Gentamicin-resistant Enterococcus Research Articles

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Enterococci, the normal inhabitant of human intestinal tract are now emerging as potential pathogens asssociated with healthcare infections despite their low virulence. The rise in antibiotic resistance has a profound impact on the treatment of infectious diseases and the consequences due to its complications. Stool samples were obtained from children under the age of 14 years, admitted to pediatrics ward of a tertiary care hospital. The identification of enterococcal isolates was followed by suitable biochemical assays, disc diffusion and the E test to assess antibiotic susceptibility and minimum inhibitory concentrations. Vancomycin (van A, van B) and gentamicin resistance genes (aac(6)-Ie-aph(2)-Ia) were detected using PCR. From the total of 300 stool samples, Enterococcus spp were isolated in 132, out of which 39 were E. faecalis and 93 were E. faecium. Highest percentage of resistance was noted against erythromycin (68%) followed by penicillin (48%) and high level gentamicin in (34%) of the isolates. Resistance to high level gentamicin by MIC was found to be 25%. The MIC of vancomycin ranged from 1.5 μg/ml - 4 μg/ml of which 16% of the isolates had an MIC of 4 μg/ml. Resistance gene for aac(6)-Ie-aph(2)-Ia(gentamicin resistance) was found in 25% of isolates and van A (Vancomycin resistance) was detected in 11% of the isolates and none of the isolates harbored van B gene. Feacal carriage of gentamicin resistant enterococcus species was high in pediatric inpatients. No resistance was seen for vancomycin.

Genomic Features of High-Level Gentamicin-Resistant Enterococcus faecalis Strain LREF-1 from India.

ABSTRACTEnterococcus faecalis strain LREF-1 was isolated from a urine sample from India; it belongs to sequence type 28 (ST28), which is associated with nosocomial infections. The strain carries genes for resistance to multiple antibiotics and resistance to various drug classes, including tetracycline, erythromycin, and high-level gentamicin, along with virulence factors.

Companion psittacine birds as reservoir of gentamicin and vancomycin-resistant Enterococcus spp.

ABSTRACT: Enterococcus are recognized worldwide as significant nosocomial agents that have been continuously envolving to adapt to different niches and acquire resistance to several antibiotic classes. Vancomycin and gentamicin-resistant strains of E. faecalis and E. faecium have been associated with nosocomial human infections. Some epidemiological studies suggest the participation of pets as reservoirs of vancomycin and gentamicin-resistant Enterococcus strains. However, the role of companion birds as reservoirs of these strains has been poorly studied. In this study, 126 psittacine birds were evaluated and 26.9% carried Enterococcus spp., including the species E. faecalis, E. faecium, E. hirae, E. phoeniculicola, E. gallinarum and E. casseliflavus. The antibiotic resistance profile showed four high-level gentamicin-resistance (HLGR) strains. In addition, two strains presented intermediate levels of vancomycin resistance. Resistant strains were isolated from fecal and oropharynx samples of sick and clinically healthy birds, suggesting that psittacine birds may act as reservoirs of HLGR Enterococcus spp. However, sick birds appear to be more implicated in the enterococci transmission than healthy birds.

Molecular characterization of antimicrobial-resistant Enterococcus faecalis and Enterococcus faecium isolated from layer parent stock

Enterococcus faecalis (E. faecalis) and Enterococcus faecium (E. faecium) are ubiquitous intestinal bacteria in humans and animals that can easily acquire antimicrobial resistance, which allows them to have roles as antimicrobial resistance indicators. In addition, layer parent stock produces thousands of eggs for the production of commercial laying hens and can transfer a variety of viral and bacterial agents to chicks. The objective of this study was to determine the prevalence and characteristics of antimicrobial-resistant E. faecalis and E. faecium isolated in the layer parent stock level of the egg-layer operating system in South Korea. A total of 129 E. faecalis and 166 E. faecium isolates from 74 flocks of 30 layer parent stock were tested for resistance in this study. The prevalence of doxycycline- (51.9%), erythromycin- (53.5%), high-level gentamicin- (13.2%), high-level kanamycin- (31.0%), high-level streptomycin- (30.2%), and tetracycline- (64.3%) resistant E. faecalis isolates were higher than those for E. faecium isolates (P < 0.05). The ermB gene was detected in 66 (95.7%) erythromycin-resistant E. faecalis isolates, which was higher than that of 32 (71.7%) erythromycin-resistant E. faecium isolates. Twenty-one high-level gentamicin-resistant Enterococcus spp. (17 E. faecalis and 4 E. faecium) carried at least one aminoglycoside-modifying enzyme gene, aac(6')Ie-aph(2')-Ia or ant(6)-Ia. Fourteen isolates that harbored both aac(6')Ie-aph(2')-Ia and ant(6)-Ia exhibited pattern A with IS256 at both ends. Ten high-level ciprofloxacin-resistant Enterococcus spp. (8 E. faecalis and 2 E. faecium) showed amino acid changes from serine to isoleucine at codons 83 in gyrA, and 80 in parC. Also, the virulence genes ace, asa1, efaA, and gelE were detected in this study. To the best of our knowledge, this is the first study to examine the prevalence and characteristics of antimicrobial-resistant E. faecalis and E. faecium isolates in the layer parent stock. Our findings support the need for a surveillance program to monitor the emergence of antimicrobial-resistant E. faecalis and E. faecium in layer operating system.

Adjunctive gentamicin did not improve outcome of enterococcal bacteraemia in neutropenic patients: a propensity scored matched study

Background: Patients with haematologic malignancies receiving chemotherapy have a high risk of developing febrile neutropenia and bloodstream infections. The benefit of adjunctive gentamicin treatment for enterococcal bloodstream infections is debated. In this study, we compare the treatment outcome of a cell wall-active antibiotic with and without gentamicin for enterococcal bacteraemia in patients with neutropenia.Methods: The observational study was performed from 1999 through 2016. Patients with bacteraemia due to non-high level gentamicin-resistant enterococci were included. Analyses were performed in two data sets of episodes with enterococcal bacteraemia. One data set consisting of all included episodes (full cohort, n = 154) and one with propensity score-matched episodes (n = 96). The primary endpoint was death within 30 days, and the secondary outcomes were defervescence and persistence of enterococcal bloodstream infection after initiation of anti-enterococcal therapy.Results: Episodes with gentamicin treatment (n = 82, full cohort; n = 48, propensity score-matched cohort) were comparable with episodes without gentamicin treatment (n = 72, full cohort; n = 48, propensity score-matched cohort) with regard to patient- and disease-related characteristics. Enterococcus faecium (40.9%) was the most frequently isolated organism. In the propensity score-matched cohort, there was no difference in 30-days mortality (14.6% in episodes with gentamicin versus 16.7% in episodes without gentamicin, p = 1), median time to defervescence (1 versus 2 days, p = .37) or persistence of enterococcal bloodstream infection for ≥72 h (9.4% versus 7.5%, p = 1).Conclusions: In our study with neutropenic patients, treatment with a cell wall-active antibiotic without adjunctive gentamicin for episodes with enterococcal bloodstream infection was as effective as combination therapy with gentamicin.

Prevalence of high-level gentamicin-resistant Enterococcus faecalis in an Iranian hospital

This study was designed to determine the molecular characteristic and antimicrobial resistance of e nterococcal strains isolated from patients in an Iranian Hospital. Enterococcal strains were isolated from the burn patients. All strains were screened for genes encoding resistance to aminoglycoside [ aac(6 ' )-Ie-aph(2 '' )-Ia , aph (3') , ant (4' )], resistance to vancomycin ( vanA , vanB ), resistance to tetracycline ( tetK , tetL , tetM , tetO ), and resistance to erythromycin ( ermA , ermB , ermC ) by PCR and multiplex PCR–based methods. Genetic diversity was evaluated using Random Amplified Polymorphic DNA (RAPD)-PCR. All enterococcal isolates showed complete sensitivity to vancomycin with MIC ≤ 0.5µg/ml. Resistance to gentamicin, tetracycline, erythromycin, ciprofloxacin or quinopristin-dalfopristin was detected, whilst more than 96.2% of isolates were high-level gentamicin-resistant (HLGR) and multiresistant. The most prevalent aminoglycoside resistance gene was aac(6 ' )-Ie-aph(2 '' )-Ia, found in 96.2% (26/27) of the isolates. The most prevalent tetracycline resistance gene was tetM , found in 85.1% (23/27) of the isolates followed by tetL and tetO found in 7.4% (2/27) of the isolates. The ermA and ermB genes were detected in 33.3% (9/27) and 44.4% (12/27) of the isolates respectively. Random Amplified Polymorphic DNA (RAPD)-PCR analysis yielded 17 distinct profiles among 27 investigated isolates. One clusters of isolates shared the same RAPD patterns, while 16 isolates had unique RAPD patterns. we found that over the examined time period one RAPD genotype were common type and were disseminated among patients in the burn unit. Interestingly, most of these strains had an identical or very similar antibiotic and gene resistance pattern.

Prevalence, antimicrobial resistance and genetic lineages of Enterococcus spp. from vegetable food, soil and irrigation water in farm environments in Tunisia.

The objective of this study was to determine the species, clonal diversity, antibiotic resistance and virulence of enterococci in different environments. Seventy-one samples of farm origin (34 of food vegetables, 27 of soil and ten of irrigation water) and 19 samples of vegetables from five markets, were inoculated in Slanetz-Bartley agar plates supplemented or not with gentamicin (SB-Gen and SB plates, respectively) for enterococci recovery. Enterococci were obtained from 72.2% of tested samples in SB media (food vegetables from farms, 88.2%; soil and irrigation water, 51%; food vegetables from markets, 84.2%), and 65 enterococcal isolates were obtained. Enterococcus faecium was the most prevalent species (52.3%), followed by E. hirae (35.4%), E. faecalis (6.15%), and E. casseliflavus (6.15%). Antibiotic resistance detected among these enterococci was as follows (percentage/detected gene): ciprofloxacin (60%), erythromycin (18.4%/erm(B)), tetracycline (15.4%/tet(M)-tet(L)), kanamycin (15.4%/aph(3')-III), chloramphenicol (7.7%), streptomycin (3%/ant(6)), vancomycin (6.15%/vanC2)), teicoplanin (0%) and ampicillin (0%). High-level gentamicin-resistant (HLR-G) enterococci were detected in SB-Gen plates in 14 of 90 tested samples (15.5%), and 15 isolates were characterized: ten E. faecalis, four E. faecium and one E. hirae. All HLR-G enterococci carried the aac(6')-aph(2″), erm(B) and tet(M) genes, among other resistance genes. The HLR-G isolates showed high genetic diversity (ten different PFGE profiles), and were ascribed to the sequence types ST2, ST16, ST28 and new ST528 (in E. faecalis), and ST56, new ST885 and new ST886 (in E. faecium). Food vegetables in the farm or market settings are frequently contaminated by HLR-G enterococci, and these microorganisms could reach the human intestine through the food chain, if hygienic conditions are not followed. © 2015 Society of Chemical Industry.

Environmental enterococci: I. Prevalence of virulence, antibiotic resistance and species distribution in poultry and its related environment in Karachi, Pakistan

Enterococci are well-established causative agents of a number of diseases in humans and animals alike. A total of 1047 isolates (838 presumptive enterococci and 209 non-enterococci), related to poultry environment (faeces/manure, feed, water and air), were evaluated for species diversity, virulence potential, antibiotic resistance and associated threats. Multiplex PCR of 204 presumptive enterococci using genus (16s rDNA)- and species-specific (superoxide dismutase) primer set leads to identification of six Enterococcus spp., i.e. Ent. faecium, Ent. faecalis, Ent. mundtti, Ent. hirae, Ent. gallinarum and Ent. casseliflavus. BOX-PCR analysis of the representative strains confirmed inter-strain variation among species. Although enterococci generally appear to be catalase negative, Ent. faecalis from some faecal, water and air samples showed catalase production. In vitro assays identified poultry environment as a reservoir of MVD and MAR enterococci and non-enterococci. In addition to vancomycin, high-level-ampicillin-, clarithromycin-, erythromycin-, kanamycin- and gentamicin-resistant enterococci and non-enterococci are also indicated. Our results show that virulence potential and resistance vary with the source of isolation. Our studies on MAR and MVD enterococci in environment, especially in air and water, clearly indicate the need for a serious commitment to deal with pathogenic enterococci associated with poultry for preventing transmission of infectious agent to humans. Significance and Impact of the Study This study demonstrates that poultry environment of Karachi city harbours a diverse reservoir of Enterococcus spp. with multiple antibiotic resistance and virulence determinants. It is expected that the results will help in assessing the impact of multiple antibiotic resistance and virulent enterococci on public health, improvement of farm management practices and preventing their dissemination. Our findings strongly suggest the need for reducing antibiotic usage during poultry production, particularly those that are being used to treat human infections.

Design, Synthesis, and Antibacterial Activity of Demethylvancomycin Analogues against Drug‐Resistant Bacteria

Five novel N-substituted demethylvancomycin derivatives were rationally designed and synthesized by using a structure-based approach. The in vitro antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA), gentamicin-resistant Enterococcus faecalis (GRE), methicillin-resistant Streptococcus pneumoniae (MRS), and vancomycin-resistant Enterococcus faecalis (VRE) were evaluated. One of the compounds, N-(6-phenylheptyl)demethylvancomycin (12 a), was found to exhibit more potent antibacterial activity than vancomycin and demethylvancomycin. Compound 12 a was also found to be ~18-fold more efficacious than vancomycin against MRSA; however, the two compounds were found to have similar efficacy against MRS. Furthermore, compound 12 a exhibited a favorable pharmacokinetic profile with a half-life of 5.11±0.52 h, which is longer than that of vancomycin (4.3±1.9 h). These results suggest that 12 a is a promising antibacterial drug candidate for further preclinical evaluation.

Molecular characterization of high-level gentamicin-resistant Enterococcus faecalis from chicken meat in Korea

Because the intrinsically antimicrobial-resistant Enterococcus has acquired high-level aminoglycoside resistance genes, treating enterococcal infections is difficult. In this study, of the 101 food-borne Enterococcus faecalis isolates collected from retail chicken meat between 2003 and 2010, 11 high-level gentamicin-resistant (HLGR) E. faecalis isolates (MICs>2,048μg/mL) were found. Molecular characterization was performed to determine the basis of this resistance. All HLGR E. faecalis isolates encoded aac(6′)-Ie–aph(2″)-Ia and harbored at least 3 virulence traits in the asa1, esp, gelE, efaA, ace, and cylA genes. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed to characterize their molecular epidemiology. A total of 8 sequence types (STs), including 3 novel STs, were identified (ST35, ST82, ST116, ST202, ST300, ST403, ST407, and ST420). ST82, which is associated with amyloid arthropathy in poultry, was the most prevalent ST among HLGR E. faecalis isolates (4 out of 11 isolates, 36.4%); all other STs were identified in the isolates as well. The STs of food-borne HLGR E. faecalis in this study have been confirmed as corresponding to clinical isolates in the MLST database (DB), except for ST300 and the new STs. Three out of 11 isolates belonged to CC116, including ST116, ST407, and ST420. This study characterized HLGR E. faecalis isolates and provided evidence for the spread of HLGR E. faecalis with virulence factors to chicken sources in Korea. The emergence of food-borne HLGR E. faecalis suggests that chicken could be a potential source of transmission of antimicrobial resistance and virulence factors.

Virulence traits and antibiotic resistance among enterococci isolated from Eurasian otter (Lutra lutra)

Enterococci are ubiquitous microorganisms found as part of the normal intestinal microbiota of many animals such as the free-ranging Eurasian otter (Lutra lutra Linnaeus, 1758). In this work, twenty-nine enterococci isolated from fecal samples of Eurasian otters free-living in reservoirs and associated river stretches in South Portugal were identified and typed by conventional/molecular methods and screened for virulence factors and antibiotic resistance. Identification allocated the isolates to the species Enterococcus faecalis (19), E. faecium (9) and E. durans (1) and PCR-fingerprinting revealed their high genomic diversity. Regarding virulence factors, three isolates produced cytolysin and six were gelatinase-positive. Genes ace and acm were detected in five enterococci each, ebpABC in seventeen, gelE in fourteen and cylA in three. All isolates showed resistance patterns and antibiotic resistance genes tet(M) and pbp5 were detected in seventeen isolates each, whereas vanB and vanD were identified in thirteen and five, respectively, being most van-harboring isolates members of E. faecium. The aac(6')-Ie-aph (2″) gene, encoding for gentamicin resistance, was observed in all gentamicin-resistant enterococci. Since all isolates harbor virulence and/or antibiotic resistance traits, the role of free-living Eurasian otters in the dissemination of virulent/resistant enterococci among other animals sharing the same ecological niche cannot be disregarded, as well as the health risk they may represent for humans directly interacting with them or their habitat.

Molecular screening of virulence genes in high-level gentamicin-resistant Enterococcus faecalis and Enterococcus faecium isolated from clinical specimens in Northwest Iran

Purpose: The present study screened clinical isolates of Enterococcus faecalis and Enterococcus faecium to determine the prevalence of high-level gentamicin-resistant enterococci and the potential virulence genes among them. Materials and Methods: Clinical enterococcal isolates were obtained from three university teaching hospitals in Northwest Iran. Isolated enterococci were identified phenotypically followed by antibiotic susceptibility testing. Multiplex PCR was performed for the detection of genus, species-specific targets, gentamicin resistance, and potential virulence genes. Results: Of 220 enterococcal isolates, 133 (60.45%) isolates were identified as high-level gentamicin-resistant. Of these isolates, 79 (59.4%) and 54 (40.6%) were E. faecalis and E. faecium, respectively. All high-level gentamicin-resistant strains carried aac(6′)Ie-aph(2″)Ia. Of 220 isolates, 65.9% were positive for gelE, and 55%, 53.6%, 51.8%, and 49.5% of isolates were positive for cpd, asa1, ace, and esp, respectively. Phenotypically detected β-haemolytic strains (19.54%) were found to possess cylLlsMAB. Conclusion: The study revealed that high-level gentamicin-resistance was related to the presence of aac(6′)Ie-aph(2″)Ia. Isolated enterococci harboured potential virulence determinants, which were more common among E. faecalis than among E. faecium strains.

Evaluation of Genetic Pattern of Gentamicin-resistant Enterococci Isolated from Clinical Samples.

Background and aims Enterococci are among resistant microorganisms to antibiotics and are responsible for some of acute gingival infections. This study aimed at molecular evaluation of gentamicin-resistant enterococcus species and determining the resistance genes. Materials and methods Clinical samples were cultured on BHI medium and enterococci were isolated by specific methods and antibiograms were prepared. DNA was derived from gentamicin-resistant species by alkaline lysis method and replicated by PCR method. Four gentamicin-resistant genes were evaluated by electrophoresis method on agarose gel. Results From 105 Enterococcus faecalis isolates, 36.2% and from 38 Enterococcus faecium isolates, 78.2% were resistant to gentamicin. 60% of these species bore aac (6’)- le – aph(2”)- la gene. ph(2”)- Ib,Ic,Id genes were not seen in any of the evaluated species. Conclusion In gentamicin-resistant species of E. faecalis and E. faecium, the aac (6’)- le – aph(2”)- la gene was identified as the main cause of resistance.

Antimicrobial-Resistant Enterococci in Animals and Meat: A Human Health Hazard?

Enterococcus faecium and Enterococcus faecalis belong to the gastrointestinal flora of humans and animals. Although normally regarded harmless commensals, enterococci may cause a range of different infections in humans, including urinary tract infections, sepsis, and endocarditis. The use of avoparcin, gentamicin, and virginiamycin for growth promotion and therapy in food animals has lead to the emergence of vancomycin- and gentamicin-resistant enterococci and quinupristin/dalfopristin-resistant E. faecium in animals and meat. This implies a potential risk for transfer of resistance genes or resistant bacteria from food animals to humans. The genes encoding resistance to vancomycin, gentamicin, and quinupristin/dalfopristin have been found in E. faecium of human and animal origin; meanwhile, certain clones of E. faecium are found more frequently in samples from human patients, while other clones predominate in certain animal species. This may suggest that antimicrobial-resistant E. faecium from animals could be regarded less hazardous to humans; however, due to their excellent ability to acquire and transfer resistance genes, E. faecium of animal origin may act as donors of antimicrobial resistance genes for other more virulent enterococci. For E. faecalis, the situation appears different, as similar clones of, for example, vancomycin- and gentamicin-resistant E. faecalis have been obtained from animals and from human patients. Continuous surveillance of antimicrobial resistance in enterococci from humans and animals is essential to follow trends and detect emerging resistance.

Porcine-Origin Gentamicin-ResistantEnterococcusfaecalisin Humans, Denmark

During 2001–2002, high-level gentamicin-resistant (HLGR) Enterococcus faecalis isolates were detected in 2 patients in Denmark who had infective endocarditis and in pigs and pork. Our results demonstrate that these isolates belong to the same clonal group, which suggests that pigs are a source of HLGR E. faecalis infection in humans.

Clonal groups of high-level gentamicin-resistantEnterococcus faeciumisolated from municipal wastewater and clinical samples in Tehran, Iran

Clonality among high-level gentamicin-resistant Enterococcus faecium (HLGR-EF) isolates obtained from clinical and sewage treatment plants (STP) were investigated using PhePlate system (PhP), ribotyping and pulsed-field gel electrophoresis (PFGE). During 1 year study (September 2005-2006), a total of 106 HLGR-EF isolates were collected from clinical (n = 48) and STP (n = 58) samples in Tehran, Iran. Biochemical fingerprinting of these isolates using the PhP showed the presence of 21 PhP types (diversity index, Di = 0.97) among the clinical and 21 PhP types (Di = 0.91) among the STP isolates. Representative isolates of each PhP type (n = 42) were further characterized by the ribotyping method. Sixteen ribotypes were identified among the isolates with five types shared between the clinical and STP isolates. PFGE recognized 24 clonal types among these isolates with three pulsotypes shared between the clinical and STP isolates. Combination of the two techniques (PFGE and ribotyping) resulted in 24 (Di = 0.96) and 16 (Di = 0.93) types among the strains isolated from clinical and STP samples, respectively. We concluded that the combination of PhP typing, ribotyping and PFGE could be extremely discriminatory when examining HLGR-EF isolates. The emergence of highly diverse HLGR-EF population in Iran is of serious concern especially because of their multi-resistances.

P28 Clonal diversity of high level gentamicin resistant Enterococcus faecalis isolated from clinical samples in Tehran, Iran

P28 Clonal diversity of high level gentamicin resistant Enterococcus faecalis isolated from clinical samples in Tehran, Iran

Persistent vancomycin and high-level gentamicin-resistant Enterococcus faecium bacteremia and intra-aortic thrombus in an extremely low birth-weight infant

Vancomycin-resistant Enterococcus (VRE) sepsis is emerging as a significant problem in the intensive care setting. The treatment at any age is challenging, but there is a dearth of information on this infection and its treatment in the very premature infant. We describe successful treatment of persistent bacteremia caused by Enterococcus faecium with vancomycin and high-level gentamicin resistance in a 10-day-old former 23-week premature male infant.

Clinical, epidemiological, and microbiological characteristics of bacteremia caused by high-level gentamicin-resistant Enterococcus faecalis

Enterococcus spp bacteremia is associated with high mortality and the appearance of high-level gentamicin resistance (HLGR) created additional challenges for the treatment of these infections. We evaluated the epidemiological and clinical characteristics of patients with bacteremias caused by HLGR and non_HLGR Enterococcus faecalis isolates at a teaching hospital in the State of São Paulo, Brazil. Patients with bacteremia due to E. faecalis diagnosed between January 1999 and December 2003 were included in the study. We collected clinical, epidemiological, and microbiological data from medical records. Banked isolates were typed using pulsed-field gel electrophoresis. We identified 145 cases of E. faecalis bacteremia: 66 (45.5%) were caused by HLGR isolates and 79 (54.5%) by non_HLGR. In the univariate analysis, patients with HLGR infection were older, had higher rates of bladder catheterization, and more often had treatment with cephalosporin, quinolone, and/or carbapenem compared with patients with non_HLGR infection (P < 0.05). Multivariate analysis indicated that older age, hematological malignancy, and previous use of vancomycin were independently associated with HLGR (P < 0.05). Mortality rates were not significantly different among patients with HLGR (50%) and non_HLGR (43%) infections (P = 0.40). Of the 32 genotyped isolates, 16 were distributed into 6 main electrophoresis patterns and 16 others had distinct patterns. E. faecalis bacteremia is associated with high mortality and is frequently caused by HLGR isolates at this teaching hospital. The variability among genotyped isolates suggests that endogenous infections, rather than patient-to-patient transmission of E. faecalis, are more common at this institution.

Polymorphism in pbp5 Gene Detected in Clinical Enterococcus faecium Strains with Different Ampicillin MICs from a Tunisian Hospital

The polymorphism in pbp5 gene was investigated in nine unrelated clinical gentamicin-resistant Enterococcus faecium strains with different minimal-inhibitory-concentration values for ampicillin (six ampicillin-resistant and three ampicillin-susceptible). Five alleles were detected when the pbp5 C-terminal region was analysed, two of them in the ampicillin-susceptible strains. Two of our high-ampicillin-resistant strains showed a new allele characterised by the Thr416Ala and Val462Ala substitutions. Two different alleles were identified when the pbp5 N-terminal region was studied; one of them in the unique strain (E. faecium 83) that presented very low ampicillin MIC (<0.125 μg/ml) and a nucleotidic mutation implicating a stop codon at 451 position. RT-PCR experiments carried out on five E. faecium strains belonging to each of the different pbp5 alleles (including E. faecium 83) gave positive results indicating the expression of this gene. Specific mutations in pbp5 gene could be responsible of the high MIC values of some of the E. faecium strains.