First identification of methicillin-resistant Staphylococcus aureus MLST types ST5 and ST45 and SCCmec types IV and Vt by multiplex PCR during an outbreak in a respiratory care ward in central Taiwan

High hemolytic activity of the Staphylococcus aureus spa t1081 among clonal complex 45 in Taiwan

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST) 45 was first reported in Taiwan in 2006. Since then, the prevalence of ST45 MRSA in clinical isolates has increased. This study was carried out to understand the changes in the proportions, evolutionary relationships, and infection advantages of ST45 and its related clones.

MATERIALS AND METHODS

S. aureus including MRSA and MSSA (methicillin-sensitive S. aureus), and clonal complex (CC) 45 blood isolates were collected in 2000, 2005, and from January 2010 to August 2014. Molecular typing, multiple-locus variable-number tandem repeat analysis (MLVA) and single nucleotide polymorphism (SNP)-based phylogenetic analysis were performed. Fitness and virulence analyses were used to understand the infection advantages of the isolates.

RESULTS

Among the 67 CC45 isolates, only MSSA ST508 isolates were found in 2000 and 2005. Since 2010, the prevalence of MRSA has increased, t1081/ST45 has become dominant, and MRSA ST508 has been found. Phylogenetic analysis indicated that most of the ST45 isolates were located in a cluster distinct from those of ST508 and ST929. However, the t026 isolates clustered with the ST508 isolates rather than with the other ST45 isolates. Moreover, fitness and virulence analyses revealed that the t1081 isolates had higher hemolytic activity than the t026 and ST508 isolates did.

CONCLUSION

Our findings indicated that the increased prevalence of ST45 MRSA isolates from blood cultures in Taiwan was due to the t1081 isolates, and their high hemolytic activity may provide an infection advantage.

A Comparative Phenotypic and Genomic Analysis of Methicillin-Resistant Staphylococcus aureus ST45 Isolates From Cellulitis and Osteomyelitis in Taiwan

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST) 45 is a globally disseminated MRSA lineage. Herein, we investigated whether MRSA ST45 isolates from cellulitis and from osteomyelitis display distinctive phenotypic and genomic characteristics.

METHODS

A total of 15 MRSA ST45 isolates from cellulitis (CL-MRSA; n = 6) or osteomyelitis (OM-MRSA; n = 9) were collected in a Taiwan hospital. These MRSA ST45 isolates were characterized for their antimicrobial susceptibility, biofilm-forming ability, cellular infectivity in vitro, and pathogenicity in vivo. Four CL-MRSA and 6 OM-MRSA ST45 isolates were selected for whole-genome sequencing (WGS).

RESULTS

Antibiotic resistance tests showed that all OM-MRSA ST45 strains, but not CL-MRSA ST45 strains, were resistant to ciprofloxacin, levofloxacin, gentamicin, and doxycycline. Compared to the CL-MRSA ST45 isolates, the OM-MRSA ST45 isolates had stronger biofilm-forming ability and cellular infectivity and caused more severe disease in mice. WGS analysis revealed that these OM-MRSA ST45 isolates carry multiple common mutations or polymorphisms in genes associated with antibiotic resistance and virulence. Moreover, the transposable elements IS256 and IS257R2 were found only in the OM-MRSA ST45 isolates.

CONCLUSIONS

The emergence and spread of the highly pathogenic and multidrug-resistant ST45 MRSAs identified from osteomyelitis may pose a serious threat on public health.

Sequence types 8, 59, and 45 methicillin resistant Staphylococcus aureus as the predominant strains causing skin and soft tissue infections in Taiwan's prisons and jails

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is the predominant cause of skin and soft tissue infections (SSTIs), which is a problem in prisons and jails. We conducted this study to understand MRSA molecular characteristics among inmates with SSTIs, and we chose MRSA isolates from a community hospital as a comparison.

METHODS

A total of 219 MRSA isolates from three custodial facilities and 134 isolates from a community hospital in Taiwan were collected in the 2017 calendar year. MRSA isolates were investigated molecularly by staphylococcal chromosome cassette mec (SCCmec) type, mupirocin, and chlorhexidine genotypical resistance, and multi-locus sequence typing (ST).

RESULTS

Of the 219 MRSA isolates from custodial facilities, SCCmec IV was the most prevalent type (65.3%), followed by type V_T (32.4%) and type V (1.8%). Regarding sequence types, ST59 (36.4%), 8 (35.3%), and 45 (17.9%) were the leading three predominant types out of 184 selected MRSA isolates, and ST45 MRSA was more prevalent in custodial facilities (p = 0.019). The antimicrobial resistance rates varied for different MRSA strains, with ST45 MRSA having the lowest rates of resistance to most antimicrobials. Overall, 91.5% of isolates carried mupA gene and 25.8% were positive for qacA/B gene, this was independent of the MRSA sequence types.

CONCLUSIONS

ST59, ST8, and ST45 MRSA are the leading three MRSA strains causing SSTIs in Taiwan, 2017, but the molecular distribution varied distinctly between the custodial facilities and hospital settings. The genotypical mupirocin resistance rate is quite high in this study. The frequency of chlorhexidine resistance gene is relatively low, especially in MRSA isolates from custodial facilities.

Anticoccidial and immunogenic effectivity of encapsulated organic acids and anticoccidial drugs in broilers infected with Eimeria spp

The study was conducted to consider the anticoccidial and immunogenic effectivities of encapsulated organic acids and anticoccidial drugs in broilers reared on a reused litter infected with Eimeria spp. for simulating in-field exposure to avian coccidiosis. 525 mixed-sex one-day-old broiler chicks (Ross 308) were used in a 2 × 3 factorial experiment as a completely randomized design with seven experimental groups and five replicates of 15 chicks. The seven experimental groups were included: negative (uninfected; T₁) and positive (infected; T₂) control groups fed a diet without additive, and other infected groups (T₃-T₇) fed diets supplemented with 0.05% maduramicin, 0.02% diclazuril, 0.1% EOAs, 0.05% maduramicin and 0.1% EOAs, 0.02% diclazuril and 0.1% EOAs. During the experimental period, the evaluated parameters were European production efficiency factor (EPEF; at 22 days of age (d)), oocyst output per gram feces (OPG; at different ages), oocyst reduction rate (ORR; at 22-d), survival rate (SR; at 22-d), caecal lesion score (CLS at 22-d), sporulation percentage (SP; by in vitro anticoccidial tests), bloody diarrhea (BD; by scoring the bloody feces each morning from 13 to 31-d), immunity (humoral test at 28 and 35-d and cell-mediated test at 22-d), goblet cells analysis of the jejunum (GC; at 22-d) and anti-coccidiosis index (ACI; at 22-d). EOAs and anticoccidials, especially their simultaneous feeding improved (P < 0.05) broiler's EPEF, SR, OPG, ORR, SP, CLS, immunity and BD (scored). ACI was improved (P < 0.05) by EOAs more than anticoccidials (marked vs. moderate). The highest ACI was significantly observed in EOAs + diclazuril group. EOAs as a safe alternative had more intensive anticoccidial and immunogenic properties and increased the anticoccidial drugs' effectiveness, especially diclazuril in Eimeria spp-infected broilers.

Nasal Methicillin-Resistant Staphylococcus aureus Colonization in Patients with Type 1 Diabetes in Taiwan

Nasal methicillin-resistant Staphylococcus aureus (MRSA) colonies are an essential reservoir of infection, especially for patients with diabetes. However, data on MRSA colonization in patients with type 1 diabetes are limited. We investigated the epidemiology of MRSA colonization in patients with type 1 diabetes. This prospective cross-sectional study was conducted in a medical center (Chang Gung Memorial Hospital) in Taiwan from 1 July to 31 December 2020. Nasal sampling and MRSA detection were performed. The molecular characteristics of MRSA isolates were tested, and factors associated with MRSA colonization were analyzed. We included 245 patients with type 1 diabetes; nasal MRSA colonization was identified in 13 (5.3%) patients. All isolates belonged to community-associated MRSA genetic strains; the most frequent strain was clonal complex 45 (53.8%), followed by ST59 (30.8%) (a local community strain). MRSA colonization was positively associated with age ≤ 10 years, body mass index < 18 kg/m², and diabetes duration < 10 years; moreover, it was negatively associated with serum low-density lipoprotein cholesterol ≥ 100 mg/dL. No independent factor was reported. The nasal MRSA colonization rate in type 1 diabetes is approximately 5% in Taiwan. Most of these colonizing strains are community strains, namely clonal complex 45 and ST59.

Detection, spread and phylogeny of meticillin-resistant Staphylococcus aureus sequence type 45 in Taiwan

Meticillin-resistant Staphylococcus aureus (MRSA) sequence type (ST) 45 was reported in the literature to have been first identified in 2006 in Taiwan. The present study was carried out to explore and trace the emergence, transmission and evolutional dynamics of MRSA ST45 in Taiwan. We identified MRSA ST45 isolates retrospectively from two collections of MRSA isolates, namely TSAR (Taiwan Surveillance of Antimicrobial Resistance) surveys and the CGMH (Chang Gung Memorial Hospital)-based laboratory collection. Representative ST45 isolates were selected for whole-genome sequencing (WGS) analysis. A total of 9554 MRSA isolates was included in this study. Among the 3766 MRSA isolates biennially collected from TSAR surveys between 1998 and 2014, ST45 accounted for 133 (3.53 %) MRSA isolates, was first identified in 2004, and the prevalence rate peaked in 2010 (up to 10.77 %). Among the 5788 MRSA isolates collected between 1995 and 2017 by the CGMH-based laboratory, 257 isolates (4.44 %) were characterized as ST45, with most identified from nursing homes since 2012. Of the 75 isolates randomly selected for WGS, two clades were identified. The major clade, clade II, comprised 63 isolates and was phylogenetically relatively close to those isolates identified from Singapore. All but one of the isolates in clade I, the minor clade, were identified from non-Taiwanese people, mostly from newly recruited foreign workers in 2017, and were phylogenetically relatively close to one isolate from the USA (CA-347). Conclusively, the emergence of MRSA ST45 strain in Taiwan can be traced back to 2004 and the strain is connected to South-East Asian countries. Since its emergence, transmission and spread of MRSA ST45 has occurred in Taiwan.

Methicillin-Resistant Coagulase-Negative Staphylococci Carriage is a Protective Factor of Methicillin-Resistant Staphylococcus Aureus Nasal Colonization in HIV-Infected Patients: A Cross-Sectional Study

Background

Methicillin-resistant coagulase-negative Staphylococci (MRCoNS) is regarded as the repository of mecA gene for methicillin-resistant Staphylococcus aureus (MRSA) and may develop methicillin-susceptible Staphylococcus aureus (MSSA) to MRSA. Therefore, we aimed to explore whether MRCoNS carriage is a risk factor of MRSA colonization. Phenotypic characteristics were performed to further assess the associations between MRSA and MRCoNS.

Methods

This cross-sectional study was conducted in Guangzhou, China. Participants completed a questionnaire and provided a nasal swab for further analysis. The risk factors of MRSA colonization were analyzed using nonconditional logistic regression models. The phenotypic characteristics between MRSA and MRCoNS were compared by Chi-square test.

Results

Among the 1001 HIV-infected patients, a total of 119 (11.89%) participants were positive for MRSA, and 34.45% (41/119) of all MRSA carriers were positive for MRCoNS. We found MRCoNS carriage was a protective factor of MRSA colonization (adjusted odds ratio = 0.59, 95% confidence interval: 0.38–0.91). A significant difference in the proportions of antibiotic resistance between MRSA and MRCoNS isolates was found except for penicillin, clindamycin, tetracycline, and teicoplanin. The main STs and CC types of MRSA isolates in this population were ST188 (15.1%) and CC59 (17.6%), respectively.

Conclusions

HIV-infected patients remain a highly vulnerable population for MRSA colonization. Though who carried MRCoNS is less likely to have MRSA colonization, similarity of some antibiotic resistance between MRSA and MRCoNS was found in this study. Regular surveillance on the colonization and antibiotic patterns of MRSA and MRCoNS is still necessary.

Isolation of a Novel Lytic Bacteriophage against a Nosocomial Methicillin-Resistant Staphylococcus aureus Belonging to ST45

Methicillin-resistant Staphylococcus aureus (MRSA) can cause a wide range of infections from mild to life-threatening conditions. Its enhanced antibiotic resistance often leads to therapeutic failures and therefore alternative eradication methods must be considered. Potential candidates to control MRSA infections are bacteriophages and their lytic enzymes, lysins. In this study, we isolated a bacteriophage against a nosocomial MRSA strain belonging to the ST45 epidemiologic group. The phage belonging to Caudovirales, Siphoviridae, showed a narrow host range and stable lytic activity without the emergence of resistant MRSA clones. Phylogenetic analysis showed that the newly isolated Staphylococcus phage R4 belongs to the Triavirus genus in Siphoviridae family. Genetic analysis of the 45 kb sequence of R4 revealed 69 ORFs. No remnants of mobile genetic elements and traces of truncated genes were observed. We have localized the lysin (N-acetylmuramoyl-L-alanine amidase) gene of the new phage that was amplified, cloned, expressed, and purified. Its activity was verified by zymogram analysis. Our findings could potentially be used to develop specific anti-MRSA bacteriophage- and phage lysin-based therapeutic strategies against major clonal lineages and serotypes.

Nasal Methicillin-Resistant Staphylococcus aureus Carriage Among Foreign Workers Recruited to Taiwan From Southeastern Asian Countries

Background

In 2012, we identified the dissemination of methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST)45 strain in 14 nursing homes in Taiwan and foreign nurse workers, a significant risk factor for MRSA carriage. We conducted this study to understand MRSA carriage and molecular characteristics among foreign workers recruited from Southeastern Asian countries.

Methods

A cross-sectional study involving a total of 1935 foreign workers—929 (arrival group) and 1006 (staying group)—from Vietnam (n = 843), Indonesia (n = 780), the Philippines (n = 239), and Thailand (n = 70) were conveniently recruited during upon-arrival and regular health examination in a regional hospital. A nasal swab was obtained from each participant for detection of MRSA.

Results

Overall, MRSA carriage rate was 2.72%, with 2.26% for arrival group and 3.18% for staying group, and 4.74% for Vietnamese, 1.28% for Indonesians, 1.26% for Filipino, and none for Thai workers. Pulsotype AK/ST45 (57%) and pulsotype AX/ST188 (14%) were the top 2 dominant clones for the arrival group, whereas pulsotype D/ST59 (41%) (an endemic community clone in Taiwan) and pulsotype AK/ST45 (19%) were predominant for the staying group. A significant decrease of pulsotype AK/ST45 from 57% to 19% (P = .007) and increase of pulsotype D/ST59 from 4.8% to 41% (P = .004) were found between the arrival and the staying groups.

Conclusions

Approximately 3% of foreign workers recruited from Southeastern Asian countries to Taiwan were colonized with MRSA, including the ST45 strain. However, the MRSA isolates from workers staying in Taiwan were mostly a locally endemic clone and genetically different from those identified from workers on arrival.

Prevalence and molecular characterizations of Staphylococcus aureus nasal colonization among patients in pediatric intensive care units in Taiwan

Background

Nasal colonization of Staphylococcus aureus is a risk factor for the pathogen transmission and the development of infections. Limited information is available on the prevalence and molecular characteristics of S. aureus colonization in pediatric intensive care unit (ICU) patients.

Methods

A cross-sectional, island-wide study was conducted in 2011. Nasal swabs were collected from pediatric ICU patients at six tertiary hospitals in Taiwan.

Results

Of 114 patients enrolled in total, nasal colonization of S. arueus was detected in 30 (26.3%) of them, among whom 20 (17.5%) with methicillin-resistant S. arueus (MRSA). The ST59/SCCmec IV and V clones were most common and accounted for 45% of MRSA isolates, followed by ST239/SCCmec III (25%) and ST45/SCCmec IV (20%) clones. Three ST59 MRSA isolates carried the Panton-Valentine Leukocidin genes.

Conclusions

The results indicated a high prevalence of S. arueus and MRSA nasal colonization among pediatric ICU patients in Taiwan. Identification of epidemic clones warrants the implement of infection control measures to reduce colonization and prevent the dissemination of MRSA in hospitals.

Prevalence and Characterization of Staphylococcus aureus Isolated From Pasteurized Milk in China

Staphylococcus aureus is one of the most important food-borne pathogens globally. It produces various toxins and invasive enzymes and can be found in numerous food products. Milk is an important source of staphylococcal food poisoning. After pasteurization, this microorganism or its enterotoxins might still remain in pasteurized milk. Therefore, this study was to investigate the contamination of S. aureus in 258 pasteurized milk from 39 cities of China. The prevalence and levels of S. aureus in these samples as well as antibiotic susceptibility profiles, virulence genes, biofilm formation, and biofilm related genes, spa typing and MLST were used to determine the characterization among the isolates. It was found 3.9% of samples were detected S. aureus in 8 of 39 cities in China. The contaminated level were not very excessive which showed the MPN values of the most positive samples (9/10) were less than 1 MPN/g. All pasteurized milk-related S. aureus isolates have ability to produce biofilm and harbored icaA, icaD, eno, clfA, clfB, fnbA, fnbB, fib genes, other biofilm related genes icaC were showed in 91.7% of isolates and cna gene were showed in 50%, except bap gene which were free in all isolates. The antibiotic susceptibility test showed that all isolates were resistant or intermediate-resistant to different concentrations of the antibiotics. Furthermore, 75.0% of the isolates were resistant to three or more antibiotic classes, which indicated multidrug resistance. The isolates had virulence potential, which showed 66.7% (8/12) of the isolates carried one or more virulence-associated genes. Molecular typing by MLST and spa typing enabled classification of these isolates into a total of 11 sequence types (STs) and spa types, which indicated high genetic diversity. Most of these types were related to various clinical S. aureus infections. Thus, the findings of this study reflect the potential risk of S. aureus infection in China. Our study also provides comprehensive analysis of the prevalence of S. aureus in pasteurized milk and helps ensure more accurate treatment of human infection with effective antibiotics.

Comparison of molecular epidemiology of bloodstream methicillin-resistant Staphylococcus aureus isolates between a new and an old hospital in central Taiwan

OBJECTIVE

To compare the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) isolates between an old, urban hospital and a new, rural hospital over the same time period.

METHODS

The molecular characteristics of 398 MRSA bloodstream isolates collected between 2007 and 2013 from two hospitals in Taiwan were analyzed retrospectively; 202 isolates were from the old hospital and 196 from the new hospital (opened in 2007).

RESULTS

The rate of resistance to multiple antibiotics was significantly higher in the old hospital (93%) than in the new hospital (81%) (p<0.001). Genetic community-associated MRSA carrying staphylococcal cassette chromosome (SCC) type IV or V accounted for 58% of all MRSA isolates in the new hospital, significantly higher than the rate in the old hospital (p=0.018). The rate of spa t037-SCCmec III MRSA was significantly lower in the new hospital than in the old hospital (p=0.02). A significant decreasing trend in spa t002-SCCmec II MRSA isolates was observed in the old hospital (p=0.006), while the proportion of spa t037-SCCmec III MRSA decreased significantly in the new hospital (41.7% to 26.1%, p=0.022).

CONCLUSIONS

The rate of multiple antibiotic resistance and the molecular characteristics of MRSA differed significantly between the old and new hospitals and changed over time.

Prevalence and Characterization of Staphylococcus aureus Isolated From Women and Children in Guangzhou, China

The prevalent Staphylococcus aureus clones and antibiotic susceptibility profiles are known to change dynamically and geographically; however, recent S. aureus strains causing infections in women and children in China have not been characterized. In this study, we analyzed the molecular epidemiology and antimicrobial resistance of S. aureus isolated from patients in four centers for women and children in Guangzhou, China. In total, 131 S. aureus isolates (100 from children and 31 from women) were analyzed by spa typing, multi-locus sequence typing, virulence gene and antimicrobial resistance profiling, staphylococcal chromosomal cassette mec typing, and mutation analyses of rpoB. A total of 58 spa types, 27 sequence types (STs), and 10 clonal complexes (CCs) were identified. While CC59 (ST59-IV, 48.8%; ST338-III, 35.7%) and CC45 (ST45-IV, 100%) were the major clones (84.4%) among MRSA isolates, CC5 (ST188, 24.3%; ST1, 21.6%) and CC398 (ST398, 70%) were the major ones (70.1%) among MSSA isolates. ST338-MRSA-III mostly found in pus but hardly in respiratory tract samples while ST45-MRSA-IV was on the opposite, even though they both found in blood and cerebrospinal fluid sample frequently. Staphylococcal enterotoxin genes seb-seq-sek were strongly associated with ST59 and ST338, while sec was associated with ST45, ST121, ST22, and ST30. All ST338, ST1232, and SCCmec III isolates carried lukF/S-PV genes. A total of 80% of ST338 isolates were resistant to erythromycin, clindamycin, and tetracycline. All ST45 isolates exhibited intermediate or complete resistance to rifampicin. In total, 481 HIS/ASN mutations in rpoB were found in rifampicin-resistant or intermediate-resistant isolates. ST338-III and ST45-IV emerged as two of three major clones in MRSA isolates from women and children in Guangzhou, China, though ST59-MRSA-IV remained the most prevalent MRSA clone. Clonal distribution of S. aureus varied, depending on the specimen source. Virulence genes and antibiograms were closely associated with the clonal lineage. These results clarified the molecular epidemiology of S. aureus from women and children in Guangzhou, China, and provide critical information for the control and treatment of S. aureus infections.

Methicillin-resistant Staphylococcus aureus nasal carriage in international medical conference attendees

BACKGROUND

Carriage of methicillin-resistant Staphylococcus aureus (MRSA) is associated with its transmission. International travels and massive gatherings may accelerate such transmission. MRSA carriage was surveyed among the attendees of two international medical conferences held in Taipei in 2010.

METHODS

A total of 209 attendees from 23 countries were recruited. Nasal specimens were collected from each volunteer and subjected to polymerase chain reaction (PCR) detection for MRSA. Molecular analysis, including pulsed-field gel electrophoresis, multilocus sequence typing (MLST), typing of staphylococcal cassette chromosome mec (SCCmec) and staphylococcal protein A (spa) genes, and detection of Panton-Valentine leukocidin (PVL) and sasX genes, was performed.

RESULTS

MRSA carriage was detected in 10 (4.8%) attendees from Vietnam (3/8, 37.5%), Korea (2/6, 33.3%), Japan (2/41, 4.9%), Philippines (2/52, 3.8%), and Bangladesh (1/4, 25.0%). The proportion of MRSA colonizers was significantly higher in the local hospital group compared to those from the other groups (3/17 vs. 7/192, p < 0.05). Six MRSA isolates were available for molecular analysis. They all carried a type IV SCCmec gene. Five pulsotypes were identified; four genotypes, respectively, were identified by MLST and spa typing. None of the isolates carried either PVL or sasX genes. None of common molecular characteristics was shared by isolates from different countries. Most of these isolates were local endemic community clone in each country.

CONCLUSIONS

As healthcare workers, a certain proportion of international medical conference attendees harbored MRSA in their nares, mostly local endemic community clones in each country, which has the potential of spread among attendees.

Characterization of rifampin-resistant Staphylococcus aureus nasal carriage in patients receiving rifampin-containing regimens for tuberculosis

Objectives

This study investigated molecular characteristics of rifampin (RIF)-resistant (RIF-R) Staphylococcus aureus isolates recovered from patients receiving RIF-containing regimens for tuberculosis (TB).

Patients and methods

Patients with TB who received RIF-containing regimens from November 2009 to May 2011 at a medical center were enrolled. Nasal swabs for S. aureus culture were obtained at the time of enrollment, and then every two months until two months after RIF treatment had been completed. Genetic relatedness of the isolates was determined using pulsed-field gel electrophoresis, multilocus sequence typing, and gene typing of spa and SCCmec. The presence of RIF resistance-associated mutations in rpoB, and fusidic acid resistance genes fusB and fusC in the S. aureus isolates were analyzed.

Results

Among the 200 patients enrolled in this study, 152 completed follow-ups during treatment, and 114 completed two months of follow-up after discontinuing use of RIF. At enrollment, ten patients (5%) had nasal colonization with S. aureus, namely eight with methicillin-susceptible S. aureus (MSSA), and two with methicillin-resistant S. aureus (MRSA, ST59-SCCmecIV-RIF-susceptible). All these patients were decolonized after RIF usage. Two patients with MSSA colonization at enrollment showed recolonization with genetically unrelated MSSA strains two months after completion of RIF treatment. There were five ST45-SCCmecV_T-RIF-R strains from two patients isolated during RIF exposure. Sequencing of rpoB in the RIF-R S. aureus isolates revealed different mutation sites between the MSSA and MRSA isolates.

Conclusion

RIF-R S. aureus strains are more likely to result in persistent nasal carriage in TB patients receiving RIF treatment. Monitoring of emergence and possible dissemination of the MRSA ST45 strains among TB patients treated with RIF in Taiwan is warranted.

Emergence of multidrug-resistant sequence type 45 strains among mecA-positive borderline oxacillin-resistant Staphylococcus aureus causing bacteraemia in a medical centre in Taiwan

Clinical data related to bacteraemia caused by mecA-positive borderline oxacillin-resistant Staphylococcus aureus (BORSA) isolates [minimum inhibitory concentrations (MICs) of 0.5-4 mg/L] are limited. Patients aged ≥15 years with bacteraemia due to BORSA who were admitted to the emergency department of a Taiwanese tertiary hospital between January 2001 and December 2015 were evaluated. Clinical characteristics of patients with bacteraemia caused by BORSA, methicillin-susceptible S. aureus and methicillin-resistant S. aureus (MRSA) were compared. MICs of 12 antibiotics were determined by agar dilution. Genetic characteristics of 64 available BORSA isolates were analysed by detection of the SCCmec gene, the mecA promoter region sequence and multilocus sequence typing (MLST). Pulsed-field gel electrophoresis (PFGE) was performed to identify the clonality of the emerging ST isolates. The quinolone resistance genes were analysed for the emerging ciprofloxacin-resistant ST45 clone isolates. Among the 65 BORSA bacteraemic patients, in-hospital mortality was 24.6%, significantly lower than that of MRSA patients (38.5%) (P = 0.03). Underlying conditions were similar between BORSA and MRSA patients, but with less dialysis in the former (P = 0.01). Multivariate analysis revealed that septic shock [odds ratio (OR) = 15.95] and bacteraemia originating from lower respiratory tract infection (OR = 5.78) were two independent risk factors for 30-day mortality. The ST45 clone with high-level ciprofloxacin resistance (MICs of 8-128 mg/L) replaced ST59 as the predominant clone since 2012, although no major clustering was detected. In conclusion, the emerging multidrug-resistant ST45 clone has replaced ST59 as the most common among BORSA isolates.

Predominance of methicillin-resistant Staphylococcus aureus in the residents and environments of long-term care facilities in Taiwan

BACKGROUND/PURPOSE

This study investigated the distribution and persistence of multidrug resistant organisms (MDROs) including methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPA), and multidrug-resistant Acinetobacter baumannii (MDRAB) in six long-term care facilities (LTCFs).

METHODS

We investigated the distribution of MDROs in residents of six LTCFs and their environments from January to December 2016 (intervention period). Active surveillance of colonization of MDROs was performed by culturing rectal and nasal swab samples from the residents every three months. Multilocus sequence typing (MLST) was conducted, and genes for panton-valentine leukocidin (PVL) from MRSA isolates were determined.

RESULTS

A total of 521 samples were positive for MDROs, and MRSA was the most common organism (65.1%), followed by MDRAB (11.3%), carbapenem-resistant Klebsiella pneumoniae (11.1%), carbapenem-resistant Escherichia coli (4.6%), and carbapenem-resistant P. aeruginosa (2.1%, n = 11). By a linear regression model, positive MRSA isolates from the environment were found to be statistically significant and associated with the number of colonized LTCF residents (p = 0.01), while the timing of the surveillance culture was not (p = 0.227). The main MLST types associated with PVL-production were sequence type (ST) 59, (40.0%, 24/60), ST30 (21.4%, 3/14), ST8 (87.5%, 14/16), and ST45 (3.6%, 1/28). The susceptibility rates of tetracycline (96.7%), trimethoprim-sulfamethoxazole (96.7%), and ciprofloxacin (81.7%) were statistically significant and higher in MRSA ST59, compared to the rates in MRSA ST45 isolates.

CONCLUSIONS

MRSA was the most commonly colonized MDRO, both in the LTCF residents and in the environment, followed by MDRAB and carbapenem-resistant K. pneumoniae.

Methicillin-Resistant Staphylococcus aureus Ocular Infection in Taiwan: Clinical Features, Genotying, and Antibiotic Susceptibility

Methicillin-resistant Staphylococcus aureus (MRSA) infection is an important public health issue. This observational study aimed to characterize clinical features, antibiotic susceptibility, and genotypes of ocular infections caused by MRSA based on the clinical and molecular definitions of community-associated (CA) and healthcare-associated (HA) strains.Fifty-nine patients with culture-proven S aureus ocular infection were enrolled from January 1, 2010 to December 31, 2011 at Chang Gung Memorial Hospital, Taiwan. Antibiotic susceptibility was verified using disk diffusion/E test. For characterization, staphylococcal cassette chromosome mec (SCCmec), pulsed-field gel electrophoresis (PFGE), multilocus sequence type (MLST), and Panton-Valentine leukocidin (PVL) gene, were performed. MRSA isolates from the patients with HA factors were classified as clinically defined HA-MRSA, and those carrying SCCmec type I to III as molecularly defined HA-MRSA.Thirty-four patients with MRSA ocular infection were identified. The most common clone of CA-MRSA and HA-MRSA isolates was ST59/PFGE type D/SCCmec IV,VT/PVL (+) (n = 12) and CC 239/PFGE type A/SCCmec III, IIIA/PVL(-) (n = 10), respectively. All the 11 patients with molecularly defined HA-MRSA infections and 50% of the 22 patients with molecularly defined CA-MRSA infections were found to have HA factors (P = .005). CA-MRSA tended to cause lid infections, whereas HA-MRSA tended to cause corneal infections. Contrary to HA-MRSA isolates, nearly all the CA-MRSA isolates were susceptible to trimethoprim/sulfamethoxazole and fluoroquinolones under either clinical or molecular classifications.In Taiwan, CA-MRSA isolates exhibited considerably higher susceptibility to fluoroquinolones when compared with HA-MRSA isolates. A strong correlation was observed between the HA factors and molecularly defined HA-MRSA isolates.

Dissemination of methicillin-resistant Staphylococcus aureus sequence type 45 among nursing home residents and staff in Taiwan

Unlike hospitals or the community, nursing homes provide a unique healthcare environment for patients. There have been no reports regarding methicillin-resistant Staphylococcus aureus (MRSA) carriage among nursing home residents and staff in Taiwan. From May to November 2012, a total of 523 subjects, including 360 residents and 163 staff, in 14 nursing homes in Taiwan were surveyed for nasal MRSA carriage. Overall, the nasal MRSA carriage rate was 20.1%, with 20.3% for residents and 19.6% for staff. For residents, age >60 years (adjusted OR 2.268; 95% CI 1.185-4.342; p 0.013) and the presence of chronic wounds (adjusted OR 2.449; 95% CI 1.082-5.544; p 0.032) were the significant risk factors for MRSA carriage in multivariate models. Among the 105 MRSA isolates, 11 pulsed-field gel electrophoresis (PFGE) patterns were identified, except for five isolates untypeable by SmaI digestion, with one major pattern; nine isolates (8.6%) possessed staphylococcal cassette chromosome (SCCmec) type II or III, 66 isolates type IV or V, and 21 isolates unidentified types. The clone characterized as PFGE pattern BM sequence type 45 was the most common clone, accounting for 50% of the isolates, and was multiresistant, including to ciprofloxacin. Intra-institutional and inter-institutional transmission of MRSA was documented by molecular methods. It was shown conclusively that one-fifth of residents and staff in nursing homes in Taiwan harboured MRSA, mostly ST45 strains, in their nares. Intra-institutional and inter-institutional transmission of MRSA was documented.

Effective application of multiple locus variable number of tandem repeats analysis to tracing Staphylococcus aureus in food-processing environment

A total of 256 isolates of Staphylococcus aureus were isolated from 98 samples (34 swabs and 64 food samples) obtained from small or medium meat- and cheese-processing plants in Slovakia. The strains were genotypically characterized by multiple locus variable number of tandem repeats analysis (MLVA), involving multiplex polymerase chain reaction (PCR) with subsequent separation of the amplified DNA fragments by an automated flow-through gel electrophoresis. With the panel of isolates, MLVA produced 31 profile types, which was a sufficient discrimination to facilitate the description of spatial and temporal aspects of contamination. Further data on MLVA discrimination were obtained by typing a subpanel of strains by multiple locus sequence typing (MLST). MLVA coupled to automated electrophoresis proved to be an effective, comparatively fast and inexpensive method for tracing S. aureus contamination of food-processing factories.

SIGNIFICANCE AND IMPACT OF THE STUDY

Subspecies genotyping of microbial contaminants in food-processing factories may facilitate identification of spatial and temporal aspects of the contamination. This may help to properly manage the process hygiene. With S. aureus, multiple locus variable number of tandem repeats analysis (MLVA) proved to be an effective method for the purpose, being sufficiently discriminative, yet comparatively fast and inexpensive. The application of automated flow-through gel electrophoresis to separation of DNA fragments produced by multiplex PCR helped to improve the accuracy and speed of the method.

Prevalence and genetic diversity of nontypeable haemophilus influenzae in the respiratory tract of infants and primary caregivers

BACKGROUND

Nontypeable Haemophilus influenzae (NTHi) causes otitis media, sinusitis, and likely lower respiratory tract infections in children. Colonization, strain diversity, transmission, and antimicrobial susceptibility have implications for both children and their caregivers.

METHODS

For 13 months, we conducted a cross-sectional study of NTHi colonization. Upper respiratory tract cultures were performed in 273 infants and children 2 to 26 months of age and their primary caregivers. NTHi isolates were characterized by multilocus sequence typing (MLST), and antibiotic resistance was examined.

RESULTS

Of the 273 infants, 44 (16.1%) were colonized with NTHi. Prevalence of NTHi varied from 14% in infants less than 6 months of age to 32% in infants between 19 and 26 months of age (P = 0.003). NTHi-colonized infants were more likely to attend day care (30% vs. 12%), have a recent respiratory infection (68% vs. 38%), have recently taken an antibiotic (27% vs. 9%), and have a primary caregiver who reported asthma (11% vs. 1%), compared with other infants (P < 0.01). In the 44 infants colonized with NTHi, we identified 33 different MLSTs. Of the 44 infant-primary caregiver dyads, 9 (20.5%) were colonized with NTHi, and 7 of these 9 shared identical NTHi strains. We also found beta-lactamase-negative NTHi with minimum inhibitory concentrations >2 μg/mL for amoxicillin and beta-lactamase-positive NTHi with minimum inhibitory concentrations >2 μg/mL for amoxicillin clavulanate.

CONCLUSIONS

We found substantial diversity by MLST analysis among NTHi isolates from this community. Infant-primary caregiver dyads usually carried the same strain of NTHi, suggesting that infant-primary caregiver transmission is occurring.