External quality control survey on identification of microorganisms using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry（ MALDI-TOF MS） is a bacterial typing tool that was approved as a medical device in 2011. However, external accuracy control examination of bacterial typing using mass spectrometry is still only performed on a small scale. In this study, E. faecium and S. maltophilia were selected and tested according to established procedures using Score Values at 228 institutions. The Score Values for MALDI Biotyper were 2.43±0.08 for E. faecium and 2.38±0.08 for S. maltophilia; and those for VITEK MS/PRIME were 99.9±0.0 for E. faecium and S. maltophilia. These results suggest that it is useful to evaluate external accuracy control with Score Values using the procedures we have developed.

Characteristics of pediatric patients claimed with acute upper respiratory infection during otorhinolaryngology consultations: A descriptive study of a large Japanese medical claims database.

This study aimed to clarify other diseases claimed simultaneously with acute upper respiratory infection (URI), antibiotic prescriptions, and examinations associated with infectious diseases in pediatric patients with acute URI insurance claims at otorhinolaryngology outpatient visits. Pediatric patients who visited an otolaryngology department between 2019 and 2021 and were definitively diagnosed with URI were selected using a large Japanese medical claims database. Patient backgrounds, antibiotic use, and examinations were descriptively evaluated. In total, 8010 patients were included in the analysis. The median number (interquartile range) of diseases claimed in the same month as acute URI was 4 (3-6). Only 519 (6.5 %) patients were claimed as acute URI alone. Regardless of the prescription of antibiotics, the most commonly redundantly claimed disease in these patients was allergic rhinitis, followed by acute bronchitis, acute sinusitis, and earwax impaction. The frequently prescribed antibiotics were third-generation cephalosporins, macrolides, and penicillins with extended-spectrum, including amoxicillin which was recommended by the Japanese manual; the proportion of patients with examinations was low (2.9-21.7 %). Among patients with acute URI, diagnoses requiring antibiotics were also claimed; therefore, when evaluating acute URI using the Japanese medical claims database, care must be taken in patient selection. Moreover, the implementation rate of examinations necessary for diagnosis was low, so there is an urgent need to develop an environment where examinations can be conducted in outpatient settings.

Verification of quality assurance for blood culture surveillance using 6 years of data from the Japan Infection Prevention and Control Conference for National and Public University Hospitals.

The importance of blood culture has been widely recognized, and there is a need for monitoring to evaluate the accuracy of blood culture that reflects domestic healthcare systems. In this study, we assessed 6-year trends in blood culture quality assurance data. The Japan Infection Prevention and Control Conference for National and Public University Hospitals conducted yearly blood culture surveillance at 52 national public university hospitals from 2015 to 2020. Statistical analysis showed that comparison with the previous year showed significant differences in the number of blood cultures per 1000 patient-days in all years. The number of blood cultures per 1000 admissions was not significantly different in 2017 and 2018, but significant differences were shown in all other years. The multiple blood culture set rate was significantly different between non-pediatric inpatients and outpatients but not between pediatric inpatients and outpatients. The contamination rate did not differ significantly. For all parameters, significant differences were found when comparing 2015 and 2020. Our survey showed that although the sample number improved over time, even the most recent values for 2020 were lower than Cumitech's targets. It is difficult to assess whether these sample numbers are appropriate because target values have not been set for the various types of hospitals in Japan. Surveillance is a useful tool for monitoring quality assurance for blood culture. All parameters improved over the 6-year period, but it is necessary to establish a benchmark for evaluating optimization. We will continue to monitor quality assurance and work on setting benchmarks.

Williamsia muralis bacteraemia in a patient with Fanconi anaemia after haematopoietic cell transplantation.

Introduction: Williamsia muralis is an environmental bacterium first detected in 1999. Infections with W. muralis isolated have been reported in two elderly patients, and were associated with the surgical intervention of artificial objects. We present a case of bacteraemia caused by W. muralis following haematopoietic cell transplantation (HCT). Case presentation: A 10-year-old Japanese boy presented with fever and the swelling of the left cheek 8 days after HCT for the treatment of Fanconi anaemia. Gram-positive, rod-shaped bacteria were isolated from the blood cultures after 5 days incubation. 16S rRNA sequencing, but not mass spectrometry, identified a strain of W. muralis (1 414 bp, %ID 100 %). The phlegmon did not respond to antimicrobial therapy, but remitted with defervescence after a successful engraftment with teicoplanin and meropenem therapy on day 16 after HCT. The patient experienced recurrence of the bacteraemia, leading to central venous catheter (CVC) line removal. The same strain of W. muralis was isolated from the cultured tip of the CVC. To our knowledge, this is the first reported case of W. muralis bacteraemia and was complicated by CVC infection after HCT. Conclusion: W. muralis bacteraemia developed in an immunocompromised child. Introduction of artificial objects into the body raises a risk of rare infection with slowly growing environmental bacteria.

Examination of Conditions for External Quality Control in Identification of Microorganisms using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was approved for medical use in 2011 and is currently used as a rapid, accurate and lowcost technique for bacterial identification. External quality control for medical analysis is monitored using tests of the Japanese Association of Medical Technologists and Prefectural Association of Clinical Laboratory Technologists and through user surveys of reagent and equipment manufacturers. However, external quality control of bacterial typing using MS is not performed. Therefore, we examined procedures for evaluating quality control of bacterial typing using an identification reliability index at 38 facilities.

Genetic and epidemiological analysis of ESBL-producing Klebsiella pneumoniae in three Japanese university hospitals.

INTRODUCTION: We aimed to clarify the genetic background and molecular epidemiology of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae (K. pneumoniae) at three geographically separated university hospitals in Japan. METHODS: From January 2014 to December 2016, 118 ESBL-producing K. pneumoniae (EPKP) strains that were detected and stored at three university hospitals were collected. Molecular epidemiological analysis was performed using enterobacterial repetitive intergenic consensus (ERIC)-polymerase chain reaction (PCR) and multi-locus sequence typing (MLST). The ESBL type was determined using the PCR-sequence method. The presence of plasmid-mediated fluoroquinolone resistance (PMQR) genes was analyzed by PCR. We compared the relationships between PMQR gene possession/quinolone resistance-determining region (QRDR) mutation and levofloxacin (LVFX)/ciprofloxacin (CPFX) susceptibility. RESULTS: The detection rate of EPKP was 4.8% (144/2987 patients). MLST analysis revealed 62 distinct sequence types (STs). The distribution of STs was diverse, and only some EPKP strains had the same STs. ERIC-PCR showed discriminatory power similar to that of MLST. The major ESBL genotypes were CTX-M-15-, CTX-M-14-, and SHV-types, which were detected in 47, 30, and 27 strains, respectively. Ninety-one out of 118 strains had PMQR genes and 14 out of 65 strains which were not susceptible to CPFX had QRDR mutations, and the accumulation of PMQR genes and QRDR mutations tended to lead to higher minimum inhibitory concentrations (MICs) of LVFX. CONCLUSIONS: At three geographically separated university hospitals in Japan, the epidemiology of EPKP was quite diverse, and no epidemic strains were found, whereas CTX-M-14 and CTX-M-15 were predominant.

Stepwise Evolution of a Klebsiella pneumoniae Clone within a Host Leading to Increased Multidrug Resistance.

Five blaCTX-M-14-positive Klebsiella pneumoniae isolates (KpWEA1, KpWEA2, KpWEA3, KpWEA4-1, and KpWEA4-2) were consecutively obtained from a patient with relapsed acute myeloid leukemia who was continuously administered antimicrobials. Compared with KpWEA1 and KpWEA2, KpWEA3 showed decreased susceptibility to antimicrobials, and KpWEA4-1 and KpWEA4-2 (isolated from a single specimen) showed further-elevated multidrug-resistance (MDR) phenotypes. This study aims to clarify the clonality of the five isolates and their evolutionary processes leading to MDR by comparison of these complete genomes. The genome comparison revealed KpWEA1 was the antecedent of the other four isolates, and KpWEA4-1 and KpWEA4-2 independently emerged from KpWEA3. Increasing levels of MDR were acquired by gradual accumulation of genetic alterations related to outer membrane protein expression: the loss of OmpK35 and upregulation of AcrAB-TolC occurred in KpWEA3 due to ramA overexpression caused by a mutation in ramR; then OmpK36 was lost in KpWEA4-1 and KpWEA4-2 by different mechanisms. KpWEA4-2 further acquired colistin resistance by the deletion of mgrB. In addition, we found that exuR and kdgR, which encode repressors of hexuronate metabolism-related genes, were disrupted in different ways in KpWEA4-1 and KpWEA4-2. The two isolates also possessed different amino acid substitutions in AtpG, which occurred at very close positions. These genetic alterations related to metabolisms may compensate for the deleterious effects of major porin loss. Thus, our present study reveals the evolutionary process of a K. pneumoniae clone leading to MDR and also suggests specific survival strategies in the bacteria that acquired MDR by the genome evolution. IMPORTANCE Within-host evolution is a survival strategy that can occur in many pathogens and is often associated with the emergence of novel antimicrobial-resistant (AMR) bacteria. To analyze this process, suitable sets of clinical isolates are required. Here, we analyzed five Klebsiella pneumoniae isolates which were consecutively isolated from a patient and showed a gradual increase in the AMR level. By genome sequencing and other analyses, we show that the first isolate was the antecedent of the later isolates and that they gained increased levels of antimicrobial resistance leading to multidrug resistance (MDR) by stepwise changes in the expression of outer membrane proteins. The isolates showing higher levels of MDR lost major porins but still colonized the patient's gut, suggesting that the deleterious effects of porin loss were compensated for by the mutations in hexuronate metabolism-related genes and atpG, which were commonly detected in the MDR isolates.

Examination of conditions for regular internal quality control in identification of microorganisms using MALDI-TOF MS.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was approved for medical use in 2011, and is currently used as a rapid, accurate and low-cost technique for bacterial identification. Microbiological testing and internal accuracy control in Japan are mainly implemented in accordance with the standards of the Clinical and Laboratory Standards Institute (CLSI). However, few facilities perform internal accuracy control of bacterial identification by MALDI-TOF MS. Therefore, we examined the procedures for internal accuracy control of bacterial identification using MALDI-TOF MS in daily work at clinical laboratories in the seven hospitals.

Within-host evolution of a Klebsiella pneumoniae clone: selected mutations associated with the alteration of outer membrane protein expression conferred multidrug resistance.

BACKGROUND: A patient repeatedly developed bacteraemia despite the continuous use of antibiotics. We obtained two Klebsiella pneumoniae isolates from the patient's blood on Days 72 and 105 after hospitalization. Each of the two isolates belonged to ST45, but while the first isolate was susceptible to most antibiotics, the second one was resistant to multiple drugs including carbapenems. OBJECTIVES: To identify the genetic differences between the two isolates and uncover alterations formed by the within-host bacterial evolution leading to the antimicrobial resistance. METHODS: Whole-genome comparison of the two isolates was carried out to identify their genetic differences. We then profiled their outer membrane proteins related to membrane permeability to drugs. To characterize a ramR gene mutation found in the MDR isolate, its WT and mutant genes were cloned and expressed in the MDR isolate. RESULTS: The two isolates showed only three genomic differences, located in mdoH, ramR and upstream of ompK36. In the MDR isolate, a single nucleotide substitution in the ompK36 upstream region attenuated OmpK36 expression. A single amino acid residue insertion in RamR in the MDR isolate impaired its function, leading to the down-regulation of OmpK35 and the subsequent up-regulation of the AcrAB-TolC transporter, which may contribute to the MDR. CONCLUSIONS: We identified very limited genomic changes in the second K. pneumoniae clone during within-host evolution, but two of the three identified mutations conferred the MDR phenotype on the clone by modulating drug permeability.

Clinical and pathogenic features of SCCmec type II and IV methicillin-resistant Staphylococcus aureus in Japan.

Staphylococcal chromosomal cassette mec (SCCmec) type IV methicillin-resistant Staphylococcus aureus (MRSA) has rapidly disseminated in healthcare settings, and its characteristics in the United States and Europe are well known. Because Japanese SCCmec type IV MRSA clones are different and less well documented, this retrospective, single center study was done to determine and compare the characteristics of SCCmec type II and IV MRSA in Japan. For the analysis, 55 SCCmec type II and 101 type IV MRSA samples were collected from lower respiratory tract specimens or from skin or soft tissue. The patients of the SCCmec type IV group were significantly younger than those of the type II group (P < 0.001). The rate of MRSA pneumonia was significantly lower for SCCmec type IV than for type II (7.8% vs 29.0%, P = 0.026). In contrast, the rate of skin and soft tissue infection was not significantly different (66.0% vs 61.9%, P = 0.788). The distribution of MRSA pathogenic genes (sea, seb, sem, seo) was significantly different between SCCmec types II and IV (P < 0.001), which indicates that their clonal complex may be completely different. Interestingly, all SCCmec type II MRSA that caused MRSA pneumonia had seb and egc and lacked tst that belonged to sequence type (ST) 764. This is the first study to reveal and compare the characteristics of Japanese SCCmec type II and type IV MRSA. The information from this study will be helpful for the management of Japanese MRSA infection.

A dramatic increase in the positive blood culture rates of Helicobacter cinaedi: the evidence of differential detection abilities between the Bactec and BacT/Alert systems.

In our hospital, positive blood culture rates of Helicobacter cinaedi dramatically increased after introducing the Bactec system. A simulated culture model of H. cinaedi bacteremia demonstrated no positive signals using the BacT/Alert system, despite efficient growth in bottles. Clinically suspected H. cinaedi bacteremia should be monitored more closely when using the BacT/Alert system, preferably with subcultivation after 7days of incubation.

Comparison of two types of matrix-assisted laser desorption/ionization time-of-flight mass spectrometer for the identification and typing of Clostridium difficile.

Microflex LT (Bruker Daltonics) and VITEK MS (bioMérieux) are bacterial identification systems that are based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). For VITEK MS, two identification softwares, VITEK MS IVD (IVD) and SARAMIS (SARAMIS), are available. Microflex LT is equipped with MALDI Biotyper RTC software (Biotyper). Although the identification accuracy of each instrument has been compared for various bacteria, no detailed examination has been conducted for the identification accuracy of Clostridium difficile. In this report, we compared the three identification softwares for identification reproducibility in three ATCC C. difficile strains and identification accuracy in 50 clinical C. difficile isolates. The results showed 100, 91.7 and 100 % identification reproducibility accuracy of ATCC strains when examined by IVD, SARAMIS and Biotyper software, respectively. For the identification of the clinical isolates, all three softwares exhibited satisfactory identification accuracy of C. difficile. Among the 50 clinical isolates, seven showed identical toxin genotype corresponding to the exact ribotype. However, MALDI-TOF MS failed to identify them as the identical type. Based on the above results, we concluded that both types of MALDI-TOF MS reproducibly identified C. difficile; however, they are currently not suitable for typing of C. difficile clones.

[Surveillance report of drug-resistant bacteria from 2007 to 2012 in Saga Prefecture, Japan (the second report)].

Drug-resistant bacteria are a problematic issue in Japan. Surveillance of drug-resistant bacteria is important because the frequency of isolation and kinds of such bacteria vary between hospitals and local areas. This study summarizes the results of detection of drug-resistant bacteria in Saga Prefecture from July 2007 to June 2012. Data presented in this study were collected through questionnaire survey that was conducted in 12 hospitals. Frequency of drug-resistant bacteria are as follows: 62.5% of Staphylococcus aureus was methicillin-resistant S. aureus (MRSA); 62.2% of Streptococcus pneumoniae was penicillin-intermediate S. pneumoniae (PISP) or penicillin-resistant S. pneumoniae (PRSP); 26.4% of Haemophilus influenzae was beta-lactamase negative ampicillin-resistant H. influenzae (BLNAR); 0.5% of Pseudomonas aeruginosa was metallo-beta-lactamase (MBL) P. aeruginosa; 0.5% of P. aeruginosa was multi-drug resistant P. aeruginosa (MDRP); 12.9% and 5.1% of Escherichia coli and Klebsiella pneumoniae, respectively, were extended-spectrum beta-lactamase (ESBL) producing organisms. While the isolation frequencies of MRSA and PISP/PRSP were unchanged, those of BLNAR, ESBL producing E. coli and ESBL producing K. pneumoniae raised from 15.4% to 34.2%, from 5.7% to 18.4% and from 2.6% to 8.2%, respectively, over the past 5 years. The frequencies of isolation of MDRP and two drug resistant P. aeruginosa declined. This study revealed that the overall trend in the long-term changes of isolation frequency of drug-resistant bacteria in Saga Prefecture is similar to the trend in the national data. It also showed that the frequency and kinds of drug-resistant bacteria are variable between hospitals and local areas. Further study, such as examination of the usage and MIC value of antimicrobial drugs, will enable us to gain more detailed information on the drug-resistant bacteria.

Successful treatment of invasive zygomycosis based on a prompt diagnosis using molecular methods in a patient with acute myelogenous leukemia.

Zygomycosis is a lethal and invasive mold infection that is often associated with hematological malignancies. The keys for successful treatment include making a rapid diagnosis and appropriately administering antifungal agents. We herein report the early diagnosis of a case of zygomycosis in a patient with acute myeloid leukemia using a deoxyribonucleic acid sequence analysis. We successfully performed allogeneic hematopoietic stem cell transplantation with the use of high-dose liposomal amphotericin B and granulocyte transfusion.

[Microbiological and clinical features of nine cases with nocardial infections].

Following recent advance in medical technology, the increase of immunocompromised patients results in an increase of opportunistic infections such as nocardiosis. However, little is known about relationships between clinical features of nocardial infections and each Nocardia species, especially newly identified ones. Therefore, we identified clinical isolates of Nocardia species by genetic methods and analyzed clinical features of nocardiosis. Nine clinical isolates were obtained in Kyushu University Hospital from 2005 to 2008. Six different Nocardia species were identified by 16Sr RNA: Nocardiafarcinia (n=2), Nocardia brasiliensis (n=2), Nocardia cyriacigeorgica (n=2), Nocardia transvalensis (n=1), Nocardia araoensis (n=1) and Nocardia testacea (n=1). The underlying diseases of 9 patients were pulmonary diseases(n=5), malignant diseases(n=3), collagen diseases(n=1) or primary immunodeficiency diseases (n=l). According to antimicrobial susceptibility testing, none of them was resistant to minocycline or linezolid. Among seven isolates from respiratory specimens, one was resistant to imipenem, sulfamethoxazole/trimethoprim and amikacin, two were to ciprofloxacin. Three species identified recently (N cyriacigeorgica, N. araoensis and N. testacea) were involved in this study and most of them were considered as infectious pathogens to human. These data suggested the identification of Nocardia to the species level and susceptibility testing were important for diagnosis as infectious diseases and treatments.

[Distributions and spreads of antimicrobial drug-resistant microorganisms in Saga prefecture].

We investigated the distribution of drug-resistant organisms to clarify transmission of the organisms. Drug-resistant organisms were surveyed in 12 facilities in 4 districts of Saga prefecture for 2 years, and were analyzed by beta-lactamase typing, antimicrobial susceptibility tests and pulsed-field gel electrophoresis (PFGE). The number of isolates was 111,505 for the 2 years. Questionnaires for drug-resistant organisms revealed that Methicillin-resistant Staphylococcus aureus (MRSA) was 64.1% of S. aureus, penicillin-intermediate Streptococcus pneumoniae (PISP) or penicillin-resistant S. pneumoniae (PRSP) 60.1% of S. pneumoniae, beta-lactamase-negative ampicillin-resistent Haemophilus inflluenzae (BLNAR) 19.4% of H. influenzae, Metallo-beta-Lactamase (MBL) 0.1% of gram-negative bacilli, multi-drug resistant Pseudomonas aeruginosa (MDRP) 0.6% of P. aeruginosa and extended-spectrum beta-lactamase (ESBL) producing organisms 8.0% and 3.1% of Escherichia coli and Klebsiella pneumoniae, respectively. PFGE analysis of ESBL E. coli revealed that 33 isolates collected from 7 facilities in 3 districts belonged to the same one group, indicating that this strain is transferred between different hospitals in different saga districts. Investigations of distribution of drug-resistant organisms in not only each hospitals but also in the first and the second medical areas are important for controls of healthcare-associated infections and antibiotic prescriptions.

[Comparison of the antimicrobial susceptibility testing with three automated systems for MRSA, VISA, ESBL-producing Escherichia coli and Klebsiella pneumoniae].

Some automated systems of the identification and susceptibility for microorganisms are used and prevail in hospital laboratories. One of the most serious problems is to perform accurate susceptibility testing for low-level resistant organisms, while antibiotic resistant microbes are increasing in medical fields. To evaluate automated machines for the susceptibility testing, several antibiotic resistant organisms were examined by plural technicians in some laboratories. Each strain of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycinintermediate S. aureus (VISA), extended-spectrum ß-lactamase (ESBL) producing Escherichia coli and Klebsiella pneumoniae was tested by three automated systems of WalkAway, VITEK2/VITEK2 compact and Phoenix for susceptibility. The results for antibiotics generated by the systems were compared to those generated by reference methods according to CLSI guidelines. The results of WalkAway, VITEK2/VITEK2 compact, and Phoenix demonstrated 92%, 91%, and 96% of reproducibilities, 92%, 94%, and 91% of MIC agreements, 0.5%, 0.8%, and 0.3% of very major error (VME) and 0.3%, 1.4%, and 2.3% of major error (ME), respectively. All automated systems had a high reproducibility even under the performance of plural technicians, although the differences of VMEs and MEs were observed among the systems. From these data, the automated systems for antimicrobial susceptibility testing were more useful for the detection of antibiotic resistant organisms by understanding the characteristics of each system.

Clonal spread in Eastern Asia of ciprofloxacin-resistant Escherichia coli serogroup O25 strains, and associated virulence factors.

A significant problem in the field of infectious diseases is the increase in fluoroquinolone (FQ)-resistant Escherichia coli. Although mutation of strains and clonal dissemination are supposed to be the cause of this increase, little is known about the prevalence of this organism. We investigated 219 FQ-resistant E. coli strains in Japan and nine Asian countries by serotyping and genotyping. Seventy-one strains (32.4%) were serogroup O25, which was prevalent in South Korea, China and Japan, especially in the southwest part of Japan. Aerobactin, a virulence factor in uropathogenic and avian pathogenic E. coli, was associated with the presence of FQ-resistant O25 strains of E. coli. Seven of the seventy-one FQ-resistant E. coli O25 had extended-spectrum beta-lactamase genes (six CTX-M-14 and one SHV-12), however, we were unable to find any E. coli O25-ST131 clone that produced CTX-M-15, which was previously reported to have emerged across continents. These data demonstrate that a clonal group of FQ-resistant and virulent E. coli recently became prevalent at least in East Asia and suggest that this might become a public health problem because the strains may acquire resistance to other antimicrobial agents.

Geographic distribution of fluoroquinolone-resistant Escherichia coli strains in Asia.

Fluoroquinolone (FQ) resistance is usually caused by point mutations within the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC and/or parE. However, little is known about the worldwide increase in FQ-resistant Escherichia coli or, more specifically, about the geographical distribution of QRDR mutations and the clonal spread of isolates. In this study, we analysed 68 FQ-resistant E. coli isolates from eight Asian countries using QRDR amino acid mutation patterns and examined their susceptibility to FQs. Of the isolates, 38% had mutations at S83 and D87 of GyrA and S80 of ParC (MM/-/M-/-) and 34% had mutations at S83 and D87 of GyrA, S80 of ParC and S458 of ParE (MM/-/M-/M). MIC(50) values (minimum inhibitory concentrations for 50% of the isolates) for isolates with at least mutation at S458 of ParE for ciprofloxacin and prulifloxacin were relatively higher than MIC(50) values of isolates without this mutation. Based on their geographic distribution and the QRDR mutation patterns, the isolates were divided into a common type in which the organisms were isolated from three or more countries, and a local type in which the isolates were from one or two countries. Mutation types at S83L and D87N in GyrA and S80I in ParC with no or another site in the QRDR were the most frequent among the FQ-resistant isolates, especially among the common type. Gene typing indicated that isolates in the common type were not similar between countries. These data suggest that the increase in FQ-resistant E. coli strains is mainly generated by mutations in the QRDR in each geographical area rather than through intercontinental spread.