Description of Leeds Acinetobacter Medium, a new selective and differential medium for isolation of clinically important Acinetobacter spp., and comparison with Herellea agar and Holton's agar

Swine farm groundwater is a hidden hotspot for antibiotic-resistant pathogenic Acinetobacter

Acinetobacter is present in the livestock environment, but little is known about their antibiotic resistance and pathogenic species in the farm groundwater. Here we investigated antibiotic resistance of Acinetobacter in the swine farm groundwater (JZPG) and residential groundwater (JZG) of a swine farming village, in comparison to a nearby (3.5 km) non-farming village (WTG) using metagenomic and culture-based approaches. Results showed that the abundance of antibiotic resistome in some JZG and all JZPG (~3.4 copies/16S rRNA gene) was higher than that in WTG (~0.7 copies/16S rRNA gene), indicating the influence of farming activities on both groundwater types. Acinetobacter accounted for ~95.7% of the bacteria in JZG and JZPG, but only ~8.0% in WTG. They were potential hosts of ~95.6% of the resistome in farm affected groundwater, which includes 99 ARG subtypes against 23 antibiotic classes. These ARGs were associated with diverse intrinsic and acquired resistance mechanisms, and the predominant ARGs were tetracyclines and fluoroquinolones resistance genes. Metagenomic binning analysis elucidated that non-baumannii Acinetobacter including A. oleivorans, A. beijerinckii, A. seifertii, A. bereziniae and A. modestus might pose environmental risks because of multidrug resistance, pathogenicity and massive existence in the groundwater. Antibiotic susceptibility tests showed that the isolated strains were resistant to multiple antibiotics including sulfamethoxazole (resistance ratio: 96.2%), levofloxacin (42.5%), gatifloxacin (39.0%), ciprofloxacin (32.6%), tetracycline (32.0%), doxycycline (29.0%) and ampicillin (12.0%) as well as last-resort polymyxin B (31.7%), colistin (24.1%) and tigecycline (4.1%). The findings highlight potential prevalence of groundwater-borne antibiotic-resistant pathogenic Acinetobacter in the livestock environment.

Biosynthesis of bacterial cellulose nanofibrils in black tea media by a symbiotic culture of bacteria and yeast isolated from commercial kombucha beverage

Bacterial cellulose has drawn the attention for its unique properties and applications including; medicine, pharmacy, food, agricultural, textile and electronics. The present study focused on the production of bacterial cellulose nanofibrils (BCNF) from black tea as cost effective alternative medium in addition to study the effect of gamma radiation on BCNF properties. A symbiotic culture of bacteria and yeast (SCOBY) were isolated from commercial Kombucha beverage and were identified as Acinetobacter lowffii and Candida krusei, respectively. The symbiotic culture was used for production of BCNF on Hestrin-Schramm (HS), black tea (BT) and modified BT media. BCNF was purified (0.5 N NaOH) and quantified by dry weight, yield and productivity determination. Characterization and effect of gamma radiation (5-25 kGy) on BCNF were studied using Scanning Electron Microscope (SEM), Fourier transform infrared (FTIR) and X-Ray Diffraction (XRD). The highest BCNF production was achieved using BT medium with 0.2% tea and 6.0% commercial sugar (with dry weight 4.77-4.61 g/l and productivity 68.14% and 65.85%, respectively). Supplementation of BT medium with 1% ethanol, 0.27% Na₂HPO₄ and 0.5% yeast extract individually, enhanced the BCNF production (7.85, 6.84 and 5.73 g/l), respectively. FTIR spectrum of BCNF from sugared water (SW), HS and BT showed similar structure with high purity. As a conclusion, gamma irradiation has no effect on the BCNF structure while showed different effects on its crystallinity index and size with the different doses. The changes in CrI were ranged between (17 and 23.5%), while the crystallinity size (Cs) was affected by gamma irradiation in a positive relationship where the crystalline size was decreased (33%) by exposure to 5 kGy then increased by increasing the dose of radiation reaching 25.7% at 25 kGy. SEM graphs showed the morphology of microbial culture and its symbiotic relationship in addition to the ultrafine structure of non-irradiated and irradiated BCNF.

Profiling Antibiotic Resistance in Acinetobacter calcoaceticus

Background: Acinetobacter spp. have emerged as troublesome pathogens due to their multi-drug resistance. The majority of the work to date has focused on the antibiotic resistance profile of Acinetobacter baumannii. Although A. calcoaceticus strains are isolated in the hospital setting, limited information is available on these closely related species. Methods & Results: The computational analysis of antibiotic resistance genes in 1441 Acinetobacter genomes revealed that A. calcoaceticus harbored a similar repertoire of multi-drug efflux pump and beta-lactam resistance genes as A. baumannii, leading us to speculate that A. calcoaceticus would have a similar antibiotic resistance profile to A. baumannii. To profile the resistance patterns of A. calcoaceticus, strains were examined by Kirby−Bauer disk diffusion and phenotypic microarrays. We found that Acinetobacter strains were moderately to highly resistant to certain antibiotics within fluoroquinolones, aminoglycosides, tetracyclines, and other antibiotic classes. These data indicate that A. calcoaceticus has a similar antibiotic resistance profile as A. baumannii ATCC 19606. We also identified that all Acinetobacter species were sensitive to 5-fluoroorotic acid, novobiocin, and benzethonium chloride. Conclusion: Collectively, these data provide new insights into the antibiotic resistance in A. calcoaceticus and identify several antibiotics that could be beneficial in treating Acinetobacter infections.

Emergence of carbapenem resistant Acinetobacter baumannii clonal complexes CC2 and CC10 among fecal carriages in an educational hospital

Carbapenem-resistant Acinetobacter baumannii strains are increasing worldwide. In this study, samples were collected from hospital environments, extra hospital environments, and fecal carriages. 76% (89/117) of bacterial isolates were detected as A. baumannii strains. The imipenem resistance in the hospital environment, fecal carriages, extra hospital environments, and clinical isolates was 37.7% (17/45), 100% (9/9), 0% (0/45), and 92.9% (92/99), respectively. The blaVIM and blaOXA-23 were detected in 6.6% (3/45) and 2.2% (1/45) of strains isolated from hospital environments. Interestingly, strains isolated from fecal carriages had blaVIM, blaOXA-23, and blaIMP genes which resembled carbapenem resistance genes in clinical strains. The structure of clonal relatedness among all non-clinical isolates was as follows: CC2, 37% (33/89); CC1, 22.4% (20/89); CC3, 12.3% (11/89); CC25, 7.8% (7/89); CC10, 4.4% (4/89) and CC15, 2.2% (2/89). Comparison of clonal relatedness among clinical and non-clinical isolates indicated that widespread clones including CC2, CC3, and CC10 were common clonal complexes between two categories.

Looking through the FOG: microbiome characterization and lipolytic bacteria isolation from a fatberg site

Sewer systems are complex physical, chemical and microbial ecosystems where fats, oils and grease (FOG) present a major problem for sewer management. Their accumulation can lead to blockages (‘Fatbergs’), sewer overflows and disruption of downstream wastewater treatment. Further advancements of biological FOG treatments need to be tailored to degrade the FOG, and operate successfully within the sewer environment. In this study we developed a pipeline for isolation of lipolytic strains directly from two FOG blockage sites in the UK, and isolated a range of highly lipolytic bacteria. We selected the five most lipolytic strains using Rhodamine B agar plates and pNP-Fatty acid substrates, with two Serratia spp., two Klebsiella spp. and an environmental Acinetobacter strain that all have the capacity to grow on FOG-based carbon sources. Their genome sequences identified the genetic capacity for fatty acid harvesting (lipases), catabolism and utilization (Fad genes). Furthermore, we performed a preliminary molecular characterization of the microbial community at these sites, showing a diverse community of environmental bacteria at each site, but which did include evidence of sequences related to our isolates. This study provides proof of concept to isolation strategies targeting Fatberg sites to yield candidate strains with bioremediation potential for FOG in the wastewater network. Our work sets the foundation for development of novel bioadditions tailored to the environment with non-pathogenic Acinetobacter identified as a candidate for this purpose.

In vitro study to evaluate the antimicrobial activity of various multifunctional cosmetic ingredients and chlorphenesin on bacterial species at risk in the cosmetic industry

AIMS

We evaluated the activity of the preservative chlorphenesin and of four antimicrobial cosmetic multifunctional ingredients against various strains of gram-negative and gram-positive human opportunistic pathogens.

METHODS AND RESULTS

Growth kinetics, modelling growth parameters and statistical analyses enabled comparing bacterial behaviour in the presence and in the absence of the compound. Whatever compound tested (i.e. chlorphenesin, phenylpropanol, hexanediol, ethylhexylglycerin, hydroxyacetophenone) and strain origin (i.e. clinical versus industrial), the growth of 42 strains belonging to Acinetobacter spp., Burkholderia cepacia complex and Stenotrophomonas maltophilia, was totally inhibited. On the opposite all of the P. aeruginosa strains (n = 13) as well as 4 and 6 out of 10 strains of Pluralibacter gergoviae grew in the presence of chlorphenesin and ethylhexylglycerin, respectively. Some P. gergoviae and Staphylococcus hominis strains withstand hydroxyacetophenone. Within a species, the different strains show variable latency phase, growth rate (r) and carrying capacity (K). They can be similar, lower or higher than those measured in control conditions.

CONCLUSIONS

Data showed differences in the antimicrobial activity of compounds. Upon exposure, strains differed in their behaviour between and within species. Whatever species and strains, compound sensitivity could not be related to antibiotic resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

Most multifunctional ingredients showed significant antimicrobial properties against the wide panel of species and strains evaluated. This will help adjusting preservation strategies in the cosmetic industry.

Two new rapid PCR-based methods for identification of Acinetobacter baumannii isolated from clinical samples

The accurate identification of Acinetobacter spp. is challenging due to their high phenotypic and biochemical similarities. Because clinical relevance and antibiotic susceptibility are significantly different among different genomic species of Acinetobacter, the exact identification of A. baumannii is necessary and it can help us prevent inappropriate antibiotic use and inferior clinical care. This project employed a sequence-specific PCR assay for the rpoB region in A. baumannii to distinguish it from non-Acinetobacter baumannii Acinetobacter species. Moreover, a duplex PCR assay was used to detect bla_OXA-51-like and gluconolactonase genes as a second identification method. In this study, 210 isolates of Acinetobacter spp. were considered and identified by PCR-sequencing of rpoB gene as a reference test. PCR-sequencing of rpoB revealed that 179 isolates were A. baumannii and 31 were non- A. baumannii Acinetobacter strains. PCR amplification targeting the rpoB gene as the first method, detected 182 isolates of A. baumannii, while duplex PCR assay confirmed 163 isolates as A. baumannii. Data analysis indicated that the sensitivities of sequence-specific PCR of the rpoB gene and duplex PCR assay were 100% and 91.06%, respectively, while specificities were 91.18% and 100%, respectively. Given the data, it was revealed that these two methods showed a reasonable potential for the accurate identification of A. baumannnii from non- A. baumannii species. Sequence-specific PCR assay for the rpoB gene and duplex PCR assay for bla_OXA-51-like and gluconolactonase genes are rapid, reliable and cost-effective methods which can be used in clinical laboratories for the accurate identification of A. baumannii.

Synergistic activity of bile salts and their derivatives in combination with conventional antimicrobial agents against Acinetobacter baumannii

ETHNOPHARMACOLOGICAL RELEVANCE

Bile traditionally was used in wound healing, having erodent, antioxidant and antimicrobial potential. Acinetobacter baumannii is a frequent etiological agent of wound infections, exhibiting high level of resistance to conventional antibiotics.

AIM OF THE STUDY

To determine the effect of selected bile acid sodium salts and their 3-dehydro (i.e. 3-oxo) derivatives, as well as their combinations with commercial antibiotics against A. baumanniia, to confirm bile ethnopharmacological application in wound healing from aspect of microbiology.

MATERIALS AND METHODS

The sensitivity of reference and multidrug resistant (MDR) A. baumannii strains to bile salts, their derivatives and conventional antibiotics were examined by a microtiter plate method. The interaction of bile salts/derivatives and antibiotics was examined by a checkerboard method and time kill curve method. The interaction of bile salts with ciprofloxacin in terms of micelles formation was examined by DOSY NMR technique.

RESULTS

The bile salts sodium deoxycholate (Na-DCA) and sodium chenodeoxycholate (Na-CDCA), as well as their derivatives sodium 3-dehydro-deoxycholate (Na-3DH-DCA) and sodium 3-dehydro-chenodeoxycholate (Na-3DH-CDCA), potentiate antibiotic activity and resensitize A. baumannii. The bile salts and their derivatives enhance A. baumannii sensitivity to antibiotics, particularly those that should penetrate cell to exhibit activity. The sodium salts of bile acid derivatives, namely Na-3DH-DCA and Na-3DH-CDCA, showed synergy against both reference and MDR strain in combination with ciprofloxacin or gentamicin, while synergy with gentamicin was obtained in all combinations, regardless of bile salt type and bacterial strains. The synergy with Na-3DH-CDCA was further confirmed by the time-kill curve method, as bacterial number decreased after 12 h. NMR experiment revealed that this bile salt derivative and ciprofloxacin form co-aggregates when bile salts concentration was higher than critical micelle concentrations (CMC), which indicate the possibility that bile salts enhance ciprofloxacin cell penetration by membrane destabilization, contributing to the synergy.

CONCLUSION

The synergistic interactions between bile salts or derivatives with ciprofloxacin and particularly gentamicin represent a promising strategy for the treatment of A. baumannii wound infections.

Comparative assessment of growth media and incubation conditions for enhanced recovery and isolation of Acinetobacter baumannii from aquatic matrices

Acinetobacter baumannii causes serious multidrug resistant nosocomial infections around the world. This comprehensive comparative study was designed to assess the effect of temperature (30, 37 and 42 °C), incubation (aerobic and microaerobic) condition and selective [CHROMagar Acinetobacter (CHR) and Leeds Acinetobacter Medium (LAM)] and non-selective [Modified Karmali Agar (MKA)] growth media on the enhanced recovery of A. baumannii from a variety of water (agricultural, recreational, raw drinking intake source, pre-chlorinated and post-chlorinated wastewater effluent) samples spiked with a known number of A. baumannii cells. After spiking each water type with a known number of cells in 10 mL volume, the sample was passed through a membrane filter (pore size 0.45 μm) and filters were placed on different selective media plates and subjected to incubate at various incubation conditions. The results reported in this study show that for all water types tested (except post-chlorinated wastewater effluent), LAM was the most effective selective growth medium in combination with variable temperature and incubation conditions for yielding high recovery rates of A. baumannii cells. Overall, A. baumannii showed that it has a high adaptive capacity to grow on selective and non-selective growth media at different temperature and incubation conditions. The data described in this study suggest that no single incubation condition and growth media would efficiently recover A. baumannii from all environmental water types tested. This data also indicate that selective growth media and incubation condition can significantly affect the recovery of A. baumannii. Differences in recovery of A. baumannii observed in this study which appeared to be dependent on the temperature and environmental characteristics of incubation as well as the sample type, suggest the need for caution when comparing recovery using different protocols.

Combined Effects Of Low Incubation Temperature, Minimal Growth Medium, And Low Hydrodynamics Optimize Acinetobacter baumannii Biofilm Formation

BACKGROUND

Biofilm formation is an important virulence factor expressed by Acinetobacter baumannii. It shields and protects microbial cells from host immune responses, antibiotics, and other anti-infectives. Its effects on Acinetobacter baumannii infection treatments notwithstanding, important environmental factors that influence its formation have not been fully investigated.

METHODS

Biofilm formation was assessed using the qualitative modified Congo red assay and quantitative microtiter plate methods. The combined effect of temperature, medium and shear force was determined by measuring adherence (OD570 nm) in microtiter plate after incubation at 26°C, 30°C, and 37°C when biofilm-grown cells were cultured in the presence of minimal nutrient medium (EAOB) and nutrient-rich medium (TSB) without or with agitation at 50 rpm. Antibiotics susceptibility of meropenem, imipenem, and ciprofloxacin were tested with Kirby-Bauer disc method. P<0.05 was considered statistically significant in all the tests.

RESULTS

A noticeable variation in adherence was observed among the isolates cultured with both media. Biofilm forming capacity of the isolates range from 0.09-0.33. The majority of the isolates had their relative biofilm-forming capacity significantly (p<0.05) higher than the positive control, Acinetobacter baumannii ATCC 19606. The biofilm biomass during growth in nutrient-rich medium (TSB) without shaking was significantly different (p<0.05; Tukey's test) among the three temperatures tested compared with when it was cultured in EAOB without shaking. A positive correlation was observed between biofilm formation and resistance to imipenem (r=0.2889; p=0.05). There was a statistically significant difference among the median of the three source groups (p<0.05) compared with the median between the source groups.

CONCLUSION

This observation extended further the view that A. baumannii biofilm formation is enhanced when nutrient-poor medium is used at room temperature (26°C) with or without agitation compared to growth at 37°C.

Heme uptake and utilization by hypervirulent Acinetobacter baumannii LAC-4 is dependent on a canonical heme oxygenase (abHemO)

Acinetobacter baumannii is an opportunistic pathogen that causes serious infections in critically ill and immune compromised patients. The ability to acquire iron from the hosts iron and heme containing proteins is critical to their survival and virulence. The majority of A. baumannii hypervirulent strains encode a heme uptake system that includes a putative heme oxygenase (hemO). Despite reports indicating A. baumannii can grow on heme direct evidence of extracellular heme uptake and metabolism has not been shown. Through isotopic labeling (¹³C-heme) we show the hypervirulent A. baumannii LAC-4 metabolizes heme to biliverdin IXα (BVIXα), whereas ATC 17978 that lacks the hemO gene cluster cannot efficiently utilize heme. Expression and purification of the protein encoded by the A. baumannii LAC-4 hemO gene confirmed catalytic conversion of heme to BVIX. We further show inhibition of abHemO with previously characterized P. aeruginosa HemO inhibitors in a fluorescence based assay that couples HemO catalytic activity to the BVIXα binding phytochrome IFP1.4. Furthermore, the hemO gene cluster encodes genes with homology to heme-dependent extra cytoplasmic function (ECF) σ factor systems. The hemophore-dependent ECF system in Pseudomonas aeruginosa has been shown to play a critical role in heme sensing and virulence within the host. The prevalence of a hemO gene cluster in A. baumannii LAC4 and other hypervirulent strains suggests it is required within the host to adapt and utilize heme and is a major contributor to virulence.

First isolation of carbapenem-resistant Acinetobacter beijerinckii from an environmental sample

The emergence of opportunistic Acinetobacter spp. in healthcare settings poses a significant threat to public health. The major reasons for nosocomial spread of these species are their abilities to develop and transfer drug resistance against various classes of antibiotics. Considering that Acinetobacter spp. are ubiquitous in nature, can utilize several carbon sources, and reach humans via various pathways, our aim was to obtain information about the environmental strains of this genus. Our first step was to develop and test a multistep isolation procedure based on traditional scientific methods. Antibiotic resistance patterns of the isolated strains were determined, as susceptibility to 12 antibiotics of 7 classes was tested by MIC Test Strip method. Altogether 366 samples (groundwater, surface water, and soil) of 24 sites were investigated and a collection of 37 Acinetobacter isolates was obtained. Among others, clinically important human pathogen Acinetobacter spp., such as A. baumannii, A. johnsonii, and A. gyllenbergii were identified. Three environmental strains were determined as multidrug-resistant including a carbapenem-resistant, hemolytic Acinetobacter beijerinckii strain isolated from a hydrocarbon-contaminated groundwater sample. In summary, it has been found that the applied multistep isolation procedure is applicable to isolate various species of Acinetobacter genus. Based on the antibiotic resistance assay, we can conclude that environmental representatives of Acinetobacter spp. are able to develop multidrug resistance, but at a lower rate than their clinical counterparts.

Comparative genomic analysis of Acinetobacter spp. plasmids originating from clinical settings and environmental habitats

Bacteria belonging to the genus Acinetobacter have become of clinical importance over the last decade due to the development of a multi-resistant phenotype and their ability to survive under multiple environmental conditions. The development of these traits among Acinetobacter strains occurs frequently as a result of plasmid-mediated horizontal gene transfer. In this work, plasmids from nosocomial and environmental Acinetobacter spp. collections were separately sequenced and characterized. Assembly of the sequenced data resulted in 19 complete replicons in the nosocomial collection and 77 plasmid contigs in the environmental collection. Comparative genomic analysis showed that many of them had conserved backbones. Plasmid coding sequences corresponding to plasmid specific functions were bioinformatically and functionally analyzed. Replication initiation protein analysis revealed the predominance of the Rep_3 superfamily. The phylogenetic tree constructed from all Acinetobacter Rep_3 superfamily plasmids showed 16 intermingled clades originating from nosocomial and environmental habitats. Phylogenetic analysis of relaxase proteins revealed the presence of a new sub-clade named MOBQAci, composed exclusively of Acinetobacter relaxases. Functional analysis of proteins belonging to this group showed that they behaved differently when mobilized using helper plasmids belonging to different incompatibility groups.

Isolation and identification of Acinetobacter spp. from healthy canine skin

BACKGROUND

Acinetobacter species can exhibit widespread resistance to antimicrobial agents. They are already recognized as important nosocomial pathogens of humans, but are becoming increasingly recognized in opportunistic infections of animals.

HYPOTHESIS/OBJECTIVES

This study aimed to determine whether Acinetobacter spp. are carried on skin of healthy dogs and, if present, to identify the species.

ANIMALS

Forty dogs were sampled at veterinary practices and rescue centres. They were free from skin disease and receiving no systemic or topical treatments.

METHODS

Skin swab samples were collected from four sites on each dog and cultured. Acinetobacter spp. isolates were detected by biochemical tests and gas chromatography. The species was determined by sequencing the RNA polymerase β-subunit (rpoB) gene. Isolates were screened for OXA carbapenemase genes and class 1 integrons capable of carrying resistance genes, and subjected to antimicrobial susceptibility tests.

RESULTS

For 25% dogs sampled (10 of 40), Acinetobacter spp. were isolated at one or more skin sites. Thirteen Acinetobacter spp. isolates were recovered from 160 samples. The most frequently cultured was A. lwoffii (seven of 13), followed by A. baumannii (two of 13), A. junii (one of 13), A. calcoaceticus (one of 13), A. pittii (one of 13) and a novel Acinetobacter species (one of 13). Class 1 integrons and bla_OXA-23-like were not detected. Isolates were susceptible to most antibiotics.

CONCLUSIONS AND CLINICAL IMPORTANCE

The study confirms that Acinetobacter spp. can survive on canine skin, where they may be potential reservoirs for infection. This highlights the importance of good hygiene in veterinary practice, adhering to aseptic principles in surgery, and treatment based on culture and susceptibility testing where possible.

Evolutionary Genetic Analysis Uncovers Multiple Species with Distinct Habitat Preferences and Antibiotic Resistance Phenotypes in the Stenotrophomonas maltophilia Complex

The genus Stenotrophomonas (Gammaproteobacteria) has a broad environmental distribution. Stenotrophomonas maltophilia is its best known species because it is a globally emerging, multidrug-resistant (MDR), opportunistic pathogen. Members of this species are known to display high genetic, ecological and phenotypic diversity, forming the so-called S. maltophilia complex (Smc). Heterogeneous resistance and virulence phenotypes have been reported for environmental Smc isolates of diverse ecological origin. We hypothesized that this heterogeneity could be in part due to the potential lumping of several cryptic species in the Smc. Here we used state-of-the-art phylogenetic and population genetics methods to test this hypothesis based on the multilocus dataset available for the genus at pubmlst.org. It was extended with sequences from complete and draft genome sequences to assemble a comprehensive set of reference sequences. This framework was used to analyze 108 environmental isolates obtained in this study from the sediment and water column of four rivers and streams in Central Mexico, affected by contrasting levels of anthropogenic pollution. The aim of the study was to identify species in this collection, defined as genetically cohesive sequence clusters, and to determine the extent of their genetic, ecological and phenotypic differentiation. The multispecies coalescent, coupled with Bayes factor analysis was used to delimit species borders, together with population genetic structure analyses, recombination and gene flow estimates between sequence clusters. These analyses consistently revealed that the Smc contains at least 5 significantly differentiated lineages: S. maltophilia and Smc1 to Smc4. Only S. maltophilia was found to be intrinsically MDR, all its members expressing metallo-β-lactamases (MBLs). The other Smc lineages were not MDR and did not express MBLs. We also obtained isolates related to S. acidaminiphila, S. humi and S. terrae. They were significantly more susceptible to antibiotics than S. maltophilia. We demonstrate that the sympatric lineages recovered display significantly differentiated habitat preferences, antibiotic resistance profiles and β-lactamase expression phenotypes, as shown by diverse multivariate analyses and robust univariate statistical tests. We discuss our data in light of current models of bacterial speciation, which fit these data well, stressing the implications of species delimitation in ecological, evolutionary and clinical research.

Characterization and Testing the Efficiency of Acinetobacter baumannii Phage vB-GEC_Ab-M-G7 as an Antibacterial Agent

Acinetobacter baumannii is a gram-negative, non-motile bacterium that, due to its multidrug resistance, has become a major nosocomial pathogen. The increasing number of multidrug resistant (MDR) strains has renewed interest in phage therapy. The aim of our study was to assess the effectiveness of phage administration in Acinetobacter baumannii wound infections in an animal model to demonstrate phage therapy as non-toxic, safe and alternative antibacterial remedy. Using classical methods for the study of bacteriophage properties, we characterized phage vB-GEC_Ab-M-G7 as a dsDNA myovirus with a 90 kb genome size. Important characteristics of vB-GEC_Ab-M-G7include a short latent period and large burst size, wide host range, resistance to chloroform and thermal and pH stability. In a rat wound model, phage application effectively decreased the number of bacteria isolated from the wounds of successfully treated animals. This study highlights the effectiveness of the phage therapy and provides further insight into treating infections caused by MDR strains using phage administration.

Prevalence of Multidrug-Resistant Bacteria on Fresh Vegetables Collected from Farmers' Markets in Connecticut

This study determined the prevalence of multidrug-resistant (MDR) Acinetobacter baumannii on fresh vegetables collected from farmers' markets in Connecticut. One hundred samples each of fresh carrots, potatoes, and lettuce were sampled and streaked on selective media, namely Leeds Acinetobacter and MDR Acinetobacter agars. All morphologically different colonies from MDR Acinetobacter agar were identified by using Gram staining, biochemical tests, and PCR. In addition, susceptibility of the isolates to 10 antibiotics commonly used in humans, namely imipenem, ceftriaxone, cefepime, minocycline, erythromycin, colistin-sulfate, streptomycin, neomycin, doxycycline, and rifampin was determined by using an antibiotic disk diffusion assay. The results revealed that only two samples of potato and one sample of lettuce yielded A. baumannii. In addition, all carrot samples were found to be negative for the organism. However, several other opportunistic, MDR human pathogens, such as Burkholderia cepacia (1% potatoes, 5% carrots, and none in lettuce), Stenotrophomonas maltophilia (6% potatoes, 2% lettuce, and none in carrots), and Pseudomonas luteola (9% potatoes, 3% carrots, and none in lettuce) were recovered from the vegetables. Antibiotic susceptibility screening of the isolates revealed high resistance rates for the following: ceftriaxone (6 of 6), colistin-sulfate (5 of 6), erythromycin (5 of 6), and streptomycin (4 of 6) in B. cepacia; colistin-sulfate (11 of 11) and imipenem (10 of 11) in P. luteola; colistin-sulfate (8 of 8), ceftriaxone (8 of 8), cefepime (7 of 8), erythromycin (5 of 8), and imipenem (4 of 8) in S. maltophilia; and imipenem (3 of 3), ceftriaxone (3 of 3), erythromycin (3 of 3), and streptomycin (3 of 3) in A. baumannii. The results revealed the presence of MDR bacteria, including human pathogens on fresh produce, thereby highlighting the potential health risk in consumers, especially those with a compromised immune system.

Sequential outbreaks in a Spanish hospital caused by multiresistant OXA-58-producing Acinetobacter baumannii ST92

The aim of this study was to assess the epidemiology and molecular basis of the infection and dissemination of multidrug-resistant Acinetobacter baumannii (MDRAB) in three sequential outbreaks at the intensive care units (ICUs) of a tertiary university hospital in Granada, Spain, between 2009 and 2011. Strains from all patients infected and/or colonized by MDRAB during outbreak periods were characterized using PFGE and multilocus sequence typing (MLST). The first outbreak appeared in the summer of 2009 involving 38 ICU patients: 25 from a Traumatology-Rehabilitation hospital (TRH) and 13 from a Medical-Surgery hospital (MSH). Between 2010 and 2011, outbreaks were limited to the MSH-ICU, affecting 9 and 11 patients, respectively. Two PFGE types were detected. In the 2009 outbreak, two clones were identified: profile 1 strains were isolated at the TRH, whilst profile 2 was isolated at the MSH. Only one clone was identified in the 2010 and 2011 outbreaks: the profile 2 clone detected at the MSH in 2009. After MLST analysis, a single sequence type (ST92) was identified. This suggested that an endemic strain could evolve and cause localized outbreaks in vulnerable patients. Multiplex PCR for OXA group enzymes yielded a positive result for blaOXA-58-like and blaOXA-51-like genes, and gene sequencing showed the presence of blaOXA-58. However, the absence of ISAba1 upstream of the blaOXA-51-like gene suggested the absence of OXA-51 expression. The susceptibility pattern was not an appropriate method for MDRAB surveillance, as several susceptibility patterns were identified in a single clone. Consequently, molecular methods of characterization are recommended for epidemiological surveillance of MDRAB.

A comprehensive water management program for multicampus healthcare facilities

OBJECTIVE

Develop and implement an effective program for hazard analysis and control of waterborne pathogens at a multicampus hospital with clinics.

DESIGN

A longitudinal study. Several-year study including analysis of results from monitoring and tests of 26 building water systems.

SETTING

Outpatient and inpatient healthcare facilities network.

METHODS

The hazard analysis and critical control point (HACCP) process was used to develop a water management program (WMP) for the hospital campuses. The HACCP method systematically addressed 3 questions: (1) What are the potential waterborne hazards in the building water systems of these facilities? (2) How are the hazards being controlled? (3) How do we know that the hazards have been controlled? Microbiological and chemical tests of building water samples were used to validate the performance of the WMP; disease surveillance data further validated effective hazard control.

RESULTS

Hazard analysis showed that waterborne pathogens were generally in good control and that the water quality was good in all facilities. The hospital network has had several legionellosis cases that were identified as presumptive hospital acquired, but none was confirmed or substantiated by water testing in follow-up investigations. Building water system studies unrelated to these cases showed that pressure tanks and electronic automatic faucets required additional hazard control.

CONCLUSIONS

Application of the HACCP process for long-term building water systems management was practical and effective. The need for critical control point management of temperature, flow, and oxidant (chlorine) residual concentration was emphasized. The process resulted in discovery of water system components requiring additional hazard control.

Quantitative real-time PCR for detection of Acinetobacter baumannii colonization in the hospital environment

A real-time PCR assay was developed for detecting the presence of Acinetobacter baumannii on hospital equipment and compared to conventional bacterial culture using 100 hospital environmental samples. The real-time PCR detected contaminated surfaces in 4 h with high sensitivity (100%) compared to conventional culture. Thirty-eight percent of samples were positive by real-time PCR and negative by bacterial culture (false positives), possibly indicating the widespread presence of bacterial DNA that is not associated with viable bacteria.

Comparison of culture media for detection of Acinetobacter baumannii in surveillance cultures of critically-ill patients

The objective of this study was to evaluate the performance of CHROMagar Acinetobacter when compared to sheep blood agar, MacConkey agar and MacConkey agar with 6 μg/ml of imipenem for the detection of A. baumannii in surveillance cultures of hospitalized patients. We utilized peri-anal swabs and sputum samples from patients admitted to the University of Maryland Medical Center ICUs from December 7 through December 21, 2009. Samples were plated onto four media in the following order: (1) 5% sheep blood agar (SBA), (2) MacConkey agar, (3) MacConkey agar with 6 μg/ml of imipenem, and (4) CHROMagar Acinetobacter (CHROMagar). SBA was the gold standard to which all media was compared. There were 165 samples collected during the study period. SBA and CHROMagar detected 18 of 18 (100%) Acinetobacter and 11 of 11 (100%) MDR-A. baumannii. MacConkey agar detected 16 of 18 (89%) Acinetobacter and 10 of 11 (91%) MDR- A. baumannii while MacConkey agar with 6 μg/ml imipenem detected 9 of 11 (82%) MDR-A. baumannii. CHROMagar did not differentiate MDR- A. baumannii from non-MDR-A. baumannii. CHROMagar may be useful for rapid detection of patients with MDR-A. baumannii if improved upon to better select for MDR-A. baumannii.

Acinetobacter infection--an emerging threat to human health

The genus Acinetobacter comprises a complex and heterogeneous group of bacteria, many of which are capable of causing a range of opportunistic, often catheter-related, infections in humans. However, Acinetobacter baumannii, as well as its close relatives belonging to genomic species 3 ("Acinetobacter pittii") and 13TU ("Acinetobacter nosocomialis"), are important nosocomial pathogens, often associated with epidemic outbreaks of infection, that are only rarely found outside of a clinical setting. These organisms are frequently pandrug-resistant and are capable of causing substantial morbidity and mortality in patients with severe underlying disease, both in the hospital and in the community. Several epidemic clonal lineages of A. baumannii have disseminated worldwide and seem to have a selective advantage over non-epidemic strains. The reasons for the success of these epidemic lineages remain to be elucidated, but could be related to the potential of these organisms to achieve very dynamic reorganization and rapid evolution of their genome, including the acquisition and expression of additional antibiotic resistance determinants, under fluctuating environmental and selective conditions.

Phosphate uptake performance of bacteria isolated from a full-scale Izmir municipal wastewater treatment plant

This study investigated the phosphate uptake capacities of bacteria isolated from aerobic and anaerobic phosphate removal tanks at a municipal wastewater treatment plant in Izmir, Turkey, removing chemical oxygen demand to nitrogen (COD-N) and phosphorus (P) on a full-scale basis. Conventional plating techniques and an enrichment culture method were used to isolate the colonies, with a total of 91 monoculture isolates from the sludge samples being subjected to phosphate uptake studies. A total of 64 of these isolates had high phosphate uptake capacities ranging from 3.7 x 10(10) to 1.0 x 10(-12) mg PO4(3-) cell(-1), and only 11 of the strains with high phosphate uptake were Gram-negative. The highest phosphorus uptake value was 3.7 x 10(-10) mg PO4(-3) cell(-1), which was achieved by Gram-positive bacteria. Gram-negative strains were identified as Acinetobacter baumannii with a 99% probability and as Pseudomonas aeruginosa with a 96-98% probability (API 20 NE).

Screening for Acinetobacter baumannii colonization by use of sponges

There is currently no consensus method for the active screening of Acinetobacter baumannii. The use of swabs to culture nostrils, pharynx, and skin surface of various anatomical sites is known to yield less-than-optimal sensitivity. In the present study, we sought to determine whether the use of sterile sponges to sample large areas of the skin would improve the sensitivity of the detection of A. baumannii colonization. Forty-six patients known to be colonized with A. baumannii, defined by a positive clinical culture for this organism as defined by resistance to more than two classes of antimicrobials, participated in the study. The screening sites included the forehead, nostrils, buccal mucosa, axilla, antecubital fossa, groin, and toe webs with separate rayon swabs and the forehead, upper arm, and thigh with separate sponges. Modified Leeds Acinetobacter medium (mLAM) agar plates that contained vancomycin and either aztreonam or ceftazidime were used as the selective medium. An enrichment culture grown overnight substantially increased the sensitivity for most sites. The sensitivity ranged between 69.6 and 82.6% for individual sponge sites and 21.7 to 52.2% for individual swab sites when mLAM plates with ceftazidime were inoculated after a 24-h enrichment period. The sponge and swab sites with the best sensitivity were the leg and the buccal mucosa, respectively (82.6% and 52.2%; P = 0.003). The combined sensitivity for the upper arm and leg with a sponge was 89.1%. The novel screening method using sterile sponges was easy to perform and achieved excellent sensitivity for the detection of A. baumannii colonization.

Microbial exposure early in life regulates airway inflammation in mice after infection with Streptococcus pneumoniae with enhancement of local resistance

The immunological explanation for the “hygiene hypothesis” has been proposed to be induction of T helper 1 (Th1) responses by microbial products. However, the protective results of hygiene hypothesis-linked microbial exposures are currently shown to be unlikely to result from a Th1-skewed response. Until now, effect of microbial exposure early in life on airway innate resistance remained unclear. We examined the role of early life exposure to microbes in airway innate resistance to a respiratory pathogen. Specific pathogen-free weanling mice were nasally exposed to the mixture of microbial extracts or PBS (control) every other day for 28 days and intratracheally infected with Streptococcus pneumoniae 10 days after the last exposure. Exposure to microbial extracts facilitated colonization of aerobic gram-positive bacteria, anaerobic microorganisms, and Lactobacillus in the airway, compared with control exposure. In pneumococcal pneumonia, the exposure prolonged mouse survival days by suppressing bacterial growth and by retarding pneumococcal blood invasion, despite significantly low levels of leukocyte recruitment in the lung. Enhancement of airway resistance was associated with a significant decrease in production of leukocyte chemokine (KC) and TNFα, and suppression of matrix metalloproteinase (MMP-9) expression/activation with enhancement of tissue inhibitor of MMP (TIMP-3) activation. The exposure increased production of IFN-γ, IL-4, and monocyte chemoattractant-1 following infection. Furthermore, expression of Toll-like receptor 2, 4, and 9 was promoted by the exposure but no longer upregulated upon pneumococcal infection. Thus, we suggest that hygiene hypothesis is more important in regulating the PMN-dominant inflammatory response than in inducing a Th1-dominant response.

Wastewater treatment contributes to selective increase of antibiotic resistance among Acinetobacter spp

The occurrence and spread of multi-drug resistant bacteria is a pressing public health problem. The emergence of bacterial resistance to antibiotics is common in areas where antibiotics are heavily used, and antibiotic-resistant bacteria also increasingly occur in aquatic environments. The purpose of the present study was to evaluate the impact of the wastewater treatment process on the prevalence of antibiotic resistance in Acinetobacter spp. in the wastewater and its receiving water. During two different events (high-temperature, high-flow, 31 degrees C; and low-temperature, low-flow, 8 degrees C), 366 strains of Acinetobacter spp. were isolated from five different sites, three in a wastewater treatment plant (raw influent, second effluent, and final effluent) and two in the receiving body (upstream and downstream of the treated wastewater discharge point). The antibiotic susceptibility phenotypes were determined by the disc-diffusion method for 8 antibiotics, amoxicillin/clavulanic acid (AMC), chloramphenicol (CHL), ciprofloxacin (CIP), colistin (CL), gentamicin (GM), rifampin (RA), sulfisoxazole (SU), and trimethoprim (TMP). The prevalence of antibiotic resistance in Acinetobacter isolates to AMC, CHL, RA, and multi-drug (three antibiotics or more) significantly increased (p<0.01) from the raw influent samples (AMC, 8.7%; CHL, 25.2%; RA, 63.1%; multi-drug, 33.0%) to the final effluent samples (AMC, 37.9%; CHL, 69.0%; RA, 84.5%; multi-drug, 72.4%), and was significantly higher (p<0.05) in the downstream samples (AMC, 25.8%; CHL, 48.4%; RA, 85.5%; multi-drug, 56.5%) than in the upstream samples (AMC, 9.5%; CHL, 27.0%; RA, 65.1%; multi-drug, 28.6%). These results suggest that wastewater treatment process contributes to the selective increase of antibiotic resistant bacteria and the occurrence of multi-drug resistant bacteria in aquatic environments.

Acinetobacter baumannii: emergence of a successful pathogen

Acinetobacter baumannii has emerged as a highly troublesome pathogen for many institutions globally. As a consequence of its immense ability to acquire or upregulate antibiotic drug resistance determinants, it has justifiably been propelled to the forefront of scientific attention. Apart from its predilection for the seriously ill within intensive care units, A. baumannii has more recently caused a range of infectious syndromes in military personnel injured in the Iraq and Afghanistan conflicts. This review details the significant advances that have been made in our understanding of this remarkable organism over the last 10 years, including current taxonomy and species identification, issues with susceptibility testing, mechanisms of antibiotic resistance, global epidemiology, clinical impact of infection, host-pathogen interactions, and infection control and therapeutic considerations.

Molecular epidemiology of Acinetobacter baumannii spread in an adult intensive care unit under an endemic setting

BACKGROUND

Acinetobacter baumannii (Ab) clones I, III, and IV were recovered in several Buenos Aires City hospitals. We investigated the prevalence of these clones with epidemic behavior (EB) in our intensive care unit (ICU) under an endemic setting and its spread.

METHODS

A 10-week prospective cohort study including surveillance cultures of newly admitted patients was conducted. Air, environment, and staff hands were weekly screened. In the seventh week, a new environmental cleaning protocol and a staff hand hygiene reeducation program were implemented.

RESULTS

Almost 15% of all screening samples (159/1042) were Ab positive. Up to the seventh week, carbapenem-resistant clone If was the main one recovered from patients, environmental frequently touched surfaces (EFTS), and staff hands screening samples. Few air samples were Ab positive. Clone I was also isolated from patients at admission. After the seventh week, a significant reduction of EFTS contamination and of clone If isolation was observed. During the last 3 weeks, clone I was no longer isolated from patients. Instead, the newly identified clone IVb was mainly cross transmitted. It was also recovered from staff hands and from EFTS. In the last week, clone If was again isolated from 1 bed rail.

CONCLUSION

Patients with EB clones-positive culture at admission provide verification that interhospital patient transfers play a role in these clones spread. However, subtypes such as clone If seem to be endemic in our ICU. EFTS showed to have potential for EB clones transmission via transient staff hand carriage. Transmission did not involve airborne route.

Air ionisation and colonisation/infection with methicillin-resistant Staphylococcus aureus and Acinetobacter species in an intensive care unit

OBJECTIVE

To determine effect of negative air ions on colonisation/infection with methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter species in an intensive care unit.

DESIGN

Prospective single-centre cross-over study in an adult general intensive care unit.

PATIENTS

201 patients whose stay on the unit exceeded 48 hour's duration.

INTERVENTION

Six negative air ionisers were installed on the unit but not operational for the first 5 months of the study (control period). Devices were then operational for the following 5.5 months.

MEASUREMENTS AND RESULTS

30 and 13 patients were colonised/infected with MRSA and Acinetobacter spp., respectively, over 10.5 months. No change in MRSA colonisation/infection was observed compared with the 5 month control period. Acinetobacter cases were reduced from 11 to 2 (p=0.007).

CONCLUSION

Ionisers may have a role in the prevention of Acinetobacter infections.

Prevalence of Acinetobacter baumannii and other Acinetobacter spp. in faecal samples from non-hospitalised individuals

In total, 226 individuals from the community were investigated for faecal carriage of Acinetobacter spp. by broth enrichment culture, followed by growth on blood agar and/or Leeds Acinetobacter Medium (LAM). Acinetobacter baumannii was isolated on both LAM and blood agar from one of 100 specimens in the UK and one of 126 specimens in The Netherlands. The predominant species were Acinetobactor johnsonii and genomic sp. 11, which were cultured from 22 and five specimens, respectively. A. baumannii did not seem to be widespread in the faecal flora of individuals in the community.

Gastritis and hypergastrinemia due to Acinetobacter lwoffii in mice

In mouse models and humans, Helicobacter pylori is associated with an increase in serum gastrin and gastrin-expressing (G) cells with a concomitant decrease in somatostatin-expressing D cells. Inflammation of the gastric mucosa can progress to metaplastic changes in the stomach and to decreased colonization by H. pylori and increased colonization by non-H. pylori organisms. In addition, about 20% of individuals with chronic gastritis are H. pylori negative, suggesting that other organisms may induce gastritis. Consistent with this hypothesis, we report here that Acinetobacter lwoffii causes the same histologic changes as does H. pylori. Gastric epithelial cells were isolated from the entire stomach by an enzymatic method for quantitation by both flow cytometry and morphometric analysis. Two months after mice were inoculated with H. pylori or A. lwoffii, the mucosal T- and B-cell numbers significantly increased. After 4 months of infection, there was a threefold increase in the number of G cells and a doubling in the number of parietal cells. A threefold decrease in the number of D cells occurred in H. pylori- and A. lwoffii-infected mice. Plasma gastrin levels increased after both H. pylori and A. lwoffii infection. Histology revealed the presence of inflammation in the gastric mucosa with both A. lwoffii and H. pylori infection. A periodic acid-Schiff stain-alcian blue stain revealed mucous gland metaplasia of the corpus. Collectively, the results demonstrate that gastritis and hypergastrinemia are not specific for H. pylori but can be induced by other gram-negative bacteria capable of infecting the mouse stomach.

Gastritis and hypergastrinemia due to Acinetobacter lwoffii in mice

In mouse models and humans, Helicobacter pylori is associated with an increase in serum gastrin and gastrin-expressing (G) cells with a concomitant decrease in somatostatin-expressing D cells. Inflammation of the gastric mucosa can progress to metaplastic changes in the stomach and to decreased colonization by H. pylori and increased colonization by non-H. pylori organisms. In addition, about 20% of individuals with chronic gastritis are H. pylori negative, suggesting that other organisms may induce gastritis. Consistent with this hypothesis, we report here that Acinetobacter lwoffii causes the same histologic changes as does H. pylori. Gastric epithelial cells were isolated from the entire stomach by an enzymatic method for quantitation by both flow cytometry and morphometric analysis. Two months after mice were inoculated with H. pylori or A. lwoffii, the mucosal T- and B-cell numbers significantly increased. After 4 months of infection, there was a threefold increase in the number of G cells and a doubling in the number of parietal cells. A threefold decrease in the number of D cells occurred in H. pylori- and A. lwoffii-infected mice. Plasma gastrin levels increased after both H. pylori and A. lwoffii infection. Histology revealed the presence of inflammation in the gastric mucosa with both A. lwoffii and H. pylori infection. A periodic acid-Schiff stain-alcian blue stain revealed mucous gland metaplasia of the corpus. Collectively, the results demonstrate that gastritis and hypergastrinemia are not specific for H. pylori but can be induced by other gram-negative bacteria capable of infecting the mouse stomach.

Allergy development and the intestinal microflora during the first year of life

BACKGROUND

The intestinal microflora is a likely source for the induction of immune deviation in infancy.

OBJECTIVE

The purpose of this study was to prospectively relate the intestinal microflora to allergy development in 2 countries differing with respect to the prevalence of atopic diseases.

METHODS

Newborn infants were followed prospectively through the first 2 years of life in Estonia (n = 24) and Sweden (n = 20). By that age, 9 Estonian and 9 Swedish infants had developed atopic dermatitis and/or positive skin prick test results. Stool samples were obtained at 5 to 6 days and at 1, 3, 6, and 12 months, and 13 groups of aerobic and anaerobic microorganisms were cultivated through use of standard methods.

RESULTS

In comparison with healthy infants, babies who developed allergy were less often colonized with enterococci during the first month of life (72% vs 96%; P <.05) and with bifidobacteria during the first year of life (17% to 39% vs 42% to 69%; P <.05). Furthermore, allergic infants had higher counts of clostridia at 3 months (median value, 10.3 vs 7.2 log(10); P <.05). The prevalence of colonization with Staphylococcus aureus was also higher at 6 months (61% vs 23%; P <.05), whereas the counts of Bacteroides were lower at 12 months (9.9 vs 10.6 log(10); P <.05).

CONCLUSION

Differences in the composition of the gut flora between infants who will and infants who will not develop allergy are demonstrable before the development of any clinical manifestations of atopy. Because the observations were made in 2 countries with different standards of living, we believe that our findings could indicate a role for the intestinal microflora in the development of and protection from allergy.

Skin carriage of acinetobacters in Hong Kong

We studied the carriage of Acinetobacter spp. at five superficial sites in 79 patients from two hospitals, in 133 healthy controls from the community (medical students and new nurses), and in 198 student nurses in different classes. A total of 431 isolates from 364 positive sites of 201 subjects and 124 blood culture isolates (1997 to 1998) were genospeciated by amplified ribosomal DNA restriction analysis. Genospecies 3 was the most common species. The carriage rate of student nurses (42 of 131) was significantly lower than that of new nurses from the community (25 of 38) (chi-square test, P = 0.0004; odds ratio [OR], 4.08; 95% confidence limits, 1.78 to 9.41) but not significantly different (P = 0.1) from that of patients in the same hospital (20 of 42). Genospecies from blood cultures and subjects (acute patients and student nurses) from Prince of Wales Hospital were similar to one another but different from subjects from the community or from another hospital (chi-square test, P < 0.0001). Half of the subjects who were positive at at least two sites had different genospecies. Of the 28 sites examined, 68% showed strain variation among isolates of the same genospecies by random amplified polymorphic DNA analysis. Half of the 106 subjects who had samples taken again within 6 weeks or 6 months later were positive only once. In the 17 subjects who were positive on at least two occasions, each occasion yielded different genospecies in 13 subjects. Our results indicate that skin carriage in the majority of healthy subjects is characterized by low density, variation in genospecies and strains, short-term duration, and the typicality of a given locality.

Survival of Acinetobacter baumannii on dry surfaces: comparison of outbreak and sporadic isolates

Acinetobacter spp. are important nosocomial pathogens reported with increasing frequency in outbreaks of cross-infection during the past 2 decades. The majority of such outbreaks are caused by Acinetobacter baumannii. To investigate whether desiccation tolerance may be involved in the ability of certain strains of A. baumannii to cause hospital outbreaks, a blind study was carried out with 39 epidemiologically well-characterized clinical isolates of A. baumannii for which survival times were determined under simulated hospital conditions. The survival times on glass coverslips of 22 strains isolated from eight well-defined hospital outbreaks in a German metropolitan area were compared with the survival times of 17 sporadic strains not involved in outbreaks but rather isolated from inpatients in the same geographic area. All sporadic isolates have been shown by pulsed-field gel electrophoresis to represent different strain types. There was no statistically significant difference between the survival times of sporadic strains of A. baumannii and outbreak strains (27.2 versus 26.5 days, respectively; P < or = 0.44) by the Wilcoxon-Mann-Whitney test. All investigated A. baumannii strains, irrespective of their areas of endemicity or epidemic occurrence, have the ability to survive for a long time on dry surfaces. Antimicrobial susceptibility testing showed that A. baumannii outbreak strains were significantly more resistant to various broad-spectrum antimicrobial agents than sporadic strains. Both desiccation tolerance and multidrug resistance may contribute to their maintenance in the hospital setting and may explain in part their propensity to cause prolonged outbreaks of nosocomial infection.

Ventilation grilles as a potential source of methicillin-resistant Staphylococcus aureus causing an outbreak in an orthopaedic ward at a district general hospital

The spread of methicillin-resistant Staphylococcus aureus (MRSA) in a hospital is thought to be mainly by direct contact. Environmental sources such as exhaust ducting systems have been increasingly recognized as a source for MRSA outbreaks in intensive therapy units. We describe an outbreak of MRSA related to ventilation grilles in an orthopaedic ward. Six patients and one nurse were involved in an outbreak with EMRSA-15 during March 1996. The index case was transferred from a large university hospital in Leeds. One of the patients had shared the same bay with the index case. The rest of the patients were in another bay of the same ward and had no direct contact with the index patient. An environmental source was suspected and the ventilation grilles in boys 1 and 2 were found to be harbouring EMRSA-15. The ventilation system at that time was working on an intermittent cycle from 4 p.m.-8 a.m. Daily shut-down of the system temporarily created a negative pressure, sucking air in from the ward environment into the ventilation system and probably contaminating the outlet grilles. It is likely that contaminated air was blown back into the ward when the ventilation system was started. The system was thoroughly cleaned, appropriate infection control measures were instituted and the ventilation system was put back on a continuous running cycle and the outbreak terminated. Six months after the outbreak no isolates of EMRSA-15 had been made on the ward.

Surveillance of an adult intensive care unit for long-term persistence of a multi-resistant strain of Acinetobacter baumannii

Sporadic infections with Acinetobacter spp., punctuated with prolonged outbreaks of infection involving larger numbers of patients and a particular epidemic strain of Acinetobacter baumannii, have occurred in the adult intensive care unit (ICU) of Nottingham University Hospital since 1985. The aim of this study was to screen patients admitted to the ICU for three or more days during a non-outbreak period in 1994-1995 and to use DNA fingerprinting techniques to compare any isolates of Acinetobacter spp. with isolates obtained from the same ICU during the previous ten years. In the present study, almost 20% of the ICU patients screened during 1994-1995 became colonized with Acinetobacter spp. The commonest species isolated from patients was Acinetobacter baumannii; five different strains were identified by random amplified polymorphic DNA fingerprinting, including the epidemic strain responsible for outbreaks of infection in 1985-1986 and 1992-1993. Environmental sampling yielded Acinetobacter spp. from one or more samples on four occasions; Acinetobacter radioresistens was the commonest species isolated, and Acinetobacter baumannii (not the epidemic strain) was isolated on only one occasion from the environment. The long-term persistence of a potentially epidemic strain in the ICU, even during a non-outbreak period, indicates a need for continued vigilance. Consequently, periodic patient and environmental surveillance, combined with typing of isolates, is recommended for ICUs where significant outbreaks of Acinetobacter infection have occurred in the past.

Impact of Acinetobacter spp. in intensive care units in Great Britain and Ireland

Acinetobacter spp. are of increasing importance as hospital pathogens in intensive care units (ICUs) but it is unclear what clinical impact these bacteria have in Great Britain and Ireland. A survey was carried out by questionnaire on the impact of Acinetobacter in ICUs and the laboratory methods used to identify and type isolates. There were 70 respondents, of whom 25 reported that Acinetobacter had not been recovered from ICU patients within the previous 12 months. The remaining 45 respondents reported that the respiratory tract was the most common site from which these bacteria were isolated, but they were currently endemic in one ICU only. There were considerable differences in methods used to identify Gram-negative bacilli recovered from ICU patients, which may partly explain differences in the reported prevalence of isolates between centres, and 12 laboratories attempted to type isolates by a range of techniques. The availability and use of agreed antibiotic policies specific for ICUs may be particularly important in prevention and control where infection with Acinetobacter is prevalent.

Intestinal microflora of Estonian and Swedish infants

The intestinal microflora of 1-y-old healthy Estonian (n = 27) and Swedish infants (n = 29) was studied by quantitative culture of faecal samples. The major differences were high counts of lactobacilli and eubacteria in the former and increased numbers of clostridia in the latter babies. Bifidobacteria and anaerobic cocci prevailed equally in both groups, while eubacteria and enterococci were the major microorganisms in many Estonian infants and bacteroides and clostridia in many Swedish infants. The microflora of the Estonian infants was in many aspects similar to the flora prevailing in infants of western Europe in the 1960s. The results suggest a shift in the intestinal microflora among infants in western industrialized countries.

Influence of relative humidity and suspending menstrua on survival of Acinetobacter spp. on dry surfaces

Acinetobacter spp. are being reported with increasing frequency as a cause of nosocomial infection and have been isolated from the skin of healthy individuals, patients, hospital staff, dry nonbiotic objects, and different pieces of medical equipment. Factors affecting the survival of Acinetobacter spp. under conditions closely similar to those found in the hospital environment were investigated in the present study to help us understand the epidemiology of nosocomial Acinetobacter infection. Bacterial cells were suspended in distilled water or bovine serum albumin and were dried onto glass coverslips and kept at different relative humidities. Cells washed from coverslips were used to determined viable counts. Freshly isolated strains of Acinetobacter spp. belonging to the clinically important Acinetobacter calcoaceticus-Acinetobacter baumannii complex were found to be more resistant to drying conditions (e.g., 30 days for A. baumannii 16/49) than American Type Culture Collection strains (e.g., 2 days for A. baumannii ATCC 9955). The majority of strains belonging to the Acb complex had survival times similar to those observed for the gram-positive organism Staphylococcus aureus tested in the experiment. Survival times were prolonged for almost all the strains tested when they were suspended in bovine serum albumin (e.g., 60 days for A. baumannii R 447) compared with those for strains suspended in distilled water (11 days for R 447). The survival times for strains at higher relative humidity (31 or 93%) were longer than those for strains of Acinetobacter kept at a relative humidity of 10% (11 days at 31% relative humidity and 4 days at 10% relative humidity for R447). These findings are consistent with the observed tendency of Acinetobacter spp. to survive on dry surfaces, and they can be transferred not only by moist vectors but also under dry conditions in a hospital environment during nosocomial infection outbreaks. The results obtained in the experiment support the previously suggested airborne spread of Acinetobacter spp. in hospital wards and repeated outbreaks after incomplete disinfection of contaminated dry surfaces.