The highly infectious bacteria can survive treatment at local sewage plants and enter the food chain of surrounding populations, the study revealed

Researchers at the University of Edinburgh (UE) in Scotland found large amounts of antimicrobial-resistance (AMR) genes in hospital wastewater. These findings will be of interest to microbiologists and clinical laboratory managers, as the scientists used metagenomics to learn “how abundances of AMR genes in hospital wastewater are related to clinical activity.”

The UE study sheds light on the types of bacteria in wastewater that goes down hospital pipes to sewage treatment plants. The study also revealed that not all infectious agents are killed after passing through waste treatment plants. Some bacteria with antimicrobial (or antibiotic) resistance survive to enter local food sources. 

The scientists concluded that the amount of AMR genes found in hospital wastewater was linked to patients’ length-of-stays and consumption of antimicrobial resistant bacteria while in the hospital.

Using Metagenomics to Surveille Hospital Patients

Antimicrobial resistance is creating super bacteria that are linked to increases in hospital-acquired infections (HAIs) nationwide. Dark Daily has reported many times on the growing danger of deadly antimicrobial resistant “super bugs,” which also have been found in hospital ICUs (see “Potentially Fatal Fungus Invades Hospitals and Public Is Not Informed,” August 26, 2019.)

In a paper the University of Edinburgh published on medRxiv, the researchers wrote: “There was a higher abundance of antimicrobial-resistance genes in the hospital wastewater samples when compared to Seafield community sewage works … Sewage treatment does not completely eradicate antimicrobial-resistance genes and thus antimicrobial-resistance genes can enter the food chain through water and the use of [processed] sewage sludge in agriculture. As hospital wastewater contains inpatient bodily waste, we hypothesized that it could be used as a representation of inpatient community carriage of antimicrobial resistance and as such may be a useful surveillance tool.”

Additionally, they wrote, “Using metagenomics to identify the full range of AMR genes in hospital wastewater could represent a useful surveillance tool to monitor hospital AMR gene outflow and guide environmental policy on AMR.”

AMR bacteria also are being spread by human touch throughout city subways, bus terminals, and mass transportation, making it difficult for the Centers for Disease Control and Prevention (CDC) to identify the source of the outbreak and track and contain it. This has led microbiologists to conduct similar studies using genetic sequencing to identify ways to track pathogens through city infrastructures and transportation systems. (See, “Microbiologists at Weill Cornell Use Next-Generation Gene Sequencing to Map the Microbiome of New York City Subways,” December 13, 2013.)

Antimicrobial stewardship programs are becoming increasingly critical to preventing the spread of AMR bacteria. “By having those programs, [there are] documented cases of decreased antibiotic resistance within organisms causing these infections,” Paul Fey, PhD, of the University of Nebraska Medical Center, told MedPage Today. “This is another indicator of how all hospitals need to implement stewardship programs to have a good handle on decreasing antibiotic use.” [Photo copyright: University of Nebraska.]

Don’t Waste the Wastewater

Antibiotic resistance occurs when bacteria change in response to medications to prevent and treat bacterial infections, according to a World Health Organization (WHO) fact sheet. The CDC estimates that more than 23,000 people die annually from two million antibiotic-resistance infections.

Wastewater, the UE scientists suggest, should not go to waste. It could be leveraged to improve hospitals’ detection of patients with antimicrobial resistance, as well as to boost environment antimicrobial-resistance polices.

They used metagenomics (the study of genetic material relative to environmental samples) to compare the antimicrobial-resistance genes in hospital wastewater against wastewater from community sewage points. 

The UE researchers:

  • First collected samples over a 24-hour period from various areas in a tertiary hospital;
  • They then obtained community sewage samples from various locations around Seafield, Scotland;
  • Finally, they complete the genetic sequencing on an Illumina HiSeq4000 System.

The researchers reported these findings:

  • 181 clinical isolates were identified in the samples of wastewater;
  • 1,047 unique bacterial genes were detected across all samples;
  • 19 genes made up more than 60% of bacteria in samples;
  • Overriding bacteria identified as Pseudomonas and Acinetobacter environmental samples (Pseudomonas fluorescens and Acinetobacter johnsonii) were most likely from hospital pipes;
  • Gut-related bacteria—Faecalibacterium, Bacteroides, Bifidobacterium, and Escherichia, were more prevalent in the hospital samples than in those from the community;
  • Antimicrobial-resistance genes increased with longer length of patient stays, which “likely reflects transmission amongst hospital inpatients,” researchers noted. 

Fey suggests that further research into using sequencing technology to monitor patients is warranted.

“I think that monitoring each patient and sequencing their bowel flora is more likely where we’ll be able to see if there’s a significant carriage of antibiotic-resistant organisms,” Fey told MedPage Today. “In five years or so, sequencing could become so cheap that we could monitor every patient like that.”

Fey was not involved in the University of Edinburgh research.

Given the rate at which AMR bacteria spreads, finding antibiotic-resistance genes in hospital wastewater may not be all that surprising. Still, the University of Edinburgh study could lead to cost-effective ways to test the genes of bacteria, which then could enable researchers to explore different sources of infection and determine how bacteria move through the environment.

And, perhaps most important, the study suggests clinical laboratories have many opportunities to help eliminate infections and slow antibiotic resistance. Microbiologists can help move their organizations forward too, along with infection control colleagues.  

—Donna Marie Pocius

Related Information:

Secrets of the Hospital Underbelly: Abundance of Antimicrobial-Resistance Genes in Hospital Wastewater Reflects Hospital Microbial Use and Inpatient Length of Stay

Antibiotic-Resistance Genes Trouble Hospital Water; Study Emphasizes Importance of Antibiotic Stewardship Programs, Expert Says

Fact Sheet: Antibiotic Resistance

United States Gathers 350 Commitments to Combat Antibiotic Resistance, Action Must Continue

Genomic Analysis of Hospital Plumbing Reveals Diverse Reservoir of Bacterial Plasmids Conferring Carbapenemase Resistance

Dark Daily E-briefings: Hospital-Acquired Infections

NIH Study Reveals Surprising New Source of Antibiotic Resistance that Will Interest Microbiologists and Medical Laboratory Scientists