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Key
words
Urinary tract infection, prophylaxis,
susceptibility, empiric treatment, Cotrimoxazole.,
Pseudomonas, E.coli.
Introduction
Urinary tract infections are very common, and
antibiotics are prescribed very frequently to treat
them. Very often this is done empirically without
sensitivity testing. As such, it’s quite important to
know about prevalent bacterial isolates and their
susceptibility patterns in a given area so we can decide
about the best empiric therapy. This will also help us
decide about which agent to use for prophylaxis against
UTI.
Cotrimoxazole is anti-bacterial, anti-protozoal and
anti-fungal. It occupies a central role in treatment of
various commonly encountered infections, particularly
urinary, as well as, upper and lower respiratory tract
infections. It’s also a key agent in the treatment of
and prophylaxis against Pneumocystis jiroveci (carinii)
infections. The other features include affordable price,
ease of administration, and high concentration in the
urinary tract.
However, the changing resistance patterns and
indiscriminate use of antibiotics in our area
necessitated a careful reevaluation of the position of
this agent in our clinical practice.
To our
knowledge no such study has
been conducted in the West Bank.
Materials and Methods
It came to our attention that the resistance to
Cotrimoxazole was unusually high in our urinary tract
isolates. So, we retrospectively studied the sensitivity
pattern of UTI isolates at Augusta Victoria Hospital
laboratory that were performed between the years 2000
and 2003. Analysis was restricted to
Cotrimoxazole
in this study.
Bacterial isolates were identified using routine
biochemical activities in cases of Gram-positive
bacteria. The predominant isolates, Gram-negative rods,
were identified using the API-20 system (BioMerieuxe).
All other reagents were purchased from Oxoid Limited.
Susceptibility testing was done using the Bauer-Kirby
method; the intermediate percentage was less than 5%
among all antibiotics, indicating an acceptable random
error according to this method.
The positive cultures were classified into two main
groups
1. In-Patient group (IP).
2. Out-Patient group (OP).
The IP group was subdivided into different subgroups:
a. Intensive care unit patients and sub-acute care
patients (ICU\SAC).
b. Pediatric patients (<14 year)
c. Male patients.
d. Female patients.
Sensitivity (# of sensitive cultures in group/ total
number of tested isolates) was calculated for all
groups. Chi-Square test was used for comparing different
groups.
Results
Data were obtained from Augusta Victoria
Hospital written records for the specified years. A
total of 4831 urine samples were tested for sensitivity,
1170 out of which showed positive bacterial growth for a
specific organism. Out of those positive cultures, 151
showed growth of Pseudomonas. Of the 151 specimens only
30 were tested for sensitivity to cotrimoxazole, and so
the remaining 121-pseudomonal growths were excluded from
the analysis. The remaining 1049 specimens were analyzed
for sensitivity to Cotrimoxazole.
The analysis of the isolates’ distribution showed
that E.coli was the main isolate. The overall
distribution is summarized in table 1.
The cultures studied showed that the overall sensitivity
to Cotrimoxazole was 33.7%; table 2 summarizes the
different sensitivity percentages in different groups.
We noticed variability in the distribution of the
isolates among the subgroups. Also there was a notable
variability among isolates in regards to their
sensitivity to Cotrimoxazole. E.coli showed notably high
resistance rates to Cotrimoxazole compared to the
others.
The results showed high incidence of Pseudomonal growths
most of which were not tested for sensitivity to
Cotrimoxazole. This will actually decrease the
sensitivity percentage, as Cotrimoxazole typically
doesn’t inhibit Pseudomonas or anaerobes (1).
Discussion
The results show that the sensitivity to cotrimoxazole
in UTI in our area is significantly lower than in
developed countries. In a study carried out in USA in
the year 2001 the sensitivity was 83.8% compared to
33.7% in our area (2). And this pattern of
lower-than-usual susceptibility was maintained even when
subgroup analysis was performed, e.g., when inpatients
were compared to outpatients, no significant difference
was seen (p=0.53). Upon running the Chi-square test on 2
X 4 contingency table that included the different
In-patient
subgroups, the probability value was 0.16 indicating
lack of difference between the four In-patient groups.
However, since the P value was considerably less than
that of the IN-OP comparison, we tested if this is a
result of significant difference between the “male”
subgroup, which has the highest sensitivity, and the
ICU/SAC, which has the lowest sensitivity, the result of
this comparison produced a probability value of 0.05
which indicated a marginal difference, however, this
difference was not enough to affect the homogeneity of
the
different In-patient's subgroups. Therefore it is safe
to deal with the pooled data as a homogenous sample.
Knowing the distribution of isolates, in a particular
area, is such important in deciding the empiric
treatment of UTI as this will affect the susceptibility
profile. In our study, the isolates’ distribution showed
a very different pattern from that seen in the developed
countries. While, the E.coli remained the most commonly
encountered pathogen, its prevalence in our area (41%)
was much less than that seen in developed countries
(75-95%) (2,3). On the other hand, it was close to the
figures in developing countries (35.6%).(4, 5, and 6).
Studies from developing countries showed high incidence
of pseudomonas (6.9%) but yet their figures were still
lower than that in our study (4, 5, and 6). This
different distribution may be, in part, due to
economical or environmental factors, like dietary
habits, or it may be due to uncontrolled use of
antibiotics in developing countries, however, more
research is needed to determine the precise causes (7).
We strongly recommend conducting more studies in the
future, both prospective and retrospective, and with
inclusion of more populations representative of the
community; like primary care facilities, and to assess
more antibiotics. These should help us select
appropriate agents for both empiric and prophylactic
therapy. Typically the sensitivity for such an agent
(for prophylaxis) should be above 80-90% (2). Besides,
patients on Cotrimoxazole, for UTI prophylaxis should be
followed up closely to determine the success of this
regimen. Also, we would like to have comparison studies
with our neighbors to evaluate our results more
objectively.
In conclusion, two thirds of bacterial isolates from
urine samples are resistant to Cotrimoxazole, this
argues strongly against using this medication as an
empiric treatment for urinary tract infections. And,
based on the above data, it is not wise to use
Cotrimoxazole in prophylaxis against UTI. However,
Cotrimoxazole remains a good medication and can be used
after the sensitivity is known.
Table 1:
percentage of different
isolate from 1170 positive cultures.
|
Isolate |
Number |
Percentage |
|
E.coli |
478 |
41% |
|
Klebsiella |
197 |
17% |
|
Pseudomonas |
151 |
13% |
|
Proteus |
107 |
9% |
|
Staphylococcus (Epidermides & Aureus) |
75 |
6% |
|
Enterobacter |
49 |
4% |
|
Streptococcus |
33 |
3% |
|
Others* |
80 |
8% |
*Others: include Salmonella,
Entterobacter Kaluvera, Providencia, Acinetobacter,
Citrobacter, Serratia, Morginella, haemophilus, and
Diphtheroids.
Table 2:
sensitivity percents among the subgroups
|
Group |
op |
IP |
TOTAL |
|
ICU/SAC |
PW |
MALE |
FEMALE |
TOTALIP |
|
Number of sensitive |
69 |
30 |
82 |
71 |
101 |
284 |
353 |
|
Number of Resistant |
125 |
82 |
185 |
116 |
188 |
571 |
696 |
|
Total Number |
194 |
112 |
267 |
187 |
289 |
855 |
1049 |
|
Percent of sensitive |
35.6% |
27% |
30.7% |
38% |
35% |
33.2% |
33.7% |
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