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+# Apply EUCAST rules
+
+## Introduction
+
+What are EUCAST rules? The European Committee on Antimicrobial
+Susceptibility Testing (EUCAST) states [on their
+website](https://www.eucast.org/expert_rules_and_expected_phenotypes):
+
+> *EUCAST expert rules (see below) are a tabulated collection of expert
+> knowledge on interpretive rules, expected resistant phenotypes and
+> expected susceptible phenotypes which should be applied to
+> antimicrobial susceptibility testing in order to reduce testing,
+> reduce errors and make appropriate recommendations for reporting
+> particular resistances.*
+
+In Europe, a lot of medical microbiological laboratories already apply
+these rules ([Brown *et al.*,
+2015](https://www.eurosurveillance.org/content/10.2807/1560-7917.ES2015.20.2.21008)).
+Our package features their latest insights on expected resistant
+phenotypes (v1.2, 2023).
+
+## Examples
+
+These rules can be used to discard improbable bug-drug combinations in
+your data. For example, *Klebsiella* produces beta-lactamase that
+prevents ampicillin (or amoxicillin) from working against it. In other
+words, practically every strain of *Klebsiella* is resistant to
+ampicillin.
+
+Sometimes, laboratory data can still contain such strains with
+*Klebsiella* being susceptible to ampicillin. This could be because an
+antibiogram is available before an identification is available, and the
+antibiogram is then not re-interpreted based on the identification. The
+[`eucast_rules()`](https://amr-for-r.org/reference/eucast_rules.md)
+function resolves this, by applying the latest ‘EUCAST Expected
+Resistant Phenotypes’ guideline:
+
+``` r
+oops <- tibble::tibble(
+  mo = c(
+    "Klebsiella pneumoniae",
+    "Escherichia coli"
+  ),
+  ampicillin = as.sir("S")
+)
+oops
+#> # A tibble: 2 × 2
+#>   mo                    ampicillin
+#>   <chr>                 <sir>     
+#> 1 Klebsiella pneumoniae   S       
+#> 2 Escherichia coli        S  
+
+eucast_rules(oops, info = FALSE, overwrite = TRUE)
+#> # A tibble: 2 × 2
+#>   mo                    ampicillin
+#>   <chr>                 <sir>     
+#> 1 Klebsiella pneumoniae   R       
+#> 2 Escherichia coli        S  
+```
+
+A more convenient function is
+[`mo_is_intrinsic_resistant()`](https://amr-for-r.org/reference/mo_property.md)
+that uses the same guideline, but allows to check for one or more
+specific microorganisms or antimicrobials:
+
+``` r
+mo_is_intrinsic_resistant(
+  c("Klebsiella pneumoniae", "Escherichia coli"),
+  "ampicillin"
+)
+#> [1]  TRUE FALSE
+
+mo_is_intrinsic_resistant(
+  "Klebsiella pneumoniae",
+  c("ampicillin", "kanamycin")
+)
+#> [1]  TRUE FALSE
+```
+
+EUCAST rules can not only be used for correction, they can also be used
+for filling in known resistance and susceptibility based on results of
+other antimicrobials drugs. This process is called *interpretive
+reading*, and is basically a form of imputation:
+
+``` r
+data <- tibble::tibble(
+  mo = c(
+    "Staphylococcus aureus",
+    "Enterococcus faecalis",
+    "Escherichia coli",
+    "Klebsiella pneumoniae",
+    "Pseudomonas aeruginosa"
+  ),
+  VAN = "-", # Vancomycin
+  AMX = "-", # Amoxicillin
+  COL = "-", # Colistin
+  CAZ = "-", # Ceftazidime
+  CXM = "-", # Cefuroxime
+  PEN = "S", # Benzylenicillin
+  FOX = "S"  # Cefoxitin
+)
+```
+
+``` r
+data
+```
+
+| mo                     | VAN | AMX | COL | CAZ | CXM | PEN | FOX |
+|:-----------------------|:---:|:---:|:---:|:---:|:---:|:---:|:---:|
+| Staphylococcus aureus  | \-  | \-  | \-  | \-  | \-  |  S  |  S  |
+| Enterococcus faecalis  | \-  | \-  | \-  | \-  | \-  |  S  |  S  |
+| Escherichia coli       | \-  | \-  | \-  | \-  | \-  |  S  |  S  |
+| Klebsiella pneumoniae  | \-  | \-  | \-  | \-  | \-  |  S  |  S  |
+| Pseudomonas aeruginosa | \-  | \-  | \-  | \-  | \-  |  S  |  S  |
+
+``` r
+eucast_rules(data, overwrite = TRUE)
+```
+
+| mo                     | VAN | AMX | COL | CAZ | CXM | PEN | FOX |
+|:-----------------------|:---:|:---:|:---:|:---:|:---:|:---:|:---:|
+| Staphylococcus aureus  | \-  |  S  |  R  |  R  |  S  |  S  |  S  |
+| Enterococcus faecalis  | \-  | \-  |  R  |  R  |  R  |  S  |  R  |
+| Escherichia coli       |  R  | \-  | \-  | \-  | \-  |  R  |  S  |
+| Klebsiella pneumoniae  |  R  |  R  | \-  | \-  | \-  |  R  |  S  |
+| Pseudomonas aeruginosa |  R  |  R  | \-  | \-  |  R  |  R  |  R  |