Increase In Fluoroquinolone Resistance Research Articles

Genotypic characterization and antimicrobial susceptibility of human Campylobacter jejuni isolates in Southern Spain.

Campylobacter jejuni is the main cause of bacterial gastroenteritis and a public health problem worldwide. Little information is available on the genotypic characteristics of human C. jejuni in Spain. This study is based on an analysis of the resistome, virulome, and phylogenetic relationship, antibiogram prediction, and antimicrobial susceptibility of 114 human isolates of C. jejuni from a tertiary hospital in southern Spain from October 2020 to June 2023. The isolates were sequenced using Illumina technology, and a bioinformatic analysis was subsequently performed. The susceptibility of C. jejuni isolates to ciprofloxacin, tetracycline, and erythromycin was also tested. The resistance rates for each antibiotic were 90.3% for ciprofloxacin, 66.7% for tetracycline, and 0.88% for erythromycin. The fluoroquinolone resistance rate obtained is well above the European average (69.1%). CC-21 (n = 23), ST-572 (n = 13), and ST-6532 (n = 13) were the most prevalent clonal complexes (CCs) and sequence types (STs). In the virulome, the cadF, ciaB, and cdtABC genes were detected in all the isolates. A prevalence of 20.1% was obtained for the genes wlaN and cstIII, which are related to the pathogenesis of Guillain-Barré syndrome (GBS). The prevalence of the main antimicrobial resistance markers detected were CmeABC (92.1%), RE-cmeABC (7.9%), the T86I substitution in gyrA (88.9%), blaOXA-61 (72.6%), tet(O) (65.8%), and ant (6)-Ia (17.1%). High antibiogram prediction rates (>97%) were obtained, except for in the case of the erythromycin-resistant phenotype. This study contributes significantly to the knowledge of C. jejuni genomics for the prevention, treatment, and control of infections caused by this pathogen.IMPORTANCEDespite being the pathogen with the greatest number of gastroenteritis cases worldwide, Campylobacter jejuni remains a poorly studied microorganism. A sustained increase in fluoroquinolone resistance in human isolates is a problem when treating Campylobacter infections. The development of whole genome sequencing (WGS) techniques has allowed us to better understand the genotypic characteristics of this pathogen and relate them to antibiotic resistance phenotypes. These techniques complement the data obtained from the phenotypic analysis of C. jejuni isolates. The zoonotic transmission of C. jejuni through the consumption of contaminated poultry supports approaching the study of this pathogen through "One Health" approach. In addition, due to the limited information on the genomic characteristics of C. jejuni in Spain, this study provides important data and allows us to compare the results with those obtained in other countries.

Detection of Macrolide and/or Fluoroquinolone Resistance Genes in Mycoplasma genitalium Strains Isolated from Men in the Northwest Region of Croatia in 2018-2023.

Mycoplasma genitalium (M. genitalium) poses a significant public health challenge due to its association with non-gonococcal urethritis (particularly in men) and antimicrobial resistance. However, despite the prevalence of M. genitalium infections and the rise in resistance rates, routine testing and surveillance remain limited. This is the first study from Croatia that aimed to assess the prevalence and trends of resistance in M. genitalium strains isolated from male individuals by detecting macrolide and fluoroquinolone resistance genes. The study also aimed to explore the factors associated with resistance and changes in resistance patterns over time. Urine samples collected from male individuals in the Zagreb County and northwest region of Croatia between 2018 and 2023 were tested for M. genitalium with the use of molecular methods. Positive samples were subjected to DNA extraction and multiplex tandem polymerase chain reaction (MT-PCR) targeting genetic mutations associated with macrolide (23S rRNA gene) and fluoroquinolone (parC gene) resistance. Of the 8073 urine samples tested from 6480 male individuals (and following the exclusion of repeated specimens), we found that the prevalence of M. genitalium infection was 2.2%. Macrolide resistance was observed in 60.4% of strains, while fluoroquinolone resistance was found in 19.2%. Co-resistance to both antibiotics was present in 18.2% of cases. A statistically significant increase in fluoroquinolone resistance was noted over the study period (p = 0.010), but this was not evident for azithromycin resistance (p = 0.165). There were no statistically significant differences in resistance patterns between age groups, whereas re-testing of patients revealed dynamic changes in resistance profiles over time. The high burden of macrolide resistance and increasing fluoroquinolone resistance underscore the urgent need for comprehensive resistance testing and surveillance programs. The implementation of resistance-guided treatment strategies, along with enhanced access to molecular diagnostics, is pivotal for effectively managing M. genitalium infections.

Monitoring fluoroquinolone resistance among ESBL-positive and ESBL-negative Escherichia coli strains isolated from urinary tract infections: An alert for empirical treatment

Bacterial resistance to extended-spectrum beta-lactamases (ESBL) is present worldwide. Empirical antibiotic therapy is often needed, and the use of fluoroquinolones, such as ciprofloxacin and norfloxacin, is common. This study aimed to analyze the urine cultures from 2,680 outpatients in January 2019, 2020, 2021, and 2022, with bacterial counts above 100,000 CFU/mL in which Escherichia coli was the etiological agent. We monitored the resistance of ESBL-positive and ESBL-negative strains to ciprofloxacin and norfloxacin and evaluated resistance rates. Significantly higher fluoroquinolone resistance rates were observed among ESBL-positive strains in all years studied. Furthermore, a significant increase in the rate of fluoroquinolone resistance was observed between 2021 and 2022 in ESBL-positive and -negative strains, as well as from 2020 to 2021 among the ESBL-positive strains. The data obtained in the present study showed a tendency towards an increase in fluoroquinolone resistance among ESBL-positive and -negative E. coli strains isolated from urine cultures in Brazil. Since empirical antibiotic therapy with fluoroquinolones is commonly used to treat diverse types of infections, such as community-acquired urinary tract infections, this work highlights the need for continuous monitoring of fluoroquinolone resistance among E. coli strains circulating in the community, which can mitigate the frequency of therapeutic failures and development of widespread multidrug-resistant strains.

Comparative genomics of drug-resistant strains of Mycobacterium tuberculosis in Ecuador

BackgroundTuberculosis is a serious infectious disease affecting millions of people. In spite of efforts to reduce the disease, increasing antibiotic resistance has contributed to persist in the top 10 causes of death worldwide. In fact, the increased cases of multi (MDR) and extreme drug resistance (XDR) worldwide remains the main challenge for tuberculosis control. Whole genome sequencing is a powerful tool for predicting drug resistance-related variants, studying lineages, tracking transmission, and defining outbreaks. This study presents the identification and characterization of resistant clinical isolates of Mycobacterium tuberculosis including a phylogenetic and molecular resistance profile study by sequencing the complete genome of 24 strains from different provinces of Ecuador.ResultsGenomic sequencing was used to identify the variants causing resistance. A total of 15/21 isolates were identified as MDR, 4/21 as pre-XDR and 2/21 as XDR, with three isolates discarded due to low quality; the main sub-lineage was LAM (61.9%) and Haarlem (19%) but clades X, T and S were identified. Of the six pre-XDR and XDR strains, it is noteworthy that five come from females; four come from the LAM sub-lineage and two correspond to the X-class sub-lineage. A core genome of 3,750 genes, distributed in 295 subsystems, was determined. Among these, 64 proteins related to virulence and implicated in the pathogenicity of M. tuberculosis and 66 possible pharmacological targets stand out.Most variants result in nonsynonymous amino acid changes and the most frequent genotypes were identified as conferring resistance to rifampicin, isoniazid, ethambutol, para-aminosalicylic acid and streptomycin. However, an increase in the resistance to fluoroquinolones was detected.ConclusionThis work shows for the first time the variability of circulating resistant strains between men and women in Ecuador, highlighting the usefulness of genomic sequencing for the identification of emerging resistance. In this regard, we found an increase in fluoroquinolone resistance. Further sampling effort is needed to determine the total variability and associations with the metadata obtained to generate better health policies.

Mycoplasma genitalium: Prevalence of macrolide and fluoroquinolone resistance at the University Hospital of Tours, and check of the S-DiaMGRes® (Diagenode Diagnostics) assay

Mycoplasma genitalium is an emerging agent of sexually transmitted infections, associated with urethritis, cervicitis, and pelvic inflammatory disease. Over the past decade, a remarkable increase in macrolide-resistant M.genitalium, the first-line treatment, is observed all over the world. In some regions, an increase in fluoroquinolone-resistance, the second-line treatment, is also noticed. It therefore seems important to have a knowledge of the local epidemiology as well as the means of detecting these resistances in order to best adapt the treatment. Our study aimed to determine the prevalence of macrolide and fluoroquinolone-resistant Mycoplasma genitalium at the University Hospital of Tours in 2018, using a real-time PCR technique followed by Sanger sequencing. The prevalence of macrolide resistance in our population was 15.4%. No FQ resistance-conferring mutations were observed in our study. Furthermore, we evaluated the performance of the commercial kit S-DiaMGRes® (Diagenode Diagnostics, Belgium), allowing the detection of 23S rRNA mutations conferring resistance to macrolides.

Rates of fluoroquinolone resistance in domestically acquired Campylobacter jejuni are increasing in people living within a model study location in Canada.

Antimicrobial resistance was evaluated in Campylobacter jejuni isolated from 1291 diarrheic people over a 15-year period (2004-2018) in southwestern Alberta, a model location in Canada with a high rate of campylobacteriosis. The prevalence of resistance to chloramphenicol, clindamycin, erythromycin, and gentamicin was low during the examination period (≤4.8%). Resistance to tetracycline remained consistently high (41.6%-65.1%), and resistance was primarily conferred by plasmid-borne tetO (96.2%). Resistance rates to ciprofloxacin and nalidixic acid increased substantially over the examination period, with a maximal fluoroquinolone resistance (FQR) prevalence of 28.9% in 2016. The majority of C. jejuni isolates resistant to ciprofloxacin (93.9%) contained a C257T single nucleotide polymorphism within the gyrA chromosomal gene. Follow up with infected people indicated that the observed increase in FQR was primarily due to domestically acquired infections. Moreover, the majority of FQ-resistant C. jejuni subtypes (82.6%) were endemic in Canada, primarily linked to cattle and chicken reservoirs; 18.4% of FQ-resistant isolates were assigned to three subtypes, predominantly associated with cattle. Study findings indicate the need to prioritize FQR monitoring in C. jejuni infections in Canada and to elucidate the dynamics of the emergence and transmission of resistant C. jejuni strains within and from cattle and chicken reservoirs.

Antibiotic Prophylaxis for the Prevention of Infectious Complications following Prostate Biopsy: A Systematic Review and Meta-Analysis.

Infectious complications following prostate biopsy are increasing and fluoroquinolone prophylaxis has recently been banned by the European Commission. In this systematic review we summarize the evidence for different antibiotic prophylaxis regimens. We searched MEDLINE®, Embase® and Cochrane Database for randomized controlled trials (inception to October 2019) assessing antimicrobial interventions in prostate biopsy. Primary outcome was infectious complications. Exclusion criteria were simultaneous interfering interventions. GRADE (Grading of Recommendations, Assessment, Development and Evaluations) was used to assess the certainty of evidence. Protocol was registered with PROSPERO (CRD42015026354). Overall 59 randomized controlled trials (14,153 participants) and 7 different antimicrobial interventions were included. Antibiotic prophylaxis reduced infectious complications compared to no prophylaxis (RR 0.56, 95% CI 0.40-0.77, p=0.0005, I2=15%, participants 1,753, studies 11). A short-term prophylaxis (single shot to 3 days) was inferior to a long-term prophylaxis (1 to 7 days) with fluoroquinolone (RR 1.89, 95% CI 1.37-2.61, p=0.0001, I2=0%, participants 3,999, studies 17). Fosfomycin trometamol was an alternative to fluoroquinolone with reduced rates of infectious complications (RR 0.49, 95 CI 0.27-0.87, p=0.02, I2=54%, participants 1,239, studies 3). Empiric prophylaxis was inferior to targeted prophylaxis (RR 1.81, 95% CI 1.28-2.55, p=0.0008, I2=48%, participants 1,511, studies 6). Standard prophylaxis was inferior to augmented prophylaxis (using multiple rather than single agent) using a fixed model (RR 2.10, 95% CI 1.53-2.88, p <0.0001, I2=71%, participants 2,597, studies 9), but not using a random model (p=0.07). No difference was observed in infectious complications based on route or timing of antimicrobial prophylaxis. The certainty of evidence was rated as low/very low. In countries where fluoroquinolones are allowed as antibiotic prophylaxis, a minimum of a full 1-day administration as well as targeted therapy in case of fluoroquinolone resistance is recommended. In countries with a ban on fluoroquinolones, fosfomycin is a good alternative, as is augmented prophylaxis, although no established standard combination exists to date.

Changes in antimicrobial resistance and molecular attributes of Salmonellae causing enteric fever in Kolkata, India, 2014–2018

Globally, enteric fever caused by Salmonella Typhi (S. Typhi, ST) and S. Paratyphi A (SPA) remain one of the major diseases of public health importance. In this study, a total of 457 (380 ST, 77 SPA) blood isolates were collected from three tertiary care hospitals in Kolkata during 2014–18. Additionally, 66 (3.4%) ST and 5 (0.25%) SPA were recovered from blood culture of 1962 patients attending OPD of one pediatric hospital during 2016–18. The study isolates were tested for antimicrobial resistance (AMR) profiles; AMR genes; molecular sub-types by PFGE, MLVA and CRISPR. Among the total 446 ST and 82 SPA isolates, fluoroquinolone (FQ) resistance was very common in both serovars. Ciprofloxacin resistance of 24.9% and 9.8% & ofloxacin resistance of 20.9% and 87.8% were found in ST and SPA respectively. Majority (>70%) of the isolates showed decreased susceptibility to ciprofloxacin (DCS). A single point mutation in gyrA gene (S83F) was responsible for causing DCS in 37.5% (n = 42/112) ST and 63% (n = 46/73) SPA isolates. Multidrug resistance (MDR) was found only in 3.4% ST isolates and encoded the genes blaTEM-1, catA, sul, strA-strB, class 1 integron with dfrA7. All MDR ST (n = 15) possessed non-conjugative non-IncHI1 (180 kb) plasmid except one having conjugative IncHI1 (230 kb) plasmid and one without plasmid. The MDR genes were integrated near chromosomal cyaA gene site in ST with/without the presence of plasmid (nonIncH1). Almost 65.7% resistant ST belonged to H58 haplotype. PFGE showed clonally related isolates with 81% similarity in ST and 87% in SPA. Similarly, CRISPR typing showed less diversity among the isolates. However, the isolates (ST and SPA) were found to be more diverse by MLVA typing (D value 0.987 and 0.938). The study reports decrease in MDR and increase in FQ resistance among typhoidal Salmonella isolates over the years giving interesting information for enteric fever treatment.

Acquisition of fluoroquinolone resistance leads to increased biofilm formation and pathogenicity in Campylobacter jejuni

The World Health Organization has listed C. jejuni as one of 12 microorganisms on a global priority list for antibiotic resistance due to a rapid increase in strains resistant to fluoroquinolone antibiotics. This fluoroquinolone resistance is conferred through a single point mutation in the QRDR region within the gyrA gene known to be involved in DNA supercoiling. We have previously revealed that changes in DNA supercoilikng play a major role in the regulation of virulence in C. jejuni with relaxation of DNA supercoiling associated with increased attachment to and invasion of human epithelial cells. The aim of this study was to investigate whether fluoroquinolone resistant strains of C. jejuni displayed altered supercoiling associated phenotypes. A panel of fluoroquinolone resistant mutants were derived and shown to have a greater ability to form viable biofilms under aerobic conditions, invade epithelial cells and promote virulence in the Galleria mellonella model of infection. We thus report for the first time that fluoroquinolone resistance in C. jejuni is associated with an increase in virulence and the ability to form viable biofilms in oxygen rich environments. These altered phenotypes likely play a critical role in the continued increase in fluoroquinolone resistance observed for this important pathogen.

Occurrence of Campylobacter jejuni and Campylobacter coli in Cattle and Sheep in Northern Spain and Changes in Antimicrobial Resistance in Two Studies 10-years Apart.

A cross-sectional survey was conducted in 2014–2016 in 301 ruminant herds to estimate C. jejuni and C. coli prevalence, and investigate their susceptibility to antimicrobials. Risk of shedding C. jejuni was higher in cattle than sheep (81.2% vs. 45.2%; ORadj = 5.22, p < 0.001), whereas risk of shedding C. coli was higher in sheep than in cattle (19.1% vs. 11.3%; ORadj = 1.71, p = 0.128). Susceptibility to six antimicrobials was determined by broth microdilution using European Committee for Antimicrobial Susceptibility Testing (EUCAST) epidemiological cut-off values. C. coli exhibited higher resistance (94.1%, 32/34) than C. jejuni (65.1%, 71/109), and resistance was more widespread in isolates from dairy cattle than beef cattle or sheep. Compared to results obtained 10-years earlier (2003–2005) in a similar survey, an increase in fluoroquinolone-resistance was observed in C. jejuni from beef cattle (32.0% to 61.9%; OR = 3.45, p = 0.020), and a decrease in tetracycline-resistance in C. jejuni from dairy cattle (75.0% to 43.2%; OR = 0.25, p = 0.026). Resistance to macrolides remained stable at low rates and restricted to C. coli from dairy cattle, with all macrolide-resistant C. coli showing a pattern of pan-resistance. Presence of the single nucleotide polymorphisms (SNPs) associated to quinolone and macrolide resistance was confirmed in all phenotypically resistant isolates. The increase in fluoroquinolone resistance is worrisome but susceptibility to macrolides is reassuring.

Acquisition of fluoroquinolone resistance in Campylobacter jejuni leads to an increase in biofilm formation and virulence

Campylobacter jejuni is the leading cause of bacterial gastroenteritis with over 550 million cases reported yearly. The World Health Organization has listed C. jejuni as one of 12 microorganisms on a global priority list for antibiotic resistance due to a rapid increase in the number of strains resistant to fluoroquinolone antibiotics. This fluoroquinolone resistance is conferred through a single point mutation in the QRDR region within the gyrA gene which is also involved in DNA supercoiling homeostasis. We recently revealed that changes in DNA topology play a major role in the regulation of virulence in C. jejuni with relaxation of DNA supercoiling associated with increased attachment to and invasion of human epithelial cells. The aim of this study was to investigate whether fluoroquinolone resistant strains of C. jejuni displayed altered supercoiling associated phenotypes. A panel of mutants were derived against nalidixic acid and ciprofloxacin and shown to have a greater ability to form viable biofilms under aerobic conditions and that this phenotype was associated with changes in DNA supercoiling levels. These mutants were also shown to have an increased ability to attach to and invade epithelial cells in vitro and conferred an increase in the killing efficiency of Galleria mellonella. We report for the first time that fluoroquinolone resistance in C. jejuni is associated with an increase in virulence and the ability to form viable biofilms in oxygen rich environments. These altered phenotypes may play a critical role in the continued increase in fluoroquinolone resistance observed for this important pathogen.

Rapid Identification of Different Escherichia coli Sequence Type 131 Clades

Escherichia coli sequence type 131 (ST131) is a pandemic clonal lineage that is responsible for the global increase in fluoroquinolone resistance and extended-spectrum-β-lactamase (ESBL) producers. The members of ST131 clade C, especially subclades C2 and C1-M27, are associated with ESBLs. We developed a multiplex conventional PCR assay with the ability to detect all ST131 clades (A, B, and C), as well as C subclades (C1-M27, C1-nM27 [C1-non-M27], and C2). To validate the assay, we used 80 ST131 global isolates that had been fully sequenced. We then used the assay to define the prevalence of each clade in two Japanese collections consisting of 460 ESBL-producing E. coli ST131 (2001-12) and 329 E. coli isolates from extraintestinal sites (ExPEC) (2014). The assay correctly identified the different clades in all 80 global isolates: clades A (n = 12), B (n = 12), and C, including subclades C1-M27 (n = 16), C1-nM27 (n = 20), C2 (n = 17), and other C (n = 3). The assay also detected all 565 ST131 isolates in both collections without any false positives. Isolates from clades A (n = 54), B (n = 23), and C (n = 483) corresponded to the O serotypes and the fimH types of O16-H41, O25b-H22, and O25b-H30, respectively. Of the 483 clade C isolates, C1-M27 was the most common subclade (36%), followed by C1-nM27 (32%) and C2 (15%). The C1-M27 subclade with blaCTX-M-27 became especially prominent after 2009. Our novel multiplex PCR assay revealed the predominance of the C1-M27 subclade in recent Japanese ESBL-producing E. coli isolates and is a promising tool for epidemiological studies of ST131.

Trends in antibiotic resistance in bacterial keratitis isolates from South India

AimsTo report trends in antibiotic resistance in cases of bacterial keratitis from a large eye hospital in South India.MethodsIn this retrospective cross-sectional study, the microbiology laboratory records of patients with...

Impact of fluoroquinolone resistance in Gram-negative bloodstream infections on healthcare utilization

There has been a concerning increase in fluoroquinolone resistance among Gram-negative bloodstream isolates. This retrospective cohort study examines the implications of fluoroquinolone resistance on use of healthcare resources in patients with Gram-negative bloodstream infections (BSI). Hospitalized adults with first episodes of community-onset Gram-negative BSI from 2010 to 2012 at Palmetto Health Hospitals in Columbia, SC, USA were identified. Multivariate linear regression was used to examine risk factors for prolonged hospital length of stay (HLOS) in survivors of Gram-negative BSI. Among 474 unique patients, 384 (81%) and 90 (19%) had BSI due to fluoroquinolone-susceptible (FQ-S) and fluoroquinolone non-susceptible (FQ-NS) Gram-negative bacilli, respectively. The FQ-NS bloodstream isolates, particularly Escherichia coli, were more likely than FQ-S isolates to be multi-drug resistant (56% versus 6%, p < 0.001). Compared with patients with BSI due to FQ-S bloodstream isolates, those with FQ-NS isolates were more likely to receive inappropriate empirical antimicrobial therapy (26% versus 3%, p < 0.001), have longer mean HLOS (11.6 versus 9.3 days, p 0.03) and treatment duration with intravenous antibiotics during hospitalization (9.1 versus 7.1 days, p 0.001), and use outpatient intravenous antibiotics at hospital discharge (15% versus 8%, p 0.05). After adjustments in the multivariate model, inappropriate empirical antimicrobial therapy was an independent risk factor for prolonged HLOS in survivors of Gram-negative BSI (parameter estimate 3.65 days, 95% CI 0.43–6.86). Multi-drug resistance among FQ-NS bloodstream isolates limits both empirical and definitive antimicrobial treatment options and poses excessive burdens on the healthcare system.

Induction of Prophages by Fluoroquinolones in Streptococcus pneumoniae: Implications for Emergence of Resistance in Genetically-Related Clones

Antibiotic resistance in Streptococcus pneumoniae has increased worldwide by the spread of a few clones. Fluoroquinolone resistance occurs mainly by alteration of their intracellular targets, the type II DNA topoisomerases, which is acquired either by point mutation or by recombination. Increase in fluoroquinolone-resistance may depend on the balance between antibiotic consumption and the cost that resistance imposes to bacterial fitness. In addition, pneumococcal prophages could play an important role. Prophage induction by fluoroquinolones was confirmed in 4 clinical isolates by using Southern blot hybridization. Clinical isolates (105 fluoroquinolone-resistant and 160 fluoroquinolone-susceptible) were tested for lysogeny by using a PCR assay and functional prophage carriage was studied by mitomycin C induction. Fluoroquinolone-resistant strains harbored fewer inducible prophages (17/43) than fluoroquinolone-susceptible strains (49/70) (P = 0.0018). In addition, isolates of clones associated with fluoroquinolone resistance [CC156 (3/25); CC63 (2/20), and CC81 (1/19)], had lower frequency of functional prophages than isolates of clones with low incidence of fluoroquinolone resistance [CC30 (4/21), CC230 (5/20), CC62 (9/21), and CC180 (21/30)]. Likewise, persistent strains from patients with chronic respiratory diseases subjected to fluoroquinolone treatment had a low frequency of inducible prophages (1/11). Development of ciprofloxacin resistance was tested with two isogenic strains, one lysogenic and the other non-lysogenic: emergence of resistance was only observed in the non-lysogenic strain. These results are compatible with the lysis of lysogenic isolates receiving fluoroquinolones before the development of resistance and explain the inverse relation between presence of inducible prophages and fluoroquinolone-resistance.

Retrospective analysis of fluoroquinolone prophylaxis in patients undergoing allogeneic hematopoietic stem cell transplantation

Patients undergoing allogeneic hematopoietic stem cell transplant are at a high risk for infection-related mortality in the immediate post-transplantation phase. Prophylaxis with a fluoroquinolone is now recommended to reduce this risk with the stipulation that surveillance for increased fluoroquinolone resistance Clostridium difficile associated diarrhea be conducted. We conducted a retrospective chart review of 48 patients who underwent an allogeneic hematopoietic stem cell transplant and received a fluoroquinolone for prophylaxis and 48 patients who underwent an allogeneic hematopoietic stem cell transplant who did not receive a fluoroquinolone for prophylaxis. All patients received the same standard antifungal, antiviral and anti-pneumocystis prophylaxis. Patients receiving fluoroquinolone prophylaxis had a lower incidence of febrile neutropenia than those not receiving prophylaxis, though the difference was not found to be statistically significant (83% vs. 67%, p = 0.098). Similar non-significant improvements in the number of positive cultures recovered during an episode of febrile neutropenia and antimicrobial days were noted. No significant increase in fluoroquinolone resistance, Clostridium difficile associated diarrhea, or in methicillin resistant Staphylococcus aureus infections were noted. Our single institution experience with fluoroquinolone prophylaxis for allogeneic hematopoietic stem cell transplant patients supports continuation of this practice. Expansion to autologous hematopoietic stem cell transplant patients may be appropriate based on guideline recommendations and our institution-specific experience with fluoroquinolone prophylaxis.

Resistance surveillance studies: a multifaceted problem—the fluoroquinolone example

This review summarizes data on the fluoroquinolone resistance epidemiology published in the previous 5 years. The data reviewed are stratified according to the different prescription patterns by either primary- or tertiary-care givers and by indication. Global surveillance studies demonstrate that fluoroquinolone- resistance rates increased in the past several years in almost all bacterial species except Staphylococcus pneumoniae and Haemophilus influenzae causing community-acquired respiratory tract infections (CARTIs), as well as Enterobacteriaceae causing community-acquired urinary tract infections. Geographically and quantitatively varying fluoroquinolone resistance rates were recorded among Gram-positive and Gram-negative pathogens causing healthcare-associated respiratory tract infections. One- to two-thirds of Enterobacteriaceae producing extended-spectrum β-lactamases (ESBLs) were fluoroquinolone resistant too, thus, limiting the fluoroquinolone use in the treatment of community- as well as healthcare-acquired urinary tract and intra-abdominal infections. The remaining ESBL-producing or plasmid-mediated quinolone resistance mechanisms harboring Enterobacteriaceae were low-level quinolone resistant. Furthermore, 10-30 % of H. influenzae and S. pneumoniae causing CARTIs harbored first-step quinolone resistance determining region (QRDR) mutations. These mutants pass susceptibility testing unnoticed and are primed to acquire high-level fluoroquinolone resistance rapidly, thus, putting the patient at risk. The continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some current guidelines for the treatment of intra-abdominal infections or even precludes the use of fluoroquinolones in certain indications like gonorrhea and pelvic inflammatory diseases in those geographic areas in which fluoroquinolone resistance rates and/or ESBL production is high. Fluoroquinolone resistance has been selected among the commensal flora colonizing the gut, nose, oropharynx, and skin, so that horizontal gene transfer between the commensal flora and the offending pathogen as well as inter- and intraspecies recombinations contribute to the emergence and spread of fluoroquinolone resistance among pathogenic streptococci. Although interspecies recombinations are not yet the major cause for the emergence of fluoroquinolone resistance, its existence indicates that a large reservoir of fluoroquinolone resistance exists. Thus, a scenario resembling that of a worldwide spread of β-lactam resistance in pneumococci is conceivable. However, many resistance surveillance studies suffer from inaccuracies like the sampling of a selected patient population, restricted geographical sampling, and undefined requirements of the user, so that the results are biased. The number of national centers is most often limited with one to two participating laboratories, so that such studies are point prevalence but not surveillance studies. Selected samples are analyzed predominantly as either hospitalized patients or patients at risk or those in whom therapy failed are sampled; however, fluoroquinolones are most frequently prescribed by the general practitioner. Selected sampling results in a significant over-estimation of fluoroquinolone resistance in outpatients. Furthermore, the requirements of the users are often not met; the prescribing physician, the microbiologist, the infection control specialist, public health and regulatory authorities, and the pharmaceutical industry have diverse interests, which, however, are not addressed by different designs of a surveillance study. Tools should be developed to provide customer-specific datasets. Consequently, most surveillance studies suffer from well recognized but uncorrected biases or inaccuracies. Nevertheless, they provide important information that allows the identification of trends in pathogen incidence and antimicrobial resistance.

Global fluoroquinolone resistance epidemiology and implictions for clinical use.

This paper on the fluoroquinolone resistance epidemiology stratifies the data according to the different prescription patterns by either primary or tertiary caregivers and by indication. Global surveillance studies demonstrate that fluoroquinolone resistance rates increased in the past years in almost all bacterial species except S. pneumoniae and H. influenzae, causing community-acquired respiratory tract infections. However, 10 to 30% of these isolates harbored first-step mutations conferring low level fluoroquinolone resistance. Fluoroquinolone resistance increased in Enterobacteriaceae causing community acquired or healthcare associated urinary tract infections and intraabdominal infections, exceeding 50% in some parts of the world, particularly in Asia. One to two-thirds of Enterobacteriaceae producing extended spectrum β-lactamases were fluoroquinolone resistant too. Furthermore, fluoroquinolones select for methicillin resistance in Staphylococci. Neisseria gonorrhoeae acquired fluoroquinolone resistance rapidly; actual resistance rates are highly variable and can be as high as almost 100%, particularly in Asia, whereas resistance rates in Europe and North America range from <10% in rural areas to >30% in established sexual networks. In general, the continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some guidelines, for example, treatment of urinary tract, intra-abdominal, skin and skin structure infections, and traveller's diarrhea, or even precludes the use in indications like sexually transmitted diseases and enteric fever.

Fluoroquinolone resistance in Escherichia coli and Klebsiella pneumoniae over 18 years: effect of different systems for eliminating duplicates

Sir, The increase in resistance of Gram-negative bacilli is a serious public health problem and our aim was to determine the effect of different duplicate elimination criteria on the evolution of fluoroquinolone resistance in Escherichia coli and Klebsiella pneumoniae in our setting over a period of 18 years. The criteria used are described in Figure 1. Antibiotic susceptibility was studied using microdilution with the Wider semiautomatic system (Soria Melguizo, Spain) and Etest (AB Biodisk, Solna, Sweden), following CLSI (formerly NCCLS) recommendations. In E. coli, the mean percentage of fluoroquinolone-resistant strains according to the EARS-Net criterion was greater than that detected using the CLSI criterion, both when the total number of strains and when the number of extended-spectrum b-lactamase (ESBL)-producing strains was considered (28.4% versus 22.4% and 65.2% versus 60.5%, respectively). With regard to K. pneumoniae, we obtained 7.2% versus 6.3% and 52.2% versus 40.0%. Analysis of the criterion of time showed that when the period considered for elimination of duplicates increased, the ciprofloxacin resistance rate also increased compared with the CLSI criterion. When the EARS-Net criterion was applied, the prevalence of these microorganisms increased in both hospitalized and non-hospitalized patients, although this phenomenon was more important in the former than in the latter. All data are shown in Table 1. The increase in fluoroquinolone resistance is a serious public health problem, especially in ESBL-producing strains, for which the therapeutic options are far more limited, and the local epidemiology of resistance has been considered a key tool in the control of this process. It is essential to apply a duplicate elimination criterion, since analysis of the data based on the total criterion does not reflect the real situation of resistance. What has not yet been definitively established is which criterion is the best to use in each case. The first isolate from each patient is an objective criterion, but has serious limitations since the same patient may frequently be infected by different strains of the same species during the course of their disease and hospital stay, or a strain may become resistant during treatment of the patient due to the selection of resistant mutants during antibiotic therapy. The EARS-Net criterion reflects more faithfully the real situation of resistance, but suggests that it is necessary to apply strict quality control in phenotypic microbiological studies to detect resistance. Our study suggests that the new EARS-Net method of studying duplicates should be applied in order to detect changes in resistance patterns that may occur during the course of disease due to mutations of the microorganism causing the infection or superinfections by more resistant microorganisms.

Fluoroquinolone-ResistantMycobacterium tuberculosis, Pakistan, 2005–2009

To the Editor: Pakistan is 1 of 22 countries listed by the World Health Organization (WHO) as having a high incidence of tuberculosis (TB). We recently reported an increase in rates of multidrug-resistant (MDR) TB with emergence of extensively drug-resistant TB (1). Fluoroquinolone resistance is associated with worse outcome in patients with MDR TB (2). Recent evidence suggests emergence and increasing incidence of fluoroquinolone-resistant Mycobacterium tuberculosis from several countries, particularly in MDR strains (3). We present data from a tertiary care referral center laboratory in Pakistan to assess fluoroquinolone resistance in MDR TB strains during 2005–2009. The Aga Khan University Hospital and its clinical laboratory have been accredited by the Joint Commission of International Accreditation and designated as a technical partner of the National TB Program. M. tuberculosis susceptibility testing is also periodically validated by the WHO Supranational Reference Laboratory network. The microbiology laboratory serves different cities across Pakistan with ≈180 peripheral collection units. Specimens for TB cultures are requested by physicians and received through passive collection and thus are not restricted to programmed surveys. All specimens received at each of the collection units are sent to the central laboratory in Karachi for culture and drug susceptibility testing (DST). Specimens reach the main laboratory within 24 hours after receipt. During the past 4 years, the laboratory has received 12,000–15,000 specimens annually for M. tuberculosis culture; positivity rate has been 15%–20%. Culture and DST are performed at the laboratory in accordance with Clinical Laboratory Standards Institute and WHO recommendations, as described (4). During 2005–2008, fluoroquinolone susceptibilities for all MDR and polydrug-resistant isolates were determined by using ciprofloxacin (2 μg/mL). From 2009 onwards, fluoroquinolone susceptibilities were determined by using ofloxacin (2 μg/mL), and second-line DST was performed for all M. tuberculosis isolates. During 2005–2009, a total of 11,263 cultures were reported positive for M. tuberculosis. Of these, 34.4% were MDR, and 50.1% were sensitive to all 4 first-line agents (isoniazid, rifampin, pyrazinamide, ethambutol). Because of inconsistencies in testing criteria for fluoroquinolones (fluoroquinolone testing being conducted primarily for MDR cases during 2005–2008), the overall fluoroquinolone-resistance rate could not be determined. However, for MDR strains, fluoroquinolone susceptibilities were consistently determined, and resistance rates increased from 17.41% in 2005 to 42.92% in 2009 (p<0.001, by χ2 test for trend analysis) (Table). A progressive increase in fluoroquinolone use and its association with increase in resistance against organisms other than M. tuberculosis have been reported from Pakistan (5). We report a progressive increase in fluoroquinolone resistance rate in MDR M. tuberculosis isolates during a 5-year period. This finding is consistent with those of several studies reporting fluoroquinolone resistance from the region. Agrawal et al. have recently reported an exponential increase in fluoroquinolone resistance in India from 3% in 1996 to 35% in 2004 (6). A significant increase in fluoroquinolone resistance from 7.7% to 20% in MDR TB was also reported from Taiwan (7); the authors correlated this finding with the inappropriate use of fluoroquinolones for managing TB rather than with fluoroquinolone misuse in the community. Another study from the United States and Canada reported 4.1% fluoroquinolone resistance in MDR TB strains (8). In addition to detecting increasing fluoroquinolone resistance in MDR isolates, we have also detected fluoroquinolone resistance in non-MDR, polydrug-resistant M. tuberculosis isolates. Moreover, in 2009, a total of 3.1% of isolates susceptible to all first-line agents were fluoroquinolone resistant. Although our dataset includes samples from throughout Pakistan, sampling limitations prevent us from deriving definite conclusions and generalizing results to the entire population of the country. A referral bias attributable to passive sampling exists because cases referred to our laboratory tend to be more complicated. Moreover, treatment history was not available for patients in our dataset; therefore, increased fluoroquinolone resistance could not be correlated with prior fluoroquinolone use. However, our findings have implications for therapy with fluoroquinolones for TB and other infections. Fluoroquinolones are freely available as over-the-counter medications to the general population (9), which creates potential for misuse of fluoroquinolones by the general population for TB and several other infections, such as enteric fever and genitourinary infections. Furthermore, because national guidelines for treating enteric fever and genitourinary infections do not exist, these drugs are also overprescribed by physicians. We propose control of over-the-counter availability of fluoroquinolones and judicious use of this class of drugs by physicians to prevent further escalation in resistance rates in Pakistan. Table Resistance patterns and fluoroquinolone resistance rates of Mycobacterium tuberculosis isolates from the Aga Khan University Hospital laboratory, Karachi, Pakistan, 2005–2009*