High efficiency all-fiber cylindrical vector beam laser using a long-period fiber grating.

We demonstrate a novel all-fiber laser generating cylindrical vector beams with high slope efficiency and low threshold by introducing a long-period fiber grating into the laser cavity. Highly efficient mode conversion is realized by an LPFG at ∼1548 nm. Mode selection and spectrum filtering are achieved in combination with a two-mode fiber Bragg grating (TM-FBG). The fiber laser operates at a single wavelength of 1547.95 nm with a 30 dB linewidth of less than 0.18 nm and a side-mode suppression ratio (SMSR) of more than 56 dB. The lasing threshold and slope efficiency of the laser are 24.5 mW and 35.41%, respectively. The output power is 72 mW with an absorbed pump power of 225 mW. The variation of slope efficiency with respect to the reflectivity of the TM-FBG is investigated. Through adjusting the intra-cavity polarization controller, high-purity radially and azimuthally polarized beams are both obtained.

Cytomegalovirus Infection after CD34(+)-Selected Hematopoietic Cell Transplantation.

The effectiveness of preemptive treatment (PET) for cytomegalovirus (CMV) in recipients of ex vivo T cell-depleted (TCD) hematopoietic cell transplantation (HCT) by CD34(+) selection is not well defined. We analyzed 213 adults who received TCD-HCT at our institution from June 2010 through May 2014. Patients were monitored by a CMV quantitative PCR assay if recipient (R) or donor (D) were CMV seropositive. CMV viremia occurred early (median, 27 days after HCT) in 91 of 213 (42.7%) patients for a 180-day cumulative incidence of 84.5%, 61.8%, and 0 for R+/D+, R+/D-, and R-/D+ patients, respectively. CMV disease occurred in 5% of patients. In Cox regression analysis, R+/D+ status was associated with increased risk for CMV viremia compared with R+/D- (hazard ratio [HR], 1.79, 95% confidence interval [CI], 1.16 to 2.76, P = .01), whereas matched unrelated donor allograft was associated with decreased risk (HR, .62; 95% CI, .39 to .97, P = .04). Of 91 patients with CMV viremia, 52 (57%) had persistent viremia (>28 days duration). Time lag from detection of CMV viremia to PET was associated with incremental risk for persistent viremia (HR, 1.09; 95% CI, 1.01 to 1.18; P = .03). Overall, 166 of 213 (77.9%) patients were alive 1 year after HCT, with no difference between patients with and without CMV viremia or among the different CMV serostatus pairs (P = not significant). CMV viremia occurred in 70% of R + TCD-HCT. Delay in PET initiation was associated with persistent viremia. With PET, CMV R/D serostatus did not adversely impact survival in TCD-HCT on 1-year survival in the present cohort.

Actively mode-locked all fiber laser with cylindrical vector beam output.

We demonstrated an all fiber actively mode-locked laser that emits a cylindrical vector beam. An intra-cavity few-mode fiber Bragg grating inscribed in a short section of four-mode fiber is employed to provide mode selection and spectrum filtering functions. Mode coupling is achieved by offset splicing between the single-mode fiber and the four-mode fiber in the laser cavity. A LiNbO3 Mach-Zehnder modulator is used to achieve active mode-locking in the laser. The laser operates at 1547 nm with 30 dB spectrum width of 0.2 nm. The mode-locked pulses have a duration of 2 ns and repetition of 12.06 MHz. Through adjusting the polarization state in the laser cavity, both radially and azimuthally polarized beams have been obtained with high mode purity.

Mode-locked all-fiber laser producing radially polarized rectangular pulses.

We propose and demonstrate a radially polarized mode-locked fiber laser through the use of a figure-8 cavity in combination with cascade fiber Bragg gratings (FBGs). The mode-locked laser emits rectangular pulses with width tunable from 2.8 to 23 ns under an increasing pump power at 1056.3 nm with 0.2-nm 30-dB linewidth. A polarization purity as high as 96% for the output transverse mode has been achieved simultaneously.

Clostridium difficile infection after allogeneic hematopoietic stem cell transplant: strain diversity and outcomes associated with NAP1/027.

Allogeneic hematopoietic stem cell transplantation (HSCT) recipients are at high risk for developing Clostridium difficile infection (CDI). We studied the incidence, risk factors, NAP1/027 prevalence, and clinical outcomes, including acute lower gastrointestinal graft-versus-host disease (GI GVHD), associated with early CDI in this population. A retrospective review was conducted of patients who underwent allogeneic HSCT at Memorial Sloan Kettering Cancer Center from January 1, 2005 to September 30, 2010. Early CDI was defined as infection occurring from day -10 to day +40 from stem cell infusion. Among 793 patients who received allogeneic HSCTs, early CDI occurred in 11.9%; 56% cases were between day -5 and day +5. Overall incidence was 25.2 cases/10,000 at-risk days. There was a high prevalence of NAP1/027 strains during peak incidence (61% in 2008). NAP1/027 was the most common strain in both adult and pediatric cases (24% and 23%, respectively). CDI was clinically mild, including those due to NAP1/027. Metronidazole was the primary treatment for 91 of 94 patients, 7 of 8 cases refractory to metronidazole had no response to vancomycin, and none was due to NAP1/027. Relapse of CDI was common (31%). The cumulative incidence of GI GVHD in patients with and without early CDI was 6.8% and 8%, respectively (P = .5). Most cases of CDI occurred during conditioning or immediately after transplant. Despite high prevalence of NAP1/027, we found only mild disease. Most patients were treated successfully with metronidazole, irrespective of NAP1/027 status. There was no significant association between early CDI and subsequent development of GI GVHD. This study demonstrates the high incidence of CDI early after allogeneic HSCT with wide diversity among infecting strains. Despite the high prevalence of NAP1/027, the disease is mild but relapses are common. No association was found between CDI and subsequent development of GI GVHD.

Relationship of BK polyoma virus (BKV) in the urine with hemorrhagic cystitis and renal function in recipients of T Cell-depleted peripheral blood and cord blood stem cell transplantations.

Hematopoietic stem cell transplant (HSCT) recipients are at significant risk for BK virus (BKV) reactivation, hemorrhagic cystitis (HC), and renal dysfunction. We prospectively monitored 98 patients who had received HSCT by serial BKV PCR in the urine through day (D) +100 to analyze the relationship between BK viruria and HC, serum creatinine (Cr), and creatinine clearance (CrCl) through D +180 or death. Patients, median age 52 years (range, 20 to 73), received T cell-depleted (50%) or cord blood allografts (21%). Median pre-HSCT BKV IgG titers were 1:10,240. Incremental increase in BKV IgG titers correlated with developing BK viruria ≥ 10(7) copies/mL. By D +100, 53 (54%) patients had BK viruria. BKV load in the urine increased at engraftment and persisted throughout D +100. HC developed in 10 patients (10%); 7 of 10 with BK viruria. In competing risk analyses, BK viruria ≥ 10(7) copies/mL, older age, cytomegalovirus reactivation, and foscarnet use were risk factors for HC. Cr and CrCl at 2, 3, and 6 months after HSCT were similar between patients with and without BK viruria.

Adenovirus viremia and disease: comparison of T cell-depleted and conventional hematopoietic stem cell transplantation recipients from a single institution.

Adenovirus (ADV) is an important cause of viral mortality in hematopoietic stem cell transplantation (HSCT). Recipients of T cell-depleted (TCD) HSCT are at increased risk for viral infections. We compared the rates and outcomes of ADV viremia and disease between TCD and conventional (CONV) HSCT at our institution. This was an observational study of 624 adult and pediatric recipients of myeloablative HSCT at Memorial Sloan-Kettering Cancer Center between January 1, 2006, and March 11, 2011. Viral cultures and ADV PCR were ordered as clinically indicated. ADV viremia by quantitative PCR assay was defined as 1 or more positive values ≥1,000 copies/mL or 2 or more consecutive positive values. Competing-risk regression analyses were used to identify predictors for ADV viremia. ADV viremia at 1 year after HSCT occurred in 8% of TCD HSCT recipients and in 4.0% of CONV HSCT recipients (P = .041). Among the TCD recipients, ADV viremia was seen in 15% of children, compared with 5% of adults (P = .008). Young age (hazard ratio [HR], 3.0; P < .001) and acute graft-versus-host disease (GVHD) (HR, 3.2; P = .001) were identified as risk factors for ADV viremia. ADV viremia was predictive of mortality (HR, 6.0; P < .001). ADV disease developed in 3.5% of TCD HSCT recipients and in 0.4% of CONV HSCT recipients (P = .022), with an attributable mortality of 27%. Among TCD HSCY recipients, grade II to IV GVHD was a risk factor for ADV disease (HR, 13; P < .001), but age was not. More than 90% of the cases of ADV disease involved a viral load of ≥10,000 copies/mL. Rates of ADV disease were 10-fold greater in TCD HSCT recipients compared with CONV HSCT recipients, predominantly in patients who developed acute GVHD. The benefit of preemptive therapy for an ADV viral load ≥10,000 copies/mL for preventing ADV disease in TCD HSCT recipients should be evaluated in prospective clinical trials.

The changing epidemiology of vancomycin-resistant Enterococcus (VRE) bacteremia in allogeneic hematopoietic stem cell transplant (HSCT) recipients.

The impact of the rising prevalence of vancomycin-resistant Enterococcus (VRE) prior to hematopoietic stem cell transplantation (HSCT) and changes in transplant techniques on risk of VREB (VRE bacteremia) early after HSCT is not known. This is a retrospective study of 247 adult patients who underwent allogeneic HSCT in the years 2008 and 2009 at the Memorial Sloan-Kettering Cancer Center. Sixty-eight of 247 (27.5%) patients were VRE colonized on pretransplant screening. VRE was the leading cause of bacteremia in the first 30 days after HSCT; 23 of 43 (53.5%) patients with positive blood cultures had VRE. Only 13 (57%) of the 23 patients with early VREB were colonized with VRE on pre-HSCT screening cultures. Mortality was directly attributable to VRE infection in 9% of patients with early VREB. VRE is emerging as the most common cause of preengraftment bacteremia in patients undergoing allogeneic HSCT, and is associated with substantial mortality. Pre-HSCT screening for VRE with stool cultures will not identify all patients who are at risk for VREB. The use of alternate agents with activity against Gram-positive bacteria for fever and neutropenia early after HSCT should be evaluated further in prospective studies.

Hematologic safety profile of linezolid in the early periengraftment period after allogeneic stem cell transplantation.

Vancomycin-resistant enterococci (VRE) are common pathogens of bloodstream infections in the peritransplantation period. Linezolid is approved by the FDA for treating VRE infections, but has been associated with low rates of hematologic toxicity in the general population; thus, there are concerns about its potential myelotoxicity in the allogeneic hematopoietic stem cell transplantation (HSCT) setting. We examined the impact of linezolid treatment on the times to neutrophil and platelet engraftment in 33 patients who underwent HSCT. In this retrospective case-controlled study conducted from 2000 through 2007, cases received > or = 7 consecutive days of linezolid therapy, starting before day +8 post-HSCT. Controls received > or = 7 consecutive days of vancomycin therapy before day +8 and were matched to cases by age and conditioning regimen. The cumulative incidence function was used to estimate the probabilities for the times to neutrophil and platelet engraftment. A competing-risk regression model was used to determine whether times to engraftment differed for cases and controls. A total of 33 cases were compared with 33 controls. The median duration of treatment after stem cell infusion was 14 days (range, 7 to 34 days) for linezolid and 16 days (range, 8 to 33 days) for vancomycin. The rates of neutrophil and platelet engraftment were similar between the cases and controls. After adjusting for baseline characteristics, no difference in the times to neutrophil or platelet engraftment was seen between the 2 groups. Our findings demonstrate no adverse effect on the times to neutrophil or platelet engraftment with linezolid use. Larger prospective studies are needed to fully determine the hematologic safety of linezolid in patients undergoing HSCT.

The effect of intratympanic gentamicin for treatment of Ménière's disease on lower frequency hearing.

Background The intratympanic application of the ototoxic aminoglycoside gentamicin has shown promising results as an ablative treatment for vertigo associated with Ménière's disease. Objective To evaluate the efficacy and safety of intratympanic gentamicin and to specifically analyse the effect of this treatment on high and low hearing frequencies in patients with unilateral definite Ménière's disease. Method Subjects were treated with intratympanic gentamicin and were evaluated on vertigo, tinnitus, mean pure tone audiometry threshold and speech discrimination score. Subjects were followed for evaluation for up to 2 years after treatment. Results The number of vertigo spells per month decreased and subjects experienced less tinnitus. During follow up there was an increase of hearing loss in the low (0.25-, 0.5-, 1-kHz) frequency range (13.3 dB; p = 0.03). There was no significant increase of hearing loss in the high (2-, 4-, 8-kHz) frequency range. A clinically significant change in speech discrimination score was found in 50 % of the subjects. Conclusion Our results indicate that intratympanic gentamicin especially affects the mean pure tone audiometry threshold in the low frequency range, which may have clinical implications. Though many of our results are (statistically) substantial the study was limited by the small cohort size.

Impact of peri-transplant vancomycin and fluoroquinolone administration on rates of bacteremia in allogeneic hematopoietic stem cell transplant (HSCT) recipients: a 12-year single institution study.

BACKGROUND: We analyzed the effect of peri-transplant prophylaxis on the epidemiology of bacteremia in a 12-year contemporary cohort of allogeneic HSCT recipients at our center. METHODS: This was an observational study of 1052 consecutive adult HSCT from 2000 to 2011. Formal prophylaxis with vancomycin only, fluoroquinolone (FQ) only, or vancomycin + FQ was implemented in 2006. The cumulative incidence of day 100 bacteremia was compared between the Early Period (2000-2005) and the Recent Period (2006-2011). Predictors for pre-engraftment bacteremia were analyzed with Cox-proportional hazard models in a subcohort of 821 HSCT who received myeloablative or reduced intensity conditioning (MA/RIC). RESULTS: The incidence of bacteremia decreased in the Recent Period (32% vs 27%; P = 0.002), whereas the rates of resistance in gram-negative rods (GNR) and vancomycin-resistant enterococci (VRE) were similar between the two Periods (P values are not statistically significant.) In multivariate analyses, prophylaxis with vancomycin only or vancomycin + FQ was protective (HR = 0.5; CI = 0.30-0.72) and (HR = 0.3; CI = 0.12-0.52, P < 0.01). Vancomycin or vancomycin + FQ eliminated viridans streptococcal bacteremia (VSB); vancomycin + FQ decreased GNR bacteremia (HR = 0.35; CI = 0.15-0.85). CONCLUSIONS: Vancomycin-based prophylaxis peri-transplant in MA/RIC HSCT was associated with elimination of VSB and may be considered at centers with high incidence of this infection.