Streptococcus pneumonia evades vaccines and drugs by high levels of recombination and rapid adaptation.

Methicillin-resistant Staphylococcus aureus (MRSA) is highly prevalent in hospitals in many Asian countries. Recent emergence of community-associated (CA) MRSA worldwide has added another serious concern to the epidemiology of S. aureus infections. To understand the changing epidemiology of S. aureus infections in Asian countries, we performed a prospective, multinational surveillance study with molecular typing analysis. We evaluated the prevalence of methicillin resistance in S. aureus isolates in CA and healthcare-associated (HA) infections, and performed molecular characterization and antimicrobial susceptibility tests of MRSA isolates. MRSA accounted for 25.5% of CA S. aureus infections and 67.4% of HA infections. Predominant clones of CA-MRSA isolates were ST59-MRSA-SCCmec type IV-spa type t437, ST30-MRSA-SCCmec type IV-spa type t019 and ST72-MRSA-SCCmec type IV-spa type t324. Previously established nosocomial MRSA strains including sequence type (ST) 239 and ST5 clones were found among CA-MRSA isolates from patients without any risk factors for HA-MRSA infection. CA-MRSA clones such as ST59, ST30 and ST72 were also isolated from patients with HA infections. Our findings confirmed that MRSA infections in the community have been increasing in Asian countries. Data also suggest that various MRSA clones have spread between the community and hospitals as well as between countries.

Antimicrobial resistance in Streptococcus pneumoniae remains a serious concern worldwide, particularly in Asian countries, despite the introduction of heptavalent pneumococcal conjugate vaccine (PCV7). The Asian Network for Surveillance of Resistant Pathogens (ANSORP) performed a prospective surveillance study of 2,184 S. pneumoniae isolates collected from patients with pneumococcal infections from 60 hospitals in 11 Asian countries from 2008 to 2009. Among nonmeningeal isolates, the prevalence rate of penicillin-nonsusceptible pneumococci (MIC, ≥4 μg/ml) was 4.6% and penicillin resistance (MIC, ≥8 μg/ml) was extremely rare (0.7%). Resistance to erythromycin was very prevalent in the region (72.7%); the highest rates were in China (96.4%), Taiwan (84.9%), and Vietnam (80.7%). Multidrug resistance (MDR) was observed in 59.3% of isolates from Asian countries. Major serotypes were 19F (23.5%), 23F (10.0%), 19A (8.2%), 14 (7.3%), and 6B (7.3%). Overall, 52.5% of isolates showed PCV7 serotypes, ranging from 16.1% in Philippines to 75.1% in Vietnam. Serotypes 19A (8.2%), 3 (6.2%), and 6A (4.2%) were the most prominent non-PCV7 serotypes in the Asian region. Among isolates with serotype 19A, 86.0% and 79.8% showed erythromycin resistance and MDR, respectively. The most remarkable findings about the epidemiology of S. pneumoniae in Asian countries after the introduction of PCV7 were the high prevalence of macrolide resistance and MDR and distinctive increases in serotype 19A.

A total of 685 clinical Streptococcus pneumoniae isolates from patients with pneumococcal diseases were collected from 14 centers in 11 Asian countries from January 2000 to June 2001. The in vitro susceptibilities of the isolates to 14 antimicrobial agents were determined by the broth microdilution test. Among the isolates tested, 483 (52.4%) were not susceptible to penicillin, 23% were intermediate, and 29.4% were penicillin resistant (MICs ≥ 2 mg/liter). Isolates from Vietnam showed the highest prevalence of penicillin resistance (71.4%), followed by those from Korea (54.8%), Hong Kong (43.2%), and Taiwan (38.6%). The penicillin MICs at which 90% of isolates are inhibited (MIC ₉₀ s) were 4 mg/liter among isolates from Vietnam, Hong Kong, Korea, and Taiwan. The prevalence of erythromycin resistance was also very high in Vietnam (92.1%), Taiwan (86%), Korea (80.6%), Hong Kong (76.8%), and China (73.9%). The MIC ₉₀ s of erythromycin were >32 mg/liter among isolates from Korea, Vietnam, China, Taiwan, Singapore, Malaysia, and Hong Kong. Isolates from Hong Kong showed the highest rate of ciprofloxacin resistance (11.8%), followed by isolates from Sri Lanka (9.5%), the Philippines (9.1%), and Korea (6.5%). Multilocus sequence typing showed that the spread of the Taiwan ^19F clone and the Spain ^23F clone could be one of the major reasons for the rapid increases in antimicrobial resistance among S. pneumoniae isolates in Asia. Data from the multinational surveillance study clearly documented distinctive increases in the prevalence rates and the levels of antimicrobial resistance among S. pneumoniae isolates in many Asian countries, which are among the highest in the world published to date.

Rationale: Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) remain important causes of morbidity and mortality. Increasing antimicrobial resistance has aroused the concern of the failure of antibiotic treatment. Objectives: To determine the distribution of the bacterial isolates of HAP and VAP, their antimicrobial resistance patterns, and impact of discordant antibiotic therapy on clinical outcome in Asian countries Methods: A prospective surveillance study was conducted in 73 hospitals in 10 Asian countries from 2008–2009. A total of 2,554 cases with HAP or VAP in adults were enrolled and 2,445 bacterial isolates were collected from 1,897 cases. Clinical characteristics and antimicrobial resistance profiles were analyzed. Measurement and Main Results: Major bacterial isolates from HAP and VAP cases in Asian countries were Acinetobacter spp., Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae. Imipenem resistance rates of Acinetobacter and P. aeruginosa were 67.3% and 27.2%, respectively. Multidrug-resistant rates were 82% and 42.8%, and extensively drug-resistant rates were 51.1% and 4.9%. Multidrug-resistant rate of K. pneumoniae was 44.7%. Oxacillin resistance rate of S. aureus was 82.1%. All-cause mortality rate was 38.9%. Discordant initial empirical antimicrobial therapy increased the likelihood of pneumonia-related mortality (odds ratio, 1.542; 95% confidence interval, 1.127–2.110). Conclusions: Acinetobacter spp., P. aeruginosa, S. aureus, and K. pneumoniae are the most frequent isolates from adults with HAP or VAP in Asian countries. These isolates are highly resistant to major antimicrobial agents, which could limit the therapeutic options in the clinical practice. Discordant initial empirical antimicrobial therapy significantly increases the likelihood of pneumonia-related mortality.

A small number of clonal lineages dominates the global population structure of methicillin-resistant Staphylococcus aureus (MRSA), resulting in the concept that MRSA has emerged on a few occasions after penicillinase-stable β-lactam antibiotics were introduced to clinical practice, followed by intercontinental spread of individual clones. We investigated the evolutionary history of an MRSA clone (ST5) by mutation discovery at 108 loci (46 kb) within a global collection of 135 isolates. The SNPs that were ascertained define a radial phylogenetic structure within ST5 consisting of at least 5 chains of mutational steps that define geographically associated clades. These clades are not concordant with previously described groupings based on staphylococcal protein A gene ( spa ) typing. By mapping the number of independent imports of the staphylococcal cassette chromosome methicillin-resistance island, we also show that import has occurred on at least 23 occasions within this single sequence type and that the progeny of such recombinant strains usually are distributed locally rather than globally. These results provide strong evidence that geographical spread of MRSA over long distances and across cultural borders is a rare event compared with the frequency with which the staphylococcal cassette chromosome island has been imported.