Evaluation of multiple fixed in-room air cleaners with ultraviolet germicidal irradiation, in high-occupancy areas of selected commercial indoor environments

The use of ultraviolet germicidal irradiation (UVGI) to combat disease transmission has come into the international spotlight again because of the recent SARS-CoV-2 pandemic and ongoing outbreaks of multidrug resistant organisms in hospitals. Although the implementation of ultraviolet disinfection technology is widely employed in healthcare facilities and its effectiveness has been repeatedly demonstrated, the use of such technology in the commercial sector has been limited. Considering that most disease transmission occurs in commercial, public, and residential indoor environments as opposed to healthcare facilities, there is a need to understand whether ultraviolet (UV) disinfection technology can be effective for mitigating disease transmission in these environments. The results presented here demonstrate that the installation of fixed in-room UVGI air cleaners in commercial buildings, including restaurants and offices, can produce significant reductions in both airborne and surface-borne bacterial contamination. Total airborne reductions after UV implementation at six separate commercial sites averaged 73% (p < 0.0001) with a range of 71-88%. Total non-high touch surface reductions after implementation averaged 55% (p < 0.0001) with a range of 28-88%. All reductions at the mitigated sites were statistically significant. The mean value of indoor airborne bacteria was 320 CFU/m³ before intervention and 76 CFU/m³ after. The mean value of indoor non-high touch surface borne bacteria was 131 CFU/plate before intervention and 47 CFU/plate after. All test locations and controls had their required pandemic cleaning procedures in place for pre- and post-sampling events. Outdoor levels of airborne bacteria were monitored and there was no significant correlation between the levels of airborne bacteria in the outside air as opposed to the indoor air. Rooms with fixed in-room UVGI air cleaners installed had significant CFU reductions on local surface contamination, which is a novel and important finding. Installation of fixed in-room UVGI air cleaners in commercial buildings will decontaminate the indoor environment and reduce hazardous exposure to human pathogens.

A Novel Competence Pathway in the Oral Pathogen Streptococcus sobrinus

Streptococcus sobrinus is an etiologic cause of dental caries (tooth decay) in humans. Our knowledge of S. sobrinus is scant despite the organism's important role in oral health. It is widely believed that S. sobrinus lacks the natural competence pathways that are used by other streptococci to regulate growth, virulence, and quorum sensing. The lack of natural competence has also prevented genetic manipulation of S. sobrinus, limiting our knowledge of its pathogenicity. We discovered that most strains of S. sobrinus contain a new class of the ComRS competence system. Although S. sobrinus is typically placed among the mutans group streptococci, the S. sobrinus ComRS system is most similar to the competence pathways in the salivarius group. Unlike all other ComRS systems, the S. sobrinus pathway contains 2 copies of the transcriptional regulator ComR and has a peptide pheromone (XIP) that lacks any aromatic amino acids. Synthetic XIP enables transformation of S. sobrinus with plasmid or linear DNA, and we leverage this newfound genetic tractability to confirm that only 1 of the ComR homologs is required for induced competence while the other appears to suppress competence. Exogenous XIP increases the expression of bacteriocin gene clusters and produces an antimicrobial response that inhibits growth of S. mutans. We also identified 2 strains of S. sobrinus that appear to be "cheaters" by either not responding to or not producing XIP. We show how a recombination event in the nonresponsive strain could restore function of the ComRS pathway but delete the gene encoding XIP. Thus, the S. sobrinus ComRS pathway provides new tools for studying this pathogen and offers a lens into the evolution of ecological cheaters.

Critical Design Parameters in Design and Efficacy of Upper-Room UVC254 Luminaire Systems: Part I: Overview of Major Parameters and Relationships†

During the current SARS‐CoV‐2 and tuberculosis global pandemics, public health and infection prevention and control professionals wrestle with cost‐effective means to control airborne transmission. One technology recommended by Centers for Disease Control and Prevention and the World Health Organization for lowering indoor concentration of these and other microorganisms and viruses is upper‐room ultraviolet 254 nm (UVC₂₅₄) systems. Applying both a material balance as well as some nondimensional parameters developed by Rudnick and First, the impact of several critical parameters and their effect on the fraction of microorganisms surviving UVC₂₅₄ exposure was evaluated. Vertical airspeed showed a large impact at velocities <0.05 m s⁻¹ but a lesser effect at velocities >0.05 m s⁻¹. In addition, the efficacy of any upper‐room UVC system is influenced greatly by the mean room fluence rate as opposed to a simple volume‐ or area‐based dosing criteria. An alternative UVC₂₅₄ dosing strategy was developed based on the fluence rate as a function of the UVC₂₅₄ luminaire output (W) and the square root of the product of the room volume and the ceiling height.

Evaluation of the Tuberculosis Infection Control Training Center, Tajikistan, 2014-2015

SETTING

Training center on tuberculosis (TB) infection control (IC) for health care workers in the Central Asian Republics region.

OBJECTIVE

To assess the effects of TB IC training courses conducted at the Tuberculosis Infection Control Training Center in Machiton, Tajikistan.

DESIGN

Participants who participated in training (n = 89) during the first year of operation (April 2014-February 2015) were invited to participate in a post-training interview.

RESULTS

Of the 89 participants, 84 (94%) completed the interview and expressed satisfaction with the training. Eighty (95%) participants reported meeting with workplace leadership to discuss the training. Of these, 69 (85%) reported discussing changes required to meet TB IC standards. Self-reported changes in TB IC practices at work facilities post training included the creation of TB IC committees, designation of a TB IC focal person, TB IC planning, policies to separate infectious patients in waiting rooms, provision of masks for infectious patients, development of cough etiquette policies, improved glove availability, hand hygiene programs, and TB IC posters in waiting rooms.

CONCLUSIONS

Participant satisfaction and reported changes in TB IC activities illustrate the potential of these training courses to improve TB IC in the region. Future training courses may be tailored to specific audiences using a structured conceptual framework to impact administration, budgeting, and facilities management of TB IC practices.

Reducing respirator fit test errors: a multi-donning approach

As a continuation of recent studies to assess the accuracy of existing fit test methods, a multi-donning approach to fit testing is presented. As an example of that approach, a multi-donning quantitative fit test for filtering-facepiece respirators is presented and analyzed by comparing its error rates with those of the single-donning approach of current fit test methods. That analysis indicates the multi-donning fit test has the potential to reduce both the alpha error and the beta error to half that of single-donning fit tests. The alpha error is the error of failing a respirator that should pass; the beta error is the error of passing a respirator that should fail. Lowering fit test error rates for filtering-facepiece respirators is important because fit testing is an essential means of helping assure that an individual has selected an adequately fitting respirator. To reduce the alpha and beta error inherent in current fit test methods, the proposed fit test for filtering-facepiece respirators incorporates five donnings of the facepiece, unlike the single donning of existing fit test methods. The analysis presented here indicates that the multiple-donning approach reduces the element of chance in the fit test result and thereby increases the consistency and accuracy of the fit tests. The time to conduct the multi-donning test can approximate the time for current, single-donning tests by shortening the time the respirator is worn after each donning to about 10 sec. And, unlike current fit tests for filtering-facepieces that measure only faceseal leakage, the example multiple-donning fit test considered here is based on a measurement of total leakage (faceseal plus filter). Utilizing total respirator leakage can result in simpler quantitative fit test instrumentation and a fit test that is more relevant to the workplace. Further trials with human subjects are recommended in order to validate the proposed multi-donning approach.

Sampling and analytical method development for qualitative assessment of airborne mycobacterial species of the Mycobacterium tuberculosis complex

This article presents a novel, qualitative approach for detecting airborne M. tuberculosis. Culturing or sample purification is not required. A DNA diagnostic method involving the polymerase chain reaction (PCR) coupled to an enzymatically generated color reaction was used for direct detection of M. bovis BCG (Bacillus of Calmette-Guérin), a surrogate for pathogenic M. tuberculosis. Fewer than 10 mycobacteria were detected with no culturing using this bioanalytical method. Analysis was completed in 1 to 1.5 days, in contrast to traditional culturing methods requiring a minimum of 2-3 weeks. To evaluate an air sampling method coupled to a PCR bioanalytical method, liquid cultures of the surrogate were aerosolized and collected for PCR analyses using 37-mm filter cassettes containing polytetrafluoroethylene filters. An Andersen six-stage (viable) particle sizing sampler was employed as a reference sampler. Aerosolized BCG impacted onto Andersen agar plates required incubation periods of 6-8 weeks before small colony forming units could be detected and enumerated. Although the BCG mean length of the rod-shaped particles was 8.3 microns, the airborne BCG particles were collected predominantly on the Andersen 4-6 stages, representing aerodynamic diameters 0.7 to 3.3 microns. Approximately 25 mycobacteria were detected without culturing using the PCR-filter cassette method. This approach could be used to detect airborne mycobacterial species of the M. tuberculosis complex and could permit the early detection of contaminated indoor air. Also, the efficacy of environmental controls could be evaluated and monitored. This approach could also be used to study the expulsion of infectious particles from patients and may permit risk assessment in regard to personal respiratory protection.

Evaluation of standard and modified sampling heads for the International PBI Surface Air System bioaerosol samplers

This study substituted sampling heads with smaller holes to collect small particles with the International PBI Surface Air System (SAS) battery-powered, bioaerosol air samplers, which have proved inefficient in collecting small airborne particles such as free bacteria (e.g., < 2 microns). An Andersen six-stage (6-STG) sampler was used simultaneously with two SAS samplers (SAS high flow [SAS-HF] and Compact SAS [SAS-C]) to sample indoor air in two office environments. Discrepancies were observed in the flow rate results obtained using the manufacturer's Pitot Validation Kit (PVK). Air sampling results suggested no significant difference in the concentration of bacteria and fungi collected among the four sampling heads using either sampler model in a small sample (n = 5) at either site. However, with an additional 15 samples at Site B (n = 5 + 15 = 20), three of the four sampling heads statistically undersampled the 6-STG and the other sampling head. The field data were variable (geometric standard deviation [GSD] = 1.25-1.94 for bacteria; GSD = 1.18-3.51 for fungi), but within ranges previously observed. The manufacturer increased particle collection efficiency by decreasing the hole size; however, this increase was only noticeable after many replicates. The PVK may be used as an accurate flow rate measurement device with the SAS-HF sampler, though the Pitot tube measures only centerline velocity pressure. Because of the 10% decrease in flow rate resulting from the pressure drop across the PVK, the equation in the manufacturer's literature for calculation of average velocities (VAVG) provides a reasonable estimate of flow rate through the SAS-C sampler.

Evaluation and control of worker exposure to fungi in a beet sugar refinery

A study of worker exposure to airborne fungi was undertaken in a sugar beet refinery to evaluate the level of exposure and to determine if controls could be implemented that would lower these exposures. A previous study at this refinery identified one worker who reacted on challenge testing to the moldy but not the fresh sugar beet pulp, had specific Immunoglobulin G to Aspergillus niger, and specific Immunoglobulin E to Aspergillus. Also, two employees were diagnosed with occupational asthma. In the study reported here, two field surveys were conducted, the first during the sugar production campaign (January) and the second during postproduction cleanup and maintenance (June). Approximately 65 personal and area air samples were collected on polycarbonate filters and the culturable fungal spores were identified and enumerated. This study showed high exposure of pellet loaders and pellet silo workers to various species of Aspergillus. Other fungal species that might pose a health hazard were detected. Exposures to fungi during the postproduction cleanup and maintenance phase were much higher than those measured during the production campaign. Engineering controls that would reduce employee exposure are discussed.

Evaluation of eight bioaerosol samplers challenged with aerosols of free bacteria

The need to quantify airborne microorganisms in the commercial microbiology industry (biotechnology) and during evaluations of indoor air quality, infectious disease outbreaks, and agriculture health investigations has shown there is a major technological void in bioaerosol sampling techniques to measure and identify viable and nonviable aerosols. As commercialization of microbiology increases and diversifies, it is increasingly necessary to assess occupational exposure to bioaerosols. Meaningful exposure estimates, by using area or environmental samplers, can only be ensured by the generation of data that are both precise and accurate. The Andersen six-stage viable (microbial) particle sizing sampler (6-STG) and the Ace Glass all-glass impinger-30 (AGI-30) have been suggested as the samplers of choice for the collection of viable microorganisms by the International Aerobiology Symposium and the American Conference of Governmental Industrial Hygienists. Some researchers consider these samplers inconvenient for evaluating industrial bioprocesses and indoor or outdoor environments. Alternative samplers for the collection of bioaerosols are available; however, limited information has been reported on their collection efficiencies. A study of the relative sampling efficiencies of eight bioaerosol samplers has been completed. Eight samplers were individually challenged with a bioaerosol, created with a Collison nebulizer, of either Bacillus subtilis or Escherichia coli. The samplers were evaluated under controlled conditions in a horizontal bioaerosol chamber. During each experimental run, simultaneous samples were collected with a reference AGI-30 to verify the concentration of microorganisms in the chamber from run to run and day to day.(ABSTRACT TRUNCATED AT 250 WORDS)

Phase I alternate-day dose study of chromomycin A3

Chromomycin A3 was given to 43 patients with metastatic cancer in order to determine the tolerable dose when the drug was administered on an every-other-day dose schedule for a total of five iv push injections, with the course of therapy being repeated every 4 weeks. At least three patients were entered at each dose level, graduated in 0.1-mg/m2 increments between 0.7 and 1.6 mg/m2. The most common (19 patients) side effect was nausea and/or vomiting, but this was usually mild, lasted for a few hours, and diminished in severity with repeated injections. Skin necrosis due to drug extravasation was a problem early in the study, but was eliminated by injecting the drug through iv tubing. Transient elevations in SGOT and alkaline phosphatase levels were observed, but proved not to be of serious consequence. Renal toxicity proved to be the limiting factor in therapy. However, a dose level of 1.3 mg/m2 was found to be a tolerable level of drug administration in previously untreated patients. Objective tumor responses were noted in four patients (Hodgkin's disease, embryonal rhabdomyosarcoma, adenocarcinoma of the lung, and malignant melanoma).