Antimicrobial Chemotherapies

Assignment 2, 2014

Please be sure to appropriately reference the sources used
Enzymes are significant in the mode of action of antibiotics (as targets) and in the resistance of
bacteria to the action of antibiotics (as inactivating agents). In resistant cells there may be
differences in enzymes compared with sensitive cells or the expression of enzymes may be
different, These differences may be due to chromosomal changes (mutations; transposons) or to
genes on plasmids.
Q1. (a) Use the mechanisms of resistance to beta-lactams discussed in GG p.1479 (12œ
Ed “ online text via the library) to explain
i) The beta-Iactam resistance shown by S. aureus M908
ii) The beta-Iactam resistance shown by S. aureus CP11
[2 marks]
(b)How is the resistance shown by newly-emerging resistant gram-negative
organisms carrying the NDM-1 gene different to those discussed in 1 (a)?
[1 mark]
(c) Examine the data collected for the aminoglycoside activities against strains CP10
and CP11. DISCUSS the possible mechanism for the SmR in these strains from the
options set out in Goodman and Gilman. (Be concise and make it clear how you use
the data in reaching your conclusion. You are asked for one choice and the reason
for that choice instead of the others). [2 marks]

02. Describe the contribution of B-lactamases to the indirect pathogenicity of some
bacteria. [2 marks]
See Maddocks,JL. Indirect pathogenicity. Journal of Antimicrobial Chemotherapy
1980; 6: 307-309. Also an Addendum at page 807 in this volume.
Brook /. The concept of indirect pathogenicity by B-Iactamase production,
especially in ear, nose and throat infection. Journal of Antimicrobial Chemotherapy
1989; 24 Suppl. B: 63-72.
[These are the significant early papers on this concept. A more recent review is
available online from the library. Clin. Microbiol. Infect. 2004 Sep; 10(9): 777-84.]
AC220 Assignment 2 2013

Q3. (a)For most infections, monotherapy is preferred to combination therapy but
in some circumstances, combination therapy is warranted. Care must be taken when
combining antimicrobials because although there are advantages-there may also be
disadvantages. Use the results of the checkerboard titration of Ne/sserla gonorrhoea
and Proteus mirabilis obtained during session 11 to prepare a clearly labelled
isobologram. [0.5marks]
(b)Refer to GG p1103 to explain your isobologram results. [1.5 marks]
Q4. A consideration of the concept of antibiotic stewardship was first introduced into the
Antibiotic Guidelines in version 14 (p.7). Describe how the role of an œantibiotic
pharmacist contributes to antibiotic stewardship. [1 mark]

[Q4 will not be in textbooks and will need to be searched on-line.
Use at least two references]