Exploring a photo-acousto-optic effect for noncontacting photoacoustic sensing.

To avoid the use of ultrasound transducers and coupling gel in photoacoustic microscopy (PAM), we propose photo-acousto-optic tomography (PAOT) for noncontact photoacoustic (PA) sensing. The process consists of two parts. The first portion is the same as typical PAM, which employs a pulsed laser to induce acoustic waves. The difference from typical methods lies in the second part of the process, which applies a DC beam, rather than a conventional transducer, to sense the PA signal. A two-beam optical microscope system was designed to verify the PAOT effect, whereby an AC spot acted as the source to induce a PA signal, while a DC beam is applied to induce the acousto-optic effect for detection of the acoustic wave. We demonstrated the preliminary result that 5-100 Hz AC radiation could derive PA waves in a water-like medium along with detection sensitivity as high as 4.9%-10.0%; besides, the signal waveform could be detected by a DC spot 10-100 µm away for noncontact sensing with detection sensitivity of about 3.7%-10.4%. Without the need for a transducer or coupling gel, PAOT has the potential to modify conventional PAM into a pure optical system, which could make PA imaging more promising in practical applications.

Resistance Phenotype and Molecular Epidemiology of Carbapenem-Resistant Klebsiella pneumoniae Isolates in Shanghai.

Background: The emergence and wide global spread of carbapenem-resistant Klebsiella pneumoniae (CRKP) isolates are of great concern, and the aim of this study was to investigate drug resistance, molecular epidemiology, and genetic relationship of CRKP isolates from patients in Shanghai, China. Methods: A retrospective study was conducted from April 2018 to July 2019, and a total of 133 CRKP isolates were collected. Antimicrobial susceptibility was determined by VITEK-2 automated microbiology analyzer platform (bioMérieux, France) and the broth microdilution method. Polymerase chain reaction assays were used to investigate the presence of drug resistance genes. A modified carbapenem inactivation method was performed to detect carbapenemases. Multilocus sequence typing and pulsed-field gel electrophoresis (PFGE) were conducted for genetic relatedness of 50 CRKP isolates selected. Results: Among 670 isolates of K. pneumoniae, 133 (19.9%) strains were identified as CRKP, of which, 76.7% (102/133) strains were isolated from intensive care units (ICUs). All the 133 CRKP isolates were found to be carbapenemase-producers and harbor blaKPC-2 gene. No other carbapenemase genes of blaNDM, blaOXA-48, blaVIM, and blaIMP were detected. Furthermore, ß-lactamase genes of blaSHV, blaCTX, and blaTEM were the most common resistance-associated genes among these KPC-2 producing isolates. All the 133 CRKP strains displayed >95% of resistance to cephalosporins and carbapenems, except for gentamicin, trimethoprim-sulfamethoxazole, amikacin, tigecycline and colistin, and ceftazidime-avibactam. The most common sequence type was ST11, accounting for 90.0% of the 50 CRKP selected, followed by ST15 (10.0%). PFGE analysis clustered the 50 KPC-2-producing isolates into seven (A-G) distinct clonal clusters at 85% cutoff. Of which, A and G were the two major clusters, accounting for the majority of the strains collected in emergency ICU and neurosurgical ICU. And all the strains of clusters D and E were collected in cardiothoracic surgery ICU, except for one strain collected in one outpatient. Conclusion: The KPC-2-producing K. pneumoniae belonged to ST11 was widely disseminated in ICUs, and active and effective surveillance of infection control strategies was initiated to limit the spread of CRKP strains.

Fluoroquinolone Resistance Mechanisms in Shigella Isolates in Shanghai, China, Between 2010 and 2015.

OBJECTIVES: This study aimed to investigate the antimicrobial susceptibility of Shigella isolated in Shanghai, China and to determine the genetic basis of its resistance to fluoroquinolones. MATERIALS AND METHODS: A total of 402 strains of Shigella, including 145 Shigella flexneri and 257 Shigella sonnei isolates, were analyzed. The Kirby-Bauer disk diffusion method was used to determine the susceptibility of the strains to 13 antimicrobials. Minimum inhibitory concentration of ciprofloxacin was determined by E-test. Mutations within the quinolone resistance-determining regions (QRDRs) of gyrA and parC and in the plasmid-mediated quinolone resistance (PMQR) genes, including qnrA, qnrB, qnrS, and aac (6')-Ib-cr, were detected by polymerase chain reaction. All the products were then sequenced. RESULTS: Most of the Shigella isolates were found to be resistant to nalidixic acid (96.4%), streptomycin (96.4%), ampicillin (86.2%), tetracycline (79.8%), and sulfamethoxazole/trimethoprim (80.6%). S. flexneri isolates showed a significantly higher resistance to cefepime (33.6%), ciprofloxacin (54.2%), norfloxacin (34.1%), and levofloxacin (12.1%) compared with that observed for the S. sonnei strains (χ2 analysis, p < 0.05). Three mutations (Ser83, Asp87, and His211) in gyrA and one mutation (Ser80) in parC were detected. Of 257 S. sonnei isolates, 11.7% possessed gyrA mutations and 2% had parC mutations. Of 145 S. flexneri isolates, 98.6% possessed gyrA mutations and 97.9% had parC mutations. The plasmid-mediated resistance genes of qnrS and aac (6')-Ib-cr were detected among 17 strains (4.2%). CONCLUSIONS: The mutation percentage within the QRDR of S. flexneri was as high as 98.6 in gyrA and 97.9 in parC. The significant abundance of mutations within QRDRs conferred high levels of fluoroquinolone resistance. Moreover, the PMQR genes, particularly qnrS, played an important role in the decreased susceptibility of Shigella to fluoroquinolones.

[A micro-culture method for continuous observation of free-living amoebae].

OBJECTIVE: To establish a method for co-culture of amoebae and endosymbionts, also for continuously observing the microphenotype of amoebae. METHODS: 24 wells culture plate with cover glass on the wells was used as containers. Amoebae and Candida albicans were co-cultured in microdrop of medium in the wells at 37 degrees C, and observed under x1000. RESULTS: Continuous observation revealed trophozoites in various shapes like letters T, K, or Y, their movement and ingestion phenomenon were observed. CONCLUSION: The micro-culture method is useful in observing the amoebal morphology and its phagocytic process to Candida albicans.

[Gimenez staining: a rapid method for initial identification of legionella pneumophila in Amoeba trophozoite].

OBJECTIVE: To establish a rapid staining method for facilitating initial identification of Legionella pneumophila in amoebal trophozoite. METHODS: Acanthamoeba polyphaga and Legionella pneumophila were co-cultured under laboratory condition. At consecutive time points during the culture, smears of the cultured products were made on glass slides for staining purposes. Different types of stainings including Gram's staining, Gimenez staining, Giemsa staining and immunofluorescence were used to determine the best method for the identification of amoebal pathogens. RESULTS: Gimenez staining technique is simpler and yields better results as compared with the other three stainings. Gimenez stain gives the best color and contrast for amoeba and amoebal Legionella Amoeba trophozoites and/or cysts showed a distinct purplish blue with amoebal Legionella in red. Amoebal Legionella can be distinguished clearly at an earlier time of co cul ture, providing a proper sensitivity. It takes only 10 minutes to finish the operation. The other techniques require the use of expensive reagents, are relatively time-consuming, and involve complex staining procedures. CONCLUSION: Gimenez staining is of value for the initial identification of amoebal pathogens, and it is suitable for laboratory diagnosis.

[Characterization of phenotype and molecular characteristics on Vibrio cholerae strains isolated in Shanghai, 1962-2011].

OBJECTIVE: To describe the phenotype and molecular characteristics of Vibrio (V.) cholerae strains isolated in Shanghai, from 1962 to 2011. METHODS: K-B test was used to investigate the antibiotic resistance of V. cholerae strains. PCR was applied to detect seven virulence-related genes including cholera toxin (ctxA), zonula occludens toxin (zot), accessory cholera enterotoxin (ace), hemolysin (hlyA), toxin-coregulated pilus (tcpA) outer membrane protein (ompU) and the regulatory protein genes (toxR). Genetic relation was assessed by pulsed-field gel electrophoresis (PFGE) and the patterns were clustered by BioNumerics software. RESULTS: V. cholerae strains isolated from 1962 to 1996 were sensitive to most of the antibiotics. However, the strains isolated from 2005 to 2011 were resistant to many antibiotics. V. cholerae O139 group showed higher prevalence of resistance to several antibiotics compared with O1 group, and the resistance rate of the O139 toxigenic isolates was higher than that of the non-toxigenic isolates. Most of the O1 strains isolated from 2005 to 2011 were non-toxigenic while O139 strains isolated from 2005 to 2011 were almost toxigenic. There were no strains of ctxA+ detected from the rivers from 2005 to 2011. Main gene type of the O1 strains detected from the aquatic products was hlyA+ toxR+ ompU+, while that of the O139 strains was hlyA+ toxR+ ompU+ ctxA+ ace+ zot+ tcpA+. Using PFGE, 222 V. cholerae strains were subtyped into 121 molecular types. O139 strains were divided to three clusters and O1 strains to five clusters. CONCLUSION: The characteristics of V. cholerae strains isolated in Shanghai from 1962 to 2011 showed great changes, suggesting that more attention should be paid to the multiplication on antibiotic resistance of V. cholerae strains.

[Study on the growth of Vibrio cholerae O139 within Acanthamoeba polyphaga and its survival in the cysts in low temperature].

OBJECTIVE: To determine whether Acanthamoeba polyphaga could affect the survival and growth of Vibrio cholerae O139 in low temperature. METHODS: V. cholerae O139 was co-cultured with the Acanthamoeba polyphaga to be examined on its intracellular growth and survival rate within cysts at low temperature, using methods as Gram-staining, electron microscope and passage culture. RESULTS: V. cholerae O139 were observed to enter into the trophozoites and grow the within the vacuoles after 8 hour incubation with Acanthamoeba polyphaga. The germs survived in the vacuole and/or endo-layer of wall and could be re-isolated from the excystment of Acanthamoeba polyphaga. At 30 degrees C, V. cholerae O139 could survive for 120 days with the amoeba while less than 45 days in PAS. At 4 degrees C, the number of viable bacteria decreased and reached undetectable levels for both study and control groups after a 30-day incubation. V. cholerae O139 could be re-isolated from the 30-, 45-, 60- and 75-day's infected cysts after excystment. However the ability of excystment for 90-day's infected cysts decreased and V. cholerae O139 within the cyst could not be isolated again because the amoebae had lysed. CONCLUSION: These findings indicated that V. cholerae O139 could grow within Acanthamoeba polyphaga and the survival time could be increased in the cysts at low temperature. It seemed that Acanthamoeba can provide an environmental reservoir for V. cholerae O139.