Antibiotic concentrations in pus and bone of children with osteomyelitis

Cefadroxil and cephalexin pharmacokinetics and pharmacodynamics in children with musculoskeletal infections

Cephalexin, a first-generation cephalosporin, is the first-line oral therapy for children with musculoskeletal infections due to methicillin-susceptible Staphylococcus aureus (MSSA). Cefadroxil, a similar first-generation cephalosporin, is an attractive alternative to cephalexin given its longer half-life. In this study, we describe the comparative pharmacokinetics (PK) and pharmacodynamics (PD) of cephalexin and cefadroxil in children with musculoskeletal infections. Children aged 6 months to 18 years with a musculoskeletal infection were enrolled in a prospective, open-label, crossover PK study and given single oral doses of cefadroxil (50-75 mg/kg up to 2,000 mg) and cephalexin (50 mg/kg up to 1,375 mg). Population PK models were developed and used for dosing simulations. Our primary PD target was the achievement of free antibiotic concentrations above the minimum inhibitory concentration (fT >MIC) for 40% of the day for MICs ≤ 4 mg/L. PK of cephalexin (n = 15) and cefadroxil (n = 14) were best described using a one-compartment, first-order absorption model, with a lag time component for cefadroxil. PK parameters were notable for cefadroxil's longer half-life (1.61 h) than cephalexin's (1.10 h). For pediatric weight bands, our primary PD target was achieved by cephalexin 25 mg/kg/dose, maximum 750 mg/dose, administered three times daily and cefadroxil 40 mg/kg/dose, maximum 1,500 mg/dose, administered twice daily. More aggressive dosing was required to achieve higher PD targets. Among children with musculoskeletal infections, oral cephalexin and cefadroxil achieved PD targets for efficacy against MSSA. Given less frequent dosing, twice-daily cefadroxil should be further considered as an alternative to cephalexin for oral step-down therapy for serious infections due to MSSA.

Have We Neglected to Study Target-Site Drug Exposure in Children? A Systematic Review of the Literature

BACKGROUND AND OBJECTIVE

Drug dosing should ideally be based on the drug concentrations at the target site, which, for most drugs, corresponds to the tissue. The exact influence of growth and development on drug tissue distribution is unclear. This systematic review compiles the current knowledge on the tissue distribution of systemically applied drugs in children, with the aim to identify priorities in tissue pharmacokinetic (PK) research in this population.

METHODS

A systematic literature search was performed in the MEDLINE and Embase databases.

RESULTS

Forty-two relevant articles were identified, of which 71% investigated antibiotics, while drug classes from the other studies were anticancer drugs, antifungals, anthelmintics, sedatives, thyreostatics, immunomodulators, antiarrhythmics, and exon skipping therapy. The majority of studies (83%) applied tissue biopsy as the sampling technique. Tonsil and/or adenoid tissue was most frequently examined (70% of all included patients). The majority of studies had a small sample size (median 9, range 1-93), did not include the youngest age categories (neonates and infants), and were of low reporting quality. Due to the heterogeneous data from different study compounds, dosing schedules, populations, and target tissues, the possibility for comparison of PK data between studies was limited.

CONCLUSION

The influence of growth and development on drug tissue distribution continues to be a knowledge gap, due to the paucity of tissue PK data in children, especially in the younger age categories. Future research in this field should be encouraged as techniques to safely investigate drug tissue disposition in children are available.

Clinical Practice Guideline by the Pediatric Infectious Diseases Society (PIDS) and the Infectious Diseases Society of America (IDSA): 2023 Guideline on Diagnosis and Management of Acute Bacterial Arthritis in Pediatrics

This clinical practice guideline for the diagnosis and treatment of acute bacterial arthritis (ABA) in children was developed by a multidisciplinary panel representing the 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 ABA, including specialists in pediatric infectious diseases and orthopedics. The panel's recommendations for the diagnosis and treatment of ABA are based upon evidence derived from topic-specific systematic literature reviews. Summarized below are the recommendations for the diagnosis and treatment of ABA 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 approach (Grading of Recommendations Assessment, Development and Evaluation) (see Figure 1). 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.

Acute infectious osteomyelitis in children: new treatment strategies for an old enemy

BACKGROUND

Acute osteomyelitis still represents a significant clinical challenge, with an increasing incidence in paediatric population. A careful assessment and a rapid diagnosis with proper timing and choice of empirical antimicrobial therapy are necessary to avoid sequelae. The initial treatment should consist of empirical antibiotic therapy, to cover the major responsible pathogens in each age group.

DATA SOURCES

We made a literature search with PubMed and Cochrane database from 2000 to 2019 in English, French, and Spanish languages using the key words "osteomyelitis, children, clinical, diagnosis, and treatment".

RESULTS

The child's clinical features, age, and the microbiological profile of the geographic area should be evaluated for diagnosis and in the choice of antibiotic treatment. Latest data suggest the administration of intravenous antibiotics for a short period, with subsequent oral therapy, according to the improvement of clinical status and inflammatory markers. For children older than 3 months, the shift to oral medications is already possible after a short course of intravenous therapy, until recovery. The timing for the shift from cefazolin to cephalexin or cefuroxime, intravenous clindamycin to oral clindamycin, and intravenous ceftriaxone + oxacillin to oral equivalents will be decided according to the improvement of clinical status and inflammatory markers. We also present the approach to osteomyelitis due to difficult pathogens, such as Methicillin-resistant Staphylococcus aureus (MRSA) and Panton-Valentine leukocidin (PVL)-positive S. aureus infections.

CONCLUSION

In this review, we present the current approach to the clinical diagnosis and management of osteomyelitis in childhood, with an update on recent recommendations, as a useful instrument to understand the rationale of antibiotic therapy.

Acute Hematogenous Osteomyelitis in Children

Background: The epidemiology of acute hematogenous osteomyelitis (AHO) in children has changed. Methods: We reviewed the current literature regarding the epidemiology, microbiology, pathogenesis, clinical presentation, diagnosis, and antimicrobial management of AHO in children. Results: Staphylococcus aureus is the most common microorganism causing pediatric AHO, followed by group A Streptococcus (GAS). AHO due to community-associated methicillin-resistant Staphylococcus aureus (MRSA) can cause severe and complicated disease. Pathogen isolation by culture is key for targeted antibiotic therapy. Polymerase chain reaction assay in tissue sample or joint fluid may enhance the yield of Kingella kingae. C-reactive protein is useful in diagnosis and monitoring the course of AHO. Magnetic resonance imaging is the preferred diagnostic imaging study for AHO. Clindamycin or vancomycin (for serious disease) is recommended for empiric therapy of suspected AHO due to MRSA depending on the geographic prevalence. Penicillinase-stable penicillins or first-generation cephalosporins are preferred antibiotics to treat methicillin-sensitive S aureus (MSSA) infection. Beta-lactam agents are the drugs of choice for treating AHO due to K kingae, GAS, or Streptococcus pneumoniae. For uncomplicated AHO due to MSSA, a short parenteral antibiotic course followed by oral therapy for a minimum total duration of 3-4 weeks is adequate. Complicated AHO due to MRSA may warrant prolonged therapy with surgical intervention. Conclusion: Given the evolution of pathogens, the variability in clinical presentations and course ranging from simple to complex disease, and response to treatment, the management of AHO continues to evolve and warrants an individualized, multidisciplinary approach.

Epidural abscesses

Until recently epidural abscess was considered a rare, almost theoretical, complication of central nerve block, but anecdotal reports suggest that this is no longer the case. Thus a review of the risk factors, pathogenesis, clinical features and outcome of this condition is appropriate, the primary aim being to make recommendations on best anaesthetic practice to minimize the risk of this serious complication. A search of EMBASE(c), PUBMED(c) and MEDLINE(c) databases from 1966 to September 2004 was performed using several strategies, supplemented by reference list screening. Spontaneous epidural abscess is rare, accounting for 0.2-1.2 cases per 10,000 hospital admissions per year. Estimates of the incidence after central nerve block vary from 1:1,000 to 1:100,000. Risk factors (compromised immunity, spinal column disruption, source of infection) are present in the majority of patients, whether the condition is spontaneous or associated with central nerve block. Presentation is vague, fever and back pain usually preceding neurological deficit. Diagnosis requires a high index of suspicion and modern imaging techniques. Treatment involves early surgical drainage to prevent permanent deficit and high dose parenteral antibiotics chosen with bacteriological advice. Primary prevention depends on proper use of full aseptic precautions. Epidural abscess can be a catastrophic consequence of central nerve block. Early diagnosis will minimize permanent damage, but primary prevention should be the aim. There is a need for a large survey to indicate the true incidence to better inform the risk-benefit ratio for central nerve block.

Pharmacodynamics and the prediction of efficacy in short-course antibiotic therapy: pediatric studies to validate the model

Short-course antibiotic therapy for specific pediatric infections allows the clinician to minimize toxicities related to antibiotic exposure, to limit antibiotic resistance, and to improve compliance and cost without compromising microbiologic efficacy. Future studies of short-course therapy in children should address the pharmacokinetics of antibiotic exposure to the pathogen at the site of infection, the pharmacodynamics of pathogen eradication, and the many host factors involved in clinical and microbiologic outcomes. By using a mathematic model that integrates all important variables, one may be able to predict the probability of a cure with short-course therapy for each pathogen, antibiotic, site of infection, and host interaction.

Acute hematogenous osteomyelitis in children: recognition and management

Acute hematogenous osteomyelitis is most common in children and has the potential to cause life-long musculoskeletal deformities. Most cases are caused by Staphylococcus aureus. Haemophilus influenzae type b (Hib) is now rare in countries that routinely use the Hib vaccine. Although magnetic resonance imaging is the preferred modality in localized disease, scintigraphy is often preferred as the first line of investigation because it helps to clarify the location of infection and exclude the presence of multifocal disease. Where the presentation is typical, there is no underlying disease, there is a low prevalence of community-acquired methicillin-resistant S. aureus (CA-MRSA), and there is a good response to antibacterial therapy, a diagnostic bone aspirate or biopsy is not necessary. The first-line antibacterial choice in most circumstances is a beta-lactamase-resistant penicillin. If CA-MRSA is suspected, the first-line options include clindamycin, the addition of an aminoglycoside or, rarely, vancomycin. In most patients, the total duration of therapy can be substantially shorter than the traditional 6 weeks, and oral therapy can be commenced after a brief course of intravenous antibacterials. We recommend 3 days of intravenous therapy followed by 3 weeks of high-dose oral antibacterials, provided there is no underlying illness, the presentation is typical and acute, and there has been a good response to treatment initially. Any deviation from this requires more intensive confirmation of the diagnosis (with imaging and/or biopsy or aspiration), and prolongation of intravenous therapy and total duration of treatment. Close monitoring and follow-up for at least 2 years are advised to detect complications.

Spinal epidural abscesses in children: a 15-year experience and review of the literature

We reviewed medical records and laboratory and diagnostic evaluations for 8 pediatric patients with spinal epidural abscesses who were treated during the last 15 years at our institution. Staphylococcus aureus was isolated from 5 of 8 epidural abscesses, including 2 abscesses with methicillin-resistant S. aureus. Unusual isolates were group B Streptococcus in a patient with chronic vesicouretral reflux associated with the posterior urethral valves and Aspergillus flavus in a patient with acute myelogenous leukemia. An analysis incorporating our results and a review of the English-language literature about abscesses in children and adults revealed differences related to age. Abscesses in children were more posterior in epidural location, had greater spinal column extension, and were associated with more favorable clinical outcomes than were abscesses in adults. Magnetic resonance imaging is the diagnostic procedure of choice; however, radionuclide bone scans should be considered for associated distant osteomyelitis in children. Prompt diagnosis and combined medical and surgical treatment remain the cornerstones for the prevention of adverse outcomes.

Should probenecid be used to reduce the dicloxacillin dosage in orthopaedic infections? A study of the dicloxacillin-saving effect of probenecid

Reduction in the dosage of dicloxacillin from 500 mg to 250 mg 3 times a day would mean lowering of costs and less side-effects in orthopaedic infections. In this cross-over study, the serum concentrations of dicloxacillin were measured in 9 patients after administration of dicloxacillin 500 mg 3 times a day (dicloxacillin 500 mg) and after co-administration of 250 mg dicloxacillin and 250 mg probenecid 3 times per day (dicloxacillin 250 mg+probenecid 250 mg). Concentrations were measured every hour after the tablet intake. The mean maximum serum concentrations of dicloxacillin were 17.1 micrograms/ml (dicloxacillin 500 mg) and 12.2 micrograms/ml (dicloxacillin 250 mg+probenecid 250 mg), respectively (P < 0.05). Serum concentrations above 3 micrograms/ml were obtained during 285 min. in both regimes, but the individual variations were biggest during in the dicloxacillin 250 mg+probenecid 250 mg treatment. Serum concentrations above 5 micrograms/ml were in mean measured during 228 min. (dicloxacillin 500 mg) and 190 min. (dicloxacillin 250 mg+probenecid 250 mg), respectively (P < 0.05). The clinical significance of these findings is being discussed. In theory, treatment with dicloxacillin 250 mg+probenecid 250 mg may be as sufficient as dicloxacillin 500 mg.

Pharmacokinetics and tissue concentrations of cefazolin in pediatric patients undergoing gastrointestinal surgery

Limited information is available on the pharmacokinetics and tissue penetration of cefazolin in pediatric patients. Nine children (age 0.8-10 years) undergoing gastrointestinal operations were studied. A single dose of cefazolin, 15-26 mg/kg was given i.v. over 2-3 min at the time of induction of anaesthesia. Multiple (5-8) blood samples were collected during the operative procedure and in the recovery room. Tissue samples from the rectus abdominis muscle were obtained at the time of incision, during surgery, and at closure. The concentration of cefazolin was measured by a high performance liquid chromatographic method. Peak serum concentrations of cefazolin ranged from 85.8-269.4 mcg/ml. Serum and tissue concentrations at incision were 50.5-169.9 mcg/ml and 1.8-29.7 mcg/g; at closure the serum and tissue concentrations ranged from 17.3-60.9 mcg/ml and 1.19-29.70 mcg/g, respectively. Total clearance, apparent distribution volume, and elimination half-life of cefazolin were 1.43 +/- 0.54 ml/min/kg, 0.08 +/- 0.03 l/kg, and 1.68 +/- 0.55 h respectively. Tissue concentrations of cefazolin were maintained above its minimum inhibitory concentrations against common susceptible pathogens. Hence, the current dosing regimen of cefazolin is adequate to protect against infection in pediatric patients undergoing gastrointestinal surgery.

Vancomycin concentrations in infected and noninfected human bone

Concentrations of vancomycin in bones of 14 patients undergoing total hip arthroplasty (group 1) and 5 patients with osteomyelitis (group 2) were studied. Group 1 received vancomycin, 15 mg/kg intravenously, 1 h prior to anesthesia. Group 2 received doses adjusted to achieve peak levels in serum of 20 to 30 micrograms/ml and trough levels of less than 12 micrograms/ml; bone specimens were collected during surgical debridement. The specimens were pulverized and eluted into phosphate buffer, and the supernatants were analyzed for vancomycin content by fluorescence polarization immunoassay. In group 1, vancomycin was detectable in all cancellous specimens with a mean concentration of 2.3 +/- 4.0 micrograms/g (range, 0.5 to 16 micrograms/g); 10 of 14 cortical specimens had detectable vancomycin; the mean cortical concentration was 1.1 +/- 0.8 micrograms/g (range, not detectable to 2.6 micrograms/g). In group 2, vancomycin was detectable in only two of five cortical bone specimens (mean concentration, 5.9 +/- 3.5 micrograms/g). Cancellous bone was obtained in one patient; the vancomycin concentration was 3.6 micrograms/g. In most patients the vancomycin levels in bones were higher than the MIC for susceptible staphylococci following single prophylactic doses. In the few infected patients studied, penetration was variable and deserves further study.

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.

Comparison of concentrations of rifampin and a new rifamycin derivative, DL 473, in canine bone

Constant-infusion experiments were performed in 14 dogs to determine the penetration into bone of rifampin and a new C-3 substituted rifamycin, DL 473. The drugs were assayed in cortical bone and medulla from tibia-femur and cortical and cancellous bone from rib. After identical dosage, the concentrations of DL 473 appeared to be higher, except in the medulla, although the serum concentrations of rifampin were almost twice as high as those for DL 473. The concentrations of both drugs in all bone areas were several times higher than their minimum inhibitory concentrations against pathogenic Staphylococcus aureus.

Bone penetration of antibiotics

Osteomyelitis is caused by bacterial pathogens and, less frequently, by other infectious agents. Treatment of osteomyelitis should include a course of antimicrobial therapy with a batericidal agent. This therapy should be directed at the causative bacteria isolated by bone biopsy and culture, not by wound swab cultures above the infected bone. The bactericidal agent should be demonstrated effective against the organism isolated from bone and should penetrate the bone in sufficient concentrations. Many studies have assessed bone penetration of antimicrobials, but methodological problems must be addressed. Penicillins, cephalosporins, aminoglycosides, erythromycin, lincomycin and clindamycin, and metronidazole have all been evaluated.

Treatment of osteomyelitis and septic arthritis with cefamandole

Fourteen patients with bone and joint infections caused by a variety of bacterial pathogens were treated with intravenous cefamandole, 4 to 12 g/day; ten received additional therapy with 2 g/day of cefaclor and one with 2 g/day of cephalexin. Ten of 14 patients were cured. Of those cured, infecting pathogens had minimal inhibitory concentrations of cefamandole of 4 micrograms or less/ml. Of those who were not cured, two had recurrent infections that had not responded to other previously administered antibiotics, one had a mixed infection with resistant strains, and one had positive bone cultures five months after a favorable clinical response. Peak and valley cefamandole serum concentrations were 48.0 to 173.0 micrograms/ml and 23.4 micrograms or less/ml, respectively. Synovial fluid concentrations were 11.1 to 16.7 micrograms/ml and bone concentrations were 0.2 to 20.4 micrograms/g. Adverse effects included leukopenia in one and hepatic enzyme elevations in four patients. Cefamandole, with and without cefaclor, was efficacious in therapy of bone and joint infections caused by susceptible organisms.

Long-term follow-up of ambulatory management of osteomyelitis

Over four years, 50 patients with osteomyelitis (32 classified as acute and 18 as subacute or chronic disease) were treated with oral antibiotics in an ambulatory setting. The profile of clinical and laboratory parameters, including etiologic agents, was similar to previous series. Forty-eight patients initially received parenteral drugs, mean duration 14 days (range 0-36). Oral agents administered at home included cephalosporins, clindamycin, dicloxacillin, penicillin VK, amoxicillin, and sulfa-trimethoprim. Mean duration of total therapy was 53.2 days (range 16-365). In follow-up, ranging from 12 to 60 months (mean 35), relapses occurred in one patient with acute and one with chronic disease. Both responded to oral treatment. No residual infection has resulted, although clinical and radiographic sequelae remain in six more patients initially termed subacute or chronic. Long-term follow-up of patients receiving high-dose oral antibiotic therapy for osteomyelitis due to sensitive organisms confirms the safety and efficacy of this mode of treatment and the feasibility of ambulatory management. The outcome after oral therapy is equivalent to that following parenteral therapy. Patients with subacute or chronic disease have a significantly poorer prognosis despite a milder initial illness and longer course of therapy.

Penetration of cefazolin into normal and osteomyelitic canine cortical bone

The ability of cefazolin to cross the capillary membrane and its concentrations in the interstitial fluid spaces were studied in normal and osteomyelitic canine bone. The maximum extraction after a single capillary passage and the net extraction after 3 min, determined with triple-tracer indicator-dilution techniques, demonstrated that cefazolin readily traversed the capillaries of normal and osteomyelitic bone. These studies suggest that the altered pathophysiology of osteomyelitic tissue and the complex diffusional characteristics of cefazolin enhanced the ability of this agent to cross the endothelial cells lining the capillaries of osteomyelitic bone. Volume of distribution studies demonstrated that cefazolin was distributed in the plasma and interstitial fluid spaces of normal cortical bone. Although these spaces were increased 330 and 941% in osteomyelitic tissue, the distribution of cefazolin increased proportionally. There was a direct correlation between the calculated concentrations of cefazolin in the interstitial fluid spaces of normal and osteomyelitic cortical bone and the simultaneous serum levels in animals in which a steady-state equilibrium had been achieved. These studies suggest that a physiological barrier or concentration gradient for cefazolin does not exist in normal or osteomyelitic bone. Cefazolin can cross the capillary membranes of bone and achieve bactericidal concentrations in the interstitial fluid space of normal and osteomyelitic tissue.

Treatment of Nongonococcal bacterial septic arthritis

Septic arthritis carries significant morbidity and mortality, necessitating prompt, appropriate therapy with joint fluid aspiration, intravenous antibiotics, and occasionally, surgical intervention. The initial choice of antimicrobial agent is guided by the results of synovial fluid gram stain, by identification of the pathogenesis of the primary focus, or by epidemiologic factors. Adequacy of therapy is assessed by serial synovial fluid white blood cell counts and by determining antimicrobial concentrations in the joint space. The goal of treatment is a clinically normal and sterile joint. Factors that may affect antimicrobial joint penetration include the degree of joint tissue inflammation, the degree of drug protein binding, and the chemical characteristics of the drug. Perhaps most important in determining the extent of joint penetration are factors that may affect serum antibiotic concentrations, for example, dose, route of administration, volume of distribution, but rate of elimination.

Acute haematogenous osteomyelitis and septic arthritis in childhood. A 10-year review and follow-up

Seventy-three children, who were admitted to hospital during the period 1965-1976 with osteomyelitis or septic arthritis, were included in a retrospective study as well as a clinical and radiological follow-up. Ten cases of osteomyelitis occurred during the neonatal period and about half of the cases of osteomyelitis and septic arthritis occurred before the age of 2 years. Staph. aureus was the dominating pathogen isolated and half of the strains were penicillin-resistant. The group of children with osteomyelitis who were given early treatment, i.e. within 1 week, against penicillin-resistant Staph, aureus had a higher clinical cure rate after 1 month (0.01 < P < 0.025) compared with the rest of the children. Five children developed recurrent or chronic osteomyelitis. An early follow-up in 69 children 1-11 years after the disease showed that none had any complaints or invalidity. However, one patient with neonatal septic arthritis presented severe dysplasia and subluxation of the hip and four children with osteomyelitis had severe, but asymptomatic, radiological changes.

Oral antibiotic therapy for skeletal infections of children. II. Therapy of osteomyelitis and suppurative arthritis

Antimicrobial regimens consisting of a brief initial period of parenteral therapy followed by oral therapy were investigated in infants and children with suppurative bone and joint disease. There were 30 patients with acute hematogenous disease (19 osteomyelitis; three osteoarthritis; eight arthritis) and five with subacute or chronic osteomyelitis. Disease was due to Staphylococcus aureus in 26, Hemophilus influenzae in five, streptococci in three, and S. aureus plus Streptococcus pyogenes in one patient. Pus was removed by surgical drainage or needle aspiration. Oral therapy was monitored by assay of antibiotic concentration and bactericidal activity in serum. Adjustments in dosage were made when necessary to assure a peak serum bactericidal titer of at least 1:8. One patient progressed to chronic osteomyelitis but all other patients with acute disease responded well. Oral therapy provides increased patient comfort and decreases the risk of nosocomial infection associated with prolonged intravenous therapy. It should be carried out only under carefully monitored conditions in hospital to assure compliance and adequacy of serum bactericidal activity.