Differential release of smooth-type lipopolysaccharide from Pseudomonas aeruginosa treated with carbapenem antibiotics and its relation to production of tumor necrosis factor alpha and nitric oxide

Release of large amounts of lipopolysaccharides from Pseudomonas aeruginosa cells reduces their susceptibility to colistin

Pseudomonas aeruginosa is an important etiological agent of opportunistic infections. Injectable colistin is available as a last-line treatment option for multidrug-resistant P. aeruginosa infections. When cells were inoculated at a high number, colistin-susceptible P. aeruginosa grew on agar medium containing colistin at a concentration 10-fold higher than the minimum inhibitory concentration without acquiring colistin resistance. This study examined the responsible mechanism for growth in the presence of a high concentration of colistin. Cell wash fluid derived from P. aeruginosa efficiently reduced colistin antimicrobial activity. This reduction was mediated by lipopolysaccharide (LPS) in the wash fluid. Extracellular LPS inhibited colistin activity more effectively than cell-bound LPS in fixed cells. Cell wash fluids from Escherichia coli and Acinetobacter baumannii also reduced colistin activity; however, they were less potent than those from P. aeruginosa. The amount of LPS in cell wash fluid from P. aeruginosa was approximately 10-fold higher than that in fluid from E. coli or A. baumannii. In conclusion, cell-free LPS derived from bacterial cells inhibited the antimicrobial activity of colistin, and this effect was greatest for P. aeruginosa. Thus, large amounts of broken and dead cells of P. aeruginosa at infection foci will reduce the effectiveness of colistin, even against cells that have not yet acquired resistance.

Multiplex PCR pathogen detection in two severely burned patients with suspected septicemia

The case studies reported in this article strive to illustrate the clinical value of multiplex polymerase chain reaction (PCR)-based pathogen detection in patients with burn sepsis. Adult (age ≥18 years) burn patients (≥20% TBSA) presenting with signs and symptoms of burn sepsis were enrolled into a prospective, observational trial. Patients received PCR testing in parallel to routine blood cultures. The authors report two cases in which PCR was used to rapidly detect pathogens in whole blood from burn patients with suspected septicemia. PCR identified Escherichia coli in 5.8 hours in case 1. Blood and sputum cultures required 17 hours for Gram stain results. Empiric ceftriaxone therapy was initiated. Blood cultures required an additional 18 hours to identify the same pathogen detected by PCR. Ceftriaxone was replaced with ciprofloxacin for improved coverage. Follow-up antimicrobial susceptibility results revealed intermediate ciprofloxacin resistance. Meropenam therapy was initiated. In case 2, PCR detected Pseudomonas aeruginosa in 5.45 hours while blood cultures remained negative. Respiratory cultures became positive for P. aeruginosa 2 days later. Serial PCR samples continued detecting P. aeruginosa despite negative blood cultures and appropriate antimicrobial therapy. The patient later became hypotensive and coagulopathic and expired. For both patient cases, PCR identified high-risk pathogens faster than culture methods. In the second patient case, PCR identified the presence of pathogen DNA despite negative cultures before the onset of septic shock and presumptive disseminated intravascular coagulation. These results warrant further investigation to determine the clinical significance of pathogen DNA in burn sepsis.

Therapeutic efficacy of mammary irrigation regimen in dairy cattle diagnosed with acute coliform mastitis

The objective of this field study was to determine the therapeutic efficacy of mammary irrigation for the treatment of dairy cattle diagnosed with acute coliform mastitis caused by gram-negative bacteria. Additionally, the effects of different mammary irrigation regimen fluids such as ozone water and normal saline were compared. Dairy cattle clinically diagnosed with acute coliform mastitis (n = 57) were enrolled in the study, randomly assigned to 1 of 3 groups, and received the following treatments: systemic antibiotic administration (SAA group; n = 40), mammary irrigation regimen (MIR group; n = 10), and both treatments (MIX group; n=7). Significant antipyretic effects, as assessed by rectal temperature measurement, were observed in the MIX and MIR groups. Although 2 irrigating fluids were used, namely, ozone water and normal saline, no significant difference was observed between the 2 groups. Fourteen days after the onset of the treatments, the milk yield recovery rate in MIR group tended to be higher (p = 0.06) than that in the SAA group. Additionally, after 30 days of treatment, the MIR group cows demonstrated significantly higher successful recovery rates (p<0.05) than the SAA group cows. These results indicate that mammary irrigation with normal saline is an effective treatment for acute coliform mastitis in dairy cattle.

Comparison of the amounts of endotoxin released from Escherichia coli after exposure to antibiotics and ozone: an in vitro evaluation

Antibiotic therapy administered for treatment of gram-negative bacterial infections can exert a negative effect in the form of endotoxin shock. Therefore, a sterilization method that releases little endotoxin is required. This in vitro study aimed to compare the amounts of endotoxin released from Escherichia coli exposed to antibiotics (aminobenzylpenicillin, kanamycin, oxytetracycline, sulfadimethoxine and enrofloxacin) or ozone. The bacterial growth and amount of endotoxin released were measured at specific time points. Compared with antibiotic treatment, ozone sterilization induced release of smaller amounts of endotoxin from the bacteria. Moreover, no major differences were observed when ozone was used against the purified endotoxin. We conclude that compared with antibiotic treatment, ozone sterilization may release smaller amounts of endotoxin.

The antibacterial activity against MRSA strains and other bacteria of a <500Da fraction from maggot excretions/secretions of Lucilia sericata (Diptera: Calliphoridae)

The application of Lucilia sericata larvae to chronic, infected wounds results in the rapid elimination of infecting microorganisms, including MRSA. Previously, we demonstrated in vitro antibacterial activity of native excretions/secretions (nES) from L. sericata and partially purified two low mass antibacterial compounds with masses of 0.5-10kDa and <500Da. The present study reports the antibacterial effects of the <500Da fraction (ES<500) on the growth and morphology of a range of bacteria, including 12 MRSA strains. Distinct morphological changes were observed in Bacillus cereus and Escherichia coli following exposure to ES<500. Flow cytometry and confocal microscopy analyses, in conjunction with turbidometric and CFU assays, revealed bacteriostatic activity of nES against S. aureus and E. coli. ES<500 also demonstrated bacteriostatic activity against S. aureus, however, bactericidal activity and the induction of a viable but non-culturable state were observed with ES<500-treated E. coli.

Antibiotic induced endotoxin release and clinical sepsis: a review

Sepsis and peritonitis have not lost much of their danger for patients. The mortality rate in peritonitis has only marginally decreased during the last 30 years despite aggressive surgical and sophisticated intensive care treatment. In intra-abdominal infection and peritonitis source control remains the mainstay of treatment, although general principles and denominators of successful source control need to be established. Endotoxin has been recognized as a major player in the pathogenesis of sepsis and its significance in clinical disease has been investigated in clinical studies for more than 20 years. Since the Sixties there is a growing interest in the effect of antibiotics and other compounds on the release of endotoxin. The effect of antibiotics on the release of endotoxin and inflammatory parameters, e.g., cytokines, remains to be clarified despite a growing body of in-vitro studies, animal studies and a few clinical studies. The purpose of this review is to evaluate the evidence of endotoxin release in clinical studies and the effect that antibiotic treatment may have in-vitro, in-vivo and in clinical studies on endotoxin and cytokine release. In-vitro antibiotic-induced endotoxin release may depend on antibiotic class, presence of serum, type of organism, site of antibiotic action and Gram-stain. Endotoxin release may be different in late or early lysis, proportional to the number of killed pathogens. Morphology of bacteria may have an impact on endotoxin release and phagocytosis. Antibiotic-treated animals may show higher endotoxin levels with a higher survival rate than untreated animals. Plasma endotoxin may increase despite decreasing bacteremia. There may be a similar killing rate by different antibiotics but a difference in endotoxin release. Intestinal endotoxin does not necessarily correlate to the level of gram-negative bacteria. However, the alteration of the gut content by pretreatment may be associated with reduced endotoxemia and increased survival. Antibiotic-induced endotoxin release may be different depending on the type of infection, the location of infection, the virulence of strains, Gram-stain, mode of application and dosage of antibiotic. Different antibiotics may induce the release of different forms of endotoxin which may be lethal for sensitized animals. The combination of antibiotics with inhibitors of endotoxin or the pro-inflammatory response may be responsible for increased survival by decrease of endotoxin release. The clinical significance of antibiotic-induced endotoxin release is documented only in a few clinical disorders, e.g., meningitis, urosepsis. The difference in endotoxin release by PBP 2-specific antibiotics, e.g., imipenem, and PBP 3-specific antibiotics, e.g., ceftazidime, may not be visible in each study. Patients with increased multi-organ failure (MOF) scores may profit from treatment with antibiotics known to decrease endotoxin. In conclusion, the clinical significance of antibiotic-induced endotoxin release remains to be clarified. Type of pathogen and its virulence may be more important than recently suggested. gram-positive pathogens were just recently recognized as an important factor for the development of the host response. In case of fever of unknown origin in intensive care patients either failure of treatment, e.g., failure of source control in intra-abdominal infection, or a side effect of antibiotic treatment, e.g., endotoxin release, should be considered as a cause of the fever.

Morphological change in Pseudomonas aeruginosa following antibiotic treatment of experimental infection in mice and its relation to susceptibility to phagocytosis and to release of endotoxin

The relationship between morphological changes in Pseudomonas aeruginosa following antibiotic treatment of experimental infection in mice, susceptibility to phagocytosis, and release of endotoxin was studied. The intraperitoneal administration of P. aeruginosa with imipenem or ceftazidime into mice induced morphological changes in the cells 2 h after injection. Round P. aeruginosa cells with imipenem treatment became susceptible to phagocytosis by peritoneal cells, whereas long filamentous cells with ceftazidime treatment were hardly phagocytized by peritoneal cells. The morphological changes also affected the plasma endotoxin level in the circulation.

Ecthyma gangrenosum in a patient with hypogammaglobulinemia

Ecthyma gangrenosum is a characteristic skin lesion that is caused by Pseudomonas aeruginosa (P. aeruginosa) in the majority of cases. Systemic P. aeruginosa usually complicates debilitating conditions like leukaemia, burns and cystic fibrosis. We report a patient with underlying hypogammaglobulinemia who developed ecthyma gangrenosum secondary to P. aeruginosa septicaemia, which was potentially life-threatening. Recognition of the characteristic skin lesions with prompt initiation of appropriate antibiotics and intravenous immunoglobulins were life-saving. A review of the English literature reports three other cases of ecthyma gangrenosum in patients with underlying hypogammaglobulinemia.

Low-level release of Shiga-like toxin (verocytotoxin) and endotoxin from enterohemorrhagic Escherichia coli treated with imipenem

Shiga-like toxin (SLT) and endotoxin may participate in the pathogenesis of enterohemorrhagic Escherichia coli (EHEC) infection. Levels of release of SLT and endotoxin from EHEC treated in vitro with antibiotics were estimated. There were differential levels of release of SLT and endotoxin from EHEC treated with different antibiotics. Treatment of EHEC strains, namely, E. coli O157, O111, and O26, with imipenem induced much lower levels of release of SLT and endotoxin than treatment with ceftazidime.

Differential induction of pro- and anti-inflammatory cytokines in whole blood by bacteria: effects of antibiotic treatment

The in vitro production of interleukin-1beta (IL-1beta), IL-6, and the IL-1 receptor antagonist (IL-1ra) in whole blood upon stimulation with different bacterial strains was measured to study the possible relationship between disease severity and the cytokine-inducing capacities of these strains. Escherichia coli, Neisseria meningitidis, Neisseria gonorrhoeae, Bacteroides fragilis, Capnocytophaga canimorsus, Staphylococcus aureus, Enterococcus faecalis, Streptococcus pneumoniae, and Streptococcus pyogenes induced the cytokines IL-1beta, IL-6, and IL-1ra. Gram-negative bacteria induced significantly higher levels of proinflammatory cytokine production than gram-positive bacteria. These differences were less pronounced for the anti-inflammatory cytokine IL-1ra. In addition, blood was stimulated with E. coli killed by different antibiotics to study the effect of the antibiotics on the cytokine-inducing capacity of the bacterial culture. E. coli treated with cefuroxime and gentamicin induced higher levels of IL-1beta and IL-6 production but levels of IL-1ra production similar to that of heat-killed E. coli. In contrast, ciprofloxacin- and imipenem-cilastatin-mediated killing showed a decreased or similar level of induction of cytokine production as compared to that by heat-killed E. coli; polymyxin B decreased the level of production of the cytokines.