Mycobacterium abscessus Surgical Site Infections Due to Modular Cooler-Heater Units in Cardiac Surgery

Background: In the spring of 2020, we identified 3 patients with organ-space surgical site infections (SSIs) secondary to Mycobacterium abscessus (Table 1). All 3 patients underwent cardiac surgery in the same operating room (OR) during which the CardioQuip Modular Cooler-Heaters (MCHs) were used. We describe key aspects of our cluster investigation, which ultimately led to release of a national safety alert by the Food and Drug Administration (FDA). Methods: For environmental cultures, we obtained samples from 9 MCHs in circulation; 2 scrub sink samples; ice from the OR ice machine; water samples from sinks in the cardiovascular critical care unit, and water samples from floors above the cardiac ORs. All samples were sent for molecular genotyping. For pathway studies, an external environmental engineering team was consulted who conducted smoke pathway tests in 3 different ORs. The team also conducted a particle generator experiment, simulating the set-up of a cardiac bypass surgery case. To assess disinfection practices, we reviewed the manufacturer instructions for use (IFU) protocol of the MCHs and audited our own policies and procedures to ensure compliance. Results: For environmental cultures, molecular typing from 5 of 9 MCHs and all 3 patient SSI isolates returned positive for the identical hybrid species M. abscessus bolleti. All other samples with mycobacterial growth returned with different species. For pathway studies, the particle-generator experiment demonstrated particle movement from the MCH to the sterile field with facilities-guidelines–compliant OR ventilation and despite MCH manufacturing design. For disinfection practices, despite compliance with the stated IFU, and in consultation with experts, we implemented disinfection of associated Quick-connect devices (otherwise not stated in the IFU), and we also initiated a precleaning step prior to disinfection. Conclusions: Our investigation concluded that 3 patients developed SSIs with Mycobacterium abscessus that was aerosolized from the CardioQuip MCH. This finding led to the national FDA safety report alerting providers to risks associated with the device and the need for continued vigilance around disinfection. In addition, we implemented other control measures including placement of MCHs outside all ORs; creation of a separate MCH fleet for non-OR use; and use of modified disinfection protocols. To date, no additional cases have been identified. Funding: No Disclosures: None Table 1.

Un Squirrel Search Algorithm discreto aplicado al problema Job Shop con operadores calificados

Introducción: El problema Job Shop Con Operadores Calificados o Job Shop With Skilled Operators (JSSO) es una extensión del problema clásico Job Shop en el cual, una operación debe ser ejecutada por un conjunto limitados de trabajadores, con el objetivo de minimizar el tiempo de terminación total de los trabajos o Makespan, situación que puede representar distintas aplicaciones en la vida cotidiana. Es un problema complejo y es catalogado como NP-HARD. Objetivo: En este artículo, se aborda el problema JSSO desde la adaptación de un algoritmo conocido como Squirrel Search Algorithm (SSA). Metodología: Se propone un esquema de codificación discreto para el algoritmo SSA utilizando el método Smallest Position Value (SPV). Además, para evitar soluciones que violen las relaciones de precedencia; se corrigen con el método Valid Particle Generator (VPG), el cual garantiza soluciones factibles. Dos versiones del algoritmo se colocan a prueba en 28 instancias propuesta en la literatura para validar su rendimiento. Resultados: Los experimentos computacionales realizados muestran que los dos algoritmos propuestos alcanzan soluciones óptimas en 25 de las 28 instancias analizadas. Además, para las instancias en donde no se logró soluciones óptimas, el gap promedio no supera el 2% para ambas versiones de los algoritmos propuestos. Conclusiones: El esquema de codificación propuesto garantiza la discretización del algoritmo, generando soluciones que convergen hacia el óptimo. Además, la codificación propuesta, permite utilizar de manera natural los operadores de movimiento propuestos originalmente para el algoritmo utilizado. El rendimiento obtenido por los algoritmos es adecuado y de alta calidad.

A Novel Global Optimization Algorithm and its Application to Airfoil Optimization

In this paper, a novel global optimization algorithm has been developed, which is named as Particle Swarm Optimization combined with Particle Generator (PSO-PG). In PSO-PG, a particle generator was introduced to iteratively generate the initial particles for PSO. Based on a series of comparable numerical experiments, it was convinced that the calculation accuracy of the new algorithm as well as its optimization efficiency was greatly improved in comparison with those of the standard PSO. It was also observed that the optimization results obtained from PSO-PG were almost independent of some critical coefficients employed in the algorithm. Additionally, the novel optimization algorithm was adopted in the airfoil optimization. A special fitness function was designed and its elements were carefully selected for the low-velocity airfoil. To testify the accuracy of the optimization method, the comparative experiments were also carried out to illustrate the difference of the aerodynamic performance between the optimized and its initial airfoil.

The Feasibility of Differential Flow Velocity Dividing Working Areas in a Cleanroom

The possibility of dividing working areas by airflow velocity differences in a cleanroom with fan-filter unit (FFU) systems was investigated. Without physical partitions, the cleanroom area was divided into working and non-working areas defined by the FFU exit flow velocities, which were maintained at constant value in the working areas and reduced in the non-working areas. As uniform micro-sized particles were released from a particle generator in the non-working area, the concentrations of particles in the working area were monitored by a particle counter. The results showed that high downward flow velocity in the working area can effectively prevent particles from spreading. The results also suggested an optimum velocity ratio of 20% between adjacent flow regions, in terms of the balance between energy savings and the effective partition insulation.