MCR-1 detected in Australian E coli isolates

Researchers have identified the colistin resistance gene MCR-1 in Escherichia coli samples from two patients in Australia, according to a report yesterday in Emerging Infectious Diseases.

The gene was detected in colistin-resistant E coli isolated from the urine of two patients in different cities in New South Wales, Australia, in 2011 and 2013. The first patient was a 70-year-old woman who had been in the intensive care unit of a large metropolitan hospital for 2 months; the other was a 71-year-old woman who had sought treatment from a community physician for a urinary tract infection. Neither woman had traveled outside the country in the previous 5 years.

The E coli isolates were among 4,555 Enterobacteriaceae isolates from 2007 through 2016 that were tested for colistin resistance. Overall, 96 isolates (2.1%) were found to be colistin resistant—44 Klebsiella pneumoniae, 18 E coli, 19 Enterobacter spp., 8 Klebsiella oxytoca, 5 Hafnia alvei, and 2 Citrobacter freundii.

Polymerase chain reaction testing confirmed the presence of the MCR-1 gene in the E coli isolates and identified them as belonging to sequence type (ST) 167 and ST93. The authors of the study note that ST167 isolates carrying MCR-1 have been found in chicken meat in China, and that ST93 is a known pathogenic strain that has been associated with transmission of MCR-1 from animals to humans in Laos and China. In addition, the plasmids carrying the gene are identical to previously described MCR-1–bearing plasmids from Asia and the Middle East.

The authors say the findings indicate that MCR-1 "is neither a key mechanism nor yet widely disseminated in this country despite multiple importation events."
May 23 Emerg Infect Dis dispatch

Study: Delayed antibiotics for respiratory infections may be preferable

A new study in The BMJ indicates that delaying antibiotic prescriptions for patients with uncomplicated lower respiratory tract infection is associated with a reduction in reconsultations for new or worsening symptoms and may be preferable to prescribing immediate antibiotics.

The prospective study evaluated 28,779 patients aged 16 and older in the United Kingdom who presented at primary care offices with acute lower respiratory infection, defined as an acute cough that had lasted for as long as 3 weeks. Patients with serious illness were excluded. The main outcomes measured were reconsultation in primary care or a visit to an emergency department with progression of illness in the 30 days after the initial visit, hospital admission, or death.

Of the patients in the study, 7,332 (25.5%) received no prescription for antibiotics, 17,628 (61.3%) received an immediate prescription, and 3,819 (13.3%) received a prescription for delayed antibiotics (median advised delay, 3 days). Subsequent hospital admission or death occurred in 26 of 7,332 patients (0.3%) after no antibiotic prescription, 156 of 7,628 patients (0.9%) after immediate antibiotic prescription, and 14 of 3,819 patients (0.4%) after delayed antibiotic prescription. Multivariable analysis showed that there was no reduction in hospital admission and death after immediate antibiotics (multivariable risk ratio 1.06) and a non-significant reduction with delayed antibiotics (0.81).

Reconsultation for new, worsening, or non-resolving symptoms occurred in 1,443 of 7,332 patients (19.7%) who received no antibiotics, 4,445 of 17,628 patients (25.3%) who received immediate antibiotics, and 538 of 3,819 patients (14.1%) who received delayed antibiotics. Multivariable analysis showed that reconsultation was significantly reduced by delayed antibiotics (multivariable risk ratio 0.64) but not by immediate antibiotics (0.98).

"Prescribing immediate antibiotics may not reduce subsequent hospital admission or death for young people and adults with uncomplicated lower respiratory tract infection, and such events are uncommon," the authors write. "If clinicians are considering antibiotics, a delayed prescription may be preferable since it is associated with reduced number of reconsultations with worsening illness."

An accompanying editorial says that the findings, combined with other studies, indicate that not offering an immediate antibiotic prescription for patients with common acute respiratory infections is a low-risk strategy.
May 22 BMJ study
May 22 BMJ editorial