ICAAC 2015

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New research was presented at ICAAC 2015, the American Society for Microbiology’s annual Interscience Conference on Antimicrobial Agents and Chemotherapy, from September 17 to 21 in San Diego. The features below highlight some of the studies that emerged from the conference.

Low Adherence to UTI Guidelines

The Particulars: Levels of adherence with Infectious Disease Society of America guidelines for the treatment of uncomplicated urinary tract infection (UTI) are not well known.
Data Breakdown: For a study, researchers examined the prescribing of antibiotics from 2011 to 2014 for uncomplicated UTIs. Fluoroquinolones were most commonly prescribed (52% of cases), followed by nitrofurantoin (36%), with a trend toward decreasing use of the latter in each successive year of the study. Combination trimethoprim and sulfamethoxazole comprised 12% of prescriptions and was increasingly used during the study period. More than 70% of fluoroquinolone and more than 80% of trimethoprim and sulfamethoxazole prescriptions were for longer than the recommended 3 days. More than 75% of nitrofurantoin prescriptions were for longer than the recommended 5 days.
Take Home Pearl: Primary care providers appear to not often adhere to guidelines for the treatment of uncomplicated UTIs.


New Test Diagnoses Staph in 20 Minutes

The Particulars: Diagnostic tests for identifying Staphylococcus aureus in blood samples can take up to 18 to 24 hours to produce results. The outcomes of a 20-minute diagnostic test are not well known.
Data Breakdown: Arizona State University researchers compared the outcomes of 100 patients with gram-positive coccidioidomycosis infections whose blood samples were tested with PNA FISH, an assay that takes 90 minutes to complete, or with QuickFISH, an assay that takes 20 minutes to complete. Samples tested with QuickFISH had average turnaround times of 66 minutes, compared with 8 to 10 hours for PNA FISH samples.  Shorter turnaround times allowed for reduced hospital lengths of stay (9.6 days vs 12.0 days) for those with S. aureus and those with coagulase-negative staphylococci (4.12 days vs 4.96 days). Prompt results with QuickFISH also prevented patients with coagulase-negative staphylococci from receiving inappropriate vancomycin treatment.
Take Home Pearl: The 20-minute QuickFISH diagnostic test for identifying S. aureus appears to provide test results faster than older tests, reduce hospital lengths of stay, and eliminate unnecessary antibiotic treatment.


CDI Doubles Mortality & Costs in the Elderly

The Particulars: Previous research analyzing the burden of Clostridium difficile infection (CDI) tends to focus on either the inpatient or outpatient setting. Few studies have taken a global perspective.
Data Breakdown: For a study, researchers compared mortality rates and healthcare costs for patients aged 65 and older with and without incident C. difficile for 1 year. Patients with CDI-associated disease had a mortality rate of 42.6%, compared with a rate of 23.4% for those without CDI. Average healthcare costs were $64,807 for those with CDI and $38,128 for those without CDI.
Take Home Pearl: Among patients aged 65 and older, CDI appears to nearly double the mortality rate and associated healthcare costs when compared with no CDI.


A More Accurate Assay for TB

The Particulars: Data from the World Health Organization show that one-third of the global population is infected with tuberculosis (TB), 10% of whom develop active disease. Identifying those with latent TB with an accurate assay allows for treatment before active disease develops.
Data Breakdown: For a study, researchers collected blood samples from patients with TB or with low risk for TB and compared the abilities of two assays in detecting TB. The currently used QuantiFERON TB Gold In-Tube (QFT-GIT) assay had a specificity of 99.0% for TB in patients who tested positive for TB and a sensitivity of 89.0% in patients who tested negative for TB. A new generation of QFT-GIT with updated technology detected TB infection with a specificity of 97.6% in patients who tested positive for TB and found no infection in 98.1% of those who tested negative.
Take Home Pearl: An updated QFT-GIT assay for detecting TB appears to be more accurate than the currently used QFT-GIT assay.


Vaccines Reduce Pediatric Hospital Burden

The Particulars: Previous studies show that winter respiratory and diarrheal disease in infants and young children are often due to infections caused by Streptococcus pneumoniae and rotavirus, respectively. Newly available pneumococcal conjugate vaccines (PCVs) and rotavirus vaccines have both made large impacts on fighting these infections. However, their combined impacts on hospital burden, particular during the fall and winter seasons, is not well known.
Data Breakdown: The combined effect of the co-administration of PCVs and rotavirus vaccines were observed for a study. Within 5 years of their introduction, hospital admission rates for children younger than 2 years decreased 78% for hospitalizations due to rotavirus diarrhea in and by 46% for those due to pneumonia. For outpatient visits, these rates were 80% and 67%, respectively.
Take Home Pearl: The introduction of both PCV and rotavirus vaccines appears to have led to substantial reductions in hospital burden of both winter diarrhea and respiratory infections within 5 years.


Microbial Diversity & Infection During Chemotherapy

The Particulars: Many microorganisms live in harmony with their human hosts, providing functions that are essential for human health and survival. Patients undergoing cancer treatment may experience disruptions to their microbiomes due to illness or various therapeutics.

Data Breakdown: For a study, University of Texas MD Anderson Cancer Center researchers analyzed stool and saliva samples in patients undergoing chemotherapy. The team found that disruptions to the microbiome by illness or administration of therapeutics often led to infections during chemotherapy. Patients who developed infections during chemotherapy had significantly lower baseline microbial diversities in their stool samples when compared with patients who did not develop infections. Patients who maintained a healthy microbiome remained infection free for 90 days after taking chemotherapy.
Take Home Pearls: Patients’ microbial diversity before and during cancer treatment appears to be linked with the risk of infection during induction chemotherapy. Baseline microbiome sampling may help predict the risk of infection during chemotherapy and subsequent treatments. This sampling may also potentially mitigate the overuse of antimicrobials.


A Novel Approach to Staph Bloodstream Infections

The Particulars: Laboratory-based research suggests that high-density methicillin-susceptible Staphylococcus aureus (MSSA) infections treated with cefazolin may result in higher rates of antibiotic failure when compared with nafcillin due to the presence of specific enzymes that break down the antibiotic’s structure. These findings have yet to be confirmed in the clinical setting.
Data Breakdown: The outcomes of patients receiving nafcillin for MSSA bloodstream infections were compared with those of patients receiving cefazolin for a study. Patients treated with nafcillin had a treatment failure rate of 14.0%, compared with a rate of 8.4% observed in patients treated with cefazolin. Rates of high-burden infections were similar between the two groups. Naficillin-treated patients had an adverse event rate of 19.7%, compared with a rate of 7.0% among cefazolin-treated patients.
Take Home Pearl: Among patients with MSSA bloodstream infections, cefazolin appears to have a lower treatment failure rate and significantly lower adverse effect rate when compared with nafcillin.


Treat Virulent Bone & Joint Infections Aggressively

The Particulars: Few studies have assessed the outcomes of treatment for Staphylococcus lugdunensis.
Data Breakdown: For a study, researchers assessed patients with bone and joint infections caused by S lugdunensis between 1995 and 2014. The majority of infections were associated with orthopedic devices, among which nearly 90% occurred more than 1 month after device implantation. Following treatment with amputation, removal of the device, prosthesis exchange or removal, or surgical debridement with retention of the device, 76% of patients recovered, 19% experienced remission, and 3% died.
Take Home Pearls: Bone and joint infections caused by Staphylococcus lugdunensis appear to have a high rate of relapse. The majority of these infections appear to occur more than 1 year after orthopedic device implantation, suggesting that patients with these infections should be treated quickly and followed for 2 years.


Reducing Clostridium difficile Recurrence

The Particulars: Clostridium difficile infections (CDIs) have been shown to have a high rate of recurrence. A small number of antibiotics are currently used to treat these infections, which tend to be caused by antibiotic use. Monoclonal antibodies may help reduce this risk.

Data Breakdown: For a study, patients treated with standard of care antibiotics for CDI were administered a single infusion of actoxumab, bezlotoxumab, a combination of the two, or placebo. Recurrence rates were 28% for placebo, 26% for actoxumab, 17% for bezlotoxumab, and 16% for the actoxumab/bezlotoxumab combination. Bezlotoxumab was well tolerated and had similar efficacy to the actoxumab/bezlotoxumab combination with an equivalent safety profile.
Take Home Pearl: The monoclonal antibody bezlotoxumab appears to reduce the rate of CDI recurrence when compared with placebo or actoxumab.


Breath Test Detects Tuberculosis

The Particulars: Data indicate that most tuberculosis (TB) cases worldwide are diagnosed with culture methods that can be time-consuming and require significant expertise. Breath sample testing has the potential to be cheaper, faster, and more widely available, allowing for earlier treatment and better outcomes.

Data Breakdown: A small study recruited patients with TB and controls known to not have TB to determine if the novel technology Field Asymmetric Ion Mobility Spectrometry could accurately detect TB. The test had a sensitivity of 93% and a specificity of 94% in detecting varying forms of TB.
Take Home Pearls: A novel breath test appears to accurately detect various forms of tuberculosis. Repeat analyses are needed to confirm these results in a larger study population.

For more information on these studies and others that were presented at ICAAC 2015, visit

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