Stewardship / Resistance Scan for Dec 11, 2018

Susceptibility testing platforms
De-escalation and patient outcome
Highly concerning ICU sepsis
Resistant Klebsiella in pets, people

Etest outperforms disc tests for ceftazidime/avibactam susceptibility

US scientists report that the Etest, made by the French company bioMerieux, outperformed disc tests and is a suitable alternative to broth microdilution (BMD) for testing ceftazidime combined with avibactam against ceftazidime- and meropenem-resistant Klebsiella pneumoniae, according to results published yesterday in the Journal of Antimicrobial Chemotherapy.

Researchers from three US universities and Accelerate Diagnostics in Tucson, Ariz., evaluated the Etest, the 30/20-microgram (mcg) disc (Hardy diagnostics), and the 10/4 mcg disc (Mast Group) against the reference BMD method for 102 gram-negative organisms: 69 ceftazidime- and meropenem-resistant K and 33 multidrug-resistant (MDR) non-K pneumoniae isolates.

The team reported that, although none of the three assays met the defined equivalency threshold against all 102 organisms, the Etest performed best, with categorical agreement of 95% and a major error rate of 6.3%. Against the 69 resistant K pneumoniae isolates, only the Etest and the 10/4 mcg disc met the equivalency threshold. None of the three tests met equivalency for the 33 non-K pneumoniae MDR isolates.

The scientists also pooled the data with those from a previous study of 74 carbapenem-resistant Enterobacteriaceae and from the ceftazidime/avibactam new drug application to bolster the findings.

The authors concluded, "Our data indicate that the Etest is a suitable alternative to BMD for testing ceftazidime/avibactam against ceftazidime- and meropenem-resistant K. pneumoniae. The 30/20 [mcg] discs overestimate resistance and may lead to the use of treatment regimens that are more toxic and less effective."
Dec 10 J Antimicrob Chemother abstract


Study shows no clinical detriment to antibiotic de-escalation for bacteremia

A Spanish team that assessed de-escalation as an antimicrobial stewardship approach in patients with single-pathogen bacteremia caused by Enterobacteriaceae (BSI-E) have determined it was not associated with a poorer clinical outcome, according to their data presented in Clinical Infectious Diseases.

The investigators conducted a post-hoc multicenter analysis involving 516 patients, 241 (47%) of whom had early antibiotic de-escalation, 98 (19%) had late de-escalation, and 180 (35%) had none.

De-escalation refers to reducing the spectrum of antibiotics through discontinuation or switching to a narrower-spectrum antibiotic.

After controlling for confounders, the researchers found that neither early nor late de-escalation was linked to increased death. In addition, de-escalation of any length was not associated with clinical failure or a longer hospital stay.
Dec 8 Clin Infect Dis study


Data show 'alarming' antimicrobial resistance levels in ICU sepsis in India

A single-center case-control study in India has found alarming levels of antimicrobial resistance among sepsis patients admitted to the intensive care unit (ICU), according to results published in Antimicrobial Resistance & Infection Control.

The research team analyzed 77 Escherichia coli isolates from the blood of patients diagnosed as having sepsis and 71 from the stool cultures of patients admitted to the ICU who were not diagnosed as having sepsis. The scientists used polymerase chain reaction to characterize the isolates genetically.

They found that 46% of blood isolates and 22% of fecal isolates were enterotoxigenic E coli (ETEC). They also found that 16% of blood isolates and 28.5% of fecal isolates were enteroaggregative E coli (EAEC). Both ETEC and EAEC are common causes of diarrhea.

In their susceptibility analysis, the investigators found that more than 90% of the blood and more than 70% of the fecal isolates were resistant to cephalosporins. In addition, 68% of blood and 44% of the fecal isolates were found to be producers of extended-spectrum beta-lactamase, which convers resistance to third-generation cephalosporins.

The researchers conclude, "The antimicrobial resistant profile found in this study is alarming and poses a great threat to public health. Apparently, an increased antimicrobial resistance to the extensively used cephalosporins is affecting an optimal drug therapy for patients. In addition, the presence of catheters, prolonged duration of stay in the hospital and poor hygienic conditions due to infrequent urination of the patient can lead to an additional vulnerability."
Dec 7 Antimicrob Resist Infect Control study


Pets, humans can be infected with same resistant Klebsiella lineage

Researchers from Portugal who examined antimicrobial resistance and virulence genes of Klebsiella pneumoniae strains that cause urinary tract infections (UTIs) in dogs and cats and humans found that pets with UTI can be infected with high-risk clonal lineages similar to the ones in humans. The group reported its findings yesterday in the Journal of Antimicrobial Chemotherapy.

For the study, the investigators tested K pneumoniae and K oxytoca isolates from the University of Lisbon that were collected from 24 dogs and cats with UTI from the Lisbon area. They also tested K pneumoniae and K oxytoca isolates from humans with UTI that they obtained from a clinical lab and a hospital lab in the Lisbon area. The specimens from the animals were isolated from 2002 to 2015, and the human ones from the clinical lab were isolated in 2014. The hospital lab samples were isolated randomly from 2006 to 2015.

Disc diffusion testing on 27 animal and 77 human specimens identified resistant isolates, which were then tested by polymerase chain reaction testing for 16 resistance genes and 7 virulence genes. The researchers used multilocus sequence typing on all pet samples and third-generation-cephalosporin (3GC)-resistant isolates from humans.

The blaCTX-M-15 resistance mechanism was detected in more than 80% of 3GC-resistant strains, and the K pneumoniae high-risk ST15 clonal lineage predominated in dog and cat isolates (60%, 15/25). Most of the pet ST15 lineage belonged to two pulsed-field gel electrophoresis clusters (C4 and C5) that also included human strains. Pet and human isolates from the lineage shared a virulence marker, with four also harboring yersiniabactin siderophore-encoding genes. A hospital-adapted lineage was found in a cat and a human, and both of the isolates were MDR.

The team concluded that animal caretakers should take precautions to prevent the spread of antimicrobial-resistant K pneumoniae.
Dec 10 J Antimicrob Chemother abstract

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