MICROBE 2018 recap - AMR in the Americas, Highlights

Highlights from the Session:

Surveillance of Antibacterial Resistance in the Americas

Mariana Castanheira, JMI Laboratories and the SENTRY Program

• The SENTRY program was established in 1997 and is one of the longest running antimicrobial surveillance programs globally. Check out their website for more information and access to visualizations of their surveillance. One of the things I note is the obvious need for AMR surveillance in Africa and parts of the middle east where I see by their map much data is missing/lacking.
• Some major sequence types to keep a close eye on with respect to growing and expanding resistance in the Americas (especially Latin America) include E. coli ST131 and K. pneumoniae ST258.
• When interrogating genes for resistance in E. coli and K. pneumoniae it was found that diversity within resistance encoding genes was higher in E. coli than K. pneumoniae. 
• 0.5% of E. coli have been found resistant to Colistin
• 2.3% of K. pneumoniae have been found resistant to  Colistin
• mcr1 was found in E. coli while K. pneumoniae appeared to multiple mechanisms and genes involved conferring colistin resistance including mcr1, mrgB disruption or alteration, and pmrB.
• A. baumannii has show increasing resistance profiles within Latin America when 1997-2000 was compared to 2013-2016. Rises were seen in resistance to:
• Meropenem (18.4% to 86.3%) 
• Levofloxacin (76.9% to 87.6%)
• Amikacin (77.3% to 82.4%)
• Ampicillin-sulbactam (70.7% to 83.6%)
• Colistin (0.8% to 3.4%).
•  Of note: Susceptible and resistant isolates have been shown to have the same pattern of expression of their resistance encoding genes so you cannot use that as a marker of organisms 'resistance'. 

Khalil Chedid - University of Michigan

• The primary treatment for Methicillin-resistant staphylococcus aureus (MRSA) is Vancomycin yet we are starting to see resistant isolates with one of the first cases of vancomycin-resistant staphylococcus aureus (VRSA) appearing in 2002.
• Vancomycin genes are collocated on a plasmid which can be acquired through conjugation between bacteria and there is epidemiological evidence to support co-infections or co-colonization that would facilitate this transfer.
• There is no human to human direct transmission of VRSA so all events that have been recorded to date are independent.
• In a case/control study looking at individuals with VRE (vancomycin resistance E. coli) only, MRSA only, no MRSA or VRE they found:
• A correlation with ST5 and coinfection
• Residence prior to hospital stay, history of chronic skin wounds and previous MRSA infection has an association with coinfection
• There was no correlation between length of stay and coinfection so the longer you are in the hospital doesn't appear to exacerbate the problem.
• Isolates were taken from a variety of body sites sometimes isolated from two different sizes in the same individual.
• It is difficult to tease apart infector and colonizer - more sample collection and analysis will allow the development of methods to differentiate the two.
• ST5 persists longer within an individual so those that carry ST5 are at higher risk for coinfection.
• There is evidence to suggest a fitness cost to acquiring vancomycin resistance and isolates may not be surviving in the host as long.

A good point brought up by several in the session including Dr. Flavia Rossi is that 

...the problem of talking about resistance in Latin America is that you have many variables at play including diversity, geographical and social differences all of which contribute and shape the problem uniquely.

Ayesha Khan spoke about the emergence of P. aeruginosa ST309 which harbors genes with resistance carbapenenms, ceftazidme/avibactam and ceftolozane/tazobactam. Phylogenetic analysis shows that ST309 harboring the resistance determinants (GES enzymes) acquired a class 1 integron and were clustering with strains originating from the US and Mexico. This suggests this highly resistant ST309 could be an emerging threat in North America.

One of Ayesha's latest papers: Mechanisms of antimicrobial resistance among hospital-associated pathogens - 2018.

Dr. Shelley Magill, a medical epidemiologist with the CDC committed to improving AMR surveillance in the US. She took us through some tools available through the CDC for AMR surveillance including:

• The National Healthcare Safety Network (NHSN)
• One of the largest US tracking systems for healthcare associated infections
• Antibiotic Resistance Lab Network (ARLN)
• Multi-drug resistant organisms and C. difficile Infection (MDRO & CDI) LabID Event Modules/Calculator
• Healthcare-Associated infections - Community Interface (HAIC)
• CDC Emerging Infections Program (EIP)
• They also have several modules that are device and/or procedure specific including: CLABSI, CAUTI, VAP, VAE and SSI
• The AR Patient Safety Atlas (also accessible via this link as well)
• National AR Report via NARMS