A Baker's Dozen of Top Antimicrobial Stewardship Intervention Publications in 2022

Keeping abreast of the antimicrobial stewardship-related articles published each year is challenging. The Southeastern Research Group Endeavor identified antimicrobial stewardship-related, peer-reviewed literature that detailed an actionable intervention during 2022. The top 13 publications were selected using a modified Delphi technique. These manuscripts were reviewed to highlight actionable interventions used by antimicrobial stewardship programs to capture potentially effective strategies for local implementation.

Epidemiology and treatment of invasive Bartonella spp. infections in the United States

OBJECTIVES

Bartonella spp., renowned for cat-scratch disease, has limited reports of dissemination. Tissue and blood cultures have limitations in detecting this fastidious pathogen. Molecular testing (polymerase chain reaction, PCR) and cell-free DNA have provided an avenue for diagnoses. This retrospective observational multicenter study describes the incidence of disseminated Bartonella spp. and treatment-related outcomes.

METHODS

Inclusion criteria were diagnosis of bartonellosis via diagnosis code, serology testing of blood, polymerase chain reaction (PCR) of blood, 16/18S tests of blood or tissue, cultures of blood or tissue, or cell-free DNA of blood or tissue from January 1, 2014, through September 1, 2021. Exclusions were patients who did not receive treatment, insufficient data on treatment course, absence of dissemination, or retinitis as dissemination.

RESULTS

Patients were primarily male (n = 25, 61.0%), white (n = 28, 68.3%), with mean age of 50 years (SD 14.4), and mean Charlson comorbidity index of 3.5 (SD 2.1). Diagnosis was primarily by serology (n = 34, 82.9%), with Bartonella henselae (n = 40, 97.6%) as the causative pathogen. Treatment was principally doxycycline with rifampin (n = 17, 41.5%). Treatment failure occurred in 16 (39.0%) patients, due to escalation of therapy during treatment (n = 5, 31.3%) or discontinuation of therapy due to an adverse event or tolerability (n = 5, 31.3%).

CONCLUSIONS

In conclusion, this is the largest United States-based cohort of disseminated Bartonella spp. infections to date with a reported 39% treatment failure. This adds to literature supporting obtaining multiple diagnostic tests when Bartonella is suspected and describes treatment options.

Mediating pathways that link adverse childhood experiences with cardiovascular disease

OBJECTIVES

There is uncertainty about which factors mediate the association between adverse childhood experiences (ACEs) and cardiovascular disease (CVD). This could inform secondary prevention targets.

STUDY DESIGN

Mediation analysis of a prospective cohort study.

METHODS

English Longitudinal Study of Ageing (ELSA) wave 3 data (2006/7) were used to measure retrospective exposure to 12 individual ACEs and waves 2 to 4 (2004/5 to 2008/9) data to measure current exposure to potential mediators [smoking, physical activity, alcohol consumption, body mass index, depression, and C-reactive protein (CRP)]. Waves 4 to 9 ELSA data (2008/9 to 2018/19) were used to measure incident CVD. Cumulative ACE exposure was categorised into experiencing 0, 1 to 3, or ≥4 individual ACEs. Associations were tested between ACE categories, potential mediators, and incident CVD, to inform which variables were analysed in causal mediation models.

RESULTS

The analytical cohort consisted of 4547 participants (56% women), with a mean age of 64 years (standard deviation = 9 years). At least one ACE had been experienced by 45% of the cohort, and 24% developed incident CVD over a median follow-up period of 9.7 years (interquartile range: 5.3-11.4 years). After adjusting for potential confounders, experiencing ≥4 ACEs compared with none was associated with incident CVD [odds ratio (OR): 1.55; 95% confidence interval (CI): 1.10, 2.17], and the association of one to three ACEs compared with none was non-significant (OR: 1.08; 95% CI: 0.93, 1.24). There were two statistically significant mediators of the association between ≥4 ACEs and incident CVD: CRP and depression, which accounted for 10.7% and 10.8% of the association, respectively.

CONCLUSIONS

Inflammation and depression partially mediated the association between ACEs and CVD. Targeting these factors may reduce the future incidence of CVD.

Trimethoprim/Sulfamethoxazole vs Minocycline for the Treatment of Nonurinary Monomicrobial Stenotrophomonas maltophilia Infections in Hospitalized Patients

BACKGROUND

Stenotrophomonas maltophilia is an opportunistic, gram-negative bacillus with few therapeutic options due to a high level of intrinsic resistance. Trimethoprim/sulfamethoxazole (SXT) is recommended as the first-line treatment; however, minocycline (MIN) has been shown to have similar clinical outcomes in treating S. maltophilia and addresses concern for increasing resistance to SXT.

OBJECTIVE

The objective of this study is to evaluate the efficacy and safety outcomes of nonurinary, monomicrobial infections due to S. maltophilia in hospitalized patients treated with MIN or SXT.

METHODS

This was a retrospective study of hospitalized adult patients receiving MIN or SXT for nonurinary monomicrobial S. maltophilia infection from April 1, 2018 to March 31, 2020. The primary outcome was clinical disposition classified as rates of clinical failure, clinical improvement, or clinical success.

RESULTS

Eighty-two patients (88.2%) received MIN and 11 patients (11.8%) received SXT initially. Clinical failure occurred in 16 (19.5%) patients in the MIN group and in 4 (36.4%) patients in the SXT group (P = 0.242). Clinical improvement occurred in 11 (13.4%) patients in the MIN group and in 1 (9.1%) patient in the SXT group (P = 1.0). Clinical success occurred in 55 (67.1%) patients in the MIN group and in 6 (54.5%) patients in the SXT group (P = 0.503). Total duration of antimicrobial therapy (P = 0.3198), in-hospital mortality (P = 1.0), hospital length of stay (P = 0.9668), intensive care unit (ICU) length of stay (P = 0.1384), and 30-day readmission (P = 0.686) were similar between groups.

CONCLUSIONS AND RELEVANCE

Rates of clinical failure, clinical improvement, or clinical success were similar between MIN and SXT for nonurinary monomicrobial S. maltophilia infections.

925. Remdesperate for Stewardship: Impact of a Remdesivir Stewardship Strategy on the Care of Patients with COVID-19 Admitted to a Community Teaching Hospital

Background

The use of remdesivir (RDV) in patients hospitalized with COVID-19 has resulted in a significantly shorter time to recovery, especially in patients receiving low flow oxygen. Despite the shortened time to recovery, concerns have been raised regarding the $3,120 cost of a five-day course. This price was originally justified by the suggestion that RDV would save hospitals approximately $12,000 per patient by shortening hospital length of stay (LOS) by four days, however, this has not been consistently demonstrated in clinical practice. A preliminary review of RDV orders at our facility revealed hospital discharges were being delayed to complete a five-day course of treatment in patients otherwise medically ready to discharge.

Methods

This single-center, retrospective, comparative study was conducted at AdventHealth Orlando, a 1,368-bed community teaching hospital in central Florida. In January 2021, the campus stewardship committee devised a RDV stewardship strategy including targeted education and escalation of orders not meeting institutional criteria at time of order verification. This study compared pre-intervention patients who received RDV from December 1, 2020, to January 7, 2021, to post-intervention patients who received RDV from January 8, 2021, to February 28, 2022. The primary objective of this study was to assess the impact of a pharmacist-driven RDV stewardship initiative on the duration of therapy in hospitalized patients with COVID-19.

Results

A total of 2104 remdesivir orders were included in the study (209 pre-intervention and 1895 post-intervention). Overall, patients had a median age of 59 years and 49% were male. Majority of patients in both groups required low flow supplemental oxygen at the time of RDV initiation. Significantly more orders in the intervention group aligned with institutional criteria at the time of order entry (47% vs 84%, p< .001). Patients completing the full 5-day course of remdesivir therapy decreased from 79 to 53% (p< .001). A decreased duration of therapy and length of stay were observed in the intervention group.

Conclusion

Pharmacist-driven RDV stewardship increased adherence to the institutional algorithm and reduced duration of therapy.

Disclosures

Amy L. Carr, PharmD, BCIDP, Shionogi: Advisory Board.

667. Real-world Experience of Cefiderocol with Pseudomonas aeruginosa in the PROVE (Retrospective Cefiderocol Chart Review) Study

Background

Gram-negative (GN) bacterial resistance is an urgent global health problem. Cefiderocol (CFDC) is active against many resistant GN pathogens, including Pseudomonas aeruginosa (PA). PROVE is an ongoing international, retrospective study assessment of CFDC use for Gram-negative infections (GNI).

Methods

Patients were eligible if they received ≥ 72 hours of CFDC. Patient and pathogen characteristics, hospital course, and antibiotic treatment patterns were described. All-cause mortality (ACM) at 14 and 30 days and clinical cure were examined as outcomes, overall, and by key characteristics such as pathogen susceptibility (determined at the local level), patient demographics, infection site, and severity of illness. Serious adverse drug reactions (SADR) were recorded.

Results

To date, 123 patients treated with CFDC at 12 sites were included. Sixty-five patients had PA as a pathogen, either alone (N=45) or in combination with another pathogen (N=20) attributed to starting CFDC. The median age was 54 years; 68% were male. The most prevalent comorbidity was diabetes with end stage organ damage (N=15, 23%). CFDC was given in an ICU setting in 54 (82%) patients. Vasopressors and mechanical ventilation were required in 42% and 62%, respectively. Most (91%) PA were carbapenem resistant. The median time from a positive culture to start of CFDC was 6 days. CFDC monotherapy was used in 75%. The most common GN antibiotic class used concurrently with CFDC was aminoglycosides (N=7). Targeted therapy with CFDC against pathogens of known susceptibility with or without prior GN antibiotics accounted for 80% of use. The remainder was used for salvage (15%) or empirically (2%). Susceptibility testing to CFDC, available for 54 cultures (54 patients), showed 94% (51/54) were susceptible. Post-CFDC initiation 14- and 30-day all-cause mortality (ACM) was 9% (95% CI: 3%-19%) and 23% (95% CI: 14%-35%) respectively. Clinical resolution was achieved in 66% (95% CI: 53% -77%). Thirty-day ACM for susceptible pathogens was 25% (13/51).

Cefiderocol Use Patterns in Pseudomonas aeruginosa

Conclusion

Real-world use of CFDC for PA demonstrated that most patients had multiple comorbidities and were severely ill. These data suggest that CFDC is being used appropriately with little empirical use in patients with few treatment options.

Disclosures

Stephen Marcella, MD, MPH, Shionogi: Shionogi employee|Shionogi, Inc: Employee Amy L. Carr, PharmD, BCIDP, Shionogi: Advisory Board Sean Nguyen, n/a, Shionogi: Employee Anan Zhou, MPH, Shionogi, Inc: contracting work for Shionogi, Inc.

181. Impact of Rapid Diagnostic Technology on Patients with Candidemia

Background

Candida spp. are the fourth most common cause of bloodstream infections (BSI) in the United States and have an associated mortality rate of 19-40.5%. Mortality rates are further impacted by delay in time to adequate antifungal therapy, historically due to delayed time to identification on culture. The utilization of rapid diagnostic technology (RDT) has been effective in timely identification of bacterial pathogens causing BSI, but RDT for fungal organisms has demonstrated mixed results. At AdventHealth Central Florida Division South (CFD-S), pharmacists provide 24-hour coverage for real-time notification of all positive blood culture results. The objective of this study was to evaluate the clinical impact of the GenMark ePlex Blood Culture Identification Panels (BCID) fungal pathogen (FP) panel paired with 24/7, pharmacist-driven response in patients with candidemia. 

Methods

This multi-site, pre/post, retrospective chart review included adult patients admitted to CFD-S with at least one positive blood culture with Candida spp. from June 2019 through May 2020 (pre-RDT), and August 2020 through July 2021 (post-RDT). Patients receiving systemic antifungal prophylaxis, with known candidiasis at time of index RDT result, or who discharged prior to culture positivity were excluded. The primary outcome was time to effective antifungal therapy in patients with candidemia.

Results

A total of 200 patients were included in the study (100 pre-RDT and 100 post-RDT). Overall, patients had a median age of 61 years and 50% were male. Patient characteristics are summarized in Table 1; median APACHEII score differed by three points (13.5 vs. 16.5). Time to effective therapy was similar between groups (39.8 vs. 38.5 hours, p=0.217). There was no difference in secondary outcomes (Table 2) other than ICU length of stay (2.5 vs. 6.0 days, p=0.033) and all-cause in-hospital mortality (15% vs. 30%, p=0.011).

Conclusion

Pharmacist-driven, real-time response to RDT did not significantly impact time to effective antifungal therapy in patients with candidemia. Higher rate of in-hospital mortality was likely a reflection of increased severity of illness in the post-RDT group.

Disclosures

Amy L. Carr, PharmD, BCIDP, Shionogi: Advisory Board.

1005. Financial and clinical impact of ceftolozane/tazobactam global recall on the treatment of multi-drug resistant Pseudomonas in a large health system

Background

In December 2020, ceftolozane/tazobactam (CT) was voluntarily recalled due to failed sterility tests. With this recall, clinicians were forced to utilize alternatives for multi-drug resistant (MDR) Pseudomonas (PSA) infections until CT returned in late December, 2021. While many studies have examined the impact of medication shortages, few have evaluated the impact of antimicrobial shortages. We evaluated the impact of the CT recall by assessing cost, clinical outcomes, and utilization of novel alternative agents.

Methods

This multi-site retrospective cohort study compared patients treated for MDR PSA prior to the CT recall (Jan-Jul 2020) to patients treated during the CT recall (Jan-Jul 2021) across seven AdventHealth Central Florida (AHCF) adult hospitals. The primary outcome was percentage of patients treated with novel therapies (CT, ceftazidime/avibactam, or cefiderocol). Secondary outcomes included length of therapy (LOT), inpatient mortality, 30-day readmissions, length of say (LOS), pharmacy expenditures, and average cost per case.

Results

A total of 203 patients with MDR PSA were evaluated: 100 in the pre-recall cohort and 103 in the post-recall cohort. The majority (58%) of patients were male with an average age of 64 years. The most common source of infection in both cohorts was pneumonia, followed by complicated urinary tract infection. Significantly more patients were treated with novel agents as definitive therapy in the post-recall cohort (65% vs. 29%, p< 0.0001). Average LOT for all anti-PSA therapy was 12 days in the pre-recall cohort compared to 14 days in the post-recall cohort (p=0.1753). Inpatient mortality and 30-day readmissions were not statistically different between groups. Hospital LOS was significantly different between the two groups (18 days vs. 25 days, p=0.006). Significantly higher pharmacy expenditures were found in the post recall cohort (Figure 1) and the average cost per case was significantly higher in the post-recall cohort ($125,254 vs. $62,249). Figure 1:Pharmacy Expenditures for Novel Agents

Novel agents: cefiderocol, ceftazidime/avibactam, ceftolozane/tazobactam

Conclusion

The CT recall had a significant impact on both economic and clinical outcomes, particularly increased length of stay, length of therapy, and cost to both the patient and health system. Higher utilization of novel agents is concerning given rising rates of PSA resistance.

Disclosures

Amy L. Carr, PharmD, BCIDP, Shionogi: Advisory Board.

666. Outcomes Using Cefiderocol for the Treatment of Acinetobacter baumannii Infections from the PROVE (Real-World Evidence) Study

Background

PROVE is an ongoing international, retrospective study assessing cefiderocol (CFDC) for Gram-negative (GN) infections. Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are difficult-to-treat with limited treatment options. CFDC is a novel sidero cephalosporin with activity against CRAB. This analysis describes the outcomes and treatment patterns of CFDC treatment in CRAB infections from this study.

Methods

Patients were eligible if they received ≥ 72 hours of CFDC. Key patient characteristics, infecting pathogen susceptibility, illness severity, and treatment patterns were assessed. Fourteen and 30-day all-cause mortality (ACM) and clinical cure were examined as outcomes. Susceptibility testing was performed locally. Serious adverse drug reactions (SADR) were recorded.

Results

To date,123 patients treated with CFDC at 12 sites were included. Forty-one had monomicrobial (n=29) or polymicrobial (n=12) Acinetobacter baumannii (AB) infection. All but one were CRAB. The median age was 53 years; 71% were male. The most prevalent comorbidity was severe burns (N=9, 22%). Sixty-one percent of patients received CFDC in the ICU, 51% required mechanical ventilation, and 34% required vasopressor support. The median time from positive culture to CFDC initiation was 5 days. CFDC monotherapy was used in 61%. Tetracyclines were the most common concurrent GN antibiotics used with CFDC (N = 8, 19.5%). Targeted therapy with or without prior GN antibiotics was used in 76%, salvage in 20%, and empirical in 2%. Susceptibility results were available for 28 AB cultures from 28 patients of which 82% were susceptible to CFDC. Post-CFDC 14- and 30-day ACM was 12% (95% CI: 4%-26%) and 22% (95% CI: 11%-38%), respectively. Clinical resolution was achieved in 59% (95% CI: 42% -74%). Thirty-day ACM varied by susceptibility to CFDC: 26% for susceptible, 40% for resistant. One SADR (interstitial nephritis) was reported.

Cefiderocol Use Patterns in Acinetobacter baumannii

Conclusion

Real-world use of CFDC for AB demonstrates that most patients were complex with multiple comorbidities and severe illness prior to treatment. It was used mostly as targeted therapy. CFDC may be a treatment option in these difficult-to-treat infections.

Disclosures

Stephen Marcella, MD, MPH, Shionogi: Shionogi employee|Shionogi, Inc: Employee Amy L. Carr, PharmD, BCIDP, Shionogi: Advisory Board Benjamin Georgiades, PharmD, Shionogi, Inc: Employee Caroline Margiotta, MA, Shionogi, Inc: contracting work for Shionogi, Inc.

919. Let’s GO PO: Impact of Monthly Feedback on a Longitudinal Intravenous to Oral Antimicrobial Conversion Initiative

Background

Timely conversion of antimicrobials from intravenous (IV) to oral (PO) route has been shown to decrease costs and length of stay (LOS) without compromising safety and efficacy of therapy. Use of oral antimicrobials may additionally prevent complications related to IV catheters, such as infection, emboli, and patient discomfort. An approved IV to PO policy allowed pharmacists to convert orders for fourteen included antimicrobials and eligible patients at time of order verification.

Methods

This single-center, retrospective, comparative study was conducted at AdventHealth Orlando, a 1,368-bed community teaching hospital in central Florida. In November 2020, six clinical pharmacist teams began receiving monthly feedback on IV to PO conversion rates in the form of a RePOrt Card, containing IV to PO conversion rates compared to other clinical teams, individual antimicrobial conversion rates, and comparison to prior team progress (Figure 1). RePOrt Cards were provided through October 2021. This study compared pre-intervention days of therapy (DOTs) of antimicrobials from November 2019-October 2020 to post-intervention DOTs from November 2020 to March 2022. The primary objective of this study was to assess the impact of monthly, team-based feedback on percentage of antimicrobials administered orally during a pharmacist-driven IV to PO stewardship initiative. Figure 1

Pharmacist-Driven Methicillin-Resistant S. aureus Polymerase Chain Reaction Testing for Pneumonia

BACKGROUND

Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) can be detected using nasal swab polymerase chain reaction (PCR) assay and is associated with clinical MRSA infection. The MRSA nasal PCR has a rapid turnaround time and a negative predictive value for MRSA pneumonia of >98%; however, data are limited in critically ill patients.

OBJECTIVE

The purpose of this study is to determine the impact of a pharmacist-driven algorithm, utilizing MRSA PCR nasal screening on duration of anti-MRSA therapy in patients admitted to the intensive care unit (ICU) with suspected pneumonia.

METHODS

A single-center pre/post study was conducted in 4 ICUs at a large tertiary care community hospital. Adult patients admitted to the ICU initiated on vancomycin or linezolid for pneumonia managed using a pharmacist-driven MRSA PCR algorithm were included in the algorithm cohort. A historical cohort with standard management was matched 1:1 by age, type of pneumonia, and Acute Physiology and Chronic Health Evaluation II (APACHE II) score. The primary outcome was duration of anti-MRSA therapy. Secondary outcomes included MRSA rates, number of vancomycin levels, new onset of acute kidney injury (AKI), ICU length of stay (LOS), hospital LOS, and mortality.

RESULTS

Of the 245 patients screened, 50 patients met inclusion criteria for the algorithm cohort and were matched to 50 patients in the historical cohort. The duration of anti-MRSA therapy was significantly lower compared with the historical cohort (47 vs 95 hours; P < 0.001). Secondary outcomes were similar between groups for MRSA rates, new onset of AKI, LOS, and mortality. There were less vancomycin levels ordered in the algorithm cohort (2 vs 3, P = 0.026).

CONCLUSIONS

A pharmacist-driven MRSA PCR algorithm significantly reduced anti-MRSA duration of therapy in critically ill patients with pneumonia. Future studies should validate these results in critically ill populations and in settings where MRSA pneumonia is more prevalent.

Renin Angiotensin Aldosterone System Antagonism in 2019 Novel Coronavirus Acute Lung Injury

It has been established that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses angiotensin-converting enzyme 2 (ACE2), a membrane-bound regulatory peptide, for host cell entry. Renin-angiotensin-aldosterone system (RAAS) inhibitors have been reported to increase ACE2 in type 2 pneumocyte pulmonary tissue. Controversy exists for the continuation of ACE inhibitors, angiotensin II receptor blockers, and mineralocorticoid receptor antagonists in the current pandemic. ACE2 serves as a regulatory enzyme in maintaining homeostasis between proinflammatory angiotensin II and anti-inflammatory angiotensin 1,7 peptides. Derangements in these peptides are associated with cardiovascular disease and are implicated in the progression of acute respiratory distress syndrome. Augmentation of the ACE2/Ang 1,7 axis represents a critical target in the supportive management of coronavirus disease 2019–associated lung disease. Observational data describing the use of RAAS inhibitors in the setting of SARS-CoV-2 have not borne signals of harm to date. However, equipoise persists, requiring an analysis of novel agents including recombinant human-ACE2 and existing RAAS inhibitors while balancing ongoing controversies associated with increased coronavirus infectivity and virulence.

Cefiderocol for the Treatment of Adult and Pediatric Patients With Cystic Fibrosis and Achromobacter xylosoxidans Infections

Treatment options for Achromobacter xylosoxidans are limited. Eight cystic fibrosis patients with A. xylosoxidans were treated with 12 cefiderocol courses. Pretreatment in vitro resistance was seen in 3 of 8 cases. Clinical response occurred after 11 of 12 treatment courses. However, microbiologic relapse was observed after 11 of 12 treatment courses, notably without emergence of resistance.

Clinical Utility of Methicillin-Resistant Staphylococcus aureus Nasal Screening for Antimicrobial Stewardship: A Review of Current Literature

Significant clinical and financial consequences are associated with both inadequate and unnecessary exposure to broad-spectrum antibiotics. As such, antimicrobial stewardship programs seek objective, reliable, and cost-effective tests to identify patients at highest or lowest risk for drug-resistant organisms to guide empirical antimicrobial selection. Use of methicillin-resistant Staphylococcus aureus (MRSA) nasal screening to rule out MRSA in lower respiratory tract infections has led to significant reductions in duration of vancomycin therapy. The clinical utility of MRSA nasal screening in other types of infection remains less clear. This review describes the performance of MRSA nasal screening in predicting MRSA infection, highlights practical considerations for use of MRSA nasal screening, and provides guidance for incorporating MRSA nasal screening into clinical practice. With a high negative predictive value when the prevalence of MRSA is low, MRSA nasal screening is a valuable antimicrobial stewardship tool with potential applications beyond lower respiratory tract infections. In appropriately selected patients, negative MRSA nasal screening can prevent initiation or guide discontinuation of anti-MRSA therapy. Antimicrobial stewardship programs should develop institutional guidelines to promote proper use of MRSA nasal screening. Pharmacists are well positioned to assist with education, interpretation, and application of MRSA nasal screening results.

Responses of Amblyomma americanum and Dermacentor variabilis to odorants that attract haematophagous insects

Carbon dioxide (CO(2) ), 1-octen-3-ol, acetone, ammonium hydroxide, L-lactic-acid, dimethyl trisulphide and isobutyric acid were tested as attractants for two tick species, Amblyomma americanum and Dermacentor variabilis (Acari: Ixodidae), in dose-response bioassays using Y-tube olfactometers. Only CO(2) , acetone, 1-octen-3-ol and ammonium hydroxide elicited significant preferences from adult A. americanum, and only CO(2) was attractive to adult D. variabilis. Acetone, 1-octen-3-ol and ammonium hydroxide were separately evaluated at three doses against CO(2) (from dry ice) at a field site supporting a natural population of A. americanum nymphs and adults. Carbon dioxide consistently attracted the highest number of host-seeking ticks. However, for the first time, acetone, 1-octen-3-ol and ammonium hydroxide were shown to attract high numbers of A. americanum. Further research is needed to determine the utility of these semiochemicals as attractants in tick surveillance and area-wide management programmes.

Localization of ISG15 and conjugated proteins in bovine endometrium using immunohistochemistry and electron microscopy

The interferon-stimulated gene ISG15, a ubiquitin homolog, becomes conjugated to and regulates uterine proteins in response to conceptus-derived interferon-tau on d 18 of pregnancy. It was hypothesized here that cellular localization of ISG15 within endometrial cells might provide insight regarding function. Uteri were collected from cows (approximately 21-d estrous cycle) on d 17-21/0 of the estrous cycle and pregnancy and d 23, 45, and 50 of pregnancy. Intracellular ISG15 and its conjugates were present on d 17 of pregnancy, peaked to highest levels from d 18 to 23 and then declined to low but detectable levels by d 45 (P < 0.05) based on Western blotting. ISG15 and its conjugates were not detected on d 50 of pregnancy or during the estrous cycle. Immunohistochemistry revealed that ISG15 was localized throughout the endometrium on d 18-23, with heaviest staining in the sublumenal stratum compactum and the glandular epithelium throughout the stratum spongiosum. By d 45 and 50, ISG15 was lightly stained only in the stratum compactum immediately beneath the lumenal epithelium. Using transmission electron microscopy and immunogold labeling, ISG15 was specifically localized to organelles and compartments of endometrial epithelial cells and stromal cells: nucleus, perinuclear space, cytosol, mitochondria, rough endoplasmic reticulum, and cell membrane. This specific localization in epithelial and stromal cells led to the conclusion that ISG15 has diverse intracellular functions. The sustained presence of conjugated ISG15 through d 50 of pregnancy might reflect stabilization of conjugated proteins in response to implantation and the development of the placenta.