Microbiology: Loracarbef exerts its bactericidal action by binding to essential target proteins of the bacterial cell wall, leading to inhibition of cell-wall synthesis. It is stable in the presence of some bacterial b-lactamases. Loracarbef has been shown to be active against most strains of the following organisms both in vitro and in clinical infections (see INDICATIONS AND USAGE).

Gram-positive aerobes:

Staphylococcus aureus(including penicillinase-producing strains)

Staphylococcus saprophyticus
Streptococcus pneumoniae
Streptococcus pyogenes

Gram-negative aerobes:

Escherichia coli
Haemophilus influenzae (including b-lactamase-producing strains)
Moraxella (Branhamella) catarrhalis (including b-lactamase-producing strains)

The following in vitro data are available; however, their clinical significance is unknown.

Loracarbef exhibits in vitro minimum inhibitory concentrations (MIC) of 8 mcg/ml or less against most strains of the following organisms; however, the safety and efficacy of loracarbef in treating clinical infections due to these organisms have not been established in adequate and well-controlled trials.

Gram-positive aerobes:

Staphylococcus epidermidis
Streptococcus agalactiae (group B streptococci)
Streptococcus bovis
Streptococci groups C, F, and Gy
viridans group streptococci

Gram-negative aerobes:

Citrobacter diversus
Haemophilus parainfluenzae
Klebsiella pneumoniae
Neisseria gonorrhoeae (including penicillinase-producing strains)
Pasteurella multocida
Proteus mirabilis
Salmonella species
Shigella species
Yersinia enterocolitica

NOTE: Loracarbef is inactive against most strains of Acinetobacter, Enterobacter, Morganella morganii, Proteus vulgaris, Providencia, Pseudomonas, and Serratia.

Anaerobic organisms:

Clostridium perfringens
Fusobacterium necrophorum
Peptococcus niger
Peptostreptococcus intermedius
Propionibacterium acnes

Susceptibility Testing

Diffusion Techniques: Quantitative methods that require measurement of zone diameters give the most precise estimate of the susceptibility of bacteria to antimicrobial agents. One such standardized method¹ has been recommended for use with the 30-mcg loracarbef disk. Interpretation involves the correlation of the diameter obtained in the disk test with MIC for loracarbef.

Reports from the laboratory giving results of the standard single-disk susceptibility test with a 30 mcg loracarbef disk should be interpreted according to the following criteria (TABLE 2).

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