Bacterial interaction and indirect pathogenesis of Pseudomonas aeruginosa at the growth of MRSA

Bacterial interactions such as methicillin-resistant Staphylococcus aureus (MRSA) growth inhibition or inactivation of anti-MRSA antibiotics by Pseudomonas aeruginosa as an indirect pathogen were tested by in vitro assay. Paired strains, P. aeruginosa and MRSA, used in this experiment were isolated from 63 respiratory samples at Juntendo University Hospital from 2002 to 2003. Growth inhibitory activities against MRSA by P. aeruginosa were tested with reversed agar plate method. Inactivation of anti-MRSA antibiotics by P. aeruginosa were assayed with disk diffusion method using agar over lay technique. Fifty-six (88.9%) out of 63 samples showed the significant MRSA growth inhibitory activity by co-existed P. aeruginosa. Anti-MRSA antibiotics such as trimetoprim-sulfamethoxazole combination (ST), arbekacin (ABK) and minocycline (MINO) except Vancomycin (VCM) and Teicoplanin (TEIC) were inactivated by the co-existed P. aeruginosa. Our data suggests that P. aeruginosa may play not only as a chronic respiratory pathogen but also as an indirect pathogen. Further, the most P. aeruginosa with anti-MRSA activity isolated respiratory sample may play as a modulator of MRSA infection.     

In vitro activities of antibiotic combinations against clincal isolates of Pseudomonas aeruginosa

Combination therapy has been recommended to treat Pseudomonas aeruginosa infections worldwide. The purpose of the present study was to determine the in vitro activities of piperacillin, cefepime, aztreonam, amikacin, and ciprofloxacin alone and in combination against 100 clinical isolates of P. aeruginosa from one medical center in southern Taiwan. The combination susceptibility assay was performed using the checkerboard technique. The percentage of resistance of P. aeruginosa to single agents in our study was relatively high for the Asia-Pacific area, except to aztreonam. Piperacillin plus amikacin exhibited the highest potential for synergy (59/100) in this study. Moreover, a high percentage of synergism was also noted with amikacin combined with cefepime (7/100) or aztreonam (16/100). The combination of two beta-lactams, such as cefepime with piperacillin, and aztreonam with cefepime or piperacillin, showed synergistic effects against some P. aeruginosa isolates. Although ciprofloxacin is a good anti-pseudomonal agent, a very low potential for synergy with other antibiotics was demonstrated in this study. No antagonism was exhibited by any combination in our study. Among piperacillin-resistant strains, there was synergy with a beta-lactam plus amikacin, including the combination of piperacillin and amikacin. However, the combination of two beta-lactams, such as piperacillin and cefepime or aztreonam, did not have any synergistic activity against these strains. In summary, the combinations of amikacin with the tested beta-lactams (piperacillin, aztreonam, cefepime) had a greater synergistic effect against P. aeruginosa, even piperacillin-resistant strains, than other combinations. Understanding the synergistic effect on clinical strains may help clinicians choose better empirical therapy in an area with high prevalence of multidrug-resistant P. aeruginosa.     

In vitro combination effects of aztreonam and aminoglycoside against multidrug-resistant Pseudomonas aeruginosa in Japan

The aim of this study was to evaluate the in vitro combination effects of aztreonam (AZT) and aminoglycosides against multidrug-resistant (MDR) Pseudomonas aeruginosa strains in Japan. We investigated 47 MDR P. aeruginosa strains collected from 8 facilities. We selected the aminoglycosides amikacin (AMK), gentamicin (GM), and arbekacin (ABK) to examine their effects when combined with AZT using the checkerboard method. Of the 47 MDR P. aeruginosa strains, 41 tested positive for metallo-β-lactamase (MBL). In all combinations, aminoglycosides decreased the minimum inhibitory concentrations of AZT in a dose-dependent manner, and there was no apparent antagonism. The combination effects were scored on a scale of 0 to 4, and statistical analysis was performed using the Wilcoxon signed-rank test. In all 47 strains, AZT + ABK (mean score, 2.02) had the highest score, followed by AZT + AMK (1.68) and AZT + GM (1.38) (ABK versus GM, P < 0.0001). In 41 MBL-positive strains, AZT + ABK (mean score, 2.05) had the highest score, followed by AZT + AMK (1.56) and AZT + GM (1.37) (ABK versus AMK, P = 0.02, and ABK versus GM, P < 0.0001). AZT + ABK was the most promising combination regimen against MDR P. aeruginosa strains; the other promising combinations were AZT + AMK and AZT + GM.     

In vitro activity of fosfomycin-gentamicin, fosfomycin-ceftazidime, fosfomycin-imipenem and ceftazidime-gentamicin combinations against ceftazidime-resistant Pseudomonas aeruginosa

The effects of antimicrobial combinations against ceftazidime-resistant Pseudomonas aeruginosa strains isolated from hospitalized patients were investigated. Using the checkerboard titration method, combination of fosfomycin-gentamicin, fosfomycin-ceftazidime, fosfomycin-imipenem and ceftazidime-gentamicin was synergistic against 4, 11, 38 and 39% of 22, 18, 29 and 18 strains tested respectively and additive effect of the combinations against the strains tested was 41, 33, 14 and 44%, respectively. Antagonistic effects against the isolates were noted when fosfomycin was combined with gentamicin (27%), ceftazidime (22%) and imipenem (7%). No antagonistic effect was observed in the ceftazidime-gentamicin combination.     

Growth inhibitory activity of clinical isolates of Pseudomonas aeruginosa against Staphylococcus aureus (MRSA and MSSA)]

Anti staphylococcal activity by clinical isolates of Pseudomonas aeruginosa was tested by the reversed agar plate and the filter paper stamp methods. Almost 40% of Pseudomonas aeruginosa inhibited the growth of both Methicillin resistant Staphylococcus aureus (MRSA) and Methicillin sensitive Staphylococcus aureus (MSSA). Green pigment (Pyocyanin) produced strains showed a strong inhibitory effect against MRSA and MSSA respectively. But some other pigment (Yellow, Red) strains also showed anti staphylococcal activity. These data suggest the colonization of Pseudomonas aeruginosa with anti staphylococcal activity may not be eradicated by the anti pseudomonic antibiotics.     

环丙沙星或阿米卡星联合β-内酰胺类抗生素对多重耐药铜绿假单胞菌的体外联合抑菌效应研究

目的探讨环丙沙星或阿米卡星分别联合4种临床常用抗铜绿假单胞菌β-内酰胺类抗生素的体外联合抑菌效应。方法2004-01—2004-09北京协和医院检验科用微量肉汤稀释法测定6种测试药物对35株临床分离并具有不同耐药表型的铜绿假单胞菌的MIC值;用肉汤棋盘法测定环丙沙星及阿米卡星分别联合头孢他啶(CAZ)、亚胺培南(IMP)、美罗培南(MEM)、哌拉西林/他唑巴坦(TZP)4种β-内酰胺类药物的联合抑菌效应。结果环丙沙星(CIP)及阿米卡星(AK)分别与4种β-内酰胺类药物联合主要表现出协同和相加作用,AK组出现协同现象的比率(AK CAZ:71·43%;AK IMP:42·86%;AK MEM:54·29%;AK TZP:85·71%)高于CIP组(CIP CAZ:20%;CIP IMP:25·71%;CIP MEM:14·29%;CIP TZP:31·43%)。CIP组中CIP TZP组合协同发生率最高;AK组中AK TZP组合协同发生率最高。两组均未发现拮抗现象。结论环丙沙星或阿米卡星联合β-内酰胺类抗生素在体外对耐药的铜绿假单胞菌体现出较好的联合抑菌效应。     

Antibiotic activity of P. aeruginosa against MRSA and Candida albicans

The antibiotic activity demonstrated by P. aeruginosa (Bacillus pyocyaneus) has been reported more than one hundred years ago by Emmerich et al (1899). Studies on such bacterial interference between P. aeruginosa and other pathogenic bacteria or fungi have not been extensively reported in recent years. In this paper, we report on the anti MRSA activity and anti Candida activity demonstrated by clinical isolates of P. aeruginosa (34 strains). The antibiotic activity was tested by reversed agar plate method, as previously reported, and the degree of the activity was expressed as the diameter of the zone of growth inhibition. The stability of both anti MRSA activity and anti Candida activity was evaluated at the time after 24 and 48-hr incubation. Also the effect of agar plate with or without 5% sheep blood on antibiotic activity was evaluated. Strong anti MRSA activity and anti Candida activity was shown at the time after 24-hr incubation. At the time after 48-hr incubation, anti MRSA activities were significantly suppressed but anti Candida activities were persisted. The inhibitory activity was correlated with dye production of P. aeruginosa. Some strains having non or weak dye production, showed the inhibitory activity by 48-hr incubation. Result from these strains without suppression of anti Candida activity by additional blood may suggest that the existence of a new factor produced by P. aeruginosa. Because of frequent isolation of MRSA or Candida from clinical materials, we must consider bacterial flora and bacterial interference against pathogenic bacteria at the time of the antibiotic choice for the patients infected or colonized with P. aeruginosa.     

Effects of macrolide antibiotics against mucoid Pseudomonas aeruginosa

Macrolide antibiotics at concentrations by far lower than their MICs proved to inhibit the production of alginate, elastase, and protease by mucoid Pseudomonas aeruginosa. The morphological study of mucoid P. aeruginosa under the electron microscope revealed the slime-like structures common to the cell morphology of the organism in cultured colonies and foci in a model for respiratory tract infection in mice, and the strains of mucoid P. aeruginosa which had been allowed to get in contact with the drugs proved to produced obviously fewer slime-like structures than control strains. The effect of a 14-membered macrolide, erythromycin, against mucoid P. aeruginosa was also observed with a 16-membered macrolide, rokitamycin this effect appeared to be common to the macrolide.     

铜绿假单胞菌抗菌物质体外对鲍曼不动杆菌的抑制作用研究

目的观察铜绿假单胞菌抗菌物质对鲍曼不动杆菌的体外抑菌活性。方法用交叉条带试验方法测定铜绿假单胞菌对15株鲍曼不动杆菌的体外抑制活性。结果铜绿假单胞菌对鲍曼不动杆菌体外抑菌活性良好,15株产色素铜绿假单胞菌中,除4、8、14、15号菌株外,其余铜绿假单胞菌对鲍曼不动杆菌的抑制率均为100％。并发现铜绿假单胞菌产色素菌株的抗菌活性显著优于不产色素菌株。铜绿假单胞菌主要通过产生的绿脓素抑制鲍曼不动杆菌的生长。结论铜绿假单胞菌产生的抗菌物质对鲍曼不动杆菌具有较强的抗菌活性,具有广阔的开发前景。     

Rapid diagnosis of pulmonary Pseudomonas aeruginosa infections by indirect immunofluorescent antibody]

167 sputum specimens collected from patients with pulmonary infection were tested by IFA (Indirect immunofluorescent antibody-staining) with serogroup-specific monoclonal antibody to Pseudomonas aeruginosa, compared with quantitative sputum culture. The results showed the minimum concentration of bacteria detectable by IFA was 10 cfu/ml. 31(86.1%) were positive in 36 specimens with more than 10 cfu/ml of Pseudomonas aeruginosa. 22(100%) were positive in 22 specimens with more than 10 cfu/ml of Pseudomonas aeruginosa. In 127 specimens with a negative culture for Pseudomonas aeruginosa, 121(95.2%) were negative, 6(4.8%) were false-positive which could be identified by Gram's-staining. The type of Pseudomonas aeruginosa could also be identified within 3 hours.     

Therapy against intractable respiratory infections with Pseudomonas aeruginosa

Patients with diffuse panbronchiolitis (DPB) are frequently affected by Pseudomonas aeruginosa superinfection. To elucidate the predisposing factors of Pseudomonas aeruginosa superinfection in patients with DPB, we analyzed the age of onset, duration of the disease, chest X-ray findings, blood gas levels, lung function, and bacteriological findings. These data were compared with those of patients who had not developed Pseudomonas aeruginosa superinfection. The administration of antibiotics and corticosteroids did not influence the incidence of Pseudomonas aeruginosa superinfection in DPB patients. The patients with long duration, more severe lung function and more deteriorated roentgenological findings developed Pseudomonas aeruginosa superinfection more easily. These infections in the lower respiratory tract significantly affect the prognosis of DPB patients. Using long-term administrations of a new quinolone antibacterial agent against DPB, acute exacerbations were controlled in some patients and the frequency of their admission to hospital was lessened. A multicomponent vaccine raised antibody titers against OEP, elastase, protease and exotoxin in DPB patients. Further clinical investigations are under way in our hospital to confirm the clinical usefulness of the Pseudomonas aeruginosa multicomponent vaccine in DPB from prophylactic and therapeutic points of view.     

Pseudomonas aeruginosa: role in the pathogenesis of the CF lung lesion

Lung disease is the leading cause of morbidity and mortality in individuals with cystic fibrosis (CF), with P. aeruginosa the main pulmonary infectious agent. Although CF patients can become infected with other microorganisms (such as Burkholderia cepacia complex, Staphylococcus aureus, Haemophilus influenzae, and atypical mycobacteria), P. aeruginosa predominates, eventually infecting approximately 80% of patients. Once established, P. aeruginosa infection usually persists until death. The interaction between the CF host and this opportunistic pathogen is unique and most likely directly contributes to the classical end-stage pathology of CF lung disease. However, the extent to which this constitutes success by the pathogen or failure by the host, or both, is yet to be determined. Many important questions remain regarding host susceptibility, the role of both innate and adaptive immune defenses, bacterial infectivity and transmission, and pathogen virulence factors. Here, we discuss some recent advances toward understanding this complex interaction between host and pathogen and how the interplay influences the CF lung lesion.     

Therapies against virulence products of Staphylococcus aureus and Pseudomonas aeruginosa

Methicillin-resistant STAPHYLOCOCCUS AUREUS (MRSA) and PSEUDOMONAS AERUGINOSA are key pathogens in hospitals (particularly intensive care units), in long-term care facilities, and in outpatients with specific comorbidities and risk factors. Both MRSA and P. AERUGINOSA display resistance to a wide array of antibiotics. Further, both bacteria contain a variety of virulence products or systems that make it difficult to treat associated infections. Within the past several years, community-acquired MRSA containing virulence factors [particularly the Panton-Valentine leukocidin (PVL) gene] has emerged globally. Given the limited number of novel antibiotics to treat antibiotic-resistant organisms, there is growing interest in treating bacterial infections by targeting specific virulence products or systems. This article reviews potential therapeutic targets in the virulence systems of these two bacteria that are responsible for a large number of serious infections in critically ill patients.     

Role of mechanical injury on airway surface in the pathogenesis of Pseudomonas aeruginosa

In this study, bacterial attachment to rat tracheal surface was measured using three nonmucoid strains of Pseudomonas aeruginosa and bacterial growth after binding to tracheal surface was also tested. Brush injury on tracheal surface significantly increased bacterial attachment (1,190 to 1,600%); bacteria binding to brush-injured sites grew more rapidly than either nonbinding bacteria or those on intact trachea. A partial characterization of the binding sites for P. aeruginosa on either intact or injured tracheal surface also was performed. Treatment of injured tracheal surface with metaperiodate significantly inhibited attachment of P. aeruginosa, but trypsin treatment did not. In contrast, neither reagent had any effects on bacterial attachment to intact tracheal surface. These results suggest that brush injury on tracheal surface produces new binding sites as a receptor for P. aeruginosa, and that this receptor has carbohydrates as important components and that it is not a protein receptor. In addition, in order to determine what the dominant sugar of this receptor was, we tested the inhibition of bacterial attachment with monosaccharide, neuraminidase, and lectin. Treatment of bacteria with N-acetylneuraminic acid (NANA) dramatically inhibited bacterial attachment to injured trachea. However, NANA also inhibited the growth of this organism. Moreover, neither neuraminidase nor lectin data suggested that the dominant sugar of the receptor was NANA. Our data go so far as to confirm that the major component of the receptor of nonmucoid strains of P. aeruginosa on brush-injured trachea is carbohydrates; it is still unclear what kind of sugar is the dominant component of the receptor.(ABSTRACT TRUNCATED AT 250 WORDS)