| Date | November 2010 | Marks available | 1 | Reference code | 10N.3.SL.TZ0.16 |
| Level | Standard level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Suggest | Question number | 16 | Adapted from | N/A |
Question
Antibiotics are sometimes given orally to poultry to prevent disease that may lead to reduced growth. Antibiotic resistance of bacteria from turkeys and chickens bred for meat and from egg laying hens was measured.
Excrement was collected and Escherichia coli bacteria were isolated. These bacteria were tested for resistance to a range of antibiotics and the results are shown below.
Calculate the percentage risk of bacteria becoming resistant to more than five kinds of antibiotics in turkeys and egg laying hens.
Turkeys:
Egg laying hens:
Compare the incidence of drug resistance in bacteria from chickens and egg laying hens.
Discuss the hypothesis that giving antibiotics increases antibiotic resistance in poultry bacteria.
Suggest how antibiotic-resistant bacteria are passed from animals to humans.
Markscheme
turkeys: 33/32.6/32.56 %
egg laying hens: 0 %
Both needed to award the mark.
a. none of the egg laying hens have bacteria resistant to 5 or more antibiotics while (10) chickens have bacteria resistant to 5 or more antibiotics;
b. 13/65 % of the egg laying hens have no resistant bacteria while 9/20 % of the chickens have no resistant bacteria;
c. both have approximately same percentage/number of E. coli resistant to 1 or 3 antibiotics;
d. egg laying hens have less incidence of antibiotic-resistant bacteria than chickens;
a. hypothesis supported for poultry raised for meat but not for egg-laying;
b. turkeys and chickens always have bacteria resistant to more antibiotics than egg laying hens;
c. antibiotic-resistant bacteria are still found in egg laying hens even though antibiotics are rarely given;
d. antibiotic-resistant strains (of bacteria) may have arisen by other means/other than by poultry being given oral antibiotics;
from fecal matter to man handling the chickens / by accidental hand to mouth contact / contaminated dust / eating raw meat;
Examiners report
The few candidates who attempted this option struggled with this data analysis question. There was quite a bit of confusion about the poultry being resistant to bacteria rather than the bacteria found in the poultry being drug resistant. This caused problems in all parts of this question except (a).
Few received more than 1 mark for this section. The only point that was made was that egg-laying hens had a lower incidence of antibiotic-resistance bacteria than chickens.
Inability to understand what the table indicated meant that few were able to discuss the hypothesis given.
Many were able to get the 1 mark here for accidental contaminated hand to mouth contact. Those who indicated humans received the bacteria from animals when eating meat did not mention this was caused from raw meat.
