diff --git a/argnorm/lib.py b/argnorm/lib.py
index c9024c4..54472c1 100644
--- a/argnorm/lib.py
+++ b/argnorm/lib.py
@@ -8,29 +8,21 @@
 
 _ROOT = os.path.abspath(os.path.dirname(__file__))
 
-def is_number(num):
-    try:
-        int(num)
-    except ValueError:
-        return False
-
-    return True
-
 def get_aro_mapping_table(database):
-    aro_mapping_table = pd.read_csv(os.path.join(_ROOT, 'data', f'{database}_ARO_mapping.tsv'), sep='\t')
-
-    manual_curation = pd.read_csv(os.path.join(_ROOT, 'data/manual_curation', f'{database}_curation.tsv'), sep='\t')
-    manual_curation['Database'] = aro_mapping_table['Database']
-
-    aro_mapping_table = aro_mapping_table.drop_duplicates(subset=['Original ID'], ignore_index=True).set_index('Original ID')
-    for i in manual_curation['Original ID']:
-        if i in aro_mapping_table.index:
-            aro_mapping_table.loc[i, 'ARO'] = manual_curation.set_index('Original ID').loc[i, 'ARO']
-            aro_mapping_table.loc[i, 'Gene Name in CARD'] = manual_curation.set_index('Original ID').loc[i, 'Gene Name in CARD']
-        else:
-            aro_mapping_table.loc[i] = manual_curation.set_index('Original ID').loc[i]
-
-    aro_mapping_table[TARGET_ARO_COL] = aro_mapping_table[TARGET_ARO_COL].map(lambda a: f'ARO:{int(a)}' if is_number(a) else a)
+    aro_mapping_table = pd.read_csv(
+            os.path.join(_ROOT, 'data', f'{database}_ARO_mapping.tsv'),
+            sep='\t')
+    aro_mapping_table.drop_duplicates(subset=['Original ID'], inplace=True)
+    aro_mapping_table.set_index('Original ID', inplace=True)
+
+    manual_curation = pd.read_csv(
+                    os.path.join(_ROOT, 'data/manual_curation', f'{database}_curation.tsv'),
+                    sep='\t', index_col=0)
+    manual_curation['Database'] = aro_mapping_table['Database'].iloc[0]
+    aro_mapping_table.drop(index=set(manual_curation.index) & set(aro_mapping_table.index), inplace=True)
+    aro_mapping_table = pd.concat([aro_mapping_table, manual_curation])
+
+    aro_mapping_table['ARO'] = aro_mapping_table['ARO'].map(lambda a: f'ARO:{int(a)}', na_action='ignore')
     return aro_mapping_table.reset_index()
 
 def map_to_aro(gene, database):
@@ -50,4 +42,4 @@ def map_to_aro(gene, database):
         if type(result) != str:
             return ARO[list(set(result))[0]]
         else:
-            return ARO[result]
\ No newline at end of file
+            return ARO[result]
diff --git a/tests/test_lib.py b/tests/test_lib.py
index 11ced10..3e31d98 100644
--- a/tests/test_lib.py
+++ b/tests/test_lib.py
@@ -1,4 +1,5 @@
-from argnorm.lib import map_to_aro
+import pytest
+from argnorm.lib import map_to_aro, get_aro_mapping_table
 import pronto
 
 def test_map_to_aro():
@@ -18,4 +19,10 @@ def test_map_to_aro():
     ]
 
     for t, e in zip(test_cases, expected_output):
-        assert map_to_aro(t[0], t[1]) == e
\ No newline at end of file
+        assert map_to_aro(t[0], t[1]) == e
+
+@pytest.mark.parametrize('database', ['argannot', 'megares', 'ncbi', 'resfinder', 'resfinderfg'])
+def test_get_aro_mapping_table_smoke(database):
+    df = get_aro_mapping_table(database)
+    assert len(df) > 0
+