Insight into the Clonal Lineage and Antimicrobial Resistance of Staphylococcus aureus from Vascular Access Infections before and during the COVID-19 Pandemic (preprint)

Patients receiving hemodialysis are at risk of vascular access infections (VAIs) and particularly vulnerable to the opportunistic pathogen Staphylococcus aureus. Hemodialysis patients were also at increased risk of infection during the COVID-19 pandemic. Therefore, this study determined the change in the molecular and antibiotic resistance profiles of S. aureus isolates from VAIs during the pandemic compared with before. 102 S. aureus isolates were collected from VAIs between November 2013 and December 2021. Before the pandemic, 69 isolates were collected, 58%, 39.1%, and 2.9% from arteriovenous grafts (AVGs), tunneled cuffed catheters (TCCs), and arteriovenous fistulas (AVFs), respectively. The prevalence of AVG and TCC isolates changed to 39.4% and 60.6%, respectively, of 33 isolates during the pandemic. Sequence type (ST)59 was the predominant clone in TCC-methicillin-resistant S. aureus (MRSA) and AVG-MRSA before the pandemic, whereas the predominant clone was ST8 in AVG-MRSA during the pandemic. ST59 carrying the ermB gene was resistant to clindamycin and erythromycin. By contrast, ST8 carrying the msrA gene was exclusively resistant to erythromycin. The ST distribution for different VAIs changed from before to during the pandemic. The change in antibiotic resistance rate for different VAIs was closely related to the distribution of specific STs.

Arteriovenous fistula thrombosis in hemodialysis patients with COVID-19: epiphenomenon or marker of severe clinical disease?

Background: Pandemic condition due to Coronavirus disease (COVID-19) caused a fastest augmentation of hospitalization, impairing the healthcare organization. As a consequence, diagnostic and therapeutic delays have been showed. COVID-19-associated coagulopathy is an endothelial disease related to SARSCoV-2 infection. Our study evaluated the thrombosis of arteriovenous fistula (AVF) as risk marker of mortality. Methods: the analysis included 24 dialysis-dependent patients admitted in a period between March 2020 and June 2021. Patients were divided based on AVF thrombosis: the A group without AVF thrombosis (13 patients), and the B group with AVF thrombosis events (11 patients). Pearson or Spearman' correlation tests were performed to detect possible confounding variable to include in multivariate models. Kaplan Meier and Cox regression analysis were performed to compute mortality analysis. Results: Delta D-dimer (Rho: 0.613, p=0.007), over-infections (Rho 0.456; p= 0,026), C-reactive Protein (CRP) (Rho=0.417, p=0.043), death (Rho=0.492, p=0.027), positive pulmonary imaging (Rho 0.388, p=0.074), and high OLT (0.408, p=0.047) were related to AVF thrombosis, using Pearson or Spearman correlation tests. Kaplan Meier test showed a death average of 19 days in group B compared to a global average of 38 days (p=0.029), and Cox analysis showed an HR of 5.01, 95% CI 1.01-24.99, p=0.049. Furthermore, AVF thrombosis explained about the 68% of the mortality, evaluated through the Harrel's C test. Conclusion: We can speculate that AVF thrombosis in hemodialysis patients with COVID-19 could be an early marker of both pro-coagulative process and severe clinical disease and it could be used to stratify patients and identify the ones that can be considered "frail".

Bilateral pediatric pial arteriovenous fistulas accompanying a giant arachnoid cyst with torticollis: A case report.

RATIONALE: Pial arteriovenous fistula (PAVF) occurs when intracranial arteries communicate directly with veins. PAVFs are very rare congenital vascular lesions that are commonly seen in infants and children. Arachnoid cysts are congenital cavitation often filled with cerebrospinal fluid. We present a very rare associated occurrence of bilateral pediatric PAVF and a giant arachnoid cyst presenting as torticollis in a child. So far, this is the first case. PATIENT CONCERNS: A 6-year-old male child was referred to our facility from a local hospital due to severe torticollis. DIAGNOSES: An enhanced computed tomography scan revealed 2 slightly high-density masses at the anterior pontine cistern, right circumferential cistern, as well as left posterior occipital region. The same computed tomography scan revealed a giant arachnoid cyst in the left occipital as well as the temporal region with a thin cerebral cortex adjacent to the cyst. INTERVENTIONS: Digital subtraction angiography confirmed that the 2 high-flow lesions were PAVFs. The patient was treated with a combination of detachable coils and Onyx Liquid Embolic System (Onyx HD-500) (Covidien/ev3 Neurovascular) via the transarterial endovascular route while the giant arachnoid cyst was managed conservatively. OUTCOMES: The torticollis resolved 2 days after the procedure. He is currently well with no neurologic deficit. LESSONS: We advocate that in cases of PAVF with accompanying cyst, the cyst should be managed conservatively if it is not associated with intracranial hemorrhage or focal neurologic deficit.

Distal arteriovenous fistula to preserve patency in COVID-19-associated acute limb ischemia.

The purpose of this study was to report our institutional experience with patients with COVID-19 who developed acute limb ischemia during hospitalization and to determine the characteristics and clinical outcomes. Between March 2020 and January 2021, we treated 3 patients who were COVID-19-positive and developed acute limb ischemia after they received thromboprophylaxis. We performed an embolectomy by exposing the popliteal artery below the knee to treat an occlusion of the popliteal and tibial arteries. An infusion of unfractionated heparin was initiated immediately after surgery, maintaining a partial thromboplastin time ratio > 2.5 times the normal value and transferred the patients to the intensive care unit. However, after these patients developed recurrent acute limb ischemia in the same leg, we decided to perform an embolectomy of popliteal and tibial arteries at the ankle and created an arteriovenous fistula (AVF) with tibial veins using polypropylene 7-0. The first patient died from pneumonia after 3 weeks in the intensive care unit; at that time, the foot was viable with triphasic flow in the distal posterior tibial artery and the AVF was patent. The second and third patients are doing well, they can walk without any problems, and the tibial arteries and AFV were patent on duplex ultrasound after 6 months. The AVF allowed part of the flow of tibial arteries to divert into the small veins of the foot that have a low resistance to maintain patency of tibial vessels, despite a hypercoagulable state and extensive thrombotic microangiopathy in patients with COVID-19.

Risk Factors for Low Humoral Response to BNT-162b2 In Hemodialysis Patients (preprint)

IntroductionMaintenance Hemodialysis (HD) patients are at higher risk of both infection and mortality associated with the new coronavirus 2. Immunization through large-scale vaccination is the cornerstone of infection prevention in this population. This study aims to identify risk factors for low response to the BNT-162b2 (Pfizer BioNTech) vaccine in a HD cohort. Materials and MethodsObservational prospective study of a HD group followed in a Portuguese Public Founded Hemodialysis Center who received BNT-162b2 vaccination. Specific anti-Spike IgG was evaluated as arbitrary units per milliliter (AU/mL) on two separate occasions: 3 weeks after the first dose and 3 weeks after the second. IgG titers, Non-Responders (NR), and Weak-Responders (WR) after each dose were evaluated against risk factors that included demographic, clinical and analytical variables. ResultsHumoral response evaluated by IgG anti-Spike levels showed a strong correlation with Charlson comorbidity index (CCI) and intact parathormone (iPTH) after each inoculation (1st dose: {rho}=-0.64/0.54; 2nd dose: {rho}=-0.66/0.63, respectively; p<0.01 throughout). After completing both doses: 1) NR were associated with female sex (p<0.01), lower albumin and iPTH (p=0.01); 2) WR showed higher CCI, older age, lower iPTH and lower albumin (p=<0.01, p=0.03, p<0.01, p=0.05, respectively) and, consistently, associated with CCI over 8, age over 75, iPTH under 150 ng/L, female sex, dialysis vintage under 24 months and central venous catheter (CVC) over arteriovenous fistula (p=0.01, p=0.03, p<0.01, p=0.01, p=0.01, p<0.01, respectively). A binary regression model using CCI, sex (male) and CVC was statistically significant in prediction of WR after the 2nd dose with OR (95% CI): 1.81 (1.06-3.08); 0.05 (0.01-0.65); 13.55 (1.06-174.18), respectively (p=0.01). ConclusionOlder age, higher CCI, lower iPTH and albumin, CVC as vascular access and recent hemodialysis initiation (less than 2 years) associate with lower response to vaccination in our study. A higher comorbidity burden is suggested as a more significant surrogate marker for low immunogenicity rather than age alone. Identifying HD patients as a population at high-risk for low response to vaccination is essential for proper policy-making, facilitating the implementation of adequate and individualized contingency protocols. What is already known about this subjectO_LIMaintenance hemodialysis patients have lower humoral response to BNT-162b2 COVID-19 vaccine when compared to the general population. C_LIO_LIMaintenance dialysis patients are at high risk of exposure to coronavirus 2 in addition to a more severe disease course. C_LI What this study addsO_LIWe suggest Charlson commorbidity index, older age, intact parathormone, central venous catheter as vascular access and lower dialysis vintage as possible surrogate markers of immunogenicity in HD patients. C_LIO_LIThere is a low humoral response after a single dose of the vaccine (50%) that can be increased after the second (86%). C_LI What impact this may have on practice or policyO_LIStrict Protocols for follow-up measures in HD patients, including closer humoral titers assessment, risk stratification, adequate isolation, and surveillance of symptoms might be necessary in order to improve this population survival/life expectancy. C_LIO_LIScreening HD patients, seroconversion rates may be improved by giving extra inoculations for patients at risk for low response. C_LI

Are There Differences in Arteriovenous Fistulae Created for Hemodialysis between Nephrologists and Vascular Surgeons?

OBJECTIVE: Many studies have reported insufficient support from surgical services, resulting in nephrologists creating arteriovenous fistulas in many centers. The aim of this study was to compare risk factors of arteriovenous fistula dysfunction in patients whose fistulas were created by nephrologists versus vascular surgeons. METHODS: This was a retrospective, analytical study of interventions by nephrologists and vascular surgeons during a period of 15 years. Out of a total of 1,048 fistulas, 764 (72.9%) were created by nephrologists patients, while vascular surgeons were responsible for 284 (27.1%) fistulae. Laboratory, demographic, and clinical parameters which might affect functioning of these arteriovenous fistulae were analyzed. RESULTS: Patients whose arteriovenous fistula was formed by nephrologists differed significantly from those created by vascular surgeons in relation to the preventive character of the arteriovenous fistula (p = 0.011), lumen of the vein (p < 0.001) and systolic blood pressure (p = 0.047). Multivariate logistic regression of arteriovenous fistula dysfunction showed that risk factors were female gender (odds ratio [OR] = 1.56, 95% CI 1.16-2.07), whether the fistulae were created by vascular surgeons or nephrologists (OR = 1.38; 95% CI 1.01-1.89) and the site of the arteriovenous fistula (OR = 0.64; 95% CI 0.48-0.85). CONCLUSIONS: Arteriovenous fistulae created by vascular surgeons, female gender, and the location are risk factors of dysfunction.

Recurrent thrombosis of an arteriovenous fistula as a complication of COVID-19 in a chronic hemodialysis patient: A case report.

Patients with end-stage kidney disease are at increased risk of death from coronavirus disease 2019 (COVID-19). In addition, severe COVID-19 has been associated with an increased risk of arterial and venous thromboses. In this report, we describe the case of a hemodialysis patient who developed an otherwise-unexplained thrombosis of an arteriovenous fistula during a symptomatic COVID-19 infection. Despite prompt treatment with three technically successful thrombectomies along with systemic intravenous heparin and two rounds of catheter-directed thrombolysis with tissue plasminogen activator, the fistula rapidly re-thrombosed each time and he required tunneled dialysis catheter placement. He subsequently required admission for hypoxemia from COVID-19 pneumonia and ultimately developed a catheter-related blood stream infection that likely contributed to his death. As the fistula had been previously well functioning and no angiographic explanation for the thrombosis was found, we speculate in this case the recurrent thromboses were related to the hypercoagulable state characteristic of severe COVID-19. Interventionalists performing hemodialysis access procedures should be aware of the prothrombotic state associated with COVID-19 and should consider it when deliberating how to best plan and approach access interventions in patients with symptomatic COVID-19.

Arteriovenous fistulas thrombosis in hemodialysis patients with COVID-19.

BACKGROUND: The current Coronavirus disease 2019 (COVID-19) outbreak is associated with significant mortality, especially in patients suffering from end stage renal disease (ESRD) and hemodialysis patients. Several previous studies reported an over-risk of arterial and venous thrombosis, in particular pulmonary embolism and venous thrombosis of catheter in COVID19 patients in intensive care unit. However, arteriovenous fistula (AVF) thrombosis has rarely been reported yet in these patients. AVF thrombosis is a serious complication that impacts significantly patients outcome. Here, we aim to describe characteristics and prognosis of a cohort of COVID-19 hemodialysis (HD) patients presenting with AVF thrombosis. METHODS: In the Ile de France region (Paris area) during the March 11th-April 30th 2020 period, fistula thrombosis cases were collected among COVID-19 hemodialysis patients in seven dialysis units and in interventional vascular departments. These patients' characteristics were analyzed through a review of the patient's medical records. RESULTS: Seventeen patients were included in our study (median age 69 years). Ten patients (59%) were men. Ten patients (59%) were diabetic and 88% had a high blood pressure. The mortality rate in these patients was 47%. All thrombosis treated with a declotting procedures (64%) were successfully cleared, but with early relapse in 36%. CONCLUSION: Our study highlights AVF thrombosis as a severe complication in COVID-19 hemodialysis patients that contributed to the severity and accelerated death.