Prospective evaluation of an easy and reliable work flow for the screening of OXA-48-producing Klebsiella pneumoniae in endemic settings.

BACKGROUND: Carbapenemase-producing Enterobacterales (CPE) represent a serious threat to public health. Clinical microbiology laboratories (CMLs) need effective protocols for screening and confirmation of CPE. AIM: To prospectively evaluate an algorithm for the screening of carbapenemase-producing Klebsiella pneumoniae in an OXA-48 endemic hospital. METHODS: The algorithm was based on a disc diffusion assay using ertapenem and temocillin, which also served as a purity check for routine automated antimicrobial susceptibility testing. All isolates with minimal inhibitory concentrations >0.5 mg/L or zone inhibition diameters <25 mm for ertapenem (Criterion 1) and <12 mm for temocillin (Criterion 2) were tested sequentially by an OXA-48 lateral flow immunochromatographic assay and a multiplex polymerase chain reaction targeting VIM, KPC and OXA-48. If neither test was positive, the modified Hodge test or CARBA NP test was used. FINDINGS: Over 2 years, 2487 K. pneumoniae were assessed by the algorithm proposed, and 378 (15.20%) met both criteria. Of these, 98.68% (373/378) were either confirmed as OXA-48 producers or originated from patients with a previous CPE isolate that maintained the same resistance phenotype over time. The remaining three K. pneumoniae were VIM producers. Only two of the 378 isolates (0.53%) did not produce carbapenemase, despite meeting Criteria 1 and 2. CONCLUSION: The algorithm described combined the most sensitive carbapenem for CPE detection with a cut-off for temocillin that was highly specific for detection of OXA-48. It is reliable and easy to apply in routine CML work flow, allowing rapid detection of CPE isolates and hence prompt implementation of infection control measures and targeted antimicrobial regimens.

Prospective multicentre study of rectal carriage of multidrug-resistant Enterobacteriaceae among health-care workers in Spain.

OBJECTIVES: To investigate the rectal carriage of multidrug-resistant Enterobacteriaceae (colistin-resistant, extended-spectrum ß-lactamase (ESBL) -producers and/or carbapenemase-producers) among health-care workers (HCWs) from six Spanish hospitals. METHODS: Rectal swabs from 258 HCWs, employed in intensive care units, haematology wards and clinical microbiology laboratories from six hospitals in northern Spain were studied. They were cultured in selective media for Gram-negative resistant bacteria. Detection of antimicrobial resistance genes and multilocus sequence typing were performed by PCR and further sequencing. A questionnaire including data related to risk factors of colonization/infection by resistant bacteria (age, gender, chronic diseases, immunosuppressive therapies, invasive procedures or antimicrobial treatments) was given to each participant. RESULTS: No carbapenemase-producing Enterobacteriaceae were recovered. However, 8/258 HCWs (3.1%) were positive for ESBL-producing isolates. This rate was not higher than the colonization rate previously reported in Spain for healthy people in the community. Five isolates showed high-level resistance to colistin (MICs ranging from 8 to 128 mg/L) but all of them were negative for the mcr genes tested. No statistically significant risk factors for gut colonization by ESBL-producing or colistin-resistant Enterobacteriaceae were identified among the HCWs participating in the study. CONCLUSIONS: Our data suggest that working in hospitals does not represent a risk for rectal carriage of multidrug-resistant Enterobacteriaceae.

Long-term endemic situation caused by a linezolid- and meticillin-resistant clone of Staphylococcus epidermidis in a tertiary hospital.

BACKGROUND: Linezolid (LZD)-resistant Staphylococcus epidermidis (LRSE) are increasing, and are mainly associated with outbreaks in hospital wards with high LZD consumption. AIM: To investigate the frequency of LRSE in a tertiary hospital in the context of LZD use. METHODS: The frequency of LRSE and the data on LZD usage [expressed as defined daily dose (DDD) per 100 patient-days], from 2011 to 2017, were analysed retrospectively. Selected LRSE were typed by pulsed-field gel electrophoresis (PFGE) and screened for transferable LZD resistance genes. Representative isolates were typed by multi-locus sequence typing, and ribosomal mechanisms of LZD resistance were investigated. FINDINGS: In total, 435 LRSE were detected, with frequencies ranging from 13.56% to 32.93% in the intensive care unit (ICU) where LZD consumption was high (6.34-8.10 DDDs), and from 2.48 to 6.80% in the remaining wards where LZD use was considerably lower (0.63-2.49 DDDs). The first 44 LRSE isolates recovered (June 2013-June 2014) were closely related according to PFGE patterns, and all except one were resistant to meticillin due to mecA production. Selected isolates belonged to ST2, carried SCCmec III, and had the G2576T mutation in the V domain of each of the six copies of the 23S rRNA gene. Five of the 44 isolates (11.36%) were positive for the cfr gene. CONCLUSION: An ST2 LZD- and meticillin-resistant clone was found in the ICU and also in wards with low consumption of LZD. This highlights the need to implement and maintain infection control measures as well as antimicrobial stewardship programmes in all hospital units in order to preserve the efficacy of LZD.

Staphylococcus aureus meningitis in adults: A comparative cohort study of infections caused by meticillin-resistant and meticillin-susceptible strains.

BACKGROUND: Staphylococcus aureus meningitis is an uncommon nosocomial infection usually associated with neurosurgical procedures, but spontaneous infections may occasionally appear. AIMS: To compare the features of meningitis caused by meticillin-resistant (MRSA) and meticillin-susceptible (MSSA) S. aureus and examine the prognostic factors for mortality, including MRSA infection and combined antimicrobial therapy. METHODS: Retrospective cohort study of 350 adults with S. aureus meningitis admitted to 11 hospitals in Spain (1981-2015). Logistic regression and propensity score matching were used to analyse prognostic factors. RESULTS: There were 118 patients (34%) with MRSA and 232 (66%) with MSSA. Postoperative infection (91% vs 73%) and nosocomial acquisition (93% vs 74%) were significantly more frequent in MRSA than in MSSA meningitis (P < 0.001). Combined therapy was given to 118 (34%) patients. Overall 30-day mortality rate was 23%. On multivariate analysis, mortality was associated with severe sepsis or shock (odds ratio (OR) 9.9, 95% confidence interval (CI) 4.5-22.0, P < 0.001), spontaneous meningitis (OR 4.2, 95% CI 1.9-9.1, P < 0.001), McCabe-Jackson score rapidly or ultimately fatal (OR 2.8, 95% CI 1.4-5.4, P = 0.002), MRSA infection (OR 2.6, 95% CI 1.3-5.3, P = 0.006), and coma (OR 2.6, 95% CI 1.1-6.1, P < 0.029). In postoperative cases, mortality was related to retention of cerebrospinal devices (OR 7.9, 95% CI 3.1-20.3, P < 0.001). CONCLUSIONS: Clinical and epidemiological differences between MRSA and MSSA meningitis may be explained by the different pathogenesis of postoperative and spontaneous infection. In addition to the severity of meningitis and underlying diseases, MRSA infection was associated with increased mortality. Combined antimicrobial therapy was not associated with increased survival.

Nosocomial ventriculitis caused by a meticillin- and linezolid-resistant clone of Staphylococcus epidermidis in neurosurgical patients.

BACKGROUND: Postneurosurgical ventriculitis is mainly caused by coagulase-negative staphylococci. The rate of linezolid-resistant Staphylococcus epidermidis (LRSE) is increasing worldwide. AIMS: To report clinical, epidemiological and microbiological data from a series of ventriculitis cases caused by LRSE in a Spanish hospital between 2013 and 2016. METHODS: Cases of LRSE ventriculitis were reviewed retrospectively in a Spanish hospital over a four-year period. Clinical/epidemiological data of the infected patients were reviewed, the isolates involved were typed by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing, and the molecular bases of linezolid resistance were determined. FINDINGS: Five cases of LRSE ventriculitis were detected. The patients suffered from cerebral haemorrhage or head trauma that required the placement of an external ventricular drain; spent a relatively long time in the intensive care unit (ICU) (10-26 days); and three out of the five patients had previously been treated with linezolid. All LRSE had the same PFGE pattern, belonged to ST2, and shared an identical mechanism of linezolid resistance. Specifically, all had the G2576T mutation in the V domain of each of the six copies of the 23S rRNA gene, together with the Q136L and M156T mutations and the 71GGR72 insertion in the L3 and L4 ribosomal proteins, respectively. CONCLUSION: The high ratio of linezolid consumption in the ICU (7.72-8.10 defined daily dose/100 patient-days) could have selected this resistant clone, which has probably become endemic in the ICU where it could have colonized admitted patients. Infection control and antimicrobial stewardship interventions are essential to prevent the dissemination of this difficult-to-treat pathogen, and to preserve the therapeutic efficacy of linezolid.

[Epidemiological surveillance for multidrug-resistant microorganisms in a general ICU]. / Vigilancia epidemiológica para microorganismos multirresistentes en una UCI polivalente.

OBJECTIVE: Multidrug resistant (MDR) microorganisms represent a threat for patients admitted in Intensive Care Units (ICUs). The objective of the present study is to analyse the results of epidemiological surveillance cultures for these microorganisms in one of these units. METHODS: General ICU. Retrospective analysis, descriptive statistics. Analysis of epidemiological surveillance cultures for MDR microorganisms in 2015. Studied microorganisms: Methicillin-resistant Staphylococcus aureus (MRSA), ESBL-and/or carbapenemase-producing Klebsiella pneumoniae (CESBL-KP) and MDR Acinetobacter baumannii (MDRAB). RESULTS: One thousand, two hundred and fifty nine patients admitted. A total of 2,234 specimens from 384 patients were analysed (690, 634, 62 and 286 were rectal, throat, nasal and skin swabs respectively). Global APACHE II was 18.3 ± 8 versus 21.7 ± 7.8 in patients colonized/infected on admission. Global mortality was 19.7% versus 22.3% in patients colonized/infected on admission. The higher sensitivities achieved with the different samples for the different microorganism detection were as follows. MRSA: 79% and 90% for nasal and nasal + throat swabs, respectively. MDRAB: 80% and 95% for throat and throat + rectal swabs, respectively. CESBL-KP: 95% and 98% for rectal and rectal + throat swabs, respectively. 94 out of the 384 patients (24.4%) were colonized/infected with MDR at admission. 134 patients (10.6% of the total patients admitted) were colonized/infected with a total of 169 MMR during the hospital stay. MRSA has the earliest colonization/infection (9.2 ± 6.4days) and ESBL-producing Enterobacteriaceae, the latest (18.7± 16.4 days). CONCLUSIONS: 24.4% of patients were colonized/infected by MDR at admission. Nasal, throat and rectal swabs were the most effective specimens for recovering MRSA, MDRAB and CESBL-KP, respectively. The combination of two specimens improves MDR detection except for CESBL-KP. Skin swabs are worthless. The most prevalent MDR at admission were ESBL-producing Enterobacteriaceae while the most frequent hospital acquired MDR was MDRAB..

In vitro effects of dental cements on hard and soft tissues associated with dental implants.

STATEMENT OF PROBLEM: Dental cements for cement-retained restorations are often chosen based on clinician preference for the product's material properties, mixing process, delivery mechanism, or viscosity. The composition of dental cement may play a significant role in the proliferation or inhibition of different bacterial strains associated with peri-implant disease, and the effect of dental cements on host cellular proliferation may provide further insight into appropriate cement material selection. PURPOSE: The purpose of this in vitro study was to investigate the cellular host response of bone cells (osteoblasts) and soft tissue cells (gingival fibroblasts) to dental cements. MATERIAL AND METHODS: Zinc oxide (eugenol and noneugenol), zinc phosphate, and acrylic resin cements were molded into pellets and directly applied to confluent preosteoblast (cell line MC3T3 E1) or gingival fibroblast cell cultures (cell line HGF) to determine cellular viability after exposure. Controls were defined as confluent cell cultures with no cement exposure. Direct contact cell culture testing was conducted following International Organization for Standardization 10993 methods, and all experiments were performed in triplicate. To compare either the MC3T3 E1 cell line, or the HGF cell line alone, a 1-way ANOVA test with multiple comparisons was used (α=.05). To compare the MC3T3 E1 cell line results and the HGF cell line results, a 2-way ANOVA test with multiple comparisons was used (α=.05). RESULTS: The results of this study illustrated that while both bone and soft tissue cell lines were vulnerable to the dental cement test materials, the soft tissue cell line (human gingival fibroblasts) was more susceptible to reduced cellular viability after exposure. The HGF cell line was much more sensitive to cement exposure. Here, the acrylic resin, zinc oxide (eugenol), and zinc phosphate cements significantly reduced cellular viability after exposure with respect to HGF cells only. CONCLUSIONS: Within the limitation of this in vitro cellular study, the results indicated that cell response to various implant cements varied significantly, with osteoblast proliferation much less affected than gingival fibroblast cells. Furthermore, the zinc oxide noneugenol dental cement appeared to affect the cell lines significantly less than the other test cements.

A finite element analysis of novel vented dental abutment geometries for cement-retained crown restorations.

Recent literature indicates that the long-term success of dental implants is, in part, attributed to how dental crowns are attached to their associated implants. The commonly utilized method for crown attachment - cementation, has been criticized because of recent links between residual cement and peri-implant disease. Residual cement extrusion from crown-abutment margins post-crown seating is a growing concern. This study aimed at (1) identifying key abutment features, which would improve dental cement flow characteristics, and (2) understanding how these features would impact the mechanical stability of the abutment under functional loads. Computational fluid dynamic modeling was used to evaluate cement flow in novel abutment geometries. These models were then evaluated using 3D-printed surrogate models. Finite element analysis also provided an understanding of how the mechanical stability of these abutments was altered after key features were incorporated into the geometry. The findings demonstrated that the key features involved in improved venting of the abutment during crown seating were (1) addition of vents, (2) diameter of the vents, (3) location of the vents, (4) addition of a plastic screw insert, and (5) thickness of the abutment wall. This study culminated in a novel design for a vented abutment consisting of 8 vents located radially around the abutment neck-margin plus a plastic insert to guide the cement during seating and provide retrievability to the abutment system.Venting of the dental abutment has been shown to decrease the risk of undetected residual dental cement post-cement-retained crown seating. This article will utilize a finite element analysis approach toward optimizing dental abutment designs for improved dental cement venting. Features investigated include (1) addition of vents, (2) diameter of vents, (3) location of vents, (4) addition of plastic screw insert, and (5) thickness of abutment wall.

Characterization of Cement Particles Found in Peri-implantitis-Affected Human Biopsy Specimens.

PURPOSE: Peri-implantitis is a disease characterized by soft tissue inflammation and continued loss of supporting bone, which can result in implant failure. Peri-implantitis is a multifactorial disease, and one of its triggering factors may be the presence of excess cement in the soft tissues surrounding an implant. This descriptive study evaluated the composition of foreign particles from 36 human biopsy specimens with 19 specimens selected for analysis. The biopsy specimens were obtained from soft tissues affected by peri-implantitis around cement-retained implant crowns and compared with the elemental composition of commercial luting cement. MATERIALS AND METHODS: Nineteen biopsy specimens were chosen for the comparison, and five test cements (TempBond, Telio, Premier Implant Cement, Intermediate Restorative Material, and Relyx) were analyzed using scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. This enabled the identification of the chemical composition of foreign particles embedded in the tissue specimens and the composition of the five cements. Statistical analysis was conducted using classification trees to pair the particles present in each specimen with the known cements. RESULTS: The particles in each biopsy specimen could be associated with one of the commercial cements with a level of probability ranging between .79 and 1. TempBond particles were found in one biopsy specimen, Telio particles in seven, Premier Implant Cement particles in four, Relyx particles in four, and Intermediate Restorative Material particles in three. CONCLUSION: Particles found in human soft tissue biopsy specimens around implants affected by peri-implant disease were associated with five commercially available dental cements.

Characterization of a new composite PMMA-HA/Brushite bone cement for spinal augmentation.

Calcium phosphate fillers have been shown to increase cement osteoconductivity, but have caused drawbacks in cement properties. Hydroxyapatite and Brushite were introduced in an acrylic two-solution cement at varying concentrations. Novel composite bone cements were developed and characterized using rheology, injectability, and mechanical tests. It was hypothesized that the ample swelling time allowed by the premixed two-solution cement would enable thorough dispersion of the additives in the solutions, resulting in no detrimental effects after polymerization. The addition of Hydroxyapatite and Brushite both caused an increase in cement viscosity; however, these cements exhibited high shear-thinning, which facilitated injection. In gel point studies, the composite cements showed no detectable change in gel point time compared to an all-acrylic control cement. Hydroxyapatite and Brushite composite cements were observed to have high mechanical strengths even at high loads of calcium phosphate fillers. These cements showed an average compressive strength of 85 MPa and flexural strength of 65 MPa. A calcium phosphate-containing cement exhibiting a combination of high viscosity, pseudoplasticity and high mechanical strength can provide the essential bioactivity factor for osseointegration without sacrificing load-bearing capability.

Preparation of TiO2 nanoparticles coated with ionic liquids: a supramolecular approach.

Coated TiO2 nanoparticles by dicationic imidazolium-based ionic liquids (ILs) were prepared and studied by differential scanning calorimetry (DSC), dynamic light scattering (DLS), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). Three ILs with different hydrophobicity degrees and structural characteristics were used (IL-1, IL-2, and IL-3). The interaction between IL molecules and the TiO2 surface was analyzed in both solid state and in solution. The physical and chemical properties of coated nanoparticles (TiO2 + IL-1, TiO2 + IL-2, and TiO2 + IL-3) were compared to pure materials (TiO2, IL-1, IL-2, and IL-3) in order to evaluate the interaction between both components. Thermal behavior, diffraction pattern, and morphologic characteristics were evaluated in the solid state. It was observed that all mixtures (TiO2 + IL) showed different behavior from that detected for pure substances, which is an evidence of film formation. DLS experiments were conducted to determine film thickness on the TiO2 surface comparing the size (hydrodynamic radius, Rh) of pure TiO2 with coated nanoparticles (TiO2 + IL). Results showed the thickness of the film increased with hydrophobicity of the IL compound. TEM images support this observation. Finally, X-ray diffraction patterns showed that, in coated samples, no structural changes in TiO2 diffraction peaks were observed, which is related to the maintenance of the crystalline structure. On the contrary, ILs showed different diffraction patterns, which confirms the hypothesis of interactions happening between IL and the TiO2 nanoparticles surface.

Preparation and Characterization of Injectable Brushite Filled-Poly (Methyl Methacrylate) Bone Cement.

Powder-liquid poly (methyl methacrylate) (PMMA) bone cements are widely utilized for augmentation of bone fractures and fixation of orthopedic implants. These cements typically have an abundance of beneficial qualities, however their lack of bioactivity allows for continued development. To enhance osseointegration and bioactivity, calcium phosphate cements prepared with hydroxyapatite, brushite or tricalcium phosphates have been introduced with rather unsuccessful results due to increased cement viscosity, poor handling and reduced mechanical performance. This has limited the use of such cements in applications requiring delivery through small cannulas and in load bearing. The goal of this study is to design an alternative cement system that can better accommodate calcium-phosphate additives while preserving cement rheological properties and performance. In the present work, a number of brushite-filled two-solution bone cements were prepared and characterized by studying their complex viscosity-versus-test frequency, extrusion stress, clumping tendency during injection through a syringe, extent of fill of a machined void in cortical bone analog specimens, and compressive strength. The addition of brushite into the two-solution cement formulations investigated did not affect the pseudoplastic behavior and handling properties of the materials as demonstrated by rheological experiments. Extrusion stress was observed to vary with brushite concentration with values lower or in the range of control PMMA-based cements. The materials were observed to completely fill pre-formed voids in bone analog specimens. Cement compressive strength was observed to decrease with increasing concentration of fillers; however, the materials exhibited high enough strength for consideration in load bearing applications. The results indicated that partially substituting the PMMA phase of the two-solution cement with brushite at a 40% by mass concentration provided the best combination of the properties investigated. This alternative material may find applications in systems requiring highly injectable and viscous cements such as in the treatment of spinal fractures and bone defects.