| bacillus subtilis | 219 | species | bacteria | bacteria | 1423 |
| bacillus cereus | 111 | species | bacteria | bacteria | 1396 |
| bacillus anthracis | 122 | species | bacteria | bacteria | 1392 |
| babesia microti | 53 | species | invertebrates | protozoa | 5868 |
| australian bat lyssavirus | 15 | species | viruses | viruses | 90961 |
| aspergillus niger | 110 | species | plants | fungi | 5061 |
| aspergillus fumigatus | 109 | species | plants | fungi | 746128 |
| aspergillus flavus | 81 | species | plants | fungi | 5059 |
| ascaris suum | 65 | species | invertebrates | helminths | 6253 |
| ascaris lumbricoides | 69 | species | invertebrates | helminths | 6252 |
| araraquara virus | 5 | no rank | viruses | viruses | 139032 |
| aracatuba virus | 1 | no rank | viruses | viruses | 201444 |
| angiostrongylus cantonensis | 35 | species | invertebrates | helminths | 6313 |
| anaplasma phagocytophilum | 62 | species | bacteria | bacteria | 948 |
| anaerococcus prevotii | 17 | species | bacteria | bacteria | 33034 |
| alexandrium tamarense | 35 | species | plants | protozoa | 2926 |
| alcelaphine herpesvirus 1 | 26 | species | viruses | viruses | 35252 |
| akabane virus | 21 | species | viruses | viruses | 70566 |
| agrobacterium tumefaciens | 155 | species | bacteria | bacteria | 358 |
| aggregatibacter aphrophilus | 19 | species | bacteria | bacteria | 732 |
| african swine fever virus | 48 | species | viruses | viruses | 10497 |
| african horse sickness virus | 28 | species | viruses | viruses | 40050 |
| african cassava mosaic virus | 55 | species | viruses | viruses | 10817 |
| adeno-associated virus 9 | 3 | species | viruses | viruses | 235455 |
| adeno-associated virus 3b | -1 | no rank | viruses | viruses | 68742 |
| adeno-associated virus 2h | -1 | no rank | viruses | viruses | 10805 |
| adeno-associated virus 12 | -1 | species | viruses | viruses | 235458 |
| adeno-associated virus 11 | -1 | species | viruses | viruses | 235457 |
| adeno-associated virus 10 | 1 | species | viruses | viruses | 235456 |
| adeno-associated virus - 8 | 7 | no rank | viruses | viruses | 202813 |
| adeno-associated virus - 7 | -1 | no rank | viruses | viruses | 202812 |
| adeno-associated virus - 6 | 8 | no rank | viruses | viruses | 68558 |
| adeno-associated virus - 5 | 2 | species | viruses | viruses | 82300 |
| adeno-associated virus - 4 | 4 | species | viruses | viruses | 57579 |
| adeno-associated virus - 3 | 2 | species | viruses | viruses | 46350 |
| adeno-associated virus - 2 | 79 | species | viruses | viruses | 10804 |
| adeno-associated virus - 1 | 14 | species | viruses | viruses | 85106 |
| actinomyces naeslundii | 49 | species | bacteria | bacteria | 1655 |
| actinomyces israelii | 25 | species | bacteria | bacteria | 1659 |
| acinetobacter radioresistens | 23 | species | bacteria | bacteria | 40216 |
| acinetobacter lwoffii | 27 | species | bacteria | bacteria | 28090 |
| acinetobacter calcoaceticus subsp. anitratus | 23 | subspecies | bacteria | bacteria | 107673 |
| acinetobacter calcoaceticus | 77 | species | bacteria | bacteria | 471 |
| acinetobacter baumannii | 88 | species | bacteria | bacteria | 470 |
| acanthamoeba polyphaga | 40 | species | invertebrates | protozoa | 5757 |
| acanthamoeba castellanii | 78 | species | invertebrates | protozoa | 5755 |
| abrus precatorius | 27 | species | plants | | 3816 |
| [haemophilus] ducreyi | 57 | species | bacteria | bacteria | 730 |
| [enterobacter] aerogenes | 75 | species | bacteria | bacteria | 548 |