clinical efficacy rate of the ABK therapy was 62% (good, 13; fair, 4; ineffective, 4; unknown, 3). The bacteriological efficacies were: eradicated, 7 (44%); decreased, 4; no change, 5; unknown, 8. Side effects were found in 3 patients (oliguria, 2; eruption due to drug, 1) and one case resulted in serious renal disorder. Abnormal laboratory data were found in 7 cases. Above results have indicated that ABK is a useful antibiotic in chemotherapy of MRSA-infections.

[Clinical efficacy of arbekacin on MRSA pneumonia]

Arbekacin sulfate (ABK) was administered by intravenous drip to pneumonia patients infected with methicillin-resistant Staphylococcus aureus (MRSA), and the efficacy and the safety were objectively evaluated by the executive committee. The daily dose was determined in principle as 150-200 mg, two times a day, 30-90 minutes drip infusion, and the dose was to be changed at each special occasion. Combined therapy with other antibiotics was scheduled in severe cases at a decision of the physician in charge. Data of 18 cases were accumulated. The efficacy could be evaluated for 12 cases (4 cases with ABK alone, and 8 cases with combined therapy), and the safety was evaluated for 18 cases. The clinical efficacy was: excellent, 1; good, 4; fair, 5; and poor, 2. The efficacy rate was 41.7%. The bacteriological effect was: eradicated, 2 (16.7%); decreased, 2; and no change, 8. There found no side effects except 3 cases of abnormal laboratory data, two abnormal renal functions(11.1%) and one abnormal hepatic function (5.5%). In one of the renal disorders, decreased dose of ABK improved the function. In the other case, the impaired renal function lasted until death by heart failure. In the case of abnormal function, discontinuing the ABK therapy improved the hepatic function. In the 4 out of 5 cases that showed excellent or good clinical efficacy, patients recovered within relatively early days of ABK therapy. The average days for recovery was 7.8.

[Clinical effect of arbekacin on MRSA infections after gastrointestinal surgery]

From January 1991 to July 1993, 58 patients with MRSA infections in our clinic at Wakayama Medical College and six affiliated hospitals were administered with arbekacin (ABK). The clinical results were as follows: 1. The clinical efficacy rates of ABK were 84% in pneumonia, 100% in both wound infections and hepatobiliary tract infections, and 85% in total. The bacteriological efficacy rate was 83%. 2. Regarding the administration route, the clinical efficacy rates were 60-79% by the intravenous treatment and inhalation therapy. Especially by the local administration with ABK, MRSA was eradicated in all cases. 3. The sufficient efficacy was obtained by the treatment of ABK alone (89%) and by the combined treatment with ABK (82%) and another antibiotics. From these results, it is concluded that ABK is useful for the treatment of MRSA infections after gastrointestinal surgery.

[Questionnaires regarding MRSA in Japan]

Changes in properties of MRSA and the status of MRSA infections in the last two years were investigated by an MRSA Forum composed of 18 groups including 115 medical institutions in Japan. And an opinion poll regarding MRSA was taken by professional doctors (41) and general clinical doctors (323). Points of discussion: 1. Did properties of MRSA change? 2. Did the pattern of MRSA infections change? 3. Did the understanding of MRSA change? 4. What is the relationship between MRSA and the 3rd cephems? 5. How is MRSA related to polymicrobial infections? 6. Is ABK useful against MRSA infections? 7. What will be future trend in characteristics of MRSA and MRSA infections?

CONCLUSIONS

1. MRSA has become more resistant to methicillin however it seemed to have become less toxic. 2. Severe MRSA infections are decreasing and colonizations are increasing. 3. There were some differences in attitude against MRSA between professional doctors and general clinical doctors. 4. The 3rd cephem should be used reasonably. 5. MRSA infections should be treated with polymicrobial infections in consideration. 6. MRSA did not gain resistance against ABK and ABK is useful against MRSA infections. 7. Problems of MRSA will cool down but they should always be kept in our mind.

[Clinical efficacy of arbekacin in deep MRSA infection. Including follow-up study after the termination of chemotherapy]

We analyzed the efficacy of arbekacin (ABK) using monotherapy or combined therapy on deep MRSA infection to find the most adequate usage of the drug. We also followed-up the isolation incidence of MRSA after the end of chemotherapy. The results are summarized as follows: 1. Clinical efficacy of ABK on 29 pneumonia and 3 septicemia due to MRSA was 42.9% in ABK monotherapy (9 patients), 62.5% in combined therapy with ABK and minocycline (9 patients), 100% with ABK and imipenem/cilastatin (IPM/CS) (7 patients), and 100% with ABK and other drugs (7 patients). 2. As for microbiological efficacy, combined therapy with ABK and IPM/CS or other drug was superior to other methods. Among patients from whom two or more species of bacteria were isolated, causative bacteria persisted in many cases, and some replacements occurred. 3. Kidney functions deteriorated in two patients that underwent monotherapy or combined therapy with ABK and IPM/CS, but they recovered when therapy was completed the completion. 4. In the three month follow-up study after ABK therapy, we found four cases of renewed infections after disappearance of MRSA. When just decreases in the number of MRSA resulted upon the chemotherapy, the relapse occurred in all cases. 5. Above results indicate that ABK is effective in MRSA infection, and combined therapy with beta-lactams is superior to other methods in serious MRSA infections. We also suggest that chemotherapy should be continued until the complete disappearance of MRSA is achieved.

[Efficacy of combination therapy against MRSA in Ibaraki Prefecture]

Clinical efficacies of fosfomycin (FOM) or arbekacin (ABK) plus beta-lactam combination therapies against methicillin-resistant Staphylococcus aureus (MRSA) infections were examined in 15 major hospitals in Ibaraki Prefecture. The subjects were 54 inpatients from January 1991 to April 1993, and most of them showed moderate to severe infections with underlying diseases. MRSA alone was isolated from 23 patients and the other 31 patients had polymicobes including MRSA. Pseudomonas aeruginosa was the most frequent among the co-isolated strains. The number of patients treated with FOM and cefmetazole (CMZ) was 22 (Group C) and that with FOM and flomoxef (FMOX) was 25 (Group F). CMZ or FMOX was administrated 60 minutes after FOM administration. To 8 nonresponding patients in Groups C and F and 7 nonresponders to the other therapies, ABK and ceftazidime (CAZ) or ABK and piperacillin (PIPC) were treated simultaneously (Group A). The clinical efficacies of Groups C and F were 63.6% and 64%, respectively. The bacteriological efficacies (eradication rates) of both groups including microbial substitutions were 42.9% in the former and 56.5% in the latter. No statistical differences were observed in the clinical and the bacteriological efficacies between Groups C and F. The clinical and bacteriological efficacies in Group A were 66.7% and 46.2%, respectively. No side effects were observed in any cases. Mild disturbances of hepatic functions were observed in 2 cases of Groups C and F, and there were no abnormal laboratory test results in Group A.(ABSTRACT TRUNCATED AT 250 WORDS)

[Evaluation of bactericidal activity of arbekacin in mixed culture with MRSA and Pseudomonas aeruginosa using an in vitro pharmacokinetic simulation system]

The bactericidal activities of arbekacin (ABK), vancomycin (VCM), gentamicin (GM) and netilmicin (NTL) in mixed culture with Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa were examined using an in vitro computer programmed pharmacokinetic simulation system and also the protective effect of these agents on systemic infection in neutropenic mice was examined. In a mixed culture of S. aureus No. 235 (MRSA) and P. aeruginosa E7, ABK showed a strong bactericidal activity and an inhibition of regrowth against both bacteria, and GM and NTL showed similar effects. On the other hand, VCM showed a bactericidal activity against S. aureus No. 235, but not against P. aeruginosa. In the protective study, ABK was evidently more effective than GM, NTL or VCM against a systemic mixed infection of mice with S. aureus No. 235 and P. aeruginosa E7. In brief, the ED50 values of ABK, VCM, GM and NTL were 19.5, > 100, 40.5 and 45.2 mg/kg, respectively.

[Clinical effect of the combined therapy of arbekacin and imipenem/cilastatin against methicillin-resistant Staphylococcus aureus]

We evaluated the efficacy of combined therapy of arbekacin (ABK) and imipenem/cilastatin (IPM/CS) against infections by methicillin-resistant Staphylococcus aureus (MRSA). The MICs of ampicillin, cefmetazole, cefotiam, cefuzonam, flomoxef, fosfomycin, ofloxacin, minocycline, ABK and IPM/CS against clinically isolated strains of MRSA were examined. Almost all strains of MRSA were resistant to these antibiotics except ABK. Furthermore, combination of ABK and IPM/CS showed smaller MICs than that of ABK or IPM/CS alone. All fractional inhibitory concentration indices (FIC indices) of ABK plus IPM/CS were lower than 0.75. The efficacy rate of combined therapy of ABK and IPM/CS in 22 patients with MRSA infections (15 patients with pneumonia, 3 patients with chronic bronchitis, 2 patients with sepsis, a patient with subcutaneous abscess and a patient with DPB) was 68%. And no patients had adverse reactions. Six (27%) of 22 strains of MRSA were eradicated. Significant correlations were found between bacteriological effect and severity of disease, and between serum albumin level and clinical effect.

[Efficacy of arbekacin, a new aminoglycoside antibiotic, in surgical patients with MRSA infections]

The clinical efficacy of a new aminoglycoside antibiotic, arbekacin (ABK), was studied in surgical patients who had been infected with methicillin-resistant Staphylococcus aureus (MRSA). Six cases of pneumonia, 2 of wound infections and 2 of intra-abdominal infections were treated by ABK alone or ABK together with beta-lactam antibiotics such as imipenem/cilastatin or cefotiam. The overall clinical efficacies against these MRSA infections were excellent in one case, good in 6 and poor in 3. In six cases treated by ABK alone, good clinical responses were obtained in 4 cases. Among 4 cases that received combination therapy with ABK, good responses were obtained in 3 cases. No adverse reactions were found in ABK monotherapy or in combined therapy. These data suggested that ABK is an effective antibiotic on surgical infections caused by MRSA.

The relationship between the degree of chronic middle ear inflammation and tympanic bulla pneumatization in the pig as animal model

The relationship between the degree of chronic middle ear inflammation and pneumatization was investigated in the pig as an animal model, since its tympanic bulla closely resembles the human mastoid air cell system. Ten piglets (sire: Landrace-Hampshire crossbreed; dam: Duroc) were used for this experiment. Four ears of two animals served as the normal control group and 16 ears of eight animals were the experimental group. In this latter group, otitis media was induced by injecting glycerin into the middle ear clefts 1 months after birth, and the degree of inflammation was varied by administering or withholding antibiotics (cefamandole and dibekacin) and adjusting the dosage regimen. The animals were sacrificed 6 months after birth and examined for the relationship between the degree of chronic middle ear inflammation present and tympanic bulla pneumatization. Various degrees of inflammation were successfully induced by injecting the antibiotics: the more severe the inflammation found, the greater was the inhibition of pneumatization. Findings demonstrated that the degree of inhibition of pneumatization produced was directly proportional to the severity of chronic middle ear inflammation.

[Treatment of cancer and counter-measures for MRSA infections]

Patients with malignancy, especially those with hematological malignancy, are well known to be very susceptible to infection in general, because of bone marrow suppression induced by anticancer chemotherapy in addition to the nature of the disease itself. Accordingly, the risk of MRSA infection is very high in these patients, and the infection is often fatal. In an attempt to establish effective measures to prevent MRSA infection, we investigated the nosocomial spread of strains of MRSA and studied the characteristics of patients from the clinical standpoint. We found that strict isolation of patients with MRSA infection is an urgent necessity to prevent the intrahospital spread of MRSA strains and that disinfection of the hands of medical staff and sterilization of the environment are extremely important. In addition, due care must be taken to select an adequate antimicrobial agent and to determine the optimal dose and period for treatment of the infection in patients with malignancy to avoid selecting MRSA strains or inducing resistance in mecA positive strains of S. aureus. For treatment of MRSA infections in patients with malignancy, a combination chemotherapy with vancomycin (VCM), or arbekacin (ABK) plus beta-lactam antibiotic is recommended, and granulocyte colony stimulating factor (G-CSF) is clinically useful when the granulocytopenia was induced by chemotherapy.

[Clinical studies of arbekacin sulfate in the pediatric field]

A clinical investigation was carried out to evaluate arbekacin, an aminoglycoside, in the treatment of MRSA infections (pneumonia, septicemia, etc.) of pediatric patients. The obtained results are summarized as follows. 1.

CLINICAL RESULTS

Excluding those patients who met the present exclusion criteria and withdrawal cases from a total of 18 patients, 10 patients (3, 6, and 1 cases of septicemia, pneumonia, and urinary tract infection, respectively) were subjected to clinical evaluation. These were composed of 1, 1, 6, and 2 cases of neonate, infants, pre- and school age children, respectively. Excellent, good and fair results were obtained in 5, 2, and 3 patients, respectively; thus, the efficacy rate was 70.0%. The efficacy rate by disease was 100%, 50.0% and 100% in septicemia, pneumonia, and urinary tract infection, respectively. The bacteriological eradication were obtained in 70.0% of the total patients; by disease, these rates were 100% and 50.0% in septicemia/urinary tract infection and in pneumonia, respectively. The MIC50 as well as the MIC80 against MRSA strains isolated from 9 patients were 0.39 microgram/ml and 1.56 micrograms/ml, respectively. No adverse reactions were observed in the 15 patients, while in laboratory test values, one case each out of 12 patients examined showed gamma-GTP elevation, proteinuria, and hematuria. 2. Pharmacokinetics: The pharmacokinetics of the agent was investigated in a total of 9 patients, which included 1 neonate and 4 cases each of pre- and school age children. The Cmax, 4.85-8.83 micrograms/ml, was observed immediately after the termination of the instillation. The T1/2's were 4.96 hours, 1.24-2.54 hours, and 1.78-1.88 hours in the neonate, the pre- and the school age children, respectively; in the neonate the half-life was longer. When 1.92-2.7 mg/kg were administered to 3 each of the pre- and school age children, urinary excretion rates in the first 6-8 hours were 40.1-56.5% of the dosages administered. In all cases, the urinary concentrations were highest in the first 2 hours, after the administration, and then gradually decreased. These results suggest that arbekacin is a useful antibiotic for treating MRSA infections in the pediatric field.

Treatment of osteomyelitis by antibiotic impregnated porous hydroxyapatite block

A novel drug delivery system was developed for osteomyelitis using porous hydroxyapatite blocks (HA-b) that were impregnated with antibiotics by a centrifuge method. For the experimental study, a 10 mm3 HA-b was placed in a container, mixed with an antibiotic solution and centrifuged at 1500 rpm for 15 min for the purpose of impregnating antibiotics into the pores. The slow release activity of antibiotic (Arbekacin sulfate [1-N-(S)-4 amino-2-hydroxybutyryl dibekacin]) from the HA-b was tested. An evaluation was made of the slow-releasing capabilities of the ABK from HA-b which was still maintained at 0.5 microgram/ml within 21 exchanges of PBS after 42 days. Consequently, seven patients with osteomyelitis, including one with tuberculosis and two with infected hip arthroplasty, have been treated. On a follow-up study, all of the foci had completely healed by the end of the follow-up period without complications. This new method is simple and can be performed safety as a one-stage operation.

[Clinical studies on methicillin-resistant Staphylococcus aureus (MRSA) infections]

We experienced 20 cases of methicillin-resistant Staphylococcus aureus (MRSA) infection from April 1991 to September 1992. Of them, 9 showed substantial morbidity and their clinical courses are herein reported. The clinical presentations of these cases were wound infection and enterocolitis. Although in 8 cases MRSA was eradicated in 14 to 160 days by effective antibiotics administration, one had a fatal outcome. All strains isolated showed similar drug-sensitivity pattern suggesting hospital infection. Sensitivity to vancomycin and arbekacin, however, remained high and these drugs were effective clinically. It should be stressed that treatment strategy of MRSA infection should consist of isolation of patients with MRSA from other patients, use of disposable equipment and products, and serious and continuing concerns of medical personal on communicability of MRSA.