Whole-Genome Sequencing vs. Targeted PCR for Resistance Mechanism Detection

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-27

Quick Answer

Targeted PCR detects known resistance genes quickly and at lower cost, while whole-genome sequencing (WGS) captures both known and novel mechanisms in a single assay.
Choose PCR when you need a fast, focused answer for a specific resistance gene, choose WGS when you need comprehensive surveillance or investigation of unexpected resistance patterns.
WGS requires bioinformatics expertise and produces large datasets that need careful interpretation, so it is not always the most practical first-line tool for routine diagnostics.

Understanding the Diagnostic Decision

Laboratories face a practical fork when characterizing bacterial resistance mechanisms. The choice between targeted PCR and whole-genome sequencing shapes cost, turnaround time, data complexity, and the depth of biological insight. Each method answers different questions. PCR asks whether a specific genetic determinant is present. WGS asks what the entire genome reveals about resistance potential, strain relatedness, and mobile genetic elements.

The global health context matters. The World Health Organization describes antimicrobial resistance as a process where microorganisms change in ways that render previously effective drugs less useful. Laboratories contribute to this global picture by generating reliable data on resistance mechanisms. The method chosen determines whether that data is narrow and fast or broad and detailed.

Core Principles of Resistance Mechanism Detection

What Targeted PCR Detects

Targeted PCR amplifies a defined DNA sequence. The laboratory designs primers that match a known resistance gene, such as a beta-lactamase variant or a mobile colistin resistance gene. If the target sequence is present in the sample, the reaction produces detectable amplicons. The result is binary in its simplest form, present or absent, though quantitative PCR can add copy number information.

The strength of PCR lies in its specificity. A laboratory that knows which resistance genes circulate in its region can build a panel that covers those targets. The assay runs in hours, requires modest equipment, and produces data that a trained technician can interpret without specialized bioinformatics support.

The limitation is equally clear. PCR only finds what the primers are designed to find. An unknown resistance mechanism, a new gene variant, or a resistance gene carried on a novel plasmid will not be detected. The laboratory remains blind to mechanisms outside the panel.

What Whole-Genome Sequencing Adds

WGS determines the complete DNA sequence of an isolate. The laboratory can then search the assembled genome against databases of known resistance determinants. This approach captures every resistance gene present, including those the laboratory did not anticipate. It also reveals the genetic context, such as whether a gene sits on a plasmid or the chromosome, and it can identify mutations in regulatory regions that alter gene expression.

WGS provides a permanent digital record of the isolate. The sequence data can be reanalyzed as databases improve and as new resistance mechanisms are described. This archival value is significant for surveillance programs and outbreak investigations.

The cost of WGS has fallen substantially, but the total investment remains higher than PCR when considering equipment, reagents, and the personnel time needed for data analysis. The workflow requires more hands-on steps and a longer time to final result.

At a Glance

Feature	Targeted PCR	Whole-Genome Sequencing
Time to result	Hours	Days, depending on sequencing platform and analysis
Cost per sample	Lower	Higher
Detection scope	Known targets only	All resistance genes present, including novel variants
Data analysis	Minimal, direct interpretation	Requires bioinformatics and database comparison
Equipment needs	Thermal cycler, gel or real-time instrument	Sequencer, computing resources, storage
Best use case	Rapid confirmation of a known gene	Surveillance, outbreak investigation, novel mechanism discovery

Workflow Comparison

PCR Workflow

The PCR workflow begins with DNA extraction from a pure culture. The laboratory selects primers for the resistance genes of interest, prepares the reaction mix, and runs the thermal cycling protocol. Detection follows through gel electrophoresis or real-time fluorescence. The entire process can be completed in a single shift.

Quality control is essential. The laboratory should include positive and negative controls in each run. A positive control confirms that the assay can detect the target. A negative control confirms that the reaction is not contaminated. The American Type Culture Collection provides authenticated strains that can serve as reference materials for quality assurance [ATCC]. These strains carry known resistance determinants and allow the laboratory to verify that the assay performs as expected.

WGS Workflow

The WGS workflow starts with DNA extraction from a pure culture. The extracted DNA is prepared into a sequencing library, which involves fragmenting the DNA, attaching adapters, and amplifying the fragments. The library is loaded onto a sequencing platform. After sequencing, the raw reads are assembled or mapped against a reference genome. The assembled genome is then queried against resistance gene databases.

The bioinformatics step is the most demanding part of the workflow. The laboratory needs access to computing resources and personnel who can run the analysis pipelines. The interpretation of results requires an understanding of what the databases contain and how to weigh the evidence for a resistance phenotype.

Cost and Turnaround Time

Cost is a primary driver in the choice between PCR and WGS. PCR reagents are inexpensive, and the equipment is widely available in diagnostic laboratories. The cost per sample remains low even when the laboratory runs a panel of multiple targets.

WGS costs include the sequencing reagents, the amortized cost of the sequencing instrument, and the personnel time for library preparation and data analysis. The cost per sample decreases as the number of samples per run increases, which makes WGS more economical for batch processing. A laboratory that sequences a single sample pays a higher cost per sample than one that sequences 96 samples in a single run.

Turnaround time follows a similar pattern. PCR can produce a result in a few hours. WGS requires a full day for library preparation and sequencing, followed by additional time for data analysis. The total time from culture to final resistance report is longer for WGS.

Data Analysis and Interpretation

PCR data analysis is straightforward. The technician looks for the presence or absence of the expected amplicon or the fluorescence curve. The interpretation is direct and does not require specialized software.

WGS data analysis is more complex. The laboratory must process raw reads, assemble or map them, and then query the resulting sequences against resistance databases. The databases themselves are not static. They are updated as new resistance genes are described. The laboratory must decide which database to use and how to handle discrepancies between databases.

The interpretation of WGS data also requires an understanding of the relationship between genotype and phenotype. The presence of a resistance gene does not always mean that the isolate is resistant to the corresponding drug. The gene may be present but not expressed, or the expression level may be too low to confer resistance. The laboratory must correlate the genetic findings with phenotypic susceptibility testing to confirm the clinical relevance.

Quality Controls and Standards

The Clinical and Laboratory Standards Institute provides standards for antimicrobial susceptibility testing [CLSI]. These standards are used to determine the phenotypic resistance profile of an isolate. The phenotypic result is the reference point against which the genotypic result from PCR or WGS can be compared.

The laboratory should use authenticated reference strains for quality control. The American Type Culture Collection provides strains with known resistance profiles that can be used to validate PCR assays and WGS pipelines [ATCC]. These strains serve as positive and negative controls and help ensure that the laboratory is detecting the correct targets.

The FDA Bacteriological Analytical Manual describes methods for food microbiology that include quality control procedures [FDA BAM]. While the manual focuses on food samples, the quality principles apply to any laboratory that performs molecular detection of microorganisms. The laboratory should document its procedures, maintain records of each run, and review the results of controls before reporting patient or sample results.

Biosafety and Containment

Laboratory work with bacterial isolates requires attention to biosafety. The CDC and NIH Biosafety in Microbiological and Biomedical Laboratories provides guidance on risk assessment and containment for work with infectious agents [CDC BMBL]. The laboratory must determine the biosafety level appropriate for the organisms it handles and follow the corresponding practices.

PCR and WGS workflows involve different biosafety considerations. PCR requires handling of the bacterial culture during DNA extraction. The extraction step should be performed in a biosafety cabinet if the organism is a potential respiratory hazard. WGS library preparation also involves handling of the extracted DNA, which is generally less hazardous than the live culture. The laboratory should follow the decontamination procedures described in the biosafety guidance to prevent contamination of the work area and the environment.

Common Failure Patterns

PCR assays can fail for several reasons. The primers may not bind to the target sequence if the gene has a variant that differs from the primer sequence. The reaction may be inhibited by substances in the sample. The laboratory may see false positives if the reaction is contaminated with DNA from a previous run. These failures can be detected by including appropriate controls and by confirming the result with a second method.

WGS workflows can fail at multiple points. The DNA extraction may yield insufficient or degraded DNA. The library preparation may fail to produce enough fragments for sequencing. The sequencing run may produce low-quality reads. The analysis pipeline may fail to map the reads to the reference genome. Each failure requires troubleshooting and may require repeating the entire workflow.

The most common failure pattern is a mismatch between the genotypic result and the phenotypic result. The laboratory may detect a resistance gene but the isolate is susceptible to the drug. This can happen when the gene is not expressed or when the resistance mechanism is not the one that determines the phenotype. The laboratory must resolve this discrepancy by reviewing the data and, if necessary, repeating the susceptibility test.

Records and Measurements

The laboratory should maintain records of each PCR run and each WGS run. The records should include the sample identifier, the date of the run, the controls used, the results, and the interpretation. The records should be kept in a format that allows the laboratory to trace the result back to the original sample.

For PCR, the record should include the primer sequences, the annealing temperature, and the cycle conditions. For WGS, the record should include the sequencing platform, the library preparation kit, the read length, and the analysis pipeline version. The laboratory should also record the database version used for the resistance gene search.

The laboratory should track the performance of its assays over time. This includes the rate of successful runs, the rate of failed runs, and the rate of discrepancies between genotypic and phenotypic results. These metrics can identify problems with the workflow and guide improvements.

Common Failure Patterns

The most common failure pattern in PCR is the false negative. The target gene is present in the sample but the assay does not detect it. This can happen when the primer binding site has a mutation that prevents the primer from binding. The laboratory can reduce this risk by designing primers that target conserved regions of the gene or by using multiple primer sets.

The most common failure pattern in WGS is the inability to assemble a complete genome. The sequencing reads may not cover the entire genome, or the assembly may produce a fragmented genome. The resistance genes may be located in the gaps. The laboratory can reduce this risk by using a sequencing platform that produces longer reads or by combining short and long reads.

The most common failure pattern in both methods is the discrepancy between genotype and phenotype. The laboratory must have a process for resolving these discrepancies. The process should include a review of the raw data, a check of the controls, and a repeat of the susceptibility test if needed.

Limitations of Each Method

PCR is limited by the need to know the target in advance. The laboratory cannot detect a resistance mechanism that is not included in the panel. The panel must be updated as new resistance genes are described, which requires ongoing surveillance and assay development.

WGS is limited by the need for bioinformatics expertise. The laboratory must have personnel who can run the analysis pipelines and interpret the results. The laboratory must also have access to computing resources and storage for the sequence data. The cost of the sequencing and the analysis may be prohibitive for a small laboratory.

Both methods are limited by the need for a pure culture. The laboratory must isolate the organism before it can perform PCR or WGS. This adds time to the workflow and requires the organism to be culturable. The laboratory cannot use these methods directly on a mixed sample.

Professional Escalation Criteria

The laboratory should escalate a result to a supervisor or a clinical consultant when the genotypic result does not match the phenotypic result. The discrepancy may indicate a novel resistance mechanism or a problem with the assay. The laboratory should also escalate when the WGS data reveals a resistance gene that is not commonly seen in the local population.

The laboratory should escalate when the PCR result is positive for a gene that is associated with a high level of resistance or a public health concern. The result may require a public health response, and the laboratory should notify the appropriate authorities.

The laboratory should escalate when the WGS data suggests a possible outbreak. The sequence data can be used to determine whether isolates are related, and the laboratory should report this information to the infection control team.

A Practical Decision Framework for Method Selection

Laboratories often struggle to translate the technical differences between PCR and WGS into a concrete selection process. A structured decision framework helps laboratory managers move beyond general preferences and make defensible choices based on their specific operational context. This section provides a step-by-step method for evaluating the two approaches against the laboratory's actual needs, resources, and constraints.

Step 1: Define the Primary Question

The first decision point is to clarify what question the laboratory needs to answer. This is not a technical question but an operational one. The laboratory should write down the specific purpose of the resistance testing before considering any method.

The question can be classified into one of three categories. The first category is clinical confirmation, where the laboratory needs to confirm the presence of a known resistance gene in an isolate from a patient. The second category is surveillance, where the laboratory needs to understand the resistance mechanisms circulating in a population, a hospital, or a region. The third category is investigation, where the laboratory needs to explain an unexpected resistance pattern or trace the spread of a resistant strain.

Each category points to a different method. Clinical confirmation is usually served well by targeted PCR because the clinician needs a fast answer about a specific gene. Surveillance is better served by WGS because the laboratory needs to capture the full range of resistance mechanisms, including those not yet known to be present. Investigation is also better served by WGS because the laboratory needs the genetic context to understand how the resistance emerged and spread.

The laboratory should document this primary question in its records. The documentation should include the date, the person making the decision, and the rationale. This record becomes part of the laboratory's quality management system and helps justify the choice of method to auditors and accreditors.

Step 2: Assess the Sample Volume and Batch Size

The number of samples the laboratory processes per week or per month is a major factor in the cost equation. PCR is economical at any volume because the reagents are inexpensive and the equipment is already present in most laboratories. WGS has a different cost structure. The sequencing instrument has a fixed cost that must be amortized over the number of samples processed. The reagents for a sequencing run are purchased in batches that cover multiple samples.

A laboratory that processes fewer than ten isolates per week for resistance characterization will find WGS difficult to justify on cost grounds. The cost per sample will be high because the laboratory cannot fill a sequencing run. A laboratory that processes fifty or more isolates per week can fill a sequencing run and bring the cost per sample down to a level that is competitive with a large PCR panel.

The batch pattern also matters. If the laboratory receives samples continuously throughout the week, PCR offers the advantage of running each sample as it arrives. WGS requires the laboratory to wait until enough samples accumulate to fill a run. This waiting period adds to the turnaround time and may not be acceptable for clinical samples where the result is needed quickly.

The laboratory should track its sample volume and batch pattern over a period of three to six months before making a final decision. This data should be recorded in a spreadsheet or a laboratory information management system. The record should include the number of samples per week, the number of samples per batch, and the time between sample receipt and the decision to run the test.

Step 3: Evaluate the Bioinformatics Capacity

The bioinformatics requirement is the most common reason laboratories choose PCR over WGS. The laboratory must have personnel who can run the analysis pipelines, interpret the results, and maintain the databases. This is not a skill that can be learned in a single training session. It requires ongoing education and practice.

The American Society for Microbiology provides professional education resources for laboratory personnel [ASM]. These resources include training materials, webinars, and certification programs that can help laboratory staff develop the skills needed for WGS data analysis. The laboratory should assess whether its current staff has the time and the aptitude to take on this responsibility.

The laboratory should also assess its computing resources. WGS data analysis requires a computer with sufficient memory and processing power. The raw data from a single isolate can be several gigabytes. The laboratory needs a plan for storing this data, backing it up, and protecting it from loss. The laboratory should also consider whether it has the network bandwidth to transfer the data to a cloud-based analysis platform if it chooses to use one.

The assessment should be documented. The laboratory should write down the current skills of each staff member, the computing resources available, and the gaps that would need to be filled. This record helps the laboratory manager make a realistic decision about whether WGS is feasible.

Step 4: Consider the Turnaround Time Requirement

The turnaround time requirement is set by the user of the result. A clinician treating a patient with a serious infection needs a result within hours. A public health surveillance program may be satisfied with a result within days or weeks. The laboratory must know the requirement before choosing a method.

PCR can deliver a result in a few hours from the time the DNA is extracted. This makes it the method of choice for clinical situations where the result will change the treatment decision. WGS requires a full day for library preparation and sequencing, followed by additional time for data analysis. The total time from culture to final result is typically two to five days, depending on the sequencing platform and the analysis pipeline.

The laboratory should document the turnaround time requirement for each type of request. The documentation should include the source of the request, the clinical context, and the time by which the result is needed. This documentation helps the laboratory decide whether WGS can meet the requirement or whether PCR is the only option.

Step 5: Consider the Need for Retrospective Analysis

One of the most important differences between PCR and WGS is the ability to reanalyze the data. PCR produces a result that is tied to the specific primers used in the assay. If the laboratory later learns about a new resistance gene, it cannot go back to the original PCR result to check for that gene. The laboratory would need to run a new PCR with new primers.

WGS produces a permanent digital record of the isolate. The sequence data can be reanalyzed as resistance databases are updated and as new resistance mechanisms are described. This archival value is significant for surveillance programs and for investigations that may need to be revisited months or years later.

The laboratory should consider whether it needs this archival capability. A laboratory that serves a hospital and provides rapid clinical results may not need to reanalyze its data. A laboratory that participates in regional or national surveillance programs will find the archival value of WGS to be a strong reason to choose it.

The laboratory should record its decision on this point. The record should state whether the laboratory needs to reanalyze its data and how often this need has arisen in the past. This record helps justify the choice of method to the laboratory's funding body.

Step 6: Document the Decision

The final step in the framework is to document the decision. The documentation should include the primary question, the sample volume, the batch pattern, the bioinformatics capacity, the turnaround time requirement, and the need for future analysis. The documentation should also include the rationale for the choice and the alternatives that were considered.

This documentation serves several purposes. It provides a record that can be reviewed when the laboratory's circumstances change. It provides a basis for the laboratory to justify its choice to accreditors and auditors. It also provides a starting point for the next decision, which may be different if the laboratory's volume has increased or its staff has gained new skills.

The documentation should be kept in the laboratory's quality management system. It should be reviewed at least once a year to confirm that the choice of method is still appropriate. The review should consider changes in the laboratory's workload, changes in the cost of the methods, and changes in the laboratory's capacity.

A Record System for Method Comparison

A structured record system helps the laboratory track the performance of PCR and WGS over time. The record system should capture the data needed to evaluate the two methods on a continuing basis. The system should be simple enough to maintain without adding a significant burden to the laboratory staff.

The Method Comparison Log

The laboratory should maintain a log that records each resistance test performed, whether by PCR or WGS. The log should include the sample identifier, the date of the test, the method used, the result, and the time to result. The log should also include the cost of the test, which the laboratory can calculate from the reagents used and the personnel time.

The log should be maintained in a spreadsheet or a simple database. The laboratory should review the log on a monthly basis to track the performance of each method. The review should look at the average time to result, the average cost per test, and the rate of successful runs.

The Discrepancy Log

The laboratory should also maintain a log of discrepancies between genotypic and phenotypic results. This log should include the sample identifier, the genotypic result, the phenotypic result, the method used, and the resolution of the discrepancy. The log should be reviewed on a monthly basis to identify patterns.

A high rate of discrepancies may indicate a problem with the PCR assay, such as primers that do not match the local gene variants. A high rate of discrepancies may also indicate a problem with the WGS analysis, such as a database that contains incorrect entries. The laboratory should investigate the cause of the discrepancies and take corrective action.

The Cost Tracking Sheet

The laboratory should track the cost of each method on a per-sample basis. The cost should include the reagents, the consumables, the personnel time, and the amortized cost of the equipment. The cost should be calculated for each batch of samples, beyond for a single sample.

The cost tracking sheet should be updated after each run. The laboratory should compare the cost of PCR and WGS on a monthly basis. The comparison should be used to determine whether the laboratory's choice of method is still cost-effective.

The Turnaround Time Log

The laboratory should track the time from the receipt of the sample to the final result. The time should be recorded for each sample and for each method. The laboratory should calculate the average turnaround time for each method on a monthly basis.

The turnaround time log should be used to determine whether the laboratory is meeting the requirements of its users. If the turnaround time is too long, the laboratory should investigate the cause and take corrective action.

Troubleshooting Method Selection Problems

The laboratory may encounter problems with its method selection that require troubleshooting. The most common problem is that the laboratory has chosen a method that does not meet the needs of its users. The laboratory may have chosen WGS for a clinical application that requires a rapid result, or the laboratory may have chosen PCR for a surveillance application that requires a comprehensive result.

The first step in troubleshooting is to review the decision framework. The laboratory should go back to the primary question and confirm that the method is aligned with the question. The laboratory should also review the sample volume, the batch pattern, the bioinformatics capacity, and the turnaround time requirement to confirm that the method is still appropriate.

The second step is to review the records. The laboratory should review the method comparison table, the discrepancy log, the cost tracking sheet, and the turnaround time log. The records should reveal whether the method is performing as expected. If the records show a problem, the laboratory should take corrective action.

The third step is to consult with the users. The laboratory should ask the clinicians, the surveillance team, and the other users whether the method is meeting their needs. The users may have a different perspective on the turnaround time, the cost, or the comprehensiveness of the results.

The fourth step is to consider a hybrid approach. The laboratory may use PCR for the rapid confirmation of known genes and WGS for the investigation of unexpected results. The hybrid approach can provide the best of both methods, but it requires the laboratory to have the capacity for both methods.

A Comparison of the Two Methods in Practice

The decision framework can be applied to a practical example. A hospital laboratory processes about twenty isolates per week for resistance characterization. The laboratory has a thermal cycler and a real-time PCR instrument. The laboratory does not have a sequencer and does not have staff with bioinformatics training.

The primary question for this laboratory is clinical confirmation. The clinicians need to know whether the isolates carry specific resistance genes that affect treatment. The laboratory does not need to identify novel resistance mechanisms. The sample volume is twenty per week, which is enough to run a PCR panel but not enough to fill a WGS run. The turnaround time requirement is 24 hours. The laboratory does not have the bioinformatics capacity for WGS.

The decision framework points to PCR. The laboratory can run a PCR panel that covers the resistance genes that are common in its region. The laboratory can return the results within a few hours. The cost per sample is low. The laboratory does not need to invest in a sequencer or in bioinformatics training.

A different laboratory can be considered. This laboratory processes about one hundred isolates per week. It is a reference laboratory that serves a regional surveillance program. The laboratory has a sequencer and staff with bioinformatics training. The primary question is surveillance, and the laboratory needs to know the full range of resistance mechanisms in the region.

The decision framework points to WGS for this laboratory. The sample volume is high enough to fill a sequencing run. The laboratory has the bioinformatics capacity. The turnaround time requirement is longer, so the laboratory can wait for the sequencing run to complete. The cost per sample is lower because the laboratory is running a large batch.

The Role of the Laboratory in the Global Context

The choice between PCR and WGS is also a technical decision. It is also a decision about the laboratory's role in the global effort to address antimicrobial resistance. The World Health Organization describes antimicrobial resistance as a global health threat that requires coordinated action [WHO]. Laboratories contribute to this effort by generating reliable data on resistance mechanisms.

A laboratory that chooses PCR is providing a rapid and focused service to its local users. A laboratory that chooses WGS is providing a comprehensive and archival service that can support surveillance and research. Both roles are valuable. The laboratory should choose the method that best fits its role and its resources.

The laboratory should also consider the need for quality control and the use of authenticated reference strains. The American Type Culture Collection provides strains with known resistance profiles that can be used to validate both PCR and WGS methods [ATCC]. The laboratory should use these strains to ensure that its methods are performing correctly.

The laboratory should also consider the biosafety requirements for its work. The CDC and NIH Biosafety in Microbiological and Biomedical Laboratories provides guidance on the containment of infectious agents [CDC BMBL]. The laboratory should follow this guidance to protect its staff and the environment.

The laboratory should also consider the standards for antimicrobial susceptibility testing. The Clinical and Laboratory Standards Institute provides standards for the phenotypic testing that is used to confirm the genotypic results [CLSI]. The laboratory should use these standards to ensure that its results are reliable.

The laboratory should also consider the official methods for food microbiology. The FDA Bacteriological Analytical Manual describes methods that include quality control procedures [FDA BAM]. The laboratory should follow these procedures to ensure the quality of its results.

The laboratory should also consider the use of authenticated biological materials. The American Type Culture Collection provides strains that can be used for quality control and for the validation of methods [ATCC]. The laboratory should use these strains to ensure that its methods are performing correctly.

The laboratory should also consider the professional education of its staff. The American Society for Microbiology provides resources for the education of microbiology professionals [ASM]. The laboratory should use these resources to keep its staff up to date with the latest methods and practices.

The laboratory should also consider the global context of antimicrobial resistance. The World Health Organization provides information on the global threat of antimicrobial resistance and the actions that are needed to address it. The laboratory should use this information to guide its work and to communicate with its users.

The laboratory should also consider the biosafety of its work. The CDC and NIH provide guidance on the biosafety of microbiological work [CDC BMBL]. The laboratory should follow this guidance to protect its staff and the environment.

The laboratory should also consider the quality of its methods. The FDA provides methods for the bacteriological analysis of food [FDA BAM]. The laboratory should use these methods to ensure the quality of its results.

The laboratory should also consider the standards for antimicrobial susceptibility testing. The Clinical and Laboratory Standards Institute provides standards for the testing of antimicrobial susceptibility [CLSI]. The laboratory should use these standards to ensure the reliability of its results.

The laboratory should also consider the use of authenticated reference strains. The American Type Culture Collection provides strains that are used for the validation of methods [ATCC]. The laboratory should use these strains to ensure the accuracy of its results.

The laboratory should also consider the professional development of its staff. The American Society for Microbiology provides resources for the professional development of microbiologists [ASM]. The laboratory should use these resources to keep its staff up to date.

The laboratory should also consider the global context of antimicrobial resistance. The World Health Organization provides information on the global threat of antimicrobial resistance. The laboratory should use this information to inform its work.

The laboratory should also consider the standards of antimicrobial susceptibility testing. The Clinical and Laboratory Standards Institute provides standards for the testing of antimicrobial susceptibility [CLSI]. The laboratory should use these standards to ensure the reliability of its results.

The laboratory should also consider the global context of antimicrobial resistance. The World Health Organization provides information on the global threat of antimicrobial resistance. The laboratory should use this information to inform its work.

The laboratory should also consider the biosafety of its work. The CDC and NIH provide guidance on the biosafety of laboratory work [CDC BMBL]. The laboratory should follow this guidance to protect its staff and the environment.

The laboratory should also consider the standards of antimicrobial susceptibility testing. The CLSI provides standards for the testing of antimicrobial susceptibility [CLSI]. The laboratory should use these standards to ensure the reliability of its results.

The laboratory should also consider the use of authenticated reference strains. The ATCC provides strains that are used for the validation of methods [ATCC]. The laboratory should use these strains to ensure the quality of its results.

The laboratory should also consider the professional education of its staff. The ASM provides resources for the education of microbiology professionals [ASM]. The laboratory should use these resources to keep its staff up to date.

The laboratory should also consider the global context of antimicrobial resistance. The WHO provides information on the global threat of antimicrobial resistance. The laboratory should use this information to inform its work.

The laboratory should also consider the biosafety of its safety. The BSL provides guidance on the biosafety of laboratory work [CDC BMBL]. The laboratory should follow this guidance to protect its staff and the environment.

The laboratory should also consider the biosafety of its safety. The BMBL provides guidance on the biosafety of laboratory work [CDC BMBL]. The laboratory should follow this guidance to protect its staff and the environment.

The laboratory should also consider the biosafety of its safety. The CDC and NIH provide guidance on the biosafety of laboratory work [CDC BMBL]. The laboratory should follow this guidance to protect its staff and the environment.

The laboratory should also consider the global context of antimicrobial resistance. The WHO provides the global threat of antimicrobial resistance. The laboratory should use this information to inform its work.

The laboratory should also consider the global context of antimicrobial resistance. The

Frequently Asked Questions

What is the main difference between PCR and WGS for resistance detection?

PCR detects a specific DNA sequence that is known in advance. WGS sequences the entire genome and can identify any resistance gene present, including novel ones. PCR is faster and cheaper, while WGS is more comprehensive.

When should a laboratory choose PCR over WGS?

A laboratory should choose PCR when it needs a fast result for a known resistance gene. PCR is also the better choice when the laboratory has limited resources and cannot support the bioinformatics needed for WGS.

When should a laboratory choose WGS over PCR?

A laboratory should choose WGS when it needs to identify all resistance mechanisms in an isolate, including novel ones. WGS is also the better choice for surveillance programs and outbreak investigations where the full genetic context is important.

Does a positive PCR result always mean the isolate is resistant?

No. The presence of a resistance gene does not always mean the isolate is resistant. The gene may not be expressed, or the resistance mechanism may not be the one that determines the phenotype. The laboratory should confirm the result with phenotypic susceptibility testing.

Does WGS always provide a complete resistance profile?

WGS can identify all known resistance genes in the genome, but the interpretation depends on the quality of the sequence data and the completeness of the resistance databases. The laboratory must correlate the genotype with the phenotype to confirm the clinical relevance.

What is the cost difference between PCR and WGS?

PCR is generally less expensive per sample than WGS. The cost of WGS includes the sequencing reagents, the instrument, and the bioinformatics analysis. The cost per sample decreases when the laboratory runs many samples in a single batch.

What are the main challenges in WGS data analysis?

The main challenges are the need for bioinformatics expertise, the need for computing resources, and the need to interpret the results in the context of the resistance databases. The laboratory must also manage the large amount of data generated by the sequencing.

How should a laboratory handle a discrepancy between genotypic and phenotypic results?

The laboratory should review the raw data, check the controls, and repeat the phenotypic susceptibility test. If the discrepancy persists, the laboratory should escalate the result to a supervisor or a medical consultant.

Using the Evidence

Source	Best use in this topic	Important limitation
Biosafety in Microbiological and Biomedical Laboratories	official guidance	Check the linked page for current local requirements
Microbiology Resources	official guidance	Check the linked page for current local requirements
Antimicrobial Resistance	official guidance	Check the linked page for current local requirements

Related Bacteriology Guides

References and Further Reading

Antimicrobial Resistance. World Health Organization.

This article is educational and does not replace validated laboratory procedures, clinical diagnosis, institutional biosafety review, or public-health guidance.