Po-Yu Liu

Clinical Outcome of Mycobacterium abscessus Infection and Antimicrobial Susceptibility Testing

BACKGROUND/PURPOSE Mycobacterium abscessus is the most resistant and rapidly growing mycobacterium and causes a wide range of clinical infectious diseases. The relationship between antimicrobial susceptibility and clinical outcome needs to be further evaluated. METHODS Forty M. abscessus isolates were obtained from clinical specimens of 40 patients at the Taichung Veterans General Hospital from January 2006 to December 2008. Antimicrobial susceptibility testing was performed using the broth microdilution method according to the recommendations of the National Committee for Clinical Laboratory Standards. The clinical manifestations and outcomes were reviewed from medical records. RESULTS Twenty-two patients were diagnosed with M. abscessus infection. Cough (86.3%), hemoptysis (31.8%) and fever (18.1%) were the most common symptoms. The radiographic findings included reticulonodular opacities (50.0%), consolidation (31.8%) and cavitary lesions (18.1%). The 40 isolates were susceptible to amikacin (95.0%), cefoxitin (32.5%), ciprofloxacin (10.0%), clarithromycin (92.5%), doxycycline (7.5%), imipenem (12.5%), moxifloxacin (22.5%), sulfamethoxazole (7.5%) and tigecycline (100%). The rate of treatment failure was 27.3% at the end of the 12(th) month after the start of treatment, although these patients were treated with a combination of clarithromycin and other antimicrobial agents. CONCLUSION M. abscessus is naturally susceptible to clarithromycin and amikacin, variably susceptible to cefoxitin and imipenem, and resistant to most other antimicrobial drugs. Combination therapy with clarithromycin, amikacin and other active antimicrobial agents may lead to clinical improvement; however, the rate of treatment failure is still high.

Antimicrobial Susceptibility and Multiplex PCR Screening of AmpC Genes From Isolates of Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens

BACKGROUND/PURPOSE The emergence of multiple drug resistance in Enterobacteriaceae is of particular concern. The aim of this study was to evaluate the antimicrobial susceptibility and screen for the ampC gene in three members of the Enterobacteriaceae family (Enterobacter cloacae, Citrobacter freundii, and Serratia marcescens) found at Taichung Veterans General Hospital during the past 5 years using multiplex polymerase chain reaction (PCR). METHODS The susceptibility of thirty isolates from each of the three Enterobacteriaceae family members to five antimicrobial agents (ceftazidime, flomoxef, imipenem, moxifloxacin, and colistin) was assessed. The susceptibility was analyzed by disk diffusion, screening and confirmatory tests for extended-spectrum β-lactamases (ESBL) and minimum inhibitory concentration tests according to the recommendations of the Clinical and Laboratory Standards Institute. The detection of ampC genes (3 families, including DHA, EBC and CIT) was performed by multiplex PCR. To detect the coexistence of ESBL genes, PCR was performed using five primer pairs: TEM, SHV, SHV-5, CTX-M-3, and CTX-M-14. RESULTS Of the 90 isolates, 53 (58.9%) were positive in the screening test for ESBL. Resistance genes were detected in 12 (22.6%) of these isolates: ampC gene of DHA type in one E. cloacae isolate and EBC type in three E. cloacae isolates; ampC gene of CIT type in four C. freundii isolates; CTX-M-3-like in one C. freundii isolate and one S. marcescens isolate; TEM in three E. cloacae isolates, three C. freundii isolates and two S. marcescens isolates; SHV in one C. freundii isolate. CONCLUSION Antibiotic phenotypes cannot accurately distinguish the resistance mechanisms caused by ampC or ESBL, and especially in ESBL-ampC combinations. However, PCR is a useful technique for the identification of the different types of resistance genes.

Antimicrobial resistance to cefotaxime and ertapenem in Enterobacteriaceae: the effects of altering clinical breakpoints

INTRODUCTION The Clinical and Laboratory Standards Institute (CLSI) updated its antimicrobial susceptibility testing interpretation criteria for Enterobacteriaceae. This study assessed the effects of clinical breakpoint changes in the CLSI 2009 to 2012 guidelines on antibiotic susceptibility testing reports. METHODOLOGY In total, 2,076 non-duplicate clinical isolates of Enterobacteriaceae were analyzed. The disk diffusion method was used for susceptibility testing. The CLSI 2009-12 clinical breakpoints were applied to determine susceptibility of cefotaxime and ertapenem. Combined-disk testing was used for phenotypic confirmation of extended-spectrum beta-lactamase (ESBL) production. RESULTS In total, Enterobacteriaceae resistance rates to cefotaxime increased from 13.1% using the CLSI 2009 guidelines to 23.6% with the CLSI 2010-12 guidelines, and the resistance rates to ertapenem were 0.4%, 1.0% and 0.8% with CLSI 2009, 2011 and 2012, respectively. Based on the 2010-12 CLSI criteria, all ESBL-producing Escherichia coli and Klebsiella pneumoniae were resistant to cefotaxime. Marked differences in susceptibility to ertapenem between the 2009 CLSI criteria and 2012-12 CLSI criteria were noted in ESBL-producing K. pneumoniae. CONCLUSIONS Breakpoints changes in the updated CLSI guidelines resulted in higher resistance rates to cefotaxime and ertapenem. In addition, the effects were different in individual Enterobacteriaceae species. As a result, clinicians may opt to use alternative antimicrobial agents. Upon implementation of the newer CLSI guidelines, laboratories should be aware of the possible consequences and closely monitor the effects.

Shewanella infection of snake bites: a twelve-year retrospective study

OBJECTIVE: Infections of snake bite wounds by Shewanella are rarely discussed in the medical literature. This study aims to characterize the presentation and management of Shewanella infections in snake bite wounds. METHOD: We retrospectively investigated the microbiology, clinical features, and outcomes of patients with Shewanella infected snake bite wounds admitted to a tertiary medical center from January 1998 to December 2009. RESULTS: Ten patients with Shewanella-infected snake bite wounds were identified. All of the snake bites were caused by cobras. The majority of patients had moderate to severe local envenomation and polymicrobial infections. Shewanella isolates are susceptible to ampicillin-sulbactam, piperacillin-tazobactam, third- and fourth-generation cephalosporins, carbapenems, aminoglycosides, and quinolones but are resistant to penicillin and cefazolin. All of the patients examined had favorable outcomes. CONCLUSION: It is recommended that Shewanella infection be considered in snake bite patients, especially when patients present with moderate to severe local envenomation.

Cobra bite wound infection caused by Shewanella algae

Shewanella wound infections after snake bites are rare. We report the case of a Shewanella algae wound infection associated with a cobra bite in a 27-year-old woman. The isolate was confirmed by sequencing of the 16S ribosomal DNA gene. This case expands the reported spectrum of infection caused by S. algae and raises the possibility that S. algae could be a causative pathogen in wound infections resulting from snake bites.

Culture-independent analysis of liver abscess using nanopore sequencing.

The identification of microbial species has depended predominantly upon culture-based techniques. However, the difficulty with which types of organisms are cultured implies that the grown species may be overrepresented by both cultivation and plate counts. In recent years, culture-independent analysis using high-throughput sequencing has been advocated for use as a point-of-care diagnostic tool. Although it offers a rapid and unbiased survey to characterize the pathogens in clinical specimens, its accuracy is reduced by the high level of contamination of human DNA. In this paper, we propose using a culture-independent analysis for a Klebsiella pneumoniae clinical strain within a liver abscess using nanopore sequencing. Owing to the highly-contaminated cell population within a liver abscess, we managed to reduce the confounding effects of human DNA through the use of DNase and differential centrifugation. Genomic DNA was sequenced through the use of Nanopore MinION sequencer and analyzed using a suite of bioinformatics approaches. K. pneumoniae was successfully identified along with antibiotic-resistant genes. Our results indicate that, by integrating real-time nanopore sequencing and bioinformatics software, real-time pathogen identification in a liver abscess can be achieved.

Shewanella bloodstream infection

To the Editor: We read the very well-written article by Shrishrimal with interest. The author described a case of bacteremia in a hemodialysis patient. Shewanella was isolated from blood obtained through the catheter. We find that two issues require further explanation. First, the article mentioned Shewanella putrefaciens is susceptible to cephalosporins. However, S. putrefaciens is resistant to cefazolin, and the susceptibility to beta-lactam antibiotics is variable, including carbapenems. In the study of S. putrefaciens bacteremia by Brink et al., all isolates were uniformly resistant to cefazolin and cefoxitin. Subsequent studies have largely supported these findings. Chen et al., in their study of S. putrefaciens skin and soft tissue infections, reported that S. putrefaciens is not susceptible to cefazolin. Furthermore, emerging resistance to piperacillin/tazobactam and imipenem during therapy has been reported. Overall, these studies signify the importance of beta-lactam antibiotics resistance in Shewanella, which may affect patient outcomes. Second, the study does not supply the method of identification to show whether the isolates were actually S. putrefaciens. Shewanella algae and S. putrefaciens account for most human Shewanella infections. As many automated identification systems are unable to distinguish between S. putrefaciens and S. algae, a number of reports of human infections described previously as caused by S. putrefaciens were actually S. algae. Nozue et al. showed that 33 of 40 clinical isolates identified tentatively as S. putrefaciens to be S. algae. In addition, pathogenicity study also indicated S. algae to be the more virulent and the predominant species associated with Shewanella infections. The two species can be distinguished by using phenotypic tests, such as growth at 42°C, and in 6% NaCl, nitrite reduction, and susceptibility to colistin. Clinicians should consider the possibility of betalactam antibiotics resistance when prescribing antibiotics in Shewanella infections. Moreover, correct identification is important to our understanding of this organism. Further studies are necessary to its role in immunocompromised patients and adequate treatment strategy.

“Ulnar artery pseudoaneurysm and compartment syndrome formation after snake bite to the left forearm” by Lan Pin et al., Clin Toxicol (Phila) 2017 Nov. 10

[1] Fuchs J, von Dechend M, Mordasini R, et al. A verified spider bite and a review of the literature confirm Indian ornamental tree spiders (Poecilotheria species) as underestimated theraphosids of medical importance. Toxicon. 2014;77:73–77. [2] Ahmed N, Pinkham M, Warrell DA. Symptom in search of a toxin: muscle spasms following bites by Old World tarantula spiders (Lampropelma nigerrimum, Pterinochilus murinus, Poecilotheria regalis) with review. QJM. 2009;102:851–857. [3] Escoubas P, Rash L. Tarantulas: eight-legged pharmacists and combinatorial chemists. Toxicon. 2004;43:555–574. [4] Escoubas P, Diochot S, C el erier ML, et al. Novel tarantula toxins for subtypes of voltage-dependent potassium channels in the Kv2 and Kv4 subfamilies. Mol Pharmacol. 2002;62:48–57. [5] Arachnoboards.com [Internet]; [cited 2017 Sep 7]. Available from http://www.arachnoboards.com/threads/heteroscodra-maculata.11996

Naja atra snakebite in Taiwan

Abstract Background: Naja atra snakebite is uncommon in Taiwan and causes distinct effects on its victims. Although the Taiwan government produces its own specific antivenom, little information on the management of N. atra snakebite is available. Materials and methods: We retrospectively evaluated 183 patients admitted to two medical centers. Of these, 45 were identified as definite cases of N. atra snakebite, 86 as suspected cases, and 52 as clinical cases. Demographic data, symptomatology, and management were compared between these case groups. Results: Symptomatology and management were similar in the three groups. Among the 183 patients, 10 (5.5%) were asymptomatic and nine (4.9%) had transient and partial ptosis or body weakness. The principal effects were local tissue swelling and pain in 173 patients (94.5%), followed by clinically suspected wound infection in 148 (80.9%), skin necrosis in 120 (65.6%), necrotizing soft tissue infection in 77 (42.1%), fever in 59 (32.2%), and gastrointestinal effects in 53 (29%). The median total dose of specific antivenom needed to treat N. atra envenoming was 10 vials. In the envenomed patients, debridement was required in 74 patients (42.8%), fasciotomy/fasciectomy in 46 (26.6%), and finger or toe amputation in seven (4%). The first operation was performed at a median of 3.5 days after the bite. Discussion and conclusions: Based on these typical manifestations, clinical diagnosis of N. atra snakebites may be feasible and practical. In contrast to other snakes of Elapidae family, N. atra bite did not cause serious neurological effects. Early surgical consultation should be obtained because half of the patients underwent surgery due to infectious complications. Acute compartment syndrome was the surgical indication in rare cases; however, overestimation of the incidence may have occurred. This syndrome should be confirmed by serial intracompartmental pressure monitoring instead of only physical examination, and a sufficient dose of antivenom should be given prior to surgical decompression.

Characteristics and Phylogeny of Shewanella haliotis Isolated from Cultivated Shellfish in Taiwan

Shewanella haliotis is an emerging human pathogen. Many infectious cases were linked to shellfish ingestion or aquatic exposure. Therefore, it is important to study the phylogeny and distribution of S. haliotis in shellfish aquaculture. We investigated the distribution of S. haliotis in cultivated shellfish farming in Taiwan in which S. haliotis was found in the shellfish from all sampling sites. S. haliotis was identified in cultivated shellfish by 16S rRNA gene sequencing, such as abalone (Haliotis diversicolor), clam (Meretrix lusoria), and oyster (Crassostrea gigas). This study highlighted the contamination of S. haliotis in cultivated shellfish and importance of further study regarding the biodiversity and pathogenesis of S. haliotis.