AB0752 CHRONIC RECURRENT MULTIFOCAL OSTEOMYELITIS: A SINGLE-CENTER CASE SERIES

Background:

Chronic recurrent multifocal osteomyelitis (CRMO) is a chronic autoinflammatory disease that primarily affects the skeleton of children and adolescents in the absence of an infectious etiology[1]. CRMO lesions presentation varies widely ranging from episodic bone pain to growth disturbance; lytic and sclerotic bone lesions can be found on X-ray, however magnetic resonance imaging is very useful for evaluating the extent of disease and follow-up [2].

Objectives:

To report demographic, clinical and laboratory characteristics and response to therapy in a single center Italian cohort of CRMO patients.

Methods:

We reviewed retrospectively the clinical records of seven patients affected by CRMO diagnosed between 2008 and 2019 at rheumatologic service of South Tyrol region in Italy.

Results:

We identified 7 patients with CRMO, 4 were female patients, median age of onset of symptoms was seven years. Median delay in diagnosis was seven months; all patients had bone pain as initial symptom and 6 patients presented joint swelling. Median number of lesions was two; all patients had a recurrent pattern, 4 patient had multifocal distribution and 5 had appendicular skeleton involvement. None of our patients had antinuclear antibodies or HLA-B27 positivity. Mean erythrocyte sedimentation rate was 52 mm/h and C-reactive protein 1,96 mg/dL. Regarding other organs involvement one patient presented palmoplantar pustulosis, one psoriatic arthritis and one psoriasis guttata; three patient referred familiarity for psoriasis. Histopathological diagnosis was confirmed in 3 patients. NSAIDs were used in six patients, methotrexate in two patients and bisphosphonates in 6 patients. Among biological DMARDs Adalimumab was used in two patients, one patient was treated subsequently with Secukinumab and Ustekinumab. 3 patients achieved remission (Table 1).

Table 1.

Demographic, clinical and laboratory characteristics of patients with chronic recurrent multifocal osteomyelitis.

Total (n=7)Demographics Female (%)4 (57) Age at disease onset, years, median (range)7 (6-24) Delay in diagnosis, months, median (range)7 (2-14) Follow-up, months, median (range)69 (11-151)Initial symptoms Bone pain, n (%)7 (100) Swelling, n (%)5 (71) Limp, n (%)3 (43) Fever, n (%)1 (14)Clinical features Number of lesions, median (range)2 (1-10) Axial skeleton involvement, n (%)2 (29) Appendicular skeleton involvement, n (%)5 (71)Distribution of involvement Femur, n (%)3 (43) Radius/ulna, n (%)2 (29) Humerus, n (%)1 (14) Tibia/fibula, n (%)5 (5) Tarsal bones, n (%)1 (14) Others, n (%)3 (43)Laboratory tests Hemoglobin, g/dL, mean ± SD13.1±0.6 Leukocytes × 103/mm3, mean ± SD8.48 ±1.7 Platelets × 103/mm3, mean ± SD384±130 Erythrocyte sedimentation rate mm/h, mean ± SD52±37 C-reactive protein, mg/dL, mean ± SD1.96±2.35 Positive antinuclear antibodies, n (%)0 (100) HLA-B27 positive, n (%)0 (100)Comorbidities Any type of autoimmunity, n (%)2 (29) Others, n (%)3 (43) Histological confirmation, n (%)3 (43)Treatment NSAIDs, n (%)6 (86) Glucocorticoids, n (%)0 (0) Bisphosphonates, n (%)6 (86) TNF blocking agents, n (%)2 (29) Biological DMARDs, n (%)1 (4) Methotrexate, n (%)2 (29) Antibiotics, n (%)3 (43) Reached remission, n (%) 3 (43)

Conclusion:

CRMO remains a rare diagnosis. From our experience most of the patients had delay in diagnosis, laboratory tests showed mild elevation of inflammatory parameters, was found association with psoriatic arthritis and psoriasis, remission was achieved with combination of bisphosphonate and immunosuppressive therapy in less than half of the cohort

References:

[1]A. Taddio, F. Zennaro, S. Pastore, e R. Cimaz, «An Update on the Pathogenesis and Treatment of Chronic Recurrent Multifocal Osteomyelitis in Children», Pediatr. Drugs, vol. 19, n. 3, pagg. 165–172, giu. 2017.

[2]S. J. Menashe et al., «The Many Faces of Pediatric Chronic Recurrent Multifocal Osteomyelitis (CRMO): A Practical Location- and Case-Based Approach to Differentiate CRMO From Its Mimics», J. Magn. Reson. Imaging JMRI, pag. e27299, ago.2020

Disclosure of Interests:

None declared

Plasma and soft tissue pharmacokinetics of ceftolozane/tazobactam in healthy volunteers after single and multiple intravenous infusion: a microdialysis study

OBJECTIVES

To investigate ceftolozane/tazobactam pharmacokinetics (PK) in plasma and interstitial space fluid (ISF) of muscle and subcutaneous tissue and establish a population PK model.

METHODS

Eight healthy volunteers received four IV doses of 1000/500 mg ceftolozane/tazobactam q8h in a prospective, open-labelled PK study. ISF concentration-time profiles were determined via in vivo microdialysis up to 8 h post-dose and efficacy of unbound ceftolozane and tazobactam was estimated using the time above MIC (%ƒT>MIC) and time above threshold concentration (%T>CT), respectively. A population PK model was established by merging derived plasma and soft tissue PK data.

RESULTS

Ceftolozane reached %ƒT>MIC values of 100% in plasma, muscle and subcutaneous ISF for Enterobacteriaceae and 87%, 89% and 87%, respectively, for Pseudomonas aeruginosa. Tazobactam %T>CT was 21%, 22% and 21% in plasma, muscle and subcutaneous ISF, respectively. Plasma protein binding was 6.3% for ceftolozane and 8.0% for tazobactam. Multiple-dose ceftolozane AUC0-8 ISF/plasma ratios were 0.92 ± 0.17 in muscle and 0.88 ± 0.18 in subcutis, and tazobactam ratios were 0.89 ± 0.25 in muscle and 0.87 ± 0.21 in subcutis, suggesting substantial soft tissue penetration.

CONCLUSIONS

Tazobactam %T>CT values were distinctly below proposed target values, indicating that tazobactam might be underdosed in the investigated drug combination. However, ISF/unbound plasma ratios of ceftolozane and tazobactam support their use in soft tissue infections. A plasma and soft tissue PK model adds important information on the PK profile of ceftolozane/tazobactam. Further investigations in patients suffering from wound infections are needed to confirm these findings.

Colistin Reduces LPS-Triggered Inflammation in a Human Sepsis Model In Vivo: A Randomized Controlled Trial

The previously described anti-endotoxin effect of colistin has not been investigated in humans yet. We performed a randomized, double-blind, placebo-controlled crossover trial to determine the degree of colistin-driven modulation of inflammatory response in blood of lipopolysaccharide (LPS)-challenged healthy volunteers in a human endotoxemia model. After a single intravenous dose of 2.5 million IU colistin methanesulfonate, interleukin (IL)-6, IL-8, tumor necrosis factor alpha (TNF-α), and IL-1β concentrations as well as other biomarkers of inflammation such as C-reactive protein, differential leukocyte counts, and body temperature were measured up to 24 h postdose. Colistin significantly decreased the inflammatory cytokine response to LPS in blood of healthy volunteers. This effect was most evident for IL-6, IL-8, and TNF-α. This study is the first to confirm the anti-endotoxin effect of colistin in humans in vivo. Further studies might increase our knowledge on the interaction between colistin and the effectors of the immune system.

Differential in vivo activation of monocyte subsets during low-grade inflammation through experimental endotoxemia in humans

Human monocytes are a heterogeneous cell population, which can be divided into a classical (CD14++CD16−), a non-classical (CD14+CD16+), and an intermediate (CD14++CD16+) subset. We hypothesized that low-grade inflammation may differentially affect monocyte subsets. We used a human lipopolysaccharide (LPS) infusion model to mimic low-grade inflammation to identify, which monocyte subsets are preferentially activated under these conditions. Monocyte subsets were identified by staining for CD14 and CD16, activation status of monocytes was analyzed by staining for CD11b and a novel in situ mRNA hybridization approach to detect IL-6 and IL-8 specific mRNA at the single-cell level by flow cytometry. After LPS challenge, cell numbers of monocyte subsets dropped after 2 h with cell numbers recovering after 6 h. Distribution of monocyte subsets was skewed dramatically towards the intermediate subset after 24 h. Furthermore, intermediate monocytes displayed the largest increase of CD11b expression after 2 h. Finally, IL-6 and IL-8 mRNA levels increased in intermediate and non-classical monocytes after 6 h whereas these mRNA levels in classical monocytes changed only marginally. In conclusion, our data indicates that the main responding subset of monocytes to standardized low-grade inflammation induced by LPS in humans is the CD14++CD16+ intermediate subset followed by the CD14+CD16+ non-classical monocyte subset. Circulating classical monocytes showed comparably less reaction to LPS challenge in vivo.

Simultaneous assessment of the pharmacokinetics of a pleuromutilin, lefamulin, in plasma, soft tissues and pulmonary epithelial lining fluid

BACKGROUND

Lefamulin is a pleuromutilin antibiotic under evaluation for the treatment of bacterial infections, including respiratory tract infections. Currently, there are no high-quality pharmacokinetic data on drug tissue concentrations of lefamulin available.

METHODS

A single dose of intravenous lefamulin (150 mg) was given to 12 healthy men. The registered EudraCT number for this study was 2010-021938-54. Lefamulin concentrations were simultaneously measured in plasma, skeletal muscle tissue, subcutaneous adipose tissue and epithelial lining fluid (ELF) over 24 h, and corresponding pharmacokinetic parameters were calculated. Microdialysis was used to measure unbound lefamulin concentrations in skeletal muscle tissue and subcutaneous adipose tissue, which were similar to unbound lefamulin concentrations in plasma. Bronchoalveolar lavage was performed 1, 2, 4 and 8 h post-dose to determine lefamulin concentrations in ELF.

RESULTS

Unbound lefamulin levels showed a 5.7-fold higher exposure in ELF compared with that in plasma, demonstrating good penetration to the target site.

CONCLUSIONS

Lefamulin may be an addition to the therapeutic armamentarium for the treatment of infections. Simultaneous measurements of unbound drug concentration can guide target attainment for future therapeutic trials.

Target site antimicrobial activity of colistin might be misestimated if tested in conventional growth media

Cation-dependent inhibition of antimicrobial activity was reported for polymyxin antibiotics. Ca(2+) and Mg(2+) concentrations recommended by the Clinical and Laboratory Standards Institute (CLSI) for the supplementation of Müller-Hinton broth (MHB) are markedly lower than interstitial space fluid (ISF) concentrations in vivo. Hence, it was speculated that the antimicrobial activity of colistin might be overestimated if tested using conventional cation-adjusted MHB. The antimicrobial activity of colistin against n = 100 clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae and Escherichia coli (n = 25 each) was evaluated by broth microdilution and, for selected isolates, by time-kill curves, in MHB without cations (MHB(ONLY)), MHB supplemented with 25 mg/L Ca(2+) and 12.5 mg/L Mg(2+) according to CLSI recommendations (MHB(CLSI)), and in MHB adjusted to 50 mg/L Ca(2+) and 20 mg/L Mg(2+) simulating ISF concentrations (MHB(ISF)). The minimum inhibitory concentration (MIC) values of colistin against the vast majority of isolates of both P. aeruginosa and A. baumannii increased significantly with higher cation concentrations. The susceptibility of K. pneumoniae isolates to colistin did not show significant changes between cation-supplemented media, while the MICs of E. coli decreased with ascending cation concentrations. These findings were confirmed in time-kill studies, where colistin killing against P. aeruginosa 1514 and A. baumannii 1485 declined with increasing cation concentrations. Contrarily, the killing of selected concentrations of colistin against K. pneumoniae 15 and E. coli 16 was enhanced in the presence of increasing cation concentrations. The present data suggest that the clinical antimicrobial activity of colistin might be misestimated in vitro if tested in conventional growth media.

Pgp-mediated interaction between (R)-[11C]verapamil and tariquidar at the human blood-brain barrier: a comparison with rat data

Using positron emission tomography (PET) imaging we assessed, in vivo, the interaction between a microdose of (R)-[(11)C]verapamil (a P-glycoprotein (Pgp) substrate) and escalating doses of the Pgp inhibitor tariquidar (3, 4, 6, and 8 mg/kg) at the blood-brain barrier (BBB) in healthy human subjects. We compared the dose-response relationship of tariquidar in humans with data obtained in rats using a similar methodology. Tariquidar was equipotent in humans and rats in its effect of increasing (R)-[(11)C]verapamil brain uptake (expressed as whole-brain volume of distribution (V(T))), with very similar half-maximum-effect concentrations. Both in humans and in rats, brain V(T) approached plateau levels at plasma tariquidar concentrations >1,000 ng/ml. However, Pgp inhibition in humans led to only a 2.7-fold increase in brain V(T) relative to baseline scans (before administration of tariquidar) as compared with 11.0-fold in rats. The results of this translational study add to the accumulating evidence that there are marked species-dependent differences in Pgp expression and functionality at the BBB.

The third-generation P-glycoprotein inhibitor tariquidar may overcome bacterial multidrug resistance by increasing intracellular drug concentration

OBJECTIVES

The use of efflux pump inhibitors may be a powerful strategy to overcome transporter-mediated bacterial multidrug resistance. In the present study, we set out to investigate the potency of tariquidar, a third-generation P-glycoprotein inhibitor in clinical development, for overcoming bacterial resistance towards ciprofloxacin.

METHODS

Staphylococcus aureus 29213 (SA29213) and S. aureus 1199B (SA1199B), which overexpresses the multidrug transporter NorA, as well as Pseudomonas aeruginosa 27853 and Stenotrophomonas maltophilia BAA-85, which expresses SmeDEF, were exposed to ciprofloxacin in the presence and absence of tariquidar or, for comparative reasons, elacridar. Activity of both P-glycoprotein inhibitors was evaluated by determination of MICs and time-kill curves, and by quantification of uptake of ciprofloxacin into bacterial cells.

RESULTS

Activity of tariquidar and elacridar was comparable for S. aureus strains, and both dose-dependently increased susceptibility towards ciprofloxacin. Highest effects were observed for SA1199B, where the addition of tariquidar resulted in a 10-fold reduction of the ciprofloxacin MIC, while no effect was observed for P. aeruginosa. For S. maltophilia, elacridar but not tariquidar improved susceptibility. Uptake of [14C]ciprofloxacin and modification of susceptibility showed significant correlations (r=0.89, P<0.0001). Tariquidar had no intrinsic activity against any strain tested.

CONCLUSIONS

We conclude that tariquidar has potent inhibitory effect against certain bacterial efflux pumps in vitro. Their high activity at clinically achievable concentrations might yield this class of drugs promising for future applications in infectious diseases.