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Letter
Antimicrobial Drug–resistant
Salmonella Typhimurium (Reply to Helms)
Read original article,
http://www.cdc.gov/ncidod/EID/vol8no5/01-0267.htm
Read Helm's reply,
http://www.cdc.gov/ncidod/EID/vol9no10/03-0029.htm
Jan Dahl*
*Danish Bacon and Meat Council, Copenhagen, Denmark
Suggested citation
for this article: Dahl J. Antimicrobial drug-resistant Salmonella
Typhimurium (reply to Helms). Emerg Infect Dis [serial online] 2003
Oct [date cited]. Available from: URL: http://www.cdc.gov/ncidod/EID/vol9no10/02-0716.htm
In Reply to Helms: In the article by Helms et al., Helms concludes
that infections with Salmonella Typhimurium strains resistant to
ampicillin, chloramphenicol, streptomycin, sulfonamide, and tetracycline
(hereafter referred to as penta-resistant) were associated with higher
death rates than infections with non–penta-resistant S. Typhimurium.
Helms also concluded that infections with quinolone-resistant (nalidixine-resistant)
S. Typhimurium were associated with higher death rates than quinolone-susceptible
S. Typhimurium (1).
Table 2 in Helms’ article
provides information that enables close scrutiny of this conclusion and
comparison of the excess mortality associated with penta-resistant, quinolone-susceptible
S. Typhimurium with the excess mortality of non–penta-resistant
S. Typhimurium (1). In this letter, the Table
is based on the original table. However, two additional comparisons have
been added: the p values, which are not based on the data but are approximations
based on the parameters in the table.
The conclusion is that only quinolone resistance is associated with excess
mortality compared with nonresistant isolates. Penta-resistant, quinolone-susceptible
S. Typhimurium has a risk ratio of 2.9 (1.1 to 7.9) compared to
the ratio of non–penta-resistant isolates 2.1 (1.5 to 2.9). When these
figures are compared, the approximate p value is 0.55, which, of course,
is far from being significant. Thus, on the basis of the article by Helms,
penta resistance may not pose a greater threat to human health than non–penta
resistance. However, the measured effect of penta resistance is achieved
by the inclusion of quinolone-resistant S. Typhimurium in the group.
Reference
- Helms M, Vastrup P, Gerner-Smidt P, Mølbak K. Excess
mortality associated with antimicrobial drug-resistant Salmonella
Typhimurium. Emerg Infect Dis 2002;8:490–5.
| Table.
Table showing additional comparisons (1)a |
|
| |
Resistant
|
Susceptible
|
p value
|
|
|
|
Deaths/cases
|
RRb (95% CI)
|
Deaths/cases
|
RRb (95 % CI)
|
|
|
Penta with and without quinolone
|
12/283
|
4.8 (2.2 to 10.5)
|
47/1,764
|
2.1 (1.5 to 2.9)
|
0.06
|
|
Penta with quinolone
|
5/40
|
13.1 (3.3 to 51.9)
|
47/1,764
|
2.1 (1.5 to 2.9)c
|
0.01d
|
|
Penta without quinolone
|
7/243
|
2.9 (1.1 to 7.9)
|
47/1764
|
2.1 (1.5 to 2.9)c
|
0.55cd
|
|
| aRR, relative risk;
CI, confidence interval. |
| bAdjusted for coexisting
conditions. |
| cCompared to the
non-penta group. |
| dApproximations
based on the parameters from the table. |
|
