The effects of tidal cycling and lack of connectivity between waterways and surrounding landscapes likely contributed to the lack of association between local land uses and microbial outcomes, though weak associations may also be indicative of mismatched spatiotemporal scales.
One study provided strong evidence of failure to control microbial outcomes despite a successful change in prescribing (32 ).
To understand how much of a change in prescribing is required to change outcome, the intervention must be independent of other control measures and be accompanied by reliable data about both prescribing and microbial outcomes.
Our primary conclusion is that 4 of the 16 studies provided strong evidence that changes in prescribing antimicrobial drugs to hospital inpatients can improve microbial outcomes (17, 27, 30, 31 ).
Eight of the remaining studies provided some evidence that antimicrobial drug prescribing interventions can improve microbial outcomes, but flaws in their design indicated that there were plausible alternative explanations for the results (18 – 20, 23, 24, 26, 28, 29 ).
Four studies provided strong evidence that the intervention changed microbial outcomes with low risk for alternative explanations, 8 studies provided less convincing evidence, and 4 studies provided no evidence.
We required studies to provide reliable data about the effect of interventions on both microbial and drug outcomes with clear case definition, description of infection control measures, and other variables such as bed occupancy or staffing levels that could provide plausible alternative explanations for changes in microbial outcomes.
However, from the microbial perspective, Outcome I events also generate a new host cell for infection and potentially doom the infected daughter cell by burdening it with a higher intracellular microbial load.
