Septicemic Isolates Research Articles

Phagoburst Response Level of Neutrophils to Septic and Non-Septic Acinetobacter baumannii Isolates

Background: Acinetobacter baumannii is an opportunistic pathogen causing community-acquired and nosocomial infections. Dissemination of infection to blood causes septicemia associated with serious morbidity and mortality of patients. Neutrophils are essential for the control of A. baumannii infections by different mechanisms, including oxidative burst. Aims: This study was conducted as an attempt to determine the effect of septicemic and non-septicemic A. baumannii isolates on the phagoburst response of neutrophils. Methods: Neutrophils were isolated from an immunocompetent individual; chronic myeloid leukemia (CML) and lung solid tumor (ST) patients. The phagoburst response of these neutrophils to various strains of A. baumannii isolated from septic and non-septic patients was investigated by flow cytometer. Results: The presence of this pathogen lowered the phagoburst response in the different types of neutrophils compared to their response to the opsonized Escherichia coli. The phagoburst response of the neutrophils from the immunocompetent individual was significantly higher than that of neutrophils from the immunodeficient patients when stimulated by the septicemic or nonsepticemic A. baumannii isolates. The isolate type (septicemic or non-septicemic) had no significant effect on the neutrophil phagoburst response of the immunocompetent individual and a significant effect on the phagoburst response of neutrophils from the immunodeficient patients. The phagoburst response of the neutrophils from the immunodeficient patients stimulated by septicemic A. baumannii isolates was significantly lower than that when neutrophils stimulated by the nonsepticemic isolates. Also, there was a significant difference in the phagoburst response of neutrophils from the CML and ST patients when stimulated by the septicemic and non-septicemic isolates. This observation might be due to the combined effect of virulent A. baumannii isolates and the chemotherapy regime the patient was undertaking. Conclusion: The results suggest that both the isolate type and the source of neutrophils have a significant effect on the neutrophil phagoburst response. The potential virulence of the septicemic A. baumannii isolates and dissemination to blood may be dependent on the host’s immune status and the neutrophils phagoburst response.

Bacteriologic Antibiography Outline of Isolates from Blood Culture at Tertiary Center

Bacteria found in blood circulation either consistently intermittently are commination to every organs of body. These infections can affect life and death. In India also blood stream infections are major causes of health problem that caused demise of patients in hospital. Timely diagnoses of infection with antimicrobial susceptibility assessment are important for optimization of treatment and best way to reduce hospital stay and improve patient health. In spite of recent advances in clinical diagnostics, blood culture remains the gold standard for the detection of blood stream infections. Studies in different places and regions have indicated the varying microbiological pattern of bloodstream infections which support the need for a continuous examination of the causative organisms. For the diagnosis of septicemia, Blood cultures are the “gold standard” are based on the detection of viable microorganisms in the blood. The main aim of this is to identify the bacteria causing bloodstream infections and to determine and analysis their antibiotic sensitivity pattern in a tertiary center. In this study blood for culture was collected from 940 clinically suspected cases of blood stream infection from the hospital. Collected blood samples were processed in the bacteriology section at microbiology laboratory and standard laboratory methods were used to identified isolates and then antibiotic susceptibility test was performed using CLSI guidelines. Total 940 blood samples were cultured in which 139(14.8%) were found positive. Among isolates, the most predominant organism was Staphylococcus aureus (51.8%) followed by Escherichia coli (24.5%) and the least was Salmonella species (1.4%), Proteus species (1.4%) and Acinetobacter species (1.4%). Among Gram positive isolates, Penicillin and Erythromycin showed high degree of resistance. Imipenem was particularly susceptible among the isolated. Gentamicin and Amikacin showed high in vitro susceptibility for both Enterobacteriaceae and Nonfermenters. This study provides information on bacteriological profile of septicemic isolates. Therefore continuous monitoring of the susceptibility of organisms towards antibiotics is necessary to prevent and spread of drug resistance.

Bacteriological profile and antibiogram of blood culture isolates from a tertiary care hospital of North India

Introduction: Blood stream infections cause a significant morbidity and mortality worldwide. Rapid and reliable detection of bacterial pathogens and rational use of antimicrobials are required for proper management. The present work was undertaken to study the bacteriological profile along with the antibiogram of the blood culture isolates from clinically diagnosed cases of sepsis. Materials and Methods: During the 1-year study period, 3472 blood samples from patients with a clinical diagnosis of sepsis were received at the Emergency Microbiology Laboratory of a 2500-bedded tertiary care hospital of North India. Bacteriological identification and antimicrobial susceptibility testing were performed for all bacterial isolates by following the standard protocol. Results: Culture positivity was seen in 16.5% of the septicemic cases. The most common bacteria isolated were Escherichia coli (22.4%) followed by Klebsiella species (19.7%), Staphylococcus aureus (18.3%), and coagulase-negative staphylococci (17.4%). About 26.5% of S. aureus were methicillin-resistant. Vancomycin (100%), gentamicin (87.9%), and ciprofloxacin (73%) showed the highest activity among the Gram-positive isolates. Most of the Gram-negative bacteria were multi-drug resistant (67.1%). Imipenem (98.8%), amikacin (90.8%), and cefoperazone/sulbactam combination (81.1%) showed the highest activity among Enterobacteriaceae. Nonfermenters in majority were susceptible to imipenem (88.2%), amikacin (81.6%), and piperacillin/tazobactam combination (72.4%). Gram-negative isolates showed 100% sensitivity toward colistin. Conclusion: The present study highlights the bacteriological etiology of sepsis along with the antibiogram of septicemic isolates that may provide necessary information for the formulation of antibiotic policy in effective management of such cases.

The high prevalence of serine protease autotransporters of Enterobacteriaceae (SPATEs) in Escherichia coli causing neonatal septicemia.

Serine protease autotransporters of Enterobacteriaceae (SPATEs) are secreted proteins demonstrating diverse virulence functions. The distribution of SPATEs is studied among diarrheagenic and extraintestinal pathogenic Escherichia coli. However, the contribution of SPATEs to the virulence of neonatal septicemic Escherichia coli (NSEC) has not yet been elucidated. This study was undertaken to evaluate the prevalence and phylogenetic distribution of different subtypes of SPATEs among NSEC. The presence of virulence factors and subtypes of SPATEs among different E. coli isolates was determined by polymerase chain reaction (PCR). E. coli phylogrouping was done by triplex PCR. Clonality of the isolates was assessed by pulsed-field gel electrophoresis (PFGE). The presence of SPATEs was significantly higher among the septicemic isolates (89 %) than the fecal (7.5 %) and environmental isolates (2.5 %). Vat (vacuolating autotransporter toxin) and Sat (secreted autotransporter toxin) were found to be the two most predominant SPATEs. The incidence of SPATEs was high in septicemic isolates of phylogroups A and B1 (87 %), lacking other virulence factors. The high prevalence of SPATEs in the non-B2 phylogroups of septicemic isolates in comparison with fecal and environmental isolates indicates an association of SPATEs with NSEC. The NSEC isolates were found to be clonally distinct, suggesting that the high prevalence of SPATEs was not due to clonal relatedness of the isolates. This study is the first to show the association of SPATEs with NSEC. The presence of SPATEs in the septicemic/NSEC isolates may be considered as the most discriminatory trait studied here.

Characterization of Escherichia coli O78 from an outbreak of septicemia in lambs in Norway

The aim of the study was to characterize isolates of Escherichia coli from an outbreak of septicemia in a Norwegian sheep flock in 2008 with emphasis on virulence, serological grouping, phylogenicity and homology. Six E. coli isolates from succumbed neonatal lambs and four E. coli isolates collected from healthy individuals were analyzed by Pulsed-Field Gel Electrophoresis (PFGE), miniaturized microarray, and polymerase chain reaction (PCR). The septicemic E. coli isolates showed identical pulsotypes (PTs), and belonged to serogroup O78, phylogenetic group A, and MLST ST 369. The virulence genes f17G, bmaE, afaE-VIII, ireA, iroN and iss were detected in the septicemic isolates. The results showed that the E. coli isolates from the septicemic outbreak had a clonal appearance, thus likely originating from a common source. The clone carried genes important for virulence, however, a significant explanation for the high pathogenicity was not revealed.

Interaction between Host Cells and Septicemic Salmonella enterica Serovar Typhimurium Isolates from Pigs

Salmonella enterica serovar Typhimurium is an important pathogen in swine and is also a frequently reported zoonotic agent. The objective of this study was to characterize isolates of S. enterica serovar Typhimurium associated with septicemia in swine and to compare them to isolates recovered from clinically healthy pigs. We were particularly interested in comparing the two groups of isolates for their ability to adhere to and invade host cells, to be phagocytized and survive in monocyte cells, to induce apoptosis, and to adhere to intestinal mucus. Their surface properties were also evaluated by interactions with solvents. The isolates recovered from diseased animals were shown to invade intestinal epithelial cell lines at a higher rate (P = 0.003) than isolates from healthy pigs. Septicemic isolates were phagocytized by human monocytes at a higher rate than isolates from healthy pigs (P = 0.009). The mean percentages of phagocytosis were significantly lower for human monocytes than for porcine monocytes (P = 0.02 and P = 0.008, respectively) for isolates from both diseased and healthy animals. Healthy animal isolates were phagocytized more by porcine monocytes at 15 min (P = 0.02) than septicemic isolates. No difference between isolates from septicemic pigs and isolates from healthy pigs was detected for other tested parameters. These results suggest that septicemic isolates have a particular pattern of invasion.

Evaluation of Genotypic and Phenotypic Methods To Distinguish Clinical from Environmental Vibrio vulnificus Strains

Vibrio vulnificus is a heterogeneous bacterial species that comprises virulent and avirulent strains from environmental and clinical sources that have been grouped into three biotypes. To validate the typing methods proposed to distinguish clinical from environmental isolates, we performed phenotypic (API 20E, API 20NE, and BIOLOG tests) and genetic (ribotyping and DNA polymorphism at several loci) studies with a large strain collection representing different biotypes, origins, and host ranges. No phenotypic method was useful for biotyping or grouping strains with regard to the origin of an isolate, and only the BIOLOG system was reliable for identifying the strains at the species level. DNA polymorphisms divided the population into three major profiles. Profile 1 strains were vcg type C, 16S rRNA type B, and vvh type 1 and included most of the biotype 1 human septicemic isolates; profile 2 strains were vcg type E, 16S rRNA type A, and vvh type 2 and included all biotype 2 isolates together with biotype 1 isolates from fish and water and some human isolates; and profile 3 strains were vcg type E, 16S rRNA type AB, and vvh type 2 and included biotype 3 strains. Ribotyping divided the species into two groups: one group that included profile 1 biotype 1 isolates and one group that included isolates of all three biotypes with the three profiles described above. In conclusion, no genotyping system was able to distinguish either clinical strains from environmental strains or biogroups within the species V. vulnificus, which suggests that new typing methodologies useful for public health have to be developed for this species.

Putative virulence characteristics of Stenotrophomonas maltophilia: a study on clinical isolates

Stenotrophomonas maltophilia is an important evolving pathogen, especially in patients with cystic fibrosis (CF), but its mechanism of pathogenesis is poorly understood. The purpose of this study was to investigate the presence of potential virulence determinants in five septicemic clinical isolates of S. maltophilia. When screened for EPS biosynthesis, all five strains produced colonies on two different growth media both at 30 and 37 °C. LPS could be extracted from all strains successfully and all were positive for both cell-free and cell-bound hemolysin production but failed to agglutinate 3% human RBCs. Variation in the ability to produce protease and phospholipase C was observed. In addition, all strains were unable to produce pyochelin but were able to produce ornibactin in the form of hydroxamate derivatives. It was also observed that all strains showed adherence to mouse tracheal epithelium.

Clonal relationships among Escherichia coli serogroup O78 isolates from human and animal infections.

We investigated the clonal relationships among 63 Escherichia coli strains of antigen serogroup O78 isolated from infections in humans, cattle, sheep, pigs, and chickens. Both septicemic and enterotoxigenic isolates were included in the study. A main group of 55 E. coli strains consisting of 52 septicemic isolates and 3 human enterotoxigenic E. coli isolates were clustered in related clones. The remaining eight strains, four human and four animal isolates, were clonally heterogeneous. The main group of 55 clonally related strains included isolates from human and animal infections. This result indicates that animals are a possible source of serogroup O78 septicemic E. coli infections in humans.

Diphenylamine increases cloacin DF13 sensitivity in avian septicemic strains of Escherichia coli

Thirteen avian septicemic isolates of Escherichia coli were examined for the presence of the aerobactin iron transport system. All of the strains possessed a functional aerobactin system and hybridization experiments showed that the aerobactin genes were located on CoIV-type plasmids in all cases. The expression of the aerobactin receptor IutA was also studied by determining the bacterial susceptibility to the bacteriocin cloacin DF13. Twelve of the 13 isolates were cloacin-resistant but became sensitive to this bacteriocin upon treatment with diphenylamine which caused a reduction in the amount of O-side chain lipopolysaccharide.

In vitro activity and in vivo evaluation of ticarcillin plus clavulanic acid against aerobic and anaerobic bacteria

The efficacy of ticarcillin plus clavulanic acid was compared with that of certain broad-spectrum antibiotics such as ticarcillin, azlocillin, and piperacillin against blood culture Isolates of aerobic bacteria obtained from seriously ill patients and anaerobic bacteria obtained from other miscellaneous infections. Ticarcillin plus clavulanic acid was found to be as effective as other broad-spectrum antibiotics against most of the 285 septicemic isolates tested. Ticarcillin plus clavulanic acid was most effective against 351 anaerobic bacteria, including B. fragilis. Further, 32 strains of B. fragilis that were relatively resistant to ticarcillin and azlocillin were tested with a mixture of ticarcillin or azlocillin, each in combination with clavulanic acid. Ticarcillin plus clavulanic acid Inhibited all 32 strains of B. fragilis. Addition of clavulanic acid to cephalothin, penicillin, or azlocillin also augmented the antibiotic activity against B. fragilis by 4- to 64-fold. These in vitro data suggest that ticarcillin plus clavulanic acid may be used as a single antibiotic in the cases of bacterial septicemias and that the combination may be used in the treatment of multiple-antibiotic-resistant bacterial strains. In a related study, the augmentation activity of clavulanic acid with penicillin or ticarcillin was evaluated against B. fragilis in a rat intra-abdominal abscess model. Gelatin capsules filled with a mixture of B. fragilis and Escherichia coli were implanted intraperitoneally in male Wistar rats. Four different groups of animals with appropriate controls were treated with penicillin or ticarcillin alone or in combination with clavulanic acid. Treatment was started immediately or delayed for 48 hours after peritoneal soilage. The mortality rate decreased by almost one half when antibiotic therapy was started immediately. Treatment with ticarcillin plus clavulanic acid resulted in a cure in 70 to 89 percent of animals, showing that this combination is the most effective regimen in the treatment of rats with experimental intra-abdominal abscesses caused by B. fragilis and E. coli.