Overview of the epidemiological profile and laboratory detection of extended-spectrum beta-lactamases

Distribution of extended-spectrum β-lactamase producing Escherichia coli genes in an integrated poultry-fish farming system in Bogor, Indonesia

Background and Aim

The excessive use of antimicrobials in livestock farming leads to the emergence and dissemination of antimicrobial-resistant organisms. This study aimed to detect extended-spectrum β-lactamase (ESBL)-producing Escherichia coli genes in integrated poultry-fish farms in Bogor, Indonesia.

Materials and Methods

A total of 256 samples were collected from six poultry-fish farms. One hundred and seventy-five chicken cloaca swabs, 60 fish skin swabs, six pond water samples, and 15 farmer's hand swabs. ESBL-producing E. coli was confirmed through double-disk diffusion. The specific primers and probe genes for quantitative polymerase chain reaction detection of ESBL-producing E. coli targeted blaTEM, blaCTX-M, blaSHV, and blaOXA-48 genes.

Results

Among the 256 samples tested, 145 (56.6%) were positive for E. coli, and 67.6% (98/145) were identified as ESBL-producing E. coli. The most ESBL-producing E. coli isolates were obtained from chicken cloaca (78.3%, 72/92), followed by pond water (66.7%, 4/6), fish skin (47.6%, 20/42), and farmer's hand swabs (40%, 2/5). About 100% of the isolates carried the genes blaTEM and blaCTX-M, whereas 17.3% and 24.5% carried blaSHV and blaOXA-48, respectively.

Conclusion

ESBL-producing E. coli genes were investigated in chicken cloaca, fish, pond water, and farmers' hands within an interconnected poultry-fish farming operation. The ESBL-producing E. coli in chickens can transfer resistant genes to aquatic environments. The transfer could harm other aquatic species and food chains, potentially threatening human health.

Carriage of Extended Spectrum Beta Lactamase-Producing Escherichia coli: Prevalence and Factors Associated with Fecal Colonization of Dogs from a Pet Clinic in Lower Saxony, Germany

Extended spectrum beta-lactamase (ESBL)-producing Escherichia coli are an emerging problem in veterinary and human medicine. Our study concentrated on the estimation of the prevalence and factors associated with the carriage of ESBL-producing E. coli in dogs who visited a veterinary clinic in northern Germany in 2017. For this reason, 1000 patients (healthy and sick dogs) were tested, resulting in 1000 samples originating from rectal swabs. Additional data were collected using a self-reported questionnaire that was completed by the dog owner. Factors associated with ESBL carriage were considered for further modeling if p < 0.05 using a two-sided Fisher test. Using a backward elimination procedure, the variables for the final multivariable logistic regression model were identified. In total, 8.9% of the dogs tested were positive for carriage of ESBL-producing E. coli. Seven factors were associated with the colonization of dogs with ESBL-E. coli within the multivariable model, namely husbandry system (p = 0.0019, OR = 3.00; 95% CI: 1.50-6.00), contact with puppies (p = 0.0044, OR = 2.43; 95% CI: 1.32-4.46), feeding of raw meat (p = 0.011, OR = 2.28; 95% CI: 1.21-4.31), food residues (p = 0.0151, OR = 2.31; 95% CI: 1.18-4.53) and food supplements (p = 0.0487, OR = 0.426; 95% CI: 0.18-0.96), and antibiotic treatments of dogs (p = 0.0005, OR = 3.030; 95% CI: 1.62-5.68) or owners (p = 0.041, OR = 2.74; 95% CI: 1.04-7.19) prior to the study. These factors refer to the animals themselves as well as to the owners and their habits or medical treatments. Although the causality and direction of transmission from owners to their dogs cannot be proven, the factor of antibiotic treatment of the owner is clearly associated with the dog's status.

Multidrug-Resistant ESBL-Producing E. coli in Clinical Samples from the UK

Globally, cephalosporin therapy failure is a serious problem for infection control. One causative agent of cephalosporin-resistant infections is multidrug-resistant (MDR) E. coli producing extended-spectrum β-lactamases (ESBLs) and/or plasmid-encoded AmpC (pAmpC) β-lactamases. We evaluated the occurrence of ESBL/pAmpC genetic determinants in phenotypically MDR E. coli isolated from clinical samples of blood, faeces, ear effusion, urine and sputum from a UK hospital. Phenotypic resistance profiling for 18 antibiotics (from seven classes) showed that 32/35 isolates were MDR, with resistance to 4-16 of the tested antibiotics. Of the isolates, 97.1% showed resistance to ampicillin, 71.4% showed resistance to co-amoxiclav, cefotaxime, ceftazidime and ceftiofur, and 68.5% showed resistance to cefquinome. blaCTX-M, blaTEM and blaOXA-1 genes were detected in 23, 13 and 12 strains, respectively, and Intl1 was detected in 17 isolates. The most common subtypes among the definite sequence types were CTX-M-15 (40%) and TEM-1 (75%). No E. coli isolates carried pAmpC genes. Significant correlations were seen between CTX-M carriage and cefotaxime, ceftiofur, aztreonam, ceftazidime and cefquinome resistance; between blaCTX-M, blaTEM and blaOXA-1 carriage and ciprofloxacin resistance; and between Intl1 carriage and trimethoprim/sulfamethoxazole resistance. Thus, MDR phenotypes may be conferred by a relatively small number of genes. The level and pattern of antibiotic resistance highlight the need for better antibiotic therapy guidelines, including reduced use and improved surveillance.

Analysis of infections among patients with historical culture positive for extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli or Klebsiella pneumoniae: Is ESBL-targeted therapy always needed?

Objective

Among patients with a history of ESBL infection, uncertainty remains regarding whether all of these patients require ESBL-targeted therapy when presenting with a subsequent infection. We sought to determine the risks associated with a subsequent ESBL infection to help inform empiric antibiotic decisions.

Methods

A retrospective cohort study of adult patients with positive index culture for Escherichia coli or Klebsiella pneumoniae (EC/KP) receiving medical care during 2017 was conducted. Risk assessments were performed to identify factors associated with subsequent infection caused by ESBL-producing EC/KP.

Results

In total, 200 patients were included in the cohort, 100 with ESBL-producing EC/KP and 100 with ESBL-negative EC/KP. Of 100 patients (50%) who developed a subsequent infection, 22 infections were ESBL-producing EC/KP, 43 were other bacteria, and 35 had no or negative cultures. Subsequent infection caused by ESBL-producing EC/KP only occurred when the index culture was also ESBL-producing (22 vs 0). Among those with ESBL-producing index culture, the incidences of subsequent infection caused by ESBL-producing EC/KP versus other bacterial subsequent infection were similar (22 vs 18; P = .428). Factors associated with subsequent infection caused by ESBL-producing EC/KP include history of ESBL-producing index culture, time ≤180 days between index culture and subsequent infection, male sex, and Charlson comorbidity index score >3.

Conclusions

History of ESBL-producing EC/KP culture is associated with subsequent infection caused by ESBL-producing EC/KP, particularly within 180 days after the historical culture. Among patients presenting with infection and a history of ESBL-producing EC/KP, other factors should be considered in making empiric antibiotic decisions, and ESBL-targeted therapy may not always be warranted.

Genotypic characterization of extended-spectrum β-lactamase producing urinary isolates among pregnant women in Ho municipality, Ghana

Objective

The case of antibiotic resistance has become a major global concern and Extended Spectrum β-lactamase (ESBL) producing organisms have so far remained the biggest culprit. The consequences of urinary tract infection (UTI) and antibiotic resistance among pregnant women cannot be underestimated. We investigated UTI and ESBL production among urinary pathogens isolated from pregnant women.

Method

We obtained non-repeat, clean catch midstream urine samples from 1345 pregnant women suspected of having UTI for bacterial identification at the Ho Teaching Hospital Laboratory between June 2013 and March 2015. The isolates were taken through relevant biochemical testing for identification and then subjected to antimicrobial agents for susceptibility testing using the disc diffusion method. We tested for ESBL production by the combined disc method and ESBL positive (+ESBL) phenotype isolates were genotyped for Bla_TEM, Bla_SHV, and Bla_CTX-M using polymerase chain reaction (PCR). Data were analyzed using SPSS v24 and p-values < 0.05 were considered statistically significant.

Results

Of the 1345 urine samples tested, 230 (17.1%, 95% CI: 15.1%-19.1%) yielded significant bacteriuria. The most common bacterium isolated was Staphylococcus aureus (29.6%) followed closely by Escherichia coli (28.7%) both of which were highest during the second trimester of gestation. We isolated 152 gram-negative isolates with 41.4% (63/230) being + ESBL. Of the 63 + ESBL, 45 (71.4%) possessed bla_TEM, 42 (66.7%) had bla_CTX-M and 2 (3.2%) possessed bla_SHV genes; 38 possessed multiple ESBL genes comprising 2 with both SHV and TEM genes and 36 with both CTX-M and TEM genes.

Conclusion

High prevalence of UTI and persistent transmission of ESBLs among pregnant women in the Ho Municipality is worrying and a course for public health concern. We recommend urine culture during pregnancy as a routine laboratory investigation to avoid birth-related complications.

Prediction of ESBL-producing E coli for suspected urinary tract infection

Aim:

The widespread existence of extended-spectrum β-lactamase (ESBL) producing Escherichia coli ( E. coli) has become a critical threat in developed countries. Prediction rule for ESBL producing E. coli is relevant to see patients with suspected urinary tract infection.

Materials and methods:

We collected clinical and laboratory data and constructed multivariate logistic regression models to develop a clinical prediction rule in the derivation cohort with 1185 patients with urine cultures and validated the rule in the validation cohort with 516 patients.

Results:

ESBL-producing E. coli was found in 185 patients (16%) in the derivation cohort. When assigning 14 points for being female (odds ratio (OR): 4.2), six points for CRP >5 mg/dl (OR: 1.87), and four points for a history of urinary tract infection (OR: 1.52), the area under the curve (AUC) had 0.67 (95% confidence interval (CI): 0.63–0.70) in the derivation cohort and 0.64 (95% CI: 0.59–0.69] in the validation cohort.

Conclusions:

The developed prediction rule had moderate accuracy to predict ESBL-producing E. coli in patients with suspected urinary tract infection.

Systematic Review of Plasmid AmpC Type Resistances in Escherichia coli and Klebsiella pneumoniae and Preliminary Proposal of a Simplified Screening Method for ampC

Beta-lactamase (BL) production is a major public health problem. Although not the most frequent AmpC type, AmpC-BL is increasingly isolated, especially plasmid AmpC-BL (pAmpC-BL). The objective of this study was to review information published to date on pAmpC-BL in Escherichia coli and Klebsiella pneumoniae, and on the epidemiology and detection methods used by clinical microbiology laboratories, by performing a systematic review using the MEDLINE PubMed database. The predictive capacity of a screening method to detect AmpC-BL using disks with cloxacillin (CLX) was also evaluated by studying 102 Enterobacteriaceae clinical isolates grown in CHROMID ESBL medium with the addition of cefepime (FEP), cefoxitin (FOX), ertapenem (ETP), CLX, and oxacillin with CLX. The review, which included 149 publications, suggests that certain risk factors (prolonged hospitalization and previous use of cephalosporins) are associated with infections by pAmpC-BL-producing microorganisms. The worldwide prevalence has increased over the past 10 years, with a positivity rate ranging between 0.1 and 40%, although AmpC was only detected when sought in a targeted manner. CMY-2 type has been the most prevalent pAmpC-BL-producing microorganism. The most frequently used phenotypic method has been the double-disk synergy test (using CLX disks or phenyl-boronic acid and cefotaxime [CTX] and ceftazidime) and the disk method combined with these inhibitors. In regard to screening methods, a 1-µg oxacillin disk with CLX showed 88.9% sensitivity, 100% specificity, 100% positive predictive value (PPV), 98.9% negative predictive value (NPV), and 98.9% validity index (VI). This predictive capacity is reduced with the addition of extended-spectrum beta-lactamases, showing 62.5% sensitivity, 100% specificity, 100% PPV, 93.5% NPV, and 94.1% VI. In conclusion, there has been a worldwide increase in the number of isolates with pAmpC-BL, especially in Asia, with CMY-2 being the most frequently detected pAmpC-BL-producing type of microorganism. Reduction in its spread requires routine screening with a combination of phenotypic methods (with AmpC inhibitors) and genotypic methods (multiplex PCR). In conclusion, the proposed screening technique is an easy-to-apply and inexpensive test for the detection of AmpC-producing isolates in the routine screening of multidrug-resistant microorganisms.

Isolation of third generation cephalosporin resistant Enterobacteriaceae from retail meats and detection of extended spectrum beta-lactamase activity

Various methods have been described to isolate third generation cephalosporin (3GC) resistant Enterobacteriaceae from foods, but it is not known how comparable they are between studies. Here, the performance of five enrichment broths and two selective agars are compared for their ability to isolate 3GC resistant Enterobacteriaceae from retail chicken, beef, pork, and veal samples. The results showed equivalence between Enterobacteriaceae enrichment broth (EE), lauryl sulfate broth (LST), and modified typtone soy broth (mTSB). Lower isolation rates were observed when LST and mTSB were supplemented with the 3GC antibiotic cefotaxime. The overall performance of MacConkey agar supplemented with cefotaxime and a proprietary selective agar (ESBL CHROMagar) was equivalent, although differences linked to the microbiota of specific meat commodities were noted. Regardless of the isolation method, further screening was required to confirm the taxonomy and resistance of the presumptive positive strains. Approximately 40% of confirmed 3GC resistant foodborne Enterobacteriaceae strains tested positive for extended spectrum beta-lactamase (ESBL) activity. Strains that were resistant to ceftriaxone and susceptible to cefoxitin were more likely to test positive for ESBL activity, as were strains that possessed either of two ESBL genes (bla_SHV or bla_TEM). Based on our results, we recommend using an antibiotic-free enrichment broth, two selective agars, and an isolate screening strategy to isolate 3GC resistant Enterobacteriaceae from retail meats. Antibiotic susceptibility testing and/or PCR screening for bla_SHV or bla_TEM can then be used to identify ESBL producing strains among the 3GC resistant meat isolates. The adoption of this approach by the research community will enable more effective monitoring of antibiotic resistance rates and trends among foodborne Enterobacteriaceae over time and across jurisdictions.

A practical update on the epidemiology and risk factors for the emergence and mortality of bloodstream infections from real-world data of 3014 hematological malignancy patients receiving chemotherapy

Background: Bloodstream infection (BSI) is a common and serious complication after patients with hematologic malignancies (HM) receiving chemotherapy. This study examined real-world data seeking to characterize HM BSI and identify risk factors for BSI emergence and mortality.

Methods: We retrospectively analyzed the pathogenic epidemiology, antibiotic resistance, and BSI risk factors in a single-center cohort including 3014 consecutive patients with HM receiving chemotherapy between 2013 and 2016. Results of the pathogenic epidemiology were validated via comparison to available reported data.

Results: We found that 725 patients (24.1%) had BSIs. Gram-negative (G-) bacteria represented 64.7% of the 744 isolated pathogenic strains, while Gram-positive (G+) bacteria and fungi accounted for 27.7% and 7.7% of the BSIs, respectively. The most common isolates were Klebsiella pneumoniae (19.2%), and 95.1% of the multidrug-resistant strains (MDR) were extended-spectrum beta-lactamase producing strains. G- bacteria were the main microflora responsible for BSI in our cohort of Chinese HM patients compared to studies in developed countries or in neutropenic children with HM or solid tumors. Multivariate analysis revealed that male sex, age ≥ 45 and < 65 yr, hospital length of stay ≥ 9d, neutropenia ≥ 7d before cultures, ≥ 2 antibiotics, and infections (gastrointestinal, perirectal, or urinary tract) independently predicted BSI emergence. Furthermore, age ≥ 65 yr, neutropenia ≥ 7d before blood cultures, no HM remission, lower white blood cell count, ≥ 3 antibiotics, respiratory infections, and Acinetobacter baumannii and Stenotrophomonas maltophilia BSI were independent predictors of 30-day mortality.

Conclusions: G- bacteria were the predominant microflora during the study period and antibiotic resistance levels of the pathogens detected were high, especially for MDR strains. The mortality of BSI patients was high in this large cohort. Close attention should be paid to the risk factors identified here to facilitate timely and effective clinical management of such patients.

High prevalence and persistence of carbapenem and colistin resistance in livestock farm environments in China

The global dissemination of antibiotic resistance genes (ARGs) and their role as novel contaminants has garnered significant attention. However, the prevalence of ARGs in farm environments is usually underestimated and understudied. Here, colistin resistance gene mcr-1 and extended-spectrum β-lactamase (ESBL) and carbapenemase genes, all of which pose a threat to food safety and public health, were selected to investigate ARG pollution in farm environments. Target gene prevalence ranged from 22.4% to 98.8%, with broiler feedlots showing higher contamination rates than pig and layer feedlots. Moreover, the ARGs were detected in the cooperative broiler feedlot environment from 2016 to 2019, with no significant changes in mcr-1 abundance after the 2017 ban on colistin as a growth promotor. The relative abundance of target genes was also higher in solid manure than in feces and soil. Overall, our results revealed: (1) that broiler farm environments could serve as an important reservoir of mcr-1 and ESBL- and carbapenemase-encoding genes; (2) that fecal treatment processes may affect levels of ARG contamination in the environment; and (3) that residual colistin selects for the persistence of mcr-1 in farm environments. Therefore, further investigation is needed to estimate the impact of the ban on colistin as a growth promoter.

Molecular characterisation of extended-spectrum β-lactamase-producing Escherichia coli and Salmonella isolated from poultry and poultry products in Egypt

Extended-spectrum β-lactamase (ESBL) producing E. coli and salmonellae have spread rapidly worldwide and pose a serious threat to human and animal health. The present study was conduct-ed to determine the prevalence of ESBL-producing E.coli and salmonellae, to perform molecular characterisation of the ESBL-related bla genes, including blaTEM, blaSHV and blaCTX, and the sus-ceptibilities of these bacteria to various antimicrobial agents. From a total of 300 poultry samples, 25 and 20 samples were recognised as Salmonella and E. coli, respectively by microbiological and molecular methods. All E. coli and Salmonella isolates were positive for an ESBL phenotype. Mo-lecular detection for antibiotic resistance gene revealed blaTEM in all isolates of salmonellae and E. coli (100%), while blaSHV was detected in 5 (20%) and 2 (10%) of salmonellae and E. coli isolates, respectively. None of the isolates contained blaCTX gene. Serotyping of Salmonella spp. in chick-ens revealed that S. enteritidis was the major isolates followed by S. Infantis (21.4%), S. Kentucky (14.2%) and S. Typhimurium, S. Kapemba, S. Newport, S. Vejle and S. Magherafelt were detected at 7.1% respectively. S. Infantis was the major isolate detected in chicks (60%), while in ducks S. Typhimurium and S. Blegdam were identified. In ducklings, S. Sinchew, S. Infantis and S. Sekon-di were equally prevalent. Only S. Newmexico was identified in poultry products. E. coli in chick-en were serotyped into O1, O8, O29, O125, O128 and O157. In chicks, O29 and O126 serotypes were detected. In poultry products only O8 was detected. The results indicate that ESBL frequen-cy has reached an alarming level in poultry isolates in Egypt, with TEM enzymes being the pre-dominant β-lactamases detected.

Clinically relevant antibiotic-resistant bacteria in aquatic environments - An optimized culture-based approach

The emergence of antibiotic-resistant clinically relevant facultative pathogenic bacteria in the environment has become one of the most important global health challenges. Antibiotic-resistant bacteria (ARB) have been found in surface waters and wastewater treatment plants. Drinking water guidelines and the EU bathing water directive 2006/7/EC include the surveillance of defined microbiological parameters on species level, while the monitoring of ARB is missing in all existing guidelines. However, standardized methods for the detection of ARB exist for clinical investigations of human materials only. They are based on cultivation on selective agar plates. These methods cannot be used directly for environmental samples, because of the high amount and diversity of bacterial background flora which interferes with the detection of human-relevant ARB. The aim of this study was to introduce a proposal for future normative standard operation procedures, with international relevance, for the culture-based detection of clinically-relevant antibiotic resistant bacteria in aquatic environmental samples like wastewater and surface water: gram-negative bacteria resistant against 3rd generation cephalosporins (ESBL) and against carbapenems (CARBA), gram-positive vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). The final adaptation of standardized cultivation methods included increasing the standard incubation temperature from 36 °C to 42 °C, which effectively inhibits the environmental background flora on agar plates while the desired target species survive. This enables the detection of target species in suitable sample volumes. Putative target colonies which belong to the remaining background flora had to be excluded by morphological and physiological differentiation. Therefore, a time and cost optimized testing scheme with good performance was developed, which allows an effective exclusion of non-target isolates in samples. Depending on the target species and sample type, sensitivity of up to 100% is achieved, and specificity ranges from 91.1% to 99.7%, while the positive predictive value, negative predicted value and accuracy rate are always >90%.

Third-generation cephalosporin resistant Enterobacteriaceae in neonates and young infants: impact and outcome

OBJECTIVE

Third-generation cephalosporins resistant Enterobacteriaceae (3GCR-EB) are a major threat in severely ill neonates hospitalized in Neonatal Intensive Care Units. Still, the particular impact of 3GCR-EB on outcomes in the wide neonatal population is not well-appreciated. We aimed to study the impact of 3GCR-EB on the length of hospital stay and mortality of a general population of neonates and young infants.

STUDY DESIGN

This was a retrospective cohort study of neonates and young infants born in eight Israeli hospitals between 2009 and 2013, with a culture taken within three months after birth that tested positive for Enterobacteriaceae (EB). Data for this study were taken from centralized electronic health records included inpatient, outpatient, socio-demographic, administrative and laboratory information. The main outcomes were length of stay and mortality. The main explanatory variable was an isolation of 3GCR-EB in any bacterial culture taken from a neonate or young infant.

RESULTS

Cultures were taken for 31,921 neonates and young infants; 2647 (8.3%) tested positive for EB and 290 (11%) tested positive for 3GCR-EB. Length of stay for those who tested positive was 2.8 times longer (95%CI: 2.70-2.91, p ˂ .001) than patients who tested positive for 3GC-susceptible EB. 3GCR-EB were also associated with increased mortality (OR: 12.06, 95%CI: 4.92-32.29).

CONCLUSIONS

Neonates with third-generation cephalosporins resistant Enterobacteriaceae had extended hospitalization and increased mortality, which was mostly significant in normal gestational weight newborns.

Review of phenotypic assays for detection of extended-spectrum β-lactamases and carbapenemases: a microbiology laboratory bench guide

Background

Infections caused by gram-negative antibiotic-resistant bacteria continue to increase. Despite recommendations by the Clinical Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) with regards to detection of antibiotic degrading enzymes secreted by these bacteria, the true prevalence of extended-spectrum β-lactamase (ESBL) and carbapenemase producers remains a difficult task to resolve. Describing of previously designed phenotypic detection assays for ESBLs and carbapenemases in a single document avails a summary that allows for multiple testing which increases the sensitivity and specificity of detection.

Methods and aims

This review, therefore, defined and classified ESBLs and carbapenemases, and also briefly described how the several previously designed phenotypic detection assays for the same should be performed.

Conclusion

Extended-spectrum β-lactamase and carbapenemase detection assays, once performed correctly, can precisely discriminate between bacteria producing these enzymes and those with other mechanisms of resistance to β-lactam antibiotics.

Short communication: Selection of extended-spectrum β-lactamase-producing Escherichia coli in dairy calves associated with antibiotic dry cow therapy-A cohort study

Antimicrobial residues in milk have been discussed as a possible selector for Enterobacteriaceae that produce extended-spectrum β-lactamases (ESBL) in dairy herds. Such residues are found in waste milk after antibiotic treatment of mastitis, but antibiotic dry cow therapy might also lead to antibiotic residues in colostrum and in milk during early lactation. While it is known that feeding of waste milk selects ESBL bacteria in calves, this was not investigated for colostrum yet, which is supposed to contain much lower antibiotic concentrations than waste milk. In this observational prospective case study on 2 farms, we hypothesized that blanket dry cow treatment with β-lactams would have more selective (here: increasing) effects on ESBL concentrations than selective (here: individually chosen) antibiotic dry cow therapy. Thus, we compared concentrations of ESBL-producing Enterobacteriaceae in feces of calves (n = 50) at 2 dairy farms with different management of antibiotic dry cow therapy. Considerably higher concentrations of ESBL-producing Escherichia coli were observed in blanket antibiotic dry cow therapy on d 3 of the calf's life (7.6 vs. 5.3 log cfu/g of calf feces). Both farms used narrow-spectrum penicillin combined with aminoglycosides for drying off, and the majority of ESBL isolates (93%) were co-resistant to aminoglycosides. No waste milk was fed to calves and no calf was treated with β-lactam antibiotics or aminoglycosides during the first 3 d of life, thus differences were most likely associated with different frequency of antibiotic dry cow therapy on farms (19 of 25 mother cows on farm A, 9 of 25 on farm B). Even though the presumable selection effect of antibiotics used for drying off decreased within the next 3 wk, this result further emphasizes the need for the reduction and prudent use of antibiotic dry cow therapy on farms.

Bacteria Producing Extended Spectrum β-lactamases (ESBLs) in Hospitalized Patients: Prevalence, Antimicrobial Resistance Pattern and its Main Determinants

Background and Objective:

There is a growing concern regarding the lack of new antibiotics, especially for multidrug- resistant bacteria that produce Extended Spectrum β-Lactamases (ESBLs). The present study aims to assess the preva- lence of bacteria producing ESBLs, their antimicrobial resistance pattern, and its main determinants among hospitalized patients.

Methods:

The study population included 383 consecutive patients with a definitive diagnosis of urinary tract infection (UTI). All eligible subjects for the study had a positive culture for gram-negative microorganisms in urine specimens. ESBL producing isolates were characterized phenotypically for ESBL production using the double disc synergy test.

Results:

In total, 383 specimens were assessed, among which 212 (55.4%) were related to bacteria producing ESBLs (ESBL+). Of those with ESBL + infections, 65.5% were sourced from catheters (as hospital-associated UTIs), and 35.5% were categorized as community-associated UTIs. In the group consisting of bacteria producing ESBLs, the high- est sensitivity was observed with Imipenem (72.2%), while the highest resistance was revealed with ceftriaxone (100%).

Conclusion:

We have shown that our community faces a high prevalence of bacteria producing ESBLs, mostly sourced from the catheterization of hospitalized patients. The highest bacterial sensitivity was observed with Imipenem, nitrofu- rantoin, and amikacin, while the highest resistance was found with ceftriaxone and cotrimoxazole, suggesting the inef- fectiveness of using the two latter antibiotics for eradicating these bacterial infections. On the other hand, a history of urinary catheterization and previous hospitalization were two main determinants of their presence, a finding which em- phasizes the importance of avoiding catheterization and hospitalization of patients with UTIs without proper indications.

Prevalence and characterisation of third-generation cephalosporin-resistant Shigella flexneri isolates from Jiangsu Province, China, 2013-2015

OBJECTIVES

The aim of this study was to assess the prevalence of Shigella flexneri resistance to third-generation cephalosporins (3GCs) and to characterise the underlying resistance mechanisms.

METHODS

A total of 282 S. flexneri strains isolated in 2013-2015 in Jiangsu Province, China, were identified, serotyped and analysed for their susceptibility to 3GCs. The bla_TEM, bla_SHV, bla_OXA-1-like and bla_CTX-M-type extended-spectrum β-lactamase (ESBL) genes were amplified and sequenced by PCR.

RESULTS

Of the 282 S. flexneri strains, 97 (34.4%) were resistant to cefotaxime, from which 68 (24.1%) were also resistant to ceftazidime. ESBL genes were detected in 73/97 isolates (75.3%), of which 66/73 (90.4%) showed resistance to 3GCs. Of the 73 ESBL-positive isolates, 32 (43.8%) were positive for CTX-M-1 group (17 for CTX-M-55, 4 for CTX-M-3, 1 for CTX-M-15, 3 for CTX-M-79 and 7 for CTX-M-123), 31 (42.5%) were positive for CTX-M-9 group (29 for CTX-M-14, 1 for CTX-M-24 and 1 for CTX-M-27), 25 (34.2%) were positive for TEM-types (21 for TEM-1 and 4 for TEM-1b) and 1 (1.4%) was positive for SHV-type (SHV-12); none were positive for CTX-M-2 group, CTX-M-8 group and OXA-type.

CONCLUSION

ESBLs play an important role in Shigella resistance to 3GCs. CTX-M-14 and CTX-M-55 appeared to be the dominant ESBLs in 13 cities of Jiangsu Province. Therefore, it is time to regularly monitor resistance of S. flexneri to 3GCs and to take appropriate measures to manage this problem.

Rapid detection of ESBL, carbapenemases, MRSA and other important resistance phenotypes within 6-8 h by automated disc diffusion antibiotic susceptibility testing

Background

In principle, automated systems allow rapid reading of disc diffusion AST (rAST) within 6-8 h.

Objectives

This study analysed whether rAST can discriminate resistance phenotypes such as ESBL, carbapenemases and MRSA/methicillin-resistant Staphylococcus epidermidis from WT populations. We describe species-drug combinations that may require clinical breakpoint adaptions for early reading due to zone diameter changes during the incubation period.

Methods

In total, 1852 clinical strains [Escherichia coli (n = 475), Klebsiella pneumoniae (n = 375), Enterobacter cloacae (n = 301), Staphylococcus aureus (n = 407) and S. epidermidis (n = 294)] were included in this study comprising WT populations and important resistance phenotypes, e.g. ESBL, carbapenemases and MRSA. We assessed (i) separation of resistance phenotypes and WT populations after 6, 8 and 12 h as compared with the 18 h standard, and (ii) diameter changes of WT populations and associated putative epidemiological cut-offs during the incubation period. Disc diffusion plates were automatically streaked, incubated and imaged using the WASPLabTM system.

Results and conclusions

We demonstrated that important resistance phenotypes could reliably be separated from WT populations at early reading times for the most prevalent bacterial pathogens encountered in the clinical laboratory. Current AST expert rules and algorithms for identification of resistance mechanisms can readily be applied for rAST, e.g. EUCAST recommended rules for detection of ESBL, AmpC, carbapenemases and MRSA/methicillin-resistant S. epidermidis. However, several species-drug combinations may require clinical breakpoint adaptations when using rAST as the diameter, and hence the epidemiological cut-off, changes during the incubation period.

Management of infections caused by extended-spectrum β-lactamase-producing Enterobacteriaceae: current evidence and future prospects

INTRODUCTION

The spread of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae has become a major public health threat worldwide. Area covered: A thorough systematic literature review describing the current evidence and future prospects of therapeutic options for infections caused by ESBL-producing Enterobacteriaceae. Expert commentary: The methods of detecting ESBLs have been evolving. The Clinical and Laboratory Standards Institute and the European Committee on Antimicrobial Susceptibility Testing lowered the MIC breakpoints of cephalosporins against ESBL-producing Enterobacteriaceae in 2010. Phenotypic testing for ESBLs is no longer recommended. Instead, the selection of appropriate antimicrobial agents largely depends on the report of minimum inhibitory concentrations (MICs). To date, therapeutic options for these multidrug-resistant organisms remain limited. The clinical efficacy of piperacillin/tazobactam and cefepime on in vitro-susceptible ESBL-producing Enterobacteriaceae remains a concern. Many studies found an in vitro-in vivo discordance based on current breakpoints. Carbapenems are the most reliable antibiotics for severe infections caused by ESBL-producing Enterobacteriaceae. However, their overuse has led to a serious problem of increasing drug resistance. Recently, ceftolozane/tazobactam and ceftazidime/avibactam have been approved for the treatment of complicated urinary tract infections and complicated intra-abdominal infections. The introduction of these new β-lactam/β-lactamase inhibitor combinations offers new carbapenem-sparing options for the treatment of ESBL infections.

Evaluation of an Accelerated Workflow for Surveillance of ESBL (CTX-M)-Producing Escherichia coli Using Amplicon-Based Next-Generation Sequencing and Automated Analysis

Outbreak management of extended spectrum β-lactamase (ESBL)-producing pathogens requires rapid and accurate diagnosis. However, conventional screening is slow and labor-intensive. The vast majority of the screened samples are negative and detection of non-outbreak-related resistant micro-organisms often complicates outbreak management. In a CTX-M-15-producing Escherichia coli outbreak, 149 fecal samples and rectal eSwabs were collected by a cross-sectional survey in a Dutch nursing home. Samples were processed by routine diagnostic methods. Retrospectively, ESBL-producing bacteria and resistance genes were detected directly from eSwab medium by an accelerated workflow without prior enrichment cultures by an amplicon-based next-generation sequencing (NGS) method, and culture. A total of 27 (18.1%) samples were positive in either test. Sensitivity for CTX-M detection was 96.3% for the phenotypic method and 85.2% for the NGS method, and the specificity was 100% for both methods, as confirmed by micro-array. This resulted in a positive predictive value (PPV) of 100% for both methods, and a negative predictive value (NPV) of 99.2% and 96.8% for the phenotypic method and the NGS method, respectively. Time to result was four days and 14 h for the phenotypic method and the NGS method, respectively. In conclusion, the sensitivity without enrichment shows promising results for further use of amplicon-based NGS for screening during outbreaks.

Extended-spectrum β-lactamase-producing Escherichia coli in wastewaters and refugee camp in Lebanon

AIM

To evaluate the effects of population influx of refugees on the prevalence of extended-spectrum β-lactamase-producing Escherichia coli in wastewater networks in Lebanon.

MATERIALS & METHODS

Pulsed-field gel electrophoresis, multilocus sequence typing and antibiotic resistance genes typing were performed.

RESULTS

53.1% of isolates recovered from Al-Qaa refugee camp were positive for the tested resistant determinants compared with 49.1% from river effluents. All isolates carried aac(6)-1b and/or aac(3)-II; none carried armA, rmtB, ant(4')-Iia, aph(3')-Ia or carbapenemases. CTX-M-15, TEM-1, OXA-1, CMY-2 and SHV-12 were detected. Single and/or double substitutions were detected in GyrA and ParC. Phylogenetic group B2 and ST6470 were the most prevalent. Pulsed-field gel electrophoresis revealed 19 XbaI patterns and 17 pulsotypes.

CONCLUSION

The introduction of novel resistance patterns into the wastewater network requires effective control.

A comparison of blood stream infections with extended spectrum beta-lactamase-producing and non-producing Klebsiella pneumoniae in pediatric patients

Background

Rapid development and global spread of multidrug resistant Klebsiella pneumonia (K. pneumoniae) as a major cause of nosocomial infections is really remarkable. The aim of this study was to explore risk factors for health care associated blood stream infections (BSI) caused by ESBL-producing K. pneumoniae in children and analyze clinical outcomes.

Methods

A retrospective review of patients younger than 18 years-old with blood stream infection caused by K. pneumoniae was performed. Patients with ESBL-producing K. pneumoniae isolates were compared with ESBL-non-producing isolates in terms of risk factors, outcome and mortality.

Results

Among 111 K. pneumoniae isolates 62% (n = 69) were ESBL –producing K. pneumoniae. The median total length of hospitalization and median length of stay in hospital before infection was significantly higher in patients with ESBL-producing isolates than ESBL-non-producing. Use of combined antimicrobial treatment was significantly different between ESBL-producing and ESBL-non-producing groups, 75.4% and 24.6%, respectively (p = 0.001). Previous aminoglycoside use was higher in cases with ESBL –producing isolates (p = 0.001). Logistic regression analysis showed a significant correlation between mortality and use of combined antibiotics (OR 4.22; p = 0.01).

Conclusion

ESBL production in K. pneumoniae isolates has a significant impact on clinical course of BSIs. Total length of hospitalization, length of hospital stay before infection, prior combined antibiotic use and use of aminoglycosides were significant risk factors for development of ESBL-producing K. pneumoniae related BSI.

Shigellosis: Epidemiology in India

Shigellosis is one of the major causes of diarrhoea in India. The accurate estimates of morbidity and mortality due to shigellosis are lacking, though it is endemic in the country and has been reported to cause many outbreaks. The limited information available indicates Shigella to be an important food-borne pathogen in India. S. flexneri is the most common species, S. sonnei and non-agglutinable shigellae seem to be steadily surfacing, while S. dysenteriae has temporarily disappeared from the northern and eastern regions. Antibiotic-resistant strains of different Shigella species and serotypes have emerged all over the world. Especially important is the global emergence of multidrug resistant shigellae, notably the increasing resistance to third generation cephalosporins and fluoroquinolones, and also azithromycin. This calls for a continuous and strong surveillance of antibiotic resistance across the country for periodic updation of the local antibiograms. The prevention of shigellosis is desirable as it will substantially reduce the morbidity associated with diarrhoea in the country. Public health measures like provision of safe water and adequate sanitation are of immense importance to reduce the burden of shigellosis, however, the provision of resources to develop such an infrastructure in India is a complex issue and will take time to resolve. Thus, the scientific thrust should be focused towards development of a safe and affordable multivalent vaccine. This review is focused upon the epidemiology, disease burden and the therapeutic challenges of shigellosis in Indian perspective.

The Activities of Adhesion and Biofilm Formation by Candida tropicalis Clinical Isolates Display Significant Correlation with Its Multilocus Sequence Typing

Adhesion and biofilm formation, which can occur on abiotic and biotic surfaces, are key components in Candida pathogenicity. The aims of this study were to infer about the C. tropicalis clinical isolates ability to adhere and form biofilm on abiotic and biotic surfaces and to correlate that with the multilocus sequence typing and other virulence factors. Adhesion and biofilm formation were measured in 68 C. tropicalis isolates from 3 hospitals in China on abiotic (polystyrene) and biotic (human urinary bladder epithelial cell) surfaces by crystal violet assay and 2,3-bis (2-methoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide reduction assay. In our study, almost all C. tropicalis isolates could adhere and produce biofilm on abiotic and biotic surfaces in a strain-dependent manner. The isolates from blood showed relatively lower adhesion and biofilm capacity on polystyrene surface, but had strong secreted aspartyl proteinase activity. Moreover, significant differences were found among MLST groups for adhesion and biofilm capacity. C. tropicalis in multilocus sequence typing group5 and group6 showed high adhesion and biofilm, while isolates in group1 exhibited low adhesion and biofilm formation. Overall, it is important to note that C. tropicalis isolates adhere to and produce biofilm on abiotic and biotic surfaces with strain specificity. These data will play an important role in subsequent research on the pathogenesis of C. tropicalis.

Strain-specific transmission in an outbreak of ESBL-producing Enterobacteriaceae in the hemato-oncology care unit: a cohort study

Background

Extended-spectrum β-lactamase (ESBL)-producing bacteria are resistant to several types of antibiotics excluding carbapenems. A transmissibility of ESBL-producing Enterobacteriaceae would be depending on each bacterial property, however, that has not been elucidated in clinical setting. In this study, we attempted to identify the source of an outbreak of ESBL-producing bacteria in a medical oncology and immunology care unit.

Methods

An ESBL-producing Enterobacteriaceae (ESBL-E) outbreak observed between July 2012 and August 2012 in Kagawa University Hospital was surveyed using various molecular microbiology techniques. We used Pulsed-field gel electrophoresis (PFGE), PCR-based ESBL gene typing, and direct sequence of ESBL gene as molecular microbiology typing method to distinguish each strain.

Results

The typical prevalence of ESBL-E isolation in the unit was 7.0 per month (1.7 per week). The prevalence of ESBL-E isolation during the target research period was 20.0 per month (5.0 per week). In total, 19 isolates (11 K. pneumoniae and 8 E. coli) were obtained from clinical samples, including four control strains (two each of both bacteria), that were physically different from those obtained from other inpatient units in our hospital. Pulsed-field gel electrophoresis (PFGE) for K. pneumoniae (digested by XbaI) produced similar patterns excluding one control strain. PCR classification of the ESBL gene for K. pneumoniae revealed that all strains other than the control strain carried SHV and CTX-M-9. This result was reconfirmed by direct DNA sequencing. Although the outbreak of K. pneumoniae was considered to be “clonal,” PFGE and PCR classification of the ESBL genes for E. coli uncovered at least six different “non-clonal” strains possessing individual ESBL gene patterns. According to the result of an antibiogram, the pattern of antimicrobial susceptibility was more variable for K. pneumoniae than for E. coli.

Conclusions

Typing by PFGE and ESBL gene PCR analysis is practical for discriminating various organisms. In our cohort, two outbreaks were concomitantly spread with different transmission strategies, namely clonal and non-clonal, in the same unit. This might represent clinical evidence that transmissibility differs according to the type of strain. We speculated that patient-to-patient transmission of ESBL-E occurred according to the properties of each individual strain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-2144-4) contains supplementary material, which is available to authorized users.

Improved Accuracy of Cefepime Susceptibility Testing for Extended-Spectrum-Beta-Lactamase-Producing Enterobacteriaceae with an On-Demand Digital Dispensing Method

Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae generally cannot be treated with penicillins and cephalosporins. However, some later-generation cephalosporins, including cefepime, are poorly hydrolyzed by specific ESBL enzymes, and certain strains demonstrate in vitro susceptibility to these agents, potentially affording additional treatment opportunities. Moreover, the ability to adjust both the dose and dosing interval of beta-lactam agents allows the treatment of strains with elevated MICs that were formerly classified in the intermediate range. The ability to treat strains with elevated cefepime MICs is codified in new susceptible dose-dependent (SDD) breakpoints promulgated by the Clinical and Laboratory Standards Institute. In the interest of validating and implementing new cefepime SDD criteria, we evaluated the performances of Vitek 2, disk diffusion, and a MicroScan panel compared to that of reference broth microdilution (BMD) during the testing of 64 strains enriched for presumptive ESBL phenotype (based on nonsusceptibility to ceftriaxone). Surprisingly, categorical agreement with BMD was only 47.6%, 57.1%, and 44.6% for the three methods, respectively. Given these findings, we tested the performance of the HP D300 inkjet-assisted broth microdilution digital dispensing method (DDM), which was previously described by our group as an at-will testing alternative. In contrast to commercial methods, DDM results correlated well with the reference method, with 86% categorical agreement, 91.1% evaluable essential agreement, and no major or very major errors. The reproducibility and accuracy of MIC determinations were statistically equivalent to BMD. Our results provide support for the use of the DDM as a BMD equivalent methodology that will enable hospital-based clinical laboratories to support cefepime MIC-based dosing strategies.

[Evaluation of antibiotic treatments for urinary tract infections in the elderly, especially regarding the effect on extended spectrum β-lactamase producing (ESBL-) Escherichia coli: A comparison between meropenem and alternatives]

BACKGROUND

An increasing incidence of extended-spectrum β-lactamase (ESBL-) producing Escherihia Coli poses a difficult problem for clinicians to establish an optimal strategy for the effective antibiotic treatment of urinary tract infections (UTI).

METHODS

(1) Fosfomycin/minocycline (FOM/MINO) or rifampicin/sulfamethoxazole-trimethoprim (RFP/ST) combinations and (2) levofloxacin (LVFX) alone were used as an internal medication, and (3) cefoperazone/sulbactam (CPZ/SBT) and (4) meropenem (MEPM) were administered through intravenous injection. The selection of antibiotics was done empirically, according to the history and severity of illness and urinary findings, and the presence of comobidities. The efficacy of the treatment was determined by the absence of any pathogenic bacteria from a urinary culture after treatment.

RESULTS

ESBL-producing and LVFX resistant non-ESBL producing E. coli were detected by an initial urinary culture in 33 and 10%, respectively, of the specimens before treatment. All the ESBL-producing E. Coli colonies were resistant against LVFX. The efficacy of the treatment was 9/11 (82%) in the FOM/MINO-RFP/ST group, 9/14 (64%) in the LVFX group, 9/16 (56%) in the CPZ/SBT group, and 19/27 (70%) in the MEPM group. In the FOM/MINO・RFP/ST group, ESBL-producing E. Coli were detected in the urine before treatment in 5 out of 16 patients and those E. coli disappeared after treatment in all 5 patients. In the LVFX group, the drug was changed to MEPM in 6 out of 15 patients soon after the presence of ESBL-producing/LVFX resistant E. Coli was identified by a urinary culture. In the CPZ/SBT group, ESBL-producing and/or LVFX-resistant E. coli disappeared in 4 out of 6 cases, while they were newly found in post-treatment urine cultures in 2 patients. In the MEPM group, 15 out of 28 patients initially had ESBL-producing/LVFX resistant E. Coli and those drug-resistant E. Coli disappeared from their urine after treatment in all patients. The drug susceptibility test of the urinary culture from all the patients with UTI showed CPZ/SBT-resistant colonies to be found in 19 out of 32 specimens, while AMPC/CVA-resistant ones were found in 9 out of 32 of ESBL-producing E. Coli.

CONCLUSIONS

Our present study demonstrates that FOM/MINO or ST combinations were effective in the treatment of ESBL-producing E. Coli in mild cases of UTI and MEPM in severe cases. When using β-lactam/β-lactamase inhibitor combinations, the effect should be ascertained by examining post-treatment urinary specimens, because of the presence of ESBL-producing E. Coli strains which are resistant to those antibiotics.

Colonisation with extended-spectrum beta-lactamase (ESBL) not detected in a prevalence study

BACKGROUND

The Mid-West of Ireland has higher than average national rates of invasive extended-spectrum beta-lactamase (ESBL) bloodstream infections and carbapenemase-producing Enterobacteriaceae (CPE), with increasing numbers of ESBL isolates detected in community-dwelling patients.

AIMS

To conduct a point prevalence study in a convenience sample of the Mid-West population with the aim of determining the extent of ESBL colonisation.

METHODS

Utilising anonymised community stool samples that had completed routine analysis, we conducted a point prevalence study over a 4-week period on all samples that met defined inclusion and exclusion criteria. Limited epidemiological data was recorded: (1) age of patient, (2) gender, and (3) sender location. From these stool specimens, rectal swabs were inoculated (eSwab™ 480CE, Copan, Italy), which were subsequently cultured on selective chromogenic agar (Colorex™ ESBL). Culture plates were incubated aerobically at 37 °C for 24 h.

RESULTS

Of 195 samples processed, 58 % (n = 112) were from females. The median patient age was 62.4 years (range 20-94 years). 186 samples (95 %) originated from general practitioner clinics. During the study period, only nine eligible stool samples were received from LTCF (6 public). From 195 Colorex™ ESBL chromogenic agar plates cultured, no ESBL-producing organisms were detected.

CONCLUSIONS

This community point prevalence study did not identify ESBL colonisation despite high numbers of patients with invasive ESBL bloodstream infections presenting for admission in our institution. We believe this may be because of our small sample size. Data regarding antimicrobial exposure and other risk factors for ESBL colonisation were also not available. We remain vigilant for ESBL-producing organisms.

Beta-lactamases in Enterobacteriaceae infections in children

Multi-drug resistance in Gram negative bacteria, particularly in Enterobacteriaceae, is a major clinical and public health challenge. The main mechanism of resistance in Enterobacteriaceae is linked to the production of beta-lactamase hydrolysing enzymes such as extended spectrum beta-lactamases (ESBL), AmpC beta-lactamases and carbapenemases (Carbapenemase Producing Enterobacteriaceae (CPE)). ESBL and CPE resistance genes are located on plasmids, which can be transmitted between Enterobacteriaceae, facilitating their spread in hospitals and communities. These plasmids usually harbour multiple additional co-resistance genes, including to trimethoprim-sulfamethoxazole, aminoglycosides, and fluoroquinolones, making these infections challenging to treat. Asymptomatic carriage in healthy children as well as community acquired infections are increasingly reported, particularly with ESBL. Therapeutic options are limited and previously little used antimicrobials such as fosfomycin and colistin have been re-introduced in clinical practice. Paediatric experience with these agents is limited hence there is a need to further examine their clinical efficacy, dosage and toxicity in children. Antimicrobial stewardship along with strict infection prevention and control practices need to be adopted widely in order to preserve currently available antimicrobials. The future development of novel agents effective against beta-lactamases producers and their applicability in children is urgently needed to address the challenge of multi-resistant Gram negative infections.

Enhancing Phenotypic Detection of ESBL in AmpC co-producers by using Cefepime and Tazobactam

INTRODUCTION

Routine phenotypic methods employing clavulanate and third generation cephalosporins to detect ESBL are not promising for isolates that co-produce an inhibitor-resistant beta lactamase like AmpC.

AIM

Enhancing phenotypic detection of ESBL in AmpC co-producers by using cefepime and tazobactam.

MATERIALS AND METHODS

A total of 245 isolates of Escherichia coli (123), Klebsiella spp. (87), Proteus spp.(20), Enterobacter spp. (9) and Citrobacter spp.(6) obtained over a period of 2 years from January 2013 to December 2014 from urine samples of hospitalized patients were studied. The isolates were simultaneously screened for ESBL and AmpC production. AmpC production was confirmed by modified three -dimensional test (MTDT). ESBL production was confirmed by original double disc synergy test, phenotypic disc confirmatory test (PDCT) and modified double disc synergy test (MDDST) and the results compared.

RESULTS

AmpC production was confirmed in 113 (46.1%) isolates by modified three dimensional test out of 143 screened positive for AmpC. Of the 192 isolates screened positive for ESBL, ESBL production was confirmed in 162 (66.1%). DDST detected ESBLs in only134 (54.7%) while additional 28 (11.4%) ESBL positive isolates were detected by MDDST. PDCT detected total 145(59.2%) ESBL positive isolates, with cefotaxime and cefotaxime + clavulanate detecting 139 (56.7%) and ceftazidime and ceftazidime + clavulanate detecting additional 6 isolates. All the 28 (11.4%) isolates which were additionally detected ESBL producers by MDDST showed positive three dimensional test i.e. AmpC co producers. DDST detected ESBL in none of AmpC positive isolates while PDCT detected ESBL in 11 isolates showing AmpC co-production. In MDDST cefepime was the best cephalosporin in detecting ESBL in presence of AmpC production. It showed synergism with amoxicillin-clavulanate in 11(39.3%) isolates and in 24(85.7%) isolates with piperacillin-tazobactam. Third generation cephalosporins -cefotaxime, ceftazidime and cefpodoxime were not able to detect ESBL in AmpC-co producers.

CONCLUSION

Modification of double disc synergy tests that combine piperacillin-tazobactum with cefepime enhances the possibility of ESBL detection.

A potential camel reservoir for extended-spectrum β-lactamase-producing Escherichia coli causing human infection in Saudi Arabia

The prevalence of antimicrobial resistance is continuing to increase. Consequently, efficient approaches to identify sources of resistance are required. This study aimed to compare Escherichia coli isolates from the intestinal tract of camels with isolates from human urinary tract infections (UTIs) in Al Ahsa Province, Kingdom of Saudi Arabia (KSA), for antimicrobial resistance and identification of extended-spectrum β-lactamases (ESBLs). A microbiological study was conducted on 100 samples of cecal contents from camels and 100 urine samples from female UTI patients, to isolate and confirm E. coli using the VITEK 2 Automated System. Sensitivity patterns and identification of ESBLs were analyzed using the antimicrobial susceptibility test. Molecular techniques were used to detect E. coli drug-resistant clones. The presence rate of E. coli in camels was 26.0 % (n = 26/100), and in human samples, the rate of E. coli was 33.0 % (n = 33/100). ESBLs were reported for the first time in KSA, in 26.9 % (n = 5/26) of camel samples and 36.4 % (n = 8/33) of human samples. The multi-drug resistance (MDR) index was 0.13 and 0.17, for camels and humans, respectively. Escherichia coli drug-resistant O25b:H4-sequence type 131(ST131) clone was detected in two camel and two human isolates. This study demonstrates a high presence rate of ESBL-producing E. coli (ESBL-EC) in camels for the first time in KSA. Confirmation of MDR strains and E. coli ST131 clone in human and camel isolates suggests that camels could be a potential reservoir for resistant E. coli strains contributing to the increase in antimicrobial resistance in KSA.

A qPCR and multiplex pyrosequencing assay combined with automated data processing for rapid and unambiguous detection of ESBL-producers Enterobacteriaceae

Rapid and specific detection of extended-spectrum β-lactamase-producing (ESBL) bacteria is crucial both for timely antibiotic therapy when treating infected patients as well as for appropriate infection control measures aimed at curbing the spread of ESBL-producing isolates. Whereas a variety of phenotypic methods are currently available for ESBL detection, they remain time consuming and sometimes difficult to interpret while being also affected by a lack of sensitivity and specificity. Considering the longer turnaround time (TAT) of susceptibility testing and culture results, DNA-based ESBL identification would be a valuable surrogate for phenotypic-based methods. Putative ESBL-positive Enterobacteriaceae isolates (n = 330) from clinical specimen were prospectively collected in Bulgaria, Romania and Democratic Republic of Congo and tested in this study. All isolates were assessed for ESBL-production by the E-test method and those giving undetermined ESBL status were re-tested using the combination disk test. A genotypic assay successively combining qPCR detection of blaCTX-M, blaTEM and blaSHV genes with a multiplex pyrosequencing of blaTEM and blaSHV genes was developed in order to detect the most common ESBL-associated TEM and SHV single nucleotides polymorphisms, irrespective of their plasmid and/or chromosomal location. This assay was applied on all Enterobacteriaceae isolates (n = 330). Phenotypic and genotypic results matched in 324/330 (98.2%). Accordingly, real-time PCR combined with multiplex pyrosequencing appears to be a reliable and easy-to-perform assay with high-throughput identification and fast TAT (~5 h).

Detection of expanded-spectrum β-lactamases in Gram-negative bacteria in the 21st century

Emerging β-lactamase-producing-bacteria (ESBL, AmpC and carbapenemases) have become a serious problem in our community due to their startling spread worldwide and their ability to cause infections which are difficult to treat. Diagnosis of these β-lactamases is of clinical and epidemiological interest. Over the past 10 years, several methods have been developed aiming to rapidly detect these emerging enzymes, thus preventing their rapid spread. In this review, we describe the range of screening and detection methods (phenotypic, molecular and other) for detecting these β-lactamases but also whole genome sequencing as a tool for detecting the genes encoding these enzymes.

Changing profile and increasing antimicrobial resistance of uropathogenic bacteria in Madagascar

OBJECTIVES

We wanted to update the distribution of community-acquired uropathogens and to estimate their susceptibility profile to newly available antibiotics in Antananarivo (Madagascar).

MATERIALS AND METHODS

We conducted a 3-year preliminary study (2011-2013) on bacteria isolated from the urine of patients at the Laboratory of Training and Research in Medical Biology (Antananarivo).

RESULTS

Three hundred and fifty-seven pathogens were isolated: 234 (65.55%) Gram-negative bacilli and 123 (34.45%) Gram-positive cocci. The most commonly isolated bacteria were Escherichia coli (89 strains) followed by Staphylococcus aureus (48 strains). Thirty-three percent of Gram-negative bacilli were resistant to 3 CG. Forty percent of Klebsiella pneumoniae strains were significantly resistant to imipenem (P = 0.01).

CONCLUSIONS

The increased resistance to newly available antibiotics and the increased rate of Gram-positive cocci strains require a drastic surveillance of antibiotic resistance to ensure appropriate empirical treatment.

The Challenge of Antimicrobial Resistance in Managing Intra-Abdominal Infections

BACKGROUND

In recent years, there has been a worldwide increase in infections caused by microorganisms resistant to multiple antimicrobial agents.

METHODS

In the past few decades, an increased prevalence of infections caused by antibiotic-resistant pathogens, including Enterococcus spp., carbapenem-resistant Pseudomonas aeruginosa and Acinetobacter baumannii, extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella spp., carbapenemase-producing Klebsiella pneumoniae, and resistant Candida spp., also has been observed among intra-abdominal infections (IAIs).

RESULTS

The increasing prevalence of multi-drug resistance is responsible for a substantial increase in morbidity and mortality rates associated with IAIs.

CONCLUSIONS

It is necessary for every surgeon treating IAIs to understand the underlying epidemiology and clinical consequences of antimicrobial resistance. Emergence of drug resistance, combined with the lack of new agents in the drug development pipeline, indicates that judicious antimicrobial management will be necessary to preserve the utility of the drugs available currently.

Antimicrobial resistance: impact on clinical and economic outcomes and the need for new antimicrobials

INTRODUCTION

Antimicrobial resistance is a well-recognized global threat; thus, the development of strong infection control policies coupled with antimicrobial stewardship strategies and new therapies is required to reverse this process. In its 2013 report on antimicrobial resistance, the Centers for Disease Control and Prevention focused on this problem while presenting estimated annual rates of infections with antimicrobial-resistant organisms and their related mortality rates. Whereas some resistant pathogens were considered less threatening, others such as carbapenem-resistant Enterobacteriaceae were associated with higher mortality rates owing to limited treatment options.

AREAS COVERED

An overview of the most common antimicrobial-resistant pathogens, focusing on risk factors for acquisition, clinical and economic outcomes, as well as current treatment options. Strategies to optimize antimicrobial therapy with currently available agents, in addition to newly developed antimicrobials are also discussed.

EXPERT OPINION

The emergence of pathogens with a variety of resistance mechanisms has intensified the challenges associated with infection control and treatment strategies. Therefore, prudent use of currently available antimicrobial agents, as well as implementing measures to limit spread of resistance is paramount. Although several new antimicrobials have been recently approved or are in the pipeline showing promise in the battle against resistance, the appropriate use of these agents is required as the true benefits of these treatments are to be recognized in the clinical care setting.

Mechanisms of β-lactam antimicrobial resistance and epidemiology of major community- and healthcare-associated multidrug-resistant bacteria

Alexander Fleming's discovery of penicillin heralded an age of antibiotic development and healthcare advances that are premised on the ability to prevent and treat bacterial infections both safely and effectively. The resultant evolution of antimicrobial resistant mechanisms and spread of bacteria bearing these genetic determinants of resistance are acknowledged to be one of the major public health challenges globally, and threatens to unravel the gains of the past decades. We describe the major mechanisms of resistance to β-lactam antibiotics - the most widely used and effective antibiotics currently - in both Gram-positive and Gram-negative bacteria, and also briefly detail the existing and emergent pharmacological strategies to overcome such resistance. The global epidemiology of the four major types of bacteria that are responsible for the bulk of antimicrobial-resistant infections in the healthcare setting - methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, Enterobactericeae, and Acinetobacter baumannii - are also briefly described.

Beyond Susceptible and Resistant, Part II: Treatment of Infections Due to Gram-Negative Organisms Producing Extended-Spectrum β-Lactamases

The production of β-lactamase is the most common mechanism of resistance to β-lactam antibiotics among gram-negative bacteria. Extended-spectrum β-lactamases (ESBLs) are capable of hydrolyzing most penicillins, extended-spectrum cephalosporins, and aztreonam, but their activity is suppressed in the presence of a β-lactamase inhibitor. Serious infections with ESBL-producing isolates are associated with high rates of mortality, making early detection and adequate medical management essential to ensure optimal patient outcomes. Much controversy has centered on the recommendations for testing and reporting of antibiotic susceptibility of potential ESBL-producing organisms. The latest version of the Clinical Laboratory Standards Institute (CLSI) susceptibility reporting guidelines, published in 2010, no longer advocates for phenotypic testing of ESBL-producing isolates. From newer studies demonstrating a correlation between organism minimum inhibitory concentration (MIC) and clinical outcome, along with pharmacokinetic/pharmacodynamic (PK/PD) modeling demonstrating the importance of the MIC to achieving therapeutic targets, the CLSI has assigned lower susceptibility breakpoints for aztreonam and most cephalosporins. The new guidelines recommend using the lower MIC breakpoints to direct antibiotic selection. This article reviews the microbiology and epidemiology of ESBLs, the recent change in CLSI susceptibility reporting guidelines for ESBLs, and the clinical and PK/PD data supporting the relationship between in vitro susceptibility and clinical outcome. Finally, considerations for antimicrobial selection when treating patients with infections caused by ESBL-producing organisms from various sources are discussed.

Klebsiella pneumoniae bloodstream infection: epidemiology and impact of inappropriate empirical therapy

Multidrug resistance associated with extended-spectrum beta-lactamase (ESBL) and Klebsiella pneumoniae carbapenemase (KPC) among K. pneumoniae is endemic in southern Europe. We retrospectively analyzed the impact of resistance on the appropriateness of empirical therapy and treatment outcomes of K. pneumoniae bloodstream infections (BSIs) during a 2-year period at a 1420-bed tertiary-care teaching hospital in northern Italy. We identified 217 unique patient BSIs, including 92 (42%) KPC-positive, 49 (23%) ESBL-positive, and 1 (0.5%) metallo-beta-lactamase-positive isolates. Adequate empirical therapy was administered in 74% of infections caused by non-ESBL non-KPC strains, versus 33% of ESBL and 23% of KPC cases (p < 0.0001). To clarify the impact of resistance on BSI treatment outcomes, we compared several different models comprised of non-antibiotic treatment-related factors predictive of patients' 30-day survival status. Acute Physiology and Chronic Health Evaluation (APACHE) II score determined at the time of positive blood culture was superior to other investigated models, correctly predicting survival status in 83% of the study cohort. In multivariate analysis accounting for APACHE II, receipt of inadequate empirical therapy was associated with nearly a twofold higher rate of death (adjusted hazard ratio 1.9, 95% confidence interval 1.1-3.4; p = 0.02). Multidrug-resistant K. pneumoniae accounted for two-thirds of all K. pneumoniae BSIs, high rates of inappropriate empirical therapy, and twofold higher rates of patient death irrespective of underlying illness.

Evaluation of the ability of four ESBL-screening media to detect ESBL-producing Salmonella and Shigella

BACKGROUND

The aim of this study was to compare the ability of four commercially available media for screening extended-spectrum beta-lactamase (ESBL) to detect and identify ESBL-producing Salmonella and Shigella in fecal samples. A total of 71 Salmonella- and 21 Shigella-isolates producing ESBL(A) and/or AmpC, were received at Norwegian Institute of Public Health between 2005 and 2012. The 92 isolates were mixed with fecal specimens and tested on four ESBL screening media; ChromID ESBL (BioMèrieux), Brilliance ESBL (Oxoid), BLSE agar (AES Chemunex) and CHROMagar ESBL (CHROMagar). The BLSE agar is a biplate consisting of two different agars. Brilliance and CHROMagar are supposed to suppress growth of AmpC-producing bacteria while ChromID and BLSE agar are intended to detect both ESBL(A) and AmpC.

RESULTS

The total sensitivity (ESBL(A)+AmpC) with 95% confidence intervals after 24 hours of incubation were as follows: ChromID: 95% (90.4-99.6), Brilliance: 93% (87.6-98.4), BLSE agar (Drigalski): 99% (96.9-100), BLSE agar (MacConkey): 99% (96.9-100) and CHROMagar: 85% (77.5-92.5). The BLSE agar identified Salmonella and Shigella isolates as lactose-negative. The other agars based on chromogenic technology displayed Salmonella and Shigella flexneri isolates with colorless colonies (as expected). Shigella sonnei produced pink colonies, similar to the morphology described for E. coli.

CONCLUSION

All four agar media were reliable in screening fecal samples for ESBL(A)-producing Salmonella and Shigella. However, only ChromID and BLSE agar gave reliable detection of AmpC-producing isolates. Identification of different bacterial species based on colony colour alone was not accurate for any of the four agars.

Epidemiology of infections due to extended-spectrum Beta-lactamase-producing bacteria in a pediatric intensive care unit

OBJECTIVES

To determine the proportion of infections caused by extended-spectrum ß-lactamase (ESBL)-producing Klebsiella or Escherichia coli Gram-negative organisms in the pediatric intensive care unit (PICU), and to identify risk factors for these infections.

METHODS

A retrospective, single-center chart review of patients admitted to a PICU in a 5-year period with infections caused by Klebsiella species or E coli was completed. Data collected include demographics, length of stay, outcome, and relevant risk factors previously defined in the literature.

RESULTS

A total of 110 isolates were cultured from 94 patients. A total of 53% of the isolates were E coli, and the remainder were Klebsiella subspecies. Of the 110 isolates, 13 isolates (11.8%) in 7 patients were ESBL positive. The ESBL-producing isolates were equally distributed amongE coli and Klebsiella and were primarily cultured from tracheal aspirates. Most of the ESBL-positive isolates (9 of 13; 69%) were cultured from patients who received ceftazidime and/or cefotaxime in the preceding 30 days. Patients infected with E coli had higher PRISM 1 scores and were more likely to have a Foley catheter, whereas infections with Klebsiella were more common in mechanically ventilated males. Although not statistically significant, 80% of patients who were infected with non-ESBL-producing organisms survived to hospital discharge versus 57% of those infected with ESBL-producing E coli and Klebsiella.

CONCLUSIONS

Almost 12% of E coli and Klebsiella isolates in this patient population tested positive for ESBL production. ESBL production was equally distributed between E coli and Klebsiella species. These organisms were cultured from 7% of the study patients. As reported in previous studies, patients infected with ESBL-producing organisms most often had received prior cephalosporins and had a longer length of stay in the PICU.

Risk factors for acquisition of extended spectrum beta lactamase producing Escherichia coli and Klebsiella pneumoniae in North-Indian hospitals

Multidrug resistance and production of extended spectrum β-lactamases (ESBLs) by enteric gram negative rods in hospitals and community continue to be a matter of scientific concern. This retrospective study was executed to assess the prevalence of ESBL-producing Escherichia coli and Klebsiella pneumoniae at two North Indian hospitals and to determine the risk factors associated with the acquisition of these organisms. A total of 346 bacterial isolates were obtained. Of these, 48.27% (n = 167) were confirmed to be ESBL producers while 51.73% (n = 179) were non ESBL-producers. Among the ESBL producers, 55.69% (n = 93) were E. coli and 44.31% (n = 74) were K. pneumoniae. ESBL producing isolates showed co-resistance to multitude of antibiotics tested. Length of hospital stay (>3 days) and previous exposure to antibiotics were found as significant risk factors (p = 0.01 and 0.02) associated with the acquisition of ESBL-producing E. coli and K. pneumoniae isolates. Imipenem and meropenem can be suggested as drugs of choice in our study.

Phenotypic and genotypic evaluation of beta-lactamases (ESBL and KPC) among enterobacteria isolated from community-acquired monomicrobial urinary tract infections

Beta-lactamases enzymes such as extended-spectrum beta-lactamases (ESBL) and carbapenemase type beta-lactamases (KPC) confer resistance to beta-lactam drugs among Gram-negative rods, mainly Enterobacteriaceae, as those frequently related to urinary tract infections (UTI). The aim of this study was to evaluate ESBL and KPC among enterobacteria isolated from monomicrobial UTI and to establish correlations between the presence of genetic markers and the phenotypic resistance to beta-lactam antibiotics. Out of 12 304 urine samples collected during 2009, 93 enterobacteria showing an ESBL phenotype were recovered. Imipenem was used for KPC screening and modified disk approximation assay was used for detection of ESBL phenotype. Polymerase chain reaction was used for screening of bla(SHV), bla(TEM), bla(CTX-M), and bla(KPC). Considering the isolated bacteria showing ESBL phenotype 56% of the isolates were positive for two genes. The bla(TEM) was the most frequent (87·1%). Neither KPC phenotype nor bla(KPC)-harboring bacteria were observed. Monitoring the antimicrobial resistance is extremely important to sustain empirical therapy of community-acquired urinary tract infections (Co-UTI).

Fungal invasion of epithelial cells

Interaction between host cells and invasive Candida plays a large role in the pathogenicity of Candida species. Fungal-induced endocytosis and active penetration are the two distinct, yet complementary invasion mechanisms of invasive candidiasis. Induced endocytosis is a microorganism-triggered, epithelial-driven, clathrin-mediated and actin-dependent process. During the fundamental pathological process of induced endocytosis, invasins (Als3 and Ssa1), which mediate the binding of host epithelial surface proteins, are expressed by Candida species on the hyphal surface. Sequentially, the interaction between invasins and host epithelial surface proteins stimulates the recruitment of clathrin, dynamin and cortactin to the sites where Candida enters epithelial cells, which in turn induce the actin cytoskeleton reorganization. Actin cytoskeleton provides the force required for fungal internalization. Parallely, active penetration of Candida can directly pass through epithelial cells possibly due to progressive elongation of hyphae and physical forces. Several molecules, such as secreted hydrolases and Als3, can affect the protective barrier of the epithelium and make Candida actively penetrate into epithelial cells through intercellular gaps of epithelial layers.

Extended-spectrum β-lactamase-producing Klebsiella pneumoniae in the neonatal intensive care unit: does vancomycin play a role?

BACKGROUND

Extended-spectrum β-lactamase (ESBL)-producing Klebsiella species cause worldwide problems in neonatal intensive care units (NICUs). This study aimed to determine possible risk factors for infection or colonization with ESBL-producing Klebsiella pneumoniae (ESBLKp) during an outbreak in the NICU.

METHODS

A retrospective cohort study was conducted among neonates admitted to the NICU of a teaching hospital in Riyadh, Saudi Arabia, during an outbreak of ESBLKp from April to July 2008. The incidence density ratio was calculated to determine possible predictors of ESBLKp colonization or infection.

RESULTS

During 2,265 person-days of follow-up of 118 neonates, 4 became infected, and 8 were colonized with ESBLKp. Univariate analyzes revealed that, among 14 neonates who were treated with vancomycin, 9 (64.3%) developed infection or colonization with ESBLKp, whereas, among 104 neonates who were not treated with vancomycin, 3 (2.9%) were affected, with an incidence density ratio of 4.22 (95% confidence interval: 1.47-5.15). Parenteral feeding and mechanical ventilation were found to be marginally significant risk factors.

CONCLUSION

Treatment with vancomycin appears to be a risk factor for infection or colonization with ESBLKp in the NICU setting.

Evaluation of 3 different agar media for rapid detection of extended-spectrum β-lactamase-producing Enterobacteriaceae from surveillance samples

Rapid detection of extended-spectrum β-lactamase (ESBL)-producing Gram-negative bacilli in surveillance samples of high-risk patients allows early optimization of antimicrobial therapy and timely introduction of infection control procedures. This study evaluated the BLSE (AES Chemunex), chromID ESBL (bioMérieux), and Brilliance ESBL agar (Oxoid) for rapid detection of ESBL-producing Enterobacteriaceae from surveillance samples. A total of 139 perineal and nose samples were processed. Isolated bacterial strains were identified by mass spectrometry. ESBL confirmation was performed by phenotypical and molecular tests. Overall, 16 ESBL-producing Enterobacteriaceae were recovered. The sensitivities after 24 h of incubation were comparable (BLSE, 87.5%; Brilliance ESBL, 87.5%; and chromID, 81.3%). The specificity of chromogenic media (80.7-82.1%) was significantly higher compared to BLSE (60.8%). All 3 media are reliable to screen for ESBL-producing Enterobacteriaceae from surveillance samples. Yet, the main advantages of chromogenic media over BLSE reside in their chromogenic character and higher specificity, reducing the total number of isolates that require further identification and ESBL confirmation testing.