Changing trends in antimicrobial resistance of major bacterial pathogens, 1985-2005: a study from a medical center in northern Taiwan

Crystal violet-based assay for the assessment of bacterial biofilm formation in medical tubing

Crystal violet-based assay is widely used to evaluate the early stages of bacterial biofilm formation. Here, we modified it to study biofilm formation in medical tubing. While cost-effective and requiring no sophisticated equipment, our method provided quantitative and qualitative distinctions between the ability of four bacterial strains to colonize PVC catheters.

Colistin Resistance of Pseudomonas aeruginosa Isolated from Snakes in Taiwan

This study included fifty-eight isolates of P. aeruginosa from the oral cavity of snakes that were recruited from clinical cases, captive and wild snakes. The minimum inhibitory concentrations (MICs) for the determination of susceptibility were identified by the broth microdilution method. Polymerase chain reaction (PCR) was employed to detect β-lactamases genes. With regard to antipseudomonal antibiotics, the lowest nonsusceptible rates were in aztreonam (15%), piperacillin/tazobactam (12%), and amikacin (9%). The nonsusceptible rates were high in gentamicin (33%) and colistin (55%). Meanwhile, bla_TEM presented in 100% of isolates where bla_AmpC, bla_OXA-1, and bla_OXA-10 came at 94.8%, 89.7%, and 27.6%, respectively. Emergence of multidrug resistant (MDR) strains and colistin-resistant strains highlights the potential breach of public health as P. aeruginosa could be transmitted through either direct contact or indirect dissemination through the environment. This study reports that the highly resistant P. aeruginosa from snakes' oral cavity were discovered for the very first time in Taiwan.

Evaluation of a matrix-assisted laser desorption ionization-time of flight mass spectrometry assisted, selective broth method to screen for vancomycin-resistant enterococci in patients at high risk

BACKGROUND

Bile esculin azide with vancomycin (BEAV) medium is a sensitive, but slightly less specific method for vancomycin-resistant enterococci (VRE) screening. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is a rapid method for identification of clinical pathogens. This study aimed to assess the performance of a novel combination screening test for VRE, using BEAV broth combined with MALDI-TOF MS.

MATERIALS AND METHODS

Clinical specimens were collected from patients at risk of VRE carriage, and tested by the novel combination method, using selective BEAV broth culture method followed by MALDI-TOF MS identification (SBEAVM). The reference method used for comparison was the ChromID VRE agar method.

RESULTS

A total of 135 specimens were collected from 78 patients, and 63 specimens tested positive for VRE positive using the ChromID VRE method (positive rate 46.7%). The sensitivity, specificity, positive predictive value, and negative predictive value of SBEAVM method after an incubation period of 28 hours were 93.7%, 90.3%, 89.4%, and 94.2%, respectively. The SBEAVM method when compared to the ChromID VRE method had a shorter turnaround time (29 vs. 48-72 hours) and lower laboratory cost ($2.11 vs. $3.23 per test).

CONCLUSIONS

This study demonstrates that SBEAVM is a rapid, inexpensive, and accurate method for use in VRE screening.

Impact of pneumococcal conjugate vaccine in children on the serotypic epidemiology of adult invasive pneumococcal diseases in Taiwan

BACKGROUND

Invasive pneumococcal disease (IPD) causes significant morbidity and mortality, especially in children and older adults. Pneumococcal 7-valent and 13-valent conjugate vaccines (PCV7 and PCV13) were introduced in Taiwan in 2005 and 2011, respectively, for children. This study was conducted to evaluate the impact of PCV administered in children on adult IPD.

METHODS

From the logbooks of microbiology laboratories, we retrospectively retrieved Streptococcus pneumoniae isolates, collected from normally sterile sites in adult patients. One hundred and fifty-seven consecutive, nonduplicated isolates were collected from one hospital during 2001 and 2003 (pre-PCV period) and 150 isolates from three hospitals from July 2011 to June 2015 (post-PCV period). Serotypes were determined by Quellung test.

RESULTS

Among the 307 isolates, 31 serotypes/serogroups were identified. PCV7 serotypes, particularly types 14 (31.2%), 23F (19.7%) and 6B (12.7%) dominated in the pre-PCV period (78.3%) but significantly decreased in the post-PCV period (36%) (p < 0.01). PCV13 specific serotypes (PCV13-PCV7) significantly increased from 7% of the isolates in the pre-PCV period to 28.7% of the isolates in the post-PCV period (p < 0.001), particularly type 19A (from 0.6% to 10%) and 6A (from 0 to 6.7%). Serotype 15B also increased significantly from 0.6% to 6.7% (p < 0.01). Nonvaccine serotypes increased significantly in the post-PCV period (11.5% to 22.0%, p < 0.05), particularly type 15A (from 0 to 4.4%, p < 0.01).

CONCLUSION

Serotype distribution of adult IPD in Taiwan has evolved after the introduction of PCV in children, indicating an indirect impact in adults. Continuous surveillance after the PCV13 vaccination program in children is needed.

Dynamic change of surface microbiota with different environmental cleaning methods between two wards in a hospital

Terminal disinfection and daily cleaning have been performed in hospitals in Taiwan for many years to reduce the risks of healthcare-associated infections. However, the effectiveness of these cleaning approaches and dynamic changes of surface microbiota upon cleaning remain unclear. Here, we report the surface changes of bacterial communities with terminal disinfection and daily cleaning in a medical intensive care unit (MICU) and only terminal disinfection in a respiratory care center (RCC) using 16s ribosomal RNA (rRNA) metagenomics. A total of 36 samples, including 9 samples per sampling time, from each ward were analysed. The clinical isolates were recorded during the sampling time. A large amount of microbial diversity was detected, and human skin microbiota (HSM) was predominant in both wards. In addition, the colonization rate of the HSM in the MICU was higher than that in the RCC, especially for Moraxellaceae. A higher alpha-diversity (p = 0.005519) and a lower UniFrac distance was shown in the RCC due to the lack of daily cleaning. Moreover, a significantly higher abundance among Acinetobacter sp., Streptococcus sp. and Pseudomonas sp. was shown in the RCC compared to the MICU using the paired t test. We concluded that cleaning changes might contribute to the difference in diversity between two wards.

Correlation between the number of Pro-Ala repeats in the EmrA homologue of Acinetobacter baumannii and resistance to netilmicin, tobramycin, imipenem and ceftazidime

Acinetobacter baumannii coccobacilli are dangerous to patients in intensive care units because of their multidrug resistance to antibiotics, developed mainly in the past decade. This study aimed to examine whether there is a significant correlation between the number of Pro-Ala repeats in the CAP01997 protein, the EmrA homologue of A. baumannii, and resistance to antibiotics. A total of 79 multidrug-resistant A. baumannii strains isolated from patients were analysed. Resistance to antibiotics was determined on Mueller-Hinton agar plates using the Kirby-Bauer disk diffusion method. The number of CCTGCA repeats encoding Pro-Ala repeats in CAP01997 was determined by PCR and capillary electrophoresis. The 3D models of CAP01997 containing Pro-Ala repeats were initially generated using RaptorX Structure Prediction server and were assembled with EasyModeller 4.0. The models were embedded in a model bacterial membrane based on structural information from homologous proteins and were refined using 100-ns molecular dynamics simulations. The results of this research show significant correlation between susceptibility to netilmicin, tobramycin and imipenem and the number of repeated Pro-Ala sequences in the CAP01997 protein, a homologue of the Escherichia coli transporter EmrA. Predicted structures suggest potential mechanisms that confer drug resistance by reshaping the cytoplasmic interface between CAP01997 protein and the critical component of the multidrug efflux pump homologous to EmrB. Based on these results, we can conclude that the CAP01997 protein, an EmrA homologue of A. baumannii, confers resistance to netilmicin, tobramycin and imipenem, depending on the number of Pro-Ala repeats.

The experience of intramuscular benzathine penicillin for prophylaxis of recurrent cellulitis: A cohort study

BACKGROUND/PURPOSE

Recurrent cellulitis is an important clinical issue but the optimal strategy for prophylaxis is not determined. Intramuscular benzathine penicillin at a 4-week interval had been adopted in our hospital and the study was conducted to evaluate the efficacy.

METHODS

From January 1, 2009 to May 31, 2013, all patients aged ≥ 18 year, with a history of recurrent cellulitis and having received at least three shots of intramuscular benzathine penicillin for prophylaxis were retrospectively recruited for analysis. Two treatment periods (prophylaxis period and nonprophylaxis period) were defined. The effects of benzathine penicillin prophylaxis and patient characteristics on the incidence rate of recurrent cellulitis were analyzed using Poisson regression model.

RESULTS

A total of 72 patients were enrolled, including 26 (36.1%) men. The most common underlying conditions were past surgery at the proximal side of the affected limb (38, 52.8%), malignancy (31, 43.1%), and diabetes mellitus (24, 33.3%). The incidence rate of recurrent cellulitis in the prophylaxis period was 0.73 episode/patient-year, significantly lower than that of 1.25 episodes/patient-year in the nonprophylaxis period (p < 0.001). Tinea pedis was a significant factor associated with increasing incidence of recurrent cellulitis in our cohort.

CONCLUSION

Intramuscular benzathine penicillin at a 4-week interval may be an effective prophylactic strategy to reduce the incidence of cellulitis. Further studies are necessary to determine the factors associated with failure of prophylaxis as well as optimal individualized dosage and dosing interval of the prophylactic agent.

Reversion of antibiotic resistance by inhibiting mecA in clinical methicillin-resistant Staphylococci by antisense phosphorothioate oligonucleotide

Methicillin-resistant Staphylococci (MRS), methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) have become a challenging problem in nosocomial infections and are connected with high morbidity and mortality rates. This is due to the increasing incidence of resistance to virtually all β-lactams and a wide variety of antimicrobials. The spread of MRS severely limits therapeutic options and generates the need for novel antibiotics that are able to combat MRS infections. One method of inhibiting bacterial growth is by blocking the expression of conserved bacterial genes and provides potential new avenues for generating a new generation of antimicrobials. The mecA gene is highly conserved among Staphylococcal species, and this makes it an ideal target for antisense inhibition. We had identified a target sequence (854-871 nt) within the mecA mRNA coding region that is particularly sensitive to antisense inhibition. The anti-mecA PS-ODN04 oligonucleotide was encapsulated into an anionic liposome. MRSA01 and MRSE01 clinical strains treated with this antisense sequence became susceptible to existing β-lactam antibiotics, and their growth was inhibited by oxacillin in vitro and in vivo. PS-ODN04 reduced the bacterial titers in the blood of mice infected with MRSA01 and MRSE01 and significantly improved their survival rate. Our data offer a possible new strategy for treating MRS infections.

Antibiotic susceptibility pattern and erythromycin resistance mechanisms in beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis isolates from central Taiwan

BACKGROUND/PURPOSE

Information concerning antibiotics susceptibilities of beta-hemolytic group G Streptococcus dysgalactiae subspecies equisimilis (SDSE) clinical isolates in central Taiwan was limited.

METHODS

Totally, 246 SDSE isolates were collected from mainly five regional hospitals, from February 2007 to August 2011. Disk diffusion method, broth microdilution method, and clindamycin induction test (D test) were respectively performed according to the guidelines of the Clinical and Laboratory Standards Institute. Polymerase chain reaction was used to detect the corresponding erythromycin resistance genes.

RESULTS

All isolates were susceptible to penicillin, cefotaxime, and vancomycin. The rate of erythromycin resistance was 24.0% (59/246), whereas that of clindamycin resistance was 12.2% (30/246). The resistance rates of isolates from different hospitals varied from 15.0% to 45.5% for erythromycin and from 7.1% to 36.4% for clindamycin. For erythromycin-resistant SDSE isolates, three different phenotypes with resistance to macrolides (M), lincosamides (L), and type B streptogramins (SB) were observed: M (49.2%), constitutive MLSB (cMLSB, 35.6%), and inducible MLSB (iMLSB, 15.3%). All M phenotypic isolates carried mefA. The most prevalent genotypes among cMLSB and iMLSB phenotypic isolates were ermB, followed by ermTR. One isolate with cMLSB phenotype carried both ermB and ermTR, whereas one isolate with iMLSB phenotype carried both ermB and ermC.

CONCLUSION

This is the first trial investigating the antimicrobial susceptibility pattern and erythromycin resistance mechanisms of beta-hemolytic group G SDSE isolates in central Taiwan. The resistance rates for both erythromycin and clindamycin varied significantly among hospitals located in this area and should be monitored continuously in the future.

Consensus statement on the management of methicillin-resistant Staphylococcus aureus nosocomial pneumonia in Asia

Nosocomial pneumonia (NP; encompassing hospital-acquired, health care-associated and ventilator-associated pneumonia) is one of the most common nosocomial infections and is associated with a mortality rate of 18.7%-40.8% in Asian countries. The burden of methicillin-resistant Staphylococcus aureus (MRSA) infections in Asia is high, and approximately 13% of NP cases in Asia are caused by this pathogen. Evidence regarding optimal management of MRSA NP continues to evolve and is complicated by the fact that a significant proportion of cases are likely to be caused by isolates with reduced susceptibility to the main therapeutic agent, vancomycin. The Asian Consensus Taskforce on MRSA Nosocomial Pneumonia has developed this statement to provide consensus points on diagnosis, antimicrobial treatment and prevention strategies for MRSA NP in the Asian context, based on our review of Asian data, previous international guidelines and recent scientific evidence.

Multidrug-resistant gram-negative bloodstream infections among residents of long-term care facilities

OBJECTIVE

Prevalence of multidrug-resistant (MDR) gram-negative (GN) bacteria is increasing globally and is complicated by patient movement between acute and long-term care facilities (LTCFs). In Asia, the contribution of LTCFs as a source of MDR GN infections is poorly described. We aimed to define the association between residence in LTCFs and MDR GN bloodstream infections (BSIs).

DESIGN

Secondary analysis of data from an observational cohort.

SETTING

Two tertiary referral hospitals in Singapore, including the 1,400-bed Tan Tock Seng Hospital and the 1,600-bed Singapore General Hospital.

PARTICIPANTS

Adult patients with healthcare-onset (HCO) or hospital-onset (HO) GN BSI.

METHODS

Patients were identified from hospital databases using standard definitions. Risk factors for both MDR GN HCO and HO BSI were analyzed using a multivariable logistic regression model.

RESULTS

A total of 675 episodes of GN BSI occurred over a 31-month period. Residence in a LTCF was an independent risk factor for developing MDR GN BSI (odds ratio [OR], 5.1 [95% confidence interval (CI), 2.2-11.9]; P < .01) when antibiotics were not used within the preceding 30 days. This risk persisted beyond the first 48 hours of hospitalization (OR, 3.4 [95% CI, 1.3-9.0]; P = .01). Previous culture growing an MDR organism (OR, 1.8 [95% CI, 1.3-2.7]; P < .01), previous antibiotic use (OR, 1.8 [95% CI, 1.2-2.6]; P < .01), and intensive care unit stay (OR, 2.2 [95% CI, 1.2-3.9]; P = .01), increased the risk of MDR GN BSI.

CONCLUSIONS

Residence in a LTCF is an independent risk factor for MDR GN BSI. Attempts to contain MDR GN bacteria in large Asian cities, where the proportion of the population that is elderly is projected to increase, should include infection prevention strategies that engage LTCFs.

The sensor kinase BfmS mediates virulence in Acinetobacter baumannii

BACKGROUND/PURPOSE

BfmR, the response regulator component of the two-component system BfmRS, has important roles in biofilm formation and cellular morphology of Acinetobacter baumannii. Until now, the contribution of the sensor kinase BfmS to the virulence of this bacterium remains unknown. In this study, a bfmS knockout and complementation studies were performed to clarify the role of BfmS in A. baumannii virulence.

METHODS

We constructed a bfmS knockout mutant in the A. baumannii 17978 type strain by transposon inactivation. To clarify the role of bfmS in A. baumannii virulence, the biofilm formation, adherence ability to eukaryotic cells, serum resistance, and antibiotic susceptibility tests were performed in A. baumannii 17978 and its derivative knockout and complementation strains.

RESULTS

The bfmS knockout displayed a reduction in biofilm formation, loss of adherence to eukaryotic cells, and greater sensitivity to serum killing compared with the parent strain. Proteomic analysis of culture supernatants revealed that the release of outer membrane proteins (Omps), including CarO and outer membrane protein A (OmpA), was associated with the inactivation of BfmS in A. baumannii.

CONCLUSION

This study is the first to demonstrate that the pathway regulated by the sensor kinase BfmS is associated with biofilm formation, adherence to biotic surfaces, serum resistance, and antibiotic susceptibility, which may be associated with the release of Omps in A. baumannii.

Genetic analysis of glycopeptide-resistant Staphylococcus epidermidis strains from bone and joint infections

Glycopeptide-resistant Staphylococcus epidermidis (GRSE) strains are of increasing concern in bone and joint infections (BJIs). Using multilocus sequence typing and multilocus variable-number tandem repeat analysis, we show that BJI-associated GRSE strains are genetically diverse but arise from related, multiresistant hospital sequence types (STs), mostly ST2, ST5, and ST23.

Trends in susceptibility of vancomycin-resistant Enterococcus faecium to tigecycline, daptomycin, and linezolid and molecular epidemiology of the isolates: results from the Tigecycline In Vitro Surveillance in Taiwan (TIST) study, 2006 to 2010

Among the 219 vancomycin-resistant Enterococcus faecium isolates collected in 20 Taiwanese hospitals from 2006 to 2010, all were susceptible to linezolid and daptomycin, and 98.6% were susceptible to tigecycline. There was a shift toward higher tigecycline MIC values (MIC(90)s) from 2006-2007 (0.06 μg/ml) to 2008-2010 (0.12 μg/ml). The MIC(90)s of daptomycin and linezolid remained stationary. Although pulsotypes among the isolates from the 20 hospitals varied, intrahospital spreading of several clones was identified in 13 hospitals.