Antimicrobial Strategies and Economic Considerations for Polymeric Medical Implants.

Healthcare acquired infections (HAI's) are a worldwide problem that can be exacerbated by surgery and the implantation of polymeric medical devices. The use of polymer based medical devices which incorporate antimicrobial strategies are now becoming an increasingly routine way of trying to prevent the potential for reduce chronic infection and device failure. There are a wide range of potential antimicrobial agents currently being incorporated into such polymers. However, it is difficult to determine which antimicrobial agent provides the greatest infection control. The economics of replacing current methods with impregnated polymer materials further complicates matters. It has been suggested that the use of a holistic system wide approach should to be developed around the implantation of medical devices which minimises the potential risk of infection. However, the use of such different approaches is still being developed. The control of such infections is important for individual patient health and the economic implications for healthcare services

Herpesviruses in Australian marsupials

© 2013 Kathryn Judith StalderHerpesviruses are ubiquitous, enveloped DNA viruses that have been identified worldwide in most vertebrate and in several invertebrate species. Within the Marsupialia, several different herpesvirus species have been detected across various macropodid species, and more recently in koalas and antechinus species. Infection may be subclinical, and the capacity to induce lifelong infection with periods of latency and intermittent reactivation is a feature common to all herpesviruses, although the mechanism by which this occurs varies according to the individual herpesvirus species. In macropodids, herpesviruses have been associated with outbreaks of disease and mortality, and clinical signs may include conjunctivitis, oral and/or cloacal ulceration, or sudden death associated with disseminated pathology including widespread visceral necrosis and inflammation. This study sought to evaluate the prevalence and significance of individual herpesvirus species in various free-living and captive populations of Australian marsupials. Swab samples from 397 marsupials principally including eastern grey kangaroos (Macropus giganteus), other members of the Macropodidae and the Potoroididae families, koalas (Phascolarctos cinereus), Tasmanian devil (Sarcophilus harrisii), common wombats (Vombatus ursinus) and bandicoot species were collected and a universal herpesvirus nested PCR protocol utilised to determine the prevalence of active herpesvirus infection in these animals. Serum neutralisation tests and PCR on tissue samples were also performed for some animals, and virological culture on wallaby fibroblast cells and newly developed wombat kidney cells was attempted for several of the novel herpesvirus species identified. Prevalence of active herpesvirus infection varied across the marsupial species, ranging from 0% in some of the wallaby species, to 25% in eastern grey kangaroos, 33.3% in koalas, 34% in Tasmanian devils and 45.5% in the common wombat. Seroprevalence of antibodies against macropodid herpesviruses-1 and -2 was also variable, from 0% prevalence in koalas and some of the wallaby species, 66.7% in common wombats and as high as 92% in the eastern grey kangaroo and 100% in the swamp wallaby. Sequencing of a conserved portion of the DNA polymerase gene identified seven novel herpesvirus species from six marsupial hosts, and phylogenetic analysis classified each of these novel herpesvirus species into their respective subfamily groups, namely the Alphaherpesvirinae (vombatid herpesvirus 3) and the Gammaherpesvirinae (macropodid herpesvirus 5, potoroid herpesvirus 1, dasyurid herpesvirus 2, vombatid herpesvirus 1, vombatid herpesvirus 2 and peramelid herpesvirus 1). Development of a wombat tissue cell culture facilitated the successful isolation of two of the novel wombat herpesviruses, vombatid herpesviruses-1 and -2, in addition to phascolarctid herpesvirus 1, a koala gammaherpesvirus that had not been previously isolated. Epidemiologic analysis was performed where permitted by sample size, and identified various factors in association with active herpesvirus infection. Results varied significantly between the different marsupial species evaluated, and likely reflect differences in the biology of the respective herpesvirus species, biological and ecological differences between marsupial hosts, and environmental factors. The significance of herpesvirus infections identified in marsupial hosts is discussed with respect to the clinical signs observed in infected animals, and the biological and ecological threats facing individual marsupial species including: ongoing habitat destruction as a result of urbanisation, logging and natural disasters; the effects of climate change; predation by introduced mammals; and concurrent diseases of ecological importance. Possible transmission routes for individual herpesvirus species are suggested and scope for further research discussed. This study has broadened the mammalian host range in which natural herpesvirus infections have been found and identified seven novel herpesvirus species. Whilst the significance of these herpesviruses remains unclear, the presence of subclinical infections in a high proportion of individuals suggests that these herpesvirus species are well adapted to their marsupial hosts, likely as a result of an extended period of coevolution, and that severe pathology is unlikely to occur in immunocompetent hosts. Studies investigating the effect of these herpesvirus infections in immunocompromised, immunonaïve or unnatural hosts may be required to determine their pathogenecity and characterise the risk they pose to marsupial populations. Herpesviruses identified in threatened marsupial species should be targeted for these further investigations, as the results of such research may be critical in informing the development and management of species recovery programs

Univariable analysis assessing select epidemiological variables as predictors for the presence of herpesvirus DNA in eastern grey kangaroos ^a.

<p>^a Reference levels are indicated by odds ratio of 1.0. Results highlighted in bold (log likelihood p ≤ 0.25) represent variables included in the initial multivariable model, with the exception of presence of pouch young/lactation as it is correlated with sex and thus excluded. Backward elimination of non-significant variables yielded no significant variables. Multivariable analysis was repeated including presence of pouch young/lactation as a variable instead of sex. Age was excluded from the model due to collinearity. In the final model (n = 42) only the absence of pouch young/lactation was identified as a significant factor (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#pone.0133807.t008" target="_blank">Table 8</a>). n/a = not applicable.</p><p>Univariable analysis assessing select epidemiological variables as predictors for the presence of herpesvirus DNA in eastern grey kangaroos <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#t004fn001" target="_blank">^a</a>.</p

Univariable analysis assessing select epidemiological variables as predictors for the presence of herpesvirus DNA in Tasmanian devils ^a.

<p>^a Reference levels are indicated by odds ratio of 1.0. Results highlighted in bold (log likelihood p ≤ 0.25) represent variables included in the initial multivariable model, with the exception of season as it was directly influenced by timing of management procedures, and therefore correlated with captive status and was thus excluded. In the final model (n = 50) only captivity was identified as a significant factor (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#pone.0133807.t008" target="_blank">Table 8</a>). n/a = not applicable.</p><p>Univariable analysis assessing select epidemiological variables as predictors for the presence of herpesvirus DNA in Tasmanian devils <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#t006fn001" target="_blank">^a</a>.</p

Electron micrographs of novel herpesviruses.

<p>Transmission electron microscopy was used to visualise herpesviruses in cultures of primary wombat kidney cells. Herpesvirus capsids (arrowheads) of VoHV-1 (A) and VoHV-2 (B) are shown. Bar = 100 nm.</p

Univariable analysis assessing select epidemiological variables as predictors for the presence of active herpesvirus infection in common wombats ^a.

<p>^a Reference levels are indicated by odds ratio of 1.0. Results highlighted in bold (log likelihood p ≤0.25) represent variables included in the initial multivariable model, with the exception of pouch young which was excluded due to zero prevalence of herpesvirus infection in females lactating/with pouch young. In the final model (n = 33) only age (adult/aged) and body condition score (≤ 2) were identified as significant factors (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#pone.0133807.t008" target="_blank">Table 8</a>). n/a = not applicable.</p><p>Univariable analysis assessing select epidemiological variables as predictors for the presence of active herpesvirus infection in common wombats <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#t007fn001" target="_blank">^a</a>.</p

Predicted amino acid alignment and phylogenetic tree of the novel marsupial herpesviruses.

<p>A: Alignment of the predicted amino acid sequence of a portion of the DNA polymerase gene of the novel marsupial herpesviruses, along with other herpesviruses from the three herpesvirus sub-families. B: Maximum likelihood tree generated from the alignment. Bootstrap values of 100 replicates are displayed on the tree branches. Novel herpesvirus species are underlined. Key: PaHV-2 = papiine herpesvirus 2 (AAN87165.1); SaHV-1 = saimiriine herpesvirus 1 (YP_003933809.1); HHV-1 = human herpesvirus 1 (NP_044632.1); MaHV-1 = macropodid herpesvirus 1 ([<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#pone.0133807.ref022" target="_blank">22</a>]); <u>VoHV-3 = vombatid herpesvirus 3 (novel sequence)</u>; PCMV = porcine cytomegalovirus (AF268042.1); HHV-6 = human herpesvirus 6A (NP_042931.1); HHV-4 = human herpesvirus 4 (YP_401712.1); HHV-8 = human herpesvirus 8 (ACY00400.1); SaHV-2 = saimiriine herpesvirus 2 (NP_040211.1); BHV-4 = bovine herpesvirus 4 (NP_076501.1); DaHV-1 = dasyurid herpesvirus 1 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#pone.0133807.ref013" target="_blank">13</a>]; <u>DaHV-2 = dasyurid herpesvirus 2</u> (novel sequence); MaHV-3 = macropodid herpesvirus 3 (ABO61861.1); <u>MaHV-5 = macropodid herpesvirus 5 (novel sequence). PeHV-1 = peramelid herpesvirus 1 (novel sequence</u>); PotHV-1 = potoroid herpesvirus 1 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#pone.0133807.ref010" target="_blank">10</a>]; <u>VoHV-1 = vombatid herpesvirus 1 (novel sequence)</u>; <u>VoHV-2 = vombatid herpesvirus 2 (novel sequence);</u> PhaHV-1 = phascolarctid herpesvirus 1 (AEX15649.1); PhaHV-2 = phascolarctid herpesvirus 2 (AFN66528.1); EHV-2 = equine herpesvirus 2 (NP_042605.1); CpHV-2 = caprine herpesvirus 2 (ADV92276.1).</p

Univariable analysis assessing select epidemiological variables as predictors for the presence of herpesvirus DNA in koalas ^a.

<p>^a Reference levels are indicated by odds ratio of 1.0. Results highlighted in bold (log likelihood p ≤ 0.25) represent variables included in the initial multivariable model, with the exception of season as the timing of sampling correlated with the location at which it occurred and was thus excluded. In the final model (n = 68) only the presence of <i>Chlamydia pecorum</i> was identified as a significant factor (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#pone.0133807.t008" target="_blank">Table 8</a>). n/a = not applicable.</p><p>Univariable analysis assessing select epidemiological variables as predictors for the presence of herpesvirus DNA in koalas <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0133807#t005fn001" target="_blank">^a</a>.</p