White Paper: Developing Antimicrobial Drugs for Resistant Pathogens, Narrow-Spectrum Indications, and Unmet Needs.

Despite progress in antimicrobial drug development, a critical need persists for new, feasible pathways to develop antibacterial agents to treat people infected with drug-resistant bacteria. Infections due to resistant gram-negative bacilli continue to cause unacceptable morbidity and mortality rates. Antibacterial agents have been historically studied in noninferiority clinical trials that focus on a single site of infection (eg, complicated urinary tract infections, intra-abdominal infections), yet these designs may not be optimal, and often are not feasible, for study of infections caused by drug-resistant bacteria. Over the past several years, multiple stakeholders have worked to develop consensus regarding paths forward with a goal of facilitating timely conduct of antimicrobial development. Here we advocate for a novel and pragmatic approach and, toward this end, present feasible trial designs for antibacterial agents that could enable conduct of narrow-spectrum, organism-specific clinical trials and ultimately approval of critically needed new antibacterial agents.

Cefazolin versus Nafcillin for Methicillin-Sensitive Staphylococcus aureus Bloodstream Infection in a California Tertiary Medical Center.

Recent observational studies have suggested possible reductions in mortality in patients receiving cefazolin versus antistaphylococcal penicillins. We examined 90-day mortality in patients receiving cefazolin compared to nafcillin for methicillin-susceptible Staphylococcus aureus (MSSA) bloodstream infection (BSI). We identified persons with MSSA BSI admitted to San Francisco General Hospital from January 2008 to July 2013 through a hospital-wide infection surveillance system and confirmed 90-day mortality using U.S. national vital registries. We included persons receiving cefazolin or nafcillin as the predominant intravenous antimicrobial agent; all participants received inpatient Infectious Diseases service consultation. We estimated the association between receipt of cefazolin and 90-day risk of death by multivariate logistic regression, including a propensity score for receiving cefazolin as the second predictor. Of 230 MSSA BSI cases, 30 received nafcillin and 70 received cefazolin as the predominant antimicrobial; 10 died within 90 days, 5 from each group. Unadjusted analysis showed substantial but not statistically significant reduced odds of death in those receiving cefazolin (odds ratio, 0.38; 95% confidence interval [CI], 0.10 to 1.44). Multivariate analysis with propensity scores found a similar adjusted odds ratio (0.40; 95% CI, 0.09 to 1.74; P = 0.22). We found a large reduction in 90-day mortality in those receiving cefazolin compared to nafcillin for MSSA BSI, but this finding was not statistically significant. The magnitude of effect seen in this and other studies justifies further study.

Development of an occupational airborne chemical exposure matrix.

BACKGROUND: Population-based studies of the occupational contribution to chronic obstructive pulmonary disease generally rely on self-reported exposures to vapours, gases, dusts and fumes (VGDF), which are susceptible to misclassification. AIMS: To develop an airborne chemical job exposure matrix (ACE JEM) for use with the UK Standard Occupational Classification (SOC 2000) system. METHODS: We developed the ACE JEM in stages: (i) agreement of definitions, (ii) a binary assignation of exposed/not exposed to VGDF, fibres or mists (VGDFFiM), for each of the individual 353 SOC codes and (iii) assignation of levels of exposure (L; low, medium and high) and (iv) the proportion of workers (P) likely to be exposed in each code. We then expanded the estimated exposures to include biological dusts, mineral dusts, metals, diesel fumes and asthmagens. RESULTS: We assigned 186 (53%) of all SOC codes as exposed to at least one category of VGDFFiM, with 23% assigned as having medium or high exposure. We assigned over 68% of all codes as not being exposed to fibres, gases or mists. The most common exposure was to dusts (22% of codes with >50% exposed); 12% of codes were assigned exposure to fibres. We assigned higher percentages of the codes as exposed to diesel fumes (14%) compared with metals (8%). CONCLUSIONS: We developed an expert-derived JEM, using a strict set of a priori defined rules. The ACE JEM could also be applied to studies to assess risks of diseases where the main route of occupational exposure is via inhalation.

Prospective clinical trial evaluating spironolactone in Doberman pinschers with congestive heart failure due to dilated cardiomyopathy.

INTRODUCTION/OBJECTIVES: Whether the aldosterone antagonist spironolactone has beneficial survival effects in dogs with dilated cardiomyopathy (DCM) is not known. The primary objective of the study was to evaluate the effect of spironolactone, when added to conventional therapy, on survival time in Doberman pinschers with congestive heart failure (CHF) due to DCM. ANIMALS: Sixty-seven client-owned Doberman pinschers with CHF due to DCM. MATERIALS AND METHODS: The trial design was prospective, randomized, blinded, and placebo controlled. Dogs were randomized to receive 50-75 mg of spironolactone twice daily (n = 34) or a placebo (n = 33), in addition to standard CHF therapy. Follow-up visits were targeted every one-six weeks until endpoint. Quality-of-life questionnaire and physical examination were performed at every visit, while renal biochemistry, ECG, echocardiography, and thoracic radiography were reassessed as needed. The primary endpoint was time to cardiac death, defined as death or euthanasia from CHF or sudden death. RESULTS: Median time to primary endpoint in the spironolactone group (183 days) was not statistically significantly different than that for the placebo group (124 days) (P = 0.254). The development of atrial fibrillation (AF) was significantly less frequent in the spironolactone group (n = 7) than the placebo group (n = 15, P = 0.037). CONCLUSIONS: While median time to cardiac death in the spironolactone group was not statistically significantly different than that in the placebo group, adding spironolactone to conventional therapy resulted in reduced occurrence of AF.

Comparison of the Respiratory Resistomes and Microbiota in Children Receiving Short versus Standard Course Treatment for Community-Acquired Pneumonia.

Pediatric community-acquired pneumonia (CAP) is often treated with 10 days of antibiotics. Shorter treatment strategies may be effective and lead to less resistance. The impact of duration of treatment on the respiratory microbiome is unknown. Data are from children (n = 171), ages 6 to 71 months, enrolled in the SCOUT-CAP trial (NCT02891915). Children with CAP were randomized to a short (5 days) versus standard (10 days) beta-lactam treatment strategy. Throat swabs were collected at enrollment and the end of the study and used for shotgun metagenomic sequencing. The number of beta-lactam and multidrug efflux resistance genes per prokaryotic cell (RGPC) was significantly lower in children receiving the short compared to standard treatment strategy at the end of the study (Wilcoxon rank sum test, P < 0.05 for each). Wilcoxon effect sizes were small for beta-lactam (r: 0.15; 95% confidence interval [CI], 0.01 to 0.29) and medium for multidrug efflux RGPC (r: 0.23; 95% CI, 0.09 to 0.37). Analyses comparing the resistome at the beginning and end of the trial indicated that in contrast to the standard strategy group, the resistome significantly differed in children receiving the short course strategy. Relative abundances of commensals such as Neisseria subflava were higher in children receiving the standard strategy, and Prevotella species and Veillonella parvula were higher in children receiving the short course strategy. We conclude that children receiving 5 days of beta-lactam therapy for CAP had a significantly lower abundance of antibiotic resistance determinants than those receiving standard 10-day treatment. These data provide an additional rationale for reductions in antibiotic use when feasible. IMPORTANCE Antibiotic resistance is a major threat to public health. Treatment strategies involving shorter antibiotic courses have been proposed as a strategy to lower the potential for antibiotic resistance. We examined relationships between the duration of antibiotic treatment and its impact on resistance genes and bacteria in the respiratory microbiome using data from a randomized controlled trial of beta-lactam therapy for pediatric pneumonia. The randomized design provides reliable evidence of the effectiveness of interventions and minimizes the potential for confounding. Children receiving 5 days of therapy for pneumonia had a lower prevalence of two different types of resistance genes than did those receiving the 10-day treatment. Our data also suggest that children receiving longer durations of therapy have a greater abundance of antibiotic resistance genes for a longer period of time than do children receiving shorter durations of therapy. These data provide an additional rationale for reductions in antibiotic use.

Clostridium difficile and cytomegalovirus colitis co-infection: search for the hidden 'bug'.

Few cases of co-infection with cytomegalovirus (CMV) and Clostridium difficile colitis have been reported previously. We describe 2 cases of CMV and C. difficile colitis, and review 7 previously published reports. We aim to raise awareness of possible CMV-C. difficile co-infection, especially in refractory cases of C. difficile colitis.

Ceftobiprole is superior to vancomycin, daptomycin, and linezolid for treatment of experimental endocarditis in rabbits caused by methicillin-resistant Staphylococcus aureus.

Beta lactam agents are the most active drugs for the treatment of streptococci and methicillin-susceptible Staphylococcus aureus endocarditis. However, methicillin-resistant S. aureus (MRSA) is resistant to all beta lactam agents licensed to date, and alternative treatments are limited. Ceftobiprole is a novel broad-spectrum cephalosporin that binds with high affinity to PBP 2a, the penicillin binding protein that mediates the methicillin resistance of staphylococci and is active against MRSA. Ceftobiprole was compared to vancomycin, daptomycin, and linezolid in a rabbit model of MRSA aortic valve endocarditis caused by the homogeneously methicillin-resistant laboratory strain COL. Residual organisms in vegetations were significantly fewer in ceftobiprole-treated rabbits than in any other treatment group (P<0.05 for each comparison). In addition, the numbers of organisms in spleens and in kidneys were significantly lower in ceftobiprole-treated rabbits than in linezolid- and vancomycin-treated animals (P<0.05 for each comparison). Anti-MRSA beta lactam agents such as ceftobiprole may represent a significant therapeutic advance over currently available agents for the treatment of MRSA endocarditis.

Relationship between susceptibility to daptomycin in vitro and activity in vivo in a rabbit model of aortic valve endocarditis.

Daptomycin is approved for treatment of Staphylococcus aureus bacteremia and right-sided endocarditis. Increases in daptomycin MICs have been associated with failure. A rabbit model of aortic valve endocarditis was used to determine whether MIC correlates with activity in vivo and whether a higher daptomycin dose can improve efficacy. Two related clinical S. aureus strains, one with a daptomycin MIC of 0.5 microg/ml and the other with a MIC of 2 microg/ml, were used to establish aortic valve endocarditis in rabbits. Daptomycin was administered once a day for 4 days at 12 mg/kg of body weight or 18 mg/kg to simulate doses in humans of 6 mg/kg and 10 mg/kg, respectively. Endocardial vegetations, spleens, and kidneys were harvested and quantitatively cultured. The strain with a MIC of 2 microg/ml had a survival advantage over the strain with a MIC of 0.5 microg/ml with >100 times more organisms of the former in endocardial vegetations at the 12-mg/kg dose in a dual-infection model. Both the 12-mg/kg dose and the 18-mg/kg dose completely eradicated the strain with a MIC of 0.5 from vegetations, spleens, and kidneys. The 12-mg/kg dose was ineffective against the strain with a MIC of 2 in vegetations; the 18-mg/kg dose produced a reduction of 3 log(10) units in CFU in vegetations compared to the controls, although in no rabbit were organisms completely eliminated. Increasing the dose of daptomycin may improve its efficacy for infections caused by strains with reduced daptomycin susceptibility.

A proteolytic transmembrane signaling pathway and resistance to beta-lactams in staphylococci.

beta-Lactamase and penicillin-binding protein 2a mediate staphylococcal resistance to beta-lactam antibiotics, which are otherwise highly clinically effective. Production of these inducible proteins is regulated by a signal-transducing integral membrane protein and a transcriptional repressor. The signal transducer is a fusion protein with penicillin-binding and zinc metalloprotease domains. The signal for protein expression is transmitted by site-specific proteolytic cleavage of both the transducer, which autoactivates, and the repressor, which is inactivated, unblocking gene transcription. Compounds that disrupt this regulatory pathway could restore the activity of beta-lactam antibiotics against drug-resistant strains of staphylococci.

MRI measurement of the canine auditory pathways and relationship with brainstem auditory evoked responses.

The objective of this study was to determine direct measurements of auditory pathways by magnetic resonance imaging (MRI) during the growth period of healthy Beagles, and to discover how canine brainstem auditory evoked response (BAER) latencies vary in relation to these MRI measurements. Eighty healthy Beagles were tested at eight, 16 and 52 weeks of age (stages 1, 2, 3, respectively) with BAER and brain MRI. The BAER interpeak latency (IPL) II-V and brain MRI neural generators of BAER waves II and V were identified. A linear distance was calculated in millimeters in order to determine the approximate length of auditory pathways. Sensory nerve conduction velocity (SNCV) of the auditory pathway between peak II and peak V was calculated for each group. A significant difference was observed between brain MRI distances among the three stages. Mean BAER IPL II-V were not significantly different between the three stages. The progressive growth of the skull and brain witnessed by the progressive increased distance of the MRI auditory pathways between peak II and peak V was not associated with a progressive maturation of the BAER IPL II-V. The SNCV of the auditory pathway between peak II and peak V was 6.14 m/sec for group 1; 6.76 m/sec for group 2; and 7.32 m/sec for group 3.

Increased amounts of a novel penicillin-binding protein in a strain of methicillin-resistant Staphylococcus aureus exposed to nafcillin.

In addition to the four typical penicillin-binding proteins (PBPs), a strain of heterogeneously methicillin-resistant Staphylococcus aureus produced an extra 78-kD PBP (PBP 2a) that had a low affinity for nafcillin and penicillin. Addition of nafcillin to cultures of this strain caused a rapid increase in the amount of this PBP in cell membranes. This increase occurred at subinhibitory concentrations of drug within minutes of exposure, and was blocked by inhibitors of protein and RNA synthesis. This suggests that the synthesis of PBP 2a can be stimulated by exposure to beta-lactam antibiotics. This process may, in part, explain the heterogeneity in methicillin-resistant S. aureus.

Perioperative Prophylaxis for Total Artificial Heart Transplantation.

BACKGROUND: Practice variation regarding perioperative antimicrobial prophylaxis in total artificial heart transplantations (TAH-t) across institutions is unknown. The aim of our survey was to assess the current practices for prevention of infection in TAH-t recipients among different programs. METHODS: An electronic survey was sent to programs that implant Syncardia TAH (Syncardia Systems, Tuscon, Ariz, USA). Proportions were analyzed for categorical variables; means and SDs were analyzed for continuous variables. RESULTS: The majority of centers (80.8%) had a formal surgical infection prophylaxis protocol. For non-penicillin-allergic patients, five (20.1%) institutions reported using a 4-drug regimen, seven (29.2%) used a 3-drug regimen, five (20.1%) used a 2-drug regimen, and seven (29.2%) used a cephalosporin alone. Similar data was seen in the penicillin-allergic patients. Infections were reported to occur postoperatively in 52.2% centers. During the first month after TAH-t, bacteremia represented 27.3%, driveline infections 27.2%, pulmonary infections 9%, and mediastinal infections 18.2%. The most common organisms seen within the first month were Candida spp., Escherichia coli, and Pseudomonas aeruginosa (21.4%). In 65% of centers, the mean rate of death post-TAH-t due to infection was 14.5% (SD, 22.3%). The mean rate of patients surviving until orthotopic heart transplantation was 58.6% (SD, 27.7%). CONCLUSIONS: Preventing infections post-TAH-t is key to decreasing morbidity and mortality. All institutions administered perioperative prophylaxis for TAH-t with significant variation among the centers. The majority of the centers have a formal perioperative prophylactic protocol.

Ceftobiprole: in-vivo profile of a bactericidal cephalosporin.

Resistance to antimicrobials is a significant and growing problem, limiting treatment options, especially for serious Gram-positive infections. Ceftobiprole is a novel broad-spectrum cephalosporin that is active in vitro against streptococci and staphylococci, including penicillin-resistant strains of pneumococci and methicillin-resistant Staphylococcus aureus (MRSA). It maintains the activity of extended-spectrum cephalosporins against Gram-negative bacteria, including Enterobacteriaceae. The in-vivo activity of ceftobiprole has been demonstrated in mouse sepsis and subcutaneous abscess models of infection. Its activity also has been examined in several discriminative models of infection that mimic specific diseases in humans and permit testing of antimicrobial activity under a variety of defined pharmacokinetic conditions. These include experimental pneumonia in mice, a tissue cage model of foreign body infection in rats, and endocarditis models in rats and rabbits. In these models, ceftobiprole exhibits activity equivalent or superior to that of comparators against MRSA, including vancomycin-intermediate strains. These models also confirm the in-vivo activity of ceftobiprole against Gram-negative bacteria that are susceptible in vitro. The results from animal models support the evaluation of the clinical efficacy of ceftobiprole in humans and also predict clinical efficacy in the empirical treatment of severe infections. The broad spectrum of activity may allow ceftobiprole to be used as monotherapy for serious hospital-acquired infections where combination therapy would otherwise be required.

A comparative trial of imipenem versus ceftazidime in the release of endotoxin and cytokine generation in patients with gram-negative urosepsis. Urosepsis Study Group.

Evidence from in vitro experiments and animal and human studies indicate that antibiotic therapy may induce the release of endotoxin from the outer membrane of Gram-negative bacteria. Antibiotics that bind preferentially to penicillin-binding protein-2 (PBP-2)--such as imipenem--are associated with little release of endotoxin, while antibiotics that preferentially bind to PBP-3--such as ceftazidime--are associated with far greater release of endotoxin. We conducted a randomized, multicenter, double-blind study comparing imipenem to ceftazidime in patients with urinary tract infections caused by Gram-negative bacilli associated with signs and symptoms of systemic inflammation. A total of 33 patients were randomized to receive either imipenem (n = 14) or ceftazidime (n = 19) for initial treatment for urosepsis. No differences in plasma endotoxin, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) or urine endotoxin, IL-6 or IL-8 levels were found between the two treatment groups within the first 8 h after antibiotic administration. We conclude that, if differences exist with respect to endotoxin release by these two antimicrobial agents, these differences are not readily demonstrable in this clinical study with carefully defined patients with Gram-negative urinary tract infections.

Atovaquone inhibits the glucuronidation and increases the plasma concentrations of zidovudine.

The pharmacokinetic interaction between atovaquone, a 1,4-hydroxynaphthoquinone, and zidovudine was examined in an open, randomized, three-phase crossover study in 14 patients infected with human immunodeficiency virus. Atovaquone (750 mg every 12 hours) and zidovudine (200 mg every 8 hours) were given orally alone and in combination. Atovaquone significantly increased the area under the zidovudine concentration-time curve (AUC) (1.82 +/- 0.62 micrograms.hr/ml versus 2.39 +/- 0.68 micrograms.hr/ml; p < 0.05) and decreased the oral clearance of zidovudine (2029 +/- 666 ml/min versus 1512 +/- 464 ml/min; p < 0.05). In contrast, atovaquone tended to decrease the AUC of zidovudine-glucuronide (7.31 +/- 1.51 micrograms.hr/ml versus 6.89 +/- 1.42 micrograms.hr/ml; p < 0.1) and significantly decreased the ratio of AUC zidovudine-glucuronide/AUC zidovudine (4.48 +/- 1.94 versus 3.12 +/- 1.1; p < 0.05). The maximum concentration of zidovudine-glucuronide was significantly lowered by atovaquone (5.7 +/- 1.5 versus 4.57 +/- 0.97 micrograms/ml; p < 0.05). Zidovudine had no effect on the pharmacokinetic disposition of atovaquone. Atovaquone appears to increase the AUC of zidovudine by inhibiting the glucuronidation of zidovudine.

Staphylococcus aureus endocarditis: clinical manifestations in addicts and nonaddicts.

Data collected from a prospective multicenter study of endocarditis caused by S. aureus were analyzed to contrast the clinical presentation of the disease between a group of 46 intravenous drug addicts and a group of 35 nonaddicts. Two-thirds of the patients in each group were men. The duration of illness before diagnosis was similar (mean, 9.3 days). Intravenous-drug addicts were younger and had less underlying disease (30% versus 80%) than the non-addicts. When first seen, the drug addicts had signs and symptoms of sepsis and pulmonary embolism, but only 40% had pathologic murmurs. Seventy-six percent had evidence of tricuspid valve infection only. Congestive heart failure and neurologic manifestations were uncommon in addicts. Nonaddicts had infection involving predominantly the left side of the heart (14 mitral valves, 8 aortic valves, 4 both aortic and mitral valves) and 80% had underlying medical diseases. Only half of these patients had pathologic murmurs when first examined, but another 30% developed them later. Congestive heart failure, involvement of the central nervous system, and peripheral embolic or septic complications each occurred in over half of the nonaddicts. Eighty percent of these patients had peripheral stigmas of endocarditis. One intravenous drug addict (2%) and seven nonaddicts (20%) died. Six patients required cardiac valve replacement either during or after a course of antibiotics. Outcome was not related to the titer of peak serum bactericidal tests. Endocarditis caused by S. aureus presents as two distinct clinical syndromes depending on the patient population (intravenous drug user or nonaddict) and the location of infection (right-sided or left-sided). The disease is distinguished from endocarditis due to other causes by its acute onset and its fulminant course manifested by a multitude of septic and embolic complications and its ability to cause heart failure. Medical management alone is often successful but in certain subsets of patients, notably those with infection of aortic or multiple valves, early operation may be necessary.

Benign neonatal sleep myoclonus. Relationship to sleep states.

Neonatal sleep myoclonus is a benign syndrome characterized by myoclonic jerks occurring only during sleep and presenting in the first month of life. There are no associations with abnormal development, neurologic deficits, or seizures. The electroencephalogram is normal and has no correlation with the myoclonic jerks. The myoclonus is present in all sleep states although its frequency is state dependent and greatest during quiet sleep. It is not associated with an arousal response as previously thought. Transient serotonin imbalance and genetic factors might play a role in the pathogenesis of this disorder.

Oral SCH 39304 as primary, salvage, and maintenance therapy for cryptococcal meningitis in AIDS.

To determine the efficacy and toxicity of SCH 39304 in the treatment and suppression of cryptococcal meningitis, we conducted a prospective, noncomparative study in three groups of patients: patients with acute cryptococcal meningitis, patients with acute cryptococcal meningitis in whom other therapies have failed (salvage), and patients who required maintenance therapy. As primary therapy, the patients received up to 14 days or 1 g of amphotericin B followed by SCH 39304 200 mg once daily for 12 weeks. As maintenance therapy, the patients received SCH 39304 600 mg once weekly for 12 months. Of five salvage patients, none completed the study. Two patients died, two patients clinically deteriorated, and one patient was noncompliant. Two of three patients with acute cryptococcal meningitis completed the 12-week primary therapy, and one patient was discontinued from therapy because of a skin rash (95% confidence interval, 14-100%). All four patients who were receiving weekly maintenance therapy followed up to 27 weeks were clinically stable with no change in their serum cryptococcal antigen titer from baseline when the study was prematurely terminated. Elevation of liver function test results developed in three patients and skin rash developed in one patient. The unique pharmacologic and pharmacokinetic properties of SCH 39304 (low incidence of toxicity, long serum half-life, and good penetration into the cerebrospinal fluid) lend promise to pursue other triazole antifungals at higher doses as primary therapy and less frequent dosing for maintenance therapy.

Covert orienting and focusing of attention in children with attention deficit hyperactivity disorder.

Performance on the covert visuo-spatial attentional functions of orienting and focusing by a group of ADHD children (n = 20) was compared to that of age and sex-matched control children. In Experiment 1, responses were given to cued targets at valid and invalid locations. In Experiment 2, responses were given to targets presented in small, medium-sized or large visual field locations. For both experiments, the hypotheses that reaction times of ADHD children would be greater than those of control children and that performance would be asymmetrical, were supported. For Experiment 1, ADHD children showed bilaterally greater 'benefits' from having directed attention to the cued location and greater 'costs' in having to relocate the attentional focus than controls. In Experiment 2, the hypothesis that the function of focusing attention by ADHD children may show breakdown in the usual pattern of an increase in reaction time with focus area was partly supported by the finding of similar reaction times to targets presented in medium-sized and large regions of the left visual hemifield. These results have been interpreted as reflecting a stronger anchorage of attention by ADHD children upon a cued location and an inability to shift covert attention easily to an alternative location. The breakdown of the focusing function suggests adoption of similar time response sets across focus area size by the more compromised right hemisphere.