IntroductionAfrican swine fever (ASF) is an important disease of pigs in sub-Saharan Africa and Uganda and is threatening the pig population and agricultural economy of other continents. ASF virus (ASFV) can be transmitted from wild suids to domestic pigs through soft ticks of the Ornithodoros species. The aim of this study was to understand the relationship between domestic pigs’ O. moubata tick exposure and ASFV status.MethodsPigs were sampled from six abattoirs in the Kampala metropolitan area of Uganda from May 2021 through June 2022. Blood, serum, and tissue samples were collected. Serum was tested for antibodies against the rtTSGP1 salivary antigens of O. moubata ticks using an indirect ELISA assay. Blood and tissue samples from pigs were tested to detect ASFV using qPCR. Probability of tick exposure was categorized based on sample-to-positive ratio cut-off points.ResultsOut of 1,328 serum samples tested, there were 828 (62.3%) samples with a negligible probability; 369 (27.8%) with a medium probability; 90 (6.8%) with a high probability, and 41 (3.1%) with a very high probability of exposure to the O. moubata salivary antigen. There was a statistically significant association between the pigs’ O. moubata exposure and ASFV status with a higher proportion of pigs having a very high probability of infection if they were ASFV positive by blood, tonsil, and lymph nodes.DiscussionThese results suggested that tick exposure was associated with ASFV transmission in Uganda. There were ASFV qPCR positive pigs that had no O. moubata exposure as well, which highlights that pig-to-pig and indirect contact transmission still play a significant role. This work highlights the need for further work in Uganda to investigate these transmission factors related to the O. moubata tick and ASFV transmission.

Introduction:In Uganda, pig production is an important source of livelihood for many people and contributes to food security. African swine fever (ASF) is a major constraint to pig production in Uganda, threatening the food supply and sustainable livelihoods. Prevention of ASF primarily relies on good biosecurity practices along the pig value chain. Previous studies showed that biosecurity along the pig value chain and on farms in Uganda is poor. However, the biosecurity practices of pig farmers in ASF affected areas of Uganda and their opinions on on-farm ASF morbidity and mortality were previously not comprehensively characterized. The objectives of this study were to document pig farmers' experiences with ASF in their farms and to describe the pig biosecurity practices in districts of Uganda that were highly affected by ASF. Methods:A total of 99 farmers were interviewed in five districts. Data were collected by way of triangulation through farmer interviews, field observations during the farmer interviews, and a survey of key informants. However, farmer interviews were considered the primary source of data for this study. Farmers' biosecurity practices were scored using a biosecurity scoring algorithm. Results:Forty-one out of 96 (42.7%) farmers reported having pigs with ASF in the past 12 months. The level of pig farming experience (p = 0.0083) and herd size (p < 0.0001) were significantly associated with the reported occurrence of ASF. Overall, the biosecurity scores for the respondents were considered poor with 99% (98/99) scoring <70% and just one farmer obtaining a fair score of 72.2%. District (p = 0.0481), type of husbandry system (p = 0.014), and type of pig breed raised (p = 0.004) were significantly associated with farmer's biosecurity score. Conclusion:Continued farmer education on ASF and the importance of good biosecurity practices is necessary. More in-depth scientific inquiry into the factors influencing the biosecurity practices among pig farmers in Uganda is necessary.

BACKGROUND:African swine fever virus (ASFV) infections in Africa cause hemorrhagic disease in domestic pigs and is maintained by a sylvatic cycle in warthogs. It is endemic in Uganda, leading to significant economic losses. Previous studies performed in rural areas and in Kampala had differing diagnostic results. The purpose of this study was to provide a robust spatial, temporal, and diagnostic summary of pigs slaughtered in the greater Kampala metropolitan area over the course of one year. This study characterized 1208 to 1323 serum, blood, and tissue samples collected from pigs at six abattoirs in the greater Kampala metropolitan area of Uganda monthly from May 2021 through June 2022. Validated and standardized serologic and molecular diagnostics were used.RESULTS:Only 0.15% of pigs had detectable antibodies against ASFV, suggesting low survival rates or pre-clinical diagnosis. Yet, 59.5% of pigs were positive for ASFV DNA. Blood had the lowest detection rate (15.3%) while tonsil and lymph nodes had the highest (38% and 37.5%, respectively), spleen samples (31.5%) were in between. Agreement between sample types was fair to moderate overall. A significant seasonality of ASFV infections emerged with infections found predominately in the dry seasons. Spatial assessments revealed that the greater Kampala metropolitan area abattoirs have a catchment area that overlaps with Uganda's most pig dense regions.CONCLUSIONS:Pigs at greater Kampala metropolitan area abattoirs can be sentinels for acute disease throughout the pig dense region of Uganda, particularly in the dry seasons. The high prevalence detected suggests that pigs are sold in response to local reports of ASFV infections (panic sales). Serological surveillance is not useful, as very few pigs seroconverted in this study prior to slaughter. In contrast, tissue samples of pigs can be used to detect disease using qPCR methods.

Introduction:Uganda is a pork-producing country in East Africa. The African swine fever virus (ASFV) has had a devastating impact on the country's pig industry. The movements of pigs and pork are a major pathway of spreading ASFV. This study was done to describe the live pig supply chain within and through districts that are impacted by African swine fever (ASF) in Uganda.Methods:A pig farmer survey in districts known to have ASFV was done using a semi-structured questionnaire available in English and two local languages. In total, 99 farmers were interviewed across five districts. Farmers were conveniently and purposively selected by local government veterinary officials. An online key informant survey was also used to validate farmer responses.Results:Most farmers interviewed in all districts reported to source and sell most of their pigs from within their district the farm was in, although there was variation by district and pig type. In relation to pig type, 89.7% of farmers sourced sows, 80.0% sourced boars, and 96.4% sourced weaned pigs from the district where the farm was located. As for sales, 91.3% of farmers sold sows, 92.7% sold boars, 91.9% sold weaned pigs, and 92.2% sold market pigs in the district where the farm was located. There was also variation to whom pigs were sold and sourced by pig type.Conclusion:This information is useful when planning the scale and focus of disease control programs based on animal movement. This study revealed that pig disease control programs can be targeted to smaller regions. Furthermore, there is a need for farmers and pig traders to be educated on and adhere to veterinary regulations of animal movement and good biosecurity practices to reduce disease spread when purchasing and selling pigs from known ASFV infected areas.

Non-judicious antimicrobial use (AMU) is a major driver of antimicrobial resistance (AMR). In human hospitals, cumulative antibiograms are often used by clinicians to evaluate local susceptibility rates and to select the most appropriate empiric therapy with the aim of minimizing inappropriate AMU. However, the use of cumulative antibiograms to guide empiric antimicrobial therapy in veterinary hospitals in the United States is limited, and there are no specific guidelines or standardized methods available for the construction of antibiograms in veterinary clinical settings. The objective of this methods article is to describe the approaches that were used to construct antibiograms from clinical samples collected from dogs seen at a veterinary teaching hospital. Laboratory data for 563 dogs for the period from 1 January 2015 to 31 December 2015 was utilized. We used the Clinical and Laboratory Standards Institute (CLSI) guidelines for use in the construction of the antibiograms in human healthcare settings as the basis for the veterinary antibiograms. One general antibiogram and antibiograms stratified by hospital section, the anatomic region of sample collection/by sample type, were created and the challenges encountered in preparing these antibiograms were highlighted. The approaches described could be useful in guiding veterinary antibiogram development for empiric therapy.

Blood samples were collected from pigs at six abattoirs in the Kampala, Uganda metropolitan area from May 2021 through June 2022, and tested for African swine fever virus. Thirty-one samples with cycle threshold values < 26 from pigs with different geographic origins, clinical and pathologic signs, and Ornithodoros moubata exposure underwent whole genome sequencing. The p72 gene was used to genotype the isolates, and all were found to be genotype IX; whole genome sequences to previous genotype IX isolates confirmed their similarity. Six of the isolates had enough coverage to evaluate single nucleotide polymorphisms (SNPs). Five of the isolates differed from historic regional isolates, but had similar SNPs to one another, and the sixth isolate also differed from historic regional isolates, but also differed from the other five isolates, even though they are all genotype IX. Whole genome sequencing data provide additional detail on viral evolution that can be useful for molecular epidemiology, and understanding the impact of changes in genes to disease phenotypes, and may be needed for vaccine targeting should a commercial vaccine become available. More sequencing of African swine fever virus isolates is needed in Uganda to understand how and when the virus is changing.

Antimicrobial resistance (AMR) is a global health crisis that threatens the health of humans and animals. The spread of resistance among species may occur through our shared environment. Prevention of AMR requires integrated monitoring systems, and these systems must account for the presence of AMR in the environment in order to be effective. The purpose of this study was to establish and pilot a set of procedures for utilizing freshwater mussels as a means of surveillance for microbes with AMR in Indiana waterways. One hundred and eighty freshwater mussels were sampled from three sites along the Wildcat Creek watershed in north-central Indiana. Specimens were evaluated for the presence of ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species), Escherichia coli, Campylobacter, and Salmonella species, and the isolates were tested for antimicrobial resistance. A total of 24 bacterial isolates were obtained from tissue homogenates of freshwater mussels collected at a site directly downstream from Kokomo, Indiana. Of these, 17 were Enterobacter spp., five were Escherichia coli, one was Pseudomonas aeruginosa, and one was Klebsiella pneumoniae. All isolates were resistant to three or more antimicrobial drug classes. Further work is necessary to determine the source of the bacterial species found in the mussels.

The increasing prevalence of antimicrobial-resistant bacterial infections has ushered in a major global public health crisis. Judicious or restricted antimicrobial use in animal agriculture, aiming to confine the use for the treatment of infections, is the most commonly proposed solution to reduce selection pressure for resistant bacterial strains and resistance genes. However, a multifaceted solution will likely be required to make acceptable progress in reducing antimicrobial resistance, due to other common environmental conditions maintaining antimicrobial resistance and limited executionary potential as human healthcare and agriculture will continue to rely heavily on antimicrobials in the foreseeable future. Drawing parallels from systematic approaches to the management of infectious disease agents and biodiversity loss, we provide examples that a more comprehensive approach is required, targeting antimicrobial resistance in agroecosystems on multiple fronts simultaneously. We present one such framework, based on nested biological units of antimicrobial resistance, and describe established or innovative strategies targeting units. Some of the proposed strategies are already in use or ready to be implemented, while some require further research and discussion among scientists and policymakers. We envision that antimicrobial resistance mitigation strategies for animal agriculture combining multiple tools would constitute powerful ecosystem-level interventions necessary to mitigate antimicrobial resistance.

Burkholderia pseudomallei is a Gram-negative bacterium that causes melioidosis, a disease of humans and animals. It is primarily transmitted through direct contact with contaminated soil and surface water. The epidemiology of this pathogen in Africa, including Uganda, is largely unknown. The objectives of this study were to estimate the seroprevalence of B. pseudomallei in pigs slaughtered in central Uganda and to identify potential hotspots for this pathogen in the country. A total of 1035 pig sera were analyzed for serological responses to B. pseudomallei with type A and type B LPS using OPS type A and OPS type B ELISAs. Of the 1035 samples, 75 (7.25%, 95% CI: 5.8–9%) were seropositive to the OPS-A ELISA using a two standard deviations (SD) cutoff and 19 (1.84%, 95% CI: 1.2–2.9%) at 3 SD. For the OPS-B ELISA, 93/1035 (8.99%, 95% CI: 7.4–10.9%) were seropositive at the 2 SD cutoff, and 28/1035 (2.71%, 95% CI: 1.9–3.9%) at the 3 SD cutoff. Pigs slaughtered in central Uganda were exposed to B. pseudomallei, and there is a higher seroprevalence in the rainy months. Public health awareness campaigns about melioidosis may be needed.

Escherichia coli (E. coli) is the most common Gram-negative pathogen isolated in human infections. Antimicrobial resistant (AMR) E. coli originating from dogs may directly or indirectly cause disease in humans. The objective of this study was to calculate the proportion of antimicrobial susceptible E. coli isolated from canine specimens submitted to the Indiana Animal Disease Diagnostic Laboratory and to identify temporal patterns of susceptibility among these isolates. Susceptibility data of 2,738 E. coli isolates from dogs from 2010 through 2019 were used in this study. Proportions of isolates susceptible to the various antimicrobials were calculated using SAS statistical software and the Cochran-Armitage trend test was used to investigate the temporal trends in susceptibility. A multivariable binary logistic regression model was built to investigate the association between host factors and AMR. Overall, 553/2,738 (20.2%) of the isolates were susceptible to 17 of the 27 antimicrobials examined. Of the 2,638 isolates examined for amikacin susceptibility, 2,706 (97.5%) were susceptible, 2,657/2,673 (99.4%) isolates were susceptible to imipenem, and 2,099/2,670 (78.6%) were susceptible to marbofloxacin. A significant decreasing trend in susceptibility was observed for amoxicillin-clavulanic acid (P<0.0001), ampicillin (P<0.0001), Cefazolin (P<0.0001), ceftazidime (P = 0.0067), chloramphenicol (P<0.0001), and orbifloxacin (P = 0.008). The overall percentage of AMR isolates (isolates not susceptible to at least one antimicrobial) was 61.7% (1,690/2,738) and 29.3% (801/2,738) of isolates were multidrug resistant. Multivariable regression analyses showed significant associations between AMR and age (P = 0.0091), breed (P = 0.0008), and sample isolation site/source (P<0.0001). The decreasing trend in the proportion of isolates susceptible to several beta-lactam antimicrobials suggests that resistance of Escherichia coli in dogs to these antimicrobials could be increasing in Indiana. The decreasing trend in susceptibility to these drugs could be due to selection pressure from antimicrobial use.

To improve judicious antimicrobial use (AMU) in food animals in the United States, all feed additives that were medically important antimicrobials were moved from over the counter to Veterinary Feed Directive in 2017. This action required a change in behavior of producers’ AMU practices. Because emotions are important aspects of behavior, several behavioral interventions have targeted people’s emotions as means of effecting change. Hence, understanding and incorporating the emotional experiences of producers towards current AMU practices can be a starting point to making future behavioral changes that could reduce the emergence of antimicrobial resistance challenge. Between June 2017 and March 2018, seven focus group meetings of Tennessee (TN) beef and dairy cattle producers were conducted to evaluate producers’ emotional views regarding responsible AMU in TN cattle. Sixty-two TN cattle producers participated and emotively expressed the following: (1) deep connections to animals in ways that improve animal and public health; (2) pride in their quality of products; (3) distress that consumers misconceive their AMU practices as indiscriminate; and (4) recommended that producers be more transparent about their AMU practices and the public improve their awareness for detecting marketers’ deceptive product labels that take advantage of public ignorance. Knowledge of these producers’ emotions would help educators target more successful behavioral change campaigns, improving stewardship in AMU practices among producers.

BACKGROUND:In recent years, there has been an increased awareness of antimicrobial resistance in both animals and humans, which has triggered concerns over non-judicious antimicrobial use. In the United States, antimicrobial use in food-producing animals for growth promotion or improved feed efficiency is perceived as non-judicious. To facilitate judicious antimicrobial use, the United States Food and Drug Administration implemented the Veterinary Feed Directive, effective from January 1, 2017. Interventions, such as the VFD, designed to ensure the judicious use of antimicrobials among cattle producers may be more effective if the factors that inform and influence producer AMU practices are addressed. The specific objectives of this study were to determine the following among Tennessee beef cattle producers: (1) the most common drivers for using antimicrobials, (2) the perceived alternatives to antimicrobials, (3) the knowledge and perceptions regarding antimicrobial resistance, and (4) the preferred avenues for receiving information on prudent antimicrobial use. A total of 5 focus group meetings with beef producers were conducted in East, Middle, and West Tennessee. Each focus group was video recorded and thematic analysis was performed using NVivo.RESULTS:The factors that producers considered to drive antimicrobial use were the type of cattle operation, disease and animal welfare, economic factors, veterinarian consultation, producer's experience and peer support, Veterinary Feed Directive, and perceived drug efficacy. Vaccination, proper nutrition, and other good management practices were considered alternatives to antimicrobial use. To encourage vaccine use among small producers, participants suggested packaging vaccines into smaller quantities. Antimicrobial resistance was perceived to be a problem affecting animal and public health. Participants suggested additional education for cattle producers on the prudent use of antimicrobials as a measure for improving antimicrobial use. The veterinarian, producer associations and meetings, and county extension agents emerged as trusted avenues for channeling information on prudent antimicrobial use to cattle producers.CONCLUSIONS:Several factors drive antimicrobial use among cattle producers in Tennessee. Participants generally perceived their antimicrobial use to be discreet and only when necessary. More awareness of drivers for the development of antimicrobial resistance and continuing education on prudent antimicrobial use is needed for Tennessee beef producers.

Indiscriminate antimicrobial use (AMU) is a factor contributing to antimicrobial resistance (AMR). The objectives of this study were to (1) identify factors influencing AMU practices of veterinary clinicians at The University of Tennessee Veterinary Medical Center (UTVMC), (2) analyze the clinicians' preferential choices of antimicrobials, and (3) evaluate their perceptions, opinions, and concerns regarding AMU and AMR. A total of 121 clinicians were surveyed. Among the 62 respondents, culture and susceptibility test results and pressure from clients were the most and least important factors in their antimicrobial prescription decision-making, respectively. Compared to clinicians who obtained their veterinary degree from 1970 to 1999, those who graduated from 2000 to 2009 and 2010-2016 were 3.96 (P = 0.034) and 5.39 (P = 0.01) times less concerned about AMR, respectively. There is a critical need to increase awareness about judicious AMU practices among clinicians, increase emphasis about AMR in the present veterinary curriculum, and implement antimicrobial stewardship program (AMS) in this institution. Educational activities in combination with awareness campaigns and the stewardship programs could be used to improve AMU practices at this hospital. More client education on AMR is needed.

Since January 1, 2017, the United States Food and Drug Administration (FDA) has fully implemented the Veterinary Feed Directive (VFD) final rule aimed at facilitating the judicious use of medically important antimicrobials in food-producing animals. The objective of this study was to identify the common perceptions of Tennessee (TN) cattle producers regarding the VFD. We used a combination of focus groups and survey questionnaires to explore TN cattle producers’ perceptions regarding the VFD. Preliminary findings from seven focus groups of 62 producers were used in the development of the questionnaire sent both online and in-print to rest of cattle producers in TN. The beef focus group participants perceived the VFD: to be a top-down policy; to have led to unregulated access to in-feed antimicrobials; a regulation that has limited the producers’ ability to prevent disease and leading to economic losses; to negatively affect small producers; and to be affected by challenges related to prescription writing and disposal of un-used medicines. The dairy focus group participants perceived the VFD as unnecessary and burdensome, to have affected small producers, and introduced additional costs. Among the survey questionnaire respondents, 35 (15.4%) beef producers and 6 (13.6%) dairy producers respectively were not familiar at all with the VFD. Forty-eight (21.1%) beef producers and 11 (25%) dairy producers were slightly familiar with VFD. Gender was significantly associated (P = 0.02) with the beef producers’ belief in the usefulness of the VFD. Similarly, for dairy producers, herd size was significantly associated (P = 0.002) with their perceptions regarding the usefulness of the VFD. The findings of this study could inform future VFD policy review processes. More awareness regarding the VFD and its benefits is needed among both beef and dairy producers in TN.

BackgroundInappropriate antimicrobial use (AMU) is a key modifiable factor that leads to the development of antimicrobial resistance (AMR). The objectives of this study were to determine the following among Tennessee beef cattle producers: (1) the opinions on factors driving AMU (2) opinions on alternatives to antimicrobials, (3) the knowledge and perceptions regarding AMU and AMR, and (4) the preferred avenues for receiving information on prudent AMU. A survey questionnaire was made available to participants both in print and online from January 26, 2018 through May 11, 2018. The questions targeted the producers' demographics and their AMU practices; factors driving producer's choice of antimicrobials; perceptions, opinions and concerns about AMU and AMR in cattle production. Ordinal logistic regression was used to test for associations between the captured demographic information and producers' degree of concern about AMR.ResultsOverall, 231 beef producers responded to all or some of the survey questions. More than 60% of the participants mentioned that they kept up-to-date written records on antimicrobial purchases and AMU. Regarding extra-label use, 169 (84.1%) of the 201 respondents did not practice extra-label AMU. Profitability of the beef operation was a key factor influencing the decisions of many producers to use antimicrobials for disease management and prevention on their farms. Of the 228 producers who completed the question on the rating of their degree of concern about AMR, 50 (21.9%) reported that they were very concerned about AMR, 133 (58.3%) were moderately concerned, and 36 (15.8%) reported that they were not concerned about AMR. Nine producers (4%) did not rate their degree of concern about AMR because they were not familiar with what antimicrobial resistance meant. The inferential analyses suggested that younger beef producers were significantly less concerned about AMR when compared to the older ones (P=0.019). Regarding avenues for receiving information on prudent AMU, no single medium was most preferred by all the respondents.ConclusionsThere is a need to promote the use of written antimicrobial treatment protocols among beef producers in Tennessee. Continued training for beef producers on infection prevention and control and prudent AMU is needed.

Nonjudicious antimicrobial use (AMU) and inadequate antimicrobial stewardship are known modifiable factors driving the occurrence of antimicrobial resistance (AMR). A mixed methods approach using a combination of focus groups and survey questionnaires was used to explore the AMU practices of Tennessee (TN) dairy cattle producers. Specifically, the objectives of the study were to determine the following: (1) the most common drivers for using antimicrobials, (2) perceived alternatives to antimicrobials, (3) knowledge of and perceptions regarding AMR, (4) and the appropriate avenues for receiving information on prudent AMU. Two focus groups were conducted, one in July 2017 and the other in March 2018. The questionnaire was simultaneously made available to participants both in print form and online from January 26, 2018, through May 11, 2018. Twenty-three dairy producers participated in the focus groups and 45 responded to the survey. Eight (18.6%) producers never used bacterial culture and sensitivity testing (C/S) to select antimicrobials, more than half (25 producers (58.1%)) sometimes used C/S, four (9.3%) used C/S about half the time, five (11.6%) most of the time, and one (2.3%) always used C/S. The most common drivers for using antimicrobials were disease and animal welfare, pathogen surveillance, economic factors, veterinarian recommendation, producer’s experience and judgment, drug attributes, and the Veterinary Feed Directive. Good management practices, vaccination, use of immunomodulatory products, and use of appropriate technology for early disease detection were considered alternatives to AMU. Four (9.1%) dairy producers were very concerned about AMR, 27 (61.4%) moderately concerned, and 10 (22.7%) not concerned. The veterinarian was considered to be a trusted source of information on prudent AMU. Use of C/S test results for antimicrobial selection is widespread among TN dairy producers. There is a need to popularize/promote selective dry cow therapy among TN dairy producers.

Background. Antimicrobial drugs in veterinary medical practice are primarily prescribed for the purposes of maintaining or improving health and increasing productivity. However, their value is being eroded by antimicrobial resistance (AMR). Indiscriminate use of antimicrobial drugs is suggested as one of the modifiable factors contributing to the development of AMR. To reduce indiscriminate use and to improve antimicrobial use, veterinary practices are encouraged to adopt good stewardship practices. Therefore, the objectives of this study were: to identify factors influencing clinician decisions to begin using antimicrobials as well as the choice of antimicrobials used at The University of Tennessee Veterinary Medical Center (UTVMC); to evaluate the practices, perceptions, opinions and concerns of veterinary clinicians at UTVMC concerning antimicrobial use, antimicrobial stewardship, and AMR. Methods. This study’s protocol was approved by the University of Tennessee Knoxville IRB for the Protection of Human Subjects in Research. Survey software was used to send a questionnaire to 121 eligible participants, where all were UTVMC faculty with clinical appointments and house officers. Cumulative logit models were fitted to investigate associations between categorical explanatory variables and ordinal response variables. Results. A response rate of 51.24% was achieved. Of the 62 respondents, 47 (75.81%) reported that bacteriological culture and antimicrobial susceptibility test results were extremely important in their antimicrobial prescription decision-making. Thirty-two (51.61%) respondents believed antimicrobials are being over-prescribed. The cephalosporin class was the most preferred antimicrobial class, while the lincosamide class was the least preferred. From the multivariable cumulative logit model, year of graduation from veterinary school (P = 0.034) and clinicians’ primary patient load (P = 0.009) were significantly associated with clinicians’ degree of concern about AMR. Conclusions and clinical relevance. The findings suggest a need for more awareness about AMR among veterinary clinicians. Improvements in antimicrobial stewardship are needed, especially among veterinary clinicians who graduated after 1999. Educational practices that target modification of antimicrobial prescription practices of veterinary clinicians would likely improve a Good Stewardship Practice (GSP) mindset. GSP is important in prolonging the efficacy of currently available antimicrobial drugs.