7
Microbiology, inflammation, and Viral infections
Table 7.11
Common characteristics of chlamydia, bacteria, and viruses
Feature
Chlamydia
Bacteria
Viruses
Ubiquitous nature
Yes
Yes
Yes
Multiplication in cell-free medium
No
Yes
No
Multiplication dependent on host-cell nucleic acid
No
No
Yes
Smallest reproductive forms— less than 350 nm
Yes
No
Yes
Cell wall or peptidoglycan present
Yes
Yes
No
DNA and RNA present
Yes
Yes
No
Various metabolic systems present
Yes
Yes
No
Multiplication inhibited by:
Antibodies alone
Yes
No
Yes
Antibiotics
Yes
Yes
No
exudation as the single most common feature among cases of
genital
C. trachomatis
infection.122
Although direct detection of
Chlamydia
in appropriately
stained representative smears has been practiced for the long-
est time, the diagnostic value of direct smear examination in
specimens other than conjunctival smears has been questioned
repeatedly. A number of advances in
Chlamydia
diagnosis have
been made in more recent years. Improved culture techniques,
direct immunofluorescence antigen detection and enzyme-
linked immunosorbent assay (ELISA)-based tests, have been
introduced with a high degree of specificity and sensitivity. In a
recent summary statement, the CDC, however, enumerated the
state of
Chlamydia
diagnosis. It stated, "Despite the encouraging
improvement in diagnostic capability, current tests are not ideal.
They are relatively difficult to perform, require considerable
experience and have limited application."115
Until recently, tissue cell culture has been used as a "gold
standard" for the diagnosis. Kellogg critically reviewed the
various diagnostic methods and their limitations.123 Briefly
stated, the number of swabs cultured, site of epithelial sam-
pling, type of collection device, storage, evaluation of symptoms,
serum immunoglobulin levels and antibodies, any treatment
to stabilize the cellular membranes including antibodies and
steroid preparations and other drugs, maturations, and various
inhibiting substances in the vaginal secretions can have a bear-
ing on the diagnostic value of
Chlamydia
cultures. Also, selection
of container, cell line and pretreatment, inoculation technique
and culture duration, concomitant infections and contamina-
tion, and type of stain used to detect growth of the organism in
the cell line all have a bearing on the performance of the culture
techniques. Cultures for
Chlamydia
are generally more valuable
in younger patients with primary first-time infection. Antigen
assays, on the other hand, depend on the population makeup.
These results tend to be less positive in asymptomatic and older
patients. The size of the population, clinical disease, quality of
the specimen, and reading threshold also determine the results
of direct
Chlamydia
diagnostic procedures.
Along with Gupta and co-workers52 and Bibbo and Wied,13
Naib has documented the cytologic detection of
Chlamydia.70,124
Elementary bodies that are abundant in symptomatic individu-
als and may be easily cultured cannot be detected in Papani-
colaou stained specimens. Romanowsky stained specimens can
be helpful for such identification, especially when the sample
Fig. 7.64
C h la m y d ia tra c h o m a tis
infection.
Moth-eaten, rarified
appearance and numerous fine-walled intracytoplasmic vacuolated
structures. Vaginopancervical smear (Papanicolaou x OI).
is examined under dark-field illumination. A golden-yellow
discoloration is observed within the
Chlamydia
organisms. In
addition, the presence of heavy, acute inflammation may cause
cellular obscuring and degeneration, rendering the fine cytoplas-
mic details incomprehensible. Cellular degenerative changes,
on the other hand, can cause intracytoplasmic structures that
may mimic chlamydial inclusions. It must be appreciated that
cytoplasmic degenerative changes may occur in the presence of
C. trachomatis
infection also, but they per se are not sufficient
for a diagnosis.
Intracytoplasmic aggregates of minute elementary bodies
occurring within the metaplastic cells are the earliest discernible
feature of
C. trachomatis
infection. These may undergo degen-
eration with small, pinhead structures surrounded by a halo
that is thin-walled (Fig. 7.64). These intermediate forms may
be prominent and give the infected cell a "moth-eaten" appear-
ance. A careful study of such cells often shows clumps of elemen-
tary bodies also.52 At times the intracytoplasmic aggregates of
elementary bodies can condense and produce distinctly iden-
tifiable intracytoplasmic nebular inclusions.125 These are large,
homogeneous or finely granular structures with ill defined and
indistinct walls. Ultrastructurally, nebular inclusions contain the
Chlamydia
organisms. The
Chlamydia
organisms can be identified
121
previous page 123 ComprehensiveCytopathology 1104p 2008 read online next page 125 ComprehensiveCytopathology 1104p 2008 read online Home Toggle text on/off