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Understanding antibiotic resistance
Understanding antibiotic resistance

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3.1 Intrinsic resistance to cephalosporins

Several bacteria are intrinsically resistant to cephalosporins. As a result, infections caused by these bacteria cannot be treated with cephalosporins. Some of these intrinsically resistant bacteria are summarised in Table 1.

Table 1 Bacteria intrinsically resistant to cephalosporins
TypeInfectious diseaseResistance mechanism (Cox and Wright, 2013)Resistance
Pseudomonas aeruginosaNosocomial infections including pneumonia, urinary tract infections and bacteraemiaExpresses cephalosporinase which deactivates cephalosporins Resistant to 1st and 2nd generation cephalosporins*
Enterococci spp.Urinary tract infections, bacteraemia, bacterial endocarditis, diverticulitis and meningitis Expresses a modified antibiotic target (PBP) that binds to β-lactams poorly Resistant to 1st and 2nd generation cephalosporins. Some resistance to 3rd generation cephalosporins*
Listeria monocytogenesListeriosisExpresses a modified antibiotic target (PBP) that binds to cephalosporins poorly Resistant to 1st, 2nd and 3rd generation cephalosporins*


* you will learn more about different generations of cephalosporins in Week 6

While intrinsic resistance limits the treatment options for infections caused by these pathogens, a greater concern is cephalosporin resistance being acquired by other intrinsically susceptible bacterial types. Some of these bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), are of huge clinical importance.

The massive use of cephalosporin antibiotics to treat infections has led to the emergence of these bacteria, as you will see in the case studies in Weeks 4 and 5. But next you will look at the mechanisms of resistance to cephalosporins.