Imipenem Resistance Research Articles

Clinical characteristics and prognostic risk factors analysis of carbapenem-resistant organism in the department of hematology

目的了解血液科碳青霉烯耐药革兰阴性菌（CRO）感染的分布及耐药情况，分析影响CRO感染患者预后的危险因素，为临床CRO感染患者的治疗和预后判断提供依据。方法回顾性分析2018年1月至2020年6月血液科确诊的CRO感染患者181例，收集患者的临床和实验室检查等资料，分析影响患者30 d死亡的危险因素。在碳青霉烯类耐药肠杆菌科细菌（CRE）亚组中进一步评价CRE主动筛查的临床意义。结果分离出的181株CRO中CRE占47.2％，铜绿假单胞菌占37.0％，肺炎克雷伯菌占32.6％，对碳青霉烯类药物高度耐药，对亚胺培南耐药最低抑菌浓度（MIC）≥16 µg/ml的占76.8％（139/181）。菌株标本来源主要是血样和痰液。CRO和CRE感染患者30 d的全因死亡率分别为（41.4±3.7）％、（44.7±5.4）％。Cox多因素回归分析结果显示：降钙素原水平>0.2 ng/ml及亚胺培南耐药的MIC≥16 µg/ml是CRO感染30 d死亡的独立危险因素。CRE亚组分析结果显示，亚胺培南耐药的MIC≥16 µg/ml为CRE感染30 d死亡的独立危险因素。CRE主动筛查患者的30 d累积生存率高于未筛查患者［（68.0±9.3）％对（50.0±6.5）％，P＝0.21］。结论高亚胺培南耐药MIC值的致病菌严重影响血液科CRO感染患者预后，病死率高。开展CRE主动筛查有助于早期预防、早期诊断和早期治疗高危患者。

Multidrug-Resistant Phenotypes of Escherichia coli Isolates in Wild Canarian Egyptian Vultures (Neophron percnopterus majorensis).

Simple SummaryIncreasing antimicrobial resistance is a global problem for both human and animal health. Escherichia coli is frequently used as a “sentinel” for antimicrobial resistance and as an indicator of faecal contamination of the environment. This study is a characterisation of the antimicrobial resistance phenotypes of E. coli isolates obtained from cloacal samples of Canarian Egyptian vultures. A total of 65 chickens and 38 adult and immature birds were studied. Antimicrobial susceptibility to 16 antibiotics of 12 different categories was determined in 103 E. coli isolates. We found a 39.8% prevalence of multidrug-resistant (MDR) E. coli. Almost all MDR phenotypes found included resistance to tetracycline, an antibiotic widely used in veterinary medicine. Resistance has also been found to chloramphenicol (13 MDR phenotypes), imipenem (5 MDR phenotypes) and others. Wild birds can act as reservoirs and disseminators of MDR E. coli, transferring them via faeces to the environment, feed or water. Our results highlight the need to minimise exposure of wild birds to antimicrobials from human activities to avoid the spread of antimicrobial resistance.The presence of multidrug-resistant (MDR) Escherichia coli in cloacal samples from Canarian Egyptian vultures was investigated. Samples were obtained from chicks (n = 65) and from adults and immature birds (n = 38). Antimicrobial susceptibility to 16 antibiotics included in 12 different categories was determined for 103 E. coli isolates. MDR was defined as acquired non-susceptibility to at least one agent in three or more antimicrobial categories. Forty-seven different resistance phenotypes were detected: 31 MDR (41 isolates) and 16 non-MDR (62 isolates). One isolate was resistant to all 12 antimicrobial categories and 2 phenotypes included resistance to 9 antimicrobial categories. Imipenem resistance was included in five MDR phenotypes, corresponding to five different isolates. Statistically significant differences in prevalence of MDR-phenotypes were found between chicks in nests and the rest of the animals, probably due to the shorter exposure time of chicks to antimicrobials. The main risk derived from MDR bacteria in scavengers is that it threatens the treatment of wild animals in rescue centres and could be transferred to other animals in the facilities. In addition to this, it could pose a health risk to veterinarians or other staff involved in wildlife protection programmes.

Rapid ResaImipenem/Acinetobacter NP Test for Detection of Carbapenem Susceptibility/Resistance in Acinetobacter baumannii.

The rapid ResaImipenem/Acinetobacter NP test was developed for the identification of carbapenem resistance among Acinetobacter baumannii isolates. The principle of this test is based on the reduction of resazurin (a viability colorant) by metabolically active bacterial cells, hence detecting bacterial growth, in the presence of a defined concentration of imipenem chosen to be slightly above that defining imipenem resistance (6 μg/ml). Bacterial growth is visually detected by a color change from blue (resazurin) to purple or pink (resorufin product). A total of 110 A. baumannii isolates, among which 61 were imipenem resistant, were used to evaluate test performance. The sensitivity and specificity of the test were found to be 100%, in comparison with broth microdilution taken as the reference standard method. The rapid ResaImipenem/Acinetobacter NP test is highly specific and sensitive and is easy to implement in routine microbiology laboratories, and results are obtained within 2 h 30 min. It does not require any specific equipment.

Co-occurrence of Carbapenemase-encoding Genes Among Klebsiella pneumoniae Clinical Isolates: Positive Relationship of bla NDM and bla SIM with Imipenem Resistance

Background: Carbapenem-resistant Klebsiella pneumoniae (CR-KP), known as a significant public health threat, is the most common causative agent of nosocomial and community-acquired infections. Objectives: This study aimed to evaluate resistance to carbapenems and determine the prevalence of carbapenemase genes and multilocus sequence typing (MLST) of K. pneumoniae clinical isolates. Methods: One-hundred K. pneumoniae isolates were evaluated. The minimum inhibitory concentrations (MIC) of imipenem and meropenem were assessed by the broth microdilution method. Multiplex-polymerase chain reaction (PCR) was applied to detect 11 carbapenemase-encoding genes belonging to different classes. The alleles and sequence types (ST) of three isolates were identified by MLST. Results: The MIC of carbapenems for the isolates ranged from 0.062 to 32 µg/mL. Overall, resistance rates to imipenem and meropenem were reported 11% and 34%, respectively. The bla IMP gene was the most abundant (78.4%), followed by bla OXA-48 (48.6%), bla GIM (27%), bla KPC (27%), bla SIM (21.6%), bla BIC (21.6%), bla NDM (16.2%), bla AIM (16.2%), bla VIM (16.2%), bla DIM (8.1%), and bla SPM (8.1%). The co-existence of carbapenemase genes was observed in 81.8% of the isolates. A positive relationship was found between the presence of bla NDM and bla SIM and resistance to imipenem. Multilocus sequence typing results showed three different sequence types, including ST14, ST5188, and ST1861. Conclusions: This study revealed a high prevalence of CR-KP isolates that suggests a high risk of horizontal gene transfer and potential to spread resistance among other strains. Since STs are reported for the first time in Iran, they can be considered as emerging strains.

Multidrug-resistant Klebsiella pneumoniae harboring extended spectrum β-lactamase encoding genes isolated from human septicemias.

Klebsiella pneumoniae is a major pathogen implicated in nosocomial infections. Extended-spectrum β-lactamase (ESBL)-producing K. pneumoniae isolates are a public health concern. We aim to characterize the type of β-lactamases and the associated resistance mechanisms in ESBL-producing K. pneumoniae isolates obtained from blood cultures in a Portuguese hospital, as well as to determine the circulating clones. Twenty-two cefotaxime/ceftazidime-resistant (CTX/CAZR) K. pneumoniae isolates were included in the study. Identification was performed by MALDI-TOF MS and the antimicrobial susceptibility testing by disk-diffusion. The screening test for ESBL-production was performed and ESBL-producer isolates were further characterized. The presence of different beta-lactamase genes (blaCTX-M, blaSHV, blaTEM, blaKPC, blaNDM, blaVIM, blaOXA-48, blaCMY-2, blaDHA-1, blaFOX, blaMOX, and blaACC) was analyzed by PCR/sequencing in ESBL-producer isolates, as well as the presence of other resistance genes (aac(6’)-Ib-cr, tetA/B, dfrA, qnrA/B/S, sul1/2/3) or integron-related genes (int1/2/3). Multilocus-sequence-typing (MLST) was performed for selected isolates. ESBL activity was detected in 12 of the 22 CTX/CAZR K. pneumoniae isolates and 11 of them carried the blaCTX-M-15 gene (together with blaTEM), and the remaining isolate carried the blaSHV-106 gene. All the blaCTX-M-15 harboring isolates also contained a blaSHV gene (blaSHV-1, blaSHV-11 or blaSHV-27 variants). Both blaSHV-27 and blaSHV-106 genes correspond to ESBL-variants. Two of the CTX-M-15 producing isolates carried a carbapenemase gene (blaKPC2/3 and blaOXA-48) and showed imipenem resistance. The majority of the ESBL-producing isolates carried the int1 gene, as well as sulphonamide-resistance genes (sul2 and/or sul3); the tetA gene was detected in all eight tetracycline-resistant isolates. Three different genetic lineages were found in selected isolates: ST348 (one CTX-M-15/TEM/SHV-27/KPC-2/3-producer isolate), ST11 (two CTX-M-15/TEM/SHV-1- and CTX-M-15-TEM-SHV-11-OXA-48-producer isolates) and ST15 (one SHV-106/TEM-producer isolate). ESBL enzymes of CTX-M-15 or SHV-type are detected among blood K. pneumoniae isolates, in some cases in association with carbapenemases of KPC or OXA-48 type.

Emergence of carbapenem resistant Acinetobacter baumannii clonal complexes CC2 and CC10 among fecal carriages in an educational hospital

ABSTRACT Carbapenem-resistant Acinetobacter baumannii strains are increasing worldwide. In this study, samples were collected from hospital environments, extra hospital environments, and fecal carriages. 76% (89/117) of bacterial isolates were detected as A. baumannii strains. The imipenem resistance in the hospital environment, fecal carriages, extra hospital environments, and clinical isolates was 37.7% (17/45), 100% (9/9), 0% (0/45), and 92.9% (92/99), respectively. The blaVIM and blaOXA-23 were detected in 6.6% (3/45) and 2.2% (1/45) of strains isolated from hospital environments. Interestingly, strains isolated from fecal carriages had blaVIM, blaOXA-23, and blaIMP genes which resembled carbapenem resistance genes in clinical strains. The structure of clonal relatedness among all non-clinical isolates was as follows: CC2, 37% (33/89); CC1, 22.4% (20/89); CC3, 12.3% (11/89); CC25, 7.8% (7/89); CC10, 4.4% (4/89) and CC15, 2.2% (2/89). Comparison of clonal relatedness among clinical and non-clinical isolates indicated that widespread clones including CC2, CC3, and CC10 were common clonal complexes between two categories.

Phenotypic and genotypic antimicrobial resistance in clinical anaerobic isolates from India.

BackgroundAntimicrobial resistance (AMR) in anaerobes remains a neglected field. The laborious procedures, non-compliance with the standard methodology and differences in interpretive breakpoints add variation in resistance data.ObjectivesTo assess the phenotypic and genotypic resistance among clinically important anaerobes to six antibiotics frequently used as empirical therapy for anaerobic infections.MethodsA total of 150 anaerobic isolates were recovered from clinical specimens. The antimicrobial susceptibility was determined by the breakpoint agar dilution method as per CLSI guidelines. The presence of genes encoding resistance to metronidazole (nim gene), imipenem (cfiA gene) and mobilizable insertion sequence (IS) elements was detected to comprehend their association with phenotypic resistance.ResultsThis is a first study of its kind from the Indian subcontinent looking at the AMR and associated genes in anaerobes. Resistance to metronidazole, clindamycin, imipenem, piperacillin/tazobactam and cefoxitin was 32.6%, 42.6%, 0.6%, 38% and 35.3%, respectively. No resistance was observed to chloramphenicol. The nim gene was detected in 24.6% of isolates, of which 70.2% were resistant by phenotype. On sequencing, the PCR products of six random nim genes showed a close similarity to nimE of Bacteroides fragilis with 99% nucleotide and 100% amino acid sequence similarity. The cfiA gene, associated with imipenem resistance, was detected in 16% of isolates.ConclusionsThe possibility of isolates carrying AMR genes to become resistant to antibiotics by acquisition of IS elements mandates attention to periodically monitor the resistance patterns and geographic distribution of these genes and IS elements to understand the trends of AMR in anaerobes.

Molecular characterization of metronidazole resistant Bacteroides strains from Kuwait

Eleven metronidazole resistant Bacteroides and one newly classified Phocaeicola dorei strain from Kuwait were investigated for their resistance mechanisms and the emergence of their resistant plasmids. All but one strain harbored nimE genes on differently sized plasmids. Of the 11 nimE genes, 9 were preceded by full copies of the prototype ISBf6 insertion sequence element, one carried a truncated ISBf6 and one was activated by an additional copy of IS612B. Nucleotide sequencing results showed that the nimE ISBf6 distances were constant and all five different plasmids shared a common region, suggesting that (i) the nimE-ISBf6 configuration was inserted into an undisclosed common genetic element, (ii) over time, this common element was mutated by insertions and deletions, spreading the resultant plasmids. Of the 10 B. fragilis strains in this collection, 6 were also cfiA-positive, one with full imipenem resistance, indicating a tendency for multidrug resistance (MDR) among such isolates. The significant number of metronidazole resistant Bacteroides spp. and P. dorei strains with the MDR phenotype warns of difficulties in treatment and suggests promoting adherence to antibiotic stewardship recommendations in Kuwait.

Emergence of Clinical Pseudomonas aeruginosa Isolate Guangzhou-PaeC79 Carrying crpP, blaGES-5, and blaKPC-2 in Guangzhou of China.

As a potential "Superbug," Pseudomonas aeruginosa remains the leading concern in antimicrobial resistance. In this study, the emergence of clinical P. aeruginosa isolate was found to carry crpP and blaGES-5 on the chromosome and blaKPC-2 on a plasmid. A clinical P. aeruginosa strain Guangzhou-PaeC79 with an extensively drug-resistant phenotype was isolated, which was resistant to all classes of clinical commonly used antibiotics. It contains one chromosomal DNA and one plasmid, with seven acquired antimicrobial resistance genes identified on the chromosome, including carbapenem resistance gene blaGES-5 and fluoroquinolone resistance gene crpP, and carbapenem resistance gene blaKPC-2 located on an IncP-6-type plasmid pPAEC79 carrying a Tn3-like element. Carriage of any two of the resistance genes has never been previously reported, and simultaneous carriage of three bla and crpP may explain the bacterial phenotype as high-level resistance to imipenem and meropenem (≥16 μg/mL) and resistance to ciprofloxacin and levofloxacin.

The Role of Uniform Meropenem Usage in Acinetobacter baumannii Clone Replacement.

The dominant carbapenem resistant Acinetobacter baumannii harboring blaOXA-23-like carbapenemase was replaced by blaOXA-40-like carriers in a Hungarian tertiary-care center with high meropenem but relatively low imipenem use. We hypothesized that alterations in antibiotic consumption may have contributed to this switch. Our workgroup previous study examined the relation between resistance spiral and the antibiotic consumption, and the results suggest that the antibiotic usage provoked the increasing resistance in case of A. baumannii. We aimed at measuring the activity of imipenem and meropenem to compare the selection pressure exerted by the different carbapenems in time-kill assays. Strain replacement was confirmed by whole genome sequencing, core-genome multilocus sequence typing (cgMLST), and resistome analysis. Based on results of the time-kill assays, we found a significant difference between two different sequence-types (STs) in case of meropenem, but not in case of imipenem susceptibility. The newly emerged ST636 and ST492 had increased resistance level against meropenem compared to the previously dominant ST2 and ST49. On the other hand, the imipenem and colistin resistance profiles were similar. These results suggest, that the uniform meropenem usage may have contributed to A. baumannii strain replacement in our setting.

Imipenem Resistance Gram-Negative Bacilli Isolated from Patients of a Tertiary Care Hospital in Dhaka, Bangladesh

Introduction: The emergence of antibiotics resistance bacteria is a persistent global problem affecting public health. The occurrence and widespread resistance to Imipenem among hospital bacterial isolates can constitute a significant threat to chemotherapy.
 Objectives: This cross-sectional study aimed to investigate the imipenem resistant pattern among gram-negative bacilli isolated from different samples in Dhaka medical college hospital.
 Methods: A total of 300 samples (wound swab, urine, endotracheal aspirate, blood, and sputum) were collected from July 2015 to June 2016. Two hundred four gram-negative bacilli were isolated and tested for resistance to imipenem by the disc diffusion method.
 Results: Among 204-gram negative bacilli, 39.21% imipenem resistance was detected by the Disc Diffusion method. 14.7% imipenem resistance gram-negative bacilli were from wound swab. 83.33% of Acinetobacter baumannii were Imipenem resistant.
 Conclusions: Imipenem resistance is widespread among gram-negative bacilli isolated from human infections. Imipenem resistance (39.21%) found in the study is quite worrisome.
 J Shaheed Suhrawardy Med Coll, December 2020, Vol.12(1); 3-5

Retrospective study of incidence of metallo-β -lactamase-producing Non-fermenters in nosocomial infections of a tertiary care hospital, in Navi Mumbai

The growing increase in the rate of antibiotic resistance is a major cause for concern in both non-fermenting bacilli. β-lactams have been the mainstay of treatment for serious infections, and the most active of these are the carbapenems. Acquired metallo-β-lactamases (MBL) have recently emerged as one of the most worrisome resistance mechanisms owing to their capacity to hydrolyze all β-lactams, including carbapenems. We have undertaken this investigation to ascertain the incidence of MBL-producing non-fermenting bacilli, like Pseudomonas Spp. and Acinetobacter Spp.To determine the incidence of MBL in Nosocomial infections of non-fermenters and their clinical correlation.Screening of nosocomial isolates for multidrug resistance by antibiotic sensitivity tests as per CLSI guidelines as a reference.To perform phenotypic confirmatory test of potential MBL isolates by double disc synergy testClinical correlation with detection of these enzymes and the patients morbidity/mortality correlation with age, immunocompromised status and hospital stay.The study was conducted over a period of 12 months in a teaching hospital, in Navi Mumbai. Isolates included in the study were screened for imipenem resistance by conventional methods. The isolates that showed imipenem resistance were tested for MBL production by imipenem (IMP)-ethylene-diamine-tetra-acetic acid (EDTA) combined disc test. Imipenem-resistant non-MBL isolates also were tested for Modified Hodge test and AmpC β-lactamases production to detect other mechanisms of carbapenem resistance. Total number of isolates tested were 107.Out of 107, 29 (27.1%) were MBL producers and 78(72.9%) were non- MBL producers. Among both types of non-fermenters , 66(61.68%) were Pseudomonas aeruginosa and 41(32.23%) were of Acinetobacters. In the sex distribution, 65.5%were males and 34.5% were females.18.18% were MBL positive Pseudomonas and among Acinetobacter species 41.46% were MBL positive. Mean age of MBL producers was 34 years. Mean hospital stay was 28 days. Mortality rate was 51.7% in MBL producers. Mortality was higher in Acinetobacter MBL producers.when compared to Pseudomonas MBL producers.

Mycobacterium Tuberculosis, Culturing and PCR Optimization

The genus Acinetobacter baumannii has undergone substantial taxonomic modifications over the last 30 years. Acinetobacter baumannii is one of the most important representatives of the genus and pathogen for healthcare facilities globally. Over the last 15 years, its clinical significance shows that it has the ability to acquire resistance against antibiotics in this threatening antibiotic era. Naturally A.baumannii can easily be isolated from different sources throughout whole world, found mostly in water, soil, sputum and many healthcare environments, is a non-fermenting, non-spore forming and gram negative coccobacilli. Pneumonia caused by MDR strains of Acinetobacter baumannii creating serious issues for Physicians to treat it properly. Risk factor for two types of patients recognized to pneumonia infection Acinetobacter baumannii hospital associated pneumonia (AHAP) and Acinetobacter baumannii ventilator associated pneumonia (AVAP), by univariate analysis prior to ceftazidime treatment. It is to be reported that potential risk factors for AVAP includes, imipenem resistance, long duration of hospital stay and fluoroquinolones exposure.

Bacterial Ecology of Otorrhea at the Laquintinie Hospital in Douala, Cameroon

Background: Otitis media is an inflammation of the lining of the middle ear, involving the eardrum, ancillary cavities and the auditory tube. Prolonged, it can be suppurative. The etiology can be bacterial, fungal or viral. The observation of this disease led us to do this study to look for possible treatment alternatives. Method: We conducted a prospective, descriptive and cross-sectional study, from February 1 to May 3, 2013 at Laquintinie hospital in Douala. The samples taken were cultured, the identification of the strains made by the galleries API (20E ™, STAPH, 20 STREP), the study of the sensitivity to antibiotics and antifungals by the method of diffusion of discs on agar. Results: 38.3% of patients had infected left ear, 53.2% right ear and 8.5% had bilateral otitis. In 50.5% of pus, at least 2 germs were isolated. 95.7% of samples were culture positive and 4.3% negative. 79.1% of bacteria were isolated against 20.9% of fungals. Pseudomonas aeruginosa was mostly isolated (50.9%) followed by staphylococcus aureus (15.1%). We had better susceptibility of Pseudomonas aeruginosa to imipenem (88.5%), piperacillin (80.8%), ciprofloxacin (76.2%) and significant resistance to ticarcillin (7.7%). The best sensitivity of Candida is that of ketoconazole (92.9%). Conclusion: The bacterial profile is different from that encountered in most Western countries. The main etiologies are: Pseudomonas aeruginosa and Staphylococcus aureus. Fungals were also present. Imipenem and ketoconazole are the antibiotic and antifungal of choice, respectively.

Bacteriological Profile and Antibiotic Sensitivity Pattern in Infected Diabetic Foot Ulcers

Objectives: To identify the common bacterial pathogens responsible for infection in diabetic foot ulcer and their sensitivity pattern to different antibiotics. Methods: This prospective observational study was conducted from 24th June 2019 to 27th December 2019 at Services Institute of Medical Sciences Lahore. Specimens of discharge from diabetic foot ulcers (DFU) were received from Diabetes Management Centre (DMC). Cultures were put up and bacteria isolated were identified by standard methods. Antibiotic sensitivity was determined by Kirby-Bauer disc diffusion method. Results: Samples from DFU of 50 patients were processed. Thirty-six (72%) samples were from males and 14(28%) were from females; mean age of patients was 53±9.5 years. Forty-nine (98%) patients had unsatisfactory glycemic control. Forty three (86%) samples were growth positive while 07(14%) were bacteriologically sterile. Monomicrobial infection was observed in 38 (76%) cases while polymicrobial infection was seen in 12 cases (24%). The most common isolates were Staphylococcus aureus 14(28%), Pseudomonas species 11 (22%) and Proteus species 10 (20%). Forty three percent of Staphylococcus aureus, were methicillin resistant (MRSA). All MRSA remained sensitive to vancomycin and linezolid. In Pseudomonas species, resistance to third generation cephalosporins, ceftazidime , was 27%, while resistance to imipenem was seen in 3 (9%) of isolates. In Proteus species, resistance to third generation cephalosporins was 90% while to imipenem resistance was 60%. Resistance to commonly prescribed quinolones was more than 70% among all the bacterial isolates. Conclusions: Common Gram positive and Gram negative organisms responsible for infection in DFU were Staphylococcus aureus, Pseudomonas species and Proteus species. The isolates were multi-drug resistant (MDR). Resistance to antibiotics used as empiric therapy was high. Keywords: Diabetic foot ulcer, antibiotic resistance, empiric therapy

Black hairy tongue associated with linezolid therapy in a patient with mycobacterial abscesses infection- Report from rural india

Background: Black Hairy tongue consists of a benign condition related to abnormal keratin build-up in filiform papillae, giving them an elongated hair-like appearance. We report a case of a 35 y/m presented who developed black discoloration of tongue while on linezolid therapy. Case Description: A 35 y/m, presented to gastroenterology OPD with chief complaints of on and off chromic discharging sinuses from port site right hypochondrium since past 1 y. Pus swabs taken from discharging site were taken and sent for gram stain, ZN stain and culture. Gram stain showed few pus cells,gram positive cocci in clusters. ZN stain showed few acid fast bacilli. Discussion: Bacterial culture grew MSSA and LJ media showed growth of rapidly growing mycobacteria(RGM) after 6 d of incubation. RGM was further identified by HAINS genotypic assay as Mycobacterium abscesses subspecies abscesses. Antibiotic susceptibility was performed on Middlebrook 7H11 with OADC and isolate was found to be sensitive to amikacin, gentamycin,imipenem and linezolid and resistance to macrolides, fluroquinolones and doxycycline. Diagnosis of MSSA and Mycobacterium abscesses infection was made and patient was started on amikacin and linezolid 600 mg OD. On 16thday of therapy patient developed dark discoloration of dorsum of tongue, teeth and oral mucosa. Other antibiotics, drugs, poor oral hygiene, smoking, and consumption of coffee or other coloured beverages were rule out as risk factors. Patient was switched on to meropenem and aminoglycoside. Discoloration improved after three weeks of discontinuing Linezolid. Conclusion: The diagnosis of BHT primarily relies on a visual intra- oral examination. Described adverse reaction is uncommonly described with prolonged Linezolid therapy.Careful review of known precipitating factors and recent medication changes is also fundamental in the diagnosis of BHT. Overall clinical prognosis of BHT is excellent.

Antimicrobial resistance and metallo-beta-lactamase producing among commensal Escherichia coli isolates from healthy children of Khuzestan and Fars provinces; Iran

BackgroundThe emergence of metallo-β-lactamase (MBL)-producing isolates is alarming since they carry mobile genetic elements with great ability to spread; therefore, early detection of these isolates, particularly their reservoir, is crucial to prevent their inter- and intra-care setting dissemination and establish suitable antimicrobial therapies. The current study was designed to evaluate the frequency of antimicrobial resistance (AMR), MBL producers and identification of MBL resistance genes in Escherichia coli strains isolated from fecal samples of the healthy children under 3 years old. A total of 412 fecal E. coli isolates were collected from October 2017 to December 2018. The study population included healthy infants and children aged < 3 years who did not exhibit symptoms of any diseases, especially gastrointestinal diseases. E. coli isolates were assessed to determine the pattern of AMR. E. coli isolates were assessed to determine the pattern of AMR, the production of extended spectrum β-lactamase (ESBL) and MBL by phenotypic methods. Carbapenem-resistant isolates were investigated for the presence of MBL and carbapenemase genes, plasmid profiling, and the ability of conjugation.ResultsIn sum, AMR, multi-drug resistance (MDR) and ESBL production were observed in more than 54.9, 36.2 and 11.7% of commensal E. coli isolates, respectively. Out of six isolates resistant to imipenem and meropenem, four isolates were phenotypically detected as MBL producers. Two and one E. coli strains carried the blaNDM-1 and blaVIM-2 genes, respectively and were able to transmit imipenem resistance through conjugation.ConclusionOur findings showed that children not exposed to antibiotics can be colonized by E. coli isolates resistant to the commonly used antimicrobial compounds and can be a good indicator for the occurrence and prevalence of AMR in the community. These bacteria can act as a potential reservoir of AMR genes including MBL genes of pathogenic bacteria and lead to the dissemination of resistance mechanisms to other bacteria.

Emergence of Imipenem Resistance in a CpxA-H208P-Variant-Producing Proteus mirabilis Clinical Isolate

The Proteus mirabilis PmirS clinical isolate, which was susceptible to imipenem (0.5 μg/mL) and amikacin (1 μg/mL), was recovered from a bronchial aspirate of a patient who recently underwent lung transplantation. The P. mirabilis PmirR clinical isolate, which exhibited resistance to imipenem (16 μg/mL) and amikacin (24 μg/mL), was isolated 3 weeks later from the same patient and the same specimen type. Using short-read sequencing technology, these isolates appeared to be genetically identical except the cpxA gene of the PmirR isolate that was mutated leading to the His-208-Pro substitution. The structural alteration was localized in the histidine kinase, adenylate cyclase, methyl accepting protein, phosphatase (HAMP) domain, which is involved in the signal transduction between the sensor kinase and the regulator response of the CpxA/CpxR two-component system (TCS). No significant defect in the growth rate was found between the PmirS and PmirR isolates. This study suggests that alteration in CpxA might confer imipenem and amikacin resistance in P. mirabilis. This study brings new evidence that the TCS alteration could provide an adaptive capacity in a clinical context by conferring antibiotic resistance without fitness cost.

Activity of imipenem/relebactam against Pseudomonas aeruginosa producing ESBLs and carbapenemases.

ESBL- and carbapenemase-producing Pseudomonas aeruginosa are prevalent in, for example, the Middle East, Eastern Europe and Latin America, though rarer elsewhere. Because P. aeruginosa readily mutate to become carbapenem resistant via loss of OprD, isolates producing ESBLs are often as broadly resistant as those producing carbapenemases. We hypothesized that: (i) relebactam might overcome class A carbapenemases directly in P. aeruginosa; and (ii) relebactam's inhibition of AmpC, which gives a generalized potentiation of imipenem against the species, might restore imipenem susceptibility in OprD-deficient ESBL producers. MICs were determined using CLSI agar dilution for P. aeruginosa isolates producing ESBLs, principally VEB types, and for those producing GES-5, KPC and other carbapenemases. Relebactam potentiated imipenem by around 4-8-fold for most P. aeruginosa isolates producing VEB and other ESBLs; however, MICs were typically only reduced to 4-16 mg/L, thus mostly remaining above EUCAST's susceptible range and only partly overlapping CLSI's intermediate range. Strong (approx. 64-fold) potentiation was seen for isolates producing KPC carbapenemases, but only 2-fold synergy for those with GES-5. Predictably, potentiation was not seen for isolates with class B or D carbapenemase activity. Relebactam did potentiate imipenem against ESBL-producing P. aeruginosa, which are mostly imipenem resistant via OprD loss, but this potentiation was generally insufficient to reduce imipenem MICs to the clinical range. Imipenem resistance owing to KPC carbapenemases was reversed by relebactam in P. aeruginosa, just as for Enterobacterales.

Comparative genomics of the sequential Pseudomonas aeruginosa isolates obtained from the continuous imipenem stress evolution.

Pseudomonas aeruginosa is a major opportunistic human pathogen that causes nosocomial infections, and the proportion of carbapenem resistance has recently dramatically increased in P. aeruginosa due to the overuse of them. In this study, strains G10 and G20, with minimum inhibitory concentration (MIC) of imipenem of 16μg/ml and more than 32μg/ml, were isolated during continuous subculture of cells exposed to stepwise increasing concentrations of imipenem, respectively. The genomes of G10 and G20 were sequenced and compared with parental strain (P. aeruginosa ATCC 27853, G0). There were 59, 59, and 58 genes involved in antibiotic resistance which were predicted in G0, G10, and G20, respectively, while 374, 366, and 363 genes involved in virulence factors were identified among these three strains. Due to the significantly different MICs of imipenem and highly similar profiles of antibiotic resistance and virulence factors related genes among three strains, the specific genetic variations that occurred were identified and compared, including single nucleotide polymorphisms (SNPs), insertions and deletions (InDels), and structural variations (SVs). The increase in the MIC of imipenem was proposed to be linked to mutations involved in polyamine biosynthesis, biofilm formation, OprD, and efflux pump functions. This study aims to clarify the underlying mechanism of imipenem resistance and provide alternative strategies for reducing resistance in P. aeruginosa. KEY POINTS: • Strains with different imipenem MIC were obtained via laboratory selection evolution. • Whole genomes of two strains with different MIC of imipenem were sequenced. • Underlying mechanism of imipenem resistance was clarified via comparative genomics.