Evaluation of MBEC™‐HTP biofilm model for studies of implant associated infections

The bacteria in implant‐related infections can evade host defenses by forming biofilms. The more we understand biofilm behavior, the better we can fight against then clinically. In vitro models for biofilms allow tests simulating in vivo conditions. In this study we evaluated the Minimum Biofilm Eradication Concentration‐High Throughput Plates (MBEC?‐HTP) as biofilm in vitro model for studies of implant associated infections. Staphylococcus aureus and Staphylococcus epidermidis biofilms were grown on MBEC?‐HTP. To ensure the biofilm formation, antibiotic susceptibility tests and scanning electron microscopy (SEM) was carried out. Susceptibility tests were carried out using gentamicin, vancomycin, rifampicin, fosfomycin, clindamycin, and linezolid. Colony forming units counting were carried out. Minimal inhibitory concentration (MIC) and biofilm inhibitory concentration (BIC) were estimated. The CFU counting showed potency of rifampicin and daptomycin against S. epidermidis biofilms and rifampicin against S. aureus biofilms. SEM images showed proteic material in contact with cells. The differences between BIC and MIC demonstrated the biofilm formation as well as the SEM images. Rifampicin and daptomycin are good choices against biofilm related infections. Moreover, after suggested modifications, the model used in this study is eligible to further studies of implant associated infections. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1176–1180, 2012     

Large variations in clinical antibiotic activity against Staphylococcus aureus biofilms of periprosthetic joint infection isolates

Staphylococcus aureus biofilms have a high tolerance to antibiotics, making the treatment of periprosthetic joint infection (PJI) challenging. From a clinical perspective, bacteria from surgical specimens are cultured in a planktonic state to determine antibiotic sensitivity. However, S. aureus exists primarily as established biofilms in PJI. To address this dichotomy, we developed a prospective registry of total knee and hip arthroplasty PJI S. aureus isolates to quantify the activity of clinically important antibiotics against isolates grown as biofilms. S. aureus planktonic minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were assessed using clinical laboratory standard index assays for 10 antibiotics (cefazolin, clindamycin, vancomycin, rifampin, linezolid, nafcillin, gentamicin, trimethoprim/sulfamethoxazole, doxycycline, and daptomycin). Mature biofilms of each strain were grown in vitro, after which biofilm MIC (MBIC) and biofilm MBC (MBBC) were determined. Overall, isolates grown as biofilms displayed larger variations in antibiotic MICs as compared to planktonic MIC values. Only rifampin, doxycycline, and daptomycin had measurable biofilm MIC values across all S. aureus isolates tested. Biofilm MBC observations complemented biofilm MIC observations; rifampin, doxycycline, and daptomycin were the only antibiotics with measurable biofilm MBC values. 90% of S. aureus biofilms could be killed by rifampin, 50% by doxycycline, and only 15% by daptomycin. Biofilm formation increased bacterial antibiotic tolerance nonspecifically across all antibiotics, in both MSSA and MRSA samples. Rifampin and doxycycline were the most effective antibiotics at killing established S. aureus biofilms. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1604–1609, 2019.     

Combined local and systemic antibiotic treatment is effective against experimental Staphylococcus aureus peri‐implant biofilm infection

We hypothesized that systemic ceftriaxone and high concentration local antibiotics might eradicate peri‐implant sepsis. Experiment 1: Eighty‐four implants inoculated with biofilm‐forming Staphylococcus aureus were treated in vitro with gentamicin, vancomycin, gentamicin + rifampin, or vancomycin + rifampin for 2, 4, or 8 days. Experiment 2: Forty‐five implants were wired in vivo to rat femurs and inoculated with 1 × 10⁶ CFU S. aureus. After 48 h, rats were treated once daily for 5 days with systemic ceftriaxone, local tobramycin or ceftriaxone, and tobramycin. Experiment 3: Forty implants with established S. aureus biofilms were wired in vivo to rat femurs. After 48 h, rats were treated with systemic ceftriaxone alone or in combination with local gentamicin, gentamicin and rifampin, or vancomycin. Experiment 1: 100% of implants treated in vitro with gentamicin were sterile after 48 h. The other treatments did not become sterile until 4 days. Experiment 2: No implant was culture negative. The combination of systemic ceftriaxone and local tobramycin was significantly better than others (p < 0.008). Experiment 3: Systemic ceftriaxone alone was ineffective. All implants treated with systemic ceftriaxone and local gentamicin were sterile (p < 0.001), the other groups were less effective. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1320–1326, 2015.     

Impact of selective antimicrobial agents on staphylococcal adherence to biomedical devices

BACKGROUND: Infection of intravascular or implanted biomedical devices often involves biofilm-forming staphylococci that are recalcitrant to antimicrobial therapy. The present study investigated the activity of 6 antimicrobial agents against biofilm-forming and non-biofilm-forming strains of staphylococci adherent to the surface of selected biomedical devices. METHODS: Five clinical staphylococcal strains were selected for study in (1) antibiotic-lock model (ALM) and (b) vascular graft model (Dacron and expanded polytetrafluoroethylene [ePFTE]) devices. Test strains were inoculated for 30 minutes to stabilize microbial adherence and then exposed to antibiotic; the impact on bacterial adherence was assessed at 1, 2, 4, 7, and 10 days. RESULTS: Regarding ALM, daptomycin and rifampin were effective at eradicating staphylococcal adherence by day 4 (P<.01); linezolid and gentamicin by day 7 (P<.01); vancomycin by day 7; and ceftriaxone failed to eradicate staphylococcal adherence in 4 of 5 strains by day 10. Regarding ePTFE, daptomycin and linezolid eradicated staphylococcal adherence by day 2 (P<.01); rifampin by day 4 (P<.01); vancomycin and gentamicin by day 7 (P<.01); and ceftriaxone failed to eliminate staphylococcal adherence in 3 of 5 strains by day 10. Regarding Dacron, daptomycin and rifampin eradicated adherent strains by day 4 (P<.01); linezolid by day 7 (P<.01), and vancomycin, gentamicin, and ceftriaxone decreased staphylococcal adherence by 90%, 95%, and 78%, respectively, by day 10. COMMENTS: Daptomycin, rifampin, and linezolid demonstrated greater efficacy and speed in eradicating microbial adherence of staphylococcal isolates from selected devices compared with vancomycin, gentamicin, or ceftriaxone (P<.01). Further studies are warranted, however, to validate the clinical efficacy of daptomycin and linezolid in the treatment of biomedical device-associated infections.     

Reduced ability to detect surface-related biofilm bacteria after antibiotic exposure under in vitro conditions

Background and purpose — Antibiotic treatment of patients before specimen collection reduces the ability to detect organisms by culture. We investigated the suppressive effect of antibiotics on the growth of non-adherent, planktonic, and surface-related biofilm bacteria in vitro by using sonication and microcalorimetry methods.

Patients and methods — Biofilms of Staphylococcus aureus, S. epidermidis, Escherichia coli, and Propionibacterium acnes were formed on porous glass beads and exposed for 24?h to antibiotic concentrations from 1 to 1,024 times the minimal inhibitory concentration (MIC) of vancomycin, daptomycin, rifampin, flucloxacillin, or ciprofloxacin. The beads were then sonicated to dislodge biofilm, followed by culture and measurement of growth-related heat flow by microcalorimetry of the resulting sonication fluid.

Results — Vancomycin did not inhibit the heat flow of staphylococci and P. acnes at concentrations ≤1,024?μg/mL, whereas flucloxacillin at >128?μg/mL inhibited S. aureus. Daptomycin inhibited heat flow of S. aureus, S. epidermidis, and P. acnes at lower concentrations (32–128 times MIC, p < 0.001). Rifampin showed inconsistent results in staphylococci due to random emergence of resistance, which was observed at concentrations ≤1,024 times MIC (i.e. 8?μg/mL). Ciprofloxacin inhibited heat flow of E. coli at ≥4 times MIC (i.e. ≥ 0.06?μg/mL).

Interpretation — Whereas time-dependent antibiotics (i.e. vancomycin and flucloxacillin) showed only weak growth suppression, concentration-dependent drugs (i.e. daptomycin and ciprofloxacin) had a strong suppressive effect on bacterial growth and reduced the ability to detect planktonic and biofilm bacteria. Exposure to rifampin rapidly caused emergence of resistance. Our findings indicate that preoperative administration of antibiotics may have heterogeneous effects on the ability to detect biofilm bacteria.     

万古霉素阳离子脂质体复合纳米羟基磷灰石/壳聚糖/魔芋葡苷聚糖支架对金黄色葡萄球菌生物膜体外抑制作用

目的：研究万古霉素阳离子脂质体（ CLVs）复合纳米羟基磷灰石/壳聚糖/魔芋葡苷聚糖支架对金黄色葡萄球菌生物膜的抑制作用。方法采用微量肉汤稀释法测定药物对金黄色葡萄球菌的最小抑菌浓度,采用再生实验方法研究支架释放的CLVs对金黄色葡萄球菌生物膜的敏感性。结果万古霉素和CLVs对金黄色葡萄球菌的最小抑菌浓度分别为1．0 mg/L和0．6 mg/L;相同浓度的万古霉素脂质体复合支架对细菌生物膜的作用在低浓度和短时间的接触较游离万古霉素支架更有效。结论 CLVs复合纳米羟基磷灰石/壳聚糖/魔芋葡苷聚糖支架可以作为新的载药系统,在临床治疗生物膜感染方面可起到重要作用。     

Targeting intracellular Staphylococcus aureus to lower recurrence of orthopaedic infection

Staphylococcus aureus is often found in orthopaedic infections and may be protected from commonly prescribed antibiotics by forming biofilms or growing intracellularly within osteoblasts. To investigate the effect of non‐antibiotic compounds in conjunction with antibiotics to clear intracellular and biofilm forming S. aureus causing osteomyelitis. SAOS‐2 osteoblast‐like cell lines were infected with S. aureus BB1279. Antibiotics (vancomycin, VAN; and dicloxacillin, DICLOX), bacterial efflux pump inhibitors (piperine, PIP; carbonyl cyanide m‐chlorophenyl hydrazone, CCCP), and bone morphogenetic protein (BMP‐2) were evaluated individually and in combination to kill intracellular bacteria. We present direct evidence that after gentamicin killed extracellular planktonic bacteria and antibiotics had been stopped, seeding from the infected osteoblasts grew as biofilms. VAN was ineffective in treating the intracellular bacteria even at 10× MIC; however in presence of PIP or CCCP the intracellular S. aureus was significantly reduced. Bacterial efflux pump inhibitors (PIP and CCCP) were effective in enhancing permeability of antibiotics within the osteoblasts and facilitated killing of intracellular S. aureus. Confocal laser scanning microscopy (CLSM) showed increased uptake of propidium iodide within osteoblasts in presence of PIP and CCCP. BMP‐2 had no effect on growth of S. aureus either alone or in combination with antibiotics. Combined application of antibiotics and natural agents could help in the treatment of osteoblast infected intracellular bacteria and biofilms associated with osteomyelitis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1086–1092, 2018.

     

Does Extracellular DNA Production Vary in Staphylococcal Biofilms Isolated From Infected Implants versus Controls?

Background

Prosthetic implant infections caused by Staphylococcus aureus and epidermidis are major challenges for early diagnosis and treatment owing to biofilm formation on the implant surface. Extracellular DNA (eDNA) is actively excreted from bacterial cells in biofilms, contributing to biofilm stability, and may offer promise in the detection or treatment of such infections.

Questions/purposes

(1) Does DNA structure change during biofilm formation? (2) Are there time-dependent differences in eDNA production during biofilm formation? (3) Is there differential eDNA production between clinical and control Staphylococcal isolates? (4) Is eDNA production correlated to biofilm thickness?

Methods

We investigated eDNA presence during biofilm formation in 60 clinical and 30 control isolates of S aureus and S epidermidis. The clinical isolates were isolated from patients with infections of orthopaedic prostheses and implants: 30 from infected hip prostheses and 30 from infected knee prostheses. The control isolates were taken from healthy volunteers who had not been exposed to antibiotics and a hospital environment during the previous 3 and 12 months, respectively. Control S epidermidis was isolated from the skin of the antecubital fossa, and control S aureus was isolated from the nares. For the biofilm experiments the following methods were used to detect eDNA: (1) fluorescent staining with 4′,6-diamidino-2-phenylindole (DAPI), (2) eDNA extraction using a commercial kit, and (3) confocal laser scanning microscopy for 24-hour biofilm observation using propidium iodide and concanavalin-A staining; TOTO^®-1 and SYTO^® 60 staining were used for observation and quantification of eDNA after 6 and 24 hours of biofilm formation. Additionally antibiotic resistance was described.

Results

eDNA production as observed by confocal laser scanning microscopy was greater in clinical isolates than controls (clinical isolates mean ± SD: 1.84% ± 1.31%; control mean ± SD: 1.17% ± 1.37%; p < 0.005) after 6 hours of biofilm formation. After 24 hours, the amount of eDNA was greater in biofilms of S epidermidis than in biofilms of S aureus (S aureus mean ± SD: 1.35% ± 2.0%; S epidermidis mean ± SD: 6.42% ± 10.6%; p < 0.05). Clinical isolates of S aureus and S epidermidis produced more eDNA than control isolates at 6 hours of biofilm formation. The extraction method also showed that clinical isolates produced substantially greater amounts of eDNA than controls.

Conclusions

S aureus and S epidermidis exhibit a differential production of DNA with time. Clinical isolates associated with implant infections produce greater amounts of eDNA than controls. Future research might focus on the diagnostic value of eDNA as a surrogate laboratory marker for biofilm formation in implant infections.

Clinical relevance

eDNA should be considered as a potential future diagnostic tool or even a possible target to modify biofilms for successful treatment of biofilm-associated infections.

     

Daptomycin and Rifampin Alone and in Combination Prevent Vascular Graft Biofilm Formation and Emergence of Antibiotic Resistance in a Subcutaneous Rat Pouch Model of Staphylococcal Infection

ObjectiveTo investigate the efficacy of daptomycin and rifampin either alone or in combination in preventing prosthesis biofilm in a rat model of staphylococcal vascular graft infection.DesignProspective, randomised, controlled animal study.MaterialsGraft infections were established in the back subcutaneous tissue of adult male Wistar rats by implantation of Dacron prostheses followed by topical inoculation with 2 × 10⁷ colony forming units of Staphylococcus aureus, strain Smith diffuse.MethodsThe study included a control group, a contaminated group that did not receive any antibiotic prophylaxis and three contaminated groups that received intra-peritoneal daptomycin, rifampin-soaked graft and daptomycin plus rifampin-soaked graft, respectively. Each group included 15 animals. The infection burden was evaluated by using sonication and quantitative agar culture. Moreover, an in vitro antibiotic susceptibility assay for S. aureus biofilms was performed to elucidate the same activity.ResultsWhen tested alone, daptomycin and rifampin showed good efficacies. Their combination showed efficacies significantly higher than that of each single compound. The in vitro studies showed that Minimum Inhibitory Concentration and Minimum Bactericidal Concentration values for daptomycin were lower in presence of rifampin. Daptomycin prevented the emergence of rifampin resistance.ConclusionDaptomycin is an important candidate for prevention of staphylococcal biofilm-related infection and rifampin could serve as an interesting anti-staphylococcal antibiotic enhancer.     

Determination of cephazolin, ceftazidime, and ceftriaxone distribution in nucleus pulposus

Background

The intervertebral disc is the largest avascular structure in the adult body and minimal blood flow through capillary beds only supplying the outer regions of the disc, which relies on the passive diffusion as a major factor for nutrition and uptake of molecules, including antibiotics. This study is to detect the serum and nucleus pulposus (NP) levels of cephazolin, ceftazidime, and ceftriaxone and to assess this antibiotic permeability into the intervertebral disc.

Methods

Forty-five consecutive patients undergoing lumbar interbody fusion surgery were divided into three groups to participate in the study. Approximately 30?min before the procedures, a bolus dose 2?g antibiotic of cephazolin, ceftazidime, and ceftriaxone was administered intravenously. The NP tissue and serum sample levels of antibiotic were assayed by high performance liquid chromatography.

Results

Three cases failed in the ceftriaxone group because the NP tissue contaminates the blood. Average time between antibiotic injection and tissue/blood collection was 41?min (range 27–57?min). The antibiotic concentration level of cephazolin, ceftazidime, and ceftriaxone was 144.26?±?29.15, 127.19?±?30.22, and 227.81?±?51.48?μg/ml in serum and 2.33?±?0.45, 3.74?±?1.91, and 2.23?±?1.86?μg/g in NP, respectively. The antibiotic penetration in to NP of cephazolin was 1.67?±?0.44, 2.99?±?1.99 of ceftazidime, and 1.08?±?1.44 of ceftriaxone.

Conclusions

The antibiotics of cephazolin, ceftazidime, and ceftriaxone had concentration in the NP tissue, which was higher than the stated MIC. Ceftazidime had highest penetration in to NP tissue, and ceftriaxone had the lowest penetration in to NP tissue.     

Biofilm dispersal of community‐associated methicillin‐resistant Staphylococcus aureus on orthopedic implant material

Orthopedic implant‐related bacterial infections are associated with high morbidity that may lead to limb amputation and exert significant financial burden on the healthcare system. Staphylococcus aureus is a dominant cause of these infections, and increased incidence of community‐associated methicillin‐resistant S. aureus (CA‐MRSA) is being reported. The ability of S. aureus to attach to the foreign body surface and develop a biofilm is an important determinant of resistance to antibiotic prophylaxis. To gain insight on CA‐MRSA biofilm properties, USA300 biofilm maturation and dispersal was examined, and these biofilms were found to exhibit pronounced, quorum‐sensing mediated dispersal from a glass surface. For comparison of biofilm maturation on different surface chemistries, USA300 biofilm growth was examined on glass, polycarbonate, and titanium, and minimal differences were apparent in thickness, total biomass, and substratum coverage. Importantly, USA300 biofilms grown on titanium possessed a functional dispersal mechanism, and the dispersed cells regained susceptibility to rifampicin and levofloxacin treatment. The titanium biofilms were also sensitive to proteinase K and DNaseI, suggesting the matrix is composed of proteinaceous material and extracellular DNA. These studies provide new insights on the properties of CA‐MRSA biofilms on implant materials, and indicate that quorum‐sensing dispersion could be an effective therapeutic strategy. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:55–61, 2010     

Pharmacodynamic performance of tigecycline versus common intravenous antibiotics for the empiric treatment of complicated skin and skin structure infections

BACKGROUND: In clinical trials tigecycline was similar to vancomycin/aztreonam for complicated skin and skin structure infections, but data comparing it with other widely used antibiotics are lacking. We predicted the pharmacodynamic cumulative fraction of response (CFR) of tigecycline against bacteria implicated in complicated skin and skin structure infections and compared it with the CFRs for piperacillin/tazobactam, ceftriaxone, levofloxacin, and imipenem/cilastatin. METHODS: A 5,000-patient Monte Carlo simulation using a two-compartment intravenous infusion model was used to simulate steady-state concentrations for common dosages of these antibiotics. Population pharmacokinetics data from infected patients were employed. The CFR was calculated against Staphylococcus aureus (42% methicillin-resistant S. aureus [MRSA]), streptococci, coagulase-negative staphylococci, Escherichia coli, Enterobacter, enterococci, Proteus mirabilis, Klebsiella, and Pseudomonas aeruginosa collected from worldwide surveillance (TEST and SENTRY) and weighted by prevalence of involvement in complicated skin and skin structure infections. RESULTS: Excluding MRSA, the weighted CFR was greatest for imipenem/cilastatin and piperacillin/tazobactam regimens (93.9%-95.9%). With 42% MRSA added to the model, only tigecycline monotherapy achieved a high CFR (88.2%). The addition of vancomycin raised the CFR to 91.0%, 89.5%, 88.3%, 82.9%, and 78% for imipenem/cilastatin 500 mg q6h, imipenem/cilastatin 500 mg q8h, piperacillin/tazobactam, levofloxacin, and ceftriaxone regimens, respectively. CONCLUSION: Tigecycline monotherapy had a likelihood of achieving its requisite pharmacodynamic exposure similar to that of combinations of piperacillin/tazobactam or imipenem/cilastatin plus vancomycin for the empiric treatment of complicated skin and skin structure infections.     

Current review—The rise of bacteriophage as a unique therapeutic platform in treating peri‐prosthetic joint infections

Peri‐prosthetic joint infection (PJI) is one of the most serious and dreaded complications after total joint replacement (TJR). Due to an aging population and the constant rise in demand for TJR, the incidence of PJI is also increasing. Successful treatment of PJI is challenging and is associated with high failure rates. One of the main causes for treatment failure is bacterial biofilm formation on implant surfaces and the adherence of biofilm bacteria on tissue and bone next to the implant. Biofilms are protective shields to bacterial cells and possess many unique properties that leads to antibiotic resistance. New therapeutic platforms are currently being explored to breakdown biofilm matrix in order to enhance the efficacy of antibiotics. Bacteriophages (phages) is one of these unique therapeutic platforms that can degrade biofilms as well as target the killing of bacterial cells. Preclinical studies of biofilm‐mediated infections have demonstrated the ability of phage to eradicate biofilms and clear infections by working synergistically with antibiotics. There is strong preclinical evidence that phage can reduce the concentration of antibiotics required to treat an infection. These findings support a promising role for phages as a future clinical adjunct to antibiotics. In addition, phage therapy can be personalized to target a specific bacterial strain. Clinical studies using phage therapy are limited in Western literature; but phase I studies have established good safety profile with no adverse outcomes reported. In order to translate phage therapy to treat PJI in clinics, further preclinical testing is still required to study optimal delivery methods as well as the interaction between phage and the immune system in vivo. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1051–1060, 2018.

     

Phenotypic characteristics of incident and chronic MRSA isolates in cystic fibrosis

BackgroundChronic methicillin resistant Staphylococcus aureus (MRSA) in CF is associated with worse outcomes compared to early or intermittent infection. This observation could be related to adaptive bacterial changes such as biofilm formation or anaerobic growth.MethodsMRSA isolates stored from incident and during chronic (>2 years) infection were included at two study sites. MRSA isolates were characterised by spa-typing, antimicrobial susceptibility testing, biofilm formation and haemolysis under aerobic and anaerobic culture conditions.ResultsPaired MRSA isolates from 49 patients were included. Mean age at incident infection was 9.7±1.2 years with mild to moderate lung disease (FEV₁ 74±4% predicted). Twenty-five subjects showed progression of disease/symptoms after onset of MRSA with significantly increased use of antibiotics. Most isolates belonged to t002 (38%) and t008 (36%) spa-types and 8 patients had a change in spa-type over time. Antimicrobial susceptibility testing showed few differences between incident and late isolates but significantly lower MIC under anaerobic vs. aerobic conditions for vancomycin, fusidic acid, rifampin but higher MIC for trimethoprim-sulfamethoxazole. Biofilm formation and haemolysis did not differ by stage of infection or disease course but both were lower under anaerobic conditions (biofilm p=0.018; haemolysis p=0.002) in multi-variate analyses that included study site, growth condition and stage of infection.ConclusionsPersistent MRSA infection is frequently associated with clinical decline. Anaerobic growth conditions, which occur in CF airways, affect the expression of virulence factors and antibiotic susceptibility of MRSA more than duration of infection.     

Comparison of the effects of human β-defensin 3, vancomycin, and clindamycin on Staphylococcus aureus biofilm formation

Despite improvements in surgical techniques and implant design in orthopedic surgery, implantation-associated infections are still a challenging problem for surgeons. In 2006, trace quantities of human β-defensin 3 (hBD-3) were found in human bone tissue and bone cells. Human β-defensin 3 is a 45-amino-acid peptide that is considered the most promising class of defensin antimicrobial peptides and may help in the prevention and treatment of implantation-associated infections. Studies of the effectiveness of hBD-3 against Staphylococcus aureus showed that hBD-3 was more potent at low concentrations than other antibiotics. The effect of hBD-3 on S aureus biofilms has not been reported. We studied the effect of hBD-3, vancomycin, and clindamycin on S aureus biofilms and on the survival of the bacteria in the biofilms.Staphylococcus aureus biofilms were examined with confocal scanning laser microscopy. Staining with LIVE/DEAD BacLight viability stain (Molecular Probes Europe BV, Leiden, The Netherlands) differentiated between live and dead bacteria within the biofilms, and extracellular polymeric substances (slime) from the biofilms was evaluated after staining with calcofluor white (Sigma Chemical Company, Rocky Hill, New Jersey). Human β-defensin 3 and clindamycin reduced the S aureus biofilm area. Human β-defensin 3 was significantly more effective against bacteria from the S aureus biofilms than was clindamycin. Vancomycin did not reduce the S aureus biofilm area.     

Pathogenic bacteria characteristics and drug resistance in acute,delayed, and chronic periprosthetic joint infection: A retrospective analysis of 202 patients

To assist orthopaedic surgeons in choosing appropriate antibiotics, this study attempted to identify the common microorganisms that cause periprosthetic joint infection (PJI) and their respective drug resistance spectrums. The clinical data of 202 patients with PJI after primary hip and knee arthroplasty between January 2017 and December 2021 were retrospectively analysed. There were 84 males and 118 females, aged (63.03 ± 13.10) years (range: 24–89 years). A total of 102 and 100 patients underwent total hip and total knee arthroplasty, respectively. Based on the time of postoperative infection, the patients were divided into acute (25 cases), delayed (91 cases), and chronic (86 cases) PJI groups. The results of pathogen species, composition ratio, and drug susceptibility tests were collected. Gram-positive bacteria were the primary causative pathogens of PJI (58.91%, 119/202), and their culture-positive rates in patients with acute, delayed, and chronic PJI were 32.00% (8/25), 62.64% (57/91), and 62.79% (54/86), respectively. Staphylococcus epidermidis and Staphylococcus aureus were the major gram-positive bacteria detected, followed by gram-negative bacteria (29/202, 14.36%), and fungi (4/202, 1.98%). Gram-positive bacteria showed higher resistance to penicillin (81.25%), oxacillin (63.33%), erythromycin (61.17%), and clindamycin (48.35%) and 100% sensitivity to linezolid, vancomycin, daptomycin, and tigecycline. In gram-negative bacteria, the drug resistance rates to cefazolin, gentamicin, furantoin, cefuroxime, ticacillin/clavulanic acid, ceftriaxone, ciprofloxacin, and tobramycin were >50%. However, no vancomycin-resistant bacteria were discovered in the current study. The drug resistance rate to carbapenems was low, ranging from 0% to 3.57%. Gram-positive bacteria are the main causative pathogens of PJI, and the resistance rate of pathogens of chronic PJI is higher than those of delayed and acute PJI. Use of cefuroxime and clindamycin in patients with PJIs should proceed with caution because of the high drug resistance rate. Vancomycin can be used as a first-line antibiotic against gram-positive bacteria. Carbapenems can be used as the first choice against gram-negative bacteria because of to their high sensitivity.     

Evaluation of perioperative prophylaxis with fosfomycin tromethamine in ureteroscopic stone removal: an investigator-driven prospective,multicenter, randomized,controlled study

Purpose

To compare efficacy, safety, and cost-effectiveness of fosfomycin tromethamine with other standard-of-care antibiotics in patients undergoing ureteroscopic lithotripsy.

Methods

This study was a prospective, multicenter, randomized, controlled trial. Eligible patients scheduled for ureteroscopic lithotripsy were randomly assigned to receive either fosfomycin (fosfomycin group, N = 101 patients) or standard-of-care antibiotic therapy as prophylaxis (control group, N = 115 patients). The incidence of infectious complications and adverse events was analyzed between the two groups, as well as the cost–benefit analysis.

Results

The incidence of infections following lithotripsy was 3.0% in the fosfomycin group and 6.1% in the control group (p > 0.05). Only asymptomatic bacteriuria was reported in fosfomycin group. In the control group was reported asymptomatic bacteriuria (3.5%), fever (0.9%), bacteremia (0.9%), and genitourinary infection (0.9%). The rate of adverse events was very low, with no adverse event reported in the fosfomycin group and only one in the control group (forearm phlebitis). The average cost per patient of antibiotic therapy with fosfomycin was 151.45 ± 8.62 yuan (22.7 ± 1.3 USD), significantly lower compared to the average cost per patient of antibiotics used in the control group 305.10 ± 245.95 yuan (45.7 ± 36.9 USD; p < 0.001).

Conclusions

Two oral doses of 3 g fosfomycin tromethamine showed good efficacy and safety and low cost in perioperative prophylaxis of infections following ureteroscopic stone removal.

     

Antibiotic loaded calcium sulfate bead and pulse lavage eradicates biofilms on metal implant materials in vitro

Pulse lavage (PL) debridement and antibiotic loaded calcium sulfate beads (CS‐B) are both used for the treatment of biofilm related periprosthetic joint infection (PJI). However, the efficacy of these alone and in combination for eradicating biofilm from orthopaedic metal implant surfaces is unclear. The purpose of the study was to understand the efficacy of PL and antibiotic loaded CS‐B in eradicating bacterial biofilms on 316L stainless steel (SS) alone and in combination in vitro. Biofilms of bioluminescent strains of Pseudomonas aeruginosa Xen41 and a USA300 MRSA Staphylococcus aureus SAP231 were grown on SS coupons for 3 days. The coupons were either, (i) debrided for 3 s with PL, (ii) exposed to tobramycin (TOB) and vancomycin (VAN) loaded CS‐B for 24 h, or (iii) exposed to both. An untreated biofilm served as a control. The amount of biofilm was measured by bioluminescence, viable plate count and confocal microscopy using live/dead staining. PL alone reduced the CFU count of both strains of biofilms by approximately 2 orders of magnitude, from an initial cell count on metal surface of approximately 10⁹ CFU/cm². The antibiotic loaded CS‐B caused an approximate six log reduction and the combination completely eradicated viable biofilm bacteria. Bioluminescence and confocal imaging corroborated the CFU data. While PL and antibiotic loaded CS‐B both significantly reduced biofilm, the combination of two was more effective than alone in removing biofilms from SS implant surfaces. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2349–2354, 2018.

     

Comparative Study of Antibiotic Elution Profiles From Alternative Formulations of Polymethylmethacrylate Bone Cement

BackgroundPolymethylmethacrylate (PMMA) bone cement is commonly used in orthopedic surgery for implant fixation and local antibiotic delivery following surgical debridement. The incidence of nephrotoxicity necessitates the balance of antiinfective properties with the potential for toxicity. Thus, understanding antibiotic elution characteristics of different PMMA formulations is essential. We sought to address this by assessing elution of vancomycin, daptomycin, and tobramycin from Palacos LV (Palacos), Stryker Surgical Simplex P (Simplex), BIOMET Cobalt HV (Cobalt), and Zimmer Biomet Bone Cement R (Zimmer) radiopaque bone cements.MethodsAntibiotics were mixed with each cement formulation, and molds were used to produce beads of cement. Beads were incubated in phosphate-buffered saline at 37°C, and antibiotic elution was measured daily for 10 days with vancomycin and 5 days with daptomycin and tobramycin. Active antibiotic was quantified by serial dilution and comparison to the minimum inhibitory concentration.ResultsThe elution profiles of Simplex were significantly lower than all other cements with all antibiotics (P < .00093). Palacos exhibited a significantly higher vancomycin elution profile than all other cements (P < .00001). The difference in daptomycin elution profiles for Cobalt and Palacos was not significant (P > .43), but both were significantly higher than Zimmer (P < .0006).ConclusionOverall, Stryker Surgical Simplex P exhibits a significantly lower elution profile than all other cements tested. In general, Palacos LV exhibits an increased elution profile compared with other cements. This elution information may assist the surgeon in choosing different cement formulations for the local delivery of antibiotics.     

New approaches for empiric therapy in Gram-positive sepsis

Nosocomial bloodstream infections (BSIs) have become an important cause of morbidity and mortality, particularly in intensive care units (ICUs). Gram-positive organisms are the prevalent causes of antibiotic-resistant BSI, especially Staphylococcus aureus, coagulase-negative staphylococci and enterococci. In recent years, several reports have shown an increase in antimicrobial resistance among Gram-positive bacteria isolated from patients in ICUs. In this context, methicillin-resistant Staphylococcus aureus (MRSA) is a major problem. In the ICU more than 50% of S. aureus isolates in Europe are resistant to methicillin. Although vancomycin became the drug of choice for MRSA and is still widely used for this indication, many studies suggest that when vancomycin MIC values are at the high end of the susceptibility range, vancomycin is less effective against MRSA. High MRSA prevalence combined with the widespread use of vancomycin for empirical Gram-positive coverage may lead to changes in patient outcomes. Here we describe the microbiological, pharmacological and clinical characteristics of three new antibacterials helpful in severe infections in ICU patients: linezolid, tigecycline and daptomycin. These new drugs have some limitations, and the possibility developing resistance is real. Knowledge of both old and new antibacterials is necessary to utilize them most effectively.