Achromobacter xylosoxidans and Stenotrophomonas maltophilia: Emerging Pathogens Well-Armed for Life in the Cystic Fibrosis Patients' Lung.

In patients with cystic fibrosis (CF), the lung is a remarkable ecological niche in which the microbiome is subjected to important selective pressures. An inexorable colonization by bacteria of both endogenous and environmental origin is observed in most patients, leading to a vicious cycle of infection-inflammation. In this context, long-term colonization together with competitive interactions among bacteria can lead to over-inflammation. While Pseudomonas aeruginosa and Staphylococcus aureus, the two pathogens most frequently identified in CF, have been largely studied for adaptation to the CF lung, in the last few years, there has been a growing interest in emerging pathogens of environmental origin, namely Achromobacter xylosoxidans and Stenotrophomonas maltophilia. The aim of this review is to gather all the current knowledge on the major pathophysiological traits, their supporting mechanisms, regulation and evolutionary modifications involved in colonization, virulence, and competitive interactions with other members of the lung microbiota for these emerging pathogens, with all these mechanisms being major drivers of persistence in the CF lung. Currently available research on A. xylosoxidans complex and S. maltophilia shows that these emerging pathogens share important pathophysiological features with well-known CF pathogens, making them important members of the complex bacterial community living in the CF lung.

Microbial associates of the southern mole cricket (Scapteriscus borellii) are highly pathogenic.

We report the isolation and identification of seven bacterial strains and one fungal strain from dead and diseased Scapteriscus borellii mole crickets collected from a golf course in southern California. Using 16S and 18S rRNA gene sequence analysis we identified the microbes as Serratia marcescens (red), S. marcescens (white), S. marcescens (purple), Achromobacter xylosoxidans, Chryseobacterium sp., Ochrobactrum anthropi, Tsukamurella tryosinosolvens, and Beauveria bassiana. We performed a dose response curve for each of these cricket-associated microbial strains (except T. tryosinosolvens) and two other strains of S. marcescens (DB1140 and ATCC 13880). We found that all of these microbes except O. anthropi were highly pathogenic to D. melanogaster compared to the other strains of S. marcescens. Injecting the mole cricket associated strains of Serratia into flies killed all infected flies in ≤24h. For all other strains, the median time to death of injected flies varied in a dose-dependent manner. In vivo growth assessments of these microbes suggested that the host immune system was quickly overcome. We used disease tolerance curves to better understand the host-microbe interactions. Further studies are necessary to understand in mechanistic detail the virulence mechanisms of these mole cricket associated microbes and how this association may have influenced the evolution of mole cricket immunity.

Seasonality of acquisition of respiratory bacterial pathogens in young children with cystic fibrosis.

BACKGROUND: Seasonal variations are often observed for respiratory tract infections; however, limited information is available regarding seasonal patterns of acquisition of common cystic fibrosis (CF)-related respiratory pathogens. We previously reported differential seasonal acquisition of Pseudomonas aeruginosa in young children with CF and no such variation for methicillin-susceptible Staphylococcus aureus acquisition. The purpose of this study was to describe and compare the seasonal incidence of acquisition of other respiratory bacterial pathogens in young children with CF. METHODS: We conducted a retrospective study to describe and compare the seasonal incidence of methicillin-resistant Staphylococcus aureus (MRSA), Stenotrophomonas maltophilia, Achromobacter xylosoxidans, and Haemophilus influenzae acquisition in young CF patients residing in the U.S. using the Cystic Fibrosis Foundation National Patient Registry, 2003-2009. Log-linear overdispersed Poisson regression was used to evaluate seasonal acquisition of each of these pathogens. RESULTS: A total of 4552 children met inclusion criteria. During follow-up 910 (20%), 1161 (26%), 228 (5%), and 2148 (47%) children acquired MRSA, S. maltophilia, A. xylosoxidans and H. influenzae, respectively. Compared to winter season, MRSA was less frequently acquired in spring (Incidence Rate Ratio [IRR]: 0.79; 95% Confidence Interval [CI]: 0.65, 0.96) and summer (IRR: 0.69; 95% CI: 0.57, 0.84) seasons. Similarly, a lower rate of A. xylosoxidans acquisition was observed in spring (IRR: 0.59; 95% CI: 0.39, 0.89). For H. influenzae, summer (IRR: 0.88; 95% CI: 0.78, 0.99) and autumn (IRR: 0.78; 95% CI: 0.69, 0.88) seasons were associated with lower acquisition rates compared to winter. No seasonal variation was observed for S. maltophilia acquisition. CONCLUSION: Acquisition of CF-related respiratory pathogens displays seasonal variation in young children with CF, with the highest rate of acquisition for most pathogens occurring in the winter. Investigation of factors underlying these observed associations may contribute to our understanding of the aetiology of these infections and guide future infection control strategies.

Pseudobacteremia outbreak of biofilm-forming Achromobacter xylosoxidans - environmental transmission.

BACKGROUND: Achromobacter xylosoxidans (AX) is known for intrinsic resistance to disinfectants. Our laboratory routine surveillance system detected an unexpected rise in AX bloodstream infections in a 2200-bed hospital. An epidemiological investigation was conducted to find the source and disrupt further transmission. METHODS: Outbreak cases were defined as patients with at least one positive blood culture positive for AX from May 2014 to May 2015. Medical records were reviewed, affected wards, as well as the microbiology laboratory were audited. Additionally, microbiologic culture and biofilm staining for suspected antiseptic reusable tissue dispensers were performed, and isolated AX strains were typed using RAPD PCR and PFGE. RESULTS: During the outbreak period, AX were isolated from blood cultures from 26 patients. The retrospective cohort study did not reveal common risk factors. The clinical features of the case patients suggested a pseudobacteremia. The reusable tissue dispensers containing Incidin® Plus solution product were found to be contaminated with biofilm-forming AX. Typing of the isolates revealed that blood culture isolates were identical with the strains found in the dispensers. CONCLUSIONS: After changing the usage of the product to single-use and educating staff, the outbreak was terminated. Contamination of dispensers occurred due to insufficient reprocessing, since biofilm disrupting steps were not included in the process.

Severe Achromobacter xylosoxidans infection and loss of sputum bacterial diversity in an adult patient with cystic fibrosis.

Achromobacter spp. are emerging pathogens in the lungs of patients with cystic fibrosis. We report the case of an adult patient with cystic fibrosis and chronic A. xylosoxidans infection who experienced rapid, progressive clinical deterioration. Metagenomic analysis of the sputum revealed that the airway microbiota was almost entirely dominated by A. xylosoxidans. We review the impact of this organism on lung function and the airway microbiome in cystic fibrosis, and discuss the potential for cross-infection between patients.

Achromobacter xylosoxidans: an emerging pathogen carrying different elements involved in horizontal genetic transfer.

In the last few years, numerous cases of multidrug-resistant Achromobacter xylosoxidans infections have been documented in immunocompromised and cystic fibrosis patients. To gain insights into the molecular mechanisms and mobile elements related to multidrug resistance in this bacterium, we studied 24 non-epidemiological A. xylosoxidans clinical isolates from Argentina. Specific primers for plasmids, transposons, insertion sequences, bla(ampC), intI1, and intI2 genes were used in PCR reactions. The obtained results showed the presence of wide host range IncP plasmids in ten isolates and a high dispersion of class 1 integrons (n = 10) and class 2 integrons (n = 3). Four arrays in the variable region (vr) of class 1 integrons were identified carrying different gene cassettes as the aminoglycoside resistance aac(6')-Ib and aadA1, the trimethoprim resistance dfrA1 and dfrA16, and the ß-lactamase bla(OXA-2). In only one of the class 2 integrons, a vr was amplified that includes sat2-aadA1. The bla(ampC) gene was found in all isolates, confirming its ubiquitous nature. Our results show that A. xylosoxidans clinical isolates contain a rich variety of genetic elements commonly associated with resistance genes and their dissemination. This supports the hypothesis that A. xylosoxidans is becoming a reservoir of horizontal genetic transfer elements commonly involved in spreading antibiotic resistance.

A heat-stable cytotoxic factor produced by Achromobacter xylosoxidans isolated from Brazilian patients with CF is associated with in vitro increased proinflammatory cytokines.

BACKGROUND: Recently, Achromobacter xylosoxidans has been related to chronic lung diseases in patients suffering from cystic fibrosis (CF), but its involvement has not been elucidated. Some virulence properties of A. xylosoxidans isolated from Brazilian patients with CF were revealed in this work. METHODS: This study examined the production of a cytotoxic factor of A. xylosoxidans capable of stimulating the secretion of inflammatory cytokines (IL-6 and IL-8) from lung mucoepidermoid carcinoma cells (NCI-H292). The cytokines were measured using enzyme-linked immunosorbent (ELISA) assays. To investigate whether the cytotoxic factors may be endotoxins, they were treated with polymyxin B. RESULTS: The culture supernatants of all A. xylosoxidans produced a heat stable, active cytotoxin in NCI-H292 cells capable of leading to intracellular vacuoles and subsequent cell contact loss, chromatin condensation, a picnotic nucleus and cell death. There was a higher concentration of proinflammatory cytokines in the NCI-H292 cells after 24 h of incubation, with the fraction greater than 50 kDa from the culture supernatant. The cytotoxin activity remained even after treatment with polymyxin B, which suggested that the release of IL-6 and IL-8 was not stimulated by lipopolysaccharide (LPS). CONCLUSION: The cytotoxic factor produced by A. xylosoxidans may represent an important virulence factor, which when associated with CF chronic lung inflammation, may cause tissue damage and decline of lung function.

Achromobacter xylosoxidans, an emerging pathogen in catheter-related infection in dialysis population causing prosthetic valve endocarditis: a case report and review of literature.

INTRODUCTION: Dialysis catheter-related infection is a major cause of morbidity and mortality in patients on dialysis. In recent years, there have been reported cases of infections with opportunistic environmental organism, Achromobacter xylosoxidans (AX) causing bacteremia in patients on dialysis. However, no previous such reports on prosthetic valve endocarditis in a dialysis patient with Achromobacter xylosoxidans were found after a Medline search. We report such a case and review the literature. CASE: A 69-year-old diabetic man with bioprosthetic aortic valve replacement developed end-stage renal disease following infective endocarditis with Staphylococcus epidermidis. Even though he was treated successfully for his endocarditis, he developed further bacteremia with AX from his peripherally inserted central catheter (PICC) and the line was removed. He had further episodes of bacteremia with AX while having dialysis with tunneled line and the line was also removed. He was re-admitted with pyrexia and vegetations both in mitral and prosthetic aortic valve confirmed with transesophageal echo. His antimicrobial therapy with etrapenum, tigecycline and cotrimoxazole failed. He had both mitral and prosthetic aortic valve replacements but postoperatively developed multiorgan failure and died despite the intensive support. DISCUSSION: Achromobacter xylosoxidans is an aerobic, Gram-negative bacillus and considered to be an opportunistic pathogen with low virulence. Infective endocarditis is a potentially lethal complication of bacteremia. The choice of appropriate antibiotic is crucial in these cases. AX strains are highly resistant to antibiotics. The organism is usually susceptible to antipseudomonal penicillins, carbapenems and trimethoprim-sulfamethoxazole. CONCLUSION: AX is an emerging pathogen in catheter-related infection in the dialysis population and, therefore, needs vigilance and prompt treatment. Antimicrobial treatment should include susceptibility and synergy testing. Removal of central intravenous catheter should also be considered at the time of early presentation in patients at high risks of developing infective endocarditis.

Urinary tract infection due to Achromobacter xylosoxidans: report of 9 cases.

Urinary tract infection (UTI) due to Achromobacter xylosoxidans is rare. The aims were to know the frequency and clinical characteristics of this infection in our area. We performed a retrospective analysis of 9 patients with UTI caused by this organism diagnosed over a period of 13 y. The mean age was 63.1 y. All patients had underlying diseases or urological abnormalities. The most frequent underlying diseases were solid or hematological malignancies (3 cases). Seven patients (77.7%) had urological abnormalities. Eight patients had symptoms of cystitis and 1 remained asymptomatic. Seven patients had community acquired UTIs. Clinical outcome was favourable in 5 patients after antibiotic treatment and recurrence occurred in 3 patients who had urological abnormalities. All isolates were susceptible to imipenem and piperacillin-tazobactam, 88.8% were susceptible to ceftazidime and 77.7% were susceptible to trimethoprim-sulfamethoxazole. High frequencies of resistance to ampicillin (100%), amoxicillin/clavulanic acid (78%), cefuroxime (100%), cefotaxime (67%), norfloxacin (89%), ciprofloxacin (78%), nitrofurantoin (89%) and gentamicin (67%) were observed. UTI due to A. xylosoxidans was predominantly observed in elderly patients with predisposing factors, especially urological abnormalities, malignancies and immunosuppression. Treatment can be difficult due to the high level of antibiotic resistance. Trimethoprim-sulfamethoxazole may be useful for treatment, particularly in outpatients with community acquired infections.

Achromobacter xylosoxidans in cystic fibrosis: prevalence and clinical relevance.

BACKGROUND: Achromobacter xylosoxidans is increasingly cultured in sputum from cystic fibrosis (CF) patients; nevertheless, there are few published data on the clinical impact of this infection or chronic colonisation. METHODS: Relying on DNA fingerprinting techniques we studied the prevalence of A. xylosoxidans in our CF population. In a retrospective case control study the clinical status of patients with at least 3 sputum cultures positive for A. xylosoxidans over at least 9 months, at the moment of the first positive culture and during the period of colonisation were compared to age (+/-1 year), gender and to Pseudomonas aeruginosa colonisation controlled CF patients who had never A. xylosoxidans positive sputum cultures. RESULTS: The prevalence of patients with at least one positive A. xylosoxidans culture was 17.9%. 5.3% of the patients fulfilled the criteria of our definition of colonisation. Colonised patients had a median age of 20 years (range 11-27 years) and a mean colonisation period of 1.5 (+/-0.9) years. At the moment of the first positive culture we found significantly lower Bhalla scores on HRCT scans of the lungs (11+/-3 versus 16+/-3, p<0.002), lower Brasfield chest X-ray scores (14+/-3 versus 18+/-3, p<0.019), lower FVC values (70%+/-22 versus 94%+/-12, p<0.017) and lower FEV(1) values (55%+/-32 versus 78%+/-23, p=0.123), although the latter did not reach significance. There was no significant difference in body mass index (BMI) (18.7+/-3 kg/m2 versus 19.6+/-3 kg/m2, p=0.8). Over the study period A. xylosoxidans-colonised patients did have more need for intravenous antibiotic treatment courses (19 versus 5, p<0.001); nevertheless, there was no significant difference in lung function decline over the study period (FVC: -6.25+/-12.34% versus -5.62+/-8.30%, p 0.77, FEV1: -5.62+/-8.30% versus -1.87+/-11.58%, p<0.47). CONCLUSIONS: The prevalence of A. xylosoxidans infection or colonisation is probably underestimated. Colonised patients are mostly older, with more pronounced lung damage and lower lung function values. Although there was more need for intravenous antibiotic treatment courses, no faster decline in lung function was observed in A. xylosoxidans positive patients.