Prevalence and Antimicrobial Susceptibility of Gram Negative Bacteria in the Urine

Prevalence and Antimicrobial Susceptibility of Gram-Negative Bacteria in the Urine of Caritas University Students


To access the prevalence and sensitivity pattern of urinary pathogens, 60 midstream urine samples from students of Caritas University were investigated using cultural methods. Samples were examined microscopically and cultured in blood agar and McConkey agar. The disk diffusion method was used for antibiotic testing. Of the 60 urine samples, 48 yielded significant growth with a prevalence rate of 80%. It was observed that females were more infected than males with a prevalence rate of 56.70% and 43.30% respectively under the ages of 18-25yrs. Escherichia coli was the most predominant. The isolates were very sensitive to Gentamicin, Nitrofurantoin and Ofloxacin which were the (most sensitive) and the most resistant were Tetracycline, Clotrimazol, Cephalexin and Ampicillin. Therefore, Nitrofurantoin, Gentamicin, Ofloxacin were strongly recommended for the treatment of UTI as indicated in the study.


Title page
Tables of contents
List of tables


1.0 Introduction———————————————————- 1
1.1 Aims and objectives of the study——————————— 3


2.0 Literature review—————————————————–4
2.1 Microorganisms found in urine and their aetiology ————–4
2.1.1 Bacteria————————————————————— 4
2.1.2 Viruses—————————————————————-5
2.1.3 Fungi——————————————————————-6
2.1.4 Protozoa————————————————————–6
2.2.1 Entry of bacteria into the urinary tract—————————-7
2.2.2 Routes of bacteria infection—————————————–7
2.2.3 Symptoms of UTI—————————————————-8
2.2.4 Diagnosis————————————————————–9
2.2.5 Treatment————————————————————-10 Aims of treatment of UTI——————————————10 Future strategies in the treatment of bacteria/UTI——————-11
2.2.6 Prevention and control———————————————-12
2.3.0 Antimicrobial resistance——————————————–12
2.3.1 Mechanisms of drug resistance————————————14 Drug- inactivating enzyme——————————————14 Alteration in the target molecule———————————–14 Decrease uptake of the drugs—————————————14 Increased elimination of the drugs———————————15
2.3.2 Conditions influencing the effectiveness of drugs————–15 Population size—————————————————– 16 Population composition——————————————–16 Concentration and intensity of antimicrobial agent————- 16 Duration of exposure————————————————17 Temperature———————————————————-17
2.3.3 Actions of antimicrobial drugs————————————-17 Inhibition of cell synthesis—————————– ———–17 Inhibition of cell membrane————————————– 18 Inhibition of nucleic acid synthesis—————————– 18 Inhibition of essential metabolites——————————-18


3.0 Materials and methods——————————————– 19
3.1 Sample collection ————————————————- 19
3.1.2 Antimicrobial susceptibility test———————————-20
3.1.3 Urinalysis test——————————————————–21
3.2 Gram staining——————————————————– 21
3.3 Biochemical test—————————————————–22
3.3.1 Catalase test———————————————————- 22
3.3.2 Coagulase test——————————————————– 23
3.3.3 Motility test———————————————————- 23
3.3.4 Methyl test———————————————————– 24
3.3.5 Urease test———————————————————— 25
3.3.6 Indole test———————————————————— 25
3.3.7 Citrate utilization test———————————————– 26


4.0 Result —————————————————————– 27


5.1 Discussion———————————————————— 31
5.2 Conclusion———————————————————– 32
5.3 Recommendation—————————————————-33
Appendix I
Appendix II


Table 1: Sex distribution of cases and prevalence rates—————— 28
Table 2: Bacterial isolates of positive cases with prevalence rate——28
Table 3: The Sensitivity/Resistivity patterns of bacterial isolates—– 29
Table 4: Biochemical test results——————————————– 41


Fig.1: Oxidase test———————————————————–42
Fig.2: Urease test———————————————————– 42
Fig.3: MacConkey culture plate ——————————————-42
Fig. 4: Catalase test ———————————————————-42
Fig. 5: Indole test ————————————————————42
Fig.6: Simmons citrate test————————————————42
Fig.7: Methyl red test ——————————————————42
Fig.8: Vp test—————————————————————-42
Fig.9: Coagulase test ——————————————————-42



Gram-negative bacteria are bacteria that do not retain their crystal violet dye in the Gram staining protocol. They are differentiated by their cell wall structure. The following characteristics are displayed by gram-negative bacteria as follows Cytoplasmic membrane Thin peptidoglycan layer(much thinner than gram-positive) Outer membrane containing lipopolysaccharide outside the peptidoglycan layer Porin exists in the outer membrane, which acts like pores There is a space between the layer of peptidoglycan and the secondary cell membrane, called the periplasmic space If present, flagella have four (4) supporting rings instead of two No teichoic acid or lipopolysaccharide.

Some examples of gram-negative bacteria include; Escherichia coli, Salmonella species, Pseudomonas species, Klebsiella species, Proteus species, Helicobacter species, Moraxella species, Cyanobacteria species, Spirochetes species.

They also constitute a serious problem in urinary tract infections in many parts of the world. Appropriate antimicrobial treatments are often critical to decreasing morbidity and mortality among hospitalized patients having infections caused by pathogens. Gram-negative bacteria are non-spore-forming bacilli that grow rapidly on ordinary laboratory media under both aerobic and anaerobic conditions. It has been estimated that symptomatic urinary tract infection (UTI) occurs in as many as 7 million visits to emergency units and 100,000 hospitalised annually. UTI has been the most common hospital-acquired infection, accounting for as many as 35% of nosocomial infections. It is the second most common cause of bacteraemia in hospitalised patients (Nacem, 2000). UTI is known to occur in all populations but has a particular impact on females of all ages and males at two extremes of life, immunocompromised patients and anyone with function or structural abnormalities of the urinary and excretory system.

UTI is known to be the microbial invasion of any of the tissues of the urinary tract reaching from the renal cortex to the urethral meatus (Nicolle, 2000). It is also known to be the presence in two consecutive urine samples of greater than 100 rods (105 ) organisms per ml of a single bacterial strain in the urinary tract. UTI can be categorized as ascending or descending. Infections that are confined to the urethral or the bladder are ascending and referred to as urethritis or cystitis respectively. On the other hand, the pathogens spread from one or other infected body site to the kidney down along the ureter to the bladder. Such descending UTI causes severe kidney infection, a condition called pyelonephritis (Parsons, 1958). This is potentially more serious; infections to the urethra are called urethritis and to the prostate gland are called prostatitis. This classification is the presence or absence of symptoms, reoccurrence or absence or presence of complicating factors which are host factors facilitating establishment and maintenance of bacteraemia or worsening the prognosis of UTI`s engaging the kidney.
The majority of pathogens are gram-negative species with a predominance of members of Enterobacteriaceae (Neu, 1992). Escherichia coli accounts for the majority of urinary tract infections in young women but other gram-negative rods of different genera such as Proteus species and pseudomonas aeruginosa anaerobic gram-negative rod is also troublesome. As urinary tract pathogens because of their resistance to antimicrobial medicine make it is difficult to treat successfully (Nester et al. 1998).

Antibiotics are used for the control of bacterial infections in humans. Generally, gram-negative bacteria are sensitive to many antimicrobial agents but strains from different patients and carriers differ in the pattern and degrees of sensitivity to different drugs. Increasing antimicrobials resistance in the bacterial pathogen is a worldwide concern. The prevalence of antimicrobial resistance among urinary tract infectious agents is also increasing (Mathai et al. 2001: Karlowsky et al. 2001) and its treatment has become more complicated due to increasing resistance and empirical therapy leading to treatment failures of most associated with gram-negative bacteria (Blondeau et al. 1999). The present study investigated the pattern of gram-negative uropathogens and their antimicrobial resistance pattern among the clinical isolates to the commercially available antibiotics that are often prescribed in urinary tract infectious cases

1.1 Aims and objectives

To find out the prevalence of gram-negative organisms in the urinary tract among Caritas university students. To investigate their antibiotic sensitivity pattern to enable formulation of drugs for urinary tract infection in our community. To determine the age and sex prevalence. To determine the prevalence of bacterial strains and their antimicrobial susceptibility in urine. Find the pathogenic bacteria commonly responsible for UTI and susceptibility patterns this will help the clinicians to choose the right empirical treatment.


Acharya, V.N.C., (1992), UTI – A dangerous Systematic Sepsis. Journal of post advanced Medicine 38, 52-54.

Ameila, G.C., Macallister, T.A & Ray, I. (1973).Measurement of Bacteria by Plane, Upside Culture. Lancet, 1, 97-99.

Akinyemi, K.O., Alabi, (1997). Antimicrobial S.A, Taiwo, Susceptibility M.A Pattern.& Omonigbehin, E.A. Journal of Hospital Medicine, 1(8), 7-11.

Azubuike, C.N, Nwamadu, O.J. & Uzoije, N. (1994). Prevalence of UTI among Patients. West Africa Journal of medicine 13, 48-52.

Cite this article: Project Topics. (2021). Prevalence and Antimicrobial Susceptibility of Gram Negative Bacteria in the Urine. Retrieved October 18, 2021, from

Copyright © 2021 Author(s) retain the copyright of this article.
This article is published under the terms of the Creative Commons Attribution License 4.0

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