The role of Gram-negative bacteria in skin and soft tissue infections

Recurrence of skin and soft tissue infections: identifying risk factors and treatment strategies

PURPOSE OF REVIEW

Recurrent skin and soft tissue infections (RSSTIs) are challenging for the clinicians due to morbidity and healthcare-related costs. Here, we review updates on risk factors and management.

RECENT FINDINGS

RSSTIs rates range between 7 and 45%. Local and systemic conditions can favour RSSTIs, with comorbidities such as obesity, diabetes, cancer and immunosuppressive disease becoming increasingly relevant. Streptococcus spp . and Staphylococcus aures (including methicillin resistant, MRSA) are the leading causative pathogens of RSSTIs, but also Gram-negative bacteria and polymicrobial infection should be considered. To prevent recurrences, treatment of underlying predisposing factor, complete source control and appropriate antibiotic therapy are crucial. Antibiotic prophylaxis for recurrent erysipelas and decolonization for MRSA carriers demonstrated some advantages, but also long-term loss of efficacy and possible adverse effects. Clinical score and patients risk stratification could be useful tools to target prophylaxis and decolonization strategies. To reduce hospitalization rates and costs, outpatient oral and parenteral antibiotic therapy (OPAT) and long-acting antibiotics are being implemented.

SUMMARY

Management of RSSTIs requires both preventive interventions on modifiable risk factors and pharmacological strategies, with a patient tailored approach.

Target-site cefiderocol pharmacokinetics in soft tissues of healthy volunteers

BACKGROUND

Cefiderocol may potentially be used to treat skin and soft tissue infections (SSTIs). However, the pharmacokinetics of cefiderocol in human soft tissues have not yet been determined. The objective of the present PK study was to investigate whether target-site concentrations of cefiderocol are sufficiently high for the treatment of SSTIs.

METHODS

In this pharmacokinetic study, a single intravenous dose of 2 g cefiderocol was administered to eight healthy male volunteers. Drug concentrations were determined in plasma, muscle and subcutis over 8 h. Free plasma concentrations were calculated using the plasma protein binding determined with ultrafiltration. Free tissue concentrations were obtained using microdialysis. Penetration ratios were calculated as AUC0-8h_free_tissue/AUC0-8h_free_plasma. A population pharmacokinetic model was developed, and the probability of target attainment (PTA) was determined using Monte Carlo simulations.

RESULTS

Cefiderocol showed good tissue penetration, with mean penetration ratios ± standard deviation of 0.99 ± 0.33 and 0.92 ± 0.30 for subcutis and muscle, respectively. Cefiderocol pharmacokinetics in plasma were best described with a two-compartment model, and tissue concentrations were described by scaling the tissue concentrations to concentrations in the peripheral compartment of the plasma model. For a thrice-daily regimen with 2 g doses intravenously infused over 3 h, PTA was ≥90% for MIC values up to 4 mg/L, both based on free plasma and soft tissue pharmacokinetics.

CONCLUSIONS

This study indicates that a dose of 2 g cefiderocol achieves concentrations in plasma considered sufficient for treating relevant bacterial species. Assuming a comparable PK/PD target for soft tissues, sufficiently high concentrations would also be achieved in soft tissues.

Ibuprofen as an adjuvant to conventional antimicrobials and essential oil compounds against skin pathogens

AIMS

Antimicrobial resistance continues to be a growing concern, resulting in increased use of drug combinations. Antibiotic adjuvants are an emerging strategy that may potentiate an antibiotics efficacy. Ibuprofen's polypharmacological properties have been investigated for their antimicrobial and host-modulating potential. This study aimed to investigate the potential of a novel multidrug combination involving ibuprofen, essential oil compounds (EOCs), and conventional antimicrobials against skin pathogens.

METHODS AND RESULTS

The minimum inhibitory concentrations of ibuprofen, conventional antimicrobials, and EOCs were determined and then combined and tested against 14 (reference and clinical) skin pathogens. The cytotoxicity was analysed using the MTT assay, whilst the anti-inflammatory effects were evaluated using lipopolysaccharide activated RAW264.7 murine macrophages. Four pairwise (Ibuprofen and antibiotic) (ΣFIC 0.33-0.50) and three triple (Ibuprofen and antibiotic with EOC) (ΣFIC 0.44-0.47) synergistic antimicrobial interactions were identified. These combinations demonstrated cell viability of 77.59%-100%. No combination significantly reduced nitric oxide production.

CONCLUSION

The results from this study provide insight into the potential of a multidrug combination involving ibuprofen with conventional antimicrobials and EOCs against common skin pathogens.

Skin and soft tissue infections in solid organ transplants

PURPOSE OF REVIEW

Skin and soft tissue infections (SSTI) in solid organ transplant (SOT) recipients may be a great challenge for clinicians caring for SOT due to the involvement of both common and opportunistic pathogens associated with a blunted immune response. The purpose of this review is to outline current literature and describe open issues on the management of SSTI in this special population.

RECENT FINDINGS

Clinical presentation in SOT recipients can manifest as isolated skin lesions after primary inoculation or be the sign of a disseminated infection. Tissue samples for microscopy and histopathology are crucial to making an accurate diagnosis given the nonspecific and heterogeneous appearance of skin lesions. Multidisciplinary teams are required for a comprehensive diagnosis and management.

SUMMARY

SSTI are frequent contributors to morbidity and mortality in SOT. Specific research focused on the clinical presentation, risk factors and management in this special population is needed.

In vitro activity of ceftaroline against bacterial isolates causing skin and soft tissue and respiratory tract infections collected in Latin American countries, ATLAS program 2016-2020

OBJECTIVES

Ceftaroline, a broad-spectrum cephalosporin, has activity against Gram-positive and several Gram-negative bacteria (GNB). This study aimed to evaluate the antimicrobial activity of ceftaroline and comparators against isolates causing skin and soft tissue infections (SSTIs) and respiratory tract infections (RTIs) collected in Latin America (LATAM) in 2016-2020 as part of the Antimicrobial Testing Leadership and Surveillance program (ATLAS).

METHODS

Minimum inhibitory concentrations were determined using both Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria.

RESULTS

Ceftaroline demonstrated potent activity against methicillin-susceptible Staphylococcus aureus (CLSI/EUCAST: MIC90 0.25 mg/L; susceptibility 100%), whereas activity against methicillin-resistant S. aureus varied for SSTIs (MIC90 1 mg/L; susceptibility 92.5%) and RTIs isolates (MIC90 2 mg/L; susceptibility 72.9%) isolates. For Streptococcus pneumoniae, particularly penicillin-resistant isolates commonly causing respiratory infections, high ceftaroline activity (MIC90 0.25 mg/L; susceptibility 100%/98.4%) was noted. All isolates of β-hemolytic streptococci were susceptible to ceftaroline (S. agalactiae: MIC90 0.03 mg/L [SSTIs]; MIC90 0.015 mg/L (RTIs); susceptibility 100%; S. pyogenes: MIC90 0.008 mg/L; susceptibility 100%). Ceftaroline was highly active against Haemophilus influenzae, including β-lactamase positive isolates (MIC90 0.06 mg/L; susceptibility 100%/85.7%). Ceftaroline demonstrated high activity against non-ESBL-producing GNB (E. coli: MIC90 0.5 mg/L, susceptibility 91.9%; K. pneumoniae: MIC90 0.25 mg/L, susceptibility 95.1%; K. oxytoca, MIC90 0.5 mg/L; susceptibility 95.7%).

CONCLUSION

Ceftaroline was active against the recent collection of bacterial pathogens commonly causing SSTIs and RTIs in LATAM. Local and regional surveillance of antimicrobial resistance patterns are crucial to understand evolving resistance and guide treatment management.

How to treat severe Acinetobacter baumannii infections

PURPOSE OF REVIEW

To update the management of severe Acinetobacter baumannii infections (ABI), particularly those caused by multi-resistant isolates.

RECENT FINDINGS

The in vitro activity of the various antimicrobial agents potentially helpful in treating ABI is highly variable and has progressively decreased for many of them, limiting current therapeutic options. The combination of more than one drug is still advisable in most circumstances. Ideally, two active first-line drugs should be used. Alternatively, a first-line and a second-line drug and, if this is not possible, two or more second-line drugs in combination. The emergence of new agents such as Cefiderocol, the combination of Sulbactam and Durlobactam, and the new Tetracyclines offer therapeutic options that need to be supported by clinical evidence.

SUMMARY

The apparent limitations in treating infections caused by this bacterium, the rapid development of resistance, and the serious underlying situation in most cases invite the search for alternatives to antibiotic treatment, the most promising of which seems to be bacteriophage therapy.

In Vitro Activity of Ceftaroline and Comparators against Bacterial Isolates Collected Globally from Patients with Skin and Soft Tissue Infections: ATLAS Program 2019-2020

The objective of this study was to assess the in vitro activity of ceftaroline and a panel of comparator agents against isolates causing skin and soft tissue infections (SSTIs) collected in Africa/Middle East, Asia-Pacific, Europe, and Latin America from 2019-2020. Minimum inhibitory concentrations (MIC) were determined using European Committee on Antimicrobial Susceptibility Testing criteria. All the methicillin-susceptible Staphylococcus aureus (MSSA) isolates were susceptible to ceftaroline. Across all regions, ceftaroline demonstrated potent activity against methicillin-resistant S. aureus (MRSA, susceptibility 89.5-93.7%) isolates. Susceptibility to vancomycin, daptomycin, linezolid, teicoplanin, trimethoprim sulfamethoxazole, and tigecycline was ≥94.1% in MSSA and MRSA isolates. Against β-hemolytic streptococci isolates, ceftaroline demonstrated very potent activity (MIC90 0.008-0.03 mg/L) across all regions. All β-hemolytic streptococci isolates were susceptible to linezolid, penicillin, and vancomycin (MIC90 0.06-2 mg/L). Among the extended-spectrum β-lactamases (ESBL)-negative Enterobacterales tested (E. coli, K. pneumoniae, and K. oxytoca), susceptibility to ceftaroline was high (88.2-98.6%) in all regions. All ESBL-negative Enterobacterales were susceptible to aztreonam. Potent activity was observed for amikacin, cefepime, and meropenem (94.1-100%) against these isolates. Overall, ceftaroline showed potent in vitro activity against isolates of pathogens causing SSTIs. Continuous surveillance of global and regional susceptibility patterns is needed to guide appropriate treatment options against these pathogens.

Antibiotic treatment of acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

Acute bacterial skin and skin structure infections (ABSSSI) are a leading cause of morbidity, with a considerable variety of clinical presentation and a wide range of etiological pathogens. Of importance, the spread of multidrug-resistant (MDR) strains (i.e. methicillin-resistant Staphylococcus aureus or Gram-negative bacteria) is increasingly reported in some regions. in this review, we summarize the current clinical approach to patients with ABSSSI.

RECENT FINDINGS

Accurate diagnosis and identification of risk factors for MDR pathogens are key determinants for administering appropriate therapy in patients with ABSSSI. In daily clinical practice, this can be critical as there are many features defining the 'high risk patient' including both disease and host-associated risk factors.

SUMMARY

Antibiotic therapy should be based according to the different clinical spectrum of disease belonging to the ABSSSI, on the pathogens most likely to be involved and local resistance. Careful evaluation of antibiotic therapy after 48-72 h of initial therapy could help clinicians to early identify patients with treatment failure and to consider an alternative approach. Close monitoring of patients with multiple comorbidities, drug-drug interaction or adverse host factors are also necessary.