In vitro elution characteristics of antibiotic-loaded polymethylmethacrylate cement and a calcium sulfate bone substitute using staphylococci isolated from orthopedic implant-associated infections.

Polymethylmethacrylate (PMMA) remains the gold standard antibiotic carrier in the management of osteomyelitis. However, biodegradable ceramic carriers may exhibit more efficient antibiotic elution properties. Through zone of inhibition (ZOI) testing and biofilm killing assays, we assessed the in vitro elution efficacy of vancomycin released from calcium sulfate (PG-CSH) and PMMA beads as carriers on clinical strains of Staphylococcus aureus and Staphylococcus epidermidis, which were isolated from sonication fluid of orthopedic implant-associated infections. Overall, vancomycin-loaded PMMA and PG-CSH beads showed potency (ZOI above 4 cm2 ) for up to 14 days against ATCC and clinical strains. Vancomycin-loaded PG-CSH beads displayed higher rates, exhibited a more stable antibiotic elution, had greater impacts on bacterial colony-forming unit counts and produced higher ZOIs; additionally, statistically significant differences (Student's t test) were observed in different time sets during the experiment. In the biofilm killing assay, PG-CSH loaded with vancomycin resulted in more bacterial deaths. In conclusion, in the present study, both PG-CSH and PMMA beads acted as good carriers, but greater antimicrobial elution and biofilm bacterial killing were observed with PG-CSH than PMMA. Future in vitro research should focus on testing other difficult-to-treat clinical strains, including multidrug resistant coagulase-negative staphylococci and Gram-negative bacilli.

In Vitro and In Vivo Synergism of Fosfomycin in Combination with Meropenem or Polymyxin B against KPC-2-Producing Klebsiella pneumoniae Clinical Isolates.

Fosfomycin disodium is a potential therapeutic option to manage difficult-to-treat infections, especially when combined with other antimicrobials. In this study, we evaluated the activity of fosfomycin in combination with meropenem or polymyxin B against contemporaneous KPC-2-producing K. pneumoniae clinical isolates (KPC-KPN). Synergistic activity was assessed by checkerboard (CKA) and time-kill (TKA) assays. TKA was performed using serum peak and trough concentrations. The activity of these combinations was also assessed in the Galleria mellonella model. Biofilm disruption was assessed by the microtiter plate technique. CKA resulted in an 8- to 2048-fold decrease in meropenem MIC, restoring meropenem activity for 82.4% of the isolates when combined with fosfomycin. For the fosfomycin + polymyxin B combination, a 2- to 128-fold reduction in polymyxin B MIC was achieved, restoring polymyxin B activity for 47% of the isolates. TKA resulted in the synergism of fosfomycin + meropenem (3.0-6.7 log10 CFU/mL decrease) and fosfomycin + polymyxin B (6.0-6.2 log10 CFU/mL decrease) at peak concentrations. All larvae treated with fosfomycin + meropenem survived. Larvae survival rate was higher with fosfomycin monotherapy (95%) than that observed for fosfomycin + polymyxin B (75%) (p-value < 0.0001). Finally, a higher biofilm disruption was observed under exposure to fosfomycin + polymyxin B (2.4-3.4-fold reduction). In summary, we observed a synergistic effect of fosfomycin + meropenem and fosfomycin + polymyxin B combinations, in vitro and in vivo, against KPC-KPN, as well as biofilm disruption.

Detection of Cutibacterium acnes in Tissue Samples from Clean Primary Shoulder Surgeries - Part II.

Objective Research and identification of Cutibacterium acnes ( C. acnes ) and other microorganisms in deep tissue samples collected in clean shoulder surgeries of patients who did not undergo any previous invasive joint procedure and who had no clinical history of infection. Methods We analyzed the results of cultures of intraoperative deep tissue samples from 84 patients submitted to primary clean shoulder surgery. Tubes containing culture medium were used for storage and transport of anaerobic agents, prolonged incubation time, and mass spectrometer for diagnosis of bacterial agents. Results Bacteria growth was evidenced in 34 patients (40.4%) of the 84 included in the study. Of these, 23 had growth of C. acnes in at least one sample of deep tissue collected, corresponding to 27.3% of the total patients. The second most common agent was Staphylococcus epidermidis , present in 7.2% of the total individuals included. We showed a higher relationship between sample positivity and males, a lower mean age, absence of diabetes mellitus, ASA I score, and antibiotic prophylaxis in anesthetic induction with cefuroxime. Conclusions A high percentage of isolates of different bacteria was found in shoulder tissue samples of patients undergoing clean and primary surgeries, who had no history of previous infection. Identification of C. acnes was high (27.6%), and Staphylococcus epidermidis was the second most frequent agent (7.2%).

Phenotypic and Genotypic Characterization of Cutibacterium acnes Isolated from Shoulder Surgery Reveals Insights into Genetic Diversity.

Specific virulence factors that likely influence C. acnes invasion into deep tissues remain to be elucidated. Herein, we describe the frequency of C. acnes identification in deep tissue specimens of patients undergoing clean shoulder surgery and assess its phenotypic and genetic traits associated with virulence and antibiotic resistance patterns, compared with isolates from the skin of healthy volunteers. Multiple deep tissue specimens from the bone fragments, tendons, and bursa of 84 otherwise healthy patients undergoing primary clean-open and arthroscopic shoulder surgeries were aseptically collected. The overall yield of tissue sample cultures was 21.5% (55/255), with 11.8% (30/255) identified as C. acnes in 27.3% (23/84) of patients. Antibiotic resistance rates were low, with most strains expressing susceptibility to first-line antibiotics, while a few were resistant to penicillin and rifampicin. Phylotypes IB (73.3%) and II (23.3%) were predominant in deep tissue samples. Genomic analysis demonstrated differences in the pangenome of the isolates from the same clade. Even though strains displayed a range of pathogenic markers, such as biofilm formation, patients did not evolve to infection during the 1-year follow-up. This suggests that the presence of polyclonal C. acnes in multiple deep tissue samples does not necessarily indicate infection.

Comparative Phenotypic and Genomic Features of Staphylococci from Sonication Fluid of Orthopedic Implant-Associated Infections with Poor Outcome.

Staphylococcus spp. remain the leading biofilm-forming agents causing orthopedic implant-associated infections (OIAI). This is a descriptive study of phenotypic and genomic features identified in clinical isolates of S. aureus and coagulase-negative Staphylococcus (CoNS) recovered from OIAIs patients that progressed to treatment failure. Ten isolates were identified by matrix-time-of-flight laser-assisted desorption mass spectrometry (MALDI-TOF-MS) and tested for antibiotic susceptibility and biofilm formation. Genotypic characteristics, including, MLST (Multi Locus Sequence Typing), SCCmec typing, virulence and resistance genes were assessed by whole-genome sequencing (WGS). All S. aureus harbored mecA, blaZ, and multiple resistance genes for aminoglycosides and quinolones. All MRSA were strong biofilm producers harboring the complete icaADBC and icaR operon. Seven CoNS isolates comprising five species (S. epidermidis, S. haemolyticus, S. sciuri, S. capitis and S. lugdunensis) were analyzed, with mecA gene detected in five isolates. S. haemolitycus (isolate 95), and S. lugdunensis were unable to form biofilm and did not harbor the complete icaADBCR operon. High variability of adhesion genes was detected, with atl, ebp, icaADBC operon, and IS256 being the most common. In conclusion, MRSA and CoNS isolates carrying genes for biofilm production, and resistance to ß-lactam and aminoglycosides are associated with treatment failure in OIAIs.

High lethality rate of carbapenem-resistant Acinetobacter baumannii in Intensive Care Units of a Brazilian hospital: An epidemiologic surveillance study.

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii (CRAB) is a growing threat to public health. METHODS: A 3-year retrospective study was conducted to evaluate the prevalence and lethality of multidrug-resistant (MDR) A. baumannii isolated from Brazilian patients. RESULTS: In this study, 219 Acinetobacter baumannii isolates were identified, of which 70.8% (155/219) were isolated from patients hospitalized in intensive care units. Of these, 57.4% (n = 89/155) were assessed, of which 92.1% (82/89) were carbapenem-resistant, and 49 were classified as infected. The lethality rate was 79.6% (39/49). CONCLUSIONS: We highlight the need of an effective epidemiological surveillance measure to contain the dissemination of CRAB in the hospital environment.

Multidrug-resistant Acinetobacter baumannii outbreaks: a global problem in healthcare settings.

INTRODUCTION: The increase in the prevalence of multidrug-resistant Acinetobacter baumannii infections in hospital settings has rapidly emerged worldwide as a serious health problem. METHODS: This review synthetizes the epidemiology of multidrug-resistant A. baumannii, highlighting resistance mechanisms. CONCLUSIONS: Understanding the genetic mechanisms of resistance as well as the associated risk factors is critical to develop and implement adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting.

A high mortality rate associated with multidrug-resistant Acinetobacter baumannii ST79 and ST25 carrying OXA-23 in a Brazilian intensive care unit.

The global spread of carbapenem-resistant Acinetobacter baumannii (A. baumannii) strains has restricted the therapeutic options available to treat infections due to this pathogen. Understanding the prevalence of such infections and the underlying genetic mechanisms of resistance may help in the implementation of adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting. This study describes the molecular characteristics and risk factors associated with OXA-23-producing A. baumannii infections. A case-control study was undertaken from September/2013 to April/2015. Acquisition of OXA-23-producing A. baumannii was found to be associated with the use of nasogastric tubes, haemodialysis, and the use of cephalosporins. These isolates were only susceptible to amikacin, gentamicin, tigecycline, and colistin, and contained the ISAba1 insertion sequence upstream ofblaOXA-23 and blaOXA-51 genes. Twenty-six OXA-23-producing A. baumannii strains belonged to the ST79 (CC79) clonal group,and patients infected or colonised by these isolates had a higher mortality rate (34.6%). In conclusion, this study showed a dissemination of OXA-23-producing A. baumannii strains that was associated with several healthcare-related risk factors and high mortality rates among intensive care unit patients.

Detection of Cutibacterium acnes in Tissue Samples from Clean Primary Shoulder Surgeries - Part II / Detecção de Cutibacterium acnes em amostras de tecidos de cirurgias limpas primárias do ombro - Parte II

Abstract Objective Research and identification of Cutibacterium acnes (C. acnes) and other microorganisms in deeptissue samples collected in clean shoulder surgeries of patients who did not undergo any previous invasive joint procedure and who had no clinical history of infection. Methods We analyzed the results of cultures of intraoperative deep tissue samples from 84 patients submitted to primary clean shoulder surgery. Tubes containing culture medium were used for storage and transport of anaerobic agents, prolonged incubation time, and mass spectrometer for diagnosis of bacterial agents. Results Bacteria growth was evidenced in 34 patients (40.4%) of the 84 included in the study. Of these, 23 had growth of C. acnes in at least one sample of deep tissue collected, corresponding to 27.3% of the total patients. The second most common agent was Staphylococcus epidermidis, present in 7.2% of the total individuals included. We showed a higher relationship between sample positivity and males, a lower mean age, absence of diabetes mellitus, ASA I score, and antibiotic prophylaxis in anesthetic induction with cefuroxime. Conclusions A high percentage of isolates of different bacteria was found in shoulder tissue samples of patients undergoing clean and primary surgeries, who had no history of previous infection. Identification of C. acnes was high (27.6%), and Staphylococcus epidermidis was the second most frequent agent (7.2%).

Resumo Objetivo Pesquisa e identificação de Cutibacterium acnes (C. acnes) e de outros microrganismos em amostras de tecidos profundos coletados em cirurgias limpas de ombro em pacientes que não foram submetidos a nenhum procedimento invasivo articular prévio e que não possuíam antecedentes clínicos de infecção. Métodos Foram analisados os resultados das culturas de amostras de tecidos profundos intraoperatórias de 84 pacientes submetidos à cirurgia limpa primária do ombro. Foram utilizados tubos contendo meio de cultivo para armazenamento e transporte de agentes anaeróbicos, tempo prolongado de incubação e espectrômetro de massa para diagnósticos de agentes bacterianos. Resultados Foi evidenciado o crescimento de bactérias em 34 pacientes (40,4%) dos 84 incluídos no estudo. Desses, 23 apresentavam crescimento de C. acnes em pelo menos uma amostra de tecido profundo coletada, correspondendo a 27,3% do total de pacientes. O segundo agente mais encontrado foi o Staphylococcus epidermidis, presente em 7,2% do total de indivíduos incluídos. Evidenciamos maior relação da positividade de amostras com o gênero masculino, uma média de idade inferior, a ausência de diabetes mellitus, o escore ASA I e a profilaxia antibiótica na indução anestésica com cefuroxima. Conclusões Verificou-se um elevado percentual de isolados de diferentes bactérias em amostras de tecidos de ombros de pacientes submetidos a cirurgias limpas e primárias e sem histórico de infecção anterior. A identificação de C. acnes foi elevada (27,6%) e o Staphylococcus epidermidis foi o segundo agente mais frequente (7,2%).

High lethality rate of carbapenem-resistant Acinetobacter baumannii in Intensive Care Units of a Brazilian hospital: An epidemiologic surveillance study

ABSTRACT Background: Carbapenem-resistant Acinetobacter baumannii (CRAB) is a growing threat to public health. Methods: A 3-year retrospective study was conducted to evaluate the prevalence and lethality of multidrug-resistant (MDR) A. baumannii isolated from Brazilian patients. Results: In this study, 219 Acinetobacter baumannii isolates were identified, of which 70.8% (155/219) were isolated from patients hospitalized in intensive care units. Of these, 57.4% (n = 89/155) were assessed, of which 92.1% (82/89) were carbapenem-resistant, and 49 were classified as infected. The lethality rate was 79.6% (39/49). Conclusions: We highlight the need of an effective epidemiological surveillance measure to contain the dissemination of CRAB in the hospital environment.

Multidrug-resistant Acinetobacter baumannii outbreaks: a global problem in healthcare settings

Abstract INTRODUCTION: The increase in the prevalence of multidrug-resistant Acinetobacter baumannii infections in hospital settings has rapidly emerged worldwide as a serious health problem. METHODS: This review synthetizes the epidemiology of multidrug-resistant A. baumannii, highlighting resistance mechanisms. CONCLUSIONS: Understanding the genetic mechanisms of resistance as well as the associated risk factors is critical to develop and implement adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting.