DEVELOPMENTAL CYCLE OF CHLAMYDIA

CHAPTER ONE

INTRODUCTION

Chlamydiae
are small gram-negative obligate intracellular microorganisms that
preferentially infect squamocolumnar epithelial cell (www. Google. Com.2010).

        Chlamydia is the most prevalent sexually
transmitted disease resulting in urethritis, with frequencies exceeding those
of Neisseria gonorrhoeae  

        In the United State
for instance, roughly four million cases are reported annually mostly occurring
in men and women under the age of 25 (Barners, 1990).

        In Nigeria and indeed most developed
nation, majority of the reported cases urethritis are diagnosed as being caused
by Neisseria gonorrhoeae, StaphyLococcus
aureus and streptococcus Spp.

        This could be attributed to inadequate facilities
to establish proper test for the diagnosis of chamydia infection. As a result,
cases of urethritis are wrongly diagnosed and treated. This calls for proper research
work to establish the major aetiologic agent of urethritis. This will go a long
to aid prompt treatment of reoccurring urethritis resulting from wrong diagnosis
and treatment.

        According to the centers of disease
control and prevention (CDC), chlamydia is the most common bacteria infection
in the United State. About 1.1 million new cases were
reported in 2007.

        However, because as many as 75% of
infected women and 50% Infected men do not experience symptoms of infection,
the CDC estimates that up to 2.8 million new cases may occur each year in the
United States. Chlamydia is most prevalent among teenagers. Nearly 75% of all
new cases occur in women under the age of 25. By age 30, 50% of sexually active
women have been exposed to Chlamydia.

        Non-gonococcal urethritis is the most
commonly diagnosed sexually transmitted disease in men in the United States.

OBJECTIVES OF THE STUDY

i.           
To determine the prevalence of
Chlamydia infection.

ii.         
To ascertain the age distribution of
the infection.

iii.       
 To determine the sex distribution of the
infection.

iv.        
To make recommendations on how to
control or eradicate the infection.

CHAPTER
TWO

LITERATURE
REVIEW

Chlamydiae are obligated intra-cellular prokaryotic
parasites of eukaryotic cells. This implies that these organisms can survive
only by establishing within the epithetical cell of the human or animal cells.
The reason for this intracellular parasitism is the fact that chlamydiae are
energy parasites i.e. they require an energy source for replication and
survival.

        All
human cells have specific system that they use to form ATP (adenosine
triphosphate) which is the major source of energy. Chlamydiae have a cell
membrane transport system that ‘steal’ ATP from the host cells.

Chlamydiae are considered as bacteria for the
following reasons: 

a.        
Like
bacteria, they posses both RNA and DNA.

b.       
They
multiply by binary fission.

c.        
They have
rigid cell wall resembling the bacteria cell wall but lacks muramic acid and is
not susceptible to lysozyme action.

d.       
They posses
ribosomes.

e.        
They have a
variety of metabolically active enzymes example they can liberatec Co₂
from glucose. Some can be synthesized folates .

f.         
Their growth
can be inhibited by many anti-microbial drugs, especially tetracycline and
erythromycin.

As a result of their unique development cycle these
micro-organisms have been classified into a separate order, chlamydiales, with
one family containing one genius, Chlamydia. There are three species, C. psittaci, C. Pneumoniae and C. trachomatis. The focus of this review
is on. trachomatis the
aetiologic agent of urethitis, cervicits, prostatitis, trachoma, inclusion
conjunctivitis, pelvic inflammatory disease (PID). Others includes;
Lymphogranuloma venereum (LGV), Reiter’s disease and infant pneumonia,
salpingitis.

This species is divided into several serological
varieties (serovars) ranging A-K.

The serovars implicated in both men and women for
urethritis are serovars D-K which are associated with genital tract infections.
(peeling,   et al., 1996)

DEVELOPMENTAL
CYCLE OF CHLAMYDIA

Chlamydiae have a unique biphasic life cycle that
is adaptable to both intracellular and extracellular environments.

a.          
Elementary
Body (EB): this is the small infections metabolically adapted for surviving
outside the cell. The EB prevents phagosome-lysozyme fusion and then undergoes
reorganization to form a reticulate body (RB).

b.         
Reticulate
body (RB): The larger intracellular from, non-infectious metabolically active,
replicate form that is unstable out of the cell. 

The elementary body is adapted for extracellular
survival and infection but does not replicate. It is relatively resistant to
the usual method of disinfections (sonication) and trypsin treatment and is
relatively impermeable. The organism have special preference for columnar
epithelia cells.

After
attachment, the elementary bodies are endocytosed (engulfed) by the host cell
and once inside the cell, the EB loses its infectivity and undergoes a number
of changes associated with its transition to reticulate body. Continued
development occurs with the formation of a cytoplasmic