Prevalence And Antimicrobial Susceptibility Of Gram Negative Bacteria In The Urine

Project and Seminar Material for Microbiology

Project and Seminar Material for Microbiology


In order 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 Macckonkey agar. 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 the 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 Gentamycin, Nitrofurantoin and Ofloxacin which were the (most sensitive) and the most resistant were Tetracycline, Cortrimozol, Cephalexin and Ampicillin. Therefore, Nitrofurantoin, Gentamycin, Ofloxacin were strongly recommended for the treatment of UTI as indicated in the study.

Chapter One


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

  1. Thin peptidoglycan layer(much thinner than gram positive)
  2. Outer membrane containing lipopolysaccharide outside the peptidoglycan layer
  3. Porin exists in the outer membrane, which acts like pores
  4. There is a space between the layer of peptidoglycan and the secondary cell membrane, called the periplasmic space
  5. If present, flagella have four (4) supporting rings instead of two
  6. No techoic acid or lipopolysaccharide

Some examples of gram negative bacteria include; Escherichia coli, Salmonella species, Pseudomonas species, Klebsiella species, Proteus species, Helicobacter species, Mosoxella 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 the infections caused by the 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 infects (UTI) occurs in as many as 7million visits to emergency units and 100,000 hospitalised annually. UTI has been the most common hospital acquired infections, accounting for as many as 35% of nosocomial infection. 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, immuno-compromised 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 urethrameatus (Nicolle, 2000). It is also known to be the presence in two consecutive urine samples of greater than 100rods (105 ) organisms per ml of a single bacterial strain in the urinary tract. UTI can be categorized in ascending or descending. Infections which are confined to the urethral or the bladder are ascending and referred to as uretitis 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 cause severe kidney infection, a condition called pyelonephritis (Parsons, 1958). This is potentially more serious; infections to the urethra are called urethritis and to the prostrate gland are called prostitis. 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.

Majority of pathogens are gram negative species with predominance of members of Enterobacteriace (Neu, 1992). Escherichia coli accounts for majority of urinary tract infections in young women but other gram negative rods of different genera such as proteus species and pseudomonas aeruginosa an aerobic gram negative rod is also troublesome. As a urinary tract pathogens because of its resistance to antimicrobial medicine make it difficult to treat successfully (Nester et al. 1998).

Antibiotics are used for the control of bacterial infections in human. 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 bacterial pathogen is a worldwide concern. The prevalence of antimicrobial resistance among urinary tract infectious agents is also increasing (Mathai et al. 2001 : Karaloswsky 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

Aims and Objectives

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

Chapter Five

Discussion, Conclusion and Recommendation

5.1 Discussion

The overall prevalence of UTI in this study was 80% and females were significantly more affected than males. Previous reports (Aimel et al. 1973; Robert et al. 1993) of studies carried out in different parts of the world indicates higher incident among females than males, this may be explained by the fact that females pass short urethra. Also the spread of normal flora in faecal materials from the anus to the vagina from where the bladder could be infected as a result of poor anal cleaning could be responsible for the observed result in female urine sample.
The prevalence of UTI in Caritas University which is found to be 80% is quite alarming . This figure is higher than the prevalence rate of 51.35% recorded by Savi et al. (2011) and 60% obtained in another study in the north central region of Nigeria. This calls for caution among the female students in Caritas

University. The high rate maybe due the increase in female with poor hygienic practice and also indiscriminate sexual behaviour among the female students.

E.coli was the commonest organism isolated, this is in conformity with the previous work done by Handeau et al. 2011. The least resistance by the bacterial isolates to antimicrobial agents was observed to be Tetracycline, Cotrimozole, Ampicillin, Cephalexin as seen from this study. The factors contributing to those resistance may be due to indiscriminate abuse of antibiotic by students. Other factors may include poor quality of drugs, poor storage and exposed drug (Okeke et al. 1999) etc. the reduction of antibiotics prescription and dispensation have been associated with reduced antibiotic resistance (Schiemann et al. 2010).

5.2 Conclusion

This study has revealed that UTI among female students is a very difficult health problem which must be properly addressed. This has also revealed that the most causative organisms of UTI in this university, community among the female students are the gram negative organisms which were shown to be sensitive to the following drugs. Gentamycin, Ofloxacin and Nitrofurantoin. It could be suggested that in the face of clear UTI symptoms and in the absence of physician or clinician of these three drug abuse (Gentamycin, Ofloxacin and Nitrofurantoin) could be procured and used and with an experienced doctor is seen for confirmation.

5.3 Recommendation

This is the appropriate time to investigate infection control measures which are lacking in the most health care institutions, firm, industries etc. There is also need to establish the sense and control surveillance agencies. There is need for interaction between physicians and microbiology department because there have been cases where by the antibiotics tested are different from those frequently prescribed since the laboratories use only the susceptibility diffusion disc available to them.

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