Infectious Diseases II

ii.

Sensitivity and specificity

A/B - vancomycin resistance; Klebsiella pneumoniae carbapenemase [KPC] - carbapenem

resistance)

iii.

Application: Earlier escalation or de-escalation of antimicrobial agents

iv.

Studies have shown an earlier time to pathogen identification and antibiotic de-escalation. One

study found no difference in mortality, LOS, or cost when multiplex PCR was combined with

antibiotic stewardship.

Mechanism

Direct detection from positive blood culture medium using nanoparticle technology

ii.

Nucleic acid extraction and array hybridization

Most-developed commercially available product with resistance gene detection

Sensitivity and specificity: 93%–100%

of accuracy and decreased time to pathogen and resistance mechanism identification. Limited

clinical evidence; however, two small single-center studies have evaluated the use of Nanosphere

technology to augment clinical decisions. These studies showed a decrease in time to appropriate

antibiotic, in addition to decreased LOS and overall cost.

Mechanism

Microbiological media used to identify different microorganisms by color production

ii.

Growth media use enzyme substrates that release colored dyes on hydrolysis, with a wide

range of enzymes that can be targeted

iii.

Potential advantage of being able to detect polymicrobial growth

Sensitivity and specificity: 95%–100%

Limitations

Many different companies make different chromogenic agar media (Brilliance, chromID,

CHROMagar). Slight differences in sensitivity and specificity were seen in studies; however,

all were within acceptable ranges.

ii.

Time to identification is longer than with other rapid diagnostic tests.

iii.

Different manufacturers’ chromogenic agar produces different colors for positive identification.

Readers of chromogenic agar should be sufficiently trained and familiar with the product used

by the local institution.

Isolation of S. aureus from other Staphylococcus spp.

ii.

Detection of methicillin resistance among S. aureus

iii.

Detection of vancomycin resistance

iv.

Detection of specific Enterobacterales: Salmonella, E. coli O157, extended-spectrum

β-lactamase (ESBL) production

Differentiation of different Candida spp.

vi.

Detection of KPC

Studies: Many clinical studies have shown significant advantages over conventional culture media.

With the advent of newer technology and shorter detection times, the clinical applicability of

chromogenic media may be limited. However, few microbiology laboratories have implemented

rapid diagnostic methods because of the considerable upfront costs. Centers where chromogenic

media are being used may continue to rely on this technology.