An in vitro method for identifying a first microorganism that infects a subject by its species and identifying a second co-infecting microorganism of a different type by its genus comprising: (a) loading a sample obtained from a gram-stain culture into a first cartridge wherein the gram-stain culture identified the sample as comprising a first microorganism that infects a subject and wherein (i) if the first microorganism was identified by the gram-stain as a gram-positive bacteria, the first cartridge comprises a first multiplex pool comprising reagents for amplifying pan-targets for gram-negative bacteria and reagents for amplifying species targets for gram-positive bacteria, and a second multiplex pool comprising reagents for amplifying pan-targets for fungi and reagents for amplifying species targets for gram-positive bacteria wherein the second coinfecting microorganism is a gram negative bacteria or fungi; or (ii) if the first microorganism was identified by the gram-stain as a gram-negative bacteria, the cartridge comprises a first multiplex pool comprising reagents for amplifying pan-targets for gram-positive bacteria and reagents for amplifying species targets for gram-negative bacteria and a second multiplex pool comprising reagents for amplifying pan-targets for fungi and reagents for amplifying species targets for gram-negative bacteria, wherein the second coinfecting microorganism is a gram positive bacteria or fungi; (b) subjecting the sample to a first single multiplex polymerase chain reaction in the first cartridge to produce at least a first amplicon corresponding to the first microorganism and a second amplicon corresponding to the second co-infecting microorganism, wherein the first single multiplex PCR comprises 30 to 35 cycles; (c) electrochemically detecting the first amplicon and the second amplicon produced in step (b) thereby generating a first signal indicative of the first microorganism and a second signal indicative of the second co-infecting microorganism; and (d) identifying the species of the first microorganism based on the first signal and identifying the genus of the second co-infecting microorganism based on the second signal. (a) loading a sample obtained from a gram-stain culture into a first cartridge wherein the gram-stain culture identified the sample as comprising a first microorganism that infects a subject and wherein (i) if the first microorganism was identified by the gram-stain as a gram-positive bacteria, the first cartridge comprises a first multiplex pool comprising reagents for amplifying pan-targets for gram-negative bacteria and reagents for amplifying species targets for gram-positive bacteria, and a second multiplex pool comprising reagents for amplifying pan-targets for fungi and reagents for amplifying species targets for gram-positive bacteria wherein the second coinfecting microorganism is a gram negative bacteria or fungi; or (ii) if the first microorganism was identified by the gram-stain as a gram-negative bacteria, the cartridge comprises a first multiplex pool comprising reagents for amplifying pan-targets for gram-positive bacteria and reagents for amplifying species targets for gram-negative bacteria and a second multiplex pool comprising reagents for amplifying pan-targets for fungi and reagents for amplifying species targets for gram-negative bacteria, wherein the second coinfecting microorganism is a gram positive bacteria or fungi; (b) subjecting the sample to a first single multiplex polymerase chain reaction in the first cartridge to produce at least a first amplicon corresponding to the first microorganism and a second amplicon corresponding to the second co-infecting microorganism, wherein the first single multiplex PCR comprises 30 to 35 cycles; (c) electrochemically detecting the first amplicon and the second amplicon produced in step (b) thereby generating a first signal indicative of the first microorganism and a second signal indicative of the second co-infecting microorganism; and (d) identifying the species of the first microorganism based on the first signal and identifying the genus of the second co-infecting microorganism based on the second signal.