A multicentre evaluation of the NG-test DetecTool OXA-23 for the rapid detection of OXA-23 carbapenemase directly from blood cultures

Objectives

A multicentre study evaluating NG-Test DetecTool OXA-23 for the detection of OXA-23 carbapenemase directly from positive blood cultures (PBCs).

Methods

The NG-Test DetecTool OXA-23 is an immunoassay that integrates a sample preparation device. We evaluated NG-Test DetecTool OXA-23 on 189 spiked and 126 clinical PBCs. The clinical samples' standard-of-care procedure consisted of bacterial identification from the first day of positivity by MALDI-TOF MS, conventional culture and antimicrobial susceptibility testing. The immunoassay results were verified molecularly. The strains used for the spiked samples consisted of well-characterized Acinetobacter baumannii and Proteus mirabilis strains.

Results

The NG-Test DetecTool OXA-23 was evaluated on 315 PBCs and revealed sensitivity of 100% (95% CI: 98.21%-100.00%) and specificity of 100% (95% CI: 96.73%-100.00%). It provided 204 true-positive results for OXA-23 in 196 bottles with carbapenem-resistant A. baumannii (CRAB) and 8 bottles with carbapenem-resistant P. mirabilis and also provided 111 true-negative results. There were no false-positive and no false-negative results. Among the 315 PBCs studied, 83 clinical blood cultures collected in the ICU of a Greek university hospital, which were tested prospectively, all yielded CRAB, and OXA-23 was correctly detected in all samples from the first day of positivity using the NG-Test DetecTool OXA-23.

Conclusions

The NG-Test DetecTool OXA-23 has exhibited excellent sensitivity and specificity for OXA-23 detection in PBCs and can provide valuable information for appropriate selection of antibiotic therapy and early implementation of infection control measures.

Multicenter study to assess the use of BL-DetecTool for the detection of CTX-M-type ESBLs and carbapenemases directly from clinical specimens

Antimicrobial resistance (AMR) is one of the major public health problems worldwide. Multiple strategies have been put in place to address this problem. One of them is the rapid detection of the mechanisms of resistance, such as extended-spectrum beta-lactamases (ESBLs) and/or carbapenemases. We conducted a multicenter study that included nine European centers for the assessment of prototypes of a novel lateral flow immunoassay-based device (BL-DetecTool) for a rapid detection of ESBL (NG-Test CTX-M-MULTI DetecTool) and/or carbapenemases (NG-Test CARBA 5 DetecTool) from Enterobacterales and Pseudomonas aeruginosa in positive urine, positive blood cultures, and rectal swabs. We performed a prospective analysis between January 2021 and June 2022, including overall 22,010 samples. Based on each hospital information, the sensitivity to detect CTX-M was 84%-100%, 90.9%-100%, and 75%-100% for urine, positive blood cultures, and enriched rectal swabs, respectively. On the other hand, the sensitivity to detect carbapenemases was 42.8%-100%, 75%-100%, and 66.6%-100% for urine, positive blood cultures, and enriched rectal swab, respectively. BL-DetecTool allows a rapid and reliable detection of ESBL and carbapenemases directly from urine, positive blood cultures, or enriched rectal swabs, being an easy technique to implement in the workflow of clinical microbiology laboratories.

IMPORTANCE

The assessed rapid assay to detect CTX-M beta-lactamases and carbapenemases directly from clinical samples can favor in the rapid detection of these mechanisms of resistance and hence the administration of a more adequate antimicrobial treatment.

Evaluation of VITEK® 2 AST cards (AST-N376 and AST-N397) for susceptibility testing of challenging Gram negatives

Due to the increasing diffusion of MDR/XDR Gram-negatives it is necessary to offer reliable antibiotic susceptibility testing (AST), which also include new drugs. Here we evaluated the performances of the VITEK®2 AST-N376 and the AST-N397 cards. A collection of 180 clinical Gram-negative bacteria, producing relevant resistance mechanisms, were tested using VITEK 2 and MERLIN, in parallel. Discrepancies between the 2 systems were solved by the reference broth microdilution method. The workflow timing of the VITEK®2 system was also assessed. Overall, the VITEK®2 cards proved to be reliable in determining AST for the molecules evaluated, even if compliance with ISO acceptance criteria for accuracy assessment was not reached for some combinations and showed a short hands-on time for panels preparation. In conclusion, VITEK®2 is a valid system that ensures accurate results for AST of the molecules evaluated in this study and speeds up the workflow in the laboratory of diagnostic microbiology.

Citrobacter freundii resistant to novel β-lactamase inhibitor combinations and cefiderocol, co-producing class A, B and D carbapenemases encoded by transferable plasmids

OBJECTIVES

To characterize a carbapenem-resistant Citrobacter freundii (Cf-Emp) co-producing class A, B and D carbapenemases, resistant to novel β-lactamase inhibitor combinations (BLICs) and cefiderocol.

METHODS

Carbapenemase production was tested by an immunochromatography assay. Antibiotic susceptibility testing (AST) was performed by broth microdilution. WGS was performed using short- and long-read sequencing. Transfer of carbapenemase-encoding plasmids was assessed by conjugation experiments.

RESULTS

Cf-Emp was isolated on selective medium for carbapenem-resistant Enterobacterales from the surveillance rectal swab taken at hospital admission from a patient of Moroccan origin. Cf-Emp produced three different carbapenemases, including KPC-2, OXA-181 and VIM-1, and was resistant to all β-lactams including carbapenems, novel BLICs (ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam) and cefiderocol. MIC of aztreonam/avibactam was 0.25 mg/L. The strain belonged to ST22, one of the C. freundii lineages of global diffusion, known to be associated with carbapenemase production. Each carbapenemase gene was located aboard a different plasmid (named pCf-KPC, pCf-OXA and pCf-VIM, respectively), which also carried other clinically relevant resistance genes, such as armA (pCf-KPC), blaSHV-12 (pCf-VIM) and qnrS1 (pCf-OXA). Transferability to Escherichia coli J53 by conjugation was observed for all plasmids.

CONCLUSIONS

The finding of enterobacterial strains carrying multiple carbapenemase genes on transferable plasmids is alarming, because similar strains could provide an important reservoir for disseminating these clinically relevant resistance determinants.

Seven Years of Culture Collection of Neisseria gonorrhoeae: Antimicrobial Resistance and Molecular Epidemiology

The emergence of Neisseria gonorrhoeae isolates displaying resistance to antimicrobials, in particular to ceftriaxone monotherapy or ceftriaxone plus azithromycin, represents a global public health concern. This study aimed to analyze the trend of antimicrobial resistance in a 7-year isolate collection retrospective analysis in Italy. Molecular typing on a subsample of gonococci was also included. A total of 1,810 culture-positive gonorrhea cases, collected from 2013 to 2019, were investigated by antimicrobial susceptibility, using gradient diffusion method, and by the N. gonorrhoeae multiantigen sequence typing (NG-MAST). The majority of infections occurred among men with urogenital infections and 57.9% of male patients were men who have sex with men. Overall, the cefixime resistance remained stable during the time. An increase of azithromycin resistance was observed until 2018 (26.5%) with a slight decrease in the last year. In 2019, gonococci showing azithromycin minimum inhibitory concentration above the EUCAST epidemiological cutoff value (ECOFF) accounted for 9.9%. Ciprofloxacin resistance and penicillinase-producing N. gonorrhoeae (PPNG) percentages increased reaching 79.1% and 18.7% in 2019, respectively. The most common sequence types identified were 5,441, 1,407, 6,360, and 5,624. The predominant genogroup (G) was the 1,407; moreover, a new genogroup G13070 was also detected. A variation in the antimicrobial resistance rates and high genetic variability were observed in this study. The main phenotypic and genotypic characteristics of N. gonorrhoeae isolates were described to monitor the spread of drug-resistant gonorrhea.

Virulence Determinants in Staphylococcus aureus Clones Causing Osteomyelitis in Italy

Staphylococcus aureus is the most common pathogen causing osteomyelitis (OM). The aim of this study was to explore the clonal complex (CC) distribution and the pattern of virulence determinants of S. aureus isolates from OM in Italy. Whole-genome sequencing was performed on 83 S. aureus isolates from OM cases in six hospitals. Antibiotic susceptibility tests showed that 30.1% of the isolates were methicillin-resistant S. aureus (MRSA). The most frequent CCs detected were CC22, CC5, CC8, CC30, and CC15, which represent the most common lineages circulating in Italian hospitals. MRSA were limited in the number of lineages (CC22, CC5, CC8, and CC1). Phylogenetic analysis followed the sequence type-CC groupings and revealed a non-uniform distribution of the isolates from the different hospitals. No significant difference in the mean number of virulence genes carried by MRSA or MSSA isolates was observed. Some virulence genes, namely cna, fib, fnbA, coa, lukD, lukE, sak, and tst, were correlated with the CC. However, different categories of virulence factors, such as adhesins, exoenzymes, and toxins, were frequently detected and unevenly distributed among all lineages. Indeed, each lineage carried a variable combination of virulence genes, likely reflecting functional redundancy, and arguing for the importance of those traits for the pathogenicity in OM. In conclusion, no specific genetic trait in the most frequent lineages could explain their high prevalence among OM isolates. Our findings highlight that CCs detected in OM isolates follow the epidemiology of S. aureus infections in the country. It is conceivable that any of the most common S. aureus CC can cause a variety of infections, including OM.

Rapid diagnostic tests in the management of pneumonia

INTRODUCTION

Pneumonia is one of the main causes of mortality associated with infectious diseases worldwide. Several challenges have been identified in the management of patients with pneumonia, ranging from accurate and cost-effective microbiological investigations, prompt and adequate therapeutic management, and optimal treatment duration.

AREAS COVERED

In this review, an updated summary on the current management of pneumonia patients is provided and the epidemiological issues of infectious respiratory diseases, which in the current pandemic situation are of particular concern, are addressed. The clinical and microbiological approaches to pneumonia diagnosis are reviewed, including discussion about the new molecular assays pointing out both their strengths and limitations. Finally, the current recommendations about antibiotic treatment are examined and discussed depending on the epidemiological contexts, including those with high prevalence of multidrug-resistant bacteria.

EXPERT OPINION

We claim that rapid diagnostic tests, if well-positioned in the diagnostic workflow and reserved for the subset of patients who could most benefit from these technologies, may represent an interesting and feasible tool to optimize timing of targeted treatments especially in terms of early de-escalation or discontinuation of antibiotic therapy.

Update on activity of dalbavancin and comparators against clinical isolates of Gram-positive pathogens from Europe and Russia (2017-2018), and on clonal distribution of MRSA

BACKGROUND

Gram-positive pathogens remain a major cause of healthcare- and community-associated infections. In particular, the dissemination of methicillin-resistant staphylococci, as methicillin-resistant S. aureus (MRSA) and vancomycin-resistant enterococci (VRE), have significantly reduced the therapeutic options, making the management of these infections even more challenging. Dalbavancin is a second-generation lipoglycopeptide approved for the treatment of moderate to severe acute bacterial skin and skin structure infections (ABSSSIs) caused by Gram-positive organisms, showing a bactericidal effect and a low propensity towards the selection of resistance over time.

AIM

This study aimed to evaluate the antimicrobial activity of dalbavancin and other comparators against recent clinical isolates of Gram-positive pathogens obtained from different sources and from several European countries, including countries of southern and eastern Europe and Russia, where resistance rates are typically high. This study also aimed to describe the clonal relationship of MRSA strains circulating in southern and eastern Europe and Russia.

RESULTS

A total of 1478 isolates were collected. Study results demonstrated the excellent and stable activity of dalbavancin against Gram-positive microorganisms, including MRSA. Interestingly, dalbavancin has retained unaltered MIC₅₀ and MIC₉₀ values over the years and seemed to have a low propensity in selecting resistance mechanisms.

CONCLUSIONS

Our data supported the potential efficacy of dalbavancin against Gram-positive bacteria and uncommon Gram-positive pathogens in patients with ABSSSIs. Of note, few CoNS isolates were resistant to dalbavancin and susceptible to vancomycin, pointing out the importance of testing the susceptibility to dalbavancin before its administration for CoNS infections.

Evaluation of Revogene® Carba C assay for the rapid detection of carbapenemase genes in gram-negative pathogens

The rapid detection of carbapenemase-producing microorganisms is crucial for clinical and infection control purposes. Here we evaluated Revogene®Carba C assay on 154 carbapenemase-producing and -nonproducing Gram-negatives. Up to 8 samples per 70 minutes were processed by Revogene®Carba C assay which showed excellent performances with 100% sensitivity, 99.5% specificity,100% NPV, and 97.8% positive predictive value.

Inappropriate use of carbapenems in an internal medicine ward: Impact of a carbapenem-focused antimicrobial stewardship program

PURPOSE

Carbapenem consumption is a major driver for selection and spread of carbapenem-resistant Enterobacterales (CRE). We assessed the impact of a carbapenem-focused multimodal antimicrobial stewardship program (ASP) in the internal medicine unit of a medium-size acute-care hospital.

METHODS

We compared the percentage of inappropriate carbapenem prescriptions and the proportion of carbapenem treated patients registered in a 12-month pre-intervention and in a 24-month post-intervention period by using an interrupted time series analysis. The consumption of carbapenems, expressed in defined daily doses (DDD), was also assessed. As a secondary objective, the incidence of infections by carbapenem-resistant Klebsiella pneumoniae (CRKP) and the percentage of CRKP invasive isolates in the same time periods were compared.

RESULTS

After the ASP intervention, the mean monthly percentage of inappropriate carbapenem prescriptions dropped from 59% to 25%, and the mean monthly proportion of carbapenem treated patients decreased from 3% to 1%. The interrupted time series analysis confirmed a significant decrease in the percentage of inappropriate carbapenem prescriptions (-41.6%, p = 0.0262) and in the proportion of carbapenem treated patients (-2.1%, p < 0.0001). Carbapenem consumption decreased from 5.2 to 1.6 DDD x 100 patient-days. The incidence of CRKP infections remained unchanged (29.1 × 100,000 patient-days vs 28.9 × 100,000 patient-days, p = 0.9864) and the percentage of CRKP invasive isolates decreased, though not significantly, from 36.4% to 13.3% (p = 0.3478).

CONCLUSIONS

The implementation of a carbapenem-focused ASP was effective at limiting the inappropriate use of carbapenems and was associated with a significant decrease in carbapenem consumption. Such effects were sustained during a 24-month post-intervention period.

Variable performance of different commercial systems for testing carbapenem susceptibility of KPC carbapenemase-producing Escherichia coli

OBJECTIVES

The aim was to evaluate different methods for testing carbapenem susceptibility of Escherichia coli producing KPC-type carbapenemase.

METHODS

Susceptibility to imipenem, meropenem and ertapenem was assayed using the reference broth microdilution method and several commercial methods (Vitek2, MicroScan, Etest, MIC Test Strip) starting from the same bacterial suspension. Susceptibility to imipenem and meropenem was also tested by Sensititre and disc diffusion (Bio-Rad). Results were interpreted according to EUCAST clinical breakpoints. Essential agreement (EA), category agreement (CA) and error rates were calculated as described by the International Organization for Standardization (ISO) guidelines and also considering the new EUCAST definitions. Genotypic diversity of isolates was evaluated with a RAPD profiling protocol.

RESULTS

Of 54 KPC-positive E. coli isolates, 5.6%, 7.4% and 0% were susceptible standard dosing regimen (S), 55.6%, 72.2% and 0% susceptible increased exposure (I), and 38.9%, 20.4% and 100.0% resistant (R) to imipenem, meropenem and ertapenem, respectively, using the reference broth microdilution method. CA lower than 90% were observed with all systems for imipenem and meropenem using both the ISO and the modified EUCAST criteria. With ertapenem, CA >90% was observed with all methods except Vitek2. RAPD profiling revealed a remarkable genotypic diversity of the isolates, supporting that results were not biased by an oligoclonal nature of the collection.

CONCLUSIONS

Commercial methods can be unreliable for testing susceptibility to carbapenems of KPC-producing E. coli. Susceptibility should be confirmed by reference broth microdilution.

Genomic analysis of Neisseria meningitidis carriage isolates during an outbreak of serogroup C clonal complex 11, Tuscany, Italy

Background

In 2015–2016, a cross-sectional carriage survey was performed in Tuscany Region, Italy, during an outbreak of invasive meningococcal disease due to Neisseria meningitidis serogroup C clonal complex 11 (MenC:cc11). This study aims to evaluate the genomic profile of meningococcal carriage isolates collected during the survey.

Methods

Whole-genome sequencing (WGS) was performed using Illumina MiSeq on 85 cultivated meningococcal carriage isolates received at the Dept. of Infectious Disease, National Institute of Health (Istituto Superiore di Sanità, ISS), as National Reference Laboratory (NRL) for Invasive Meningococcal Disease (IMD). De novo assembled genomes were scanned by the BIGSdb platform to assign: the genotypic profiles, the cgMLST, the vaccine antigen variants and allele types of antimicrobial resistance associated genes, together with denitrification pathway loci.

Results

Capsule null and non-groupable meningococci accounted for 52.9% and 10.6%, respectively. Among the remaining carriage isolates, serogroup B was the predominant (71.0%). Serogroup C meningococci were culture negative and unavailable for WGS. Overall, 64 genotypic profiles were identified and, based on cgMLST, isolates clustered according to clonal complexes. Eight isolates (9.4%) harbored at least one gene encoding a 4CMenB vaccine antigen. Mutated penA alleles were found in more than 82%. Finally, complete aniA and norB coding sequences were detected among 71.8% of carriage isolates.

Conclusions

Meningococcal carriage isolates collected during the MenC:cc11 outbreak were characterized by an extensive genetic diversity. The lack of outbreak-related isolates among carriage might be attributable to the high transmissibility with low duration of colonization of MenC:cc11 meningococci.

Carriage rates and risk factors during an outbreak of invasive meningococcal disease due to Neisseria meningitidis serogroup C ST-11 (cc11) in Tuscany, Italy: a cross-sectional study

Background

During 2015–2016 an outbreak of invasive meningococcal disease due to N. meningitidis serogroup C ST-11 (cc11) occurred in Tuscany, Italy. The outbreak affected mainly the age group 20–30 years, men who have sex with men, and the area located between the cities of Firenze, Prato and Empoli, with discos and gay-venues associated-clusters. A cross-sectional-survey was conducted to assess the prevalence and risk factors for meningococcal-carriage, in order to address public health interventions.

Methods

A convenience sample of people aged 11–45 years provided oropharyngeal swab specimens and completed questionnaires on risk factors for meningococcal carriage during a 3 months study-period, conducted either in the outbreak-area and in a control-area not affected by the outbreak (cities of Grosseto and Siena). Isolates were tested by culture plus polymerase chain reaction. Serogroup C meningococcal isolates were further characterized using multilocus sequence typing. Univariate and multivariate analyses were performed to estimate adjusted odds ratios (AORs) for meningococcal carriage.

Results

A total of 2285 oropharyngeal samples were collected. Overall, meningococcal carriage prevalence was 4.8% (n = 110), with nonencapsulated meningococci most prevalent (2.3%; n = 52). Among encapsulated meningococci, serogroup B was the most prevalent (1.8%; n = 41), followed by serogroup Y (0.5%; n = 11) and serogroup C (0.2%; n = 4); one carrier of serogroup E and one of serogroup Z, were also found (0.04%). Three individuals from the city of Empoli were found to carry the outbreak strain, C:ST-11 (cc11); this city also had the highest serogroup C carriage prevalence (0.5%). At the multivariate analyses, risk factors for meningococcal carriage were: illicit-drugs consumption (AOR 6.30; p < 0.01), active smoking (AOR 2.78; p = 0.01), disco/clubs/parties attendance (AOR 2.06; p = 0.04), being aged 20–30 years (AOR 3.08; p < 0.01), and have had same-sex intercourses (AOR 6.69; p < 0.01).

Conclusions

A low prevalence of meningococcal serogroup C carriage in an area affected by an outbreak due to the hypervirulent N. meningitidis serogroup C ST-11 (cc11) strain was found. The city of Empoli had the highest attack-rate during the outbreak and also the highest meningococcal serogroup C carriage-prevalence due to the outbreak-strain. Multivariate analyses underlined a convergence of risk factors, which partially confirmed those observed among meningococcal outbreak-cases, and that should be considered in targeted immunization campaigns.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3598-3) contains supplementary material, which is available to authorized users.

Characterization of KPC-encoding plasmids from two endemic settings, Greece and Italy

OBJECTIVES

Global dissemination of KPC-type carbapenemases is mainly associated with the spread of high-risk clones of Klebsiella pneumoniae and of KPC-encoding plasmids. In this study, we explored the population structure of KPC-encoding plasmids from the recent epidemics of KPC-producing K. pneumoniae (KPC-Kp) in Greece and Italy, the two major European endemic settings.

METHODS

Thirty-four non-replicate clinical strains of KPC-Kp representative of the early phases (2008-11) of the Greek (n = 22) and Italian (n = 12) epidemics were studied. Isolates were typed by MLST, and blaKPC-carrying plasmids were characterized by S1 profiling, PCR-based replicon typing and RFLP. Transfer experiments by conjugation or transformation were carried out with Escherichia coli recipients. Eleven plasmids, representative of all different restriction profiles, were completely sequenced.

RESULTS

The representative Greek strains belonged to 14 sequence types (STs), with a predominance of ST258. The representative Italian strains belonged to three STs, with a predominance of clonal complex 258 (ST258, ST512). The 34 strains carried plasmids of variable size (78-166 kb), either with blaKPC-2 or blaKPC-3 gene embedded in a Tn4401a transposon. Plasmids from Greek strains were mostly of a single RFLP type (A) and resembled the archetypal pKpQIL KPC-encoding plasmid, while plasmids from Italian strains belonged to a more heterogeneous population, showing five RFLP profiles (A, C-F). Types A and C resembled pKpQIL or deletion derivatives thereof, while types D-F included plasmids with hybrid structures between pKpQIL, pKPN3 and pKPN101-IT.

CONCLUSIONS

pKpQIL-like plasmids played a major role in the dissemination of blaKPC in Greece and Italy, but evolved with different dynamics in these endemic settings.

Antimicrobial susceptibility and emerging resistance determinants (blaCTX-M, rmtB, fosA3) in clinical isolates from urinary tract infections in the Bolivian Chaco

BACKGROUND

Bolivia is among the lowest-resourced South American countries, with very few data available on antibiotic resistance in bacterial pathogens. The phenotypic and molecular characterization of bacterial isolates responsible for urinary tract infections (UTIs) in the Bolivian Chaco are reported here.

METHODS

All clinical isolates from UTIs collected in the Hospital Basico Villa Montes between June 2010 and January 2014 were analyzed (N=213). Characterization included susceptibility testing, extended-spectrum beta-lactamase (ESBL) detection, identification of relevant resistance determinants (e.g., CTX-M-type ESBLs, 16S rRNA methyltransferases, glutathione S-transferases), and genotyping of CTX-M producers.

RESULTS

Very high resistance rates were observed. Overall, the lowest susceptibility was observed for trimethoprim-sulphamethoxazole, tetracycline, nalidixic acid, amoxicillin-clavulanic acid, ciprofloxacin, and gentamicin. Of E. coli and K. pneumoniae, 11.6% were ESBL producers. Resistance to nitrofurantoin, amikacin, and fosfomycin remained low, and susceptibility to carbapenems was fully preserved. CTX-M-15 was the dominant CTX-M variant. Four E. coli ST131 (two being H30-Rx) were identified. Of note, isolates harbouring rmtB and fosA3 were detected.

CONCLUSIONS

Bolivia is not an exception to the very high resistance burden affecting many South American countries. Optimization of alternative approaches to monitor local antibiotic resistance trends in resource-limited settings is strongly encouraged to support the implementation of effective empiric treatment guidelines.

Highly bactericidal Ag nanoparticle films obtained by cluster beam deposition

The recent emergence of bacterial pathogens resistant to most or all available antibiotics is among the major global public health problems. As indirect transmission through contaminated surfaces is a main route of dissemination for most of such pathogens, the implementation of effective antimicrobial surfaces has been advocated as a promising approach for their containment, especially in the hospital settings. However, traditional wet synthesis methods of nanoparticle-based antimicrobial materials leave a number of key points open for metal surfaces: such as adhesion to the surface and nanoparticle coalescence. Here we demonstrate an alternative route, i.e. supersonic cluster beam deposition, to obtain antimicrobial Ag nanoparticle films deposited directly on surfaces. The synthesized films are simple to produce with controlled density and thickness, are stable over time, and are shown to be highly bactericidal against major Gram positive and Gram negative bacterial pathogens, including extensively drug-resistant strains.

FROM THE CLINICAL EDITOR

The use of silver nanoparticle in health care is getting more widespread. The authors here describe the technique of cluster beam deposition for spraying silver on surfaces used in health care sectors. This may open a new avenue for future anti-bacterial coatings.

Quinolone resistance in absence of selective pressure: the experience of a very remote community in the Amazon forest

BACKGROUND

Quinolones are potent broad-spectrum bactericidal agents increasingly employed also in resource-limited countries. Resistance to quinolones is an increasing problem, known to be strongly associated with quinolone exposure. We report on the emergence of quinolone resistance in a very remote community in the Amazon forest, where quinolones have never been used and quinolone resistance was absent in 2002.

METHODS

The community exhibited a considerable level of geographical isolation, limited contact with the exterior and minimal antibiotic use (not including quinolones). In December 2009, fecal carriage of antibiotic resistant Escherichia coli was investigated in 120 of the 140 inhabitants, and in 48 animals reared in the community. All fluoroquinolone-resistant isolates were genotyped and characterized for the mechanisms of plasmid- and chromosomal-mediated quinolone resistance.

PRINCIPAL FINDINGS

Despite the characteristics of the community remained substantially unchanged during the period 2002-2009, carriage of quinolone-resistant E. coli was found to be common in 2009 both in humans (45% nalidixic acid, 14% ciprofloxacin) and animals (54% nalidixic acid, 23% ciprofloxacin). Ciprofloxacin-resistant isolates of human and animal origin showed multidrug resistance phenotypes, a high level of genetic heterogeneity, and a combination of GyrA (Ser83Leu and Asp87Asn) and ParC (Ser80Ile) substitutions commonly observed in fluoroquinolone-resistant clinical isolates of E. coli.

CONCLUSIONS

Remoteness and absence of antibiotic selective pressure did not protect the community from the remarkable emergence of quinolone resistance in E. coli. Introduction of the resistant strains from antibiotic-exposed settings is the most likely source, while persistence and dissemination in the absence of quinolone exposure is likely mostly related with poor sanitation. Interventions aimed at reducing the spreading of resistant isolates (by improving sanitation and water/food safety) are urgently needed to preserve the efficacy of quinolones in resource-limited countries, as control strategies based only on antibiotic restriction policies are unlikely to succeed in those settings.

Plasmid-mediated fluoroquinolone resistance determinants in Escherichia coli from community uncomplicated urinary tract infection in an area of high prevalence of quinolone resistance

In Italy fluoroquinolones (FQs) are extensively prescribed in empirical therapy of uncomplicated urinary tract infection (UTI) despite recommendations in national guidelines and widespread antibiotic resistance in community. To survey the dissemination of plasmid-mediated quinolone resistance in a peak area of FQs consumption, E. coli strains from 154 community and 41 local hospital patients were collected; low level ciprofloxacin resistance qnrA, qnrB, qnrS, and aac(6)'-Ib-cr genes were screened by PCR and patterns of transferable resistances were determined. Clinical ciprofloxacin resistance in hospital doubled community value, while overall rates of FQ resistance genes were similar (31.6% and 27.8%). Prevalence of aac(6')-Ib-cr gene was 11% in outpatients (21%, inpatients) and risk of harbouring this variant was significantly associated with gentamicin resistance; linkage to ceftazidime resistance was significant (P=0.001) and six out of eight strains produced CTX-M-15 and TEM-1 beta lactamases. In transconjugants, the unique pattern ampicillin/kanamycin-gentamicin/ ESBL + was associated with aac(6')-Ib-cr gene presence and with an increase of ciprofloxacin MIC value. Data highlight the need to monitor the resistance risk factors in the local community to provide clinicians with well-grounded guidelines for UTI therapy.

Carriage of antibiotic-resistant Escherichia coli among healthy children and home-raised chickens: a household study in a resource-limited setting

We have previously observed high rates of acquired antibiotic resistance in commensal Escherichia coli from healthy children living in urban areas of Bolivia and Peru, including resistance to tetracycline and quinolones, which are not routinely used in childhood. In this work we investigated acquired resistance in commensal E. coli from healthy children and home-raised chickens in 12 households from one of the previously surveyed urban area in Bolivia, to ascertain the possibility of human-animal exchange of resistant strains in similar settings. The resistance rates to ampicillin, tetracycline, chloramphenicol, streptomycin, and trimethoprim-sulphametoxazole were overall high (≥50%) and comparable between children and chickens, whereas those to quinolones were significantly higher in chickens (81% vs. 29% for nalidixic acid; 43% vs. 10% for ciprofloxacin). Molecular characterization of tetracycline- and quinolone-resistant isolates (n = 66) from children and chickens of three selected households revealed a remarkable clonal diversity and, in some cases, the presence of the same resistant strains among children or among chickens living in the same household, but not between children and chickens. Several resistance plasmids were characterized, but inter-clonal plasmid dissemination was not detected. Overall, the results from the present study suggested that cross-transmission between children and home-raised chickens could not represent a major spreading mechanism for resistant E. coli in households of resource-limited settings with high human-animal promiscuity.