CHAPTER ONE
INTRODUCTION
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 techoic acid or lipopolysaccharide
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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.
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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
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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
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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.
To find the pathogenic bacteria commonly responsible with UTI and
susceptibility patterns this will help the clinicians to choose the right
empirical treatment.
