Ertapenem microbiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sheng Shi, M.D. [2]

Microbiology[edit | edit source]

Gram-positive bacteria[edit | edit source]

• Staphylococcus aureus (methicillin susceptible isolates only)
• Streptococcus agalactiae
• Streptococcus pneumoniae (penicillin susceptible isolates only)
• Streptococcus pyogenes

Gram-negative bacteria[edit | edit source]

• Escherichia coli
• Haemophilus influenzae (beta-lactamase negative isolates only)
• Klebsiella pneumoniae
• Moraxella catarrhalis
• Proteus mirabilis

Anaerobic bacteria[edit | edit source]

• Bacteroides fragilis
• Bacteroides distasonis
• Bacteroides ovatus
• Bacteroides thetaiotaomicron
• Bacteroides uniformis
• Clostridium clostridioforme
• Eubacterium lentum
• Peptostreptococcus species
• Porphyromonas asaccharolytica
• Prevotella bivia

The following in vitro data are available, but their clinical significance is unknown. At least 90% of the following bacteria exhibit an in vitro minimum inhibitory concentration (MIC) less than or equal to the susceptible breakpoint for ertapenem. However, the efficacy of ertapenem in treating clinical infections due to these bacteria has not been established in adequate and well-controlled clinical trials:

Gram-positive bacteria[edit | edit source]

• Staphylococcus epidermidis (methicillin susceptible isolates only)
• Streptococcus pneumoniae (penicillin-intermediate isolates)

Gram-negative bacteria[edit | edit source]

• Citrobacter freundii
• Citrobacter koseri
• Enterobacter aerogenes
• Enterobacter cloacae
• Haemophilus influenzae (beta-lactamase positive isolates only)
• Haemophilus parainfluenzae
• Klebsiella oxytoca (excluding ESBL producing isolates)
• Morganella morganii
• Proteus vulgaris
• Providencia rettgeri
• Providencia stuartii
• Serratia marcescens

Anaerobic bacteria[edit | edit source]

• Bacteroides vulgatus
• Clostridium perfringens
• Fusobacterium spp.

Susceptibility Test Methods[edit | edit source]

When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility tests for antimicrobial drug products used in resident hospitals to the physician as periodic reports which describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting the most effective antimicrobial.

Dilution Techniques[edit | edit source]

Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized procedure. Standardized procedures are based on a broth dilution method or equivalent with standardized inoculum concentrations and standardized concentrations of ertapenem powder. The MIC values should be interpreted according to criteria provided in Table below and Table 4.

Diffusion Techniques[edit | edit source]

Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. One such standardized procedure requires the use of standardized inoculum concentrations. This procedure uses paper disks impregnated with 10-µg ertapenem to test the susceptibility of microorganisms to ertapenem. The disk diffusion interpretive criteria should be interpreted according to criteria provided in Table below and Table 4.

Anaerobic Techniques[edit | edit source]

For anaerobic bacteria, the susceptibility to ertapenem as MICs can be determined by standardized test methods. The MIC values obtained should be interpreted according to criteria provided in Table below and Table 4.

A report of "Susceptible" indicates that the pathogen is likely to be inhibited if the antimicrobial compound at the infection site reaches the concentrations usually achievable. A report of "Intermediate" indicates that the result should be considered equivocal, and, if the microorganism is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug is physiologically concentrated or in situations where high dosage of drug can be used. This category also provides a buffer zone which prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of "Resistant" indicates that the pathogen is not likely to be inhibited if the antimicrobial compound at the infection site reaches the concentrations usually achievable; other therapy should be selected.

Quality Control[edit | edit source]

Standardized susceptibility test procedures require the use of laboratory control microorganisms to ensure the accuracy and precision of supplies and reagents used in the assay, and the techniques of the individuals performing the test. Quality control microorganisms are specific strains of organisms with intrinsic biological properties. QC strains are very stable strains which will give a standard and repeatable susceptibility pattern. The specific strains used for microbiological quality control are not clinically significant. Standard ertapenem powder should provide the following range of values noted in Table 12.^[1]

References[edit | edit source]

Adapted from the FDA Package Insert.