Introduction

The term 'bacteriuria' means the presence of bacteria in urine. It may results from contamination during or after collection of urine or it may indicate the presence of bacteria in bladder urine. To distinguish among these possibilities; Kass₁ introduced the term “significant bacteriuria” which was defined as the occurrence of 10⁵ or more bacteria per ml of a voided midstream urine aseptically collected. Bacteriuria can be divided into symptomatic and asymptomatic. Asymptomatic bacteriuria refers to the presence and multiplication of bacteria in the bladder urine in the absence of symptoms of urinary tract infection while symptoms are present in symptomatic cases₃.

Bacterial infections of the urinary tract are commonly seen in outpatients, hospitalised patients and apparently healthy populations. Asymptomatic bacteriuria occurred reliably more frequently in females as compared with males and it is a major criterion of urinary tract infection(UTI)₁₄. Reasons adduced to this include shorter and wider urethra and its proximity to the anus. It was therefore thought necessary to investigate incidence of asymptomatic bacteriuria in female undergraduate students and also to study the effects of commonly used antibiotics on the bacteria isolated.

Materials And Methods

Three hundred healthy asymptomatic undergraduate students of Lagos State University between ages of 16 and 26 were randomly sampled. Students with any symptom suggestive of urinary tract infection or those who have taken antibiotics two weeks before or were currently on antibiotics, or pregnant were excluded from the study. Midstream urine samples were collected from clinically healthy female students into sterile universal bottles. The samples were examined immediately or refrigerated (4°C) and examined within 6 hours of collection.

Each of the urine samples (5ml.) was centrifuged for 1min and examined under the microscope (Griffin model) for the presence of yeast cells, parasites, leucocytes, erythrocytes and granular casts.

Each specimen was cultured on MacConkey agar and Blood agar. The inoculated plates were incubated (using Gallenkamp model cooled incubator) at 37°C aerobically for 24hours. Those without growth were re-incubated for an additional 24hours. Samples with 10⁵ or more bacteria per ml were recorded as showing significant bacteriuria. Bacterial species were identified according to standard bacteriological tests.

Pure isolates were tested by the plate diffusion method for antibiotic susceptibility on the Diagnostic Sensitivity Teat (DST) agar (OXOID CM26) with antibiotic disc. The sensitivity plates were incubated aerobically for 18hours and the zone of inhibition was noted.

Results

The colour of the urine samples ranged from colourless, straw, to turbid. From the microscopic examination, 18 samples contained epithelial cells, 7 samples, leucocytes, 16 samples, yeast cells, 3 samples, granular casts and crystals. No Trichomonas vaginalis was found. Thirty samples (10%) showed significant bacteriuria while 270(90%) showed no bacteriuria or non-significant bacteria.

Escherichia coli was found to be the most predominant, (50%), followed by Staphylococcus aureus (20%), Streptococcus faecalis (13.33%) Staphylococcus albus (10%) and Klebsiella (6.67%).

The result of the sensitivity test (Table3) showed that E. coli strains were most sensitive to Co-trimoxazole followed by Cefuroxin but were resistant to Ampicillin and Tetracycline. Klebsiella was sensitive to Cotrimoxazole and very resistant to Ampicillin and Penicillin. Overall.Co-trimoxazole was the most effective while Ampicillin and Tetracycline were the least effective against the bacteria strains.

Figure 1

Table 1: Level of bacteriuria

Figure 2

Table 2: Bacterial species isolated from asymptomatic LASU female students urine.

Figure 3

Table 3: Sensitivity pattern of some bacteria isolated from the urine of asymptomatic students

Discussion

The term 'bacteriuria' means the presence of bacteria in urine. Bacteriuria can be divided into symptomatic and asymptomatic. Asymptomatic bacteriuria refers to the presence and multiplication of bacteria in the bladder urine in the absence of symptoms of urinary infection while symptoms are present in symptomatic cases₃. Urinary tract bacterial infections are common in women. Moreover, they tend to recur throughout life and in the same relatively small group of women. In some instances, however, especially with frequent sexual activity, pregnancy, stone disease, or diabetes, symptomatic cystitis or pyelonephritis develops and antimicrobial therapy is indicated₄.

Asymptomatic bacteriuria is a common finding, and past history of symptoms such as frequency and dysuria is common₅. Akinkugbe et al.₆, report incidence of asymptomatic bacteriuria in paediatric populations while Omer and Ahmed₇ report incidence in school children and Olusanya and Olutiola₈ report incidence in students of high school in Nigeria.

It has also been reported that bacteriuria is common among women probably due to the proximity of female urethra to the anus, its short length and its termination beneath the labia₁₀. It has been observed that bacteriuria in young girls and women is preceeded by colonisation of the vaginal introitus by the specific species of Enterobacteriaceae that produces the infection. Adhesion property of the bacteria is an important factor that mediate the ability of a bacterial species to colonise the vaginal or any mucosal surface.

Bacteria associated with bacteriuria in asymptomatic female in this study are E. coli, S.aureus, S. albus, S. faecalis and Klebsiella. E. coli accounts for the greatest percentage (50%) of micro-organisms associated with significant bacteriuria. This is similar to many previous reports₂, ₃, ₈,₉.

It accounts for 47% of all isolates, whereas in general practice it accounts for more than 90% hence most work on the pathogenesis of urinary tract infection has focused on this micro-organism.

The current study shows a 10% incidence of significant bacteriuria. This value is higher than 5% incidence bacteriuria among students of secondary schools₇ and females of 14-17year of age with 3.3% bacteriuria₁₁. The higher value obtained could be possibly due to increase in sexual activities among the University age group and /or increased age compared to the secondary school students. The age of the students screened ranges between 16 and 26 compared to less than 16 years of secondary school age. The value of 1.4-2.1% obtained in Europe₁₃ several years ago was much lower than our current report. This may be attributed to the difference in socio-economic and hygiene levels of the people. Asymptomatic bacteriuria occurred reliably more frequently in females as compared with males and it is a major criterion of urinary tract infection(UTI)₁₄.

Other bacteria isolated from this study included S. aureus (20%), S. albus (10%), S. faecalis (13.33%) and Klebsiella (6.67%). Akinkugbe et al., 1973 found E. coli in two-thirds of the urban children while S. aureus was the commonest among children who are asymptomatic. Olusanya and Olutiola 1984, isolated S. aureus (25%)from the majority of the healthy female students closely followed by E. coli. (21%) Omer and Ahmed, 1992, found S. aureus as the commonest case of asymptomatic bacteriuria followed by E. coli.

Co-trimoxazole and Nitrofurantoin were very effective against E. coli in the current study in agreement with other previous reports₈ . Co-trimoxazole was also effective on other isolates except S. albus which was sensitive only to Erythromycin. The result also showed that there was a rapid decline in Ampicillin and Tetracycline sensitivity. It has been suggested that the effectiveness of Co-trimoxazole against isolates may be due to its ability to act on both Gram positive and Gram-negative microorganisms₁₄.

The high prevalence of resistance to the commonly used antibiotics such as Ampicilllin and Tetracycline has caused considerable alarm. This may be due to failure to control the sale and restrict the use of antibiotics in our community.

In conclusion, while improved level of hygiene is likely to assist in reducing asymptomatic bacteriuria which may be complicated by urinary tract infection, the general pubic should be educated on the danger in taking unprescribed drugs and therefore stop indiscriminate use of antibiotics. The sale of such drugs as antibiotics must be restricted to physician's prescription. The female should always clean from forward to backward after using the toilet so as not to transfer the microorganisms from the bowel to the vagina. These will help in reducing the high rate of asymtomatic bacteriuria among our university female students.