Infection by Chlamydia,Gardenella and Ureaplasma. Dr. Mohammad Shakeeb, MD Specialist in clinical pathology/Microbiology and immunology

CHLAMYDIAL INFECTIONS

Chlamydiae that infect humans are divided into three species, Chlamydia trachomatis. Chlamydia (Chlamydophila) pneumoniae. Chlamydia (Chlamydophila) psittaci. All Chlamydiae exhibit similar morphologic features, share a common group antigen, and multiply in the cytoplasm of their host cells by a distinctive developmental cycle.

lack mechanisms for the production of metabolic energy and cannot synthesize adenosine triphosphate (ATP). Chlamydiae are obligate intracellular parasites. Chlamydiae possess a heat-stable, family-specific antigen that is an essential component of the cell membrane lipopolysaccharide. Species and type-specific protein antigens also exist.

Chlamydiae have a unique developmental life cycle, with an intracellular growth, or replicative form, the reticulate body (RB), and an extracellular, metabolically inert, infective form, the elementary body (EB). Structurally, the chlamydial EB closely resembles a gram-negative bacillus; however, its cell wall lacks a peptidoglycan layer.

Chlamydiae possess shared group (genus)– specific antigens. Species-specific or serovar-specific antigens are mainly outer membrane proteins. There are different serovars of C trachomatis; these include A, B, Ba, C–K, and L1–L3.

CHLAMYDIA TRACHOMATIS CHLAMYDIA TRACHOMATIS Is the most common cause of sexually transmitted disease in the United States, and in trachoma-endemic regions of the Middle East, sub-Saharan Africa, and Asia, it is the primary infectious cause of blindness. The disorder is endemic in more than 50 countries. Estimates indicate that more than 3 million people are affected, with over a third having progressed to blindness

TRACHOMA CHLAMYDIA TRACHOMATIS GENITAL INFECTIONS AND INCLUSION CONJUNCTIVITIS CHLAMYDIA TRACHOMATIS AND NEONATAL PNEUMONIA LYMPHOGRANULOMA VENEREUM

 TRACHOMA It is a chronic keratoconjunctivitis that begins with acute inflammatory changes in the conjunctiva and cornea and progresses to scarring and blindness. The C trachomatis serovars A, B, Ba, and C are associated with clinical trachoma.

Clinical Findings Classic trachoma is an important cause of blindness in areas where public sanitation is inadequate and personal hygiene poor. The disease is due to repeated infections of the conjunctiva, resulting in a pathologic sequence over time. follicular conjunctivitis Subepithelial scarring (entropion). contraction of the scar resulting in turning inward of the eyelid (entropion).

(trichiasis) Rubbing of the eyelashes on the cornea (trichiasis) with subsequent corneal injury, and corneal scarring with opacification and reduced vision. Typically, acute infection is transmitted among children via fingers, fomites, and probably flies Most children become chronically infected within a few years of birth. Conjunctival scarring usually becomes evident by the second or third decade of life, and blindness can occur anywhere from 10–40 years after the first infection.

 CHLAMYDIA TRACHOMATIS GENITAL INFECTIONS AND INCLUSION CONJUNCTIVITIS. C trachomatis serovars D–K cause sexually transmitted diseases, especially in developed countries, and may also produce infection of the eye (inclusion conjunctivitis). In sexually active men, C trachomatis causes nongonococcal urethritis and, occasionally, epididymitis. In women, C trachomatis causes urethritis, cervicitis, and pelvic inflammatory disease, which can lead to sterility and predispose to ectopic pregnancy.

Proctitis and proctocolitis may occur in men and women, although these infections appear to be most common in men who have sex with men. Up to 50% of nongonococcal urethritis (men) or the urethral syndrome (women) is attributed to chlamydiae and produces dysuria, nonpurulent discharge, and frequency of urination. Genital secretions of infected adults can be self-inoculated into the conjunctiva, resulting in inclusion conjunctivitis, an ocular infection that closely resembles acute trachoma. The newborn acquires the infection during passage through an infected birth canal.

Probably 20–60% of infants of infected mothers acquire the infection. with 15–20% of infected infants manifesting eye symptoms and 10–40% manifesting respiratory tract involvement. Inclusion conjunctivitis of the newborn begins as a mucopurulent conjunctivitis 7–12 days after delivery. It tends to subside with erythromycin or tetracycline treatment or spontaneously after weeks or months. It is essential that chlamydial infections be treated simultaneously in both sex partners and in offspring to prevent reinfection.

Tetracyclines (eg, doxycycline) are commonly used in non- gonococcal urethritis and in non-pregnant infected women. Azithromycin is effective and can be given to pregnant women. Systemic therapy should be used for inclusion conjunctivitis because topical therapy may not cure the eye infections or prevent respiratory disease.

 CHLAMYDIA TRACHOMATIS AND NEONATAL PNEUMONIA Of newborns infected by the mother, 10–20% may develop pneumonia 2–12 weeks after birth. Affected newborns have striking tachypnea, a characteristic paroxysmal staccato cough, an absence of fever, and eosinophilia. Consolidation of lungs and hyperinflation can be seen on radiographs.

The diagnosis should be suspected if pneumonitis develops in a newborn who has inclusion conjunctivitis and can be established by isolation of C trachomatis from respiratory secretions. In such neonatal pneumonia, an immunoglobulin M (IgM) antibody titer to C trachomatis of 1:32 or more is considered diagnostic. Oral erythromycin for 14 days is recommended; systemic erythromycin is effective treatment in severe cases.

 LYMPHOGRANULOMA VENEREUM Lymphogranuloma venereum is a sexually transmitted disease caused by C trachomatis and is characterized by suppurative inguinal adenitis. It is most common in tropical climates C trachomatis serovars L1–L3. Several days to several weeks after exposure, a small, evanescent papule or vesicle develops on any part of the external genitalia, anus, rectum, or elsewhere. The lesion may ulcerate, but usually it remains unnoticed and heals in a few days.

The regional lymph nodes enlarge and tend to become matted and painful. In men, inguinal nodes are most commonly involved The overlying skin often turns purplish as the nodes suppurate and eventually discharge pus through multiple sinus tracts. In women and in homosexual men, the perirectal nodes are prominently involved. proctitis and a bloody mucopurulent anal discharge During the stage of active lymphadenitis, there are often marked systemic symptoms.

fibrosis, lymphatic obstructionrectal strictures. Unless effective antimicrobial drug treatment is given at that stage, the chronic inflammatory process progresses to fibrosis, lymphatic obstruction, and rectal strictures. elephantiasis The lymphatic obstruction may lead to elephantiasis of the penis, scrotum, or vulva. fistula formation The chronic proctitis of women or homosexual men may lead to progressive rectal strictures, rectosigmoid obstruction, and fistula formation.

LABORATORY DIAGNOSIS Specimens for detection of C. trachomatis are determined by the type of disease suspected

Screening women at risk for genital C. trachomatis infection has been shown to decrease the rate of pelvic inflammatory disease, thus preventing subsequent reproductive sequelae. epithelial Demonstration of C trachomatis by smear or culture requires the collection of epithelial (not inflammatory) cells from the site of infection (conjunctiva, urethra, cervix). specially treated cells inclusions Culture is carried out in specially treated cells in which chlamydial inclusions are detected by immunofluorescence. Results require incubation for 3 to 7 days. Direct fluorescent antibody (DFA) and immunoassay methods have also been developed.

nucleic acid amplification (NAA) tests All these methods have now been replaced by the newest generation of nucleic acid amplification (NAA) tests. They are rapid, sensitive, specific for genital infections. Urine is a suitable specimen although less sensitive than direct genital samples. Culture or DFA are now reserved for pharyngeal and rectal specimens which for NAA tests might generate false positives. Nucleic acid amplification methods for genital Chlamydia infection are now combined with parallel tests for N gonorrhoeae.

Serodiagnostic methods have limited use. difficulty of distinguishing current from previous infection detection of IgM antibodies against C trachomatis is helpful in cases of infant pneumonitis. useful in the diagnosis of LGV, Chlamydial serology is also useful in the diagnosis of LGV, where a single high complement fixation antibody titer (higher than 1:32) or a fourfold rise supports a presumptive diagnosis. The most satisfactory method for diagnosis of LGV is isolation of an LGV strain of C trachomatis from aspirated lymph nodes or tissue biopsies.

TREATMENT Strains of C trachomatis are sensitive to tetracyclines, macrolides and related compounds, and some fluoroquinolones. Azithromycin is the first-line therapy Azithromycin is the first-line therapy because it is given as a single oral dose for non-LGV C trachomatis infection. Doxycycline is also a first-line Doxycycline is also a first-line drug and preferred for LGV. Erythromycin and fluoroquinolones are alternatives., a single dose of azithromycin For trachoma, a single dose of azithromycin is the treatment of choice.

Gardnerella Gardnerella vaginalis is a thin, gram-variable rod or coccobacillus Over the years, this organism, in its association with bacterial vaginosis. Catalase is not produced, and cells are nonmotile. Growth is best observed after 48 hours of incubation in a 5% CO2-enriched atmosphere. Colonies are small and exhibit β-hemolysis on media containing rabbit or human blood.

Clinical Manifestations and Pathogenesis This organism is associated with bacterial vaginosis but is not the cause. It has been found in the blood of patients with postpartum fever and can cause infection in newborns. G. vaginalis is a part of the anorectal flora of healthy adults of both sexes, as well as of children. It is part of the endogenous vaginal flora of women of reproductive age.

Laboratory Diagnosis Diagnosis of bacterial vaginosis does not require culture. The diagnosis is made by: clue cells Direct examination of vaginal secretions for the presence of clue cells (epithelial cells covered with bacteria on the cell margins) and Small gram-negative rods and coccobacilli. The absence of lactobacilli (gram positive thin rods). a pH greater than 4.5. Fishy amine odor after addition of 10% potassium hydroxide (KOH) to the secretions.

Antimicrobial Susceptibility Metronidazole is the drug of choice for bacterial vaginosis. Systemic infection due to G. vaginalis may be treated with ampicillin because this organism has not been found to produce β-lactamase.

GENITAL MYCOPLASMAS Mycoplasmas are the smallest free-living organisms. They are pleomorphic, ranging from spherical cells 0.2 μm in diameter to filaments 0.1 μm wide by 1–2 μm long. Most are facultative anaerobes that replicate by binary fission. Mycoplasmas are unique among bacteria because they have no cell wall. They are unable to synthesize cell wall precursors, and they require cholesterol and related sterols for membrane synthesis

The potential pathogens, M. pneumoniae and the genital mycoplasmas (Mycoplasma hominis, Mycoplasma genitalium, Ureaplasma urealyticum, and Ureaplasma parvum), Other mycoplasmas are part of the normal human flora, primarily of the respiratory and genitourinary tracts.

Epidemiology Ureaplasma species can be found colonizing the vagina and cervix in 40%–80% of adult women. M. hominis can be found in 21%–53% of women. The frequency in males appears to be lower. Prevalence studies for M. genitalium are infrequent in the literature, but it appears to be less common as a colonizer in asymptomatic individuals and is found with a frequency of around 1%.

Colonization of infants with genital mycoplasmas can occur during passage through the birth canal, but colonization appears to be temporary in many cases, and a lower rate of colonization has been noted in children. The increase in colonization by mycoplasmas after puberty indicates an association with sexual activity

Neonates can acquire infections due to Ureaplasma spp. and M. hominis hematogenously through the placenta or through an ascending infection, resulting in seeding of amniotic fluid.

Clinical Manifestations the presence of mycoplasma in the placental membranes or amniotic fluid is consistently associated with : chorioamnionitis, preterm birth. adverse perinatal outcomes associated with several neonatal disorders, including perinatal pneumonia and sepsis in preterm infants Both Ureaplasma spp. and M. hominis are associated with postpartum fever.

Ureaplasma spp. can cause urinary calculi and are a cause of nongonococcal urethritis (NGU) M. hominis has been related to both pelvic inflammatory disease (PID) and pyelonephritis and may have an association with bacterial vaginosis. M. genitalium has been linked to NGU in males only relatively recently, but it is now firmly established as a significant cause of the disorder and is the etiologic agent in approximately 25% of cases.

Among women, M. genitalium has shown an association with cervicitis, endometritis, PID, and tubal infertility.