Phage Typing Patterns Research Articles

Antimicrobial Susceptibility, Phage Typing and Plasmid Profile of Salmonella enterica Serotype paratyphi A Strains Isolated in Kuwait

Objective: To determine the antimicrobial susceptibility, phage type and plasmid profile pattern of Salmonella enterica serotype paratyphi A strains isolated in Kuwait. Material and Methods: From January 1995 to December 1999, 106 strains of S. enterica serotype paratyphi A isolated from an equal number of cases of enteric fever, attending the Infectious Disease and Mubarak Al-Kabeer Hospitals in Kuwait were investigated. The isolates were tested for antimicrobial susceptibility to 8 commonly used antimicrobial agents. Their phage type and plasmid profile patterns were determined using an international set of phages and Qiagen plasmid mini kit, respectively. Results: All of the isolates were susceptible to ciprofloxacin, cefuroxime, ceftazidime, piperacillin and co-trimoxazole. One hundred isolates were susceptible to ampicillin, 99 to chloramphenicol and 98 to tetracycline. None of the isolates was multidrug resistant. Sixty-six percent of the isolates were phage type I, 27.4% phage type II and 6.6% were untypable. All phage type I and untypable strains had 3 plasmids of 2.2, 5 and 20 kb, whereas phage type II strains had only 1 plasmid of 20 kb. Conclusion: The findings indicate that while all of the isolates of the S. enterica serotype paratyphi A were susceptible to 4 of the drugs tested, some were resistant to ampicillin, chloramphenicol or tetracycline, thereby indicating the need for continued surveillance and monitoring of antimicrobial susceptibility of these isolates.

Community acquisition of gentamicin-sensitive methicillin-resistant Staphylococcus aureus in southeast Queensland, Australia.

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) susceptible to gentamicin has been reported in a number of countries in the 1990s. To study the acquisition of gentamicin-sensitive MRSA (GS-MRSA) in southeast Queensland and the relatedness of GS-MRSA to other strains of MRSA, 35 cases of infection due to GS-MRSA from October 1997 through September 1998 were examined retrospectively to determine the mode of acquisition and risk factors for MRSA acquisition. Thirty-one isolates from the cases were examined using a variety of methods (antibiotyping, phage typing, pulsed-field gel electrophoresis [PFGE] fingerprinting, and coagulase typing by restriction analysis of PCR products) and were compared with strains of local hospital-acquired gentamicin-resistant MRSA (GR-MRSA) and of Western Australian MRSA (WA-MRSA). Only 6 of 23 cases of community-acquired GS-MRSA had risk factors for MRSA acquisition. Twenty of 21 isolates from cases of community-acquired infection were found to be related by PFGE and coagulase typing and had similar phage typing patterns. Hospital- and nursing home-acquired GS-MRSA strains were genetically and phenotypically diverse. Community-acquired GS-MRSA strains were not related to nosocomial GR-MRSA or WA-MRSA, but phage typing results suggest that they are related to GS-MRSA previously reported in New Zealand.

Interpretation of band differences to distinguish strains of Serratia marcescens by pulsed-field gel electrophoresis of XbaI DNA digests

The number of band differences in DNA macrorestriction profiles required to distinguish unrelated strains from an index strain varies in an outbreak with the species and restriction enzyme used. In order to define this difference for epidemiological studies of Serratia marcescens, we produced DNA fingerprints from 57 isolates of the organism using the restriction enzyme XbaI and pulsed-field gel electrophoresis (PFGE). The isolates were selected on the basis of their epidemiology, serotype and phage-typing patterns to include 28 unrelated strains and 29 representatives from 2 distinct outbreaks. One of the outbreaks was prolonged. lasting for several years. Electrophoretic profiles consisting of 20 or more clearly resolved bands were obtained for all isolates. Twenty-six of the unrelated strains had unique profiles with over 10 band differences from all other strains, while 27 of the outbreak representatives could be assigned to the appropriate outbreak with confidence. The majority of the outbreak isolates had none or 2 band differences from the index profile, although 3 isolates differed by 5-7 bands. The 2 exceptions among the unrelated strains differed by 4 bands, and 3 phage typing reactions, and were isolated from London and Berlin 3 years apart, while the 2 exceptions among the outbreak collection had clearly unique profiles with over 20 band differences from each other and the outbreak profiles. Cluster analysis using Dice coefficient and UPGMA gave cut-off values of 75-78% similarity overall for related isolates, while the closest similarity for unrelated strains was 70%. The results of this study together with those of the 6 previous reports of PFGE for S. marcescens (which used either enzymes XbaI or SpeI) confirm that this technique is of value for this species and that with XbaI at least, most epidemiologically related strains will only differ by 3-4 bands. However, on occasion up to 7 band differences can be found within an apparent outbreak, which may be suggestive of genetic drift.

Molecular typing of multiple-antibiotic-resistant Salmonella enterica serovar Typhi from Vietnam: application to acute and relapse cases of typhoid fever.

The rate of multiple-antibiotic resistance is increasing among Salmonella enterica serovar Typhi strains in Southeast Asia. Pulsed-field gel electrophoresis (PFGE) and other typing methods were used to analyze drug-resistant and -susceptible organisms isolated from patients with typhoid fever in several districts in southern Vietnam. Multiple PFGE and phage typing patterns were detected, although individual patients were infected with strains of a single type. The PFGE patterns were stable when the S. enterica serovar Typhi strains were passaged many times in vitro on laboratory medium. Paired S. enterica serovar Typhi isolates recovered from the blood and bone marrow of individual patients exhibited similar PFGE patterns. Typing of S. enterica serovar Typhi isolates from patients with relapses of typhoid indicated that the majority of relapses were caused by the same S. enterica serovar Typhi strain that was isolated during the initial infection. However, some individuals were infected with distinct and presumably newly acquired S. enterica serovar Typhi isolates.

The independent evolution of resistance to ciprofloxacin, rifampicin, and fusidic acid in methicillin-resistant Staphylococcus aureus in Australian teaching hospitals (1990-1995). Australian Group for Antimicrobial Resistance (AGAR).

Methicillin-resistant Staphylococcus aureus (MRSA) is endemic in teaching hospitals in eastern Australian states, with prevalence rates averaging 25-30% of all S. aureus. Between 1990 and 1995, 1467 non-duplicate MRSA isolates from clinically infected sites were tested in Sydney, Melbourne, and Brisbane as part of a national survey of staphylococcal susceptibility. We reviewed the differing evolution of resistance to ciprofloxacin, rifampicin, and fusidic acid. Despite similarities in community and hospital antibiotic use and MRSA prevalence rates, trends in resistance to the oral antibiotics in these cities have progressed independently of each other. In the 1995 survey in individual hospitals in Melbourne, 16-24% of strains were ciprofloxacin-resistant, compared with 80-100% in Sydney and 30-44% in Brisbane. There was great diversity of phage type patterns for ciprofloxacin-resistant strains, suggesting heterogeneous development of resistance. Rifampicin resistance was more closely associated with distinct dominant epidemic phage types, common to institutions in the same city, but without spread to the other cites. Between 1990 and 1995, these comprised 30-60% of all MRSA in Brisbane, compared with 5-10% in Melbourne and < 25% in Sydney. Fusidic acid resistance was uncommon and sporadic (< 5%), and was distributed equally between methicillin-resistant and methicillin-susceptible strains. Resistance to the oral agents in MRSA is due to a complex mix of antibiotic selection pressures and cross-infection with local and epidemic strains in closely related institutions. Each of these mechanisms can predominate, dependent on local factors and the antibiotics used.

Control of an outbreak of an epidemic methicillin-resistant Staphylococcus aureus also resistant to mupirocin

An epidemic methicillin-resistant Staphlococcus aureus (EMRSA-3) appeared in a District hospital in June 1989 as part of a regional outbreak. The dynamics of the outbreak were complex and involved patient transfer between hospitals and wards. Control measures followed UK guidelines and included the use of nasal mupirocin. During these efforts a mupirocin-resistant MRSA [MuMRSA: mupirocin minimum inhibitor concentration (MIC) > 256 mg/L] emerged, probably in a patient who had been given eight mupirocin courses over nine months. The MuMRSA had a narrower phage-typing pattern than EMRSA-3, but was indistinguishable by pulsed-field gel electrophoresis of SmaI chromosomal restriction enzyme digests and its susceptibility pattern to other antibiotics. The results of in vitro curing and gene probing indicated that mupirocin resistance was encoded on a 48 Md plasmid. MuMRSA spread occurred in 12 patients and 11 staff. The affected patients were nursed on the same ward. The strain was eradicated from patients with oral ciprofloxacin and rifampicin, triclosan skin treatment and nasal fusidic acid and bacitracin cream. The control of the outbreak had significant medical, social and financial implications. Fortunately, there were alternative topical agents to mupirocin, an agent which has played such a key role in MRSA eradication in recent years.

Plasmid profile and phage type of Salmonella typhimurium strains encountered in different regions of India

A total of 190 Salmonella typhimurium strains encountered in different parts of India were characterized on the basis of plasmid profile, phage type and antimicrobial resistance pattern. Recent trends in the epidemiology of R-plasmids were also studied. The majority of S. typhimurium strains (90.5%) were untypable by phage typing. Only 18 strains (9.5%) were phage typable. The phage untypable strains isolated from northern (57) central (65), and southern (50) regions of India could be subgrouped into 24, 12 and 16 different plasmid profiles respectively. Heterogeneity was the prominent feature although most of the plasmid profiles were related among strains isolated from particular place. A great diversity among small plasmids (2.7–8.3 kb) made subgrouping of majority strains (71%) with R-pattern ApCmKmSmSuTcTp possible. Conjugation studies and plasmid profile analysis of transconjugants revealed all the strains to harbour non conjugative non-auto transmissible plasmids with the exception of 7.2 and 2.7 kb plasmids which were not mobilizable.

Prevalence of erm gene classes in erythromycin-resistant Staphylococcus aureus strains isolated between 1959 and 1988.

The epidemiology of the two common erythromycin resistance methylase (erm) genes ermA and ermC was analyzed by Southern blotting in 428 erythromycin-resistant Staphylococcus aureus strains isolated from blood between 1959 and 1988 in Denmark. ermA and/or ermC was present in 98% of the erythromycin-resistant strains tested. ermA was found only as a chromosomal insert and was solely responsible for erythromycin resistance in these strains until about 1971. ermA was the only erm gene found in 337 strains and was a single insert in 61% of these strains, two inserts were seen in 37%, and three inserts were found in 2%. Thirteen different ermA EcoRI restriction fragment length polymorphisms were identified. ermA was not found in strains of phage type patterns group II and type 95, which are very common today. ermC was found on a plasmid in 77 strains. ermC was first seen in 1971 and spread rapidly in the S. aureus population, with a 5- to 10-fold increase every 5 years, and in 1984 to 1988, it was responsible for erythromycin resistance in 72% of the strains. The predominant plasmid carrying ermC was 2.5 kb, while four plasmids were smaller and three were larger. ermC has been found in all phage type patterns. Eight strains contained combinations of ermA and ermC, and no erm gene was detected in six strains.

開業医療施設におけるＭＲＳＡの現状について

An increased number of cases of methicillin resistant staphylococcus aureus (MRSA) infection has been reported in hospitalized patients in university hospitals. It is estimated that approximately 16-20% of patients in the otolaryngological departments of such hospitals suffer from MRSA infections. However, accurate statistics of MRSA in outpatients in the private clinics of ENT practitioners have not been compiled.The authors attempted to determine the incidence of MRSA infections in outpatients treated in these clinics, using the same OPA staphylococcus agar and epidemiological markers such as phage typing patterns, coagulase type, enterotoxin and toxic shock syndrome toxin-1.We found 2% of the MRSA in both private ENT clinics.The epidemiological data suggest that MRSA was not of epidemic type.

Staphylococcus aureus bacteremia: a 14-year nationwide study in hematological patients with malignant disease or agranulocytosis.

This retrospective nationwide study of 756 cases of S. aureus bacteremia in hematological patients, between 1977-1990, confirms that S. aureus bacteremia is disproportionately prevalent among, and a major cause of morbidity and mortality in, hematological patients. The case mortality rate attributable to S. aureus bacteremia (44%) was significantly higher than the rate (29%) found in patients without hematological disease. A decreasing mortality was, however, observed from the first to the last part of the study period (53 and 37% respectively). A logistic regression analysis showed that mortality was further dependent on age, the type of hematological disease and origin of infection/primary focus of infection. Analysis of clinical features confirmed that in comparison with other patients, S. aureus bacteremia in hematological patients more often was hospital-acquired, acquired without known portal of infection/primary focus of infection and much less frequently resulted in osteomyelitis or endocarditis. From phage typing and antibiotic susceptibility patterns no specific types of S. aureus were associated with hematological patients.

Epidemiology of Staphylococcus aureus bacteremia in Denmark.

The number of Staphylococcus aureus bacteremia cases has increased annually in Denmark during the latest decades. This increase has occurred among older patients with hospital-acquired bacteremia. Methicillin-resistance, which earlier was a property of strains of the 83A phage-complex, has nearly disappeared, while the frequency of penicillin-resistance has increased. Today both the phage-type pattern and antibiotic resistance are nearly similar for strains from hospital-acquired and community-acquired cases. In hospitals the frequency of bacteremia after postoperative wound infections has decreased, while cases associated with intravascular catheters has increased, and these infections are now the most common cause of hospital-acquired S. aureus bacteremia. Endocarditis is most commonly found in community-acquired cases without an identified primary focus in patients between 21-50 years. Also hematogenous osteomyelitis is most common in community-acquired cases, but these infections have changed to having a high predilection for the vertebral column, and the prevalence of chronic cases has decreased.

Distribution of phagetype patterns of Mycobacterium tuberculosis isolated in Cuba (1987-1991).

Distribution of phagetype patterns of Mycobacterium tuberculosis isolated in Cuba (1987-1991).

Staphylococcus aureus phage typing, antimicrobial susceptibility patterns and patient data correlated using a personal computer: advantages for monitoring the epidemiology of MRSA

Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA) is an important nosocomial pathogen. A problem encountered in the control of staphylococcal nosocomial infection is the difficulty correlating data available from antimicrobial susceptibility patterns (usually available locally) with phage typing patterns which are generally determined in a reference laboratory. Data problems are exaggerated because many patients have numerous samples taken over long periods of time. This paper describes the use of a database, ‘DataEase’, on a personal computer to correlate available data with patient demographics and to present the resulting information in whatever format is required. The information might be presented as the phage pattern of each isolate from patients in a particular unit per month or as a combination of the phage types and antimicrobial susceptibility patterns of isolates from a particular unit. The system can be used to generate a list of all isolates for phage typing in a format that allows the phage typing pattern to be recorded directly onto the list worksheet. In addition to providing clinically relevant reports, the system simplifies the collation of epidemiological information, data from which showed that since 1987 the incidence of MRSA has been rising in the group of hospitals served by this laboratory; MRSA of phage type 83A became a problem during 1990 and 1991; the incidence of gentamicin-sensitive phage type non-typable MRSA increased fourfold between 1988 and 1991; and the incidence of gentamicin-resistant MRSA rose sharply in 1992.

A double outbreak of exfoliative toxin–producing strains ofStaphylococcus aureusin a maternity unit

This report describes a double outbreak of staphylococcal scalded skin syndrome (SSSS) in which two distinct tetracycline-resistant strains of Staphylococcus aureus producing different exfoliative toxins were involved. In the first phase the daytime staff of the delivery unit and eczematous skin conditions in midwives were implicated as the probable source. In the second phase a source within a post-natal ward was suggested with local cross-infection. In the final phase both sources were epidemiologically linked to cases of SSSS. Because early discharge was the policy of the unit many cases presented in the community rather than in the hospital. Confirmation of epidemiological findings was provided by additional laboratory studies. Two distinct strains of S. aureus could be defined, differing in phage-typing patterns, the exfoliative toxin produced, plasmid profile, cadmium resistance and bacteriocin production. Strict care in hand washing with a chlorhexidine-containing detergent was an important control measure.

Catheter-related Staphylococcus aureus infections

Among 3394 patients with Staphylococcus aureus bacteraemia from the years 1986–1989, 88 patients were found whose intravenous catheter and blood grew organisms of the same phage type. Strains of phage type 95 were more frequent among the patients with confirmed catheter-related bacteraemia than among other bacteraemia cases. Strains with particular phage-type patterns occurring with increasing frequency in Denmark during recent years also occurred with significantly higher frequencies among the confirmed catheter-related bacteraemias. No major differences in antibiotic resistance were observed. Patients with catheter-related bacteraemia had, in spite of a higher frequency of underlying diseases, a lower mortality compared with other bacteraemia patients, and endocarditis occurred less frequently (2% vs. 6%). Among 201 S. aureus isolates from catheters in 1988 only strains of group I occurred with increased frequency. The possible role of catheters as selection pressure on the S. aureus population is discussed.

Application of phage typing to the identification of sources of groundwater contamination

Phage typing of Escherichia coli populations was used as a “fingerprinting” tool to identify the source(s) of fecal coliform contamination of a drinking water well, PW- 12. Group discriminate analysis was used to evaluate the data and determine the relative distance of population centroids from the centroid of the PW- 12 population. The phage typing patterns were compared to serological results and correlations noted. Phage typing patterns were shown to be stable following 32-days incubation of E. coli isolates in garden soil, tap water and neutralized tertiary effluent, with and without the presence of autochthonous flora.

The use of biochemical fingerprinting, phage typing and antimicrobial-susceptibility testing in the detection of epidemic strains of Salmonella of serotype Typhimurium in Iran.

A collection of 86 strains of Salmonella of serotype Typhimurium isolated from children with gastroenteritis in Tehran, Iran was examined for biochemical phenotype, phage type and antibiotic-resistance pattern. Twenty-seven biochemical phenotypes (BPTs), 14 discrete phage types (PTs) and 18 resistotypes (RTs) were identified. Fifty-three strains (62%) belonged to two major and probably related BPTs, whereas the other 33 isolates belonged to less common BPTs. The two predominant BPTs contained 26 strains of the same PT and 23 strains of the same RT. Different PTs and RTs of strains with similar BPT were sometimes observed, possibly reflecting antibiotic pressures in Iran. These results suggest that two major "clones" of Typhimurium strains are particularly common in Iran and, although each method alone adequately detected these and other less common "clones", biochemical fingerprinting provided additional information about relationships among strains.

The prevalence, antibiotic susceptibility and phage-type of nasally carried Staphylococcus aureus in the Dublin community.

A study was undertaken to determine the distribution, antibiotic susceptibility and phage type pattern of nasally-carried Staphylococcus aureus in the community. Coagulase-positive staphylococci were isolated from 180 of 440 individuals. The rate was higher in the inner city and among young adults and middle-aged males. The isolates were examined for phage-type patterns and antibiotic susceptibility. Most (60.6%) of the isolates were typable either at Routine Test Dilution (RTD) or at 100 RTD. Most belonged to phage group I (53.2%) and phage group III (21.1%). Susceptibility to penicillin and ampicillin was low at 12.3 and 15.5% respectively. All were susceptible to vancomycin. Methicillin-resistance was unexpectedly low at 0.6% whereas tetracycline and erythromycin resistance were in line with recent trends at 4.5 and 2.7%. The rate of multiple resistance was low at 2.3%.

Epidemiological studies of penicillin resistance in Danish Staphylococcus aureus strains in the period 1977-1990.

During the period 1977-1990 the frequency of penicillin resistance increased from 78.7 to 87.5% among a total of 278,193 Danish Staphylococcus aureus strains from hospitalized patients. By combining these data with phage-type patterns the increase was shown to be caused by 1) the introduction and spread of mainly resistant strains of type 95 and the 94,96 complex; 2) an increased occurrence of strains of group II which during the observation period became more frequently penicillin resistant; and 3) a gradual disappearance of strains of group III and the 83A complex which showed a decreasing degree of penicillin resistance. During the observation period community acquired strains reached nearly the same level of penicillin resistance as the hospital-acquired strains, and the frequency of penicillin resistance did not increase during hospitalization among the predominant strains of type 95, group II and the 94,96 complex. S. aureus isolated from airways had a higher frequency of penicillin resistance mainly caused by increasing amount of penicillin resistant strains of group II. Strains from urine had a lower frequency of penicillin resistance. The total antibiotic consumption and the usage of beta-lactam antibiotics remained nearly unchanged during the observation period. The frequent use of beta-lactam antibiotics for airway infections might explain the possible selection of penicillin resistant strains of group II.

Evolution of Staphylococcus aureus resistance to erythromycin in Denmark, 1959 to 1988: correlations between characteristics of erythromycin-resistant bacteraemia strains

In an attempt to characterize erythromycin-resistant Staphylococcus aureus we present the intricate relationships between the following factors: phage type, period of isolation, antibiogram, minimum inhibitory concentration (MIC) to erythromycin, inducible or constitutive resistance, spectinomycin susceptibility, hospital- or community-acquired infection, and mortality rate. We studied 718 cases of bacteraemia with erythromycinresistant S. aureus, occurring between 1959 and 1988. Central factors were phage type pattern, period of isolation, and antibiogram. Between 1959 and 1973 the majority of the erythromycin-resistant strains were multiresistant and belonged to the 83A complex and the related group III. They were mainly inducibly resistant, spectinomycin resistant, and had intermediate MICs (1–4 mg l −1) to erythromycin. The majority of these strains came from hospital-acquired infections and still exist today, although in decreased numbers. By contrast, erythromycin-resistant S. aureus isolated in recent years are usually co-resistant only to penicillin and more rarely also to tetracycline. These strains have inducible resistance, are spectinomycin susceptible, and have a high erythromycin MIC. They are isolated both from hospital- and community-acquired infections. Strains with constitutive resistance to macrolides occurred at a stable low level (13%) during the whole observation period and always had high MICs to erythromycin. The mortality rate among patients with S. aureus bacteraemia due to an erythromycin-resistant strain was only associated with the year of infection and decreased from 61% in the first 15-year period to 40% in the subsequent 15 years.