Antimicrobial Susceptibility Of Clinical Isolates Research Articles

Antimicrobial spectrum against wound pathogens and cytotoxicity of star-arranged poly-l-lysine-based antimicrobial peptide polymers.

Introduction. As growing numbers of patients are at higher risk of infection, novel topical broad-spectrum antimicrobials are urgently required for wound infection management. Robust pre-clinical studies should support the development of such novel antimicrobials.Gap statement. To date, evidence of robust investigation of the cytotoxicity and antimicrobial spectrum of activity of antimicrobial peptides (AMP)s is lacking in published literature. Using a more clinical lens, we address this gap in experimental approach, building on our experience with poly-l-lysine (PLL)-based AMP polymers.Aim. To evaluate the in vitro bactericidal activity and cytotoxicity of a PLL-based 16-armed star AMP polymer, designated 16-PLL10, as a novel candidate antimicrobial.Methods. Antimicrobial susceptibilities of clinical isolates and reference strains of ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) pathogens, to 16-PLL10 were investigated. Human erythrocyte haemolysis and keratinocyte viability assays were used to assess toxicity. Modifications were made to 16-PLL10 and re-evaluated for improvement.Results. Minimum bactericidal concentration of 16-PLL10 ranged from 1.25 µM to ≥25 µM. At 2.5 µM, 16-PLL10 was broadly bactericidal against ESKAPE strains/wound isolates. Log-reduction in colony forming units (c.f.u.) per millilitre after 1 h, ranged from 0.3 (E. cloacae) to 5.6 (K. pneumoniae). At bactericidal concentrations, 16-PLL10 was toxic to human keratinocyte and erythrocytes. Conjugates of 16-PLL10, Trifluoroacetylated (TFA)-16-PLL10, and Poly-ethylene glycol (PEG)ylated 16-PLL10, synthesised to address toxicity, only moderately reduced cytotoxicity and haemolysis.Conclusions. Due to poor selectivity indices, further development of 16-PLL10 is unlikely warranted. However, considering the unmet need for novel topical antimicrobials, the ease of AMP polymer synthesises/modification is attractive. To support more rational development, prioritising clinically relevant pathogens and human cells, to establish selective toxicity profiles in vitro, is critical. Further characterisation and discovery utilising artificial intelligence and computational screening approaches can accelerate future AMP nanomaterial development.

In vitro antimicrobial susceptibility of clinical isolates from adult and paediatric patients in Jordan: Antimicrobial Testing Leadership and Surveillance (ATLAS) 2010–2021

ObjectivesTo evaluate the in vitro antimicrobial susceptibilities of Gram-positive and Gram-negative isolates from patients in Jordan between 2010 and 2021, through the Antimicrobial Testing Leadership and Surveillance (ATLAS) programme.MethodsMedical centres in Jordan collected bacterial isolates from hospitalised patients with defined infection sources between 2010 and 2021 (no isolates collected in 2014). Antimicrobial susceptibility was interpreted using CLSI standards. FDA-approved breakpoints were applied for tigecycline. The identification of β-lactamase genes was performed for a proportion of isolates using multiplex PCR assays.ResultsMore than 92% of Acinetobacter baumannii collected were multidrug-resistant (MDR) and/or carbapenem-resistant (CR), and > 50% susceptibility was reported only to minocycline (62.2% among both MDR and CR isolates). Rates of MDR and CR Pseudomonas aeruginosa were 14.3% and 20.5%, respectively, and among all P. aeruginosa collected from adults, susceptibility to ceftazidime/avibactam was 95.3% and to ceftolozane/tazobactam was 88.4%. For Escherichia coli from adults and MDR E. coli, susceptibility to ceftazidime/avibactam, ceftolozane/tazobactam, imipenem, meropenem and meropenem/vaborbactam was 92.1%–98.7%. Susceptibility to tigecycline was > 94% among Klebsiella pneumoniae from adult, paediatric, and ICU patients (all ages). CTX-M-15 was the most frequently identified β-lactamase gene among E. coli and K. pneumoniae. Susceptibility to most antimicrobial agents was < 50% among K. pneumoniae carrying CTX-M-15, CTX-M-9-type, NDM-5, and/or OXA-48 β-lactamase genes. All S. aureus collected were susceptible to teicoplanin, vancomycin, daptomycin, linezolid and tigecycline, with 96.1% of S. aureus from adults were susceptible to ceftaroline. Overall, 58.8% of Staphylococcus aureus were MRSA.ConclusionThis study provides valuable information regarding antimicrobial susceptibility in Jordan between 2010 and 2021. Continued monitoring of in vitro antimicrobial susceptibility is critical in the fight against antimicrobial resistance.

Molecular Identification of Prevalent Streptococcus Pyogenes Serogroup Associated with Respiratory Tract Infections in Children

The current study intends to characterize the respiratory tract infections that have an association with gram positive bacterial pathogens, emm typing, the pattern of antibacterial resistance in isolated pathogens, phenotyping of virulence factor and molecular detection of Macrolide resistance gene. Various samples from patients with respiratory tract infections were collected and identification and antimicrobial susceptibility of clinical isolates was performed as per standard laboratory procedure. Macrolides (Eruthromycin, Clindamycin)-resistant isolates were again subjected to MIC method. Macrolide-inducible resistance to clindamycin (D test) was conducted upon Erythromycin and Clindamycin discs. Multiplex PCR was used to detect the resistance genes in all the three types of macrolide resistance strains. Serum Opacity Factor (SOF) was detected for all the isolates of GAS. Every isolate was checked to produce biofilm through micro titre plate method. Bacterial growth got registered in 156 (36.28%) samples. The most common isolate from URI samples was GAS i.e., 64 (14.9%), only to be followed by GGS 38(8.8%), GCS 29 (6.7%) and Staphylococcus aureus 18 (4.2%). Among GAS, only one isolate was recorded from blood, whereas 8.50% from sputum and the rest. All 71 GAS isolates were found to exhibit sensitivity towards Penicillin and Ceftriazone. GAS exhibited 55% Mtype of resistance whereas 40% were resistant to cMLS and 5% to iMLS. GCS showcased an equal number of cMLS and M type too. GGS portrayed 54.54% resistance to cMLS followed by 36.36% to Mtype and 9.09% to iMLS. The current study found iMLS type with least resistance. The current study identified that Streptococcus pyogenes is the most common bacteria that cause and recur the infection. The prevalence of resistance tends to change geographically and periodically. For this purpose and to achieve a sound public health outcome, periodical screening of antibiotic-resistance pattern becomes inevitable.

Antimicrobial Susceptibility of Clinical Isolates of Candida Species to Ethanolic Extracts of Ziziphus Abyssinica Leaves

Pectinases are the group of enzymes that catalyzes the degradation of pectic substances. Pectinase are enzymes that are remarkably employed in most industries because they have a large variety of applications, such as increasing juice extraction by decreasing the viscosity of concentrates in cellulose fibre preparation, coffee/tea fermentation and also for the clarification of juices and wines. This research was carried out for pectinase production by Aspergillus niger AR2 using local orange peel as substrate. Aspergillus niger was isolated from spoiled orange fruit and identified using phenotypic and molecular techniques. The isolate was screened for pectinase production on pectin agar. Fermentation was carried out by Aspergillus niger AR2 at fermentation days 3, 4 and 5; the amount of substrate (15g), pH (5), temperature (300C) and inoculum density of 106 (spore/mL). After fermentation, crude pectinase was extracted for enzyme assay. Enzyme activity was measured based on the amount of D-galacturonic acid released by the crude enzyme. Pectinase produced was used for orange juice extraction from mashed oranges and compared with juice with no enzymes. The results have shown that maximum pectinase production by A. nigerAR2 was found to be at a temperature of 300C, inoculum density of 106 (spore/mL), pH 5 at day 5 using orange peels as substrate with an activity of 3.04±0.024 (U/ml). The result shows that the pectinase produced was effective in orange juice extraction from mashed oranges due to the increase in the volume of orange juice.

Prevalence and antibiotic susceptibility trends of periodontal pathogens in the subgingival microbiota of German periodontitis patients: A retrospective surveillance study.

This retrospective surveillance study aimed to follow periodontitis-associated bacterial profiles and to identify time-dependent changes in antibiotic susceptibility patterns. From 2008 to 2015, bacterial specimen from deep periodontal pockets were collected from a total of 7804 German adults diagnosed with periodontitis. Presence of selected bacteria was confirmed by anaerobic culture and nucleic acid amplification. Antimicrobial susceptibility of clinical isolates was tested by disc diffusion with antibiotics used for the treatment of periodontitis and oral infections. The prevalences of periodontal pathogens were calculated and temporal evolution of antimicrobial susceptibility towards amoxicillin, amoxicillin/clavulanic acid, metronidazole, doxycycline, clindamycin, azithromycin, ciprofloxacin and ampicillin was analysed with logistic regression. The prevalence of patients harbouring bacteria was 95.9% Fusobacterium nucleatum, 88.0% Tannerella forsythia, 76.4% Treponema denticola, 76.5%, Campylobacter rectus, 76.0% Eikenella corrodens, 75.0% Capnocytophaga spp., 68.2% Porphyromonas gingivalis, 57.7% Peptostreptococcus micros, 43.1% Prevotella intermedia, 30.4% Eubacterium nodatum and 21.5% Aggregatibacter actinomycetemcomitans. In 63.5% of patients, one or more isolates were not susceptible to at least one of the antibiotics tested. The data further revealed a trend towards decreasing susceptibility profiles (p < 0.05) with antibiotic non-susceptibilities in 37% of patients in 2008 and in 70% in 2015. The present study confirmed a high prevalence of periodontal pathogens in the subgingival microbiota of German periodontitis patients. The data revealed an incremental increase in isolates displaying resistance to some antibiotics but no relevant change in susceptibility to amoxicillin and metronidazole.

Carbapenemase Producers Among Extensive Drug-Resistant Gram-Negative Pathogens Recovered from Febrile Neutrophilic Patients in Egypt.

PurposeThis study aimed to detect the prevalence of carbapenemase producers (CPs) among extensive drug-resistant (XDR)-carbapenemase producing Gram-negative bacteria (GNB) recovered from various clinical specimens of hospitalized neutrophilic febrile patients in two major tertiary care hospitals in Egypt.MethodsStandard methods were used to evaluate the antimicrobial susceptibility of clinical isolates according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Phenotypic and genotypic analysis of CPs were carried out and statistically analyzed using standard methods.ResultsThree hundred and forty-two GNB were obtained from 342 clinical specimens during the period of the study, where 162 (47%) were enterobacterial isolates, including, 63 (18.4%) Escherichia coli, 87 (25.4%) Klebsiella spp., 5 (1.46%) Enterobacter cloacae, 5 (1.46%) Salmonella spp. and 2 (0.6%) Proteus and 180 (53%) were non-fermentative bacilli including, 129 (37.7%), Acinetobacter baumannii, and 51 (14.9%), Pseudomonas spp. Out of the 342 GNB, 188 (54.9%) isolates were multi-drug resistant (MDR). Of these, 52 (27.6%) were XDR as well as CPs as confirmed phenotypically. The MIC of imipenem against the XDR GNB against showed either low (11 isolates; 21.1%; MIC range =4–32 µg/mL) or high levels of resistance (41 isolates; 78.8%; MIC range = 64-≥1024). The most prevalent carbapenem resistance (CR) genes were blaKPC (63.5%) followed by blaOXA-48 (55.7%) and blaVIM (28.8%). No significant association could be observed between the MIC level and the presence of CR genes (P value >0.05).ConclusionHigh prevalence of MDR (54.9%) and XDR (27.6%) GNB pathogens associated with high levels of resistance to carbapenems were observed. All XDR GNB were CPs and tested positive for at least one of the CR genes. However, most of them (78.8%) showed a high level of CR (MIC range = 64-≥1024) with no significant association with the CR genes.

Antimicrobial susceptibility and molecular characteristics of Mycoplasma pneumoniae isolates across different regions of China

BackgroundIn China mainland, most Mycoplasma pneumoniae related studies are carried out in Beijing and Shanghai, while rare studies are performed in the other regions. In this study, we analyzed the molecular biology characteristics and antimicrobial susceptibility of clinical isolates of M. pneumoniae from 5 regions between January 2017 and December 2018.MethodsGenotyping was performed to 154 M. pneumoniae isolates from 5 cities using PCR and multiple-locus variable-number tandem repeat analysis (MLVA) method. Antimicrobial susceptibility test was performed to all the isolates against 4 antibiotics. Sequencing was performed to the amplification products of the 23S rRNA drug resistant gene.ResultsGenotype I was detected in 118 M. pneumoniae isolates (76.6%), and genotype II was identified in 36 isolates (23.4%). The majority (92.2%) of the MLVA genotypes were 4–5–7-2 and 3–5–6-2, which represented the genotype I and II, respectively. The total macrolide (ML) resistance rate was 79.7%. The minimum inhibitory concentration (MIC) of the erythromycin was in a range of 128- > 256 μg/ml, while that for the azithromycin was 2-32 μg/ml. There were mutations in the 23S rRNA in each ML resistance isolate. Jilin city showed the highest prevalence of genotype I (100%) and ML resistance rate (100%), while Jinan showed the lowest prevalence of genotype I (45.5%) and ML resistance rate (54.5%).ConclusionsA large variance was identified in the M. pneumoniae genotype and ML resistance among the 5 cities. The proportion of M. pneumoniae with a genotype II genotype (3–5–6-2) showed an increased trend.

Fast and reliable determination of Escherichia coli susceptibility to antibiotics: Infrared microscopy in tandem with machine learning algorithms.

Antimicrobial drugs have an important role in controlling bacterial infectious diseases. However, the increasing resistance of bacteria to antibiotics has become a global health care problem. Rapid determination of antimicrobial susceptibility of clinical isolates is often crucial for the optimal antimicrobial therapy. The conventional methods used in medical centers for susceptibility testing are time-consuming (>2 days). Two bacterial culture steps are needed, the first is used to grow the bacteria from urine on agar plates to determine the species of the bacteria (~24 hours). The second culture is used to determine the susceptibility by growing colonies from the first culture for another 24 hours. Here, the main goal is to examine the potential of infrared microscopy combined with multivariate analysis, to reduce the time it takes to identify Escherichia coli susceptibility to antibiotics and to determine the optimum choice of antibiotic to which the bacteria will respond. E coli colonies of the first culture from patients with urinary tract infections (UTI) were examined for the bacterial susceptibility using Fourier-transform infrared (FTIR). Our results show that it is possible to determine the optimum choice of antibiotic with better than 89% sensitivity, in the time span of few minutes, following the first culture.

Antimicrobial susceptibilities of clinical isolates of the anaerobic bacteria which can cause aspiration pneumonia

Aspiration pneumonia is an infectious disease of the lungs caused by inhalation of saliva or foods, associated with swallowing dysfunction. Therefore, the major causative organisms are oral or gastric bacteria. In this study, we evaluated the antimicrobial susceptibility patterns of the anaerobic bacteria which can cause aspiration pneumonia, Fusobacterium spp., Finegoldia magna, Bacteroides fragilis, Peptostreptococcus spp., Prevotella spp., and Streptococcus milleri group to ceftriaxone, cefmetazole, flomoxef, ampicillin/sulbactam, and ampicillin. We also tested the β-lactamase activities of each of the bacterial strains. Fusobacterium spp. and Finegoldia magna were susceptible to all of the tested antimicrobial drugs, except ampicillin, and showed no β-lactamase activity. The Streptococcus milleri group, Bacteroides fragilis, and Peptostreptococcus spp. showed decreased susceptibility to cefmetazole or flomoxef as compared to the susceptibility levels documented in a previous report. There was one strain of Peptostreptococcus anaerobius which was not susceptible to ampicillin/sulbactam, but also showed no β-lactamase activity, suggesting that this strain harbored a mechanism of resistance other than the production of β-lactamase. The susceptibility of Prevotella spp. to ceftriaxone was also decreased as compared to the susceptibility level documented in a previous report. Furthermore, β-lactamase-positive strains were found even among ceftriaxone-susceptible strains. Elderly persons with swallowing dysfunction carry a risk of recurrent episodes of aspiration pneumonia and repeated use of antibiotics increases the risk of development of antibiotic resistance. In the present study, the antibiotic susceptibilities of some of organisms which can cause aspiration pneumonia were found to be decreased as compared to the susceptibility levels documented in a previous report. Therefore, surveillance of the antimicrobial susceptibility patterns of these bacteria is recommended to prevent the development of resistance.

Antimicrobial susceptibility of clinical isolates of Campylobacter jejuni from New South Wales, Australia.

The aim of this study was to investigate the prevalence of resistance to commonly used antimicrobials in Campylobacter jejuni isolates from clinical faecal samples in New South Wales (NSW), Australia. A total of 117 C. jejuni isolates from human faecal samples from regional and metropolitan NSW were examined for antimicrobial resistance. Of the 117 isolates tested, 15.4% were resistant to ampicillin, 5.1% to tetracycline and 13.7% to ciprofloxacin. Most of the isolates were susceptible to erythromycin, except for three that showed intermediate resistance. Furthermore, 9.4% of isolates were resistant (or intermediate-resistant) to more than one antimicrobial agent. Isolates that were resistant to ampicillin and tetracycline harboured the blaOXA-61 and tet(O) genes, respectively. A mutation in the gyrA gene, resulting in the T86I substitution, was identified in the majority of ciprofloxacin-resistant isolates. The data obtained in the current study demonstrate that the majority of C. jejuni isolates evaluated were susceptible to one or more antimicrobials tested. Apart from three isolates that demonstrated intermediate resistance, all of the isolates were susceptible to erythromycin, which is the drug of choice for treating Campylobacter infections.

A multicenter survey of antimicrobial susceptibility of Prevotella species as determined by Etest methodology

Knowledge about the antimicrobial susceptibility patterns of different Prevotella species is limited. The aim of this study was to determine the current antimicrobial susceptibility of clinical isolates of Prevotella species from different parts of Europe, Kuwait and Turkey. Activity of 12 antimicrobials against 508 Prevotella isolates, representing 19 species, were tested according to Etest methodology. EUCAST, CLSI and FDA guidelines were used for susceptibility interpretations. All Prevotella species were susceptible to piperacillin/tazobactam, imipenem, meropenem, tigecycline and metronidazole. Ampicillin/sulbactam and cefoxitin also showed good activity. Ampicillin, clindamycin, tetracycline and moxifloxacin were less active; 51.2%, 33.7%, 36.8% and 18.3% of isolates were non-susceptible, respectively. A total of 49 (9.6%) isolates were resistant to three or more antimicrobials. Prevotella bivia was the most prevalent species (n = 118) and accounted for most of the multidrug-resistant isolates. In conclusion, the level of non-susceptibility to antimicrobials, which may be used for treatment of infections involving Prevotella species, are a cause of concern. This data emphasizes the need for species level identification of clinical Prevotella isolates and periodic monitoring of their susceptibility to guide empirical treatment.

Antimicrobial susceptibility of clinical isolates of Neisseria gonorrhoeae to alternative antimicrobials with therapeutic potential.

The prevalence of MDR Neisseria gonorrhoeae is increasing globally and represents a public health emergency. Development and approval of new anti-gonococcal agents may take years. As a concurrent approach to developing new antimicrobials, the laboratory and clinical evaluation of currently licensed antimicrobials not widely used for the treatment of gonorrhoea may provide new options for the treatment of gonococcal infections. To determine the in vitro activity of nine alternative, currently licensed and late-development antimicrobials with the potential to treat gonococcal infections against 112 clinical isolates of N. gonorrhoeae resistant to one or multiple antimicrobials. The MICs of conventional anti-gonococcal antimicrobials (penicillin, ceftriaxone, cefixime, azithromycin, ciprofloxacin, tetracycline and spectinomycin) and alternative antimicrobials (ertapenem, gentamicin, netilmicin, tigecycline, eravacycline, fosfomycin, linezolid, ceftazidime/avibactam and ceftaroline) were determined by agar dilution. Ertapenem and the novel cephalosporins demonstrated similar MIC values to the third-generation cephalosporins, but increased MICs were observed for isolates with increased cefixime and ceftriaxone MICs. Tigecycline and eravacycline had MIC values below expected serum concentrations for all isolates tested. The aminoglycosides gentamicin and netilmicin were generally more potent than spectinomycin, with netilmicin demonstrating the greatest potency. Fosfomycin MICs were elevated compared with other agents, but remained within the MIC range for susceptible organisms, while linezolid MICs were generally higher than those for organisms considered resistant. Among potentially therapeutically useful alternative agents, the aminoglycosides, eravacycline, tigecycline and fosfomycin had good in vitro activity. The novel cephalosporins and ertapenem had comparable activity to cefixime and ceftriaxone.

Antimicrobial susceptibility of clinical isolates of Actinomyces and related genera reveals an unusual clindamycin resistance among Actinomyces urogenitalis strains.

Patterns of antimicrobial susceptibility in Actinomyces and related genera are very limited in the literature. Data of predominant susceptibility profiles could contribute to the establishment of an accurate empirical treatment. A total of 113 isolates from clinical samples were included in this study. Each isolate was identified using phenotypic methods and MALDI-TOF/MS. When discrepancies were observed, 16S rRNA gene sequencing was performed. The minimum inhibitory concentrations (MICs) of nine antimicrobial agents (penicillin, ceftriaxone, linezolid, tetracycline, clindamycin, erythromycin, ciprofloxacin, levofloxacin and vancomycin) were tested against the species Actinotignum schaalii (n=23), Actinomyces turicensis (n=18), Actinomyces europaeus (n=13), Actinomyces naeslundii/Actinomyces viscosus group (n=12), Actinomyces urogenitalis (n=11), Actinomyces radingae (n=11), Actinomyces neuii (n=9), Actinomyces odontolyticus (n=8), Bifidobacterium scardovii (n=3), Actinomyces graevenitzii (n=2), Alloscardovia omnicolens (n=2) and Varibaculum cambriense (n=1). All of the isolates were susceptible to penicillin, ceftriaxone, vancomycin and linezolid. Almost all of the A. urogenitalis isolates (8/11) were resistant to clindamycin and showed susceptibility to erythromycin, suggesting an L-phenotype, however no determinants of clindamycin resistance (lnu and lsa genes) were detected by PCR. High MIC values to quinolones were observed in 54/113 isolates (47.8%). All of the A. urogenitalis isolates were highly resistant to ciprofloxacin and levofloxacin. These data highlight the importance of ongoing surveillance to provide relevant information for empirical management of infections caused by these organisms.

Relative Prevalence and Antimicrobial Susceptibility of Clinical Isolates of Elizabethkingia Species Based on 16S rRNA Gene Sequencing.

Some of the previously reported clinical isolates of Elizabethkingia meningoseptica may be later named species of Elizabethkingia We determined the accuracy of species identification (with two matrix-assisted laser desorption ionization-time of flight mass spectrometry [MALDI-TOF MS] systems and the Vitek 2 GN card), relative prevalence of three Elizabethkingia spp. in clinical specimens, and antimicrobial susceptibility of the species identified by 16S rRNA gene sequencing. Specimens for culture were collected from patients in a university hospital in Seoul, South Korea, between 2009 and 2015. All 3 Elizabethkingia spp. were detected in patients; among the 86 isolates identified by 16S rRNA gene sequencing, 17 (19.8%) were E. meningoseptica, 18 (20.9%) were Elizabethkingia miricola, and 51 (59.3%) were Elizabethkingia anophelis Only the MALDI-TOF Vitek MS system with an amended database correctly identified all of the isolates. The majority (76.7%) of the isolates were from the lower respiratory tract, and 8 (9.3%) were from blood. Over 90% of E. meningoseptica and E. anophelis isolates were susceptible to piperacillin-tazobactam and rifampin. In contrast, all E. miricola isolates were susceptible to fluoroquinolones except ciprofloxacin. Further studies are urgently needed to determine the optimal antimicrobial agents for the treatment of infections due to each individual Elizabethkingia species.

Clinical and Diagnostic Aspects of Brucellosis and Antimicrobial Susceptibility of Brucella Isolates in Hamedan, Iran.

Current drug regimens for brucellosis are associated with relatively high rates of therapeutic failure or relapse. Reduced antimicrobial susceptibility of Brucella spp. has been proposed recently as a potential cause of therapeutic failure. The aim of this study was to evaluate the antibiotic resistance pattern of Brucella melitensis clinical isolates by E-test method in Hamadan, west of Iran. In a 15-month period, all patients with suspected brucellosis were enrolled. Blood specimens were collected for diagnosis of brucellosis by BACTEC system and serological tests. Antimicrobial susceptibility of clinical isolates to 7 antibiotics was assessed by the E-test method. One hundred forty-nine patients with brucellosis were evaluated. 38.3% of cultures of clinical samples were positive for BACTEC system, of which 91.2% were associated with a positive serological test result. No significant associations were found between serology and the culture method. All Brucella isolates were susceptible to doxycycline, streptomycin, gentamicin, ciprofloxacin, and moxifloxacin. However, decreased sensitivity to rifampin and trimethoprim-sulfamethoxazole was found in 35.1% and 3.5% of isolates, respectively. Because of the high rates of intermediate sensitivity to rifampin among Brucella isolates, this drug should be prescribed with caution. We recommend restricting the use of rifampin for treatment of brucellosis except as an alternative drug for special situations.

Microbiological and Clinical Effects of Sitafloxacin and Azithromycin in Periodontitis Patients Receiving Supportive Periodontal Therapy.

Sitafloxacin (STFX) is a newly developed quinolone that has robust antimicrobial activity against periodontopathic bacteria. We previously reported that oral administration of STFX during supportive periodontal therapy was as effective as conventional mechanical debridement under local anesthesia microbiologically and clinically for 3 months. The aim of the present study was to examine the short-term and long-term microbiological and clinical effects of systemic STFX and azithromycin (AZM) on active periodontal pockets during supportive periodontal therapy. Fifty-one patients receiving supportive periodontal therapy were randomly allocated to the STFX group (200 mg/day of STFX for 5 days) or the AZM group (500 mg/day of AZM for 3 days). The microbiological and clinical parameters were examined until 12 months after the systemic administration of each drug. The concentration of each drug in periodontal pockets and the antimicrobial susceptibility of clinical isolates were also analyzed. The proportions of red complex bacteria, i.e., Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia, which are the representative periodontopathic bacteria, were significantly reduced at 1 month and remained lower at 12 months than those at baseline in both the STFX and AZM groups. Clinical parameters were significantly improved over the 12-month period in both groups. An increase in the MIC of AZM against clinical isolates was observed in the AZM group. These results indicate that monotherapy with systemic STFX and AZM might be an alternative treatment during supportive periodontal therapy in patients for whom invasive mechanical treatment is inappropriate. (This study has been registered with the University Hospital Medical Information Network-Clinical Trials Registry [UMIN-CTR] under registration number UMIN000007834.).

Antimicrobial susceptibility of clinical isolates of Bacteroides fragilis group organisms recovered from 2009 to 2012 in a Korean hospital.

BackgroundPeriodic monitoring of antimicrobial resistance trends of clinically important anaerobic bacteria such as Bacteroides fragilis group organisms is required. We determined the antimicrobial susceptibilities of clinical isolates of B. fragilis group organisms recovered from 2009 to 2012 in a tertiary-care hospital in Korea.MethodsA total of 180 nonduplicate clinical isolates of B. fragilis group organisms were collected in a tertiary care hospital. The species were identified by conventional methods: the ATB 32A rapid identification system (bioMérieux, France) and the Vitek MS matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (bioMérieux). Antimicrobial susceptibility was determined by the CLSI agar dilution method.ResultsImipenem and meropenem resistance rates were 0-6% for B. fragilis group isolates. The rate of resistance to piperacillin-tazobactam was 2% for B. fragilis and 0% for other Bacteroides species, but 17% for B. thetaiotaomicron isolates. High resistance rates to piperacillin (72% and 69%), cefotetan (89% and 58%), and clindamycin (83% and 69%) were observed for B. thetaiotaomicron and other Bacteroides spp. The moxifloxacin resistance rate was 27% for other Bacteroides spp. The MIC50 and MIC90 of tigecycline were 2-4 µg/mL and 8-16 µg/mL, respectively. No isolates were resistant to chloramphenicol or metronidazole.ConclusionsImipenem, meropenem, chloramphenicol, and metronidazole remain active against B. fragilis group isolates. Moxifloxacin and tigecycline resistance rates are 2-27% and 8-15% for B. fragilis group isolates, respectively.

English

BACKGROUND: Enterococci have emerged as the second most common cause of nosocomial infections over the past 2-3 decades and antibiotic resistance is a major obstacle for treatment. Identification of enterococci to species level is helpful and crucial for proper patient treatment, epidemiologic and infection control purposes. The emergence of vancomycin resistant enterococci is of particular concern as it has limited the therapeutic options available for the clinicians. AIM: To speculate and determine the antimicrobial susceptibility of clinical isolates of enterococci with special reference to vancomycin. SETTINGS AND DESIGN: A prospective descriptive study was carried out in Rajarajeswari medical college and hospital, Bangalore. MATERIAL AND METHODS: The study included a total of 90 clinical isolates of enterococcus from urine, pus, blood and endotracheal aspirates over a period of one year from November 2012 to October 2013. The isolates were confirmed to belong to genus Enterococcus and speciation was based on potassium tellurite (0.04 %) reduction, arginine deamination and fermentation of arabinose, mannitol, raffinose, and sorbitol. Antimicrobial susceptibility was determined by Kirby Bauer disk diffusion and MIC of vancomycin was determined by agar dilution method according to CLSI guidelines. STATISTICAL ANALYSIS: p value was calculated by Fisher’s exact test. RESULTS: Amongst the total 90 Enterococcal isolates, 76 isolates (84.5 %) were Enterococcus faecalis, 13 isolates (14.4 %) were Enterococcus faecium and 1 isolate (1.1 %) was Enterococcus raffinosus. Out of the 90 isolates, 65 (72.2 %) were from urine, 15 (16.6 %) from pus, 5 (5.6 %) from blood and 5 (5.6 %) from endotracheal aspirates. High level gentamicin resistance was 22.4 % for E. faecalis and 30.8 % for E. faecium by Kirby Bauer disc diffusion method. Occurrence of vancomycin resistant enterococci (VRE) in our setting is 2.2 %. Isolates had 100 % sensitivity to linezolid. CONCLUSION: Enterococcus faecalis was the most common species. Maximum isolates were from urine samples. Higher level of gentamicin resistance could lead to failure of synergistic therapy. Speciation and regular monitoring for antibiotic resistance with special attention to vancomycin and high level aminoglycosides is warranted.

Culture and molecular analysis of Enterococcus faecalis and antimicrobial susceptibility of clinical isolates from patients with failure endodontic treatment

Objective: The aim of this study was to evaluate the minimal inhibitory concentrations (MIC) of different antibiotic agents against to the most prevalent microorganism found in root-filled canals by culture and molecular approaches. Material and Methods: The microbial samples were taken either from thirty root-filled canals after removal of gutta-percha. Culture methods and 16s rDNA assay were used to identify the E faecails present in the samples. The antimicrobial susceptibilities of the isolates of E faecalis were determined by MIC values using the E test System and interpreted according to the Clinical and Laboratory Standards Institute guidelines. The following antibiotics were used: benzylpenicillin, amoxicillin, amoxicillin-clavulanic acid, erythromycin, azithromycin, vancomycin, chloramphenicol, tetracycline, doxycycline, ciprofloxacin, rifampicin and moxifloxacin. Results: E faecalis were isolated (7/30) and detected (13/30) by culture and PCR assay, respectively. All tested E faecalis (n=12) were highly sensitive to amoxicillin, moxifloxacin, vancomycin, benzylpenicillin and amoxicillin-clavulanic acid. Some antibiotics were resistant against E faecalis strains such as rifampicin (4/12), tetracycline (2/12), doxycycline (1/12), erythromycin (3/12) and azythromycin (8/12). Conclusion: Amoxicillin, amoxicillin-clavulanic acid, benzylpenicillin, vancomycin and moxifloxacin were the most active antibiotics, in vitro, against E faecalis clinical strains, with all the isolates being susceptible. Azithromycin and erythromycin were least effective, with none percentage of isolates being susceptible, during laboratory testing. Moreover, E faecalis were identified more frequently by PCR assay than by culture technique.Keywords: Retreatment; Antibiotics, antimicrobial susceptibility; Enterococcus faecalis; Antibiotic resistance.

Antimicrobial susceptibility of clinical isolates of anaerobic bacteria in Ontario, 2010–2011

The local epidemiology of antimicrobial susceptibility patterns in anaerobic bacteria is important in guiding the empiric treatment of infections. However, susceptibility data are very limited on anaerobic organisms, particularly among non-Bacteroides organisms. To determine susceptibility profiles of clinically-significant anaerobic bacteria in Ontario Canada, anaerobic isolates from sterile sites submitted to Public Health Ontario Laboratory (PHOL) for identification and susceptibility testing were included in this study. Using the E-test method, isolates were tested for various antimicrobials including, penicillin, cefoxitin, clindamycin, meropenem, piperacillin-tazobactam and metronidazole. The MIC results were interpreted based on guidelines published by Clinical and Laboratory Standards Institute. Of 2527 anaerobic isolates submitted to PHOL, 1412 were either from sterile sites or bronchial lavage, and underwent susceptibility testing. Among Bacteroides fragilis, 98.2%, 24.7%, 1.6%, and 1.2% were resistant to penicillin, clindamycin, piperacillin-tazobactam, and metronidazole, respectively. Clostridium perfringens was universally susceptible to penicillin, piperacillin-tazobactam, and meropenem, whereas 14.2% of other Clostridium spp. were resistant to penicillin. Among Gram-positive anaerobes, Actinomyces spp., Parvimonas micra and Propionibacterium spp. were universally susceptible to β-lactams. Eggerthella spp., Collinsella spp., and Eubacterium spp. showed variable resistance to penicillin. Among Gram-negative anaerobes, Fusobacterium spp., Prevotella spp., and Veillonella spp. showed high resistance to penicillin but were universally susceptible to meropenem and piperacillin-tazobactam. The detection of metronidazole resistant B. fragilis is concerning as occurrence of these isolates is extremely rare. These data highlight the importance of ongoing surveillance to provide clinically relevant information to clinicians for empiric management of infections caused by anaerobic organisms.