Biofilm formation of methicillin-resistant coagulase negative staphylococci (MR-CoNS) isolated from community and hospital environments

Methicillin-resistant coagulase negative staphylococci (MR-CoNS) are the major cause of infectious diseases because of their potential ability to form biofilm and colonize the community or hospital environments. This study was designed to investigate the biofilm producing ability, and the presence of mecA, icaAD, bap and fnbA genes in MR-CoNS isolates. The MR-CoNS used in this study were isolated from various samples of community environment and five wards of hospital environments, using mannitol salt agar (MSA) supplemented with 4 μg/ml of oxacillin. The specie level of Staphylococcus haemolyticus, Staphylococcus epidermidis, Staphylococcus hominis and Staphylococcus warneri was identified by specific primers of groESL (S. haemolyticus), rdr (S. epidermidis) and nuc (S. hominis and S. warneri). The remainder isolates were identified by tuf gene sequencing. Biofilm production was determined using Congo red agar (CRA) and Microtiter plate (MTP) assay. The mecA and biofilm associated genes (icaAD, fnbA and bap) were detected using PCR method. From the 558 samples from community and hospital environments, 292 MR-CoNS were isolated (41 from community environments, and 251 from hospital environments). S. haemolyticus (41.1%) and S. epidermidis (30.1%) were the predominant species in this study. Biofilm production was detected in 265 (90.7%) isolates by CRA, and 260 (88.6%) isolates were detected by MTP assay. The staphylococci isolates derived from hospital environments were more associated with biofilm production than the community-derived isolates. Overall, the icaAD and bap genes were detected in 74 (29.5%) and 14 (5.6%) of all isolates from hospital environments. When tested by MTP, the icaAD gene from hospital environment isolates was associated with biofilm biomass. No association was found between bap gene and biofilm formation. The MR-CoNS isolates obtained from community environments did not harbor the icaAD and bap genes. Conversely, fnbA gene presented in MR-CoNS isolated from both community and hospital environments. The high prevalence of biofilm producing MR-CoNS strains demonstrated in this study indicates the persisting ability in environments, and is useful in developing prevention strategies countering the spread of MR-CoNS.

[MRSA and ESBL in outpatient: development from 2008 up to 2012 and socio demographic differences]

Data on resistance from ambulatory care are rarely available, since surveillance systems cover mostly isolates come from inpatient care. The outpatient setting is of interest, however, since it is where hospitalized patients with resistant pathogens are also treated as outpatients, and where patients are seen who have resistant pathogens from other sources, such as food. In addition, 85% of the antibiotics used in human medicine, are used in ambulatory care. Using data from the Antibiotic Resistance Surveillance System (ARS), we show the development of resistance of Staphylococcus aureus to oxacillin and of Escherichia coli and Klebsiella pneumoniae to cefotaxime in outpatient care between 2008 and 2012 and corresponding socio-demographic differences in the resistance rate. According to our analyses, the proportion of MRSA in S. aureus since 2009 in the outpatient sector decreased (all materials: 2009 11.5%, 2012 9.8%), which is similar to inpatient care, while the proportion of ESBL in E. coli (2008 2.7%, 2012 5.6%), and K. pneumoniae (2008 2.7%, 2012 6.6%) increased over the total period. At the same time resistance for the three pathogens in both sexes over the age groups continuously increased, women still hold a lower proportion of resistance than men. The resistance levels of S. aureus and K. pneumoniae in ambulatory care are reflected at a lower level than in hospital care. In contrast, the high proportion of resistant E. coli in children suggests another source in ambulatory care.

Brainstem abscess of undetermined origin: microsurgical drainage and brief antibiotic therapy

CONTEXT

Solitary brainstem abscesses are rare and they are usually associated with other infections. They are severe conditions with high morbidity and mortality. The surgical options are stereotactic aspiration and microsurgical drainage. Systemic antibiotic therapy is used for more than six weeks.

CASE REPORT

We present the case of a young man with a solitary abscess at the pons, without other systemic infections. The patient was treated by means of microsurgical drainage and antibiotic therapy for three weeks. His postoperative recovery was good.

CONCLUSIONS

A microsurgical approach may be considered to be an important option for large abscesses that are multiloculated, close to the surface or contain thick fluid. Complete emptying of the purulent accumulation may diminish the required duration of antibiotic therapy.

Oxacillin or cefalotin treatment of hospitalized children with cellulitis

Cellulitis is an important cause of hospitalization in pediatrics. Because Staphylococcus aureus is the main pathogen of cellulitis, medicinal therapeutics should take the changing resistance profile of this organism into consideration. The aim of this study was to evaluate the progression and outcomes of children hospitalized for cellulitis and treated with oxacillin or cefalotin. This retrospective cohort study enrolled 218 children, hospitalized between 2001 and 2008 in Salvador, Northeast Brazil. All were diagnosed with cellulitis and treated with oxacillin or cefalotin (≥100 mg/kg/day). The median age was 2 years and 56.9% were males. Frequencies of signs and symptoms used in the clinical diagnoses were as follows: swelling (91.3%), redness (81.7%), warmth (47.2%), and tenderness (31.7%). All patients were discharged due to clinical recovery and the mean length of hospitalization was 7 ± 4 days. None of the patients died, needed intensive care, or had sequelae. By comparing the daily frequency of clinical findings during hospitalization, significant decreases were found in the frequencies of fever (admission day [42.2%], first day [20.8%], second day [12.9%], third day [8.3%], fourth day [6.1%]), toxemia, irritability, somnolence, vomiting, tachycardia, and need for intravenous hydration. In conclusion, oxacillin or cefalotin remain the drugs of choice for treating uncomplicated cellulitis in regions where community-acquired methicillin-resistant S. aureus is infrequent (<10%).

Bilateral hip pain caused by adductor pyomyositis as the initial presentation of chronic myeloid leukemia in a 17-year-old child

Pyomyositis is a pyogenic muscular tissue infection mainly occurring in immunocompromised patients. Chronic myeloid leukemia (CML) accounts for only 2-3% of cases of childhood leukemia. Herein, we report on a 17-year-old male with bilateral hip pain caused by adductor pyomyositis before beginning the treatment course of CML. CML was diagnosed by bone marrow chromosome study and was treated initially with imatinib but switched to hydroxyurea 5 days later because of poor cytoreduction response. Subsequently, white blood cell counts decreased gradually; however, the hyperleukocytosis condition resolved very slowly again until we switched back to imatinib use on the 40(th) day of hospitalization. Pyomyositis was diagnosed by magnetic resonance imaging. Oxacillin was administered to cover Staphylococcus aureus, the most common pathogen of pyomyositis. Bilateral hip pain improved within 72 hours after antibiotic usage, but follow-up magnetic resonance imaging after 15 days of treatment revealed well-defined abscess and osteomyelitis of both femoral heads. Abscess incision and drainage were performed, and cultures of the drained pus grew no microorganisms. The patient completed 5 weeks of oxacillin treatment after the operation and recovered with a full range of motion of both hips. There was no residual disability. This is the first report of bilateral hip pain caused by pyomyositis as the initial presentation of CML. Pyomyositis needs to be considered in the differential diagnosis of hip pain in pediatric patients.

Antibiotic treatment schemes for very severe community-acquired pneumonia in children: a randomized clinical study

OBJECTIVE

To compare clinical response to initial empiric treatment with oxacillin plus ceftriaxone and amoxicillin plus clavulanic acid in hospitalized children diagnosed with very severe community-acquired pneumonia (CAP).

METHODS

A prospective randomized clinical study was conducted among children 2 months to 5 years old with a diagnosis of very severe CAP in the pediatric ward of São Paulo State University Hospital in Botucatu, São Paulo, Brazil, from April 2007 to May 2008. Patients were randomly divided into two groups by type of treatment: an oxacillin/ceftriaxone group (OCG, n = 48) and an amoxicillin/clavulanic acid group (ACG, n = 56). Analyzed outcomes were: time to clinical improvement (fever and tachypnea), time on oxygen therapy, length of stay in hospital, need to widen antimicrobial spectrum, and complications (including pleural effusion).

RESULTS

The two groups did not differ statistically for age, sex, symptom duration before admission, or previous antibiotic treatment. Time to improve tachypnea was less among ACG patients than OCG patients (4.8 ± 2.2 versus 5.8 ± 2.4 days respectively; P = 0.028), as was length of hospital stay (11.0 ± 6.2 versus 14.4 ± 4.5 days respectively; P = 0.002). There were no statistically significant differences between the two groups for fever improvement time, time on oxygen therapy, need to widen antimicrobial spectrum, or frequency of pleural effusion.

CONCLUSIONS

Both treatment plans are effective in treating very severe CAP in 2-month-to 5-year-old hospitalized children. The only analyzed outcome that favored amoxicillin/clavulanic acid treatment was time required to improve tachypnea.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT01166932.

Successful medical treatment of spinal epidural abscess

Spinal epidural abscess is a rare but potentially fatal disease. A 67-year-old female suffered fever and painful swelling of the right knee and lower leg for one week. Both synovial fluid and blood cultures yielded methicillin-sensitive Staphylococcus aureus. Low back pain developed and fever was sustained despite the administration of intravenous oxacillin. Magnetic resonance imaging (MRI) of the thoracolumbar spine revealed spinal epidural abscess from T12 to S1. Because of severe hypoalbuminemia and general anasarca and followed by exploratory laparotomy for massive duodenal bleeding, she did not receive surgical intervention for the spinal epidural abscess. After intravenous administration of oxacillin 2 g 4-hourly for 12 weeks, she recovered and follow-up MRI confirmed the efficacy of the medical treatment. She remained well at 1-year follow-up. In a patient with minimal neurological deficit or surgical contraindication, spinal epidural abscess can be successfully treated with a medical regimen.

[Activity of indolicidin, alone or together with oxacillin, against Staphylococcus aureus and S. epidermidis]

Difficulties in the treatment of staphylococcal infections as well as the increasing frequency of isolating resistant clinical strains have prompted a search, among the products of immune systems of plants and animals, for more effective antistaphylococcal therapies. This study examined the activity of indolicidin towards the planktonic cultures and biofilm of Staphylococcus aureus and S. epidermidis strains representing different clinical sources and various profiles of drug sensitivity. The synergistic effect between the peptide and oxacilin was also studied.

Successful treatment of extended epidural abscess and long segment osteomyelitis: a case report and review of the literature

BACKGROUND

Spinal osteomyelitis and epidural abscess are complicated medical conditions. Diagnosis is often delayed because of cormorbidity. The time of instrumentation is still controversial. However, there is no doubting the indication of spinal hardware implantation when spinal fusion is needed. Long segment osteomyelitis and extended epidural abscess are rare. The treatment is challenging for neurosurgeons. We report a case of extended epidural abscesses and long segments of osteomyelitis.

METHODS

One-stage meticulous debridement, anterior cervical corpectomies, and spinal fusion with mesh cage and titanium plate were performed on the patient. Hyperbaric oxygenation and 6 weeks of intravenous antibiotics were prescribed as adjuvant therapy.

RESULTS

Both clinical presentations and imaging studies showed a good response to the treatment. The patient returned to his life 3 months later.

CONCLUSIONS

This case illustrates that spinal instrumentation is not an absolute contraindication in the presence of epidural abscesses and vertebral osteomyelitis. Combined surgical debridement at a critical level, with adjuvant antibiotics and hyperbaric oxygenation, is a safe and effective therapy in those with neurologic deficits, spinal instability, and extended epidural abscess.

Prolonged exposure of methicillin-resistant Staphylococcus aureus (MRSA) COL strain to increasing concentrations of oxacillin results in a multidrug-resistant phenotype

Our previous studies demonstrated that exposure of a bacterium to increasing concentrations of an antibiotic would increase resistance to that antibiotic as a consequence of activating efflux pumps. This study utilises the same approach; however, it employs the methicillin-resistant Staphylococcus aureus (MRSA) COL strain, which is highly resistant to oxacillin (OXA). MRSA COL was adapted to 3200 mg/L of OXA. Changes in resistance to other antibiotics were evaluated and efflux pump activity during the adaptation process was determined. MRSA COL was exposed to stepwise two-fold increases of OXA. At the end of each step, minimum inhibitory concentration determination for erythromycin (ERY) and other antibiotics was conducted. Reserpine (RES) was employed to evaluate whether resistance to ERY was dependent on efflux pump activity. Efflux pump activity was also evaluated using the ethidium bromide (EB) assay. DNA typing of the products of each culture step was conducted to assess purity. Serial exposure of MRSA COL to increasing concentrations of OXA resulted in increased resistance to ERY, which could be eliminated with RES. Evaluation of efflux pump activity by the EB method indicated increased efflux activity. Resistance to ERY was accompanied by resistance to kanamycin, amikacin, ofloxacin, norfloxacin, ciprofloxacin and rifampicin. This is the first time that a multidrug-resistant phenotype has been experimentally produced as a consequence of exposure of the organism to an antibiotic to which it is initially highly resistant.

Antimicrobial activity of berberine alone and in combination with ampicillin or oxacillin against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) bacteria have been responsible for substantial morbidity and mortality in hospitals because they usually have multidrug resistance. Some natural products are candidates as new antibiotic substances. In the present study, we investigated the antimicrobial activity of berberine, the main antibacterial substance of Coptidis rhizoma (Coptis chinensis Franch) and Phellodendri cortex (Phellodendron amurense Ruprecht), against clinical isolates of MRSA, and the effects of berberine on the adhesion to MRSA and intracellular invasion into human gingival fibroblasts (HGFs). Berberine showed antimicrobial activity against all tested strains of MRSA. Minimum inhibition concentrations (MICs) of berberine against MRSA ranged from 32 to 128 microg/mL. Ninety percent inhibition of MRSA was obtained with 64 microg/mL or less of berberine. In the checkerboard dilution test, berberine markedly lowered the MICs of ampicillin and oxacillin against MRSA. An additive effect was found between berberine and ampicillin, and a synergistic effect was found between berberine and oxacillin against MRSA. In the presence of 1-50 microg/mL berberine, MRSA adhesion and intracellular invasion were notably decreased compared with the vehicle-treated control group. These results suggest that berberine may have antimicrobial activity and the potential to restore the effectiveness of beta-lactam antibiotics against MRSA, and inhibit the MRSA adhesion and intracellular invasion in HGFs.

Evaluation of the Efficacy and Safety of Outpatient Parenteral Antimicrobial Therapy for Infections With Methicillin-sensitive Staphylococcus aureus

OBJECTIVES

As increasing numbers of patients are being treated with outpatient parenteral antimicrobial therapy (OPAT), it becomes ever more important to ascertain the risks and benefits of such treatment for patients.

METHODS

We conducted a retrospective analysis of 1,515 patients with methicillin-sensitive Staphylococcus aureus infections who were treated with outpatient parenteral antimicrobial monotherapy. All patients were included in the adverse drug reaction analysis; 1,252 were evaluable for purposes of evaluating treatment efficacy.

RESULTS

The six antibiotics most frequently used in this study (ceftriaxone, cefazolin, vancomycin, oxacillin, nafcillin, and clindamycin) appeared to be equivalent in achieving the desired efficacy outcome.

CONCLUSIONS

Vancomycin was associated with a significantly greater number of side effects than was ceftriaxone, cefazolin, or oxacillin, and nafcillin was associated with a significantly greater number of adverse events than ceftriaxone.

Comparison of linezolid with oxacillin or vancomycin in the empiric treatment of cellulitis in US hospitals

In this decision-model analysis, the authors compared overall clinical efficacy and total cost of empiric treatment of hospitalized cellulitis patients prescribed linezolid and oxacillin or vancomycin. The authors hypothesized that, when used appropriately, empiric linezolid treatment is an effective, potentially cost-saving antibiotic compared with treatment initiated with oxacillin or vancomycin. Data on efficacy, duration of antibiotic treatment, and hospital stay for first-line treatment success were obtained from two clinical trials. Other medical resource use data were obtained from an expert panel of clinicians. US hospital direct medical costs were determined using standard costing techniques. Overall efficacy and total cost of treatment were estimated for combinations of the risk of being infected with methicillin-resistant pathogens. Sensitivity analyses were performed to test the impact of changes in major assumptions. Overall first-line efficacy is better for empiric treatment initiated with linezolid than with oxacillin or vancomycin across the spectrum of the risk of being infected with methicillin-resistant bacteria. The average total cost of treatment is lower for treatment initiated with linezolid than with vancomycin across the spectrum, or than with oxacillin when the risk of being infected with methicillin-resistant pathogens is 18.7 % or higher. Linezolid appears to be at least as effective as vancomycin or oxacillin for empiric treatment of hospitalized cellulitis patients. Linezolid is likely to be less costly compared with vancomycin at all resistance rates and with oxacillin when the risk of infection with methicillin-resistant pathogens is greater than 18.7 %, a resistance rate commonly seen in US hospitals.

Antibiotic administration in an animal model of chronic peritoneal dialysate exposure

OBJECTIVES

The high incidence of intraperitoneal infection remains an important problem in animal models of chronic dialysate exposure. Prophylactic antibiotic administration can be used to resolve this problem, but the isolated effects of antibiotics on peritoneal membrane function and structure are unknown. The present study examined the effects of prophylactic antibiotics on infection rate and peritoneal membrane function and structure in a rat model of chronic dialysate exposure.

DESIGN

A first group of rats (A; n = 12) received 10 mL 3.86% glucose dialysate twice daily through a heparin-coated catheter. In a second group of animals (B; n = 12), oxacillin 2.5 mg/day and gentamicin 0.04 mg/day were added to the dialysate. Group C (n = 12) was injected twice daily with an identical dose of antibiotics dissolved in 1 mL of buffer solution. Group D (n = 12) was left untreated. Dialysate cultures were obtained regularly. After 8 weeks of exposure, peritoneal transport studies were performed and samples for histology were obtained.

RESULTS

Technique survival was 92% in group A and 100% in the remaining groups. Five rats in group A but none of the animals in the other groups developed peritonitis. The transport rates of small solutes were elevated and net ultrafiltration was decreased in group A compared to the controls. Fibrosis, as evaluated by quantifying Picro Sirius Red staining with image analysis, was significantly elevated in group A (3.48% +/- 1.06% vs 0.72% +/- 0.51% in group D, p < 0.05) but not in group B (0.29% +/- 0.07%) or in group C (0.52% +/- 0.28%). Vascular density, measured by counting the number of blood vessels that stained positive for endothelial NO synthase, was increased in both groups that were exposed to dialysate: 153.0 +/- 12.9/microm2 in group A and 131.6 +/- 14.3/microm2 in group B, versus 76.76 +/- 12.37/microm2 in group C and 73.2 +/- 10.4/microm2 in group D (p < 0.01).

CONCLUSIONS

Prophylactic administration of oxacillin and gentamicin adequately prevented intraperitoneal infection in an animal model of chronic dialysate exposure. In addition, fibrosis was absent, suggesting intraperitoneal infection rather than dialysate exposure is a causative factor.

[Management of dermatologic industrial accidents. Skin burns by bitumen as an example]

Hot bitumen burns, although rare, usually occur in workers in the paving or roofing industries. When bitumen is heated to high temperatures it can cause deep burns, and its incorrect removal often causes further skin damage. Application of butter has been proven to be very effective to remove bitumen from the skin. Further clinical and legal safety guidelines for occupational injuries are described.

Spinal epidural abscess successfully treated with percutaneous, computed tomography-guided, needle aspiration and parenteral antibiotic therapy: case report and review of the literature

OBJECTIVE AND IMPORTANCE

We describe a case of a posterior spinal epidural abscess that was successfully treated with percutaneous, computed tomography-guided, needle aspiration and parenteral antibiotic therapy.

CLINICAL PRESENTATION

A 48-year-old man experienced acute pain in the paralumbar region for 1 week, followed by gait disturbance and micturition difficulty. Laboratory studies demonstrated leukocytosis and hyperglycemia. Blood cultures yielded Staphylococcus aureus. Magnetic resonance imaging scans of the thoracolumbar spine revealed a posterior spinal epidural abscess located between L2 and the lower cervical spine.

INTERVENTION

The patient's low back pain persisted despite 10 days of antibiotic therapy. Therefore, percutaneous, computed tomography-guided, needle aspiration was performed. The low back pain was relieved dramatically and immediately after the procedure. The spinal epidural abscess completely resolved after 6 weeks of antibiotic treatment.

CONCLUSION

Surgical decompression and antibiotic therapy are the treatments of choice for patients with spinal epidural abscesses. Selected patients may be treated nonsurgically. Rarely, percutaneous drainage of the abscess has been reported to be helpful. Our case suggests that percutaneous, computed tomography-guided, needle aspiration might be a rational alternative to surgical decompression for treatment of spinal epidural abscesses.

Application of the IDSA guidelines for the use of antimicrobial agents in neutropenic patients: impact on reducing the use of glycopeptides

We evaluated the impact of applying the Infectious Diseases Society of America guidelines for febrile neutropenic patients in reducing the use of glycopeptides. Forty-five prior episodes of febrile neutropenia were compared to 97 episodes seen after application of the guidelines. Glycopeptide use was reduced from 73% to 43% of episodes (P=.0008), without changes in outcome.

[Vascular graft infection by Staphylococcus epidermidis: efficacy of various perioperative prophylaxis protocols in an animal model]

A rat model was used to investigate the efficacy of levofloxacin, cefazolin and teicoplanin in the prevention of vascular prosthetic graft infection. Graft infections were established in the subcutaneous tissue of 300 male Wistar rats by implantation of Dacron prostheses followed by topical inoculation with methicillin-susceptible and methicillin-resistant S. epidermidis. The study included a group without contamination, two contaminated groups without prophylaxis, two contaminated groups with intraperitoneal levofloxacin prophylaxis (10 mg/kg), two contaminated groups with intraperitoneal cefazolin prophylaxis (30 mg/kg), two contaminated groups with intraperitoneal teicoplanin prophylaxis (10 mg/kg) and six contaminated groups with rifampin-soaked graft and intraperitoneal levofloxacin, cefazolin or te- icoplanin prophylaxis. The grafts were removed after 7 days and evaluated by quantitative culture. The efficacy of levofloxacin against the methicillin- susceptible strain did not differ from that of cefazolin or teicoplanin. Levofloxacin showed slight less efficacy than teicoplanin against the methicillin-resistant strain. The levofloxacin-rifampin combination proved to be similarly effective to the rifampin-teicoplanin combination and more effective than the rifampin-cefazolin combination against both strains. The rifampin-levofloxacin combination may be useful for the prevention of late-appearing vascular graft infections caused by S. epidermidis because it takes advantage of the good anti-staphylococcal activity of both drugs.

[Some problems of the current therapy of infective endocarditis]

AIM

To analyse clinical characteristics of endocarditis for the last 10 years, treatment difficulties and how to overcome them.

MATERIAL AND METHODS

135 patients with infectious endocarditis (IE) were examined according to the routine scheme using modern methods of diagnosis and therapy control: transthoracic and transesophageal echo-CG, test for antibiotics sensitivity of the microflora, etc. Immediate results were assessed in all the patients, some of them were followed up for maximum 5 years.

RESULTS

Last decade was marked for growing difficulties in the treatment of IE related to its polyetiology. It can be caused by such therapy-resistant microbes as Staphylococcus aureus, Pseudomonas aeruginosa, anaerobic infection, nosocomial infection, injections of narcotic drugs, etc.

CONCLUSION

Current course of IE dictates the necessity of fighting resistant microflora especially in case of nosocomial disease. Recurrences become more frequent. Indications to surgery did not change for the last decade. The best treatment results are achieved after antibacterial treatment of the valve.

[Comparative diffusion of fusidic acid, oxacillin, and pristinamycin in dermal interstitial fluid after repeated oral administration]

OBJECTIVE

The aim of this study was to use the suction bullae technique to compare skin diffusion of 3 antibiotics commonly used for skin infections (fusidic acid, oxacillin, pristinamycin) and to estimate their potential activity at the site of skin infections.

SUBJECTS AND METHODS

This comparative open study was conducted in 12 healthy volunteers using a repeated latin square experimental scheme. Antibiotic concentrations in serum and suction bullae fluid were measured by high performance liquid chromatography after 5.5 days of repeated oral administration of fusidic acid (1 g/d), oxacillin (2 g/d), and pristinamycin (2 g/d).

RESULTS

Mean antibiotic concentrations in serum and interstitial fluid (suction bullae fluid) were highest for fusidic acid with a Cmax at 91.3 +/- 23.0 mg/l and 45.5 +/- 18.0 mg/l respectively (interstitial fluid/serum ratio=49 +/- 10 p. 100). For oxacillin, Cmax was 8.3 +/- 3.6 mg/l and 0.98 +/- 0.49 mg/l (ratio 13 +/- 5 p. 100). Pristinamycin concentrations were low with a Cmax at 0.51 +/- 0.40 and 0.26 +/- 0.15 mg/l (ratio 73 +/- 57 p. 100). Comparing the area under the interstitial fluid and the serum concentration-time curves showed that the best diffusion was obtained with pristinamycin (114 +/- 61 p. 100), followed by fusidic acid (57 +/- 13 p. 100) and oxacillin (48 +/- 25 p. 100).

DISCUSSION

These data were used to calculate indicators of potential efficacy in the interstitial dermal fluid: inhibitor quotient (Cmax/MIC) and AUIC (ASC/MIC), indicator of the time antibiotic concentrations are maintained above the minimal inhibitor concentration (MIC). This showed that fusidic acid was potentially more active against all staphylococci. For streptococci, the observed interstitial concentrations of pristinamycin and of fusidic acid should theoretically inhibit streptococci A growth, but oxacillin was the most adapted antibiotic.

Comparative efficacies of liposomal amikacin (MiKasome) plus oxacillin versus conventional amikacin plus oxacillin in experimental endocarditis induced by Staphylococcus aureus: microbiological and echocardiographic analyses

Optimal treatment strategies for serious infections caused by Staphylococcus aureus have not been fully characterized. The combination of a beta-lactam plus an aminoglycoside can act synergistically against S. aureus in vitro and in vivo. MiKasome, a new liposome-encapsulated formulation of conventional amikacin, significantly prolongs serum half-life (t1/2) and increases the area under the concentration-time curve (AUC) compared to free amikacin. Microbiologic efficacy and left ventricular function, as assessed by echocardiography, were compared in animals administered either oxacillin alone or oxacillin in combination with conventional amikacin or MiKasome in a rabbit model of experimental endocarditis due to S. aureus. In vitro, oxacillin, combined with either free amikacin or MiKasome, prevented the bacterial regrowth observed with aminoglycosides alone at 24 h of incubation. Rabbits with S. aureus endocarditis were treated with either oxacillin alone (50 mg/kg, given intramuscularly three times daily), oxacillin plus daily amikacin (27 mg/kg, given intravenously twice daily), or oxacillin plus intermittent MiKasome (160 mg/kg, given intravenously, a single dose on days 1 and 4). The oxacillin-alone dosage represents a subtherapeutic regimen against the infecting strain in the endocarditis model (L. Hirano and A. S. Bayer, Antimicrob. Agents Chemother. 35:685-690, 1991), thus allowing recognition of any enhanced bactericidal effects between oxacillin and either aminoglycoside formulation. Treatment was administered for either 3 or 6 days, and animals were sacrificed after each of these time points or at 5 days after a 6-day treatment course (to evaluate for posttherapy relapse). Left ventricular function was analyzed by utilizing serial transthoracic echocardiography during treatment and posttherapy by measurement of left ventricular fractional shortening. At all sacrifice times, both combination regimens significantly reduced S. aureus vegetation counts versus control counts (P < 0.05). In contrast, oxacillin alone did not significantly reduce S. aureus vegetation counts after 3 days of therapy. Furthermore, at this time point, the two combinations were significantly more effective than oxacillin alone (P < 0.05). All three regimens were effective in significantly decreasing bacterial counts in the myocardium during and after therapy compared to controls (P < 0.05). In kidney and spleen abscesses, all regimens significantly reduced bacterial counts during therapy (P < 0.0001); however, only the combination regimens prevented bacteriologic relapse in these organs posttherapy. By echocardiographic analysis, both combination regimens yielded a significant physiological benefit by maintaining normal left ventricular function during treatment and posttherapy compared with oxacillin alone (P < 0.001). These results suggest that the use of intermittent MiKasome (similar to daily conventional amikacin) enhances the in vivo bactericidal effects of oxacillin in a severe S. aureus infection model and preserves selected physiological functions in target end organs.

[Infection prophylaxis in open leg fractures. Comparison of a dose of pefloxacin and 5 days of cefazolin-oxacillin. A randomized study of 616 cases]

THE PURPOSE OF THE STUDY

Was to compare the efficacy of a single 800 mg injection of Pefloxacin (PF) versus 2 days of cefazolin (1 gr.Q.6 H) followed by 3 days of oxacillin (1 gr.Q.8 H) in patients with an open tibial fracture and to examine the predictive factors for infection. A double-blind double dummy, multicentric, randomized trial was performed. 616 adults with an open tibial fracture requiring single-stage bone coverage were included. The end point was wound infection within 3 months.

RESULTS

Within 3 months, 21/316 patients were infected in the PF group (6.6 p. 100) versus 24/300 in the CZ-OX group (8 p. 100), the difference was not significant (95 p. 100 Cl for difference: -4.8 p. 100 to 2.1 p. 100). Twenty one strains were isolated in 18 infected patients in the PF group, and 27 in 20 patients in the CZ-OX group. Negative gram bacteria were less frequent in the PF group (10 p. 100) than in the CZ-OX group (48 p. 100), and positive gram bacteria were more frequent in the PF group (90 p. 100) than in the CZ-OX group (52 p. 100). Independent risk factors for infection were severe contamination, widespread contusion, unstable fracture, positive sample in the emergency room and at the end of surgery. Resistant infecting bacteria rate was 24 p. 100 in infected cases.

CONCLUSION

There was no difference in infection rates after surgery for open tibial fractures between a 800 mg injection of Pefloxacin and 2 days of pephazolin followed by 3 days of oxacillin. Infecting bacteria were mainly nosocomially acquired.

Reduction in cytokine release from human monocytes by modifications in cell wall structure of Staphylococcus aureus induced by subinhibitory concentrations of oxacillin

Whole bacterial cells of Staphylococcus aureus as well as purified staphylococcal peptidoglycan (PG) have been demonstrated to stimulate human monocytes to release cytokines. Hypothesising that the phenomenon of changes induced by beta-lactam antibiotics in cell-wall composition may alter the immunological properties of the intact cell wall as well as of purified cell-wall components, this study assessed whether cytokine release by human monocytes is altered if cells from strains grown in the presence or absence of sub-minimal inhibitory concentrations of oxacillin are used as stimuli. Whole bacterial cells and isolated PG from these strains, grown in the presence of oxacillin, showed a significantly reduced stimulation of tumour necrosis factor-alpha, interleukin (IL)-1beta and IL-6 release by human monocytes in a concentration-dependent fashion. The serum-induced potentiation of cytokine production by human monocytes in response to PG with modified cross-linking was also reduced. These observations may have particular relevance for staphylococcal infections, in which clinically achievable beta-lactam concentrations do not suppress staphylococcal growth yet may alter and possibly enhance virulence.

MR of staphylococcal myelitis of the cervical spinal cord

A homogeneously enhancing cervical cord lesion and multiple ring-enhancing brain lesions were detected with MR imaging in a 41-year-old woman with a staphylococcal septicemia. The brain and spinal cord lesions diminished in size after antibiotic therapy. Although no biopsy was performed, we believe, on the basis of the clinical outcome, that the spinal cord lesion represented a bacterial myelitis and that the lesion was prevented from developing into an abscess by early antibiotic therapy.

Oral antibiotic treatment of right-sided staphylococcal endocarditis in injection drug users: prospective randomized comparison with parenteral therapy

PURPOSE

To compare the efficacy and safety of inpatient oral antibiotic treatment (oral) versus standard parenteral antibiotic treatment (intravenous) for right-sided staphylococcal endocarditis in injection drug users.

PATIENTS AND METHODS

In a prospective, randomized, non-blinded trial, febrile injection drug users were assigned to begin oral or intravenous (IV) treatment on admission, before blood culture results were available. Oral therapy consisted of ciprofloxacin and rifampin. Parenteral therapy was oxacillin or vancomycin, plus gentamicin for the first 5 days. Antibiotic dosing was adjusted for renal dysfunction. Administration of other antibacterial drugs was not permitted during the treatment or follow-up periods. Bacteremic subjects having right-sided staphylococcal endocarditis received 28 days of inpatient therapy with the assigned antibiotics. Test-of-cure blood cultures were obtained during inpatient observation 6 and 7 days after the completion of antibiotic therapy, and again at outpatient follow-up 1 month later. Criteria for treatment failure and for drug toxicity were prospectively defined.

RESULTS

Of 573 injection drug users who were hospitalized because of a febrile illness and suspected right-sided staphylococcal endocarditis, 93 subjects (16.2%) had two or more sets of blood cultures positive for staphylococci; 85 of these bacteremic subjects (14.8%) satisfied diagnostic criteria for at least possible right-sided staphylococcal endocarditis (no other source of bacteremia was apparent) and entered the trial. Forty-four (oral, 19; IV, 25) of these 85 subjects completed inpatient treatment and evaluation including test-of-cure blood cultures. There were four treatment failures (oral, 1 [5.2%]; IV, 3 [12.0%]; not significant, Fisher's exact test). Drug toxicity was significantly more common in the parenterally treated group (oral, 3%; IV, 62%; P < 0.0001), consisting largely of oxacillin-associated increases in liver enzymes.

CONCLUSIONS

For selected patients with right-sided staphylococcal endocarditis, oral ciprofloxacin plus rifampin is effective and is associated with less drug toxicity than is intravenous therapy.

Cervicofacial Actinomyces viscosus infection in a Brazilian fila: a case report and literature review

A five-month-old, male Brazilian fila presented with a three-day history of a focal swelling in the left superior palpebra and a focal, subcutaneous swelling over the dorsal cervical region. Both lesions initially responded to warm compresses and a two-week course of oral amoxicillin-clavulanic acid therapy. The eyelid swelling recurred after discontinuation of the oral antibiotic therapy. The lesion was progressive and was refractory to trimethoprim-sulfadiazine therapy. Culture and sensitivity performed from a surgical biopsy sample of the eyelid mass identified Actinomyces viscosus and other bacterial genera. A combination of surgical debulkment, Penrose drain placement, and a one-month course of oral oxacillin therapy has resulted in clinical regression of the lesion at a six-month postoperative evaluation.

Antibiotic penetration into cervical discs

Antibiotics are frequently prophylactically administered in surgical procedures to reduce the incidence of infection. The penetration of antibiotics into lumbar discs has been studied with mixed results, but penetration into cervical discs has not been reviewed. In this study, we examined the penetration of two commonly used antibiotics, oxacillin and cefazolin, into cervical discs. Eighteen patients with a total of 30 discs removed were studied. Two groups, each consisting of four patients with five discs removed, received either 1 g of oxacillin or 1 g of cefazolin by a single, preoperative intravenous infusion. Two other groups, each consisting of five patients with 10 discs removed, received either 2 g of oxacillin or 2 g of cefazolin, also by a single, preoperative intravenous infusion. A blood specimen, from which serum antibiotic levels were determined, was obtained from each patient simultaneously with each discectomy. The time interval between the antibiotic infusion and discectomy/phlebotomy was also recorded. Antibiotic levels were detected in all discs removed but were quantifiable in only 12. Nine of these 12 had been exposed to cefazolin. Of these nine discs, one was from a patient who had received 1 g whereas the other eight were from patients who had received 2 g of cefazolin. This represents 80% of the removed discs exposed to 2 g of cefazolin (10 discs total) and 20% exposed to 1 g (5 discs total). The remaining three discs with quantifiable antibiotic levels had been exposed to 2 g of oxacillin, which represents 30% of the discs (10 total) exposed to that dose of oxacillin. Although cervical disc space infections are rare, they are serious.(ABSTRACT TRUNCATED AT 250 WORDS)

Antimicrobial therapy for children with chronic suppurative otitis media without cholesteatoma

This study was designed to determine the middle ear bacterial pathogens, the frequency of serum immunoglobulin deficiency and the efficacy of medical management in patients with chronic suppurative otitis media without cholesteatoma. This was an open noncomparative clinical trial performed at the National Children's Hospital, San Jose, Costa Rica, and included 186 patients older than 2 months of age with a confirmed diagnosis of chronic suppurative otitis media without cholesteatoma. Middle ear cultures and serum for immunoglobulin determinations were obtained on admission. The first 40 patients were treated only with ceftazidime and from patient 41 and up, if a Gram-positive organism was cultured, oxacillin was added to (for combined infection) or replaced ceftazidime. Parenteral antibiotics and suction twice daily were continued until three days after the middle ear became dry. Trimethropimsulfamethoxazole prophylaxis was administered during the follow-up period. Middle ear bacterial cultures were positive in 166 patients. Pseudomonas sp. (35.6%), enteric Gram-negative organisms (28.7%) and Gram-positive cocci (26%) were the most common organisms. Immunoglobulin determinations were below normal in 3 of 69 (4.3%) evaluable patients. Dryness of the ear was achieved in 174 patients (93.5%) including 130 of 139 patients treated with ceftazidime, 28 of 28 patients treated with oxacillin and 14 of 14 patients treated with ceftazidime and oxacillin. Recurrent otorrhea developed in 39 (23.4%) patients. Twice-daily canal aspiration and parenteral ceftazidime for Gram-negative organisms and/or oxacillin for Gram-positive bacteria for 3 days after dryness of the middle ear followed by prophylactic oral antimicrobials are effective for treatment of most chronic suppurative otitis media without cholesteatoma patients.

Single-dose antibiotic prophylaxis in maxillofacial surgery

The clinical efficacy of short-term antimicrobial prophylaxis with either one shot of ceftriaxone (1 g) or a course of 3 injections of a fixed combination of mezlocillin (2 g) and oxacillin (1 g) administered over 24 h was studied in a prospective randomized clinical study of 100 patients undergoing elective maxillofacial surgery. Tissue and plasma concentrations of the antibiotics were determined by high-pressure liquid chromatography in 6 tumor surgery patients from each treatment group. Statistical analysis showed the treatment group to be comparable both demographically and with respect to the types of surgery performed and the durations of the procedures. Only 1 patient in each group developed a postoperative wound infection. It is concluded that 1 g ceftriaxone given 30 min preoperatively meets the pharmacokinetic requirements for perioperative antimicrobial prophylaxis in maxillofacial surgery.

[The dynamics of the nonspecific immunity indices during the lymphotropic therapy of children with acute pyelonephritis]

The comparison of the effect obtained in children with primary acute pyelonephritis treated with lymphotropic ampiox plus lidase against oral or intramuscular ampiox showed more rapid induction of clinical remission and more pronounced tendency to normalization of immunological indices in the patients on lymphotropic ampiox. In addition, the lymphotropic route made it possible to decrease the drug dose and number of its injections which is of importance in pediatric practice. The above advantages say in favour of wide application of indirect lymphotropic therapy for pyelonephritis in children.

Activity of ampicillin-sulbactam and oxacillin in experimental endocarditis caused by beta-lactamase-hyperproducing Staphylococcus aureus

Using a rat model of aortic valve infective endocarditis, we previously found that oxacillin was equally effective against an oxacillin-susceptible strain of Staphylococcus aureus and a beta-lactamase-hyperproducing borderline oxacillin-susceptible strain of S. aureus; also, ampicillin-sulbactam was less effective than oxacillin against both isolates and at low doses was less effective against the borderline-susceptible strain than against the fully oxacillin-susceptible strain (C. Thauvin-Eliopoulos, L. B. Rice, G. M. Eliopoulos, and R. C. Moellering, Jr., Antimicrob. Agents Chemother. 34:728-732, 1990). In the present study, we extended this work, using alternative treatment schedules and additional bacterial strains. Extending treatment with low doses of ampicillin-sulbactam (500 and 250 mg/kg of body weight per day, respectively) to 6.5 days resulted in equalization of effectiveness against the previously studied strains BOSSA-1 and OSSA-1 (3.75 +/- 1.61 log10 and 4.71 +/- 1.79 log10 CFU of residual viable bacteria per g, respectively). Against the borderline oxacillin-susceptible strain BOSSA-1, increasing the sulbactam dosage from 500 to 2,000 mg/kg/day while maintaining a fixed dose of ampicillin (1,000 mg/kg/day) by continuous infusion resulted in lower bacterial counts (4.93 +/- 1.84 log10 versus 3.65 +/- 1.26 log10 CFU of residual viable bacteria per g, respectively), but this difference was of only borderline significance; differences in efficacy between the low-dose and high-dose sulbactam regimens were exaggerated when intermittent intravenous administration was used (6.19 +/- 1.90 log10 versus 3.37 +/- 1.41 log10 CFU/g, respectively; P < 0.001). However, for any individual sulbactam dosage, the model of administration (continuous versus intermittent infusion) did not affect the activity of the regimen. When additional strains were used in the model, oxacillin and ampicillin-sulbactam (1,000 plus 2,000 mg/kg/day) were equally effective against both oxacillin-susceptible and borderline oxacillin-resistant strains of S. aureus. These results support the predictions that oxacillin would be clinically effective in the treatment of infections caused by borderline oxacillin-susceptible strains of S. aureus and that, except at very low doses, ampicillin-sulbactam would also be as effective against borderline-susceptible strains as against fully oxacillin-susceptible strains of S. aureus.

[Excretion of beta-lactam antibiotics in human parotid saliva]

We investigated the penetration of beta-lactam antibiotics into parotid saliva after intravenous administration. Neither mezlocillin nor oxacillin could be detected in parotid saliva, but cefotaxime (CTX) and cefotiam (CTM) penetrated parotid saliva very well. While salivary CTM concentrations reached peak values (9.52 +/- 3.4 mg/l) within 30 min of the end of infusion, the highest CTX concentrations in parotid saliva (5.84 +/- 2.6 mg/l) were observed after 90 min. After 300 min the salivary CTM levels were below the limit of detection, while the mean CTX concentration even 360 min after the end of infusion was 2.27 +/- 1.23 mg/l. Both CTX and CTM achieve salivary concentrations that are inhibitory against the prevailing pathogens causing suppurative parotitis, and thus promise to be effective for the treatment of this disease. Furthermore, the excretion of comparatively high concentrations of both drugs into the mouth achieves a selective decontamination of the mucosal surfaces of the upper aerodigestive tract so that they are suitable for perioperative prophylaxis in head and neck surgery.

[Perioperative preventive use of antibiotics in neurosurgery. Experience with a fixed antibiotic combination of mezlocillin and oxacillin (optocillin)]

We report a retrospective account of 200 patients who have been surveyed after having undergone neurosurgical intervention. They received as perioperative antibiotic prophylaxis a combination of Mezlocillin and Oxacillin in a ratio of 2:1 (Optocillin) in their management. The clinical and bacteriological efficacy including the side effects was examined with standardisation of sterility measures in the operating theatre, careful standardised operative procedures and ward after care. No problems in wound healing were found. There was no certain evidence of side effects.

Antibiotic prophylaxis during prolonged clean neurosurgery. Results of a randomized double-blind study using oxacillin

The efficacy of oxacillin as a prophylaxis for infection was analyzed in a 27-month randomized double-blind study of 400 patients who had undergone clean neurosurgical interventions lasting longer than 2 hours. Four neurosurgeons took part in the study and 356 patients were eligible for final analysis. Among the 171 patients treated with oxacillin, there was one case of infection (0.6%), compared to nine (4.9%) of the 185 patients given a placebo. The difference between the two groups was statistically significant (p = 0.0398). This study, together with others (randomized or not), clearly demonstrates the efficacy of antibiotic prophylaxis in prolonged clean neurosurgery.

Efficacy of oxacillin and ampicillin-sulbactam combination in experimental endocarditis caused by beta-lactamase-hyperproducing Staphylococcus aureus

Optimal therapy of infections caused by borderline oxacillin-susceptible, beta-lactamase-hyperproducing Staphylococcus aureus has not been established. We used a rat model of aortic valve endocarditis to examine efficacies of antibiotic regimens against a borderline oxacillin-susceptible strain as compared with a fully susceptible S. aureus strain. Animals were treated with oxacillin alone or in combination with sulbactam or with ampicillin-sulbactam combinations at two dose levels. Infections caused by the borderline susceptible and fully susceptible strains responded equally well to oxacillin alone, with residual bacterial titers in vegetations falling to 4.8 +/- 1.6 and 4.4 +/- 1.7 (mean +/- standard deviation) log10 CFU/g, respectively. Addition of sulbactam to oxacillin (1:2) did not enhance the efficacy of oxacillin against either strain in the animal model. A high-dose regimen of ampicillin-sulbactam (2:1) yielding mean (+/- standard deviation) levels in serum of 16.8 +/- 7.4 and 9.5 +/- 1.1 micrograms/ml, respectively, proved equally effective against both strains (bacterial titers, 6.6 log10 CFU/g). However, at lower doses (8.3 +/- 2.6 and 5.9 +/- 2.4 micrograms/ml, the combination showed greater efficacy against the fully susceptible strain, with residual titers of 7.1 +/- 2.0 versus 9.0 +/- 1.6 log10 CFU/g (P less than 0.05). In vitro studies revealed that the beta-lactamase inhibitor sulbactam was also a potent inducer of staphylococcal beta-lactamase at clinically relevant concentrations. Based on this short-term in vivo therapy study, oxacillin would be predicted to be clinically effective in the therapy of infections caused by borderline oxacillin-susceptible strains of S. aureus, while the combination of ampicillin with sulbactam appears to be inferior to oxacillin alone against such infections.

[Perioperative preventive use of antibiotics in thoracic surgery--results of a controlled randomized study with optocillin]

There seems to be general agreement that antibiotic prophylaxis should be provided for patients undergoing resections of the lung. In order to obtain further information about the extent of resection beyond which this is necessary, and also to establish the type of prophylaxis that is meaningful over the long term, we carried out a controlled study involving two groups of 100 patients each. In the first group, who received minor resections, ultrashort-term prophylaxis was compared with an 0 group. We were able to show that in high-risk patients with prior pulmonary diseases, prophylaxis is indeed meaningful. In the second group of patients undergoing major resections, antibiotic prophylaxis must be provided; a one-day administration suffices, and long-term administration fails to offer any further advantages.

[Early complications following stapedectomy--surgical or conservative treatment?]

The incidence of sensorineural hearing loss after stapedectomy ranges from 0.6% to 5%. There is evidence that reparative granuloma is a major cause: most authors report that it requires urgent surgery, but this view is not universally accepted. This study analyses 14 stapedectomies that resulted in a sudden or gradual sensorineural hearing loss, often combined with vertigo, and presenting between 1 and 6 weeks after an initial hearing improvement. All patients were treated immediately with a combined infusion of an antibiotic, a corticosteroid and a plasma expander. The sensorineural hearing loss began to improve compared with pre-operative values 9 days later. Thus drug therapy might be sufficient in most cases of sensorineural hearing loss early after stapedectomy, and surgery can be restricted to patients with perilymph fistulae.

[Bacterial infections in cancer patients without neutropenia. Comparison between 2 antibiotic combinations (aztreonam and oxacillin versus cefoxitin and tobramycin)]

In the treatment of infections arisen in neoplastic patients without neutropenia, 2 antibiotic combinations (aztreonam + oxacillin vs tobramycin + cefoxitin), have been compared with regard to therapeutic effectiveness and tolerability. Twenty patients (age: 30-75) have been studied. Tolerability of both combinations was excellent. Results of this study showed a lower percentage of superinfections and a higher percentage of cure in patients treated with the combination aztreonam + oxacillin, even if the data were not statistically significant.

Oxacillin and tobramycin serum levels during cardiopulmonary bypass

Antibiotic prophylaxis in cardiac surgery is recommended to combat acquired infections caused by staphylococci and gram-negative bacilli. Prophylaxis seems effective provided blood levels are greater than minimal inhibitory concentrations (MIC). In this study, two doses of antibiotics were compared in 45 patients with normal renal function during cardiopulmonary bypass (CPB). All patients received 50 mg/kg of oxacillin. Group 1 (30 patients) also received 1 mg/kg of tobramycin, while group 2 (15 patients) received 2 mg/kg of tobramycin. Blood samples were taken after the administration of antibiotics, as well as at the onset and conclusion of CPB. Additional samples were taken before and after heparin injection before CPB, and from the arterial and venous cannulae of the bubble oxygenator during CPB. In both groups, oxacillin serum levels were constantly greater than MIC for susceptible bacteria. In group 1, tobramycin levels less than 2 micrograms/mL (MIC for most susceptible bacteria) occurred in four patients before CPB, in 14 patients at the onset of CPB, and in 19 patients at the conclusion of CPB. These low levels were not explained by heparin administration or absorption onto the CPB circuit, but were the result of hemodilution. In group 2, in which all the tobramycin levels were higher than 2 micrograms/mL, serum levels decreased from 9.9 +/- 3.4 (mean +/- SD) to 3.7 +/- 0.7 micrograms/mL throughout the procedure. Plasma creatinine did not change significantly in either group. It is concluded that in patients with normal renal function, doses as high as 50 mg/kg of oxacillin and 2 mg/kg of tobramycin may be necessary before CPB to provide adequate serum levels throughout CPB.

[In vivo bactericidal activity of an oxacillin-netilmicin combination against Staphylococcus aureus. Influence of the rhythm of netilmicin administration]

The bactericidal activity of two regimens of netilmicin (8 mg/kg/day) given intravenously once a day (od) or thrice daily (tid) both alone and in combination with oxacillin (200 mg/kg/day) was compared using a model of fibrin clots infected with a strain of Staphylococcus aureus (10(7) CFU/g) sensitive to methicillin and netilmicin (clinical isolate) and implanted subcutaneously in rabbit. This study shows that: 1) Netilmicin given alone as both single and divided doses results in early bacterial killing but does not exert a bactericidal effect after 24 hours because of a significant late increase of the number of bacterial. 2) The netilmicin-oxacillin combinations are more bactericidal at 1 h, 2 h and 24 h than oxacillin alone (P less than 0.001). 3) The oxacillin-netilmicin combination appears to be better for bacterial killing when netilmicin is given thrice daily (P less than 0.001). It is hard to draw a clinical inference from such an experimental study but it seems that 8-hour divided doses intervals should be better for administration of netilmicin than single daily dose during the acute period of staphylococcal infections.

Control of prosthetic bacterial infection: evaluation of an easily incorporated, tightly bound, silver antibiotic PTFE graft

Despite the use of prophylactic antibiotics in vascular surgery, prosthetic infection rate remains 2-5%. Antibiotics bound to vascular prostheses can control experimentally induced infection but prolonged antibacterial activity has not been achieved. This study evaluates the in vivo efficacy and antibiotic retention of an easily prepared silver-antibiotic prosthesis. Prostheses were prepared by combining silver with oxacillin or amikacin using an organic solvent. After evaporation of the solvent, the graft was left impregnated with the antibiotic complex. In vivo retention studies were performed by implanting PTFE 110Ag-oxacillin prostheses in four canine abdominal aortas. When prostheses were explanted at 1 week, mean antibiotic retention was found to be 20% of original activity, higher than the mean inhibitory concentration for Staphylococcus aureus. In three groups of five dogs, 20 X 7-mm prostheses of PTFE alone, PTFE silver-oxacillin, or PTFE silver-amikacin were implanted in the abdominal aorta and the grafts were inoculated with 10(7) S. aureus of a known bacteriophage type, in a closed retroperitoneal pocket. The animals were sacrificed at 1 week and the prostheses were excised for quantitative bacterial culture. PFTE silver-oxacillin, and PTFE silver-amikacin prostheses had 1.7 X 10(2) and 2.0 X 10(2) colonies, respectively, significantly less (P less than 0.05) than controls (1.3 X 10(6) colonies). These data suggest that antibiotic prostheses can be easily prepared without binding agents. They retain the bound antibiotic for a prolonged period and are effective in reducing graft infection in a stringent direct contamination model.

[Which antibiotics should one choose for prophylaxis in vascular surgery?]

Although the principle and duration of prophylactic antibiotic therapy in prosthetic vascular surgery are fairly widely accepted, the choice of antibiotic is still open to discussion. During two successive periods, identical groups of patients received peri-operative prophylaxis with, during period I (455 cases) oxacillin alone and during period II (537 cases) combined treatment with oxacillin and amikacin. The aim of the study was to evaluate efficacy of the association and to draw general conclusions on choice of antibiotic. The addition of amikacin reduced frequency of infection in elective operations, particularly aorto-ilio-femoral prostheses (0.5% as against 1.24%), but not in operations conducted as emergencies. In addition, frequency of infection due to BGN fell only slightly. Finally, combined therapy with oxacillin-amikacin had 2 disadvantages: impossibility of using these antibiotics for prophylaxis alone as provided for in the protocol, and its high cost. Factors of choice of antibiotic should be: efficacy against germs encountered, which can vary from year to year, rarity of toxic or side effects, good tissue diffusion, the rare need for therapeutic use and a low cost.