A method for determining a mechanism for an antimicrobial susceptibility phenotype, comprising: - providing a sample comprising at least one microorganism that is not susceptible to at least one antimicrobial agent; - contacting the sample with the antimicrobial agent, wherein the antimicrobial agent can kill, inhibit the growth, or otherwise compromise the viability of one or more microorganisms; - contacting the at least one microorganism with at least one compound comprising an oligonucleotide molecule targeting at least one specific nucleic acid sequence that is involved in a non-susceptible phenotype to the antimicrobial agent; - contacting the sample with a non-replicative transduction particle (NRTP) comprising a reporter nucleic acid molecule encoding a reporter molecule under conditions such that the NRTP inserts into the microorganism the reporter nucleic acid molecule and such that the reporter molecule provides the detectable indication of viability; and - determining the mechanism for the antimicrobial susceptibility phenotype of the microorganism based on the presence or absence of a detectable indication of viability associated with the microorganism when the microorganism is in contact with the antimicrobial agent and the oligonucleotide molecule, wherein the presence of the detectable indication of viability indicates that the specific nucleic acid sequence targeted by the oligonucleotide molecule is not related to the mechanism for the antimicrobial susceptibility phenotype to the antimicrobial agent, and wherein the absence of the detectable indication of viability indicates that the specific nucleic acid sequence targeted by the oligonucleotide molecule is related to the mechanism for the antimicrobial susceptibility phenotype to the antimicrobial agent. - providing a sample comprising at least one microorganism that is not susceptible to at least one antimicrobial agent; - contacting the sample with the antimicrobial agent, wherein the antimicrobial agent can kill, inhibit the growth, or otherwise compromise the viability of one or more microorganisms; - contacting the at least one microorganism with at least one compound comprising an oligonucleotide molecule targeting at least one specific nucleic acid sequence that is involved in a non-susceptible phenotype to the antimicrobial agent; - contacting the sample with a non-replicative transduction particle (NRTP) comprising a reporter nucleic acid molecule encoding a reporter molecule under conditions such that the NRTP inserts into the microorganism the reporter nucleic acid molecule and such that the reporter molecule provides the detectable indication of viability; and - determining the mechanism for the antimicrobial susceptibility phenotype of the microorganism based on the presence or absence of a detectable indication of viability associated with the microorganism when the microorganism is in contact with the antimicrobial agent and the oligonucleotide molecule, wherein the presence of the detectable indication of viability indicates that the specific nucleic acid sequence targeted by the oligonucleotide molecule is not related to the mechanism for the antimicrobial susceptibility phenotype to the antimicrobial agent, and wherein the absence of the detectable indication of viability indicates that the specific nucleic acid sequence targeted by the oligonucleotide molecule is related to the mechanism for the antimicrobial susceptibility phenotype to the antimicrobial agent. <EOS>