Isolation of Chlamydia using McCoy cells and Buffalo green monkey cells

Recent developments in the laboratory diagnosis of chlamydial infections

There are two main approaches to diagnosing infections by Chlamydia and Chlamydophila spp. in mammals and birds. The first involves the direct detection of the agent in tissue or swab samples, while the second involves the serological screening of blood samples for the presence of anti-chlamydial antibodies. Ultimately, the test that is used is dependent on the types of samples that are submitted to the diagnostic laboratory for analysis. The present paper gives an overview on methodologies and technologies used currently in diagnosis of chlamydial infections with emphasis on recently developed tests. The performance characteristics of individual methods, such as the detection of antigen in smears and in pathological samples, the isolation of the pathogen, various antibody detection tests and DNA-based methods utilising conventional and real-time PCR, as well as DNA microarray technology are assessed, and specific advantages and drawbacks are discussed. Further, a combination of a specific real-time PCR assay and a microarray test for chlamydiae is proposed as an alternative reference standard to isolation by cell culture.

High-yield culture and purification of Chlamydiaceae bacteria

Research on intracellular bacteria of the family Chlamydiaceae, and the diseases they cause, requires large amounts of infectious elementary bodies (EB). We describe an approach that maximizes the generation of Chlamydia pneumoniae, Chlamydia trachomatis, Chlamydia abortus, or Chlamydia pecorum EBs in several replication cycles over approximately 10 days or more in a saturated equilibrium monolayer cell culture system. Buffalo Green Monkey Kidney (BGMK) cells, Human Epidermoid Carcinoma-2 (HEp-2) cells, or mouse McCoy cells were tested. BGMK cells best supported C. pneumoniae replication when cultivated in Iscove's Modified Dulbecco's Medium. From day 1 to day 9 after inoculation, C. pneumoniae genomes per ml culture medium increased from 10(5.1) to 10(8.6) in BGMK, from 10(5.6) to 10(8.1) in HEp-2, and remained at 10(5.2) in McCoy cell cultures. Three-month pre-inoculation maintenance of BGMK cells in different culture media did not influence C. pneumoniae yields. Inoculation at multiplicities of infection (MOI) of 10 or higher and supplementation of the cell culture medium on day 7 after inoculation with 0.1% glucose enhanced C. pneumoniae EB yields in harvested cell culture medium. For purification, EBs in medium were concentrated by sedimentation, followed by low-speed centrifugation for removal of host cell nuclei, and by step-gradient centrifugation of the supernatant in a 30% RenoCal-76-50% sucrose step-gradient. Extensive sonication increased yield and infectivity of chlamydial EB. The combined method typically produced from 1000 ml infected BGMK culture medium 10 ml homogeneous, single-cell, highly infectious EB stock containing approximately 5x10(11) C. pneumoniae genomes equivalent to 4-5x10(11) inclusion forming units.

Dynamics of the development of Chlamydophila psittaci inclusions in epithelial and fibroblast host cells

The development of Chlamydophila psittaci (formerly Chlamydia psittaci, avian strains) inclusions in fibroblast L-929 and epithelial BGM cell lines was studied along the bacterial growth cycle using a BGM cell-adapted strain in the presence or absence of cycloheximide and cycloheximide + polyethylene glycol. Evolution of the inclusions was determined in terms of their number and size at 24, 30, 36, 48 and 54 h after infection. Significant differences in the chlamydial growth were found between both host cells, throughout the study. Higher numbers of inclusions (P < 0.05) were observed in L cells while larger inclusions (P < 0.01) were found in BGM cells. In both fibroblast and epithelial cells, inclusions showed a significant (P < 0.001) increase in size at the later times studied. Free extracellular chlamydial particles were noticed at 48 and 54 h post-infection (p.i.) in infected L cells, and at 54 h p.i. in BGM cells. Addition of cycloheximide or cycloheximide + polyethylene glycol had no significant effect on the number of inclusions or their size. The results suggest that host cell characteristics and innate compatibility between Chlamydophila strain and host cell are more important than host cell adaptation for the development of the microorganism.

Comparison of Giemsa and fluorescent monoclonal antibody staining of inoculated cell cultures for diagnosis of Chlamydia trachomatis

Three methods of isolation and identification of Chlamydia trachomatis inclusions in cell monolayers were compared: Giemsa staining followed by darkfield microscopy of cycloheximide treated Buffalo green monkey kidney monolayers (BGM), fluorescent monoclonal antibody staining of cycloheximide treated BGM and of HeLa 229 monolayers. In an unselected group of 895 patients with suspected chlamydial infections including contacts of symptomatic patients, significantly more positive chlamydia isolates were detected with immunofluorescent monoclonal antibody staining of BGM and HeLa 229 than with Giemsa staining followed by darkfield microscopy on BGM. However, there was no disparity between the 2 staining methods with specimens from 156 patients with untreated non-gonococcal urethritis. In all chlamydia positive specimens, significantly more inclusions were seen after BGM-immunofluorescence than after HeLa-immunofluorescence or BGM-Giemsa. The extra cost associated with immunofluorescence staining was justified by the time saved in scanning.

Comparison of Buffalo green monkey kidney cells and McCoy cells for the isolation of Chlamydia trachomatis in shell vial centrifugation culture

A total of 745 clinical specimens from patients attending hospitals and clinics in an area with a low prevalence of Chlamydia trachomatis were inoculated in parallel into shell vial cultures containing Buffalo green monkey kidney (BGM) and McCoy cells. The shell vial cultures were prepared in-house and were less than 5 days after seeding when inoculated. A total of 38 specimens (5%) were positive for C. trachomatis. In 36 of the cases, C. trachomatis was detected in both the BGM and McCoy vials. In two cases, C. trachomatis was detected in only the BGM vial. The BGM cells were more resistant to cytotoxicity and seemed to show more and larger inclusions than the McCoy cells. Furthermore, because the BGM cells displayed contact inhibition without the rounding and piling of cells that was encountered with the McCoy cells, they could be stored, ready to use, with an optical monolayer of cells, at 35 degrees C for at least 10 days.

Comparison of buffalo green monkey cells and McCoy cells for isolation of Chlamydia trachomatis in a microtiter system

A total of 1,229 urogenital samples of patients with sexually transmitted diseases and prostitutes were inoculated simultaneously in McCoy cells and Buffalo green monkey (BGM) cells by using a microtitration technique. BGM cells proved to be slightly more sensitive than McCoy cells, and they usually showed more and larger inclusions and were more resistant to cytotoxic substances in samples. The decrease in sensitivity as a result of mycoplasmal contamination was much more prominent in McCoy cells than in BGM cells.

Chlamydia trachomatis infection in late pregnancy: a prospective study

During a 1-year period, 3309 women were screened in pregnancy for Chlamydia trachomatis infection. A cervical swab was taken and chlamydial antigen was detected, using a monoclonal antibody ELISA technique, in 198 women (6%). The prevalence of chlamydial infection was high in women under 20 years (14.5%), single women (14.2%) and black women (16.8%). Binomial regression of these data estimates a relative risk of 2.9 for women under 20 years compared with women aged 25 and over. There was an interaction between race and marital status with a high risk in single white and single asian women (2.3, 4.5 respectively) but a similar risk in black single and black married women (3.0, 4.0 respectively). Parity and social class did not effect the prevalence of antigen carriage. There was no demonstrable effect of maternal antigen carriage on outcome of pregnancy, gestation or admission to neonatal unit. Infants of 174 antigen-positive mothers were followed-up. Tissue culture for Chlamydia trachomatis was positive in 43 (24%) infants. Complications occurred in 23 (53%): 17 had conjunctivitis, three had lower respiratory tract infection and three both complications. Amongst 131 chlamydia-negative infants, complications occurred in 21 (16%). Since this infection, in infants, responds promptly to erythromycin therapy, screening and treatment in pregnancy will convey little benefit in prevention of perinatal morbidity or perinatal mortality.

Chlamydia trachomatis infection in infants: a prospective study

In a prospective study of Chlamydia trachomatis infection in pregnancy, 198 mothers positive for chlamydial antigen were identified; the infants of 174 were followed for up to six months and C trachomatis was recovered in cell culture from 43 infants (25%). Conjunctivitis occurred in significantly more infants who were positive for C trachomatis (20 of 43, 47%) than in those who were negative (18 of 131, 14%). There were also significantly more lower respiratory tract infections among infants with positive cultures (six of 43, 14%, compared with three of 131, 2%). The chlamydial antigen enzyme linked immunosorbent assay (ELISA) was positive in 61 of 131 infants from whom C trachomatis was not recovered in cell culture. False positive results were usually associated with the isolation of Staphylococcus aureus from samples of pharyngeal aspirate. Our results confirm that C trachomatis infection is a common cause of neonatal conjunctivitis, and respiratory infection in the first few months of life, with an incidence of 8.2/1000 live births. Because the infection is easily treated by oral erythromycin, however, screening during pregnancy is not warranted.