• Korean Journal of Clinical Laboratory Science
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• v.38 no.3
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• pp.166-172
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• 2006

Metallo-${\beta}$-lactamase (MBL) can hydrolyze all ${\beta}$-lactams except monobactams and frequently coexists with various antibiotic resistance genes such as aminoglycoside resistance, sulfonamide resistance gene, etc. Therefore, the effective antibiotics against infections by these bacteria are markedly limited or can't even be found. We tried to search in-vitro antimicrobial combinations with synergistic effects for a VIM-2 type MBL producing Pseudomonas aeruginosa, isolated from clinical specimen. On the selection of antibiotic combinations with synergistic effects, we performed a one disk synergy test, modified Pestel's method, in agar without aztreonam (AZT). The bacteriostatic synergistic effects of this tests were scored as $S_1$ (by susceptibility pattern in agar without antibiotics), $S_2$ (by the change of susceptibility in agar with or without antibiotics) and $S_3$ ($S_1$ + $S_2$) and was classified into weak (1 point), moderate (2 points) and strong (3 points) by $S_3$ score. Subsequently, we carried out the time-killing curve for the antibiotic combinations with the strong synergistic bacteriostatic effect. One VIM-2 type MBL producing P. aeruginosa confirmed by the PCR showed all resistance against all ${\beta}$-lactams except AZT, aminoglycoside and ciprofloxacin. In the one disk synergy test, this isolate showed a strong bacteriostatic synergistic effect for the antibiotic combination of AZT and piperacillin-tazobactam (PIP-TZP) or AZT and amikacin (AN). On the time-killing curve after six hours of incubation, the colony forming units (CFUs/mL) of this bacteria in the medium broth with both combination antibiotics were decreased to 1/18.7, 1/17.1 of the least CFUs of each single antibiotics. The triple antibiotic combination therapy including AZT, PIP-TZP and AN was shown to be significantly synergistic after 8 hrs of exposure. In a VIM-2 MBL producing P. aeruginosa with susceptibility for AZT, the triple antibiotic combination therapy including AZT, PIP-TZP and AN may be considered as an alternative antibiotics modality against the infection by some MBL type. But the antimicrobial combination therapy for many more MBL producing isolates is essential to know as soon as possible for the selection of effective treatment against the infection by this bacteria.

• The Journal of the Korean Society for Microbiology
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• v.22 no.3
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• pp.283-294
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• 1987

One hundred and fifty-seven strains of staphylococci isolated from various clinical specimens and 80 of Gram-negative bacilli from urine of patients with urological diseases were tested for resistance to antimicrobial drugs by microdilution broth method. Among staphylococci, 50 to 89% of the strains were resistant to gentamicin(Gm), kanamycin(Km), erythromycin(Em), nalidixic acid(Na), and tetracycline. Ninety per cent MIC was lowest in ciprofloxacin(Cp), followed by vancomycin(Vc), trimethoprim(Tp), enoxacin(Ex), and norfloxacin(Nf) with the values of two ${\mu}g/ml$ or lower. Twenty-seven strains were resistant to methicillin(MR), with 24 strains of Staphylococcus aureus and 3 of S. epidermidis. All strains of MR S. aureus were resistant to oxacillin, rifampin(Rf), Gm, Km, Em, Na, and Tc, and no strain was resistant to Vc and Tp. Almost all staphylococci isolated from urine were S. epidermidis and sensitive to most drugs tested without MR strain. Among Gram-negative bacilli from urine, Escherichia coli(43 strains) was most frequently isolated, and followed by Klebsiella spp.(11), Proteus spp.(10), Serratia spp.(10), and Pseudomonas aeruginosa(6) in the decreasing order. The majority of E. coli and Serratia spp. were resistant to chloramphenicol(Cm), Tc, streptomycin, sulfisomidine(Su), ampicillin(Ap), Km, and carbenicillin(Cb), and 50 and 90% MICs of these drugs were also high. In Klebsiella spp., 54% or more were resistant to Cm, Su, Ap, cephalothin, and Cb. Proteus spp. were susceptible to most drugs tested, but Pseudomonas were resistant to nearly all drugs tested except Rf, amikacin, and moxalactam(Mx). All Gram-negative bacilli tested were found to be susceptible to Mx. New quinolone carboxylic acid compounds, such as Nf, Ex, and Cp showed very high antimicrobial activities against the majority of organisms tested except Pseudomonas, and 50 and 90% MICs of Nf and Ex were always equal or 2 to 4 times higher than Cp. Organisms multiply resistant to drugs were noted in almost all isolates tested. Twenty-seven strains of staphylococci were multiply resistant to 11 or more drugs, and 6 of Klebsiella spp. to 8 to 11 drugs. The most frequent multiplicity of durg resistance were 7 and 8, 12, and 13 in E. coli, Serratia spp., and Pseudomonas, respectively. No strain was resistant to more than 5 drugs in Proteus spp..

• Journal of Environmental Health Sciences
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• v.47 no.5
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• pp.479-485
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• 2021

Background: Vibrio vulnificus has been frequently detected in seawater, fish, and shellfish mainly in the coastal areas of Chungcheongnam-do Province. Objectives: This study was conducted to investigate the analyzed biochemical properties, genetic characteristics, and distribution of Vibrio vulnificus isolated from environmental sources in coastal areas of Chungcheongnam-do Province from 2019 to 2020. Methods: A total of 1,510 samples were obtained from six different sites in Chungcheongnam-do Province. Isolated strains from the samples were identified by a VITEK 2 system and MALDI-TOF. Antibiotic susceptibility testing for 85 isolates was done by microdilution minimum inhibitory concentration methods, and 11 isolates were analyzed for 16s rRNA sequences in multiple alignments. Results: Among the 1,510 samples taken during the investigation period, 306 strains were isolated and the detection rate of V. vulnificus was 20.3%. One hundred eighty-eight strains (24.6%) from seawater and 118 strains (15.8%) from mud flats were isolated. It was mainly detected in July (17.3%), August (36.5%), and September (28.8%), and the proportion was 82.0%. Based on the CLSI-recommended breakpoints, V. vulnificus isolates were all susceptible to amoxicillin/clavulanic acid, amikacin, gentamicin, ciprofloxacin and trimethoprim/sulfamethoxazole. However, nonsusceptible isolates to ampicillin, ampicillin/sulbactam, cefazolin, cefoxitin, imipenem, tetracycline and chloramphenicol were identified. In the analysis of the nucleotide sequences for 16s rRNA of V. vulnificus isolates, it was confirmed that mutations frequently occurred between nucleotide number 922 and 952, and 98.2% to 100% nucleotide identities between isolates was verified. Conclusions: The results of this study can be used as a basic data for infection control and prevention of Vibrio vulnificus infection by describing the distribution and characteristics of Vibrio vulnificus strains isolated in coastal areas of Chungcheongnam-do Province.

• Microbiology and Biotechnology Letters
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• v.50 no.1
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• pp.89-94
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• 2022

Triclosan (TCS) is an antimicrobial agent used in various human personal care products against both gram-positive and gram-negative bacteria. The purpose of this study was to evaluate the presence of TCS-resistant bacteria in sewage water in Peshawar, Khyber Pakhtunkhwa (KPK), Pakistan, for the first time. TCS-supplemented Luria Bertani (LB) agar was used to isolate TCS-tolerant bacteria. A total of 17 TCS-resistant isolates were randomly selected from a large pool of bacteria that showed growth on TCS-supplemented LB agar. Based on gram staining and physiochemical characteristics, the isolated strains were identified as Salmonella typhi (n = 6), Escherichia coli (n = 4), Citrobacter freundii (n = 4), Proteus mirabilis (n = 1), Enterobacter cloacae (n = 1), and Pseudomonas aeruginosa (n = 1). The Triclosan mean minimum inhibitory concentrations (MICs) for the isolates of Salmonella typhi, Escherichia coli, Citrobacter freundii, Proteus mirabilis, Enterobacter cloacae, and Pseudomonas aeruginosa were 23.66 ㎍ ml^-1, 18.75 ㎍ ml^-1, 42 ㎍ ml^-1, 32 ㎍ ml^-1, 64 ㎍ ml^-1, and 128 ㎍ ml^-1, respectively. The antibiogram revealed that all isolates were resistant to penicillin G (100%) and linezolid (100%), followed by ampicillin (94%), tetracycline (76%), tazobactam (76%), sulbactam/cefoperazone (64%), polymyxin PB (58%), amikacin (29.41%), aztreonam (29.41%), imipenem (5%), and gentamicin (5%). This is the first known study regarding the isolation of TCS-tolerant bacteria from sewage water in Peshawar, KPK, Pakistan. It was concluded that all the TCS-resistant isolates were multidrug resistant (MDR) gram-negative rod-shaped bacteria, mostly belonging to the Enterobacteriaceae family.

• Korean Journal of Clinical Laboratory Science
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• v.54 no.2
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• pp.125-132
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• 2022

The prevalence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) are increasing. We analyzed the patterns of drug resistance and tracking period days of acquiring anti-mycobacterial resistance. From January 2010 to December 2019, drug susceptibility tests (DST) were performed by the absolute concentration method using the Löwenstein-Jensen solid medium and pyrazinamidase activity test (to assess pyrazinamide resistance) in samples from patients who were referred to the Green Cross Laboratories in Yongin. Among the cases that showed resistance to one or more anti-tuberculosis drugs, 55 patients (33.1%) were resistant to isoniazid (INH) at the time of initial referral, and the rates for the development of resistant anti-tuberculosis drugs were ethambutol (EMB) (26.6%), rifampicin (RFP) (21.9%), quinolones (QUI) (21.9%) and pyrazinamide (PZA) (10.9%), in that order. In the cases sensitive to all 10 anti-tuberculosis drugs initially, the development of resistance to INH was the most frequent, seen in 43 patients (7.2%). The average follow-up period was 435.6 days, and the resistance development was observed in the order of INH (7.2%), RFP (3.9%), SM (1.9%), QUI (0.7%), amikacin (AMK) (0.5%), and EMB (0.5%). The conversion of susceptible strains to resistant strains is an important warning sign for the patient, especially in cases of conversion to MDR or XDR. This information would be helpful for improving patient care during TB treatment.

• 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.

• Clinical and Experimental Pediatrics
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• v.49 no.3
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• pp.278-286
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• 2006

Purpose : Although suprapubic bladder aspiration(SBA) is the most reliable technique for identifying bacteriuria in young infant, no report has been published about the clinical manifestations of urinary tract infection(UTI) diagnosed by aspirated urine in Korea. This study was performed to examine clinical manifestations and related factors of UTI confirmed by a positive urine culture obtained by SBA in young infants. Methods : We reviewed medical records of 159 infants younger than six months of age, who had been admitted for UTI to Korea University Ansan Hospital from January 2002 to June 2005. Results : The male:female ratio was 5.1 : 1. The most common pathogen in urine culture was Escherichia coli(92.5 percent). Most of the gram-negative pathogens had high sensitivity to amikacin, or third generation cephalosporins and had low sensitivity to ampicillin, trimethoprim-sulfamethoxazole, or gentamicin. Hydronephrosis and vesicoureteral reflux(VUR) were present in 32.7 percent and 27.7 percent respectively. Renal cortical defects observed on DMSA scans were detected in 37.1 percent. Prolonged fever duration and hospital day, high erythrocyte sedimentation rate(ESR) and C-reactive protein(CRP) levels, hydronephrosis and VUR were related to the renal cortical defects(P<0.05). Rates of UTI-associated bacteremia and aseptic meningitis were 8.3 percent and 6.6 percent. Conclusion : Early differential diagnosis is very important in infants younger than 6 months of age with UTI because the clinical findings are non-specific and UTI-associated bacteremia and aseptic meningitis are concomitantly found. Because prolonged fever and higher ESR and CRP levels are risk factors of the renal cortical defects, radiologic evaluations and nephrologic follow-up were needed in identifying the predisposing congenital abnormalities and chronic renal scarring.

• Pediatric Infection and Vaccine
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• v.17 no.1
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• pp.36-48
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• 2010

Purpose : In children on anticancer chemotherapy, bloodstream infections (BSIs) are a major cause of morbidity and mortality. We investigated febrile episodes and bloodstream infections in pediatric cancer patients to guide proper selection of empiric antibiotics for febrile pediatric hemato-oncologic patients. Methods : All febrile episodes treated in the division of hematology-oncology, the department of pediatrics, Hanyang University Hospital, between July 2005 and June 2008 were reviewed. Episodes with and without bloodstream infections were compared. Results : Forty cases (18.9%, 25 patients) of BSI occurred in 212 febrile episodes (63 patients). Thirty-seven cases (23.6%, 22 patients) of BSI occurred in 157 febrile episodes with neutropenia (54 patients). Microorganisms identified in BSI corresponded to 23 gram-positive bacteria (51.2%), 20 gram-negative bacteria (44.5%), and 2 fungi (4.4%). Rates of BSI between those who had received umbilical cord blood transplantation and those who had received transplantation from other source were significantly different (55.0% vs. 7.7%, P =0.001). No differences in mortality rate were observed among organisms in BSI patients. For febrile episodes the rate of BSI was higher among those with Chemoport than those with Hickman catheter (P =0.029) and gram-positive pathogens were more likely to be associated with Chemoport (P =0.001). Conclusion : The study showed the rate of BSI, distribution of pathogens with regard to neutropenia, transplantation, central venous catheters, and antimicrobial susceptibility of pathogens in order to help guide in the choice of optimal empiric antibiotics in pediatric febrile neutropenic hemato-oncologic patients.

• Korean Journal of Veterinary Research
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• v.44 no.2
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• pp.217-224
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• 2004

This study was carried out to investigate the antibiotic resistance pattern of Listeria spp. and Staphylococcus aureus. A total of 17 (14.8%) L. monocytogenes, 13 (11.3%) L. innocua, 7 (7%) L. welshimeri, and 83 (72.2%) S. aureus were isolated from commercial poultry carcasses in Seoul and Kyonggi province during the period between 2001 and 2003. Antibiotic susceptibility test of all Listeria strains isolated was performed by the disk agar diffusion method. Antibiotics used in the study were as follows; Amikacin (An), Ampicillin (Am), Cephalothin (Cf), Chloramphenicol (C), Ciprofloxacin (Cip), Erythromycin (E), Gentamicin (Gm), Imipenem (Ipm), Kanamycin (K), Minocycline (Mi), Neomycin (N), Norfloxacin (Nor), Ofloxacin (Ofx), Penicillin (P), Streptomycin (S), Tetracycline (Te), Tobramycin (Nn), Trimethoprim (Tmp), Trimethoprim/Sulfamethoxazloe (Sxt), and Vancomycin (Va). The antibiotic resistance pattern of S. aureus isolates was performed by the disk agar diffusion method. For the latter program, antibiotics used to the study were as follows; Cf, C, Cip, Clindamycin (Cc), E, Gm, Ipm, Nafcillin (Nf), Oxacillin (Ox), P, Te, Sxt, and Va. Of the 17 L. monocytogenes isolates, 94.1% were resistant to Te, 88.2% to Mi, 11.8% to Nor, 11.8% to S, 5.9% to Cip, and 5.9% to C. Of 13 L. innocua, 53.8% were resistant to Te, 23.1% to Mi, 23.1% to S, 7.7% to Cip, and 7.7% to Nor. Of 7 L. welshimeri, 57.1% were resistant to Te, and 14.3% to Am. Of 83 S. aureus, 100% were resistant to Te, 86.7% to Gm, 34.9% to P, 15.7% to Cip, 12% to Cc, 9.6% to E. The multiple antibiotic resistance patterns of L. monocytogenes isolates were observed in Te Mi Cip (5.9%), Te Mi Nor (5.9%), Te Mi (76.5%), and Te Nor (5.9%). Multiple antibiotic resistance was also found in L. innocua isolates. Resistant to Te Mi S Cip Nor was 7.7%, Te Mi S (7.7%), Te Mi (7.7%), and was 7.7% to Te S. Antibiotic resistance patterns for S. aureus isolats were demonstrated to Te Gm P Cip Cc E (6.0%), Te Gm Cip Cc E (3.6%), Te Gm P Cc (1.2%), Te Gm P (15.6%), Te Gm Cip (2.4%), Te P Cip (2.4%), Te Gm Cc (1.2%), Te Gm (56.6%), Te P (9.6%), and to Te Cip (1.2%). The results of this study suggest a high incidence of Lsteria spp. and S. aureus on poultry carcasses. The contaminated poultry carcasses may be a potential vehicle for foodborne infections due to multiple antimicrobial resistant organisms.

• Journal of Yeungnam Medical Science
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• v.16 no.1
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• pp.60-68
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• 1999

A nationwide survey was conducted to investigate the annual occurrence rate of neonatal sepsis, maternal risk factors in neonatal sepsis, localized infection in neonates, causative organisms in nosocomial infection and the most common causative organism for neonatal sepsis in Korea. Clinical and bacteriological data wele collected from 37 neonatal units to perform retrospective review of the medical records of the newborn infants who were confirmed as having neonatal sepsis and whose blood culture was collected to isolate organisms for one year study period from January to December in 1997. 78,463 neonates were born at 37 hospital in 1997, and 20,869 neonates were admitted to the neonatal units, During this period, 772 episodes of neonatal sepsis were recorded in 517 neonates. The occurrence rate of neonatal sepsis was 0.73%(0~2.95%). Male to female ratio was 1.15:1, and 303 cases(42.1%) were born prematurely. The main pathogens of early onset of sepsis were S. aureus(20%), S. epidermidis(14.4%) and coagulase negative staphylococcus(14. 4%). Gram negative bacilli including Enterobacter spp (7.2%), E. coli(5.1%), Klepstella(4.5%), Pseudomonas(3.7%) and Enterobacter faectum(3.6%) accounted for 24.1% of sepsis. Group B beta-hemolytic streptococcus were isolated only in two cases. Common obstetric factors were PROM(21.1%), difficulty delivery(18.7%), fetal tachycardia(5.3%), chorioamnionitis(4.9%), and maternal fever(4.7%). The main pathogens of late-onset sepsis were S. aureus(22.3%), S. epidermidis(20.4%) and CONS(9.9%). There were 6 cases(1.0%) of Candida sepsis, Frequent focal infections accompanying sepsis were pneumonia(26.1%), urinary tract infection(10.5%), meningitis(8.2%), and arthritis(3.6%), S. epidermidis(22.0%) and s. aureus(21.7%) were also the most common pathogens in 373 nosocomial infection.