Parachlamydia acanthamoebae

Similar to other Chlamydiales, it is commonly found in two developmental stages, the first of which is the elementary body, which is the infective stage of the organism.[2] The other developmental stage it is commonly found in is the reticulate body, which is its metabolically active dividing stage.[9] However, Parachlamydia acanthamoebae and bacteria within the family Parachlamydiaceae can also be found a crescent body stage, which has been found to be a more efficient infective stage for the organism.[2] The elementary body has been found to be the most dominant stage this organism resides in once within an amoeba.[9] Studies found that the elementary bodies were mainly found in vacuoles, and as incubation time continued, the organism continued to replicate within the vacuole.[2] Researchers were able to show that Parachlamydia acanthamoebae is mainly found in the reticulate body stage while it is present in the cytoplasm.[9] This organism was only in the crescent body stage after a significant incubation time, and even then it was only found within vacuoles and not in the cytoplasm of the infected amoeba.[9] The only stage that this organism was proven to be in outside of the amoeba was the elementary stage.[9]

The Parachlamydia acanthamoebae begins its life cycle by entering the amoeba by phagocytosis in either the elementary stage or the crescent stage.[9] During this time, it begins to acquire the endosomal and lysosomal integral glycoprotein, designated Lamp-1.[2] Once within the amoebic cell, the organism changes its morphology to the reticulate body, where it then replicates by binary fission. Once in this stage, they can then leave the vacuole, and enter the cytoplasm.[9] During the time that the amoeba is infected, it begins to increase significantly in size.[9] This can be attributed to the increase in vacuoles in the cytoplasm that contain Parachlamydia acanthamoebae.[9] Replication of the organism continues until the amoeba lyses.[9]

Parachlamydia acanthamoebae has been shown to infect and multiply in simian and human cells.[10] Experimental models were able to demonstrate that this bacterium can enter, replicate, and lyse in human macrophages and pneumocytes.[11] A study in 2003 examined P. acanthamoebae’s ability to enter and survive in human macrophages.[12] These researchers collected human macrophages and placed these cells on growth plates in conjunction with P. acanthamoebae.[12] The results for this study showed that after an 8-hour time period, eighty percent of the macrophages incubated with live P. acanthamoebae were infected with an average of 3.8 bacteria and were located in vacuoles.[12] Their results also shows that the P. acanthamoebae cells continued to replicate within the macrophages, and eventually caused apoptosis.[12] Although research on this bacterium and how it can affect humans is minimal, there are several studies that link P. acanthamoebae to the onset of illnesses in humans.[10] The diseases that have been connected to this bacterium primarily affect the respiratory system.[10] Research shows that pneumonia, bronchitis, and atherosclerosis are among the most common complications that have arisen from ingestion of this bacterium by humans.[10] Although these studies show that P. acanthamoebae is linked to human diseases, researchers have not been able to isolate this bacteria directly from a human.[10]

In a study that assessed whether different bacteria were present in a water treatment plant, P. acanthamoebae had been found in the river water that fed the water treatment plant that was used in the experiment.[13] These researchers looked at the different steps within the water treatment facility, including sand filtration, followed by ozonation, and finally granular activated carbon filtration, also known as GAC.[13] They found this bacterium within a biofilm around the GAC.[13] From this finding, the researchers concluded that this bacteria was able to bypass the ozonation step of the water treatment, which means it passed through this step inside an undetected Acanthamoeba species.[13] This shows that it can protect itself from the harsh conditions in the treatment facility, or that the bacteria itself is resistant to ozonation.[13]

P. acanthamoebae has also been implicated as an abortive agent when it is present in Swiss cattle.[14][15] Researchers in Switzerland randomly selected 235 late term abortions in cattle during the breeding season of 2003 and 2004 and used PCR to detect the presence of this bacterium in the sample.[14] They found that 43 of the 235 cases tested positive for the presence of P. acanthamoebae.[14] Further examination of these positive cases showed that 25 of the 43 cases showed necrotizing placentitis and 35 of the 43 cases were confirmed positive by the presence of the antibody that was elicited against the bacterial infection.[14] Not only is this detrimental to the cattle infected with the bacteria, but it also poses a zoonotic risk to humans because handling this aborted material could facilitate the contraction of bronchitis or pneumonia.[14][15]

P. acanthamoebae has shown that it is affected by the presence of antibiotics when it is inside of the host.[16] One study analyzed two strains of P. acanthamoebae, the Hall's Coccus strain and the BN9 strain, and tested their response to a number of common antibiotics.[16] They cultured Acanthamoeba polyphaga, a common endosymbiotic host of P. acanthamoebae, in a PYG medium and added 20 μl of P. acanthamoebae to the growth plates.[16] A portion of the amoeba were left both drug-free and free of P. acanthamoebae as a control to measure amoebal viability in the medium.[16] Another portion was only subjected to antibiotics.[16] The purpose of this is to serve as a control to assess if the amoeba itself displayed any antibiotic toxicity.[16] In this experiment, they found that Acanthamoeba polyphaga was not effected by any of the tested antibiotics.[16] They found that most of the beta-lactam antibiotics, vancomycin, and fluoroquinolones had no effect on the growth of P. acanthamoebae.[16] Because of this, it can be inferred that these two strains of P. acanthamoeba are resistant to these antibiotics.[16] However, both of these strains showed inhibited growth when in the presence of macrolides, doxycycline, aminoglycosides, and rifampin.[16] These results show that P. acanthamoebae shows susceptibility and resistance to antibiotics that is very different from other closely related microbes, such as Chlamydia trachomatis or Chlamydophila pneumoniae.[16]