Antimicrobial Resistance In Community Research Articles

Risk Factors for Colonization With Multidrug-Resistant Bacteria in Urban and Rural Communities in Kenya: An Antimicrobial Resistance in Communities and Hospitals (ARCH) Study.

Colonization with antimicrobial-resistant bacteria increases the risk of drug-resistant infections. We identified risk factors potentially associated with human colonization with extended-spectrum cephalosporin-resistant Enterobacterales (ESCrE) in low-income urban and rural communities in Kenya. Fecal specimens, demographic and socioeconomic data were collected cross-sectionally from clustered random samples of respondents in urban (Kibera, Nairobi County) and rural (Asembo, Siaya County) communities between January 2019 and March 2020. Presumptive ESCrE isolates were confirmed and tested for antibiotic susceptibility using the VITEK2 instrument. We used a path analytic model to identify potential risk factors for colonization with ESCrE. Only 1 participant was included per household to minimize household cluster effects. Stool samples from 1148 adults (aged ≥18 years) and 268 children (aged <5 years) were analyzed. The likelihood of colonization increased by 12% with increasing visits to hospitals and clinics. Furthermore, individuals who kept poultry were 57% more likely to be colonized with ESCrE than those who did not. Respondents' sex, age, use of improved toilet facilities, and residence in a rural or urban community were associated with healthcare contact patterns and/or poultry keeping and may indirectly affect ESCrE colonization. Prior antibiotic use was not significantly associated with ESCrE colonization in our analysis. The risk factors associated with ESCrE colonization in communities include healthcare- and community-related factors, indicating that efforts to control antimicrobial resistance in community settings must include community- and hospital-level interventions.

Long-term impact of fluoroquinolone-sparing strategies for empirical treatment of acute uncomplicated cystitis among ambulatory patients.

Background:Acute uncomplicated cystitis is common among outpatients and frequently leads to antibiotic prescriptions, making urinary tract infections (UTIs) an important area for antimicrobial stewardship initiatives. Infectious Disease Society of America (IDSA) guidelines promote alternative agents in place of fluoroquinolones for acute uncomplicated cystitis. Despite IDSA guidance, adherence to the guideline remains low in the United States (US). Several studies have described interventions to improve guideline-concordant prescribing for UTIs. However, the long-term sustainability and impact of fluoroquinolone (FLQ)-sparing strategies on community antimicrobial resistance and treatment outcomes are unknown. The objectives of this study were to characterize current antibiotic prescribing patterns, treatment failures and Escherichia coli resistance rates in a setting which instituted FLQ sparing strategies for UTIs in 2007.Methods:Retrospective cohort study of women aged ⩾ 18 diagnosed with acute uncomplicated cystitis based on International Classification of Diseases, 10th Revision (ICD-10) codes were included. Data were abstracted for ambulatory visits over a 6-month period, January 2018 to June 2018, at a large urban health care system. Treatment decisions were made by individual providers, and data were analyzed retrospectively. Nitrofurantoin (NFT) resistance was obtained from the institutional antibiogram and patient-level data. Treatment failure was defined as the need for a different antibiotic for UTI within 28 days of the original prescription.Results:NFT was the most frequently prescribed antibiotic (n = 386, 71.6%) of empiric antibiotic prescriptions for UTIs. FLQs comprised 4.6% of all antibiotic prescriptions (n = 25). Treatment failure rate was 2.3% in patients treated with NFT. Urine culture was ordered for only 26.8% of patients. Among the small group of patients with cultures ordered, E. coli remained 98.5% susceptible to NFT.Conclusions:This study is the first to report significantly low rates (4.6%) of FLQ prescribing for acute uncomplicated cystitis. Treatment failure rate was low with empiric NFT. Increased NFT resistance among E. coli was not observed at the institution or among the subset of patients with E. coli positive urine cultures. These findings support current IDSA treatment guidance for uncomplicated cystitis.

Monitoring the exposure and emissions of antibiotic resistance: Co-occurrence of antibiotics and resistance genes in wastewater treatment plants.

The COVID-19 pandemic has brought new momentum to 'wastewater-based epidemiology' (WBE). This approach can be applied to monitor the levels of antibiotic-resistant genes (ARGs), which in terms are used to make inferences about the burden of antimicrobial resistance (AMR) in human settlements. However, there is still little information about temporal variability in ARG levels measured in wastewater streams and how these influence the inferences made about the occurrence of AMR in communities. The goal of this study was hence to gain insights into the variability in ARG levels measured in the influent and effluent of two wastewater treatment plants in The Netherlands and link these to levels of antibiotic residues measured in the same samples. Eleven antibiotics were detected, together with all selected ARGs, except for VanB. Among the measured antibiotics, significant positive correlations (p > 0.70) with the corresponding resistance genes and some non-corresponding ARGs were found. Mass loads varied up to a factor of 35 between days and in concomitance with rainfall. Adequate sampling schemes need to be designed to ensure that conclusions are drawn from valid and representative data. Additionally, we advocate for the use of mass loads to interpret levels of AMR measured in wastewater.

One Health Surveillance of Antimicrobial Resistance Phenotypes in Selected Communities in Thailand.

Integrated surveillance of antimicrobial resistance (AMR) using the One Health approach that includes humans, animals, food, and the environment has been recommended by responsible international organizations. The objective of this study was to determine the prevalence of AMR phenotypes in Escherichia coli and Klebsiella species isolated from humans, pigs, chickens, and wild rodents in five communities in northern Thailand. Rectal swabs from 269 pigs and 318 chickens; intestinal contents of 196 wild rodents; and stool samples from 69 pig farmers, 155 chicken farmers, and 61 non-farmers were cultured for E. coli and Klebsiella species, which were then tested for resistance to ceftriaxone, colistin, and meropenem. The prevalence of ceftriaxone-resistant E. coli and Klebsiella species in pigs, chickens, rodents, pig farmers, chicken farmers, and non-farmers was 64.3%, 12.9%, 4.1%, 55.1%, 38.7%, and 36.1%, respectively. Colistin resistance in pigs, chickens, rodents, pig farmers, chicken farmers, and non-farmers was 41.3%, 9.8%, 4.6%, 34.8%, 31.6%, and 24.6%, respectively. Meropenem resistance was not detected. The observed high prevalence of AMR, especially colistin resistance, in study food animals/humans is worrisome. Further studies to identify factors that contribute to AMR, strengthened reinforcement of existing regulations on antimicrobial use, and more appropriate interventions to minimize AMR in communities are urgently needed.

Access, use and disposal of antimicrobials among humans and animals in Wakiso district, Uganda: a qualitative study

BackgroundInappropriate use of antimicrobials in both humans and animals is a key driver of antimicrobial resistance (AMR). In addition, human behaviours such as poor disposal of antimicrobials in the environment can increase their exposure to microbes which can impact on humans and animals. However, evidence on access, use and disposal of antimicrobials for humans and animals at community level in Uganda is limited. This study therefore explored access, use and disposal of antimicrobials among humans and animals in Wakiso district, Uganda.MethodsA qualitative study was conducted that involved focus group discussions (FGDs) and key informant interviews (KIIs). Participants of the FGDs were community health workers (CHWs) and farmers involved in animal husbandry, while key informants included: officials from the Ministry of Health; Ministry of Agriculture, Animal Industry and Fisheries; human and animal health professionals; district health officials; and members of the national AMR surveillance committee. Twelve FGDs were held (8 for CHWs and 4 for farmers) while 15 KIIs were conducted. Thematic analysis in NVivo (version 12) was performed.ResultsFive main themes emerged from the study: access to antimicrobials in humans; access to antimicrobials in animals; use of antimicrobials in humans; use of antimicrobials in animals; and disposal of antimicrobials. Community members mainly accessed antimicrobials for humans from public health facilities such as government health centres, as well as private facilities, including drug shops and clinics. Antimicrobials for animals were obtained from veterinary practitioners and drug shops (both for humans and veterinary). Examples of inappropriate use of antimicrobials in both humans and animals was evident, such as sharing antibiotics among household members, and giving human-prescribed antimicrobials to food-producing animals as growth promoters. While some CHWs returned unused antimicrobials to public health facilities for proper disposal, community members mainly disposed of antimicrobials with general household waste including dumping in rubbish pits.ConclusionsThere is a need to increase awareness among the population on proper access, use and disposal of antimicrobials for both humans and animals. Development of a drug disposal system at community level would facilitate improved waste management of antimicrobials. Together, these measures would help prevent the rate of progression of AMR in communities.

How accurate is presumptive Chlamydia trachomatis treatment? A 6-month clinical audit of a walk-in sexual health service.

Background Chlamydia trachomatis (chlamydia) is highly prevalent and is an important sexually transmitted infection as it can lead to increased risk of HIV seroconversion; and if left untreated, can cause infertility in women. Clinical guidelines recommend treating chlamydia presumptively when presenting symptomatically; however, clinicians are now questioning this due to increasing prevalence of antimicrobial resistance. Methods To determine the accuracy of presumptive chlamydia treatment practices at a walk-in sexual health service in regional Australia, we audited all same-day screen and treat presentations prescribed azithromycin over a 6-month period in 2018. Results A total of 325 cases were included in the analysis. Over half (54%) the presentations returned negative pathology for all pathogens investigated. One quarter (25%) of presentations were positive for chlamydia, and (4%) reported a dual infection. A further one fifth (20%) were negative for chlamydia but positive for another pathogen. More symptomatic males than females returned positive pathology for chlamydia (8% vs 4%). Conclusions While presumptive treatment is recommended in the current guidelines, our findings indicate this resulted in over-treatment. Considering the increasing resistance patterns for Mycoplasma genitalium, which include azithromycin, presumptive treatments need to balance immediate client care needs against long-term community antimicrobial resistance outcomes. This internal audit provided a feedback mechanism to the walk-in sexual service, enabling modification of practices to provide more precise, individual clinical care within the bounds of current STI guidelines, while balancing wider the objectives of antimicrobial stewardship.

Spatial Exposure of Agricultural Antimicrobial Resistance in Relation to Free-Ranging Domestic Chicken Movement Patterns among Agricultural Communities in Ecuador.

The use of antimicrobial growth promoters in chicken farming has been commonly associated with high levels of antimicrobial resistance (AMR) in humans. Most of this work, however, has been focused on intensive large-scale operations. Intensive small-scale farming that regularly uses antibiotics is increasing worldwide and has different exposure pathways compared with large-scale farming, most notably the spatial connection between chickens and households. In these communities, free-ranging backyard chickens (not fed antibiotics) can roam freely, whereas broiler chickens (fed antibiotics) are reared in the same husbandry environment but confined to coops. We conducted an observational field study to better understand the spatial distribution of AMR in communities that conduct small-scale farming in northwestern Ecuador. We analyzed phenotypic resistance of Escherichia coli sampled from humans and backyard chickens to 12 antibiotics in relation to the distance to the nearest small-scale farming operation within their community. We did not find a statistically significant relationship between the distance of a household to small-scale farming and antibiotic-resistant E. coli isolated from chicken or human samples. To help explain this result, we monitored the movement of backyard chickens and found they were on average 17 m (min-max: 0-59 m) from their household at any given time. These backyard chickens on average ranged further than the average distance from any study household to its closest neighbor. This level of connectivity provides a viable mechanism for the spread of antimicrobial-resistant bacteria and genes throughout the community.

Mycoplasma genitalium Antimicrobial Resistance in Community and Sexual Health Clinic Patients, Auckland, New Zealand

Our retrospective study compared genotypic antimicrobial resistance in Mycoplasma genitalium–positive specimens collected from 48 community and 33 sexual health clinic (SHC) patients. Macrolide resistance was similar in community (75%) and SHC (76%) patients. We observed no significant difference in fluoroquinolone resistance between community (19%) and SHC (27%) patients (p = 0.66).

Antimicrobial susceptibility patterns among community and health care acquired carbapenem resistant Enterobacteriaceae, in a tertiary care hospital of Lahore.

To compare the disk susceptibility pattern of healthcare acquired carbapenem-resistant enterobacteraceae with that of community-acquired isolates and their associated clinical presentations. The cross-sectional study was conducted at the Department of Microbiology, Combined Military Hospital, and the Institute of Dentistry, Lahore, Pakistan, from November 2017 to July 2018. Patients with positive carbapenem-resistant enterobacteraceae cultures from clinical specimens were included. All the isolates were identified through conventional methods and standard biochemical tests. Antibiotic susceptibility testing was performed by Kirby Bauer Disk Diffusion method on Muller Hinton Agar plates. Data was analysed using SPSS 23. Of the 123 isolates identified, 97(79%) were healthcare acquired and 26(21%) were community-acquired. Statistically significant susceptibility patterns (p<0.001) of community acquired isolates were observed against cefoperazone-sulbactum and amikacin, while a low significance was observed with gentamycin (p<0.05). Significant results were obtained in case of colistin against both the groups (p<0.001). There was low antimicrobial resistance in community acquired carbapenem-resistant enterobacteraceae isolates.

2328. Community-Onset Invasive Bacterial Infections in Infants Under 3 Months–10 Years of Experience in Auckland, New Zealand

BackgroundSerious infections remain the leading cause of death in the first year of life. Sepsis in neonatal intensive care units is well described but infants with bacterial infections presenting from the community has not previously been described in New Zealand. Recent studies suggest an increasing incidence of Staphylococcus aureus and Streptococcus pyogenes in New Zealand pediatric populations. It is, therefore, important to understand the unique pattern of infections seen in the infant population in New Zealand as this may impact on empiric management.MethodsA retrospective study (2007–2017) including infants aged 8 to 90 days presenting with clinically significant infection and positive culture from a sterile site. Cases were identified from laboratory database and ICD discharge codes, enabling data collection and analysis.Results192 cases were identified from two major hospitals in Auckland. This represented an incidence of invasive bacterial infections of 129/100,000 live births. Escherichia coli (40%) and Streptococcus agalactiae (22%) were the commonest pathogens. Streptococcus pyogenes and Staphylococcus aureus caused 14% and 12% of bacteremias respectively. Pacific island infants had the highest rates of infection (255/100,000) as did those from deprived backgrounds.Conclusion Escherichia coli and Streptococcus agalactiae are the commonest causative organisms in community-onset infant sepsis in Auckland.Rates of invasive bacterial infections in this age group are higher than reported in other industrialized countries (including published data from the USA), with Staphylococcus aureus and Streptococcus pyogenes being the most disproportionate. Our study demonstrates the increased risk of invasive Staphylococcus aureus and Streptococcus pyogenes in New Zealand, even at this early age, and this impacts on empiric antibiotic prescribing and management of infant sepsis in New Zealand. The risk of invasive infection is highest in Pacific and Māori infants and those from deprived backgrounds.A small number of multi-resistant organisms were present in this age group, prior to antibiotic exposure, illustrating that rising rates of community antimicrobial resistance will need to be considered even when prescribing for infants.Disclosures All authors: No reported disclosures.

Investigating the impact of poverty on colonization and infection with drug-resistant organisms in humans: a systematic review

BackgroundPoverty increases the risk of contracting infectious diseases and therefore exposure to antibiotics. Yet there is lacking evidence on the relationship between income and non-income dimensions of poverty and antimicrobial resistance. Investigating such relationship would strengthen antimicrobial stewardship interventions.MethodsA systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed, Ovid, MEDLINE, EMBASE, Scopus, CINAHL, PsychINFO, EBSCO, HMIC, and Web of Science databases were searched in October 2016. Prospective and retrospective studies reporting on income or non-income dimensions of poverty and their influence on colonisation or infection with antimicrobial-resistant organisms were retrieved. Study quality was assessed with the Integrated quality criteria for review of multiple study designs (ICROMS) tool.ResultsNineteen articles were reviewed. Crowding and homelessness were associated with antimicrobial resistance in community and hospital patients. In high-income countries, low income was associated with Streptococcus pneumoniae and Acinetobacter baumannii resistance and a seven-fold higher infection rate. In low-income countries the findings on this relation were contradictory. Lack of education was linked to resistant S. pneumoniae and Escherichia coli. Two papers explored the relation between water and sanitation and antimicrobial resistance in low-income settings.ConclusionsDespite methodological limitations, the results suggest that addressing social determinants of poverty worldwide remains a crucial yet neglected step towards preventing antimicrobial resistance.

Complex narratives of health, stigma and control: Antimicrobial resistance screening among non-hospitalized refugees

Antimicrobial resistance (AMR) is often presented as a major public health problem globally. Screening for AMR usually takes place in clinical settings. Recent developments in microbiology stimulated a series of studies focusing on AMR in communities, and particularly in travelers (any mobile individual), which was argued to be important for identifying potential public health risks. Against this background, microbiologists have become interested in non-hospitalized refugees as one of the traveler groups. However, this attention to refugees has provoked some professional debates on potential stigmatization of refugees as dangerous “others”. To contribute to these debates, and to explore the idea of AMR screening of non-hospitalized refugees from different perspectives, we conducted a qualitative study among four groups of stakeholders who were chosen because of their associations with potential microbiological screening: microbiologists, public health physicians, public health nurses, and refugees. The study took place in a Dutch city from June to August 2016 and had 17 participants: five microbiologists, two public health nurses, four public health physicians, and six refugees. While microbiologists and public health physicians demonstrated a de-contextualized biomedical narrative in arguing that AMR screening among non-hospitalized refugees could be important for scientific research as well as for AMR prevention in communities, public health nurses displayed a more contextualized narrative bringing the benefits for individuals at the center and indicating that screening exclusively among refugees may provoke fear and stigmatization. Refugees were rather positive about AMR screening but stressed that it should particularly contribute to their individual health. We conclude that to design AMR prevention strategies, it is important to consider the complex meanings of AMR screening, and to design these strategies as a process of co-production by diverse stakeholders, including the target populations.

Ceftriaxone-induced immune hemolytic anemia as a life-threatening complication of antibiotic treatment of ‘chronic Lyme disease’

‘Chronic Lyme disease’ is a controversial condition. As any hard evidence is lacking that unresolved systemic symptoms, following an appropriately diagnosed and treated Lyme disease, are related to a chronic infection with the tick-borne spirochaetes of the Borrelia genus, the term ‘chronic Lyme disease’ should be avoided and replaced by the term ‘post-treatment Lyme disease syndrome.’ The improper prescription of prolonged antibiotic treatments for these patients can have an impact on the community antimicrobial resistance and on the consumption of health care resources. Moreover, these treatments can be accompanied by severe complications. In this case report, we describe a life-threatening ceftriaxone-induced immune hemolytic anemia with an acute kidney injury (RIFLE-stadium F) due to a pigment-induced nephropathy in a 76-year-old woman, who was diagnosed with a so-called ‘chronic Lyme disease.’

Trends of Increasing Antimicrobial Resistance in Community Acquired infections- a Case Study of Enteric Fever and Health Implications.

Trends of Increasing Antimicrobial Resistance in Community Acquired infections- a Case Study of Enteric Fever and Health Implications.

Nasopharyngeal swabs of school children, useful in rapid assessment of community antimicrobial resistance patterns in Streptococcus pneumoniae and Haemophilus influenzae

ObjectivesThe present study evaluates the feasibility of rapid surveillance of community antimicrobial resistance (AMR) patterns of Streptococcus pneumoniae and Haemophilus influenzae in India using nasopharyngeal swabs (NPSs) of school children. It compares the AMR data obtained with that of invasive and nasopharyngeal (NP) isolates studied previously. No one has done such surveillance since our study so we decided to publish and more clearly demonstrate the feasibility of the methodology we did. Study Design and SettingThis community-based, cross-sectional, cluster sample study had seven centers; each had two sites distant to them. Two hundred sixty school children per center were enrolled. NP swabbing was performed and isolates identified as S. pneumoniae and H. influenzae at each center were sent to reference laboratories. ResultsFrom January to December 2004, 1,988 NP swabs were processed; 776 S. pneumoniae and 64 H. influenzae were isolated. The AMR patterns for S. pneumoniae to co-trimoxazole varied, with sensitivity as low as 6% in Mumbai, 29% in Chennai and Vellore, and 100% in Delhi and Lucknow. For H. influenzae, sensitivity rates to co-trimoxazole ranged from 22% to 62%. The AMR patterns for both bacteria in the present study with data from invasive and NP isolates studied earlier were similar. ConclusionThe study demonstrates that it is practical and feasible to rapidly assess the AMR patterns of both S. pneumoniae and H. influenzae in NPSs of school children in different geographic locations all over India.

Antimicrobial resistance in community and nosocomial Escherichia coli urinary tract isolates from Chennai, South India in 2007

Escherichia coli are the commonest cause of community and nosocomial urinary tract infection (UTI). Antibiotic treatment is usually empirical relying on susceptibility data from local surveillance studies. We therefore set out to determine levels of resistance to 9 commonly used antimicrobial agents amongst all urinary isolates obtained over a 12 month period. Methods: Antimicrobial susceptibility to ampicillin, amoxicillin/clavulanate, cephalexin, cefpodoxime, norfloxacin, amikacin, nitrofurantoin, trimethoprim and imipenem was determined for 14,678 E. coli urinary isolates obtained from community and hospitalised patients in Chennai, South India. Results: Imipenem was the most active agent (100% susceptible), followed by nitrofurantoin and amikacin (94% each). High rates of resistance to ampicillin (82%) and co-trimoxazole (76%), often in combination with norfloxacin were observed in both sets of isolates. Although 65% of the isolates exhibited resistance to multiple drug classes, resistance to cefpodoxime, indicative of extended spectrum β-lactamase production, was observed in 40% of community and 60% of nosocomial isolates. Conclusion: With the exception of nitrofurantoin, resistance to agents commonly used as empirical oral treatments for UTI was extremely high. Levels of resistance to trimethoprim and ampicillin render them unsuitable for empirical use. Continued surveillance and investigation of other oral agents for treatment of UTI in the community is required

Antimicrobial resistance in community and nosocomial Escherichia coli urinary tract isolates, London 2005 – 2006

BackgroundEscherichia coli is the commonest cause of community and nosocomial urinary tract infection (UTI). Antibiotic treatment is usually empirical relying on susceptibility data from local surveillance studies. We therefore set out to determine levels of resistance to 8 commonly used antimicrobial agents amongst all urinary isolates obtained over a 12 month period.MethodsAntimicrobial susceptibility to ampicillin, amoxicillin/clavulanate, cefalexin, ciprofloxacin, gentamicin, nitrofurantoin, trimethoprim and cefpodoxime was determined for 11,865 E. coli urinary isolates obtained from community and hospitalised patients in East London.ResultsNitrofurantoin was the most active agent (94% susceptible), followed by gentamicin and cefpodoxime. High rates of resistance to ampicillin (55%) and trimethoprim (40%), often in combination were observed in both sets of isolates. Although isolates exhibiting resistance to multiple drug classes were rare, resistance to cefpodoxime, indicative of Extended spectrum β-lactamase production, was observed in 5.7% of community and 21.6% of nosocomial isolates.ConclusionWith the exception of nitrofurantoin, resistance to agents commonly used as empirical oral treatments for UTI was extremely high. Levels of resistance to trimethoprim and ampicillin render them unsuitable for empirical use. Continued surveillance and investigation of other oral agents for treatment of UTI in the community is required.

An overview of emerging community based antimicrobial resistance

The development of community antimicrobial resistance should not surprise any budding microbiologist. Bacteria are highly adaptable and mutations are acquired or selected in response to any number of stresses. In the 21st century the major ?stressor? is profligate human and veterinary antibiotic use, and inappropriate antimicrobial use in food and agricultural sectors. Worldwide, resistance in the community has been well described in many bacterial species. In this overview, we focus on community resistance in three bacterial species ? Streptococcus pneumoniae, Staphylococcus aureus and Neisseria gonorrhoeae. In all three human antibiotic use provides the greatest selection pressure.

Introduction: Progress towards meeting the challenges in clinical microbiology and infectious diseases

With their elusive epidemiology, infectious diseases present new threats and increasingly complex challenges for healthcare systems. Ecological changes, global warming and the massive increases in movements of people and foodstuffs around the globe facilitate the dispersion of microbial pathogens. Emerging infections as well as increasing antimicrobial resistance in community- and hospital-acquired infections demand close monitoring and continuous revision of diagnosis, management and control strategies.

Laboratory testing policies and their effects on routine surveillance of community antimicrobial resistance.

To investigate the effects of laboratory testing policies, particularly selective testing, rule-based reporting and isolate identification, on estimates of community antimicrobial resistance. Antibiotic resistance estimates were analysed from an all-Wales dataset for approximately 300 000 community isolates of common pathogens. Selective testing policies were often associated with markedly increased resistance, particularly for second-line testing. Site-specific testing tended to yield variant resistance estimates for eye and ear isolates. Estimates from rule-based reporting deviated markedly from test-result-based reporting. Urinary isolates reported as Escherichia coli showed greater susceptibility than those reported as undifferentiated urinary 'coliforms'. The proportion of isolates tested for an antibiotic by a laboratory was a useful indicator of selective testing in this dataset. Selective testing policies had invariably been applied where the proportion of isolates of a species tested against an antibiotic was <90%. As this proportion fell with increasingly selective policies, divergence from pooled-all-Wales non-selective estimates tended to increase, with a bias to increased resistance. Selective testing, rule-based reporting and urinary coliform identification policies all had significant effects upon resistance estimates. Triage based upon the proportion of isolates tested seemed a useful tool in assigning analysis resources. Where <20% of isolates were tested, selective policies with inherent bias to increased resistance were common, the low number of isolates gave high potential sampling errors, and little confidence could be placed in the resistance estimate. Where 20-90% of isolates were tested, detailed analysis sometimes revealed resistance estimates that might be usefully retrieved. Where >/=90% of isolates were tested, there was no evidence of selective testing, and inter-laboratory variation in estimates appeared to be safely ascribable to other effects, e.g. methodology or real variation in resistance levels.