Gram-negative Bacilli Bacteremia Research Articles

The Value of Serum Procalcitonin Level for Differentiation between Contaminants and Pathogens in Bacteremia

Background: Bacteremia is a life-threatening infection, and prognosis is highly dependent on early recognition and treatment with appropriate antimicrobial agents. We investigated the diagnostic performance of serum procalcitonin (PCT) for differentiation between contaminants and true pathogens in blood cultures. Methods: Serum PCT, C-reactive protein (CRP) and blood culture were performed for 473 patients between February 2008 and October 2008. We retrospectively reviewed the patients' clinical characteristics and laboratory results based on medical records. Results: The mean concentration of PCT was significantly different between the two negative and positive blood culture groups (6.45 ng/mL vs 28.77 ng/ mL, P<0.001). Procalcitonin levels were found to be markedly higher in those with Gram-negative bacilli (mean±SD; 59.58±67.00 ng/mL) bacteremia than in those with Gram-positive cocci (mean±SD; 17.75±42.88 ng/mL) bacteremia (P<0.001). The areas under the receiver operating characteristic curves (95% confidence interval) for PCT and CRP were 0.880 (0.820∼ 0.940) and 0.637 (0.538∼0.736), respectively. The use of a PCT level of 2 ng/mL as a cutoff value yielded an 83.6% positive predictive value and a 77.4% negative predictive value for the detection of bacteremia pathogens. Conclusion: Serum PCT is a helpful diagnostic marker for rapidly and accurately distinguishing between contaminants and pathogens in blood cultures. (Korean J Clin Microbiol 2011;14:7-12)

Bacteraemia due to multidrug-resistant Gram-negative bacilli in cancer patients: risk factors, antibiotic therapy and outcomes

To assess the risk factors, antibiotic therapy and outcomes of multidrug-resistant Gram-negative bacilli (MDRGNB) bacteraemia in hospitalized patients with cancer. Episodes of MDRGNB bacteraemia were compared with a susceptible control group in a 4 year prospective study. Of 747 bacteraemias, 372 (49.7%) were caused by a Gram-negative bacilli (GNB). Fifty-one of these (13.7%) were caused by a multidrug-resistant (MDR) strain. Previous antibiotics [odds ratio (OR) 3.57; 95% confidence interval (CI) 1.63-7.80] and urinary catheter (OR 2.41; 95% CI 1.01-5.74) were identified as independent risk factors for MDRGNB acquisition. The most frequent mechanism of resistance was extended-spectrum β-lactamase (ESBL) production (45%), mainly by Escherichia coli, followed by Amp-C cephalosporinase hyperproduction (24%). Patients with MDRGNB bacteraemia more frequently received inadequate initial antibiotic therapy (69% versus 9%; P < 0.001) and time to adequate therapy was longer in this group (41% versus 4%; P < 0.001). Patients in the resistant group more frequently required intensive care unit (ICU) admission (14% versus 5%; P = 0.023), had greater need for mechanical ventilation (14% versus 3%; P = 0.005) and had a higher overall case-fatality rate (41% versus 21%; P = 0.003). Risk factors for mortality were solid tumour (OR 5.04; 95% CI 2.49-10.19), current corticosteroid use (OR 4.38; 95% CI 2.39-8.05), ICU admission (OR 11.40; 95% CI 3.19-40.74) and MDRGNB bacteraemia (OR 3.52; 95% CI 1.36-9.09). MDRGNB bacteraemia was common among cancer patients, especially in those exposed to antibiotics and urinary catheter. The most frequent mechanism of resistance was ESBL production. Patients with MDRGNB more frequently received inadequate empirical antibiotic therapy and presented poorer outcomes with a higher overall case-fatality rate (within 30 days).

Viridans streptococci bacteraemia in children with fever and neutropenia: a case–control study of predisposing factors

Viridans streptococci (VS) are an increasing cause of bacteraemia in neutropenic patients with cancer. Case–control studies of predisposing factors for acquisition of this infection in children are not published. Between January 1989 and December 1999, 168 episodes of bacteraemia in 161 children with fever and neutropenia of haemato-oncology origin were analysed. 15 cases (9%) in 15 patients were caused by VS. Each case patient was compared with 6 matched control patients; 2 with other Gram-positive cocci (group 2), 2 with gram-negative bacilli bacteraemia (group 3) and two children with fever and neutropenia without bacteraemia (group 4). The median age of patients was 4.1 years (range: 2–15 years). 87% of children had acute leukaemia or lymphomas. Pneumonia was the predominant clinical focus (70%). Shock was observed in 13% of patients. ARDS was observed in one child who died of this complication. Multivariate analysis of risk factors for the development of VS bacteraemia showed that two factors were independent predictors: high doses of cytosine-arabinoside (ARA-C) as part of the chemotherapy treatment (Odds Ratio (OR): 9.3; Confidence Interval (CI) 1.56–55.5) (P<0.014) and the presence of pneumonia (OR: 1.36: CI 2.27–81.9) (P<0.0043). We propose that further studies are warranted to confirm these results.

The French National Registry of HA-1A (Centoxin) in septic shock. A cohort study of 600 patients. The National Committee for the Evaluation of Centoxin

Antiendotoxin monoclonal antibodies are under investigation as adjunctive therapy for severe sepsis. One of these antibodies (the human IgM monoclonal antibody HA-1A) was marketed in Europe during 1992 for treatment of patients with severe sepsis, especially those with shock, and probable gram-negative bacilli (GNB) bacteremia, after a placebo-controlled trial showed improved outcome in such patients. This cohort study was designed to assess characteristics and determinants of outcome of patients through a nationwide registry of all adult patients hospitalized in intensive care units of French hospitals and treated with HA-1A. Main outcome measures included (1) survival at 14 days, 28 days, and hospital discharge, with comparison of observed with expected hospital mortality according to the Acute Physiology and Chronic Health Evaluation II (APACHE II) score, and (2) analysis of risk factors for death using a Cox proportional hazards model. Of 600 patients who received HA-1A in a 1-year period, 75% had documented GNB infection and 39% had GNB bacteremia; 94% had hypotension and 54% had refractory shock. Crude overall mortality rates were 49% and 61.3% (P < 10(-4)) at day 14 after therapy and hospital discharge, respectively. Hospital mortality tended to be higher than expected from the APACHE II score (61.3% vs 56%, P = .06), especially in patients without GNB infection (68.1% vs 58.3%). Independent risk factors for death were the APACHE II score (P < 10(-4)), the number of organ system failures (P = 10(-4)), the prognosis of underlying disease (P = .001), and non-GNB infection (relative risk, 1.32 [95% confidence interval, 1.05 to 1.66]; P = .02). This cohort study did not confirm decreased mortality in patients with GNB bacteremia, as reported in the first placebo-controlled HA-1A trial, and it further suggests excess mortality in the subgroup of patients with non-GNB infection. In clinical trials of patients with severe sepsis, controlling for both the severity of acute illness score and the number of organ system failures, as well as for the severity of underlying disease and the source of infection, should be considered, especially when subgroups are analyzed.

The importance of surveillance stool cultures during periods of severe neutropenia.

The correlation of fecal gram-negative bacilli (GNB), neutropenia, and bacteremia was studied in 45 bone marrow transplant recipients. Weekly stool cultures were prospectively monitored for GNB resistant to routine prophylactic and empiric antimicrobial agents. Seven cases of GNB bacteremia occurred in 45 patients described as follows. Twenty-three patients had no fecal or blood GNB. Fifteen patients had fecal GNB and no blood GNB; three of these latter patients had less than or equal to 50/mm3 circulating white blood cells (WBC) at the time of isolation of fecal GNB but two of the three were concurrently receiving appropriate empiric antibiotics. Two patients had blood GNB but no fecal GNB: one patient had a trimethoprim/sulfamethoxazole (TMP-SMZ)-sensitive isolate that would not be detectable in the feces by our methodology and one patient had feces analyzed only after the bacteremic event. Five patients had fecal GNB and blood GNB: one of these patients did not have a fecal sample analyzed prior to bacteremia but the remaining four patients had the same species/antibiogram of GNB isolated from the feces two to three days prior to the detection of bacteremia. Thus, the fecal GNB could have been used to predict the antibiogram of the subsequent blood GNB. In addition, all four of these latter bacteremic patients had less than or equal to 50/mm3 circulating WBC at the time of documented fecal GNB. Thus, bone marrow transplant recipients with fecal GNB coupled with severe neutropenia (less than or equal to 50/mm3 circulating WBC) were more likely to develop bacteremia (P less than 0.02) than were those with fecal GNB and greater than 50/mm3 circulating WBC.