Several studies have reported the detection by PCR of the DNA of Parachlamydia in the mononuclear

cells of sputa and bronchoalveolar lavage samples from patients with bronchitis (6, 8). Other studies have also indicated that P. acanthamoebae infection occurs in a mouse model of severe pneumonia (9), and might be responsible for community or hospital-acquired pneumonia in HIV-infected patients (10, 11) and in organ transplant recipients receiving immunosuppressive therapy (13). Thus, it seems likely that P. acanthamoebae is becoming, or will anti-PD-1 antibody become, widespread along with Acanthamoeba, and should be considered a potential human pathogen associated with lower respiratory tract infections, similar to other pathogenic chlamydia such as C. pneumoniae and C. psittaci (10, 12–17). It is known that P. acanthamoebae develops inclusions

with specific developmental cycles, including an infectious form termed the EB to gain entry into the host cells, a metabolically-active form termed the RB (similar to pathogenic chlamydiae), and additionally a crescent body similar to EB which is specific to Maraviroc clinical trial environmental chlamydiae (18). It has also been proposed that P. acanthamoebae can enter and multiply within human macrophages, pneumocytes and lung fibroblasts (19–21). However, methods to accurately monitor the number of bacteria and CFU are insufficient. Whether other protozoa in the natural environment, such as ciliates and myxamoebae, can support the growth and survival of P. acanthamoebae remains undetermined, and the growth properties of bacteria in mammalian cells are also yet to be fully elucidated. Hence, the present authors

have previously established the AIU assay in order to quantify the growth of P. acanthamoebae in culture (22). In the present study, the host range of P. acanthamoebae in various protozoan and mammalian cells has been assessed. P. acanthamoebae Bn9 (VR-1476) was purchased from the ATCC (Manassas, VA, USA). The bacteria were propagated in Acanthamoeba according to methods described previously (22). Briefly, the infected cells were harvested and disrupted by freeze-thawing. After centrifugation at 180 ×g for 5 min to remove cell debris, the bacteria were concentrated Fludarabine mw by high-speed centrifugation at 3500 ×g for 30 min. The bacterial pellet was resuspended in sucrose-phosphate-glutamic acid buffer containing 0.2 M sucrose, 3.8 mM KH2PO4, 6.7 mM Na2HPO4 and 5 mM L-glutamic acid (pH 7.4), and then stored at −80°C until needed. The number of infective progeny of P. acanthamoebae was determined by the AIU assay, using co-culture with amoebae as described below (22). Briefly, each sample containing viable P. acanthamoebae was serially diluted from 10°–10−7 with PYG medium and incubated with A.