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Inadequate data on antimicrobial susceptibility patterns in the Africa region and indeed in Zambia have led to ineffective empirical treatment before the culture and sensitivity results are made available. The purpose of this study was to determine the antimicrobial susceptibility patterns amongst the most common bacterial causes of UTIs amongst patients presenting at Kitwe Central Hospital (KCH), Zambia.  A 5-year record review of data captured in the laboratory urine register from 2008 to 2013 was conducted. Demographic data, culture and antimicrobial susceptibility data were entered in Epi Info version 7 and analysed using SPSS version 17.0. Associations were determined using the Chi-squared test at the 5% significance level.  A total of 1854 records were extracted from the laboratory register.  The highest frequency of UTI (43.9%) was in the 15–29 years age group. The overall sensitivity patterns indicated that E.coli was mostly sensitive to ciprofloxacin (69.8%), Klebsiella species to ciprofloxacin (68.2%), Proteus species to cefotaxime (66.7%) and Staphylococcus saprophyticus to nitrofuratoin (63.7%). Sensitivity for E. coli to nalidixic acid was higher for males (58.6%) than females (39.5%).  Sensitivity for E. coli to cefotaxime and norfloxacin varied with age (Chi-squared for trend=10.32, p=0.001).  Our results have shown that UTI pathogens isolated at KCH were less than 70% sensitive to the recommended and used antibiotic. Studies to establish highly sensitive antibiotics to UTI pathogens are needed to effectively treat patients.

Introduction

Urinary tract infections (UTIs) account for one of the major reasons for most hospital visits and the determination of the antimicrobial susceptibility patterns of uropathogens will help to guide physicians on the best choice of antibiotics to recommend to affected patients [1]. Bacterial infections that cause community-acquired urinary tract infections and upper respiratory tract infections are most frequently treated empirically. However, an increase in antimicrobial resistance has raised challenges in treating outpatients [2]. The increases in antibiotic resistance of urinary tract pathogens can be attributed mainly to frequent and indiscriminate use of antibiotics [3]. Increasing resistance in bacterial pathogens been reported widely [4]. Despite the widespread availability of antimicrobial agents, UTIs have continued to be increase resistance to antimicrobial agents [5]. The prevalence of antibiotic resistance in UTIs varies according to geographical and regional location [4].  Studies conducted in Pakistan and Washington showed variations in resistance to antibiotics by sex and age group [6,7]. UTIs are caused by different microbial pathogens. The most prevalent bacteria causing UTI are Escherichia coli, Staphylococcus saprophyticus, S. aureus, Proteus sp., Klebsiella pneumoniae, Pseudomonas aeruginosa, and enterococci [1].
The Ministry of Health [Zambia] recommends antibiotic prescription for UTIs to be guided by sensitivity results [8]. The recommended drugs for the treatment of UTI in Zambia are as follows: amoxicillin, nitrofurantoin, nalidixic acid, ciprofloxacin, cefotaxime and ceftriaxone [8]. Limited data on urinary tract pathogens and their in-vitro susceptibility pattern hinder effective empirical treatment. A retrospective study was conducted to determine susceptibility patterns for some of the commonly used antibiotics for the treatment of urinary tract infections at Kitwe Central Hospital, Zambia. 

Methods

The study was conducted at the Kitwe Central Hospital, which is a provincial referral facility for Copperbelt, North Western and Luapula provinces of Zambia. Ethics clearance was obtained from the Tropical Diseases Research Centre Ndola reference number TRC/C4/07/2015 to conduct the study.  
An analysis of secondary data was performed on data captured in the microbiology laboratory register from 2008 to 2013.  The data were captured using Epi info version 7 and analyzed using SPSS version 17.0.  Proportions were compared in 2 x 2 contingency tables using the Yates’ corrected Chi-squared test, while the uncorrected Chi-squared test was used to determine associations in higher contingency tables.  The Chi-squared test for trend was used to determine linear associations.  The cut off point for statistical significance was set at the 5% level.
The culture and sensitivity results that were analysed were results from routine analysis of urine specimen collected from both in- and out-patients. Mid-stream urine
and occasionally urine specimen collected suprapubically were analysed as outlined in the standard operating procedure. Culture was done on CLED agar. Susceptibility testing was done on Mueller Hinton agar using Disk diffusion method with the inoculums suspension in sterile distilled water prepared using a 0.5 McFarland standard.

Results

Table 1 shows susceptibility patterns of commonly isolated UTI pathogens to antibiotics. E.coli isolates were more sensitive to ciprofloxacin (69.8%), norfloxacin (64.0%) and cefotaxime (61.0%) and least to cotrimoxazole (12.7%). Klebsiella species isolates were more sensitive to ciprofloxacin (69.8%), norfloxacin (67.2%) and least to cotrimoxazole (8.4%). Proteus species were  more sensitive to cefotaxime (66.7%), norfloxacin (61.4%), ciprofloxacin (60.6%) and least to co-trimoxazole (17.7%). Staphylococcus saprophyticus isolates were more sensitive to nitrofurantoin (63.7%), ciprofloxacin (63.1%) and norfloxacin (60.5%).
Table 1 Susceptibility patterns of commonly isolated UTI pathogens at Kitwe Central Hospital (Zambia) from 2008-2013

Sensitivity levels for E. coli to antibiotics varied by year. Overall, E.coli was most sensitive to ciprofloxacin (69.8%), norfloxacin (64.0%) and cefotaxime (61.0%) with least sensitivity to co-trimoxazole (12.7%) as shown in Table 2.
Table 2. Susceptibility by year for E.coli to antibiotics at Kitwe Central Hospital (Zambia) from 2008-2013

Apart from ciprofloxacin and co-trimoxazole, sensitivity levels for the other drugs remained constant as shown in table 3.
Table 3 Linear trends in sensitivity levels by year

For both ciprofloxacin and co-trimoxazole, sensitivity levels declined between 2008 and 2013. A unit change in the year corresponded to about 6%(-6.48 for ciprofloxacin and -5.93 for co-trimoxazole).
Sensitivity levels varied by age for cefotaxime (p=0.010) and norfloxacin (p=0.010) as shown in Table 4.
Table 4 E.coli Susceptibility by age group at Kitwe Central Hospital (Zambia) from 2008-2013

Sensitivity levels for cefotaxime linearly decreased with age (Chi-squared test for trend=10.32, p=0.001) but not for nalidixic acid (Chi-squared test for trend=2.20, p=0.138).  The lowest sensitivity level was observed among the 45 years or older patients (48.4% for cefotaxime and 54.5% for norfloxacin). No  significant differences  in antibiotic sensitivity to E. coli were observed between females and males, except for nalidixic acid (p<0.001) with higher levels of sensitivity for males (58.6%) than females (39.5%) as shown in table 5.
Table 5 E.coli Susceptibility by sex at Kitwe Central Hospital (Zambia) from 2008-2013

Discussion

This study provides the information about the antibiotic susceptibility patterns of common bacterial pathogens isolated from urine specimen of patients with urinary tract infections at Kitwe Central Hospital on the Copperbelt province of Zambia. In this study, 1854 urine culture and sensitivity results were analyzed covering the period 2008 to 2013.
Of the 1854 culture results that were analyzed, the most common organisms were   E.coli (46.7%), Klebsiella species (17.1%), Proteus species (15.4%) and Staphylococcus saprophyticus (12.6%). These findings are slightly to what Ekwealor et al found in Nigeria that the most prevalent isolates were S. aureus (28%), E. coli (24.6%), and S. saprophyticus (20%) [1]. Analysis of the susceptibility pattern excluded Enterobacter species, Enterococcus faecalis and Pseudomonas because of small numbers. Susceptibility by age and sex were only done for E.coli because of large numbers.
In the current study, E.coli isolates were more sensitive to ciprofloxacin (69.8%), norfloxacin (64.0%) and cefotaxime (61.0%). The analysis of the trends revealed that apart from ciprofloxacin and co-trimoxazole, sensitivity levels for the other drugs in the table remained constant. For both ciprofloxacin and co-trimoxazole, sensitivity levels declined between 2008 and 2013. A unit change in the year corresponded to about 6%(-6.48 for ciprofloxacin and -5.93 for co-trimoxazole). A study conducted in Tumkur, Bangalore, revealed lower sensitivity level for E.coli to ciprofloxacin (24%), norfloxacin (25.5%) and co-trimoxazole (37%) [10]. Another study conducted in Chandigarh, northern India [11], revealed similar sensitivity for E.coli to ciprofloxacin (62%) among outpatients but higher than 48% sensitivity observed in in-patients.  However, the sensitivity level for E. coli to cefotaxime in the current study was lower than the 96% observed among out-patients and 80% among inpatients. A retrospective study carried out in Brazil revealed rate of resistance of E.coli to ciprofloxacin was higher than expected with highest of 36.0% [12]. A study by Cho et al placed ciprofloxacin (20.7%), levofloxacin (22.7%), co-trimoxazole (34.3%) and ampicillin-clavulanate (42.9%) as the least active substance compared to nitrofurantoin (93.1%) and fosfomycin (100%) [13]. A study by Ahmad et al revealed that E.coli had higher rates of rates of resistance to ampicillin (90%), tetracycline (70%), erythromycin (70%) and Cotrimoxazole (50%) [14]. Fasugba et al concluded that ciprofloxacin resistance in UTI caused by E.coli is increasing hence a need to reconsidered empirical treatment [15].  A study by Bryce et al revealed high rates of resistance ampicillin (23.6%), trimethoprim (8.2%), co-amoxiclav (26.8%) and lower rates for ciprofloxacin (2.1%) and nitrofurantoin (1.3%) [16]. Klebsiella species isolates were more sensitive to ciprofloxacin (68.2%), norfloxacin (67.2%) and the least sensitive to co-trimoxazole (8.4%). The study in Tumkur, Bangalore also showed that Klebsiella species had sensitivity of 63% (ciprofloxacin), 66% (norfloxacin) and 58% (co-trimoxazole) [11]. Proteus species were more sensitive to cefotaxime (66.7%), norfloxacin (61.4%) and ciprofloxacin (60.6%). A study done in Portugal revealed the sensitivity of Proteus species as 2.9% for nitrofurantoin, 75.1%  for norfloxicin,75.0% for ciprofloxacin and 73.2% for cefotaxime [17]. Staphylococcus saprophyticus isolates were more sensitive to nitrofurantoin (63.7%), ciprofloxacin (63.1%) and norfloxacin (60.5%). A study in Iran showed the sensitivity of coagulase negative staphylococci as 100% for ciprofloxacin and nitrofurantoin, 69.2% for co-trimoxazole, 23.1% for cefotaxime and 0% for nalidixic acid [18].
The Sensitivity levels of E.coli varied with age for cefotaxime and norfloxacin.  Furthermore, the sensitivity variation was linearly related to age for cefotaxime suggesting that the drug should be limited to younger age groups of <15 years.  Although no similar pattern emerged for norfloxacin, the least sensitivity was observed in the 45 years or older age group, indicating that the drug should not be used for persons in this age group. Sensitivity to cefotaxime decreased as age increased and this was the same for nalidixic acid and nitrofurantoin. Cefotaxime had the highest sensitivity in the under 15 years of age (70.6%) and lowest in the 45 years or older age group (48.8%). Chloramphenicol had the highest sensitivity in the 15-29 years age group (53.2%) and lowest in the <15 years age group (30.0%). Ciprofloxacin had highest sensitivity in the under 15 years age group (75.5%) and lowest in the 45 years or older age groups (60.5%). Co-trimoxazole had the highest sensitivity in the 45 years or older age group (17.2%) and the lowest in the under 15 years age group (0.0%). Nalidixic acid had the highest sensitivity in the under 15 years age group (56.5%) and lowest in the 45 years or older age group (33.6%). Nitrofurantoin had the highest sensitivity in the 15-29 years age group (61.2%) and the lowest in the under 15 years age group. Norfloxacin had the highest sensitivity in the   under 15 (80.0%) and lowest in the 45+ age group (54.5%).
The only sex difference in sensitivity levels was observed for nalidixic acid, with higher sensitivity for males (58.6%) than females (33.8%).  However, the level of sensitivity was too low to recommend the use of nalidixic acid among males only.
A study done in Pakistan on the resistance of E.coli across age groups and sex revealed variation in resistance patterns of E.coli to antibiotics. Nitrofurantoin was about  2-fold more resistant  in males than  females, while trimethoprim,  co-trimoxazole  and  ceftazidime showed 11%  more  resistance in males than females. Ceftriaxone, ciprofloxacin showed 13%, 14%, more resistance in males as compared to females, respectively. E.coli also manifested almost complete resistance to trimethoprim and co-trimoxazole in all the age groups. The isolates from below 40 years male patients and age groups 50-59 and 70-79 showed almost complete resistance to ciprofloxacin, while  it  was  effective  in  half  of male  patients  in  age  groups  40-49  and  60-69.  Nitrofurantoin showed 33% resistance in age groups 0-9, 20-29 and 30-39 and was found almost sensitive in all other age groups.  Ceftriaxone showed 60% resistance in age group 60+. Ceftriaxone was sensitive in   age group 10-19, while it showed variable resistance among other age groups.
Ciprofloxacin, co-trimoxazole and trimethoprim showed variable resistance patterns in all age groups except 40-49 in which these antibiotics were effective among half the female patients [6]. A study done in USA reported that differences in antibiotic susceptibility to common urinary anti-infectives among E. coli isolated from males versus females was meaningful hence recommending that male sex alone cannot be used as a basis for empirical treatment [7].
Our results have shown that the UTI pathogens isolated at KCH were less than 70% sensitive to the recommended and used antibiotic. Studies to establish high sensitive antibiotics to UTI pathogens are needed to effectively treat patients.

Authors’ contributions

JC obtained the data, conducted preliminary analysis and drafted the manuscript. JM revised the manuscript. CB research protocol development, analysed the findings and revised the manuscript. SS interpreted the findings and edited the manuscript MLM reanalyzed the data, interpreted the results and edited the manuscript.

Acknowledgement

We would like to thank the management of Kitwe Central Hospital for allowing us to use their records.

References

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