Use of the serum bactericidal titer to assess the adequacy of oral antibiotic therapy in the treatment of acute hematogenous osteomyelitis

What Is the Appropriate Dose, Route, and Duration of Antibiotic Therapy for Pediatric Acute Hematogenous Osteomyelitis (AHO)? I Wish I Knew

Treatment of pediatric AHO requires antibiotic/surgical management. Considerable clinical experience exists, but with current knowledge of antibiotic pharmacokinetics and pharmacodynamics, recommendations for dosages for old or new antibiotics should be based on current standards for drug development whenever possible.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America: 2021 Guideline on Diagnosis and Management of Acute Hematogenous Osteomyelitis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute hematogenous osteomyelitis (AHO) in children was developed by a multidisciplinary panel representing Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA). This guideline is intended for use by healthcare professionals who care for children with AHO, including specialists in pediatric infectious diseases, orthopedics, emergency care physicians, hospitalists, and any clinicians and healthcare providers caring for these patients. The panel's recommendations for the diagnosis and treatment of AHO are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of AHO in children. The panel followed a systematic process used in the development of other IDSA and PIDS clinical practice guidelines, which included a standardized methodology for rating the certainty of the evidence and strength of recommendation using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. A detailed description of background, methods, evidence summary and rationale that support each recommendation, and knowledge gaps can be found online in the full text.

Probenecid effects on cephalexin pharmacokinetics and pharmacodynamics in healthy volunteers

OBJECTIVES

We evaluated the effects of probenecid on the Pharmaco Kinetics (PK) and pharmacodynamics (PD) of oral cephalexin in healthy volunteers.

METHODS

Cephalexin 1000 mg was administered orally to 11 healthy volunteers following a standardized meal, with and without probenecid 500 mg orally, on two separate days one week apart. Total plasma concentrations of cephalexin and probenecid over a 12 h period were measured by liquid chromatography tandem mass spectrometry. Standard pharmacokinetic measures and contemporary PK/PD targets were compared.

RESULTS

Probenecid increased the mean (95% CI) cephalexin area under the concentration-time curve (AUC_0-∞) 1.73-fold (1.61-1.85, p < 0.0001), peak concentration 1.37-fold (1.16-1.58, p < 0.01), time to peak concentration 1.45-fold (1.1-1.8, p < 0.01)_, and half-life 1.33-fold (1.03-1.62, p < 0.05). The effects resulted in clinically meaningful increases in the probability of PK/PD target attainment (PTA). As an example, the PTA of total concentrations above the minimum inhibitory concentration required to inhibit methicillin-susceptible Staphylococcus aureus isolates (MIC ≤ 8 mg/L) for 70% of a 6 h dose interval approached 100% for cephalexin + probenecid while for cephalexin alone it was <15%.

CONCLUSIONS

Probenecid prolonged and flattened the plasma concentration-time curve, enhancing the probability of attaining PK/PD targets. Co-administration of probenecid may expand the clinical benefits of oral cephalexin.

Probenecid and food effects on flucloxacillin pharmacokinetics and pharmacodynamics in healthy volunteers

OBJECTIVES

To measure the effect of probenecid, fasting and fed, on flucloxacillin pharmacokinetic and pharmacodynamic endpoints.

METHODS

Flucloxacillin 1000 mg orally was given to 11 volunteers alone while fasting ('flucloxacillin alone'), and with probenecid 500 mg orally while fasting ('probenecid fasting') and with food ('probenecid fed'). Flucloxacillin pharmacokinetic and pharmacodynamic endpoints were compared.

RESULTS

Probenecid, fasting and fed, increased free plasma flucloxacillin area under the concentration-time curve (zero to infinity) ∼1.65-fold (p < 0.01) versus flucloxacillin alone. Probenecid fed prolonged time to peak flucloxacillin concentrations ∼2-fold versus the other two regimens (p < 0.01). Probenecid fasting or fed increased free flucloxacillin concentrations exceeding 30%, 50% and 70% of the first 6, 8 and 12 h post-dose by 1.58- to 5.48-fold compared with flucloxacillin alone. As an example of this pharmacodynamic improvement, the probability of target attainment of free concentrations above the minimum inhibitory concentration for Staphylococcus aureus (0.5 mg/L) for 50% of a 6-hour dose interval was > 80% for flucloxacillin plus probenecid (fasting or fed) and < 20% for flucloxacillin alone.

CONCLUSIONS

Probenecid increased flucloxacillin exposure, with predicted pharmacodynamic effects greater than pharmacokinetic effects because of the altered shape of the concentration-time curve. Probenecid may improve the applicability of oral flucloxacillin regimens.

Systematic review of duration and choice of systemic antibiotic therapy for acute haematogenous bacterial osteomyelitis in children

AIM

Historically, children with acute osteomyelitis received 4-6 weeks of parenteral antibiotics; however, evidence to guide optimal duration of therapy is limited. This study aims to summarise the available evidence on the duration and choice of antimicrobial therapy for acute haematogenous osteomyelitis in children.

METHODS

We systematically reviewed the literature on children with acute osteomyelitis to determine if shorter durations of antibiotic treatment compared with protracted treatment gave different cure rates. We also analysed studies for choice of antibiotics to determine differences in success rates. Randomised controlled trials, cohort studies, case-control studies and case series were eligible for inclusion.

RESULTS

We identified six randomised controlled trials, three of which addressed duration of antibiotic use and three choice of antibiotic for acute osteomyelitis in children. We found 28 observational studies, 20 of which focused on duration and 22 of which allowed analysis of choice of antibiotic. A range of therapy durations and types of antibiotics were assessed. Only one small study looked at treatment of neonates.

CONCLUSIONS

The quality of evidence on antibiotic treatment for acute osteomyelitis is limited, allowing only weak (GRADE 2B) recommendations. Our review suggests that early transition from intravenous to oral therapy, after 3-4 days in patients responding well, followed by oral therapy to a total of 3 weeks may be as effective as longer courses for uncomplicated acute osteomyelitis. This recommendation does not apply to neonates.

[Intravenous antibiotic therapy for acute hematogenous osteomyelitis in children: short versus long course]

The aim of this study was to evaluate the results of two antibiotic therapy protocols for osteomyelitis with different durations of intravenous treatment. This was a prospective randomized study of children treated for acute hematogenous osteomyelitis. Patients in group 1 (G1) received 7 days of intravenous antibiotics, whereas patients in group 2 (G2) received 14 days. Treatment was deemed effective if there were no signs of chronic osteomyelitis at the last follow-up. Fifty-three patients were included in the study (G1=27, G2=26). After a mean follow-up of 11.5 months, none of the patients in either group showed signs of chronic osteomyelitis. In conclusion, a shortened treatment of 7 days of intravenous antibiotic therapy is as effective as a longer treatment.

Sequential antibiotic therapy: Effective cost management and patient care

The escalating costs associated with antimicrobial chemotherapy have become of increasing concern to physicians, pharmacists and patients alike. A number of strategies have been developed to address this problem. This article focuses specifically on sequential antibiotic therapy (sat), which is the strategy of converting patients from intravenous to oral medication regardless of whether the same or a different class of drug is used. Advantages of sat include economic benefits, patient benefits and benefits to the health care provider. Potential disadvantages are cost to the consumer and the risk of therapeutic failure. A critical review of the published literature shows that evidence from randomized controlled trials supports the role of sat. However, it is also clear that further studies are necessary to determine the optimal time for intravenous to oral changeover and to identify the variables that may interfere with the use of oral drugs. Procedures necessary for the implementation of a sat program in the hospital setting are also discussed.

Haematogenous acute and subacute paediatric osteomyelitis: a systematic review of the literature

A delay in the diagnosis of paediatric acute and subacute haematogenous osteomyelitis can lead to potentially devastating morbidity. There are no definitive guidelines for diagnosis, and recommendations in the literature are generally based on expert opinions, case series and cohort studies. All articles in the English literature on paediatric osteomyelitis were searched using MEDLINE, CINAHL, EMBASE, Google Scholar, the Cochrane Library and reference lists. A total of 1854 papers were identified, 132 of which were examined in detail. All aspects of osteomyelitis were investigated in order to formulate recommendations. On admission 40% of children are afebrile. The tibia and femur are the most commonly affected long bones. Clinical examination, blood and radiological tests are only reliable for diagnosis in combination. Staphylococcus aureus is the most common organism detected, but isolation of Kingella kingae is increasing. Antibiotic treatment is usually sufficient to eradicate the infection, with a short course intravenously and early conversion to oral treatment. Surgery is indicated only in specific situations. Most studies were retrospective and there is a need for large, multicentre, randomised, controlled trials to define protocols for diagnosis and treatment. Meanwhile, evidence-based algorithms are suggested for accurate and early diagnosis and effective treatment.

Polymyxin Combination Therapy and the Use of Serum Bactericidal Titers in the Management of KPC-Producing Klebsiella pneumoniae Infections: A Report of 3 Cases

Management of patients with KPC-harboring Enterobacteriaceae has become a significant and challenging scenario. We report three cases of KPC-producing Klebsiella pneumoniae bacteremia that were successfully treated using combination therapy with polymyxin B and other antimicrobials. Serum bactericidal titers were determined and provided additional clinical guidance in the management of such patients.

Acute haematogenous osteomyelitis in children: is there any evidence for how long we should treat?

PURPOSE OF REVIEW

Despite diagnostic and therapeutic advances, acute haematogenous osteomyelitis in children continues to cause significant morbidity and disease burden. The molecular epidemiology of causal organisms has wide geographic variation, but regardless of cause children often require several weeks of inpatient parenteral antibiotic therapy. This review focuses on antibiotic treatment and length of antibiotic therapy.

RECENT FINDINGS

Currently there is no international and little local consensus regarding the route or duration for antibiotic treatment of acute haematogenous osteomyelitis in children. Although there are encouraging data from review papers and case series, no randomized controlled trial has been conducted to show good evidence for shorter courses of parenteral antibiotic treatment. Prospective studies show effective treatment for a wide variety of antibiotic agents, but there are few comparative studies. Overall treatment for 4-6 weeks is considered standard therapy, but the laboratory or clinical parameters that would determine the decision to switch to oral therapy remain undefined.

SUMMARY

Evidence-based data about the route and duration of intravenous antibiotic treatment for acute haematogenous osteomyelitis in children are still limited to observational and retrospective studies. A randomized controlled trial will provide much needed data.

[Pharmacokinetics and pharmacodynamics of antimicrobial therapy used in child osteoarticular infections]

The progress in the knowledge of antibiotic action mechanisms have led to determine phamacodynamic/pharmacokinetic (PK/PD) parameters predictive of antibiotic efficacy in bacterial infections. According to the antibiotic compound, the implicated bacterial specie, the localization of the infection, the severity of the disease, these parameters could vary. The PK/PD parameters described in this paper focus only on blood compartment and S. aureus, (main bacteria implicated in bone and joint tissue infections). All beta-lactamase resistant beta-lactam compounds given by IV route, if they are prescribed at the good dosage and frequency, fulfill these PK/PD parameters. In contrast, by oral route, M penicillins and cefuroxime-axetil should not be considered as acceptable regimens. Only amoxicillin-clavulanate and some first generation cephalosporin compounds fulfill the PK/PD parameters predictive of clinical efficacy if S. aureus strains are methicillin susceptible and dosages of cephalosporins are increased. Clindamycin is a very interesting alternative, if the strains are susceptible to macrolides.

Osteomyelitis in children

Osteomyelitis is one of the more common invasive bacterial infections in children leading to hospitalization and prolonged antibiotic administration. Over the past decade, increasing microbial virulence, diminishing antibiotic susceptibility, and advances in diagnostic molecular microbiology and imaging techniques have led to changes in the clinical management of children with suspected osteomyelitis, which are reviewed in this article.

Management of septic arthritis

Septic arthritis in children remains a serious disease with the potential for significant systemic and musculoskeletal morbidity. Staphlococcus aureus is the most common cause of bone and joint infections in all age groups. Microbial invasion of the synovial space occurs typically results from hematogenous seeding. Diagnosis in neonates and young infants can be difficult since the clinical signs are much less specific in these age groups. Early diagnosis by needle aspiration of the affected joint and prompt initiation of appropriate antimicrobial therapy in conjunction with drainage of the affected joint is critical to avoid destruction of the articular cartilage and prevent disability. Septic arthritis in infants and children should always be managed by a pediatrician in close consultation with an orthopedic surgeon. Empiric antibiotic regimens should always include adequate anti-staphylococcal coverage. Antibiotic treatment should be started with appropriate doses of intravenous antibiotics. Switch to oral antibiotic therapy can be made when patient demonstrates clinical improvement. A minimum of 3-4 weeks of therapy is recommended. Close follow-up is warranted to monitor the growth of the affected limb until skeletal maturity.

Treatment of chronic osteomyelitis in children resistant to previous therapy

Patients admitted to the authors' institution with tibial osteomyelitis between 1978 and 1998 were reviewed. The purpose of this study was to determine the incidence, etiology, treatment, and outcome in chronic pediatric tibial osteomyelitis. The authors describe their treatment of chronic osteomyelitis in children resistant to previous therapeutic modalities. Thirty patients were identified with a mean age of 8.5 years at diagnosis. Mean age at admission was 9.6 years, indicating more than a 1-year duration of disease. Follow-up averaged 2.3 years. Patients underwent 97 procedures, averaging 3.2 procedures per patient. Hospital stay ranged from 2 weeks to 18 months, with an average stay of 4.7 months. Seventy-seven percent of patients were culture-positive, and 78% of positive cultures identified Staphylococcus aureus as the causative pathogen. Eighty percent of patients had a good outcome, 13% had a fair outcome, and there were no poor results. Patients with large tibial defects obtained good results with both tibiofibular synostosis and Ilizarov distraction osteogenesis. The authors describe the only reported group of pediatric patients successfully treated using Ilizarov bone transport for bony tibial defects due to osteomyelitis.

Shorter courses of parenteral antibiotic therapy do not appear to influence response rates for children with acute hematogenous osteomyelitis: a systematic review

BACKGROUND

Acute hematogenous osteomyelitis (AHO) occurs primarily in children and is believed to evolve from bacteremia followed by localization of infection to the metaphysis of bones. Currently, there is no consensus on the route and duration of antimicrobial therapy to treat AHO.

METHODS

We conducted a systematic review of a short versus long course of treatment for AHO due primarily to Staphylococcus aureus in children aged 3 months to 16 years. We searched Medline, Embase and the Cochrane trials registry for controlled trials. Clinical cure rate at 6 months was the primary outcome variable, and groups receiving less than 7 days of intravenous therapy were compared with groups receiving one week or longer of intravenous antimicrobials.

RESULTS

12 eligible prospective studies, one of which was randomized, were identified. The overall cure rate at 6 months for the short course of intravenous therapy was 95.2% (95% CI = 90.4 - 97.7) compared to 98.8% (95% CI = 93.6, 99.8) for the longer course of therapy. There was no significant difference in the duration of oral therapy between the two groups.

CONCLUSIONS

Given the potential increased morbidity and cost associated with longer courses of intravenous therapy, this finding should be confirmed through a randomized controlled equivalence trial

Epidemiology and outcome of osteomyelitis in the era of sequential intravenous-oral therapy

BACKGROUND

There has been little recent information on the epidemiology and outcome of childhood osteomyelitis since the era of sequential intravenous-oral antibiotic therapy.

METHODS

Retrospective chart review.

OBJECTIVE

To review the recent experience and outcome of osteomyelitis in children.

RESULTS

Between 1984 and 1996 we identified 146 patients with osteomyelitis. Decreased limb use and fever were the most common presenting symptoms, and tenderness was the most common sign. Staphylococcus aureus was the most common causative organism, and Haemophilus influenzae was not identified after 1990. Bone biopsies or aspirates were superior (83%) to blood cultures (32%) in yielding organisms. 99mTc bone scan was the most sensitive imaging test (94%). Lack of use of anti-teichoic acid titers and serum bactericidal titers did not adversely affect outcome. The median duration of intravenous antibiotic therapy was 11 days, with a median duration of total antibiotics of 38 days. Complications occurred in 6.6% of patients.

CONCLUSION

S. aureus remains the most important cause of osteomyelitis. Despite inconsistent use of tests for diagnosis and management and use of sequential intravenous-oral therapy, the overall outcome remains excellent.

Septic arthritis in children

Because of its seriousness, septic arthritis should be considered early in the differential diagnosis of any child presenting with joint inflammation. Physicians who care for children should be aware of the early signs and symptoms of septic arthritis and be aggressive about establishing the diagnosis so that treatment is not delayed. Early orthopedic consultation and a low threshold for performing arthrocentesis are prudent. Prolonged and appropriate antimicrobial therapy is warranted to achieve optimal results.

Simplified treatment of acute staphylococcal osteomyelitis of childhood. The Finnish Study Group

OBJECTIVE

Recommendations on treatment of acute staphylococcal osteomyelitis of children, based mostly on retrospective analyses, comprise surgical drainage, up to 6 weeks fo antimicrobials guided by the erythrocyte sedimentation rate, and the possibility of switching to the oral route only if monitoring of serum bactericidal titer is guaranteed. A prospective study was conducted to test whether the treatment could be simplified.

DESIGN

Fifty pediatric cases of acute Staphylococcus aureus osteomyelitis were randomized to receive 150 mg/kg/day of cephradine divided in four doses, or 40 mg/kg/day in four doses of clindamycin. The treatment was initiated intravenously, but switched to oral administration mostly within 4 days, using the same doses. The peak antimicrobial serum inhibitory titer or bactericidal titer was not measured. The course of illness was monitored by blood leukocytes, erythrocyte sedimentation rate, and serum C-reactive protein. The follow-up was extended to 1 year posthospitalization.

SETTING

Eight tertiary pediatric-orthopedic hospitals in Finland.

MAIN OUTCOME MEASURE

Full recovery and remaining healthy at least 12 months from hospital discharge.

RESULTS

The lower and upper extremities were affected in 72% and 8% of patients, respectively. No surgery at all or needle aspiration only was performed in 62% and drilling in 38%. C-reactive protein and the sedimentation rate normalized within 9 days and 29 days, respectively. X-ray changes developed in 68% but had no prognostic significance. The mean hospitalization time was 11 days, and the total duration of antimicrobials was 23 days. No failure has occurred nor have long-term sequelae been observed in any patient.

CONCLUSIONS

Treatment of pediatric acute staphylococcal osteomyelitis can be simplified and costs reduced by keeping surgery at a minimum, shortening hospitalization and the course of antimicrobials, switching quickly to the oral route, and not monitoring serum bactericidal activity.

Continuation of antibiotic therapy for serious bacterial infections outside of the hospital

Many children hospitalized with serious bacterial infections are candidates for either home oral antibiotic therapy or outpatient parenteral antibiotic therapy. Outpatient antibiotic therapy offers the potential for excellent medical treatment, reduced costs, and improved quality of life for ill children. However, cost considerations must not override good medical judgment. Certain children simply are not candidates for outpatient therapy because of the seriousness of their infection, poor compliance, lack of intravenous access, or poor social situation. In addition, although the few published studies to date all show that outpatient antibiotic therapy is effective, there is further need for properly designed clinical trials to evaluate the efficacy and safety of outpatient antibiotic therapy for serious bacterial infections in children.

Switch therapy: the theory and practice of early change from parenteral to non-parenteral antibiotic administration

OBJECTIVE: The idea behind switch therapy is that antibiotic treatment should be changed from the parenteral to another suitable route (usually oral) as soon as the patient's condition allows. This option is cost-effective in terms of both acquisition costs (oral antibiotics are less expensive than their parenteral counterparts) and indirect costs, and patients may be discharged home sooner. This not only releases hospital beds but is also popular with patients and has other advantages. There are relatively few formal clinical trials, most often using oral third-generation cephalosporins and fluoroquinolones; these agents at present seem the most appropriate to use after parenteral antibiotics have been stopped (usually after 2 to 3 days). Logistic aspects are important, and close collaboration is required between pharmacists, physicians and microbiologists. Further trials are needed in specific patient groups and with other antibiotic regimens to validate the efficacy of switch therapy.

Pharmacokinetics of sparfloxacin and serum bactericidal activity against pneumococci

Sparfloxacin, a new fluorinated quinolone, exhibits higher in vitro activity against pneumococci than do ciprofloxacin and ofloxacin. Since up to 30% of cases of pneumococcal pneumonia are associated with bacteremia, and since an increasing percentage of pneumococci are resistant against penicillin, we studied the serum bactericidal activity of sparfloxacin against pneumococci in eight healthy, middle-aged volunteers. Pharmacokinetics in serum and urine after a 400-mg oral dose of sparfloxacin were comparable to those described by other authors. Inhibitory and bactericidal activities in serum were measured for four pneumococcal isolates representing penicillin-susceptible (one isolate), intermediately resistant (two isolates), and highly resistant (one isolate) strains. Geometric mean inhibitory titers ranged between 1:2.4 and 1:6.3 and bactericidal titers ranged between 1:1.3 and 1:3.6 during a time period of 1 to 6 h after drug intake. Although such titers were not sufficient to predict a clinical response based on previous pharmacodynamic studies using quinolone antibiotics, data obtained with volunteers may only partially reflect the clinical situation in which a rise of humoral antibodies directed against pneumococcal antigens may help to reinforce the bactericidal action of the antibiotic.

How far can the paediatric patient with a serious infection be managed as an outpatient?

Serious infections are often treated by paediatricians with parenteral antibiotics. Traditionally, patients receiving parenteral treatment are hospitalized. However, hospitalization has a grave negative impact on the child. The present article discusses the potential benefits of outpatient treatment of serious paediatric infections, together with the logistic approach for such treatment. Outpatient treatment for serious paediatric infections may provide an excellent medical treatment that both reduces costs and increases the patient's quality of life.

Serious bacterial infections in children. When can outpatient treatment be used?

Several studies now support outpatient treatment of many serious bacterial infections in children, such as periorbital or buccal cellulitis, urinary tract infection, pneumonia, and abscess. However, an appropriate agent, that is, a third-generation cephalosporin with a long half-life, must be available and its effectiveness properly researched. In addition, children must be free of other illnesses and able to ingest fluids and maintain hydration, and their parents must be willing and able to cooperate with an outpatient treatment regimen. Family physicians can maintain the close patient and family contact needed to facilitate this form of therapy.

Neonatal group B streptococcal osteomyelitis and suppurative arthritis. Outpatient therapy

ORAL ANTIBIOTIC TREATMENT of acute staphylococcal osteomyelitis in toddler and school-age children has proven a cost-effective and efficacious alternative to intravenous therapy. 1,2 Oral antibiotic regimens, however, have not been carefully studied in neonatal osteomyelitis. We recently treated an infant with oral antibiotics for multifocal group B streptococcal (GBS) osteomyelitis and suppurative arthritis and report our experience.

Duration of antimicrobial therapy for acute suppurative osteoarticular infections

From 1974 to 1983, inclusive, 274 children with acute suppurative osteoarticular infections were treated with antibiotic regimens that were shorter than usually recommended. The median duration of antibiotic treatment for acute suppurative arthritis caused by staphylococci, streptococci, Haemophilus influenzae type b, gram-negative cocci, or other gram-negative bacteria was 23, 16, 16, 15, and 22 days, respectively. For acute osteomyelitis caused by staphylococci, streptococci, H influenzae, or other gram-negative bacteria the median duration of antibiotic therapy was 24, 23, 17, and 22.5 days, respectively. Osteoarthritis usually had to be treated for about a month. 180 patients received large dosages of oral antimicrobials after clinical stabilisation with intravenous treatment, the median duration of intravenous therapy being about a week (range up to 7 weeks). 99% of patients underwent needle aspiration for diagnostic reasons. 36%, 71%, and 63% of the patients with acute suppurative arthritis, osteomyelitis, and osteoarthritis, respectively, underwent incision and drainage. Recurrence occurred in 4 patients with acute osteomyelitis (3.8% of cases). There was no recurrence of arthritis.

Serum bactericidal test

The serum bactericidal test represents one of the few in vitro tests performed in the clinical microbiology laboratory that combines the interaction of the pathogen, the antimicrobial agent, and the patient. Although the use of such a test antedates the antimicrobial era, its performance, results, and interpretation have been subject to question and controversy. Much of the confusion concerning the serum bactericidal test can be avoided by an understanding of the various factors which influence bactericidal testing. In addition, the methodologic aspects of the serum bactericidal test have recently been addressed and should place this test on firmer ground. New information on the clinical utility of this test is becoming available; additional data are needed to establish more clearly the usefulness of the serum bactericidal test in specific infections. Such clinical trials from multiple centers will enable firmer recommendations for the future use of the serum bactericidal test.

Dosage guidelines for the use of vancomycin based on its pharmacokinetics in infants

The purpose of this study was to characterize the pharmacokinetics of vancomycin and to develop optimal dosage guidelines in infants. Thirteen infants between the ages of 13 to 183 days were enrolled. All had been born prematurely, and average gestational age, postconceptional age, and actual body weight were 29.8 weeks, 38.2 weeks, and 2.1 kg respectively. Multiple blood samples were obtained from each patient after 72 h of therapy. Serum inhibitory and bactericidal titres were determined for peak and trough samples. There were good correlations between total body clearance of vancomycin and both postconceptional age (r = 0.86) and actual body weight (r = 0.87). This information was used to develop vancomycin dosage guidelines in premature infants. The regression line for vancomycin daily dosage requirements vs postconceptional age may be useful for determining initial dosage recommendations. There were also good correlations between vancomycin serum concentrations and serum inhibitory and cidal titres. Peak and trough concentrations in the therapeutic range (peak, 25-35 micrograms/ml; trough, 5-10 micrograms/ml) corresponded to titres of greater than or equal to 1:8 and 1:2 to 1:8 respectively. Based on these data we suggest the following dosage guidelines for vancomycin: 10 mg/kg 12 hourly for 30-34 weeks postconceptional age and less than 1.2 kg actual body weight; 10 mg/kg 8 hourly for 30-42 weeks postconceptional age and greater than 1.2 kg actual body weight; 10 mg/kg 6 hourly for greater than 42 weeks postconceptional age and greater than 2.0 kg actual body weight. Thus, doses which are lower than currently recommended are needed for infants born prematurely.(ABSTRACT TRUNCATED AT 250 WORDS)

Multicenter collaborative evaluation of a standardized serum bactericidal test as a predictor of therapeutic efficacy in acute and chronic osteomyelitis

Forty-eight episodes of osteomyelitis, 30 acute and 18 chronic, were evaluated in a prospective multicenter collaborative study to determine whether a standardized serum bactericidal test could predict outcome of infection. All centers used a microdilution test method that defined the recognized important test variables, including inoculum size, culture medium, dilution technique, incubation time, method of subculture, and bactericidal endpoint. In patients with acute osteomyelitis, peak serum bactericidal titers had no predictive value; however, trough titers of 1:2 or greater accurately predicted cure, whereas trough titers of less than 1:2 predicted therapeutic failure. In patients with chronic osteomyelitis, peak serum bactericidal titers of 1:16 or greater and trough titers of 1:4 or greater accurately predicted cure, whereas peak titers of less than 1:16 and trough titers of less than 1:2 accurately predicted failure. It is concluded that this standardized serum bactericidal test provides good prognostic information in patients with osteomyelitis, and it is recommended that patients with acute osteomyelitis have serum bactericidal titers of 1:2 or greater at all times and that patients with chronic osteomyelitis have serum bactericidal titers of 1:4 or greater at all times.

Plasma concentration following oral administration of di- and flucloxacillin in infants and children

The bioavailability of commercial liquid preparations of di- and flucloxacillin was compared in infants and children. The plasma concentrations following a dose of 12.5 mg/kg were equal within the two age groups. Infants 0-1 months old, however, demonstrated a better absorption than older children.

Current concepts in the management of infections in bones and joints

Significant changes have taken place in the epidemiology, microbiology and antibiotic therapy of bone and joint infections. Gram-negative bacilli have become an increasingly common cause, particularly in immunocompromised patients; anaerobes have been implicated in osteomyelitis associated with metallic foreign bodies; and there is increasing use of oral antibiotic regimens following an initial period of parenteral treatment. Gram-negative bacilli and anaerobes are found in polymicrobial non-haematogenous osteomyelitis (e.g. post-traumatic, post-surgical), but Staphylococcus aureus remains the most common cause of acute haematogenous osteomyelitis, with streptococci and Haemophilus influenzae responsible for most of the remainder. A precise microbiological diagnosis is essential. Diagnosis is based on Gram stain and culture of bone biopsies or aspirated pus, or on blood cultures. Specimens should be obtained before starting therapy. Any suspected primary foci of infection should be cultured. Parenteral antibiotics are given as soon as specimens are obtained, and continued for at least 3 weeks. The common causative organisms in septic arthritis are the same as in osteomyelitis, with the addition of Neisseria gonorrhoeae in young, sexually active adults. As in osteomyelitis, a precise microbiological diagnosis is of paramount importance, ideally by joint aspiration for cell count, Gram stain, biochemical analysis and culture, or by blood cultures. Optimum therapy is with antibiotics, repeated therapeutic aspirations, and resting the joint. Parenteral antibiotics should be started as soon as specimens are obtained and continued for 4 to 6 weeks. Gonococcal arthritis, however, can be treated successfully with 1 week of antibiotics. When treatment of either osteomyelitis or septic arthritis is continued with oral antibiotics, serum antibiotic concentrations or serum bactericidal levels are mandatory to ensure adequate absorption.

Technical aspects and clinical correlations of the serum bactericidal test

A review of the studies using 50% human serum as a diluent for the serum bactericidal test has shown correlations with patient outcome. Human serum used as diluent of the patient's serum appears to be essential because of high protein binding of some antibiotics. An inoculum of 10(5)-10(6) bacteria/ml and a bactericidal criteria of 99.9% killing are technical aspects that have gained popularity. Careful timing of serum collection for the assay is important. Neither the macrotube nor microtiter techniques are entirely satisfactory. The latter method, however, has the advantage of being more reproducible than the macrotube method, less cumbersome and requiring less serum. Preliminary guidelines for performing and interpreting the test are provided. Future research should be directed toward making the microtiter technique more sensitive for identifying antibiotic tolerance, developing effective methods to eliminate the need for human serum as a diluent and obtaining more clinical correlations.

Acute hematogenous staphylococcal osteomyelitis: evaluation of cloxacillin therapy in an animal model

A reproducible avian model of acute hematogenous staphylococcal osteomyelitis was used to investigate various aspects of antibiotic therapy using a single antibiotic, cloxacillin. The effects of both delaying antibiotic administration and increasing the frequency of antibiotic administration on the outcome of the disease were evaluated. Following bacterial inoculation, a delay in commencing therapy for 4 d in comparison to 1 d significantly reduced the likelihood of a favourable outcome. An increase in the frequency of antibiotic administration from once to 4 times daily resulted in significant improvement in the recovery rate of chickens. Whilst repeated antibiotic administration controlled the systemic effects of the disease and improved the clinical status of chickens, the local bone lesion was not always sterilized. The role of antibiotic therapy in acute hematogenous osteomyelitis is discussed in relation to these findings.

Oral therapy for orthopedic infections in children and adults

Literature and clinical experience in the treatment of both adult and pediatric osteomyelitis by oral antibiotics is reviewed. Antibiotics achieving adequate penetration into joint fluid and bone are listed. Particular discussion is given to penicillins, cephalosporins, and non-β-lactam antibiotics. Techniques for monitoring therapeutic effectiveness and patient compliance are noted.

The usefulness of the serum bactericidal test in orthopedic infections

The serum bactericidal test is proposed as a means to monitor the effectiveness of antibiotic therapy in orthopedic cases. Preliminary results of a multicenter study of the test in osteomyelitis suggest that trough titers yield the best indication of successful treatment.

Significance of serum bactericidal activity in gram-negative bacillary bacteremia in patients with and without granulocytopenia

Serum bactericidal activity was determined routinely in 89 patients with gram-negative bacillary bacteremia, 79 of whom were analyzed because they had granulocyte counts either below 100/mm3 or above 1,000/mm3. A peak (one hour after the administration of the antibiotics) serum bactericidal titer of 1:8 or more in non-granulocytopenic patients or 1:16 or more in severely granulocytopenic patients could be correlated with a favorable clinical response, in 98 percent (44 of 45) (p less than 0.0001) and 87 percent (20 of 23), (p less than 0.001) respectively. Granulocytopenic patients required a statistically significantly higher serum bactericidal activity for a favorable response. Serum bactericidal activity appears to be a useful and simple method to monitor antibiotic treatment in gram-negative bacillary bacteremia, especially when combination therapy is used.

Pitfalls in diagnosis of osteomyelitis in children with sickle cell disease

The cases of three children with unusual features of osteomyelitis and sickle cell disease are presented. Two children had salmonella osteomyelitis, one with a recurrence 1.5 years after adequate intravenous therapy. In the second, the bone scan was negative despite verified disease. The causative organism in the third case was Staphylococcus aureus, and there was extensive bone involvement of the radius without symptoms, but with a positive bone scan. It is recommended that the possibility of osteomyelitis be entertained in a child with sickle cell disease whenever there are symptoms and/or objective findings referrable to bone. Radionuclide scans, when used in timely fashion, can assist in the diagnosis, but confirmation can best be achieved by the recovery of microorganisms through blood culture and/or bone aspirate. The choice, dosage, and duration of antibiotic therapy should be determined by causative organisms and by serologic titers.

Cost-effective antibiotic prescribing

Antibiotics are often misused, resulting in a high frequency of adverse effects, emergence of drug-resistant organisms, and excessive costs. The high cost of antibiotics is currently receiving the greatest attention. Considerable cost savings can be achieved by appropriate prescribing of antibiotics for patients receiving these drugs prophylactically as well as for those with established infections. This article cites specific examples of how cost-effective antibiotic prescribing practices can realize substantial cost savings without any diminished quality in patient care.