• Tuberculosis and Respiratory Diseases
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• v.86 no.1
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• pp.47-56
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• 2023

Background: There is a global increase in isolation of nontuberculous mycobacteria (NTM). The aim of the study was to analyze longitudinal trends of NTM identification and pattern of antimicrobial susceptibility testing. Methods: NTM recovery rates, distribution of NTM species identification, and antimicrobial susceptibility pattern of NTM at Pusan National University Yangsan Hospital between January 2016 and December 2020 were retrospectively analyzed. Results: A total of 52,456 specimens from 21,264 patients were submitted for mycobacterial culture, of which 2,521 from 1,410 patients were NTM positive over five years (January 2016 to December 2020). NTM isolation showed an increasing trend from 2016 to 2020 (p<0.001, test for trend) mainly caused by Mycobacterium avium complex. The vast majority of M. avium complex were susceptible to key agents clarithromycin and amikacin. For Mycobacterium kansasii, resistance to rifampin and clarithromycin is rare. Amikacin was the most effective drug against Mycobacterium abscessus subspecies abscessus and Mycobacterium subspecies massiliense. Most of M. subspecies massiliense were susceptible to clarithromycin, while the majority of M. abscessus subspecies abscessus were resistant to clarithromycin (p<0.001). Conclusion: There was an increasing trend of NTM isolation in our hospital. Resistance to key drugs was uncommon for most NTM species except for M. abscessus subspecies abscessus against clarithromycin.

• Infection and chemotherapy
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• v.50 no.4
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• pp.328-339
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• 2018

Background: Pneumococcal disease is a major cause of morbidity and mortality worldwide, especially in patients with comorbidities and advanced age. This study evaluated trends in epidemiology of adult pneumococcal disease in Crete, Greece, by identifying serotype distribution and antimicrobial resistance of consecutive Streptococcus pneumoniae strains isolated from adults during an 8-year time period (2009-2016) and the indirect effect of the infant pneumococcal higher-valent conjugate vaccines 10-valent pneumococcal conjugate vaccine (PCV10) and 13-valent pneumococcal conjugate vaccine (PCV13). Materials and Methods: Antimicrobial susceptibility was performed by E-test and serotyping by Quellung reaction. Multidrug resistance (MDR) was defined as non-susceptibility to penicillin (PNSP) combined with resistance to ${\geq}2$ non-${\beta}$-lactam antimicrobials. Results: A total of 135 S. pneumoniae strains were isolated from adults during the study period. Twenty-one serotypes were identified with 17F, 15A, 3, 19A, and 11A, being the most common. The coverage rates of PCV10, and PCV13 were 17.8% and 37.8%, respectively. PCV13 serotypes decreased significantly from 68.4% in 2009 to 8.3% in 2016 (P = 0.002). The most important emerging non-PCV13 serotypes were 17F, 15A, and 11A, with 15A being strongly associated with antimicrobial resistance and MDR. Among all study isolates, penicillin-resistant and MDR strains represented 7.4% and 14.1%, respectively. Predominant PNSP serotypes were 19A (21.7%), 11A (17.4%), and 15A (17.4%). Erythromycin, clindamycin, tetracycline, trimethoprim-sulfamethoxazole, and levofloxacin resistant rates were 30.4%, 15.6%, 16.3%, 16.3%, and 1.5%, respectively. Conclusion: Although pneumococcal disease continues to be a health burden in adults in Crete, our study reveals a herd protection effect of the infant pneumococcal higher-valent conjugate vaccination. Surveillance of changes in serotype distribution and antimicrobial resistance among pneumococcal isolates are necessary to guide optimal prevention and treatment strategies.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.2
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• pp.155-163
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• 2019

During the time period from 2010 to 2017, out of 162,551 blood specimens, 11,233 (6.9%) specimens were positive for culture and 11,865 strains were cultured. Among the isolates, 47.8% were Gram positive cocci, 38.8% were Gram negative rods, 4.2% were Gram positive bacilli, 6.8% were fungi and 2.3% were anaerobes. When the culture results were compared according to gender, 55.0% (2,732/4,969) of the isolates were found in males and 45.0% (2,237/4,969) were isolated in females. In addition, when categorized according to age group, people in their 70s were the most separated by 28.7% (1,426/4,969) and this showed a great difference from 1.2% (62/4,969) of people in their teens. MRSA decreased significantly from 66.7% in 2016 to 46.8% in 2017. The vancomycin resistance rate of E. faecium was 35.0% (48/137). The ESBL positive rate of E. coli in intestinal bacteria was increased from 17.2% in 2010 to 28.8% in 2017, but the positive rate decreased for K. pneumoniae. 11.8% (14/119) of multidrug-resistant P. aeruginosa (MDRPA) of P. aeruginosa and 64.3% (161/252) of MDRAB of A. baumannii showed high resistance. Because the microbial susceptibility and antimicrobial susceptibility patterns of the blood specimens isolated from all the blood specimens differ according to the time period, region and patients, periodic analyses of different pathogens and understanding the changes in the degree of susceptibility to antimicrobial susceptibility have been conducted in hospitals.

• Biomedical Science Letters
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• v.5 no.2
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• pp.213-217
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• 1999

In order to control resistant strains and to properly select the antimicrobial agents, it is of quite importance to know current trends of bacterial species and changing patterns of antimicrobial resistance rates. The authors studied the results of 542 Gram-positive strains among 1,689 strains isolated at Chung-buk National University Hospital in 1996. The frequently isolated Gram-positive microorganisms were Staphylococcus aureus, Streptococcus pneumoniae, Staphylococcus epidermidis and Enterococcus faecalis in descending order. S. aureus showed high resistance to penicillin, gentamicin, and susceptibility to teicoplanin and vancomycin. Coagulase negative Staphylococcus was highly resistant to all of the antibiotics used in this experiment except teicoplanin and vancomycin. Enterococcus were highly resistant to vancomycin, penicillin and tetracycline. MIC of Gram-positive oaganisms was appeared to be zig-zag pattern.

• Pediatric Infection and Vaccine
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• v.10 no.2
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• pp.167-177
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• 2003

Purpose : To know the trends of antimicrobial susceptibility is critical for antimicrobial treatment. We studied the organisms isolated from blood, urine, stool, and cerebrospinal fluid from 1997 to 2001 to reveal the trends of their antimicrobial susceptibility. Methods : We conducted a retrospective study with isolates obtained from 0~18 year old outpatients and inpatients from 1997 to 2001 at Department of Pediatrics, Hanil general hospital. We gathered the data through the laboratory test files and the origin of microorganisms cultured from blood, urine, stool and cerebrospinal fluid and their antimicrobial susceptibility. Results : Microorganisms were isolated from 226(3.3%) out of 6,974 blood cultures, 365 (8.0%) out of 4,549 urine cultures, 50(1.9%) out of 2,593 stool cultures and 9(1.4%) in 655 cerebrospinal fluid cultures. The most frequently isolated organisms from blood cultures was Staphylococcus epidermidis(33.5%) which was followed by Staphylococcus aureus(19.7%), Escherichia coli(13.8%), and Burkholderia cepacia(9.0%). Among the urine cultures, E. coli was the most common(74.7%) which was followed by Group D Enterococcus(11.3%), Klebsiella pneumoniae(7.1%) and Proteus mirabilis(2.5%). The positive stool cultures all yield Salmonella species. Group D Salmonella was obtained most frequently. Among the positive cerebrospinal fluid cultures, Group B Streptococcus was isolated most frequently. Among the 40 cases of S. aureus in blood cultures, 27 cases were methicillin-resistant. The rates of susceptibility for amikacin, ceftizoxime and ceftriaxone of E. coli isolated from blood cultures were 80%, 100% and 60% in 1997 and 60%, 80% and 60% in 2001. The rates of susceptibility for amikacin, ceftizoxime and ceftriaxone of K. pnumoniae isolated from urine cultures. were 80%, 100% and 80% in 1997 and 50%, 83% and 50% in 2001 Enterococcus was isolated from 6.7% to 15.8% and vancomycin-resistant Enterococcus was observed in 17% of Group D Enterococcus isolated from urine cultures. The rates of susceptibility for amikacin, ceftizoxime and ceftriaxone of Group D Salmonella were 96%, 96% and 92% during the study period. Conclusion : Among the blood cultures S. epidermidis, S. aureus, E. coli and B. cepacia were isolated in order of frequency and among the urine cultures E. coli, Group D Enterococcus, K. pneumoniae and P. mirabilis were isolated in order of frequency. During the study period there was no big difference in major organisms isolated from blood and urine. The methicillin-resistant S. aureus was observed in 67% of S. aureus isolated from blood cultures but vancomycin-reistant S. aureus or vancomycin intermediate resistant S. aureus was not observed. The rates of susceptibility to amikacin and the third generation cephalosporin of E. coli isolated from blood cultures and K. pneumoniae from urine cultures have decreased. The isolation rates of Group D Enterococcus and vancomycin resistant Enterococcus have increased.

• Biomedical Science Letters
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• v.21 no.2
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• pp.84-91
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• 2015

To provide guidelines for the empirical treatment of urinary tract infections, we observed annual changes in the occurrence frequency and antimicrobial susceptibility of urinary isolates in a university hospital in the Chungbuk province, South Korea, over a period of 10 years (2004~2013). Escherichia coli (38.2%), Enterococcus faecalis (11.7%), Klebsiella pneumoniae (7.3%), Pseudomonas aeruginosa (4.3%), E. faecium (4.3%), and Staphylococcus aureus (4.1%) were commonly isolated urinary pathogens. The prevalence of E. coli, E. faecium and Streptococcus agalactiae were significantly higher in females (P < 0.001), whereas E. faecalis, P. aeruginosa and S. aureus were significantly more common in male patients (P < 0.001). E. coli mostly frequently showed resistance to ampicillin (67.94%), followed by trimethoprim/sulfamethoxazole (36.06%) and ciprofloxacin (26.84%). Over the studied time period, resistance rates of E. coli to ciprofloxacin significantly increased (20.44% to 33.55%). Moreover, extended-spectrum $\beta$-lactamase (ESBL) producing isolates also significantly increased in E. coli (4.2% to 18.3%) and K. pneumoniae (9.6% to 26.9%). In addition, the proportion of vancomycin-resistant Enterococcus facium (VRE) also increased (15.7% to 25.0%). In conclusion, over the last 10 years, the proportions of ciprofloxacin resistant E. coli and multidrug-resistant bacteria, such as ESBL and VRE have significantly increased. This trend must be strictly controlled and demonstrates the need for more updated guidelines for the treatment of urinary tract infections.

• Journal of Veterinary Clinics
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• v.21 no.1
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• pp.7-14
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• 2004

Bacteria that are resistant to several different groups of antibiotics have increased during the past few years. The importance of surveillance of antimicrobial resistance is now widely recognized. Unfortunately, this development has not been documented continuously in veterinary medicine in Korea. Therefore, the clinical prevalence and trend of antimicrobial susceptibility of aerobic isolates were investigated in this study. Total 121 isolates of aerobic bacteria were isolated from clinical specimens of dogs and cats at Veterinary Medical Teaching Hospital of Seoul National University from May 2001 to October 2002. Among them, the most common isolated species was Staphylococcus spp. (48 isolates), followed by E.coli (26 isolates), Enterococcus spp. (21 isolates), Klebsiella pneumoniae (9 isolates), Streptococcus spp. (6 isolates), Enterobacter cloacae (3 isolates), Pseudomonas aeruginosa (3 isolates), Corynebacterium xerosis (2 isolates), Chryseomonas spp. (2 isolates), and Providencia stuartii (1 isolate). The susceptibility of isolates to antibiotics was determined by the disk diffusion method. Gram-positive bacterial isolates were showed high susceptibilities to amikacin, amoxacillin/clavulanate, ceftazidime, and oxacillin, while Gram-negative bacterial isolates were showed high susceptibilities to amikacin and ceftazidime. Staphylococcus spp. were showed high susceptibilities to amikacin, amoxicillin/clavulanate, ceftazidime, cephalothin, and oxacillin. Streptococcus spp. and E.coli were showed high susceptibilities to amikacin and ceftazidime. Of the 48 staphylococci, seven Methicillin Resistant staphylococci were observed (14.6%), distributed among S. auricularis (1), S. hemolyticus (2), S. sciuri (1), S. saprophyticus (1), S. warneri (2) isolates. One strain of E.coli and one strain of Corynebacterium xerosis were resistant to all antibiotics tested. And, resistance trends between the you 2000 (from July 1999 to September 2000) and 2002 (from May 2001 to October 2002) were compared. Resistance to antibiotics was increased in both Gram-positive and Gram-negative bacterial isolates (p＜ 0.05). The resistance rates of Staphylococcus spp., E.coli and Klebsiella pneumoniae to all antibiotics tested were also increased (p＜0.05). This study investigated increasing resistance between the year 2000 and 2002 in Veterinary Medical Teaching Hospital of Seoul National University. Surveillance resistance is helpful to alert to veterinarian and select of appropriate therapy. Antimicrobial susceptibility surveillance of isolates should urgently be continued in veterinary medicine.

• Biomedical Science Letters
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• v.20 no.2
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• pp.77-84
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• 2014

Periodic analysis of local epidemiologic data of prevalent pathogens of blood culture can provide clinicians with relevant information to guide empirical antibiotic therapy. In this study, we analyzed a pattern of change of causative microorganisms and antimicrobial resistance at a tertiary medical center in Chungcheong province from 2003 to 2012, retrospectively. Of 70,258 blood specimens cultured, 6,063 (8.6%) were positive. Among the positive isolates, 95.9% were aerobic or facultative anaerobic bacteria, 0.1% were anaerobes, and 3.9% were fungi. Coagulase-negative Staphylococci (CoNS) (32.9%), Escherichia coli (16.7%), Staphylococcus aureus (9.1%), Klebsiella pneumoniae (6.4%), and ${\alpha}$-hemolytic Streptococcus (5.9%) were commonly isolated bacteria, and Candida albicans (1.4%) was the most commonly isolated fungi. Enterococcus faecium progressively increased but Streptococcus pneumoniae, Acinetobacter baumannii and Proteus species gradually decreased over a period of 10 years. The multidrug-resistant microorganisms such as methicillin-resistant S. aureus (MRSA), vancomycin-resistant enterococci (VRE), cefotaxime-resistant E. coli, imipenem-resistant Pseudomonas aeruginosa (IRPA) and imipenem-resistant A. baumannii (IRAB), were significantly increased. Therefore, there is a need for a more strict control of antibiotics and a more updated guideline for the treatment of bloodstream infection.

• Pediatric Infection and Vaccine
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• v.24 no.2
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• pp.71-78
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• 2017

Purpose: The aim of this study was to identify the pathogens of blood stream infection (BSI) in children with hemato-oncologic disorders, to analyze susceptibility patterns of microorganisms to guide empirical antimicrobial therapy, and to compare temporal trends of the pathogen and antimicrobial susceptibility with those of previous studies. Methods: We retrospectively analyzed the medical records of children with hemato-oncologic disorders whose blood culture grew pathogens at the Seoul National University Children's Hospital between 2011 and 2015. Results: A total of 167 patients developed 221 episodes of bacteremia. Among 229 pathogens, gram-negative bacteria (GNB) accounted for 69.0% (64.0% in 2002 to 2005, 63.4% in 2006 to 2010); gram-positive bacteria (GPB) accounted for 28.8% (31.3% in 2002 to 2005, 34.6% in 2006 to 2010); and fungus accounted for 2.2%. Among GNB, Klebsiella species (53.2%, 84/158) and Escherichia coli (19.6%, 31/158) were common. Staphylococcus aureus (48.5%, 32/66) and viridans streptococci (21.2%, 14/66) were frequently isolated among GPB. The susceptibilities of oxacillin and vancomycin in GPB were 54.8% and 96.9% (51.5% and 95.5% in 2002 to 2005; 34.1% and 90.5% in 2006 to 2010), respectively, whereas in GNB, the susceptibilities of cefotaxime, piperacillin/tazobactam, and imipenem were 73.2%, 77.2%, and 92.6% (75.9%, 82.8%, and 93.4% in 2002 to 2005; 62.8%, 82.9%, 93.8% and in 2006 to 2010), respectively. There were no significant differences in the proportion of etiologic agents or the antimicrobial susceptibilities between the current study and that of the previous two studies from 2002 to 2010. Overall fatality rate was 13.1%. Conclusions: GNB predominated in BSI among children with hemato-oncologic disorders. The etiology of bacteremia and antimicrobial susceptibility were comparable to those of the previous studies. Thus, piperacillin/tazobactam can be used as the initial empirical antimicrobial agent in febrile neutropenia.

• Pediatric Infection and Vaccine
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• v.31 no.1
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• pp.46-54
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• 2024

Purpose: This study aimed to identify the pathogens of bloodstream infection in children with underlying hemato-oncologic diseases, analyze susceptibility patterns, compare temporal trends with those of previous studies, and assess empirical antimicrobial therapy. Methods: Retrospective review study of children bacteremia in hemato-oncologic diseases was conducted at Seoul National University Bundang Hospital from January 2013 to July 2023. Results: Overall, 98 episodes of bacteremia were observed in 74 patients. Among pathogens isolated, 57.1% (n=56) were Gram-positive bacteria, 38.8% (n=38) were Gram-negative bacteria, and 4.1% (n=4) were Candida spp. The most common Gram-positive bacteria were coagulase-negative staphylococci (n=21, 21.4%) and Staphylococcus aureus, (n=14, 14.3%) whereas the most common Gram-negative bacteria were Klebsiella pneumoniae (n=16, 16.3%) and Escherichia coli (n=10, 10.2%). The susceptibility of Gram-positive bacteria to penicillin, oxacillin, and vancomycin was 11.5%, 32.7%, and 94.2%, respectively and the susceptibility of Gram-negative bacteria to cefotaxime, piperacillin/tazobactam, imipenem, gentamicin, and amikacin was 68.6%, 80%, 97.1%, 82.9%, and 91.4%, respectively. Methicillin-resistant S. aureus was detected in 1 strain and among Gram-negative strains, extended spectrum β-lactamase accounted for 28.9% (12/38). When analyzing the antibiotic susceptibility and empirical antibiotics, the mismatch rate was 25.5% (n=25). The mortality rate of children within 30 days of bacteremia was 7.1% (n=7). Conclusions: Empirical antibiotic therapy for bacteremia in children with hemato-oncologic diseases should be based on the local antibiogram in each institution and continuous monitoring is necessary.