Gram-positive Bacterial Isolates Research Articles

The Susceptibility of Bacterial Endophthalmitis Isolates to Vancomycin, Ceftazidime, and Amikacin: A 23-Year Review

To investigate the in vitro susceptibility of Gram-positive and Gram-negative endophthalmitis bacterial isolates to vancomycin, amikacin, and ceftazidime over a 23-year period. Retrospective non-comparative laboratory case series. Endophthalmitis patients that were culture positive for bacteria. Laboratory records of bacteria isolated from endophthalmitis specimens collected from January 1st 1993 to December 31st 2015 were reviewed for incidence and standard susceptibility testing. The in vitro susceptibilities of bacteria cultured from endophthalmitis to vancomycin (VAN), amikacin (AMK), and ceftazidime (CEF). Patients with endophthalmitis were culture positive for bacteria in 665 cases.. Coagulase negative Staphylococci (CoNS) were the most common bacteria (54.6%), followed by Streptococci (Strep) species (20.8%), Staphylococcus aureus (SA) (10.2%), other Gram-positive (other-GP) bacteria (7.4%) and Gram-negative (GN) bacteria (7.1%). All Gram-positive organisms were susceptible to VAN, with the exception of 2 isolates. The in vitro susceptibilities of bacteria to AMK were: CoNS (95.3%), SA (75.0%), Strep (8.0%), GN (95.7%), and other-GP (81.1%). The in vitro susceptibilities of bacteria to CEF were: CoNS (58.5%), SA (54.4%), Strep (84.1%), GN (93.6.%), and other-GP (52.8%). There was no difference between AMK (95.7%) and CEF (93.6%) for GN coverage. AMK provided better coverage than CEF for CoNS, SA, and other-GP bacteria respectively (p<0.05, Fisher's exact), however, CEF appeared to provide better coverage (p<0.001, Fisher's exact) for Strep than AMK. Based on standard in vitro susceptibility testing, vancomycin remains an optimal antibiotic choice for the treatment of Gram-positive endophthalmitis. AMK and CEF appear to provide equal GN coverage, but AMK appears to provide better coverage for CoNS, SA, and other-GP, but not Strep.

Prevalence of methicillin-resistant &lt;i&gt;Staphylococcus aureus&lt;/i&gt; and extended spectrum β–lactamase producers among bacteria isolated from infected wounds in a tertiary hospital in Ibadan City

Wound colonization by microorganisms is most frequently polymicrobial and incidences of high level resistance among bacterial isolates from wounds have been reported. Methicillin-resistant Staphylococcus aureus (MRSA) and extendedspectrum beta-lactamase (ESBL) producing Gram-negative bacteria both constitute serious challenge to physician in their choice of antibiotic treatment of infections caused by these bacteria. This study determined the antibiotic susceptibility profiles and prevalence of MRSA and ESBL producers among wound bacterial isolates from a tertiary hospital in Ibadan City. Forty (40) clinical bacterial isolates from five wound sources were collected from the Microbiology unit of the University College Hospital (UCH), Ibadan and were authenticated with standard bacteriological techniques. Antibiotic susceptibility test was done by disc-diffusion method using 19 antibiotics belonging to 12 classes. MRSA strains were detected by their resistance to cefoxitin and/or oxacillin antibiotics. Presumptive ESBL production was by double-disc synergy test using 30 μg cefotaxime and ceftazidime around 20/10 μg amoxicillin-clavulanic acid discs. ESBL confirmation was by minimum inhibitory concentration (MIC) using agar-dilution method. The authenticated isolates include Proteus spp (47.5%), Staphylococcus aureus (27.5%), Pseudomonas aeruginosa (12.5%), Klebsiella spp (7.5%), Acinetobacter baumanii (2.5%) and E. coli (2.5%). Distribution of the isolates collected according to wound sources includes: acute soft tissue wounds (35%), leg ulcer (32.5%), surgical wounds (17.5%), burn wounds (12.5%) and diabetic foot ulcer (2.5%). Distributions according to patients’ gender are: male (65%), female (35%), and according to age-groups are: 0 – 19 years (22.5%), 20 – 39 years (35%), 40 – 59 years (32.5%) and ≥ 60 years (10%). All (100%) the isolates were multidrug resistant (MDR) being resistant to ≥ 3 classes of antibiotics. Percentages of isolates resistance to each of the antibiotic include: piperacillin, piperacillin tozobactam and amoxicillin-clavulanic acid were 100%, ceftazidime, cefuroxime, cefixime, aztreonam, sulphamethoxazole-trimethoprim, erythromycin, chloramphenicol and doxycyclin were > 70%, cefoxitin (62.5%), Nitrofurantion (52.5%), ciprofloxacin (45%), ofloxacin (35%), perfloxacin (37.5%), gentamicin (32.5%) and imipenem (2.5%). Of the 11 Staphylococcus aureus collected, 54.5% were detected to be MRSA strains while ESBL production was detected in 55.2% of the Gram negative isolates. This study revealed 100% MDR phenotype constituting high level of MRSA strains (54.5%) and ESBL producers (55.2%) among Gram-positive and Gram-negative bacterial wound isolates respectively. Hence, this calls for caution in the use of extended spectrum antibiotics in treating patients with infected wounds.

Isolation and characterization of bacteria from the feathers of wild Dark-eyed Juncos (Junco hyemalis)

We dislodged microbes from samples of composites of ventral feathers from different birds of overwintering Dark-eyed Juncos (Junco hyemalis) after mist-net capture in south-central Kansas, USA. Bacterial loads were measured by standard plate counts and >300 isolates were purified by repetitive streak-plating on R2A medium (+ cycloheximide). Biochemical and physiological characterization included identification by 16S rRNA gene phylogeny. Nearly half of the isolates grew on keratin and 80% exhibited lipase activity, suggesting that these isolates can degrade feathers and thus may affect survival and reproduction. Individual bacterial loads from 8 juncos varied within a 3-fold range, 105–106 colony-forming units g−1 feather. At 97% DNA sequence identity (species-level), 63 operational taxonomic units were detected among 202 sequences; the Chao1 estimate was 123. The Shannon diversity index (H; 97% identity) was 3.75, Simpson's diversity index (1/D) was 16.1, and Good's coverage was 82.4. Gram-positive bacteria dominated the culture collection, balanced between low and high G+C clades. Bacillus spp. were abundant, including B. asahii, B. cereus, B. megaterium, and B. pumilus. Lysinibacillus, Paenibacillus, and Staphylococcus also were isolated. Remarkably, substantial numbers of Actinomycetes were isolated, including representatives of Clavibacter, Curtobacterium, Microbacterium, and Rathayibacter, genera recognized as being populated by xylem-filling crop plant pathogens. Apposed to these were feather isolates implicated as beneficial to host plants, Frigoribacterium and Kitasatospora, being antagonists to plant pathogens or acting as plant growth promoters. High G+C Gram-positive bacterial isolates included Blastococcus, Cellulomonas, Humicoccus, Nocardioides, Promicromonospora, and Rhodococcus. Proteobacteria dominated the Gram-negative bacteria, with Alphaproteobacteria most abundant, including the potential plant pathogens Agrobacterium and Sphingomonas, and the oligotrophs Aurantimonas, Brevundimonas, Methylobacterium, Rhizobium, and Rhodobacter. Gammaproteobacteria included Pantoea, Pseudomonas, and Stenotrophomonas. Ours is the first report of abundant helpful and harmful phyllosphere bacteria on wild bird feathers. The clear implication is that free-living migratory birds may carry bacteria throughout their geographic ranges and may transmit pathogens and beneficial bacteria to plants.

Differential toxicity of Al2O3 particles on Gram-positive and Gram-negative sediment bacterial isolates from freshwater.

The current study was aimed to explore the differential effects on Gram-positive and Gram-negative freshwater sediment bacterial isolates upon exposure to nano-particles and bulk particles of Al2O3 at low concentrations (0.25, 0.5, and 1mg/L). The Gram-negative Pseudomonas aeruginosa was more susceptible to both the nano-forms and bulk forms than the Gram-positive Bacillus altitudinis. The generation of reactive oxygen species (ROS) and release of lipopolysaccharide due to membrane damage were dependent on the dose of nano-Al2O3. The Fourier transform infrared spectroscopy (FT-IR) studies confirmed the attachment of nano-Al2O3 on bacterial cells, which may lead to subsequent changes in the cell membrane composition and integrity. Internalization of nano-Al2O3 was estimated to be more for P. aeruginosa than for B. altitudinis cells. As a role of defense mechanism, the biofilm formation and production of extracellular polymeric substances (EPSs; polysaccharide and protein) were increased with respect to the concentration of toxicant. Nano-Al2O3 was estimated to cause more DNA damage than the bulk particles in both Gram-positive and Gram-negative bacterial strains.

Septic arthritis of the knee: clinical and laboratory comparison of groups with different etiologies

OBJECTIVES:To clinically and epidemiologically characterize a population diagnosed with and treated for septic arthritis of the knee, to evaluate the treatment results and to analyze the differences between patients with positive and negative culture results, patients with Gram-positive and Gram-negative bacterial isolates and patients with S. aureus- and non-S. aureus-related infections.METHODS:One hundred and five patients with septic knee arthritis were included in this study. The clinical and epidemiological data were evaluated. Statistical analysis was performed to compare patients with and without an isolated causative agent, patients with Gram-positive and Gram-negative pathogens and patients with S. aureus-related and non S. aureus-related infections.RESULTS:Causative agents were isolated in 81 patients. Gram-positive bacteria were isolated in 65 patients and Gram-negative bacteria were isolated in 16 patients. The most commonly isolated bacterium was S. aureus. Comparing cases with an isolated pathogen to cases without an isolated pathogen, no differences between the studied variables were found except for the longer hospital stays of patients in whom an etiological agent was identified. When comparing Gram-positive bacteria with Gram-negative bacteria, patients with Gram-positive-related infections exhibited higher leukocyte counts. Patients with S. aureus-related infections were more frequently associated with healthcare-related environmental encounters.CONCLUSION:S. aureus is the most common pathogen of septic knee arthritis. Major differences were not observed between infections with isolated and non-isolated pathogens and between infections with Gram-positive and Gram-negative bacteria. S. aureus infections were more likely to be associated with a prior healthcare environment exposure.

Rifaximin combined with polymyxins: A potential regimen for selective decontamination of multidrug-resistant bacteria in the digestive tract?

Selective decontamination of the digestive tract (SDD) using combinations of oral non-absorbable antibiotics has been proposed as a means of preventing multidrug-resistant (MDR) infections. The minimum inhibitory concentrations (MICs) of rifaximin (RIFAX) were determined against 262 Gram-negative and Gram-positive bacterial isolates by broth microtitre assay. Rifampicin (RIF) was used as a comparator in the analysis. Synergistic interactions between RIFAX and polymyxin B (PMB) were assessed by using the chequerboard method and calculating the fractional inhibitory concentration index (FICI). The antimicrobial activities of both RIFAX and RIF were similar with little variation in the overall MIC distributions for Gram-negative non-fermenters and Gram-positive bacteria. However, against Enterobacteriaceae higher MICs (>16mg/L) were observed for RIFAX than for RIF (50% vs 27%). Amongst the 262 isolates tested, 100 could be considered resistant to RIFAX. Overall, the combination of RIFAX and PMB was more active against all of the isolates tested compared with either drug alone, with reductions of 2-11 doubling dilutions in individual MICs. Potent synergy was observed with the RIFAX+PMB combination using FICI criteria (FICI range 0.02-0.5). The data presented here suggest that combination therapy may be significantly more effective against isolates with RIFAX and/or PMB resistance and could be considered as part of a SDD regimen aimed at reducing enteric carriage of MDR pathogens in colonised and infected patients.

Analysis of pathogenic bacteria and drug resistance in neonatal purulent meningitis

To study the clinical characteristics, pathogenic bacteria, and antibiotics resistance of neonatal purulent meningitis in order to provide the guide for early diagnosis and appropriate treatment. A retrospective review was performed and a total of 112 cases of neonatal purulent meningitis (male 64, female 58) were identified in the neonatal intensive care unit of Yuying Children's Hospital of Wenzhou Medical University seen from January 1, 2004 to December 31, 2013. The clinical information including pathogenic bacterial distribution, drug sensitivity, head imageology and therapeutic outcome were analyzed. Numeration data were shown in ratio and chi square test was applied for group comparison. Among 112 cases, 46 were admitted from 2004 to 2008 and 66 from 2009 to 2013, 23 patients were preterm and 89 were term, 20 were early onset (occurring within 3 days of life) and 92 were late onset meningitis (occurring after 3 days of life). In 62 (55.4%) cases the pathogens were Gram-positive bacteria and in 50 (44.6%) were Gram-negative bacteria. The five most frequently isolated pathogens were Escherichia coli (32 cases, 28.6%), coagulase-negative staphylococcus (CNS, 20 cases, 17.9%), Streptococcus (18 cases, 16.1%, Streptococcus agalactiae 15 cases), Enterococci (13 cases, 11.6%), Staphylococcus aureus (9 cases, 8.0%). Comparison of pathogenic bacterial distribution between 2004-2008 and 2009-2013 showed that Gram-positive bacteria accounted for more than 50% in both period. Escherichia coli was the most common bacterium, followed by Streptococcus in last five years which was higher than the first five years (22.7% (15/66) vs. 6.5% (3/46), χ(2) = 5.278, P < 0.05). Klebsiella pneumoniae was more common isolate in preterm infants than in term infants (13.0% (3/23) vs. 1.1% (1/89), χ(2) = 7.540, P < 0.05). Streptococcus (most were Streptococcus agalactiae) was the most common bacteria in early onset meningitis and higher than those in late onset meningitis (35.0% (7/20) vs. 12.0% (11/92), χ(2) = 4.872, P < 0.05). Drug sensitivity tests showed that all the Gram-positive bacterial isolates were sensitive to linezolid. Staphylococci were resistant to penicillin, and most of them were resistant to erythromycin, oxacillin and cefazolin; 77.8%of CNS isolates were methicillin-resistant staphylococcus. No Streptococcus and Enterococcus faecalis was resistant to penicillin. None of enterococci was resistant to vancomycin. Among the Gram-negative bacterial isolates, more than 40% of Escherichia coli were resistant to commonly used cephalosporins such as cefuroxime, cefotaxime and ceftazidime, and all of them were sensitive to amikacin, cefoperazone sulbactam and imipenem. Isolates of Klebsiella pneumoniae were all resistant to ampicillin, cefuroxime, cefotaxime and ceftazidime, but none of them was resistant to piperacillin tazobactam and imipenem. Of the 112 patients, 69 were cured, 23 improved, 9 uncured and 11 died. There were 47 cases (42.0%) with poor prognosis, they had abnormal head imageology, severe complications and some cases died, 13 of 18 (72.2%) patients with meningitis caused by Streptococcus died. Escherichia coli, CNS and Streptococcus are the predominant pathogens responsible for neonatal purulent meningitis over the past ten years. There were increasing numbers of cases with Streptococcus meningitis which are more common in early onset meningitis with adverse outcome, therefore careful attention should be paid in clinic. Linezolid should be used as a new choice in intractable neonatal purulent meningitis cases caused by gram positive bacteria.

Retrospective Analysis of Bacterial Pathogens Isolated from Wound Infections at a Tertiary Hospital in Nguru, Yobe State Nigeria

Wound infections inflict clinical and societal consequences on the patients, but its bacteriological characteristic varies with different factors. Therefore, effective treatment and management of wound infections in hospital and community setting will require detailed epidemiological knowledge of the infecting bacterial pathogens and their antibiogram peculiar to the environment. Based on this information, we examined the prevalence and antibiogram of bacterial pathogens isolated from wound infection cases seen at the hospital over the study period. A total of 392 wound swabs/ and pus of different types of wound infections from different anatomical sites and associated clinical conditions were analyzed by standard bacteriological methods. Of the 392 clinical specimens analyzed, 301(76.8%) yielded at least one bacterial pathogen, 25(6.4%) polymicrobial, no anaerobes identified and 91(23.2%) yielded no bacterial growth, gender distribution, 204(67.8%) males and 97(32.2%) females, and majority of pathogens were recovered from septic wound infections. Overall, 7 different bacterial pathogens were identified 5(71.4%) gram-negative bacteria isolates and 2(28.6%) gram-positive bacterial isolates]. Staphylococcus aureus accounted for majority of the bacterial pathogens isolated, 162(53%) followed by coliforms 62(21%) and Pseudomonas aeroginosa 57(19%). The bacterial pathogens demonstrated high resistance to ampicillin(78%), amoxicillin(66%), and cotrimoxazole(78%), in contrast to high sensitivity pattern observed with fluoroquinolones ( ofloxacin 83%,, norfloxacin 71%, ciprofloxacin 78%), erythromycin 72%, chloramphenicol 62%, gentamycin 58% and ceftazidime 60%. The relatively high number of wound infection cases seen within the study period is of public health concern, while the low number of bacterial pathogens isolated underscores the need for improvement in the laboratory diagnostic approach for effective treatment and management of wound infections.

Synthesis, characterization and antimicrobial studies on 13-membered-N6-macrocyclic transition metal complexes containing trimethoprim

Asymmetrical macrocyclic complexes of MnII, CoII, NiII, CuII and ZnII have been synthesized by the template process using bis(benzil)ethylenediamine as precursor. Bis(benzil)ethylenediamine reacts with transition metal chlorides and trimethoprim in a 1:1:1 molar ratio in methanol to give several solid metal complexes of the general composition [M(L)X2] (M=MnII, CoII, NiII, CuII and ZnII, L=ligand and X=Cl−). They were characterized by physicochemical and spectroscopic techniques. Based on analytical, spectral and magnetic moments, all the complexes are identified as distorted octahedral structures. All the complexes are of the [M(L)X2] type. The shifts of the ν(CN) (azomethine) stretches have been monitored. To find out the donor sites of the ligands, the activity data show that the metal complexes are more potent than the parent ligand. The [M(L)X2] complexes showed a broad spectrum of antimicrobial activity in vitro against both gram-positive and gram-negative human pathogenic bacterial isolates and the antimicrobial spectrum enhanced only with a combination of metal chlorides and trimethoprim complex. From the results it is imperative that the synthesized macrocyclic [M(L)X2] complexes exhibit potent broad spectrum antibacterial activity.

Bacteria etiological agents causing lower respiratory tract infections in the western part of Nepal

Objectives: Lower respiratory tract infections (LRTIs) are among the most common infectious disease. We determined the bacterial etiology of LRTIs among patients attending Nepalgunj Medical College teaching hospital in Banke, western Nepal. Materials and Methods: 426 specimens from patients with suspected LRTIs attending out-patients and in-patients departments were studied. The specimens were collected and processed according to standard methodology in the Central Laboratory of Microbiology at Nepalgunj Medical College and Teaching Hospital, Banke, Nepal during the period of January to December 2012. Results: Respiratory pathogens were recovered from 210 cases (49.3%). Bacteria were more commonly recovered from endotracheal secretions (86 cases; 41%) than in sputum (82 cases; 39%) and bronchial washing (42 cases, 20%). In168 cases, growth was monomicrobial while the rest was mixed growth. Gram-negative bacteria were isolated in 246 cases (80.9%) and Gram-positive bacteria in 58 cases (19.1%). Among the Gram-positive organisms isolated, Streptococcus pneumoniae (30, 51.7%) was the most predominant pathogen followed by Staphylococcus aureus (28, 48.3%) and in Gram-negative organisms isolated, Pseudomonas aeruginosa (116, 47.2%) was most predominant pathogen followed by Haemophilus influenzae (68, 27.6%), Klebsiella pneumoniae (36, 14.6%) and Escherichia coli (26, 10.6%). Conclusions: Respectively, Pseudomonas aeruginosa and Streptococcus pnemoniae were the most common Gram negative and Gram-positive bacterial isolates recovered from LRTIs. Close monitoring and surveillance of these pathogens is urged.

Myroides pelagicus from the Gut of Drosophila melanogaster Attenuates Inflammation on Dextran Sodium Sulfate-Induced Colitis

Probiotics are live microorganisms that confer a health benefit on the host when administered in adequate amounts. In the present study, the putative probiotic strain was identified from the gut of Drosophila melanogaster and assessed for its protective effect in inflammatory bowel disease. Active probiotics were screened from the Drosophila melanogaster gut by the selection criteria of gastric juice tolerance, hydrophobic property, antimicrobial potential, adhesion, and invasion properties. The active probiotics were identified by 16s rDNA sequencing and the effect of these active probiotics was evaluated in a Dextran sulphate sodium (DSS)-induced mice model by estimating inflammatory markers and histopathological changes. Nine Gram-positive and bile salt tolerant bacterial isolates were obtained from the gut samples. The isolates PTH 2, PTH 4, and PTH 7 clearly showed significant activity in antimicrobial potential, hydrophobic (>74%) property, and intestinal juice tolerance. Among these, PTH 7 was selected for further studies due to its significant low-invasion ability and it proved capable of reducing the secretion of proinflammatory cytokines. The 16s rDNA studies revealed that PTH 7 was Myroides pelagicus. Administration of M. pelagicus to the DSS-induced colitic animals significantly suppressed myeloperoxidase, ALP, and malondialdehyde levels, and also lowered levels of proinflammatory cytokine expression. Further, the recovery from the disease by the probiotic treatment was supported by histopathological and macroscopic observation. The treated animals did not show any adverse signs in their physiology or behavior. Myroides pelagicus successfully prohibited inflammatory markers and acted as a potent probiotic. Future studies with this stain might prove its efficacy as a drug for the management of colitis.

Bacteriobilia and fungibilia are associated with outcome in patients with endoscopic treatment of biliary complications after liver transplantation

To determine the importance of bacteriobilia and fungibilia in patients with endoscopic treatment of biliary complications after orthotopic liver transplantation (OLT). In a prospective study at a tertiary center, 213 patients underwent 857 endoscopic retrograde cholangiographies (ERCs) after OLT. Findings at first ERC were: anastomotic stricture in 24.4%, nonanastomotic stricture in 18.3%, leakage in 11.3%, and gallstones in 4.7%. Bile samples from first ERC showed Gram-positive bacterial isolates in 102/180 (57%) and Gram-negative in 44/180 (24%). Main species were Enterococcus spp. (40%; 72/180) and Escherichia coli (10%; 18 /180). Enteric bacteria (present in 47%) and Candida spp. (present in 18%) were both associated with clinical signs of cholangitis, but not with laboratory signs of inflammation. Multiresistant strains (present in 12% of samples) showed no association with clinical or laboratory parameters. Detection of microbiological isolates was independent of endoscopic findings and treatment. In patients with successful endoscopic intervention, the actuarial survival free of retransplantation was significantly lower in those with detection of enteric bacteria, being 51.8 months (95% confidence interval [CI] 42.9-60.6) vs. 62.9 months (95% CI 59.1-66.7); P = 0.025). Fungibilia was associated with significantly lower actuarial retransplantation-free survival, independently of successful endoscopic treatment (mean 35.1 months [95% CI 23.5-46.7] vs. 53.1 months [(95% CI 48.0-58.2]; P = 0.019). Bacteriobilia and fungibilia can frequently be detected by routine microbiological sampling in patients after OLT. Regular bile sampling is recommended since the presence of difficult-to-treat multiresistant strains is unpredictable. Survival is affected by this altered biliary microbiological environment after OLT.

Rapid Identification of Microbes in Positive Blood Cultures by Use of the Vitek MS Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry System

Sepsis is a major cause of death worldwide among nonhospitalized people and hospitalized patients. A wide range of pathogens are involved, and the correct identification and correct antimicrobial therapy are critical to ensure optimal clinical outcomes. With the recent introduction of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), rapid identification of bacteria and fungi is now possible. The purpose of this study was to develop a rapid technique for identifying organisms in positive blood cultures using the Vitek MS system (bioMérieux). This technique is a lysis centrifugation method which involves a four-step washing and centrifugation procedure. A total of 253 positive monomicrobial blood cultures (Bactec Plus aerobic, anaerobic, and pediatric bottles) were tested using the Vitek MS system (KnowledgeBase version 2.0), with 92.1% and 88.1% of organisms overall being identified to the genus level and the species level, respectively. Of 161 Gram-positive bacterial isolates, 95.7% and 90.1% were identified to the genus level and the species level, respectively; of 92 Gram-negative bacterial isolates, 84.7% and 83.7% were identified to the genus level and the species level, respectively. The results obtained using this method demonstrate that the Vitek MS system can be used for rapid and effective identification of bacteria from positive blood cultures within 30 to 45 min after the positive signal has been provided by the Bactec FX blood culture system (Becton, Dickinson). This will lead to faster administration of the appropriate antimicrobial therapy and increase the chances for optimal clinical outcomes for patients.

Rapid Detection of Gram-Positive Organisms by Use of the Verigene Gram-Positive Blood Culture Nucleic Acid Test and the BacT/Alert Pediatric FAN System in a Multicenter Pediatric Evaluation

Assays that expedite the reporting of organism identification and antibiotic susceptibility status in positive blood cultures can fast track interventions that improve clinical outcomes. We evaluated the Verigene Gram-positive blood culture nucleic acid test (BC-GP) in two pediatric hospitals. Positive BacT/Alert Pediatric FAN blood cultures with Gram-positive organisms were tested using the BC-GP in tandem with routine laboratory procedures. To test organisms underrepresented in the clinical blood culture evaluation, blood culture bottles were spiked with diluted organism suspensions at concentrations of 10 to 100 CFU per milliliter. A total of 249 Gram-positive bacterial isolates were recovered from 242 blood cultures. The BC-GP detected Staphylococcus aureus, methicillin-susceptible S. aureus, and methicillin-resistant S. aureus with sensitivities of 100%, 99%, and 100% and specificities of 100%, 100%, and 99.5%, respectively. The BC-GP detected Staphylococcus epidermidis, methicillin-susceptible S. epidermidis, and methicillin-resistant S. epidermidis with sensitivities of 95%, 80%, and 96%, respectively, and 100% specificity. The BC-GP correctly identified 14/15 cases of Enterococcus faecalis and Enterococcus faecium bacteremia and 9 cases of Streptococcus pneumoniae. It misidentified 5/15 clinical blood cultures with Streptococcus mitis/Streptococcus oralis and 1/3 blood cultures spiked with Streptococcus anginosus group as S. pneumoniae. The BC-GP detected a case of Streptococcus pyogenes bacteremia but failed to detect 2/3 clinical blood cultures with Streptococcus agalactiae. BC-GP's rapid accurate detection of Staphylococcus spp., E. faecium, and E. faecalis and its ability to ascertain mecA, vanA, and vanB status may expedite clinical decisions pertaining to optimal antibiotic use. False-positive S. pneumoniae results may warrant reporting of only "Streptococcus spp." when this organism is reported by the BC-GP.

ANTIBIOGRAM PATTERN OF BACTERIAL ISOLATES FROM SUBCLINICAL MASTITIS IN COWS

From 69 lactating cows of University livestock farm , a total of 266 quarters were screened for subclinical mastitis (SCM), 89 quarters were found to be positive which resulted in the recovery of 190 bacterial isolates. Of these, 50 (56.17%) quarters yielded monomicrobic isolates whereas 39 (43.82%) quarters harboured mixed infection. On bacteriological culture examination, a total of 190 bacterial isolates were recovered which comprised of 54 isolates of CPS, 115 isolates of CNS 2 isolates of Micrococcous varians, 11 isolates of Str. agalactiae and 8 isolates of coliforms. In the present study a total of 67 isolates comprising of 57 gram positive and 10 gram-negative isolates were studied for their antibiogram pattern against 20 antibacterial drugs . Results of invitro drug susceptibility testing on gram-positive and gram-negative bacterial isolates showed that most of the broad-spectrum antibacterial drugs were found highly effective against isolates recovered from cases of subclinical mastitis. The sensitivity profile of isolates showed poor sensitivity towards commonly used antibacterial drugs penicillin, ampicillin and amoxyclav.

Antibacterial serrulatane diterpenes from the Australian native plant Eremophila microtheca

Chemical investigations of the aerial parts of the Australian plant Eremophila microtheca resulted in the isolation of three serrulatane diterpenoids, 3-acetoxy-7,8-dihydroxyserrulat-14-en-19-oic acid (1), 3,7,8-trihydroxyserrulat-14-en-19-oic acid (2) and 3,19-diacetoxy-8-hydroxyserrulat-14-ene (3) as well as the previously reported compounds verbascoside (4) and jaceosidin (5). Acetylation and methylation of the major serrulatane diterpenoid 2 afforded 3,8-diacetoxy-7-hydroxyserrulat-14-en-19-oic acid (6) and 3,7,8-trihydroxyserrulat-14-en-19-oic acid methyl ester (7), respectively. The antibacterial activity of 1-7 was assessed against a panel of Gram-positive and Gram-negative bacterial isolates. All of the serrulatane compounds exhibited moderate activity against Streptococcus pyogenes (ATCC 12344) with minimum inhibitory concentrations (MICs) ranging from 64-128 μg/mL. Serrulatane 1 demonstrated activity against all Gram-positive bacterial strains (MICs 64-128 μg/mL) except for Enterococcus faecalis and Enterococcus faecium. This is the first report of natural products from E. microtheca.

Recent trend of bacterial aetiology of lower respiratory tract infection in a tertiary care centre of Nepal

INTRODUCTION: Lower respiratory tract infections (LRTIs) are among the most common infectious diseases of humans. This study focused on determining the recent trend of bacterial aetiology of LRTIs among the patients attending Tribhuvan University Teaching Hospital (TUTH) in Kathmandu. MATERIALS AND METHODS: This was a prospective study conducted over a period of six months in the bacteriology laboratory of TUTH. A total of 1120 specimens representing lower respiratory tract were received from patients with suspected LRTIs. The specimens were collected and processed according to standard methodology. RESULTS: Respiratory pathogens were recovered from 44.4% cases (n=497). Gram-negative bacteria were recovered in 84.1% (n=488). Bacteria were more commonly recovered from endotracheal secretion (41/61, 67.2%) than in sputum (454/1039, 43.7%) and bronchial washing (2/20, 10%). Ninety-one percent (n=454) growth was monomicrobial while the rest accounted for mixed growth. Among the organisms isolated, Haemophilus influenzae (112, 21%) was the most predominant pathogen followed by Klebsiella pneumoniae (102, 19.1%), Pseudomonads (91, 17.1%), Acinetobacter baumannii calcoaceticus complex (60, 10.9%), Streptococcus pneumoniae (46, 8.6%), Escherichia coli (37, 6.9%). CONCLUSIONS: H. influenzae and S. pneumoniae were the most common Gram-negative and Grampositive bacterial isolates recovered, respectively from LRTIs urging for monitoring and surveillance of these pathogens.DOI: http://dx.doi.org/10.3126/ijim.v1i1.6639 Int J Infect Microbiol 2012;1(1):3-8

Synthesis and Evaluation of Antimicrobial Silver Nanoparticles on Multidrug-Resistant Bacterial Isolates from Urine Samples of Diabetic Patients and Infected Human Soft Tissues

Antimicrobial citrate-stabilized silver nanoparticles (AgNPs) were synthesized by dissolving silver nitrate in water and the antimicrobial activity was studied against multidrug-resistant bacterial isolates from urine samples of diabetic patients and infected human soft tissues of patients undergoing prolonged antibiotic treatment. The minimum inhibitory concentration and minimum bactericidal concentration values of the AgNPs were found to be 60, 80 and 140, 160 μg/mL against Bacillus megaterium and Staphyloccus aureus, respectively, isolated from infected human soft tissues and 60, 80 and 120, 160 μg/mL against Kluyvera ascorbata and Escherichia coli, respectively, isolated from urine samples of diabetic patients. The sizes of the AgNPs were found to be of 141 nm and were stable till 120 days at 37 °C. The AgNPs were found to be effective against both gram-positive and negative bacterial isolates.

A comparative study of the effect of different topical agents on burn wound infections

Background:Topical agents are used to treat burn wound infections.Aims and Objective:The present work was aimed to find out the in vitro efficacy of different topical agents against burn wound pathogens.Settings and Design:Randomly selected gram-positive (29) and gram-negative bacterial (119) isolates from burn wound cases admitted in burn unit of Choithram Hospital and Research Centre, Indore, were included in the in vitro activity testing for silver nitrate, silver sulphadiazine (SSD), chlorhexidine, cetrimide, nitrofuran, soframycin, betadine, benzalkonium chloride and honey by growth inhibition on agar medium.Materials and Methods:Multidrug-resistant isolates of gram-positive and gram-negative bacteria were checked for different topical agents. 1% topical agent was mixed with Mueller-Hinton agar. Two microlitres of bacterial suspension adjusted to 0.5 McFarland turbidity standard was spread over the topical agent containing plates. The plates without the topical agent were used as control plates. The plates were incubated for 48 h at 37°C.Results:SSD (148/148), silver nitrate (148/148) and chlorhexidine (148/148) showed excellent activity against all the pathogens. Neosporin had poor activity against Pseudomonas aeruginosa, (4/44) Proteus spp. (2/4) and group D streptococci (1/4). Betadine did not show activity against the bacterial isolates in the presence of organic matter. Honey did not exert any antimicrobial activity under the study conditions.Conclusion:SSD, silver nitrate and chlorhexidine have excellent activity against all the bacterial pathogens and could be used empirically, while identification of the infective agent is required for selecting the alternative topical agents such as nitrofuran, soframycin, and benzalkonium chloride.

Microbacterium sediminis sp. nov., a psychrotolerant, thermotolerant, halotolerant and alkalitolerant actinomycete isolated from deep-sea sediment

An aerobic, rod-shaped, Gram-positive, oxidase- and catalase-positive bacterial isolate, strain YLB-01(T), was characterized using phenotypic and molecular taxonomic methods. 16S rRNA gene sequence analysis revealed that the isolate belonged to the genus Microbacterium and represented an evolutionary lineage that was distinct from recognized species of the genus Microbacterium. The isolate showed <97 % 16S rRNA gene sequence similarity with respect to the type strains of all of the members of the genus Microbacterium with validly published names. Cell-wall hydrolysate from the isolate contained the amino acids ornithine, alanine, glycine homoserine and glutamic acid, and the cell-wall sugars consisted of ribose, glucose and galactose. The main respiratory quinones were MK-8, 9, 10 and 11. The major cellular fatty acids were anteiso-C(15:0) (38.5 %), anteiso-C(17:0) (23.1 %) and C(16:0) (18.9 %). The polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, an unidentified phospholipid and two unidentified glycolipids. The DNA G+C content of strain YLB-01(T) was 71 mol %. On the basis of the morphological, physiological and chemotaxonomic data and the results of comparative 16S rRNA gene sequence analysis, this isolate represents a novel species of the genus Microbacterium, for which the name Microbacterium sediminis sp. nov. is proposed. The type strain is YLB-01(T) (= DSM 23767(T) = CCTCC AB2010363(T) = MCCC 1A06153(T)).