[8] Infrequent adverse effects include fever, vomiting, erythema, dermatitis, angioedema, pseudomembranous colitis.

Rarely, allergic reactions have been triggered by exposure from kissing and sexual contact with a partner who is taking these antibiotics.

[citation needed] β-Lactam antibiotics are bactericidal, and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls.

The final transpeptidation step in the synthesis of the peptidoglycan is facilitated by DD-transpeptidases, also known as penicillin binding proteins (PBPs).

[11] β-Lactam antibiotics are analogues of d-alanyl-d-alanine—the terminal amino acid residues on the precursor NAM/NAG-peptide subunits of the nascent peptidoglycan layer.

This irreversible inhibition of the PBPs prevents the final crosslinking (transpeptidation) of the nascent peptidoglycan layer, disrupting cell wall synthesis.

Bacterial cytotoxicity could arise from incomplete repair of closely spaced 8-oxo-2'-deoxyguanosine lesions in the DNA resulting in double-strand breaks.

[citation needed] The production of a β-lactamase by a bacterium does not necessarily rule out all treatment options with β-lactam antibiotics.

For example, Augmentin (FGP) is made of amoxicillin (a β-lactam antibiotic) and clavulanic acid (a β-lactamase inhibitor).

Another β-lactam/β-lactamase inhibitor combination is piperacillin/tazobactam with a broad spectrum of antibacterial activity that includes gram-positive and -negative aerobic and anaerobic bacteria.

[21] However, in all cases where infection with β-lactamase-producing bacteria is suspected, the choice of a suitable β-lactam antibiotic should be carefully considered prior to treatment.

In particular, choosing appropriate β-lactam antibiotic therapy is of utmost importance against organisms which harbor some level of β-lactamase expression.

[27][28] This color change is a visual indicator of the presence and activity of β-lactamase enzymes, which are responsible for conferring resistance to β-lactam antibiotics in many bacterial species.

[29] For ceftriaxone, the color of solutions can range from light yellow to amber, depending on the length of storage, concentration, and diluent used.

[29] As a response to the use of β-lactams to control bacterial infections, some bacteria have evolved penicillin binding proteins with novel structures.

Notable examples of this mode of resistance include methicillin-resistant Staphylococcus aureus (MRSA)[32] and penicillin-resistant Streptococcus pneumoniae.

[33] By convention, the bicyclic β-lactams are numbered starting with the position occupied by sulfur in the penams and cephems, regardless of which atom it is in a given class.

[citation needed] The numbering of monobactams follows that of the IUPAC; the nitrogen atom is position 1, the carbonyl carbon is 2, the α-carbon is 3, and the β-carbon 4.