Staphylococcus aureus phage types and their correlation to antibiotic resistance.

Context: Staphylococcus aureus is one of the most devastating human pathogen. The organism has a differential ability to spread and cause outbreak of infections. Characterization of these strains is important to control the spread of infection in the hospitals as well as in the community. Aim: To identify the currently existing phage groups of Staphylococcus aureus, their prevalence and resistance to antibiotics. Materials and Methods: Study was undertaken on 252 Staphylococcus aureus strains isolated from clinical samples. Strains were phage typed and their resistance to antibiotics was determined following standard microbiological procedures. Statistical Analysis: Chi square test was used to compare the antibiotic susceptibility between methicillin resistant Staph. aureus (MRSA) and methicillin sensitive S. aureus (MSSA) strains. Results: Prevalence of MRSA and MSSA strains was found to be 29.36% and 70.65% respectively. Of these 17.56% of MRSA and 40.44% of MSSA strains were community acquired. All the MSSA strains belonging to phage type 81 from the community were sensitive to all the antibiotics tested including clindamycin and were resistant to penicillin. Forty five percent strains of phage group III and 39% of non-typable MRSA strains from the hospital were resistant to multiple antibiotics. Conclusion: The study revealed that predominant phage group amongst MRSA strains was phage group III and amongst MSSA from the community was phage group NA (phage type 81). MSSA strains isolated from the community differed significantly from hospital strains in their phage type and antibiotic susceptibility. A good correlation was observed between community acquired strains of phage type 81 and sensitivity to gentamycin and clindamycin.

Tracing lineage by phenotypic and genotypic markers in Salmonella enterica subsp. enterica serovar 1,4,[5],12:i: - and Salmonella Typhimurium isolated in state of São Paulo, Brazil

Fifty-three Salmonella 1,4,[5],12:i:- and 45 Salmonella Typhimurium strains were characterised using phage typing, plasmid profiles and pulsed-field gel electrophoresis (PFGE) for comparison. The majority of the strains were subdivided into definitive type (DT) 41 (22.6 percent) and DT 193 (18 percent) and the 60-MDa plasmid was detected in 94.3 percent and 84.4 percent of strains, respectively. Genetic diversity was observed among all strains and 90 percent presented a > 70 percent similarity through PFGE analysis. These results suggest a close relationship between Salmonella 1,4,[5],12:i:- and Salmonella Typhimurium at the serotype level.

Phenotypic and genotypic characterization of Salmonella Enteritidis isolates

In order to study the epidemiology of Salmonella Enteritidis outbreaks and determine the source of contamination so that a recurrence can be avoided, detailed characterization is necessary. Thus, the purpose of this study was to verify whether rep-PCR was able to discriminate among Salmonella Enteritidis isolates. Phage typing, detection of virulence genes and antimicrobial resistance testing were also associated to rep-PCR results. One hundred and two S. Enteritidis isolates from broiler carcasses, food, human, pigs, poultry-related samples, and nine isolates from other countries were genotypically typed by REP-PCR, ERIC-PCR and BOX-PCR, collectively called rep-PCR. Phage typing, detection of virulence genes and antimicrobial resistance testing were also performed. Only three fingerprinting profiles were obtained with each rep-PCR method, with the majority of isolates belonging to the same profile. No relationship was observed between genotypic profile and year, place of isolation or source of infection. However, the less frequent rep-PCR profiles showed single antimicrobial resistance patterns. Although few strains isolated from swine were analyzed, different antimicrobial resistance patterns were observed. Furthermore, phage type 4 was not found in swine isolates. rep-PCR showed a lower discriminatory power as compared with antimicrobial resistance and phage typing, but the combination of genotypic and phenotypic methods was more discriminatory than any method alone, resulting in 48 different types.

Uma caracterização detalhada de Salmonella Enteritidis é necessária para que possa ser desenvolvido o estudo da epidemiologia dos surtos causados por este organismo, bem como a determinação da fonte de contaminação, evitando que ocorram novos surtos. Assim, o objetivo deste estudo foi verificar se a rep-PCR era capaz de diferenciar isolados de S. Enteritidis. A fagotipagem, a detecção de genes de virulência e a determinação de resistência antimicrobiana foram associadas aos resultados da rep-PCR. Cento e duas S. Enteritidis isoladas de carcaças de frango, alimentos prontos para consumo, humanos suínos, amostras relacionadas a aves, e nove isolados de outros países foram genotipicamente tipados por REP-PCR, ERIC-PCR e BOX-PCR, juntamente chamados de rep-PCR. A fagotipagem, a detecção de genes de virulência e a determinação de resistência antimicrobiana também foram realizadas. Somente três padrões de fingerprinting foram obtidos com cada método de rep-PCR, sendo que a maioria dos isolados pertenceu ao mesmo perfil. Nenhuma relação foi observada entre o perfil genotípico e o ano, o local de isolamento e a fonte de infecção. Entretanto, os perfis menos freqüentes de rep-PCR apresentaram padrões de resistência antimicrobiana únicos. Embora poucas amostras de suínos tenham sido analisadas, diferentes padrões de resistência antimicrobiana foram observados. Além disso, o fagotipo 4 não foi encontrado em isolados de suínos. A rep-PCR apresentou um menor poder discriminatório quando comparada com a resistência antimicrobiana e com a fagotipagem, mas a combinação dos métodos genotípicos e fenotípicos foi mais discriminatória do que qualquer método isolado, resultando em 48 tipos diferentes.

Phage Typing of Staphylococcus intermedius Isolated from Canine Clinical Specimens

Bacteriophages were induced from staphylococcus intermedius isolates from dogs and used for a phage typing. Mitomycin C induction was performed on 60 strains of S. intermedius and all phages were reacted with the strains. Twenty-eight strains (46.7%) were found to be lysogenic. Based on host ranges, eight phages were selected. By using the eight phages, 129 strains isolated from canine clinical specimens were subjected to the phage typing at the routine test dilution (RTD) and 100xRTD. Typability of the phage set was 78.3%, yielding 40 phage patterns. The phage set was considered useful for differentiating S. intermedius strains isolated from dogs. None of 50 strains of S. aureus, 2 (3.6%) of 56 S. simulance strains, 13 (24.5%) of 53 S. chromogenes strains and 46 (28.1%) of 164 S. hyicus strains were typable by the phages at 100xRTD.

Characteristics of Epidemic Multidrugresistant Salmonella enterica Serovar Typhimurium DT104 Strains First Isolated in Korea / 감염

BACKGROUND: Salmonella infections continue to cause gastrointestinal and systemic diseases throughout the world. S. Enteritidis and S. Typhimurium were traditionally known as typical food poisoning Salmonella agents, the isolation rate of which has been increased recently in Korea. S. Typhimurium phage type DT104 has become an important emerging pathogen. Isolates of this phage type often possess resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline (ACSSuT resistance). The mechanism by which DT104 has accumulated resistance genes is of interest, since these genes interfere with treatment of DT104 infections and might be horizontally transferred to other bacteria, even to unrelated organisms. METHODS: All the isolates included in this study were identified as S. enterica serovar Typhimurium according to the Kauffmann-White serotyping scheme and were definitive phage type DT104 according to the phage typing scheme described by Anderson, et al. A total of 63 isolates of S. enterica serovar Typhimurium DT104 were characterized by antimicrobial resistance analysis, pulsed-field gel electrophoresis (PFGE) with the restriction enzyme XbaI. RESULTS: Four hundred ninety six S. Typhimurium isolates were divided into 28 different phage types and DT104 was the second most common phage type in Korea. A total of 63 S. Typhimurium DT104 isolates were grouped into 7 resistance phenotypes. Fourty one (65.1%) isolates were resistant to the ACSSuTTic core alone or to additional drugs as well except twenty two (33.9%) isolates were resistant to the ASSuTeTic. Four PFGE subtypes A1, A2, B1, and B2 were observed among DT104 isolates and type A1 was prevalent. CONCLUSIONS: We concluded two distinct clones were present among Korea multidrug resistant S. enterica serotype Typhimurium DT104 and multidrug resistant S. Typhimurium phage type DT104 has been an important emerging pathogen in Korea.

Molecular Analysis of Salmonella enterica Serotype typhi Isolated Sporadically in Seoul City / 감염

BACKGROUND: Typhoid fever, caused by Salmonella enterica serotype Typhi, remams an important public health problem in Korea, and asymptomatic chronic carriers play a role in the endemicity. However, the molecular studies of S. typhi isolates are very limited. We characterized clinical isolates of S. typhi by molecular and phage typing tools for the extent of genetic diversity and relatedness among the isolates. METHODS: A total of 49 S. typhi isolates from sporadic cases of typhoid fever were collected in 3 university hospitals in Seoul during 1992 to 1998 and examined for in vitro susceptibility to 14 antimicrobials by disk diffusion method, ribotyping using PstI restriction enzyme, and pulsed-field gel electrophoresis (PFGE) using XbaI and Vi phage typing. The distribution of the epidemiological types and genomic DNA relatedness were analyzed. RESULTS: Forty-five out of 49 isolates were susceptible to all drugs tested. Thirty-two out of 47 were typable by phage typing and 56.3% possessed the phage type El or Ml. Forty-nine isolates divided into 6 different ribotypes (A to F) and 19 different PFGE types (AO through A17, BO) by ribotyping and PFGE analysis, respectively. Based on the 3 typing systems, 32 isolates divided into 17 different epidemiological types. The E1-A-A12 (phage type-ribotype-PFGE type) was most prevalent (18.8Fo) and isolated only in 1998, but distributed in various areas of isolation. The next prevalent M1-A-A1 (15.6%) was isolated from 1992 through 1998. The genetic relatedness based on PFGE analysis revealed that F (coefficient of similarity) values are 0.64 to 1.0 and 0.52 for A subtypes and BO type, respectively. CONCLUSIONS: We conclude that the circulating S. typhi strains in Seoul city show considerable genetic diversity, whereas most of them seems to be clonally related.

Pulsed-Field Gel Electrophoresis Pattern, Phage Type and Drug Susceptibility of Salmonella typhi Isolates from an Outbreak in Pusan City in 1996 / 감염

BACKGROUND: During the period from April to June 1996, an outbreak of typhoid fever occurred in SuYoung-Ku, Pusan city. We performed the molecular epidemiological analysis and drug susceptibility test for 48 isolates of Salmonella typhi from the outbreak. METHODS: Chromosomal DNA of S. typhi was digested with the restriction endonuclease Spe I and the resulting restriction polymorphism was observed on pulsed field gel electrophoresis (PFGE). Phage typing was performed using Vi-phages, and antimicrobial susceptibility test was done by Disc diffusion method. RESULTS: On phage typing, 2 isolates were M1 phage type, 2 E1 phage type and 44 untypable. The PFGE analysis on 14 to 16 chromosomal DNA restriction fragments ranged from 50 Kb to 1000kb showed 2 different patterns of restriction fragments, divided into group A and B. Forty-seven isolates belonged to group A that were allocated into A1 (42 strains), A2 (1 strain), A3 (3 strains), A4 (1 strain), and one strain was grouped into group B. In the F-value of genetic similarity of the epidemic S. typhi strains, there was low similarity (F value:0.2-0.258) between group A strains and group B strains. However, the subgroup strains (A1-A4) showed high similarity (F value:0.8-0.897) each other. The drug susceptibility test showed susceptibility to ampicillin, carbenicillin, cephalothin, chloramphenicol, tobramycin, gentamicin, kanamycin, nalidixic acid, neomycin, polymyxin B, streptomycin, tetracycline, trimethoprim-sulfamethoxazole, ciprofloxacin and norfloxacin. CONCLUSION: This study showed that phage typing and PFGE were very useful as a tool to investigate molecular analyses of epidemic S. typhi strains this study.