The effect of daily usage of Listerine Cool Mint mouthwash on the oropharyngeal microbiome: a substudy of the PReGo trial.

Introduction. ListerineÒ is a bactericidal mouthwash widely used to prevent oral health problems such as dental plaque and gingivitis. However, whether it promotes or undermines a healthy oral microbiome is unclear.Hypothesis/Gap Statement. We hypothesized that the daily use of Listerine Cool Mint would have a significant impact on the oropharyngeal microbiome.Aim. We aimed to assess if daily usage of Listerine Cool Mint influenced the composition of the pharyngeal microbiome.Methodology. The current microbiome substudy is part of the Preventing Resistance in Gonorrhoea trial. This was a double-blind single-centre, crossover, randomized controlled trial of antibacterial versus placebo mouthwash to reduce the incidence of gonorrhoea/chlamydia/syphilis in men who have sex with men (MSM) taking HIV pre-exposure prophylaxis (PrEP). Fifty-nine MSM taking HIV PrEP were enrolled. In this crossover trial, participants received 3 months of daily Listerine followed by 3 months of placebo mouthwash or vice versa. Oropharyngeal swabs were taken at baseline and after 3 months use of each mouthwash. DNA was extracted for shotgun metagenomic sequencing (Illumina Inc.). Non-host reads were taxonomically classified with MiniKraken and Bracken. The alpha and beta diversity indices were compared between baseline and after each mouthwash use. Differentially abundant bacterial taxa were identified using ANOVA-like differential expression analysis.Results. Streptococcus was the most abundant genus in most samples (n = 103, 61.7 %) with a median relative abundance of 31.5% (IQR 20.6-44.8), followed by Prevotella [13.5% (IQR 4.8-22.6)] and Veillonella [10.0% (IQR 4.0-16.8)]. Compared to baseline, the composition of the oral microbiome at the genus level (beta diversity) was significantly different after 3 months of Listerine (P = 0.006, pseudo-F = 2.29) or placebo (P = 0.003, pseudo-F = 2.49, permutational multivariate analysis of variance) use. Fusobacterium nucleatum and Streptococcus anginosus were significantly more abundant after Listerine use compared to baseline.Conclusion. Listerine use was associated with an increased abundance of common oral opportunistic bacteria previously reported to be enriched in periodontal diseases, oesophageal and colorectal cancer, and systemic diseases. These findings suggest that the regular use of Listerine mouthwash should be carefully considered.

Long-term effects of ciprofloxacin treatment on the gastrointestinal and oropharyngeal microbiome are more pronounced after longer antibiotic courses.

BACKGROUND: Urinary tract infections (UTIs) are one of the main reasons for antibiotic prescriptions in primary care. Recent studies demonstrate similar clinical outcomes with short vs. long antibiotics courses. The aim of this study was to investigate the differential collateral effect of ciprofloxacin treatment duration on the gastrointestinal and oropharyngeal microbiome in patients presenting with uncomplicated UTI to primary care practices in Switzerland, Belgium and Poland. METHODS: Stool and oropharyngeal samples were obtained from 36 treated patients and 14 controls at the beginning of antibiotic therapy, end of therapy and one month after the end of therapy. Samples underwent shotgun metagenomics. RESULTS: At the end of therapy, patients treated with both short (≤7 days) and long (>7 days) ciprofloxacin courses showed similar changes in the gastrointestinal microbiome compared to non-treated controls. After one month, most changes in patients receiving short courses were reversed; however, long courses led to increased abundance of the genera Roseburia, Faecalicatena and Escherichia. Changes in the oropharynx were minor and reversed to baseline levels within one month. Ciprofloxacin resistance encoding mutations in gyrA/B and parC/E reads were observed in both short and long treatment groups but decreased to baseline levels after one month. An increased abundance of resistance genes was observed in the gastrointestinal microbiome after longer treatment, and correlated to increased prevalence of aminoglycoside, ß-lactam, sulphonamide, and tetracycline resistance genes. CONCLUSION: Collateral effects on the gastrointestinal community, including an increased prevalence of antimicrobial resistance genes, persists for up to at least one month following longer ciprofloxacin therapy. These data support the use of shorter antimicrobial treatment duration.

Molecular pathways to high-level azithromycin resistance in Neisseria gonorrhoeae.

BACKGROUND: The prevalence of azithromycin resistance in Neisseria gonorrhoeae is increasing in numerous populations worldwide. OBJECTIVES: To characterize the genetic pathways leading to high-level azithromycin resistance. METHODS: A customized morbidostat was used to subject two N. gonorrhoeae reference strains (WHO-F and WHO-X) to dynamically sustained azithromycin pressure. We tracked stepwise evolution of resistance by whole genome sequencing. RESULTS: Within 26 days, all cultures evolved high-level azithromycin resistance. Typically, the first step towards resistance was found in transitory mutations in genes rplD, rplV and rpmH (encoding the ribosomal proteins L4, L22 and L34 respectively), followed by mutations in the MtrCDE-encoded efflux pump and the 23S rRNA gene. Low- to high-level resistance was associated with mutations in the ribosomal proteins and MtrCDE efflux pump. However, high-level resistance was consistently associated with mutations in the 23S ribosomal RNA, mainly the well-known A2059G and C2611T mutations, but also at position A2058G. CONCLUSIONS: This study enabled us to track previously reported mutations and identify novel mutations in ribosomal proteins (L4, L22 and L34) that may play a role in the genesis of azithromycin resistance in N. gonorrhoeae.

Estimating the association between antibiotic exposure and colonization with extended-spectrum ß-lactamase-producing Gram-negative bacteria using machine learning methods: a multicentre, prospective cohort study.

OBJECTIVES: The aim of the study was to measure the impact of antibiotic exposure on the acquisition of colonization with extended-spectrum ß-lactamase-producing Gram-negative bacteria (ESBL-GNB) accounting for individual- and group-level confounding using machine-learning methods. METHODS: Patients hospitalized between September 2010 and June 2013 at six medical and six surgical wards in Italy, Serbia and Romania were screened for ESBL-GNB at hospital admission, discharge, antibiotic start, and after 3, 7, 15 and 30 days. Primary outcomes were the incidence rate and predictive factors of new ESBL-GNB colonization. Random forest algorithm was used to rank antibiotics according to the risk of selection of ESBL-GNB colonization in patients not colonized before starting antibiotics. RESULTS: We screened 10 034 patients collecting 28 322 rectal swab samples. New ESBL-GNB colonization incidence with and without antibiotic treatment was 22/1000 and 9/1000 exposure-days, respectively. In the adjusted regression analyses, antibiotic exposure (hazard ratio (HR) 2.38; 95% CI 1.29-4.40), age 60-69 years (HR 1.19; 95% CI 1.05-1.34), and spring season (HR 1.25; 95% CI 1.14-1.38) were independently associated with new colonization. Monotherapy ranked higher als combination therapy in promoting ESBL-GNB colonization. Among monotherapy, cephalosporins ranked first followed by tetracycline (second), macrolide (fourth) and cotrimoxazole (seventh). Overall the ranking of cephalosporins was lower when used in combination. Among combinations not including cephalosporins, quinolones plus carbapenems ranked highest (eighth). Among sequential therapies, quinolones ranked highest (tenth) when prescribed within 30 days of therapy with cephalosporins. CONCLUSIONS: Impact of antibiotics on selecting ESBL-GNB at intestinal level varies if used in monotherapy or combination and according to previous antibiotic exposure. These finding should be explored in future clinical trials on antibiotic stewardship interventions. CLINICAL TRIAL REGISTRATION: NCT01208519.

Remarkable geographical variations between India and Europe in carriage of the staphylococcal surface protein-encoding sasX/sesI and in the population structure of methicillin-resistant Staphylococcus aureus belonging to clonal complex 8.

OBJECTIVES: sasX is a colonization-virulence factor that potentially underlies the success of methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST) 239 in Asia. We aimed to study the spread of sasX and the population structure of MRSA in two geographically distinct regions, Europe and India. METHODS: MRSA (n = 128) from screening and clinical samples from tertiary care patients in 12 European countries (n = 119), and from India (n = 9) were multilocus-sequence-typed and screened for sasX and its carrier φSPß-like prophage by PCR. Whole genome sequencing was performed on sasX-harbouring strains from India (n = 5) and Europe (n = 2) and on a selection non-harbouring sasX (n = 36) (2 × 150 bp, Miseq, Illumina). Reads were mapped to the ST239 reference strain, TW20. RESULTS: sasX and sesI, a sasX homologue native to Staphylococcus epidermidis, were detected in five of the nine Indian MRSA belonging to ST239 and to other sequence types of CC8. In contrast, sasX was restricted to two ST239 strains in Europe. The intact sasX and sesI carrier φSPß-like prophages were ∼80 kb and ∼118 kb, and integrated in the yeeE gene. We identified 'novel' ST239 clades in India and Serbia that showed significant differences in base substitution frequencies (0.130 and 0.007, respectively, Tamura-Nei model) (p <0.05). CONCLUSIONS: Our data highlight dissemination of sasX to non-ST239 sequence types of CC8. Detection of the S. epidermidis-associated sesI in MRSA provided unquestionable evidence of transfer between the two species. Stark differences in evolutionary rates between the novel Indian and Serbian ST239 clades identified here might be due to inherent clade characteristics or influenced by other environmental differences such as antibiotic use.

Effect of outpatient antibiotics for urinary tract infections on antimicrobial resistance among commensal Enterobacteriaceae: a multinational prospective cohort study.

OBJECTIVES: We quantified the impact of antibiotics prescribed in primary care for urinary tract infections (UTIs) on intestinal colonization by ciprofloxacin-resistant (CIP-RE) and extended-spectrum ß-lactamase-producing Enterobacteriaceae (ESBL-PE), while accounting for household clustering. METHODS: Prospective cohort study from January 2011 to August 2013 at primary care sites in Belgium, Poland and Switzerland. We recruited outpatients requiring antibiotics for suspected UTIs or asymptomatic bacteriuria (exposed patients), outpatients not requiring antibiotics (non-exposed patients), and one to three household contacts for each patient. Faecal samples were tested for CIP-RE, ESBL-PE, nitrofurantoin-resistant Enterobacteriaceae (NIT-RE) and any Enterobacteriaceae at baseline (S1), end of antibiotics (S2) and 28 days after S2 (S3). RESULTS: We included 300 households (205 exposed, 95 non-exposed) with 716 participants. Most exposed patients received nitrofurans (86; 42%) or fluoroquinolones (76; 37%). CIP-RE were identified in 16% (328/2033) of samples from 202 (28%) participants. Fluoroquinolone treatment caused transient suppression of Enterobacteriaceae (S2) and subsequent two-fold increase in CIP-RE prevalence at S3 (adjusted prevalence ratio (aPR) 2.0, 95% CI 1.2-3.4), with corresponding number-needed-to-harm of 12. Nitrofurans had no impact on CIP-RE (aPR 1.0, 95% CI 0.5-1.8) or NIT-RE. ESBL-PE were identified in 5% (107/2058) of samples from 71 (10%) participants, with colonization not associated with antibiotic exposure. Household exposure to CIP-RE or ESBL-PE was associated with increased individual risk of colonization: aPR 1.8 (95% CI 1.3-2.5) and 3.4 (95% CI 1.3-9.0), respectively. CONCLUSIONS: These findings support avoidance of fluoroquinolones for first-line UTI therapy in primary care, and suggest potential for interventions that interrupt household circulation of resistant Enterobacteriaceae.

Fatty acid kinase A is an important determinant of biofilm formation in Staphylococcus aureus USA300.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA)-USA300 is notorious for its ability to cause community- and healthcare-acquired infections, which are even more difficult to treat when associated with a biofilm phenotype. We aimed to characterize the genetic determinants of biofilm formation in a USA300 skin abscess isolate (UAS391) that formed prolific biofilms. METHODS: USA300 S. aureus strains, TCH1516 and FPR3757, were found to be closely related based on whole genome mapping (Argus™ Optical Mapping System, Opgen Inc, Gaithersburg, USA) to UAS391 (96.3-99.1 % similarity, P=0.0151), however differed markedly in biofilm formation (P=0.0001) on a dynamic assay (BioFlux 200, Fluxion Biosciences, USA). Comparison of whole genome sequences of these strains identified differences in a total of 18 genes. Corresponding Tn (bursa aurealis-bearing) knockout mutants in these target genes were obtained from a publicly available mutant library of the same clonal lineage (USA300-JE2) and were characterized phenotypically for biofilm formation. Tn mutants showing significant differences in biofilm formation were utilized for transduction into a plasmid-cured erythromycin-sensitive derivative of UAS391 and for complementation experiments. All strains were tested on the dynamic assay, and 17h-biofilms were stained (SYTO9, Life Technologies) and fluorescence intensity quantified by microscopy (Zeiss, ImageJ). Gene expression levels in Tn and transduced mutants were studied by quantitative reverse transcriptase PCR (StepOnePlusTM, Applied Biosystems®). RESULTS: Comparison of the sequenced genomes of TCH1516, FPR3757 and UAS391 yielded a limited number of variant genes (n=18) that were hypothesized to account for the observed difference in biofilm-forming capacity. Screening of Tn mutants disrupted in these target genes identified one mutant (NE229) bearing a transposon insertion in SAUSA300_1119 (fakA), which exhibited increased biofilm formation similar to UAS391 (P=0.9320). Transduction experiments confirmed that fakA::Tn corresponded to 1.9- to 4.6-fold increase in biofilm formation depending on the USA300 strain background (P≤0.0007), while complementation of the TCH1516 wild-type fakA allele in UAS391 resulted in a 4.3-fold reduction in biofilm formation (P<0.0001). CONCLUSIONS: This sequential approach, consisting of strain typing, genome comparison and functional genomics, identified fakA, a recently described fatty acid kinase in S. aureus that is essential for phospholipid synthesis and also impacts the transcription of numerous virulence factors, as a negative regulator of biofilm formation in S. aureus USA300.

Collateral damage from oral ciprofloxacin versus nitrofurantoin in outpatients with urinary tract infections: a culture-free analysis of gut microbiota.

Recent treatment guidelines for uncomplicated urinary tract infections (UTIs) discourage fluoroquinolone prescription because of collateral damage to commensal microbiota, but the ecologic impact of alternative agents has not been evaluated by culture-free techniques. We prospectively collected faecal samples at three time points from ambulatory patients with UTIs treated with ciprofloxacin or nitrofurantoin, patients not requiring antibiotics and household contacts of ciprofloxacin-treated patients. We described changes in gut microbiota using a culture-independent approach based on pyrosequencing of the V3-V4 region of the bacterial 16S rRNA gene. All groups were similar at baseline. Ciprofloxacin had a significant global impact on the gut microbiota whereas nitrofurantoin did not. The end of ciprofloxacin treatment correlated with a reduced proportion of Bifidobacterium (Actinobacteria), Alistipes (Bacteroidetes) and four genera from the phylum Firmicutes (Faecalibacterium, Oscillospira, Ruminococcus and Dialister) and an increased relative abundance of Bacteroides (Bacteroidetes) and the Firmicutes genera Blautia, Eubacterium and Roseburia. Substantial recovery had occurred 4 weeks later. Nitrofurantoin treatment correlated with a reduced relative proportion of the genus Clostridium and an increased proportion of the genus Faecalibacterium. This study supports use of nitrofurantoin over fluoroquinolones for treatment of uncomplicated UTIs to minimize perturbation of intestinal microbiota.

A longitudinal study of Staphylococcus aureus colonization in pigs in Ireland.

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) in livestock has refocused attention on S. aureus colonization and transmission in pigs. This study investigated the effect of the S. aureus colonization status of a sow on the colonization status of her piglets, and whether pigs carry the same strain of S. aureus throughout production. Nasal swabs were collected from the piglets of six healthy sows two days after birth and two days before and two days after they were moved into each production stage. The average prevalence of S. aureus colonization varied between 26% and 73%. The odds of being S. aureus positive were almost 12 times higher for piglets born to nasal-positive sows than for those born to nasal-negative sows, and three times higher again for piglets born to sows that were both nasal- and vaginal-positive. Isolates recovered from piglets immediately after birth were indistinguishable from those of the dam as determined by phenotypic and molecular typing, including microarray analysis and optical mapping. All isolates belonged to clonal complex 9 and the majority exhibited a novel spa type, t10449. The findings show that the S. aureus colonization status of the sow influences the colonization status of her piglets in the early production stages but strains carried by pigs change over time. Multiresistant S. aureus was detected, in particular post-weaning. Results suggest that sow status and management practices, including mixing of pigs and antimicrobial usage at weaning, should be considered when implementing control measures for S. aureus on a farm.

High rates of intestinal colonisation with fluoroquinolone-resistant ESBL-harbouring Enterobacteriaceae in hospitalised patients with antibiotic-associated diarrhoea.

The purposes of this study were to investigate the intestinal carriage of extended-spectrum ß-lactamase-harbouring Enterobacteriaceae (ESBL-EN) and associated fluoroquinolone resistance (FQ-R) in 120 hospitalised patients with antibiotic-associated diarrhoea, and to investigate a correlation between Clostridium difficile (C. difficile) infection and intestinal colonisation with ESBL-EN in these patients. Stool samples were screened for C. difficile infection by toxin A/B enzyme-linked immunosorbent assay (ELISA) and for the presence of enterobacterial isolates producing ß-lactamases by plating on ß-lactamase screening (BLSE) agar. Recovered isolates were confirmed pheno- and genotypically for the presence of ESBL genes (bla CTX-M, bla TEM, bla SHV) by the double-disc synergy test and polymerase chain reaction (PCR) sequencing, and tested for the presence of topoisomerase mutations (gyrA, parC) and plasmid-mediated quinolone resistance (PMQR) determinants [qnrA, qnrB, qnrS, qepA, aac(6')-Ib-cr] by PCR sequencing. ESBL-EN were detected in 44/120 (37 %) stool samples. C. difficile-infected patients showed a significantly higher frequency of intestinal colonisation with ESBL-EN compared to C. difficile non-infected patients (62 % vs. 31 %, p = 0.008). Of the 73 ESBL-EN recovered, 46 (63 %) showed high-level FQ-R [ciprofloxacin minimum inhibitory concentration (MIC) ≥32 mg/L]. The largest group consisted of 21 bla CTX-M-15-harbouring Enterobacteriaceae (ciprofloxacin MIC ≥64 mg/L) with multiple topoisomerase mutations in gyrA and parC, in combination with co-carriage of aac(6')-Ib-cr. Most of them were Escherichia coli isolates belonging to sequence types ST131 and ST410. We found remarkably high rates of intestinal colonisation with high-level FQ-R ESBL-EN in hospitalised patients with antibiotic-associated diarrhoea, especially among C. difficile-infected patients. These data underscore the need for stringent infection control to contain this potentially infectious and multidrug-resistant reservoir.

Complete Genome Sequences of Two Prolific Biofilm-Forming Staphylococcus aureus Isolates Belonging to USA300 and EMRSA-15 Clonal Lineages.

Methicillin-resistant Staphylococcus aureus (MRSA) causes serious infections that are even more difficult to treat when associated with a biofilm phenotype that facilitates evasion of the host immune system and antibiotics. As a first step toward understanding the mechanisms underlying biofilm formation, we sequenced the genomes of two prolific biofilm-forming strains belonging to the two most important globally disseminated clonal lineages, USA300 and EMRSA-15.

A multinational study of colonization with extended spectrum ß-lactamase-producing Enterobacteriaceae in healthcare personnel and family members of carrier patients hospitalized in rehabilitation centres.

The study aims were: (i) to define the prevalence of and risk factors for colonization by extended spectrum ß-lactamase (ESBL) -producing Enterobacteriaceae (EPE) among healthcare workers (HCWs) and family members (FMs) of EPE-colonized patients in rehabilitation units and (ii) to compare EPE isolates from these three groups. The study included 286 FMs of 194 EPE-carrying patients identified in five rehabilitation units located in Israel, Italy, France and Spain. The EPE were detected in rectal swabs from 26 (9%) of 286 FMs screened. In multivariate analyses, older age of FM, greater mean number of hours spent with the patient, being a daughter or a female spouse of a patient, and chronic lung disease of the patient were significantly associated with carriage in the FM. Escherichia coli was the most common organism (76%), followed by Klebsiella pneumoniae (19%). Isolates were typed by pulsed field gel electrophoresis and multilocus sequence typing, and ESBLs were identified by PCR sequencing. A comparison of paired species isolates from FMs and their respective patient showed that 17 of 23 strains were indistinguishable. EPE were detected in 35 (3.5%, E. coli = 34) of the 1001 HCWs screened. Feeding patients was associated with EPE carriage by HCWs. Only 7 of 23 E. coli subclones cultured from HCWs were also represented among 376 patient-derived ESBL-producing E. coli isolates from the same rehabilitation units. In Spain, a higher proportion of HCWs and FMs were ESBL carriers than elsewhere (p <0.05). In conclusion, the molecular and epidemiological data suggest that FMs are at higher risk of EPE acquisition from their relative patients than HCWs.

Comparative population analysis of Klebsiella pneumoniae strains with extended-spectrum ß-lactamases colonizing patients in rehabilitation centers in four countries.

The international project MOSAR was conducted in five rehabilitation centers; patients were screened for rectal carriage of extended-spectrum ß-lactamase (ESBL)-producing members of the Enterobacteriaceae. Among 229 Klebsiella pneumoniae isolates, four clonal groups (CG) or complexes (CC) prevailed: CG17 in France, CG101 in Italy, CG15 in Spain, and CC147 in Israel. ESBLs, mainly CTX-Ms, were produced by 226 isolates; three isolates expressed AmpC-like cephalosporinases. High genetic diversity of K. pneumoniae populations was observed, with specific characteristics at each center.

Risk factors for previously unknown meticillin-resistant Staphylococcus aureus carriage on admission to 13 surgical wards in Europe.

BACKGROUND: Early identification of meticillin-resistant Staphylococcus aureus (MRSA) carriers may be helpful for clinical and epidemiological reasons. AIM: To identify and compare risk factors of previously unknown MRSA carriage on admission to 13 surgical wards in France, Greece, Italy, and Spain. METHODS: The study was a prospective observational cohort study which enrolled consecutive patients screened for MRSA on admission to surgical wards. Sociodemographic data, comorbidities and possible risk factors for MRSA were recorded. A multivariate logistic regression model was used to predict probabilities of previously unknown MRSA colonization on admission based on patient characteristics. Prediction rules for MRSA carriage were developed and evaluated using the c-statistic. FINDINGS: Of 2901 patients enrolled, admission screening identified 111 (3.8%) new MRSA carriers. Independent risk factors for MRSA carriage were urinary catheterization (odds ratio: 4.4; 95% confidence interval: 2.0-9.9), nursing home residency (3.8; 1.9-7.7), chronic skin disease (2.9; 1.5-5.8), wounds/ulcers (2.4; 1.5-4.0), recent hospitalization (2.2; 1.5-3.3), diabetes (1.6, 1.02-2.5), and age >70 years (1.5; 1.03-2.3). However, risk factors varied between centres. The c-statistic for the common prediction rule for all centres was 0.64, indicating limited predictive power. CONCLUSIONS: Risk profiles for MRSA carriers vary between surgical wards in European countries. Identifying local risk factors is important, as a common European prediction rule was found to be of limited clinical value.

Clonal structure, extended-spectrum ß-lactamases, and acquired AmpC-type cephalosporinases of Escherichia coli populations colonizing patients in rehabilitation centers in four countries.

The prospective project MOSAR was conducted in five rehabilitation units: the Berck Maritime Hôpital (Berck, France), Fondazione Santa Lucia (Rome, Italy), Guttmann Institute (GI; Barcelona, Spain), and Loewenstein Hospital and Tel-Aviv Souraski Medical Center (TA) (Tel-Aviv, Israel). Patients were screened for carriage of Enterobacteriaceae resistant to expanded-spectrum cephalosporins (ESCs) from admission until discharge. The aim of this study was to characterize the clonal structure, extended-spectrum ß-lactamases (ESBLs), and acquired AmpC-like cephalosporinases in the Escherichia coli populations collected. A total of 376 isolates were randomly selected. The overall number of sequence types (STs) was 76, including 7 STs that grouped at least 10 isolates from at least three centers each, namely, STs 10, 38, 69, 131, 405, 410, and 648. These clones comprised 65.2% of all isolates, and ST131 alone comprised 41.2%. Of 54 STs observed only in one center, some STs played a locally significant role, like ST156 and ST393 in GI or ST372 and ST398 in TA. Among 16 new STs, five arose from evolution within the ST10 and ST131 clonal complexes. ESBLs and AmpCs accounted for 94.7% and 5.6% of the ESC-hydrolyzing ß-lactamases, respectively, being dominated by the CTX-M-like enzymes (79.9%), followed by the SHV (13.5%) and CMY-2 (5.3%) types. CTX-M-15 was the most prevalent ß-lactamase overall (40.6%); other ubiquitous enzymes were CTX-M-14 and CMY-2. Almost none of the common clones correlated strictly with one ß-lactamase; although 58.7% of ST131 isolates produced CTX-M-15, the clone also expressed nine other enzymes. A number of clone variants with specific pulsed-field gel electrophoresis and ESBL types were spread in some locales, potentially representing newly emerging E. coli epidemic strains.

Transmission dynamics of ESBL-producing Escherichia coli clones in rehabilitation wards at a tertiary care centre.

Increasing resistance due to the production of ESBL in Escherichia coli (ESBL-E. coli) has become a major threat to public health. Our aims were to study the incidence of ESBL-E. coli acquisition during hospitalization and the transmission rates of different ESBL-E. coli clones. This was a prospective case-control study, conducted in two geriatric rehabilitation wards in Tel-Aviv. Serial rectal cultures were collected from admission till discharge. All patient-unique ESBL-E. coli isolates were subjected to molecular typing by PFGE, MLST and determination of ESBL genes. An acquisition of ESBL-E. coli was defined as traceable when a patient with the same ST, PFGE type and ESBL gene was hospitalized in the same ward in parallel to the acquisition case. ESBL-E. colis were recovered from 125 patients out of 492 enrolled: 52 were recovered upon admission, 59 acquired ESBL-E. coli during their stay, and there was undetermined status in 14 patients. A low Norton's score was associated with acquisition (O.R. 1.14 for each point, 95% C.I. 1.01-1.29, p < 0.05). ESBL-E. coli infections (n = 9) had occurred only in ESBL-E. coli carriers. The pandemic ST131 clone was the most common (48/125). The majority of the isolates (101/125) produced CTX-M-type ESBL. Of the 59 acquisition cases, 32 were traced to another patient. In-hospital dissemination was highest in the CTX-M-27-producing ST131 and the SHV-5-producing ST372 sub-clones (acquisition/admission ratios of 17/11 and 9/3, respectively), with almost all cases traced to other patients. In conclusion, most ESBL-E. coli acquisition cases were traceable to other patients. The transmission potential varied significantly between ESBL-E. coli clones.