Chemical and Microbiologic Aspects of Penems, a Distinct Class of β-Lactams: Focus on Faropenem

Jeremy M. T. Hamilton-Miller, D.Sc., FRCPath

Pharmacotherapy. 2003;23(11)

Conclusion

The rapid advance in the development of penicillins and cephalosporins slowed in the mid-1970s, but β-lactams remain the most widely used class of antimicrobial agents. With the emergence of resistance to current antimicrobials, new therapies are sought that offer a long-term solution to the problem of emerging multidrug-resistant clinical isolates. Synthesizing new agents by combining the best features of known classes is an alternative strategy to optimizing the design of existing compounds, and β-lactam structures are versatile, lending themselves to further modifications.

The penems exhibit considerable advantages as a new class of β-lactams: they possess good antibacterial activity against the gram-positive and gram-negative pathogens commonly responsible for a wide range of community infections and are stable to β-lactamases. Developing new antimicrobials remains a challenge, and the penems offer a potential opportunity to meet this continuing need.

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Acknowledgments

The author thanks Chris Thompson for his assistance in preparing the manuscript.

Reprint Address

Address reprint requests to Jeremy M. T. Hamilton-Miller, D.Sc., FRCPath, Royal Free and University College London Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF, United Kingdom; e-mail: j.hamilton-miller@rfc.ucl.ac.uk.

Cite this: Chemical and Microbiologic Aspects of Penems, a Distinct Class of β-Lactams: Focus on Faropenem - Medscape - Nov 01, 2003.

Table 1. Activity of β-lactams Against Important Pathogens
Drug	Staphylococcus aureus ^a	Escherichia coli	Streptococcus pneumoniae ^b	Pseudomonas aeruginosa	Moraxella catarrhalis	Haemophilus influenzae
Faropenem	++	+	++++ (+)	-	++	+
Amoxicillin	+	-	++++ (+/-)	-	+++	+
Amoxicillin-clavulanate	+	+	++++ (+/-)	-	+++	+
Cefaclor	+/-	+/-	+ (-)	-	+	+/-
Ceftriaxone	+/-	++	+++ (-)	-	+	+++
Cefotaxime	+/-	++	+++ (-)	-	+	+++
Cefixime	-	+	++ (-)	-	+++	+++
Imipenem	+++	++	++++ (+)	+/-	++++	+/-

MIC₉₀ values: ++++ = 0.008-0.015 mg/L; +++ = 0.03-0.06 mg/L; ++ = 0.12-0.25 mg/L; + = 0.05-1.0 mg/L; +/- = 2-8 mg/L; - = 16-64 mg/L.^[19]
^aNot methicillin-resistant S. aureus.
^bPenicillin-resistant strains are shown in parentheses.

Table 2. In Vitro Activity of Faropenem Against Gram-Negative Bacteria ^[19]
Bacteria	No. of Isolates	MIC Range (mg/L)	MIC₅₀ (mg/L)	MIC₉₀ (mg/L)
Haemophilus influenzae (β-lactamase negative)	50	0.03-1	0.5	1
Haemophilus influenzae (β-lactamase positive)	20	0.056-1	0.5	1
Moraxella catarrhalis (β-lactamase negative)	50	0.015-0.5	0.06	0.5
Moraxella catarrhalis (β-lactamase positive)	20	≤ 0.0075-0.06	0.015	0.03
Escherichia coli (AMP^a ≤ 8)	30	0.13-1	0.25	1
Escherichia coli (AMP^a > 8)	58	0.5-2	1	1
Pseudomonas aeruginosa	50	128 to > 256	> 256	> 256
Salmonella sp	20	0.25-4	0.5	1
Shigella sp	22	0.5-1	0.5	1
Serratia sp	20	1-128	2	32
Stenotrophomonas maltophilia	10	128 to > 128	> 128	> 128
Neisseria gonorrhoeae	35	0.008-0.25	0.03	0.06
Neisseria meningitidis	10	0.008	0.008	0.008

MIC = minimum inhibitory concentration; MIC_{50, 90} = MIC for 50% and 90%, respectively, of tested strains.
^aMIC₉₀ for ampicillin.

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Chemical and Microbiologic Aspects of Penems, a Distinct Class of β-Lactams: Focus on Faropenem

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