Enhancement of in vitro bactericidal activity of neutrophils from trauma patients in the presence of granulocyte colony-stimulating factor

Bactericidal activity response of blood neutrophils from critically ill patients to in vitro granulocyte colony-stimulating factor stimulation

OBJECTIVE

Neutrophil function impairment is common in nonneutropenic critically ill patients. Whether granulocyte colony-stimulating factor (G-CSF) may be useful for preventing nosocomial infection in these patients is debated. The response of blood neutrophils from critically ill patients to G-CSF was investigated in vitro.

DESIGN AND SETTING

Prospective study, laboratory investigation in two intensive care units.

PATIENTS

52 critically ill patients without immunosuppression.

MEASUREMENTS

Neutrophils obtained from 52 patients on the 5th day of their intensive care unit stay were incubated with and without G-CSF (1, 10, 100 ng/ml). Reactive oxygen species (ROS) release and bactericidal activity against Staphylococcus aureus and Pseudomonas aeruginosa were evaluated. Plasma cytokines (interleukin 10, tumor necrosis factor alpha, and G-CSF) were measured.

RESULTS

Median values (25th-75th percentiles) indicated no stimulatory effect of G-CSF on neutrophil bactericidal activity against either organism: S. aureus, 100% (95-109) of the unstimulated condition with 1 ng/ml G-CSF, and P. aeruginosa, 102% (98-109) with 1 ng/ml G-CSF. However, wide interindividual variability was found, ranging from marked inhibition to marked stimulation. Similar variability was found for ROS release. No correlations were found between ROS release and bactericidal activities against either bacterial strain. Inhibition of neutrophil bactericidal activity by G-CSF was associated with significantly higher plasma interleukin 10 concentrations. Plasma G-CSF levels were significantly higher in patients whose neutrophil bactericidal activity was unresponsive to G-CSF, suggesting G-CSF receptor downregulation.

CONCLUSIONS

The effect of G-CSF on in vitro neutrophil bactericidal activity varied widely, depending on endogenous levels of G-CSF and was not predictable based on severity scores.

Impairment of polymorphonuclear neutrophil functions precedes nosocomial infections in critically ill patients

OBJECTIVE

A postinjury immunodepression involving neutrophil functions has been described in critically ill patients. The aim of this prospective study was to search for a relationship between an impairment of neutrophil functions and the subsequent development of nosocomial infection.

DESIGN

Twenty-one severely ill (simplified acute physiology score II >20 on admission), nonimmunosuppressed patients who were receiving no antibiotics active against methicillin-resistant Staphylococcus aureus and highly resistant Pseudomonas aeruginosa were included. Twelve healthy subjects constituted a control group.

MEASUREMENTS

Neutrophil functions (phagocytosis and bactericidal activity toward S. aureus and P. aeruginosa in homologous plasma, reactive oxygen species secretion) were studied at day 4 +/- 1 after admission, and occurrence of nosocomial infection was prospectively recorded over the following 5 days. Interleukin-10 concentration was assessed by enzyme-linked immunosorbent assay. Results are expressed as median (25th-75th percentiles).

MAIN RESULTS

Six out of the 21 patients acquired a nosocomial infection during the 5 days after blood sampling (infected group). Compared with the patients who did not acquire nosocomial infection (noninfected group, n = 15), the neutrophils of the infected group demonstrated a higher percentage of intracellular bacterial survival (17% [2% to 67%] vs. infected: 62% [22% to 100%], p <.05), leading to an impairment of S. aureus killing in homologous plasma (killed bacteria: 4.93 log(10) colony forming units/mL [4.24-5.29] vs. infected: 3.62 log(10) colony forming units/mL [0.00-4.58], p <.05). Interleukin-10 plasma concentration was higher in infected patients (78 pg/mL [60-83]) compared with noninfected patients (22 pg/mL [14-58], p <.05). By contrast, P. aeruginosa killing was similar in patients whether or not they acquired a nosocomial infection.

CONCLUSION

A decrease in S. aureus killing capabilities of neutrophils can be evidenced within the days before occurrence of a nosocomial infection.

Granulocyte colony-stimulating factor improves host defense to resuscitated shock and polymicrobial sepsis without provoking generalized neutrophil-mediated damage

BACKGROUND

Granulocyte colony-stimulating factor (G-CSF) increases production and release of neutrophil precursors and activates multiple functions of circulating polymorphonuclear neutrophils (PMNs). G-CSF has therapeutic effects in many experimental models of sepsis; its actions with superimposed reperfusion insults are unknown. In traumatic conditions, G-CSF could exacerbate unregulated, PMN-dependent injury to otherwise normal host tissue or, it could partially reverse trauma-induced immune suppression, which may improve long-term outcome. This study tested whether stimulating PMN proliferation and function with G-CSF during recovery from trauma+sepsis potentiated reperfusion injury or whether it improved host defense.

METHODS

Anesthetized swine were subjected to cecal ligation and incision, 35% hemorrhage, and 1 hr of hypotension. Resuscitation consisted of intravenous G-CSF (5 microg/kg) or placebo followed by shed blood and 40 mL/kg of lactated Ringer's solution. The control group received laparotomy only. G-CSF or placebo was given daily. Animals were killed at 4 days. Observers, blind to the protocol, graded autopsy samples for localization of infection and quality of abscess wall formation. Data included complete blood count, granulocyte oxidative burst after phorbol myristate acetate stimulation in vitro (GO2B), bronchoalveolar lavage (BAL) cell count, BAL noncellular protein, lipopolysaccharide-stimulated tumor necrosis factor production in whole blood in vitro (lipopolysaccharide-tumor necrosis factor), and lung tissue myeloperoxidase (MPO).

RESULTS

Neutrophilia and localization of infection, were significantly improved by G-CSF. Variables altered by G-CSF, though not significantly, showed GO2B potential increased by 50%, lipopolysaccharide-tumor necrosis factor decreased by 50%, and improved survival versus placebo (100% vs. 70%). G-CSF did not increase lung MPO, BAL cell count, or BAL protein. Both arterial and venous O2 saturations were unaltered.

CONCLUSIONS

Our data show that G-CSF initiated at the time of resuscitation reduced the sequelae of posttrauma sepsis by increasing PMN proliferation and function without potentiating PMN-mediated lung reperfusion injury.

The pathogenesis of Staphylococcus aureus in the trauma patient and potential future therapies

BACKGROUND

Staphylococcus aureus is the most frequently isolated pathogen in the trauma patient and uses multiple virulent factors to cause infection. At the cellular level, infection begins with the prokaryotic bacterial cell manipulating the eukaryotic host cell through its virulent factors. Researching this cellular interaction by describing the mechanisms of actions of various virulent factors may lead to new preventive therapies which will make the trauma patient less susceptible to S aureus infections.

METHODS

Surgical, medical, and microbial literature was reviewed to provide an update on S aureus pathogenesis.

RESULTS

Novel future therapies, in addition to antibiotics, are being devised based on understanding the molecular nature of S aureus pathogenesis.

CONCLUSION

The impact of S aureus on trauma will increase as S aureus develops more antibiotic resistance and as the trauma population becomes older and includes an increasing proportion of immunocompromised patients. To meet the challenge of increased virulence, trauma surgeons should be directly involved in the research of microbial pathogenesis.

Synergy of simultaneous administration of ofloxacin and granulocyte colony-stimulating factor in killing of Escherichia coli by human neutrophils

The in vitro effect of subinhibitory and inhibitory concentrations of ofloxacin and G-CSF on the bactericidal activity of polymorphonuclear leucocytes (PMNL) against Escherichia coli was investigated. PMNL obtained from healthy volunteers were incubated with different concentrations of G-CSF and ofloxacin for 180 min. The minimum inhibitory concentration (MIC) of ofloxacin and even 1/4 x MIC enhanced the bactericidal activity of PMNL. G-CSF at a concentration of 6,000 units/ml led to a significant improvement of the bactericidal activity of PMNL. The combination of 6,000 units/ml of G-CSF and ofloxacin in inhibitory as well as subinhibitory concentrations, however, showed a significant synergistic effect on the antibacterial activity of PMNL during the complete incubation period. Combinations of G-CSF and antibiotics could therefore be beneficial for infected patients, especially those with impaired cellular host defense.

Combined effect of human neutrophils, ceftazidime and granulocyte colony-stimulating factor on killing of Escherichia coli

The combination effect of subinhibitory and inhibitory concentrations of ceftazidime, granulocyte colony-stimulating factor (G-CSF) and polymorphonuclear leukocytes (PMNL) against Escherichia coli was investigated. PMNL obtained from healthy volunteers were incubated with different concentrations of G-CSF and ceftazidime for 180 min. The addition of 0.25 x MIC of ceftazidime or 1 x MIC significantly enhanced the bactericidal activity of PMNL. G-CSF at a concentration of 6,000 units/ml led to only a slight improvement in the bactericidal activity of PMNL. The combination of 6,000 units/ml G-CSF and ceftazidime in inhibitory as well as subinhibitory concentrations, however, showed a significant synergistic effect (p < 0.01) on the antibacterial activity of PMNL during the entire incubation period. Combinations of G-CSF and antibiotics could therefore be beneficial for infected patients, especially those with impaired cellular host defence.