Aura 2016: first Australian report on antimicrobial use and resistance in human health

5.2 Antimicrobial resistance

Comparisons can be made between rates of resistance in Australia and other countries for a selected number of priority organisms and antimicrobials. The selection is mandated by the availability of representative and comparable national data from national or regional surveillance programs, and data for 2014 or 2013 (but not earlier). Directly comparable data was available from the Australian Group on Antimicrobial Resistance programs in Australia, the European antimicrobial resistance surveillance system (EARS-Net) and a single publication from the United States. All of these sources provided resistance data on isolates from blood and/or cerebrospinal fluid.

Escherichia coli

Figures 5.6–5.8 compare resistance rates in invasive isolates of Escherichia coli from Australia and Europe to fluoroquinolones and third-generation cephalosporins, and combined resistance to fluoroquinolones, third-generation cephalosporins and aminoglycosides.

Figure 5.6 Resistance to fluoroquinolones in invasive isolates of Escherichia coli in Australia and European countries, 2014

Note: In Australia, ciprofloxacin resistance is used to represent resistance to the fluoroquinolone class.

Sources: Australian Group on Antimicrobial Resistance, 2014; EARS-Net, 2014 (Polish data is from 2013)

Rates of resistance to fluoroquinolones in Australia are very low. This can be attributed to the restricted access to fluoroquinolones in Australia, on a background of high use of other antimicrobials.

Resistance to third-generation cephalosporins is also comparatively low in Australia. In part, this may be attributed to the high frequency with which resistance to third-generation cephalosporins (~50%) is linked to fluoroquinolone resistance (~50%). In keeping with the findings for these two antimicrobial classes, rates of combined resistance to fluoroquinolones, third-generation cephalosporins and aminoglycosides are also comparatively low.

Figure 5.7 Resistance to third-generation cephalosporins in invasive isolates of Escherichia coli in Australia and European countries, 2014

Note: In Australia, ceftriaxone resistance is used to represent resistance to the cephalosporin class.

Sources: Australian Group on Antimicrobial Resistance, 2014; EARS-Net, 2014 (Polish data is from 2013)

Figure 5.8 Combined resistance to fluoroquinolones, third-generation cephalosporins and aminoglycosides in invasive isolates of Escherichia coli in Australia and European countries, 2014

Note: In Australia, ciprofloxacin resistance (fluoroquinolones), ceftriaxone resistance (cephalosporins) and gentamicin resistance (aminoglycosides) are used to represent resistance to their respective classes.

Sources: Australian Group on Antimicrobial Resistance, 2014; EARS-Net 2014 (Polish data is from 2013)

Klebsiella pneumoniae

The comparative rates of resistance in Klebsiella pneumoniae are similar to those for E. coli. Figures 5.9–5.11 compare resistance rates in invasive isolates from Australia and Europe to fluoroquinolones and third-generation cephalosporins, and combined resistance to fluoroquinolones, third-generation cephalosporins and aminoglycosides.

Figure 5.9 Resistance to fluoroquinolones in invasive isolates of Klebsiella pneumoniae in Australia and European countries, 2014

Note: In Australia, ciprofloxacin resistance is used to represent resistance to the fluoroquinolone class.

Sources: Australian Group on Antimicrobial Resistance, 2014; EARS-Net, 2014 (Polish data is from 2013)

Figure 5.10 Resistance to third-generation cephalosporins in invasive isolates of Klebsiella pneumoniae in Australia and European countries, 2014

Notes: In Australia, ceftriaxone resistance is used to represent resistance to the cephalosporin class.

Sources: Australian Group on Antimicrobial Resistance, 2014; EARS-Net, 2014 (Polish data is from 2013)

Figure 5.11 Combined resistance to fluoroquinolones, third-generation cephalosporins and aminoglycosides in invasive isolates of Klebsiella pneumoniae in Australia and European countries, 2014

Note: In Australia, ciprofloxacin resistance (fluoroquinolones), ceftriaxone resistance (cephalosporins) and gentamicin resistance (aminoglycosides) are used to represent resistance to their respective classes.

Sources: Australian Group on Antimicrobial Resistance, 2014; EARS-Net, 2014 (Polish data is from 2013)

Staphylococcus aureus and Enterococcus faecium

In contrast to the gram-negative pathogens discussed above, comparative rates of resistance to methicillin in Staphylococcus aureus and to vancomycin in Enterococcus faecium are high to very high in Australia compared with other countries (Figures 5.12 and 5.13). Resistance rates to vancomycin for E. faecium exceed those of any of the European countries contributing to EARS-Net. The reasons for the major difference between comparative rates of resistance in gram-positive bacteria and gram-negative bacteria in Australia are not clear, but it is likely that the drivers for these types of resistance are different. For instance, an analysis of AU in hospitals and hospital-onset enterococcal bacteraemia rates showed that, while certain antimicrobials were associated with enterococcal bacteraemia, other factors such as casemix and infection control practices played a strong role in driving rates of hospital-onset bacteraemia.

Rates of resistance to methicillin in Staphylococcus aureus and to vancomycin in Enterococcus faecium are high to very high in Australia compared with other countries.

Figure 5.12 Methicillin resistance in Staphylococcus aureus in Australia, European countries and the United States, 2014

Sources: Australian Group on Antimicrobial Resistance, 2014; EARS-Net, 2014 (Polish data is from 2013); Sader et al.⁶²

Figure 5.13 Vancomycin resistance in Enterococcus faecium in Australia and European countries, 2014

Sources: Australian Group on Antimicrobial Resistance, 2014; EARS-Net, 2014 (Polish data is from 2013)