David S. Yassa

Characterization of an amino-terminal fragment of the bacteriophage T4 uvsY recombination protein

The uvsY protein plays essential roles in homologous genetic recombination processes in the bacteriophage T4. In vitro, uvsY promotes the formation of presynaptic filaments containing stoichiometric amounts of the T4 uvsX recombinase bound to single-stranded DNA. uvsY protein has intrinsic binding activities towards ssDNA, uvsX, and gp32, the T4-encoded SSB, however, it has not been directly determined which of these activities are essential for uvsYs role in presynapsis. We have therefore sought to generate altered forms of uvsY deficient in uvsX- and/or gp32-binding, in order to assess whether these specific protein-protein interactions are essential for uvsY recombination functions. Limited chymotrypsinolysis of the 16 kDa uvsY protein generates two major fragments: an 11.5 kDa fragment containing the N-terminus of uvsY, and a 4.5 kDa C-terminal fragment. We have expressed and purified the large fragment as a fusion protein containing the N-terminal 101 amino acids of uvsY. We show that this truncated uvsY species, which we call uvsYNT, retains ssDNA-binding activity, but is devoid of both uvsX- and gp32-binding activities. Like native uvsY, uvsYNT stimulates the ssDNA-dependent ATPase activity of the uvsX protein, however, the synergistic effects observed between uvsY, uvsX, and gp32 are not observed with uvsYNT. In addition, uvsYNT weakly stimulates uvsX-catalyzed DNA strand exchange reactions. The latter result is surprising since it suggests that specific interactions with uvsX and/or gp32 are not absolutely essential for uvsY recombination functions. Taken together, the data are consistent with a model in which uvsY-ssDNA interactions alone are capable of promoting the assembly of functional uvsX-ssDNA complexes, while uvsY-protein interactions stabilize uvsX-ssDNA complexes.

iAIDS: HIV-Related Internet Resources for the Practicing Clinician

In this review, we collate 25 clinically useful human immunodeficiency virus (HIV)-related Web sites to facilitate efficient access to online resources according to themes of clinical inquiry: (1) comprehensive clinical information, (2) opportunistic infections, (3) antiretroviral drug interactions, (4) care of HIV-infected women and children, and (5) continuing medical education. We evaluated these Web sites for clinical content and quality using criteria including the currency of information, inclusion of references, sponsors, whether the site is useful in resource-limited settings, ease of navigation, and content specific for each theme. Using the specified criteria, we provided overall ratings for each Web site. We conclude that the Web sites listed in this review can help extend knowledge about best practices and provide real-time patient care support to clinicians.

Risk Factors for Staphylococcus aureus Postpartum Breast Abscess

BACKGROUND Staphylococcus aureus (SA) breast abscesses are a complication of the postpartum period. Risk factors for postpartum SA breast abscesses are poorly defined, and literature is conflicting. Whether risk factors for methicillin-resistant SA (MRSA) and methicillin-susceptible SA (MSSA) infections differ is unknown. We describe novel risk factors associated with postpartum breast abscesses and the changing epidemiology of this infection. METHODS We conducted a cohort study with a nested case-control study (n = 216) involving all patients with culture-confirmed SA breast abscess among >30 000 deliveries at our academic tertiary care center from 2003 through 2010. Data were collected from hospital databases and through abstraction from medical records. All SA cases were compared with both nested controls and full cohort controls. A subanalysis was completed to determine whether risk factors for MSSA and MRSA breast abscess differ. Univariate analysis was completed using Students t test, Wilcoxon rank-sum test, and analysis of variance, as appropriate. A multivariable stepwise logistic regression was used to determine final adjusted results for both the case-control and the cohort analyses. RESULTS Fifty-four cases of culture-confirmed abscess were identified: 30 MRSA and 24 MSSA. Risk factors for postpartum SA breast abscess in multivariable analysis include in-hospital identification of a mother having difficulty breastfeeding (odds ratio, 5.00) and being a mother employed outside the home (odds ratio, 2.74). Risk factors did not differ between patients who developed MRSA and MSSA infections. CONCLUSIONS MRSA is an increasingly important pathogen in postpartum women; risk factors for postpartum SA breast abscess have not changed with the advent of community-associated MRSA.

Randomized Comparison of 3 High-Level Disinfection and Sterilization Procedures for Duodenoscopes

BACKGROUND AND AIMS Duodenoscopes have been implicated in the transmission of multidrug-resistant organisms (MDRO). We compared the frequency of duodenoscope contamination with MDRO or any other bacteria after disinfection or sterilization by 3 different methods. METHODS We performed a single-center prospective randomized study in which duodenoscopes were randomly reprocessed by standard high-level disinfection (sHLD), double high-level disinfection (dHLD), or standard high-level disinfection followed by ethylene oxide gas sterilization (HLD/ETO). Samples were collected from the elevator mechanism and working channel of each duodenoscope and cultured before use. The primary outcome was the proportion of duodenoscopes with an elevator mechanism or working channel culture showing 1 or more MDRO; secondary outcomes included the frequency of duodenoscope contamination with more than 0 and 10 or more colony-forming units (CFU) of aerobic bacterial growth on either sampling location. RESULTS After 3 months of enrollment, the study was closed because of the futility; we did not observe sufficient events to evaluate the primary outcome. Among 541 duodenoscope culture events, 516 were included in the final analysis. No duodenoscope culture in any group was positive for MDRO. Bacterial growth of more than 0 CFU was noted in 16.1% duodenoscopes in the sHLD group, 16.0% in the dHLD group, and 22.5% in the HLD/ETO group (P = .21). Bacterial growth or 10 or more CFU was noted in 2.3% of duodenoscopes in the sHLD group, 4.1% in the dHLD group, and 4.2% in the HLD/ETO group (P = .36). MRDOs were cultured from 3.2% of pre-procedure rectal swabs and 2.5% of duodenal aspirates. CONCLUSIONS In a comparison of duodenoscopes reprocessed by sHLD, dHLD, or HLD/ETO, we found no significant differences between groups for MDRO or bacteria contamination. Enhanced disinfection methods (dHLD or HLD/ETO) did not provide additional protection against contamination. However, insufficient events occurred to assess our primary study end-point. ClinicalTrials.gov no: NCT02611648.

An unusual pathogen for prosthetic joint infection

In 2012, an 84-year-old Chinese man presented with progressive, chronic left atraumatic knee pain and swelling. His medical history was notable for pulmonary tuberculosis treated in China in 1951 and rheumatoid arthritis diagnosed in 2006. His joint pain progressed despite use of disease modifying drugs and steroid injections. Antitumor necrosis factor inhibitors were not used because of concerns of tuberculosis reactivation. Clinical examination showed he had antalgic gait, knee eff usion, stiff ness, and joint-line tenderness. Laboratory results included erythrocyte sedimentation rate of 88 mm/h and C-reactive protein of 205 mg/L. Radiographs showed severe tri-compartmental degenerative arthritis (fi gure A). The patient underwent total knee arthroplasty in August, 2012 (fi gure B). Extensive synovitis was noted and pathological examination showed granulomatous infl ammation (fi gure C). Staining of synovial tissue for acid-fast bacilli and tuberculosis PCR were negative. The patient’s knee symptoms initially improved, but 5 months after total knee arthroplasty he developed a draining sinus from the knee incision. He underwent irrigation and debridement of the knee with exchange of the polyethylene tibial insert. Initial synovial tissue fl uid cultures were negative, but subsequent acid-fast bacilli cultures from synovial tissue and joint fl uid grew Mycobacterium tuberculosis. Sputum cultures were negative for pulmonary tuberculosis. He started a course of antituberculosis therapy including rifampicin, isoniazid, pyrazinamide, and ethambutol for treatment of tuberculosis prosthetic joint infection in February, 2013. He was advised to undergo a two-stage resection-revision arthroplasty but declined further surgery and thus an implant retention strategy was pursued. The patient completed 12 months of antituberculosis therapy in February, 2014. He has since continued rifampicin and isoniazid treatment with a plan for long-term suppressive therapy in the setting of retained prosthesis. At his latest follow-up, 2 years after initial diagnosis of tuberculous prosthetic joint infection, the incision had healed without clinical sign of infection and his knee has a pain-free range of motion from 0–95°. Tuberculous arthritis accounts for 1–5% of people with tuberculosis. Scarce data are available for optimum management of tuberculous prosthetic joint infection. This case illustrates an unusual reactivation of tuberculosis in an isolated extra-pulmonary site after joint replacement surgery. Prompt initiation of antituberculosis therapy might enable implant retention, although continuation of suppressive therapy might be needed. In the setting of globalisation and the increasing use of immunomodulatory therapies and joint replacement surgeries, this case illustrates the need for tuberculosis to be thought about early in the diff erential diagnosis for culture-negative prosthetic joint infection in patients with previous exposures or epidemiological risk factors.

Re-Treatment With Ethambutol After Toxic Optic Neuropathy.

There are no data in the literature regarding the safety of re-treatment with ethambutol for recurrent mycobacterial infection after prior ethambutol-induced optic neuropathy. We describe a patient who developed optic neuropathy attributed to ethambutol, recovered fully after drug withdrawal, and tolerated a 14-month long re-treatment 10 years later without developing recurrent optic neuropathy.

Periprocedural Antibiotic Prophylaxis for Cardiac Implantable Electrical Device Procedures: Results From a Heart Rhythm Society Survey

Cardiac implantable electrical device (CIED) infections are morbid and costly, with incidence estimates ranging up to 2.0% to 3.0% or more [(1,2)][1]. Use of perioperative antibiotics is the standard of care for CIED implantation [(3)][2], but there are no high-quality data supporting antibiotic

Standard work for room entry: Linking lean, hand hygiene, and patient-centeredness.

BACKGROUND Healthcare-associated infections are costly and fatal. Substantial front-line, administrative, regulatory, and research efforts have focused on improving hand hygiene. PROBLEM While broad agreement exists that hand hygiene is the most important single approach to infection prevention, compliance with hand hygiene is typically only about 40%(1). GOALS Our aim was to develop a standard process for room entry in the intensive care unit that improved compliance with hand hygiene and allowed for maximum efficiency. STRATEGY We recognized that hand hygiene is a single step in a substantially more complicated process of room entry. We applied Lean engineering techniques to develop a standard process that included both physical steps and also standard communication elements from provider to patients and families and created a physical environment to support this. RESULTS We observed meaningful improvement in the performance of the new standard as well as time savings for clinical providers with each room entry. We also observed an increase in room entries that included verbal communication and an explanation of what the clinician was entering the room to do. IMPLICATIONS The design and implementation of a standardized room entry process and the creation of an environment that supports that new process has resulted in measurable positive outcomes on the medical intensive care unit, including quality, patient experience, efficiency, and staff satisfaction. Designing a process, rather than viewing tasks that need to happen in close proximity in time (either serially or in parallel) as unrelated, simplifies work for staff and results in higher compliance to individual tasks.

Correlation of Hand Hygiene Compliance Measured by Direct Observation with Estimates Obtained from Product Usage

Improving compliance with hand hygiene is a cornerstone of infection prevention. However, data regarding practical methods for monitoring compliance are limited. We found that product use metrics have a moderate correlation with direct observation in ward settings and limited correlation in intensive care units.Infect Control Hosp Epidemiol 2018;39:746-749.

Investigation of a Candida guilliermondii Pseudo-outbreak Reveals a Novel Source of Laboratory Contamination

ABSTRACT Candida guilliermondii was isolated from sterile specimens with increasing frequency over a several-month period despite a paucity of clinical evidence suggesting true Candida infections. However, a health care-associated outbreak was strongly considered due to growth patterns in the microbiology laboratory that were more consistent with true infection than environmental contamination. Therefore, an extensive investigation was performed to identify its cause. With the exception of one case, patient clinical courses were not consistent with true invasive fungal infections. Furthermore, no epidemiologic link between patients was identified. Rather, extensive environmental sampling revealed C. guilliermondii in an anaerobic holding jar in the clinical microbiology laboratory, where anaerobic plates were prereduced and held before inoculating specimens. C. guilliermondii grows poorly under anaerobic conditions. Thus, we postulate that anaerobic plates became intermittently contaminated. Passaging from intermittently contaminated anaerobic plates to primary quadrants of aerobic media during specimen planting yielded a colonial growth pattern typical for true specimen infection, thus obscuring laboratory contamination. A molecular evaluation of the C. guilliermondii isolates confirmed a common source for pseudo-outbreak cases but not for the one true infection. In line with Reasons model of organizational accidents, active and latent errors coincided to contribute to the pseudo-outbreak. These included organism factors (lack of growth in anaerobic conditions obscuring plate contamination), human factors (lack of strict adherence to plating order, leading to only intermittent observation of aerobic plate positivity), and laboratory factors (novel equipment). All of these variables should be considered when evaluating possible laboratory-based pseudo-outbreaks.