cefepime and Peritonitis

Topics: Abdomen; Bacterial Infections; Cefepime; Cephalosporins; Cholecystitis; Gastrointestinal Diseases; Peritonitis; Surgical Wound Infection

Topics: Cefepime; Cephalosporins; Humans; Peritonitis; Surgical Wound Infection

Topics: Bacterial Infections; Cefepime; Cephalosporins; Gram-Negative Bacteria; Gram-Positive Bacteria; Humans; Microbial Sensitivity Tests; Neutropenia; Peritonitis

Compared to combination therapy, intraperitoneal (IP) cefepime monotherapy for continuous ambulatory peritoneal dialysis (CAPD)-associated peritonitis may provide potential benefits in lowering staff burden, shortening time-consuming antibiotic preparation, and reducing bag contamination risk. This study sought to evaluate whether cefepime monotherapy is noninferior to combination regimens.. Multicenter, open-label, noninferiority, randomized, controlled trial.. Adult incident peritoneal dialysis (PD) patients with CAPD-associated peritonitis in 8 PD centers in Thailand.. Random assignment to either IP monotherapy of cefepime, 1g/d, or IP combination of cefazolin and ceftazidime, 1g/d, both given as continuous dosing.. Primary end point: resolution of peritonitis at day 10 (primary treatment response).. initial response (day 5), complete cure (relapse/recurrence-free response 28 days after treatment completion), relapsing/recurrent peritonitis, and death from any cause. Noninferiority would be confirmed for the primary outcome if the lower margin of the 1-sided 95% CI was not less than-10% for difference in the primary response rate. A 2-sided 90% CI was used to demonstrate the upper or lower border of the 1-sided 95% CI.. There were 144 eligible patients with CAPD-associated peritonitis, of whom 70 and 74 patients were in the monotherapy and combination-therapy groups, respectively. Baseline demographic and clinical characteristics were not different between the groups. The primary response was 82.6% in the monotherapy group and 81.1% in the combination-therapy group (treatment difference, 1.5%; 90% CI, -9.1% to 12.1%; P=0.04). There was no significant difference in the monotherapy group compared with the combination-therapy group in terms of initial response rate (65.7% vs 60.8%; treatment difference, 4.9%; 95% CI, -10.8% to 20.6%; P=0.5) and complete cure rate (80.0% vs 80.6%; treatment difference, -0.6%; 95% CI, -13.9% to 12.8%; P=0.7). Relapsing and recurrent peritonitis occurred in 4.6% and 4.6% of the monotherapy group and 4.2% and 5.6% of the combination-therapy group (P=0.9and P=0.8, respectively). There was nominally higher all-cause mortality in the monotherapy group (7.1% vs 2.7%; treatment difference, 4.4%; 95% CI, -2.6% to 11.5%), but this difference was not statistically significant (P = 0.2).. Not double blind.. IP cefepime monotherapy was noninferior to conventional combination therapy for resolution of CAPD-associated peritonitis at day 10 and may be a reasonable alternative first-line treatment.. This study is supported by The Kidney Foundation of Thailand (R5879), Thailand; Rachadaphiseksompotch Fund (RA56/006) and Rachadaphicseksompotch Endorsement Fund (CU-GRS_61_06_30_01), Chulalongkorn University, Thailand; National Research Council of Thailand (156/2560), Thailand; and Thailand Research Foundation (IRG5780017), Thailand.. Registered at ClinicalTrials.gov with study number NCT02872038.

Topics: Anti-Bacterial Agents; Cefazolin; Cefepime; Ceftazidime; Dose-Response Relationship, Drug; Drug Therapy, Combination; Female; Follow-Up Studies; Humans; Injections, Intraperitoneal; Male; Middle Aged; Peritoneal Dialysis, Continuous Ambulatory; Peritonitis; Prospective Studies; Treatment Outcome

Spontaneous bacterial peritonitis (SBP), in the presence of bacterial resistance or failure of third generation cephalosporins (3rd GC) has poor outcome. Empirical antibiotic(s) options are limited in these scenarios.. Consecutive cirrhotics with SBP because of hospital acquired SBP (>48 h of admission), microbial resistance or non-response (no resolution of SBP at 48 h) were randomized to Cefepime (n = 88) or Imipenem (n = 87) plus standard medical therapy. We assessed for 'response at 48 h' (reduction in ascitic fluid absolute neutrophil count (ANC) by >25% at 48 h), resolution of SBP (<250 cu/mm ANC at day 5) and their clinical outcome.. Of 957 paracentesis in 1200 hospitalized cirrhotics, 253 (26.4%) had SBP and 175 (69.6%) were randomized. Baseline parameters were comparable in two groups. Response at 48 h (58.6% vs. 51.7%; P = 0.4) and resolution of SBP in those with response at 48 h were comparable with no difference in mortality at week 2, month 1 and 3. Patients with 'No response at 48 h' had higher mortality compared with responders (73.8% vs. 25%; P < 0.001). Resolution of SBP was associated with 'response at 48 h' and septic shock, latter being main pre-terminal event. AKI at enrolment [Hazard ratio (HR), 2.6], pneumonia [HR, 2.9], septic shock [HR, 2.2] and response at 48 h [HR, 4.6] predicted poor outcome.. In hospitalized cirrhotics with SBP and risk factors for treatment failure, cefepime showed comparable efficacy and survival to imipenem. Non-response to therapy at 48 h is a reliable predictor of treatment failure and mortality. Antibiotic combinations and novel options are needed for these patients.

Topics: Adult; Anti-Bacterial Agents; Ascitic Fluid; Bacterial Infections; Cefepime; Cephalosporins; Cross Infection; Drug Resistance, Multiple; Drug Therapy, Combination; Female; Humans; Imipenem; India; Liver Cirrhosis; Male; Middle Aged; Paracentesis; Peritonitis; Risk Factors; Severity of Illness Index; Survival Analysis; Time Factors

Comparative estimation of the treatment result of severe abdominal infection, using cefalosporins of the fourth generation maxipim and Quadrocef (Arterium, Ukraine) was accomplished. High efficacy of Quadrocef preparation and possibility of its application as a first-line preparation for severe infections was proved.

Topics: Adult; Aged; Anti-Bacterial Agents; APACHE; Cefepime; Cephalosporins; Digestive System Diseases; Female; Humans; Male; Middle Aged; Peritonitis; Postoperative Complications; Sepsis; Treatment Outcome

The safety and efficacy of cefepime empiric monotherapy compared with standard broad-spectrum combination therapy for hospitalized adult patients with moderate to severe community-acquired bacterial infections were evaluated. In an open-label, multicenter study, 317 patients with an Acute Physiology and Chronic Health Evaluation (APACHE II) score ranging from >5 to =19 were enrolled with documented pneumonia (n=196), urinary tract infection (n=65), intra-abdominal infection (n=38), or sepsis (n=18). Patients were randomly assigned 1:1 to receive cefepime 1 to 2 g IV twice daily or three times a day or IV ampicillin, cephalothin, or ceftriaxone +/-aminoglycoside therapy for 3 to 21 days. For both treatment groups, metronidazole, vancomycin, or macrolide therapy was added as deemed necessary. The primary efficacy variable was clinical response at the end of therapy. Two hundred ninety-six (93%) patients met evaluation criteria and were included in the efficacy analysis. Diagnoses included the following: 180 pneumonias (90 cefepime, 90 comparator), 62 urinary tract infections (29 cefepime, 33 comparator), 37 intra-abdominal infections (19 cefepime, 18 comparator), and 17 sepses (8 cefepime, 9 comparator). At the end of therapy, overall clinical success rates were 131/146 (90%) for patients treated with cefepime vs 125/150 (83%) for those treated with comparator (95% confidence interval [CI]: -2.6% to 16.3%). The clinical success rate for patients with community-acquired pneumonia, the most frequent infection, was 86% for both treatment groups. Among the patients clinically evaluated, 162 pathogens were isolated and identified before therapy. The most commonly isolated pathogens were Escherichia coli (n=49), Streptococcus pneumoniae (n=29), Haemophilus influenzae (n=14), and Staphylococcus aureus (n=11). Bacteriologic eradication/presumed eradication was 97% for cefepime vs 94% for comparator-treated patients. Drug-related adverse events were reported in 16% of cefepime patients and 19% of comparator patients. In conclusion, cefepime had higher cure rates compared with broad-spectrum combination therapy as an initial empiric treatment for hospitalized patients with moderate to severe community-acquired infections, including urinary tract infections, intra-abdominal infections, and sepsis.

Topics: Abdominal Abscess; Adolescent; Adult; Aged; Aged, 80 and over; Cefepime; Cephalosporins; Community-Acquired Infections; Drug Therapy, Combination; Female; Humans; Male; Middle Aged; Peritonitis; Pneumonia, Bacterial; Prospective Studies; Sepsis; Severity of Illness Index; South America; Treatment Outcome; Urinary Tract Infections

Cefepime is a cephalosporin with a broad spectrum of activity against most gram-positive and gram-negative pathogens. In this study, we attempted to compare the safety and efficacy of cefepime monotherapy against the potentially more toxic combination of vancomycin and netilmicin in the treatment of continuous ambulatory peritoneal dialysis (CAPD)-associated bacterial peritonitis. Eighty-one consecutive CAPD patients who presented with peritonitis from January 1, 1998, to June 30, 2000, were recruited for study. Patients were randomized to be administered either intraperitoneal (IP) cefepime, 1 g once daily (group A), or intravenous vancomycin and netilmicin at conventional doses (group B) for 10 days. Bacterial growth was obtained in 52 episodes (66%), and pathogens identified included gram-positive organisms (30 episodes; 38%), gram-negative organisms (14 episodes; 18%), mixed organisms (2 episodes; 2.5%), and fungus (6 episodes; 8%). Eight patients were excluded after randomization for various reasons (6 patients, fungal peritonitis; 2 patients, wrong diagnoses). Because of the relatively low peritonitis rate after the use of a disconnect system, the sample size of this study was relatively small, giving a power of 0.45. There were no significant differences in primary response rates and cure rates (no relapse >28 days after completion of antibiotic therapy) between both groups of patients (group A versus group B, 82% [32 of 39 patients] versus 85% [29 of 34 patients] and 72% [28 of 39 patients] versus 76% [26 of 34 patients], respectively; P = not significant). No significant side effect was encountered in either group. Total peritonitis-related hospitalizations were 84 patient-days (1, 7, 8, 11, 20, and 37 patient-days) and 115 patient-days (3, 6, 9, 14, 21, 21, and 41 patient-days), whereas total costs per patient cure were estimated to be US $1,039 and US $1,371 in groups A and B, respectively. We conclude that once-daily 1-g IP cefepime monotherapy is a simple, safe, and cost-effective alternative to vancomycin and netilmicin therapy in the treatment of CAPD-associated bacterial peritonitis.

Topics: Adult; Aged; Anti-Bacterial Agents; Cefepime; Cephalosporins; Female; Gentamicins; Gram-Negative Bacteria; Gram-Positive Bacteria; Humans; Male; Middle Aged; Netilmicin; Peritoneal Dialysis, Continuous Ambulatory; Peritonitis; Prospective Studies; Treatment Outcome; Vancomycin

The efficacy of cefepime in the treatment of 46 patients operated for general peritonitis of various genesis and severity (APACHE II not greater than 35) was studied. Cefepime was used in a dose of 2 g administered every 12 hours as slow intravenous infusions in 0.9 per cent sodium chloride solution in combination with metronidazole administered intravenously in a dose of 7.5 mg/kg body weight. The treatment course was 4 to 15 days. 45 patients were given diflucan for the prophylaxis of fungal superinfection, 3 patients were given aminoglycoside antibiotics (netilmicin or amikacin) and 2 patients were given vancomycin per os. The favourable clinical effect of the cefepime therapy was stated in 38 patients (82.6 per cent) including 4 out of 10 patients with initial APACHE II > 15. 101 isolates of aerobic gram-negative and gram-positive microbes from 38 patients treated with cefepime in combination with metronidazole were tested to estimate the bacteriological efficacy of the therapy and it was shown that only 5.9 per cent of them was resistant. The pathogen eradication was stated in 84.2 per cent of the patients.

Topics: Abdomen; Aged; Anti-Infective Agents; APACHE; Cefepime; Cephalosporins; Drug Therapy, Combination; Female; Humans; Male; Metronidazole; Middle Aged; Peritonitis; Prospective Studies; Sepsis; Surgical Wound Infection; Time Factors

To evaluate the safety and efficacy of cefepime hydrochloride plus metronidazole vs the combination of imipenem and cilastatin sodium in the treatment of complicated intra-abdominal infections in adult patients.. Prospective, randomized, double-blind multicenter study.. University-affiliated hospitals in the United States and Canada.. Three hundred twenty-three patients with complicated intra-abdominal infections in whom an operative procedure or percutaneous drainage was required for diagnosis and management.. Cefepime, 2 g, was administered intravenously every 12 hours (n= 164) in addition to metronidazole, 500 mg (or 7.5 mg/kg) intravenously every 6 hours. Imipenen-cilastatin sodium, 500 mg, was administered intravenously every 6 hours (n= 159). Surgical infection management was determined by the patients' surgeons. MAIN OUTCOME ASSESSMENTS: Clinical cure, defined as elimination of all signs and symptoms relevant to the original infection; and treatment failure, defined as persistence, increase or worsening of signs and symptoms resulting in an antibiotic change, requirement of an additional surgical procedure to cure the infection, or a wound infection with fever.. Of the initial isolates, 84% were susceptible to cefepime and 92% were susceptible to imipenem-cilastatin. Among the 217 protocol-valid patients, those treated with cefepime+metronidizole were deemed clinical cures (88%) more frequently than were imipenem-cilastatin-treated patients (76%) (P=.02). Using multivariate analysis to adjust for identified clinical risk factors for an adverse outcome (severity of presenting illness, isolation of enterococcus, type of infection, and duration of prestudy hospitalization), there was a trend (P=.06) toward a higher cure rate favoring cefepime+metronidazole. Pathogens were eradicated in significantly (P=.01) more patients treated with combined cefepime and metronidazole (89%) than with imipenem-cilastatin (76%).. The combination of cefepime plus metronidazole is safe and effective therapy for patients with severe intra-abdominal infections.

Topics: Abdomen; Abdominal Abscess; Adult; Aged; Antitrichomonal Agents; Appendicitis; Cefepime; Cephalosporins; Cilastatin; Double-Blind Method; Drug Therapy, Combination; Female; Gastrointestinal Diseases; Humans; Imipenem; Infections; Male; Metronidazole; Middle Aged; Peritonitis; Treatment Outcome

Topics: Cefazolin; Cefepime; Ceftazidime; Humans; Peritoneal Dialysis; Peritoneal Dialysis, Continuous Ambulatory; Peritonitis

Peritoneal dialysis (PD)-associated peritonitis is treated by administration of antibiotics mixed with the PD solution. Data on antibiotic stability for solutions in current use are limited. The aim of this study was to determine the stability of cefepime, cephazolin and ampicillin in three commercial PD solutions.. Antibiotics were added to the non-glucose compartment of the Gambro (Gambrosol®) and Fresenius (Balance®) multi-compartment systems and Baxter (Dianeal®) single-compartment (glucose 2.5%) PD solutions in a sterile suite. Antibiotic stability over 3 weeks was determined using both a bioassay of bacterial inhibition and antibiotic concentrations. The influence on stability and sterility of storage conditions was determined.. The bioassay demonstrated the stability of all antibiotics for 9 days at room temperature and 3 weeks when refrigerated, except ampicillin in the Gambro solution, which displayed no bioactivity after 4 days. However, a ceiling effect in bacterial inhibition at higher antibiotic concentrations limited the ability of the bioassay to detect antibiotic degradation at relevant concentrations. Antibiotic concentrations varied with time but were comparable to the bioassay and supported stability in refrigerated solutions, except ampicillin in the Gambro solution. No bacterial contamination, marked colour change or precipitation occurred.. This study supports the stability of cephazolin and cefepime in all three PD solutions and ampicillin in only the Baxter and Fresenius PD solutions. Antibiotic stability studies should ideally be conducted prior to registration and marketing of new PD solutions.

Topics: Ampicillin; Anti-Bacterial Agents; Bacteria; Cefazolin; Cefepime; Cephalosporins; Chemistry, Pharmaceutical; Dialysis Solutions; Drug Stability; Drug Storage; Humans; Peritoneal Dialysis; Peritonitis

The aim of this research is to evaluate the recent changes in microorganisms causing spontaneous bacterial peritonitis in cirrhotic patients, antibiotic resistance, and response to empirical cephalosporin therapy. A total of 218 patients with ascites secondary to cirrhosis were enrolled. Parenteral cefotaxime or cefepime was given to patients who had a neutrophil count of 250/mm(3) or more or a positive bacterial culture of ascitic fluid. Antibiotic failure was defined by an absence of clinical improvement and an insufficient decrease in neutrophil count of ascites (<25% of initial value) by the third day of therapy. Of all the patients, 44.6% had culture-negative neutrocytic ascites, 24.8% had spontaneous bacterial peritonitis, and 10.1% had monomicrobial nonneutrocytic bacterascites. Growth in culture was observed in 76 patients (34.9%). The two most common isolated bacteria were Escherichia coli (33.8%) and coagulase-negative Staphylococcus (CoNS; 19.7%). The two cephalosporins were effective against E. coli (82%) and but not against CoNS (44%), while levofloxacin showed reasonable activity against both E. coli (71%) and CoNS (90%) in vitro. We confirmed a recent increased incidence of spontaneous bacterial peritonitis caused by Gram-positive bacteria. Levofloxacin seems to be a good alternative treatment for patients with uncomplicated spontaneous ascites infections.

Topics: Adult; Aged; Aged, 80 and over; Anti-Bacterial Agents; Ascitic Fluid; Bacterial Infections; Cefepime; Cefotaxime; Cephalosporins; Drug Resistance, Bacterial; Enterococcus; Escherichia coli Infections; Female; Humans; Infusions, Intravenous; Klebsiella Infections; Klebsiella pneumoniae; Leukocyte Count; Levofloxacin; Liver Cirrhosis; Male; Microbial Sensitivity Tests; Middle Aged; Neutrophils; Ofloxacin; Peritonitis; Pneumococcal Infections; Pseudomonas aeruginosa; Pseudomonas Infections; Staphylococcal Infections

This study aimed to examine the peritoneal pharmacokinetics of cefepime and to assess its pharmacodynamic exposure in peritoneal fluid (PF). Cefepime (1 g) was administered to eight patients with inflammatory bowel disease before abdominal surgery. Venous blood and PF samples were obtained at the end of the 0.5-h infusion and at 1, 2, 3, 4, 5, and 6 h thereafter. Drug concentrations in plasma and PF were determined, analyzed pharmacokinetically, and used for a Monte Carlo simulation with minimum inhibitory concentration (MIC) data. Cefepime penetrated well into PF, with a maximum drug concentration in a PF/plasma ratio of 0.59 +/- 0.15 (mean +/- SD, n = 8), and an area under the concentration-time curve ratio of 0.90 +/- 0.10. The probabilities of attaining the bacteriostatic and bactericidal targets (40% and 70% of the time above the MIC, respectively) in PF were > or =85% against Escherichia coli, Klebsiella species, and Enterobacter cloacae with 0.5 g every 12 h, 1 g every 12 h, 1 g every 8 h, and 2 g every 12 h. However, 1 g every 8 h or 2 g every 12 h was required for bacteriostatic and bactericidal probabilities > or =85% against Pseudomonas aeruginosa. These conventional regimens did not achieve a high probability against Bacteroides species. These results should help to give us a better understanding of the peritoneal pharmacokinetics of cefepime while also helping to choose the appropriate dosage to prevent surgical intra-abdominal infections on the basis of the pharmacodynamic assessment.

Topics: Abdomen; Adult; Aged; Anti-Bacterial Agents; Ascitic Fluid; Bacteria, Aerobic; Cefepime; Cephalosporins; Female; Humans; Inflammatory Bowel Diseases; Male; Microbial Sensitivity Tests; Monte Carlo Method; Peritonitis

Intraperitoneal (IP) administration of either streptokinase (SK) or urokinase (UK) has assumed an adjunctive role to antibiotic therapy in selected patients with relapsing peritonitis. In these circumstances, bacteria may be protected from antibiotics through sequestration in either fibrinous structures or biofilms within the lumen of the peritoneal dialysis (PD) catheter or the peritoneal cavity. In some cases, it appears that disruption of these sheltered microenvironments by thrombolytic agents facilitated eradication of the offending organism and obviated the need for catheter removal, replacement, or interim hemodialysis. Although IP SK has been generally well tolerated as additive therapy in relapsing peritonitis, sporadic reports of significant complications, such as abdominal pain, fever, and severe hypotension, have precluded its more widespread acceptance. The only other thrombolytic agent used in this setting, UK, is presently unavailable because of a manufacturing shortfall. Therefore, adjunctive thrombolytic therapy for relapsing peritonitis is currently restricted. To circumvent these limitations, we devised an IP tissue plasminogen activator (tPA) protocol to eliminate recurring infection in a patient undergoing chronic ambulatory PD. After a third episode of peritonitis caused by Enterobacter cloacae, treated twice previously with an adequate antibiotic regimen, we instilled 6 mL of tPA (1 mg/mL) into the PD catheter for a 2-hour dwell time. The treatment was well tolerated and, in conjunction with a third course of antibiotic therapy, has produced an infection-free interval of 8 months.

Topics: Adult; Cefepime; Cephalosporins; Ciprofloxacin; Drug Therapy, Combination; Gentamicins; Humans; Injections, Intraperitoneal; Male; Peritoneal Dialysis, Continuous Ambulatory; Peritonitis; Recombinant Proteins; Recurrence; Remission Induction; Tissue Plasminogen Activator; Vancomycin

The purpose of this study was to compare the effect, both in vitro and in vivo, of cefepime with those of four other cephalosporins, namely ceftriaxone, cefotaxime, cefuroxime and cephalothin, against penicillin-resistant pneumococci. One hundred pneumococcal strains, 31 penicillin-susceptible, 30 penicillin-intermediate-resistant and 39 penicillin-resistant pneumococci, were used in MIC studies. Time-kill experiments were carried out for four strains. In the mouse peritonitis model, the dose that gave protection to 50% of mice challenged with a lethal dose of pneumococci (ED50) was determined for three pneumococci and five cephalosporins. The MICs of all five cephalosporins and penicillin correlated significantly with each other. In vitro, the most potent cephalosporins against pneumococci were cefotaxime, ceftriaxone and cefepime, followed by cefuroxime and cephalothin. In time-kill experiments, carried out for four pneumococci, no differences were found in the killing effect of these five cephalosporins in relation to MICs. In the mouse peritonitis model, there was no significant correlation between log(MIC) and log(ED50) for the five cephalosporins against three pneumococci (Spearman's rho = 0.39, P = 0.16). However, if the values for cefepime against the three pneumococci were excluded, there was a significant correlation for the remaining four cephalosporins (Spearman's rho = 0.62, P = 0.04). For all three pneumococci, the ED50s of cefepime were lower than expected from the MICs. It was not possible to explain this beneficial difference in the effect of cefepime in terms of in-vitro bactericidal activities, serum protein binding or pharmacodynamic parameters.

Topics: Animals; Blood Proteins; Cefepime; Cephalosporins; Half-Life; Mice; Mice, Inbred Strains; Microbial Sensitivity Tests; Penicillin Resistance; Peritonitis; Pneumococcal Infections; Streptococcus pneumoniae; Time Factors

Resistance emerging after ceftazidime or cefepime therapy was investigated in a peritonitis model. Mice were given a peritoneal challenge (10(8) cfu plus talcum) and treated by either antibiotic (50 mg/kg/dose, which produced similar antibiotic concentrations in peritoneal fluid in both cases). After one or three doses, resistance never developed in Serratia marcescens or Citrobacter freundii infections. After Enterobacter cloacae and Pseudomonas aeruginosa challenge, ceftazidime selected more resistance (21/36 cases) than did cefepime (1/36 cases). In mice challenged with resistant strains selected by ceftazidime therapy, cefepime (six doses) successfully treated 7/18 E. cloacae infections but 0/18 P. aeruginosa infections; ceftazidime was never effective. Neither cefepime nor ceftazidime cured mice infected with the resistant strain selected by cefepime. MICs were poor predictors of further emergence of resistance in mice inoculated with strains classified as susceptible, but antibiotic-containing agar gradients plated with a high inoculum (10(8) cfu) allowed better prediction. In selected clinical situations, cefepime may be preferable because it may be associated with less frequent emergence of resistance.

Topics: Animals; Cefepime; Ceftazidime; Cephalosporins; Citrobacter freundii; Disease Models, Animal; Drug Resistance, Microbial; Enterobacter cloacae; Enterobacteriaceae Infections; Female; Mice; Mice, Inbred ICR; Microbial Sensitivity Tests; Peritonitis; Pseudomonas aeruginosa; Pseudomonas Infections; Serratia Infections; Serratia marcescens; Virulence