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PubMed1992

Comparison of ampicillin/sulbactam and amoxicillin/clavulanic acid for detection of borderline oxacillin-resistant Staphylococcus aureus.

Borderline oxacillin-resistant Staphylococcus aureus (BORSA) may be misidentified as intrinsically methicillin-resistant Staphylococcus aureus (MRSA) in the clinical laboratory. Under disk diffusion testing conditions designed to maximize detection of MRSA (incubation at 32 degrees C, pre-induction with methicillin, or plating on 4% NaCl-supplemented agar), BORSA strains also tend to appear resistant to semisynthetic penicillins. Under these conditions, ampicillin/sulbactam appears to be more accurate than amoxicillin/clavulanic acid for differentiating BORSA from MRSA.

Amoxicillin↗

PubMed1998

New strategies to prevent Staphylococcus aureus infections in peritoneal dialysis patients.

The importance of Staphylococcus aureus as etiological agent for catheter-related infections and peritonitis in peritoneal dialysis patients is well established. To evaluate groups at risk of developing Staphylococcus aureus infections, nasal and exit-site cultures were performed in 76 peritoneal dialysis patients monthly over a period of 3 yr. The risk of Staphylococcus aureus catheter infection was significantly higher in diabetic (group 1) and immunosuppressed (group 2) patients compared with nondiabetic and nonimmunosuppressed (group 3) patients. In diabetic patients, Staphylococcus aureus-positive nasal cultures were more frequent than positive cultures taken from the bland exit-site (73.3% versus 60.0%). On the other hand, both positive and negative exit-site cultures had a better prognostic value for Staphylococcus aureus catheter infection compared with nasal cultures. In immunosuppressed patients, both nasal and exit-site carriages were associated with a very high risk of Staphylococcus aureus catheter infection, but nasal swabs were far more often positive than swabs from the bland exit-site (72.7% versus 25.0%). However, the risk of infection was also high for non-nasal and non-exit-site carriers in this group. In nondiabetic and nonimmunosuppressed patients, the risk of Staphylococcus aureus catheter infection was increased only if two or more positive nasal cultures were detected. It is concluded that in diabetic patients, antibiotic prophylaxis should be performed in all Staphylococcus aureus exit-site carriers. All immunosuppressed patients should be treated prophylactically. In contrast, in nondiabetic and nonimmunosuppressed patients, prophylactic treatment should be considered only in nasal carriers with two or more positive cultures. The overall low peritonitis rate does not influence this prevention strategy.

Adult↗

PubMed1997

Comparison of screening methods to identify methicillin-resistant Staphylococcus aureus.

Screening methods to identify methicillin-resistant Staphylococcus aureus (MRSA) were compared using 96 isolates representing 17 distinct clones. The sensitivity of four commercial agglutination tests was determined in comparison to the tube coagulation test, and the results related to the presence of the coagulase gene. The broth screening test, agar dilution test and disc diffusion test were carried out, and the results related to the presence of the mecA gene. Mannitol salt agar and Iso-Sensitest agar with varying salt supplements were used. All agglutination tests had high rates of detection of Staphylococcus aureus (95.8-99.0%). Resistance in mecA gene-positive Staphylococcus aureus isolates was correctly detected by the oxacillin broth test, the agar dilution test and the disc diffusion test on mannitol salt agar, whereas on Iso-Sensitest agar detection rates were lower (between 68.5% and 94.4%, depending on the salt supplement). Incubation of the Iso-Sensitest plates for 48 hours significantly improved the rate of detection of resistance, but increased the major error rate up to 71.4%. MecA gene-positive Staphylococcus aureus isolates not detected by the disc diffusion test on Iso-Sensitest agar had significantly lower oxacillin minimal inhibitory concentration values and were significantly less resistant to a variety of antibiotics. Thus, mannitol salt agar might be a suitable medium for use in the disc diffusion and agar dilution test to detect resistance to oxacillin in Staphylococcus aureus.

Agglutination Tests↗

PubMed1992

Methicillin resistant Staphylococcus aureus.

Out of 308 isolates of Staphylococcus aureus isolated from specimens processed at the Department of Microbiology, Faculty of Medicine, Colombo 66 (21.5%) were resistant to methicillin. A significantly higher proportion of methicillin resistant Staphylococcus aureus (MRSA) were isolated from special care units, namely the Premature Baby Unit (PBU) and the Plastic Surgery Unit (PSU) when compared with other general medical and surgical units. Most of these strains were also resistant to many other antibiotics. The patients with MRSA infections had a longer mean hospital stay when compared to patients with methicillin sensitive Staphylococcus aureus (MSSA) infections. MRSA strains are as virulent as MSSA strains and these infections are mainly nosocomial.

Female↗

PubMed2025

Comprehensive genomic analysis of antibiotic resistance plasmids in animal-associated Staphylococcus aureus in France.

UNLABELLED: In Staphylococcus aureus, an animal pathogen and zoonotic agent, plasmids play a pivotal role in the acquisition and spread of antibiotic resistance genes (ARGs). This study investigated the plasmid content of 329 S. aureus isolates from livestock and companion animals collected in France between 2010 and 2021. Plasmids (n = 211) were identified from 139 isolates. The major families identified-rep7a, rep20, and rep10-were associated with specific resistance genes (str, cat, blaZ, erm(C)) and exhibited widespread horizontal transfer across different S. aureus sequence types (STs) and animal hosts. In temporal analysis, the rep7a/str and rep7a/cat plasmids circulating in horses were progressively replaced by a rep7a plasmid carrying both str and cat genes. The study also highlighted the presence of mosaic plasmids, which combined elements from different bacterial species/genera, confirming the broad host range of S. aureus plasmids and their ability to acquire ARGs from diverse sources. Moreover, the occurrence of hybrid plasmids (carrying multiple rep genes) underscores the plasticity of these vectors of ARGs. This study emphasizes the need to investigate the mechanisms driving the spread and persistence of antibiotic-resistant plasmids in S. aureus, with a view to developing strategies aimed at combating antibiotic resistance. IMPORTANCE: The spread of antibiotic resistance in Staphylococcus aureus is a growing concern, particularly in animals that can serve as reservoirs for resistant strains. This study highlights the crucial role of plasmids in transmitting resistance genes among different animal hosts and S. aureus lineages. The characterization of 329 isolates collected over 10 years revealed how certain plasmid families are associated with specific resistance genes and how they evolve over time. The occurrence of mosaic and hybrid plasmids further underscores the ability of S. aureus to acquire resistance from diverse bacterial sources. These findings provide key insights into the mechanisms shaping antibiotic resistance in this pathogen and emphasize the fact that understanding plasmid-driven resistance is essential for developing effective interventions to limit the spread of multidrug-resistant S. aureus in both veterinary and human medicine.

Animals↗

PubMed1987

Growth responses of Staphylococcus aureus and Streptococcus agalactiae to Corynebacterium bovis metabolites.

Staphylococcus aureus and Streptococcus agalactiae growth responses to metabolites of Corynebacterium bovis cultured in media containing polyoxyethylenesorbitan monolaurate, monooleate, or trioleate and milk were determined. Filter sterilized metabolites of 48-h C. bovis cultures in synthetic media were added to cultures of Staph. aureus and Strep. agalactiae. Staphylococcus aureus and Strep. agalactiae were inoculated into 12-h C. bovis milk cultures. Growth responses of Staph. aureus and Strep. agalactiae were not affected by C. bovis metabolites of synthetic media. Staphylococcus aureus growth was inhibited during logarithmic and stationary phases in milk containing mixed cultures of C. bovis compared with growth in pure Staph. aureus cultures. Streptococcus agalactiae growth curves were similar in pure and C. bovis mixed cultures. Fatty acid compositions were not different in sterile milk and milk containing bacterial cultures. Growth responses of Staph. aureus and Strep. agalactiae were not related to concentration of C. bovis metabolites or fatty acid content of media in which C. bovis were cultured.

Corynebacterium↗

PubMed2004

[Mutant prevention concentrations of fluoroquinolones for Staphylococcus aureus].

OBJECTIVE: To establish a method to measure mutant prevention concentration (MPC) in vitro, and to measure MPC of fluoroquinolones for staphylococcus aureus. METHODS: The staphylococcus aureus strain ATCC25923 and 20 ciprofloxacin-susceptible clinical isolates were enriched in broth, and the bacterial concentrations were adjusted to 10(10) colony forming units per milliliter. The minimal inhibitory concentration (MIC), MIC for 99% of input cells (MIC99), provisional MPC (MPCpr) and MPC of moxifloxacin, gatifloxacin, pasufloxacin and ciprofloxacin for staphylococcus aureus were determined by agar plates dilution method. RESULTS: The MPC of moxifloxacin, gatifloxacin, pasufloxacin and ciprofloxacin for staphylococcus aureus strain ATCC25923 were 0.18, 0.3, 0.75 and 1.8 microg/ml, and the MPC/MIC99 were 9.0, 7.5, 8.0 and 10.6 respectively. The MPC for 90% of the isolates (MPCpr90) of moxifloxacin, gatifloxacin, pasufloxacin and ciprofloxacin for 20 staphylococcus aureus clinical isolates were 1, 1, 4 and 8 microg/ml, and the MPCpr90/MIC90 were 8, 8, 16 and 16 respectively. CONCLUSION: The capacity of moxifloxacin and gatifloxacin for restricting the selection of staphylococcus aureus resistant mutants were stronger than that of pasufloxacin and ciprofloxacin. Combined with pharmacokinetic parameters, moxifloxacin and gatifloxacin may restrict the selective enrichment of resistant mutants among ciprofloxacin-susceptible staphylococcus aureus clinical isolates, and ciprofloxacin is expected to selectively enrich mutants easily.

Anti-Infective Agents↗

PubMed1999

Rapid detection of epidemic strains of methicillin-resistant Staphylococcus aureus.

Fifty methicillin-resistant Staphylococcus aureus (MRSA) initial isolates obtained from patients hospitalized in the orthopedic clinic of the Frankfurt University Hospital and 150 methicillin-sensitive Staphylococcus aureus (MSSA) isolates were investigated in this study to determine whether the Slidex Staph-Kit is capable of differentiating between MRSA and MSSA owing to its unique performance characteristics. The Slidex Staph-Kit is a combined latex hemagglutination test designed to detect clumping factor, protein A, and a specific surface immunogen for S. aureus. Clumping factor-positive strains cause erythrocytes sensitized with fibrinogen to hemagglutinate, thereby resulting in visible red clumps. S. aureus strains deficient in clumping factor agglutinate latex particles sensitized with specific antibodies against surface proteins of S. aureus, thereby resulting in visible white clumps. Our results demonstrate that white clumping has a 99% specificity as well as a 98% positive predictive value for MRSA. Clumping factor-negative MRSA, which have been reported to occur in several countries, are epidemic in the Frankfurt area and account for 80% of all MRSA initial isolates in the orthopedic clinic of the Frankfurt University Hospital. Genotyping of all MRSA isolates by macrorestriction analysis of chromosomal DNA revealed that 83% of clumping factor-negative MRSA are closely related to the "southern-German" epidemic strain. This is the first study demonstrating the Slidex Staph-Kit's capability for identifying epidemic clumping factor-negative S. aureus strains as methicillin resistant even prior to antimicrobial susceptibility testing.

Agglutination Tests↗

PubMed2004

Association between carriage of Streptococcus pneumoniae and Staphylococcus aureus in Children.

CONTEXT: Widespread pneumococcal conjugate vaccination may bring about epidemiologic changes in upper respiratory tract flora of children. Of particular significance may be an interaction between Streptococcus pneumoniae and Staphylococcus aureus, in view of the recent emergence of community-acquired methicillin-resistant S aureus. OBJECTIVE: To examine the prevalence and risk factors of carriage of S pneumoniae and S aureus in the prevaccination era in young children. DESIGN, SETTING, AND PATIENTS: Cross-sectional surveillance study of nasopharyngeal carriage of S pneumoniae and nasal carriage of S aureus by 790 children aged 40 months or younger seen at primary care clinics in central Israel during February 2002. MAIN OUTCOME MEASURES: Carriage rates of S pneumoniae (by serotype) and S aureus; risk factors associated with carriage of each pathogen. RESULTS: Among 790 children screened, 43% carried S pneumoniae and 10% carried S aureus. Staphylococcus aureus carriage among S pneumoniae carriers was 6.5% vs 12.9% in S pneumoniae noncarriers. Streptococcus pneumoniae carriage among S aureus carriers was 27.5% vs 44.8% in S aureus noncarriers. Only 2.8% carried both pathogens concomitantly vs 4.3% expected dual carriage (P =.03). Risk factors for S pneumoniae carriage (attending day care, having young siblings, and age older than 3 months) were negatively associated with S aureus carriage. CONCLUSIONS: Streptococcus pneumoniae carriage, specifically of vaccine-type strains, is negatively associated with S aureus carriage in children. The implications of these findings in the pneumococcal vaccine era require further investigation.

Carrier State↗

PubMed2003

Increasing prevalence of methicillin-resistant Staphylococcus aureus infection in California jails.

Staphylococcus aureus clinical isolates obtained from patients who were inmates of the San Francisco County jail system showed an increase in the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) from 29%, in 1997, to 74%, in 2002; 91% of the MRSA isolates carried staphylococcal chromosomal cassette mec (SCCmec) type IV. Pulsed field gel electrophoresis and multilocus sequence typing demonstrated 2 major clonal groups. One of these clonal groups is genetically indistinguishable from the strain responsible for an outbreak of MRSA in the Los Angeles County jail system in 2002.

Anti-Bacterial Agents↗

PubMed2006

Staphylococcus aureus resistance to antibiotics and spread of phage types.

OBJECTIVE: The aim of this study was to identify the phage groups of Staphylococcus aureus strains, their prevalence, and resistance of different phage groups to antibiotics. MATERIALS AND METHODS: A total of 294 Staphylococcus aureus strains in Kaunas hospitals were obtained; they were phage typed and their resistance to antibiotics was determined. We used the method of routine dilution to test 17 antibiotics against the isolates. Susceptibility of Staphylococcus aureus to studied antibiotics was estimated on the basis of National Committee for Clinical Laboratory Standards according to minimal inhibition concentration of each antibiotic. Staphylococcus aureus strains were phage typed by the international diagnostic set of Staphylococci bacteriophages (Moscow, Russia). RESULTS: After evaluating the resistance of obtained Staphylococcus aureus strains to oxacillin/methicillin, it was determined that 5.8% of Staphylococcus aureus were resistant to methicillin. Almost all strains (93.75%) of methicillin-resistant Staphylococcus aureus were susceptible to the fusidic acid, 18.75%--to ciprofloxacin; 31.25% of methicillin-resistant Staphylococcus aureus strains were susceptible to gentamicin, 37.5%--to doxycycline, and just 6.25%--to erythromycin. The strains of methicillin-susceptible Staphylococcus aureus are susceptible to many studied antibiotics. The strains of methicillin-susceptible Staphylococcus aureus are most resistant to penicillin--83.1% and to erythromycin--29.9%. Phage typing revealed that 20.9% of methicillin-susceptible Staphylococcus aureus and 56.2% of methicillin-resistant Staphylococcus aureus were nontypable. CONCLUSIONS: Using the international set of bacteriophages, 79.1% of methicillin-susceptible Staphylococcus aureus and 43.8% of methicillin-resistant Staphylococcus aureus strains were phage typed. Among the strains of methicillin-resistant Staphylococcus aureus, phagotype 77 of phagogroup III was the most common and among the strains of methicillin-susceptible Staphylococcus aureus--phagotype 3C of phagogroup II.

Anti-Bacterial Agents↗

PubMed1989

Ciprofloxacin resistance in methicillin- and gentamicin-resistant Staphylococcus aureus.

A total of 112 Staphylococcus aureus strains resistant to methicillin and gentamicin were collected from 31 centres in 22 countries worldwide. Many strains were multi-resistant. In tests to determine the susceptibility of the organisms to ciprofloxacin 16 strains (14.3%), originating from France, the FRG, Israel and Italy, were shown to be resistant to this agent. To limit ciprofloxacin resistance, a reappraisal is necessary of fluoroquinolone usage against methicillin- and gentamicin-resistant Staphylococcus aureus.

Ciprofloxacin↗

PubMed1986

A simple method for counting Staphylococcus aureus in swimming pool water.

Staphylococcus aureus counts from swimming pool water were determined by the membrane filtration technique. Water samples were passed through a membrane filter and then put on Baird-Parker media. After incubation, the filters were transferred to nutrient agar, and incubated at 37 degrees C, for 3 h. After removal of the filters, the plates were incubated at 60 degrees C for 2 h. An overlay of toluidine blue agar was added and the plates reincubated for 4 h at 37 degrees C. The formation of thermonuclease correlated with the formation of coagulase, and the results indicated that Staphylococcus aureus could be present in swimming pool water without the presence of either coliform or faecal coliform bacteria.

Enterobacteriaceae↗

PubMed1994

Comparison of traditional and molecular methods of typing isolates of Staphylococcus aureus.

Fifty-nine Staphylococcus aureus isolates and 1 isolate of Staphylococcus intermedius were typed by investigators at eight institutions by using either antibiograms, bacteriophage typing, biotyping, immunoblotting, insertion sequence typing with IS257/431, multilocus enzyme electrophoresis, restriction analysis of plasmid DNA, pulsed-field or field inversion gel electrophoresis, restriction analysis of PCR-amplified coagulase gene sequences, restriction fragment length polymorphism typing by using four staphylococcal genes as probes, or ribotyping. Isolates from four well-characterized outbreaks (n = 29) and a collection of organisms from two nursing homes were mixed with epidemiologically unrelated stock strains from the Centers for Disease Control and Prevention. Several isolates were included multiple times either within or between the sets of isolates to analyze the reproducibilities of the typing systems. Overall, the DNA-based techniques and immunoblotting were most effective in grouping outbreak-related strains, recognizing 27 to 29 of the 29 outbreak-related strains; however, they also tended to include 3 to 8 epidemiologically unrelated isolates in the same strain type. Restriction fragment length polymorphism methods with mec gene-associated loci were less useful than other techniques for typing oxacillin-susceptible isolates. Phage typing, plasmid DNA restriction analysis, and antibiogram analysis, the techniques most readily available to clinical laboratories, identified 23 to 26 of 29 outbreak-related isolates and assigned 0 to 6 unrelated isolates to outbreak strain types. No single technique was clearly superior to the others; however, biotyping, because it produced so many subtypes, did not effectively group outbreak-related strains of S. aureus.

Bacterial Typing Techniques↗

PubMed1992

[Nosocomial infections of methicillin-resistant Staphylococcus aureus and their detection].

In 142 strains of Staphylococcus aureus randomly isolated from clinical samples in a year, methicillin-resistant Staphylococcus aureus (MRSA) accounted for 79.6% (113/142). MRSA in the samples from the respiratory, burning and hematological departments came to 92.0% (23/25), 84.6% (11/13) and 83.3% (30/36) in proportion respectively. 79.6% of MRSA strains were isolated from the patients in whom the infections were confirmed to be hospital-acquired. All the strains of Staphylococcus aureus examined were resistant to penicillin G and ampicillin, but sensitive to vancomycin. Twenty hospital-acquired strains of MRSA showed a resistance to all detected antibiotics (multi-drug resistance, MDR), but vancomycin; strains of methicillin-sensitive ones, however, showed on MDR. In 45 strains of Staphylococcus aureus isolated from swabs of fingers of 62 medical workers, 31 (68.9%) were methicillin-resistant. The resistant similarity of shares of strains between medical staff and patients indicated a potential role that medical workers play in spread of nosocomial infections.

Cross Infection↗

PubMed1990

Detection of borderline oxacillin-resistant Staphylococcus aureus and differentiation from methicillin-resistant strains.

Eighty-eight Staphylococcus aureus clinical isolates meeting criteria for borderline oxacillin resistance (intermediate susceptibility or resistance to oxacillin but susceptibility to amoxicillin/clavulanic acid upon disk diffusion testing) were studied to determine optimal test techniques and conditions for differentiating borderline oxacillin-resistant Staphylococcus aureus (BORSA) from methicillin-resistant Staphylococcus aureus (MRSA). Further testing revealed three distinct resistance patterns: 61 strains (69%) consistently met BORSA criteria and had average beta-lactamase levels five- to six-fold higher than oxacillin-susceptible controls; 11 strains (13%) were markedly heteroresistant MRSA with delayed appearance of resistant colonies leading to spurious susceptibility to amoxicillin/clavulanic acid; 16 strains (18%) appeared to be oxacillin-susceptible on repetitive testing. Under conditions used to elicit intrinsic methicillin resistance in Staphylococcus aureus, a large percentage of BORSA appeared resistant to amoxicillin/clavulanic acid. This clearly shows that BORSA may be misidentified as MRSA while heteroresistant MRSA may appear to be BORSA. It is concluded that amoxicillin/clavulanic acid zone sizes should be measured after a full 24 hours of incubation, that susceptibility testing of Staphylococcus aureus under certain environmental conditions should be interpreted with caution, and that MIC testing is the most reliable technique for differentiating these two resistance patterns in Staphylococcus aureus.

Amoxicillin↗

PubMed2004

Mupirocin prophylaxis against nosocomial Staphylococcus aureus infections in nonsurgical patients: a randomized study.

BACKGROUND: Staphylococcus aureus nasal carriage is a major risk factor for nosocomial S. aureus infection. Studies show that intranasal mupirocin can prevent nosocomial surgical site infections. No data are available on the efficacy of mupirocin in nonsurgical patients. OBJECTIVE: To assess the efficacy of mupirocin prophylaxis in preventing nosocomial S. aureus infections in nonsurgical patients. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: 3 tertiary care academic hospitals and 1 nonacademic hospital. PATIENTS: 1602 culture-proven S. aureus carriers hospitalized in nonsurgical departments. INTERVENTION: Therapy with mupirocin 2% nasal ointment (n = 793) or placebo ointment (n = 809), twice daily for 5 days, started 1 to 3 days after admission. MEASUREMENTS: Nosocomial S. aureus infections according to defined criteria, in-hospital mortality, duration of hospitalization, and time to nosocomial S. aureus infection. Staphylococcus aureus isolates were genotyped to assess whether infection was caused by endogenous strains. RESULTS: The mupirocin and placebo groups did not statistically differ in the rates of nosocomial S. aureus infections (mupirocin, 2.6%; placebo, 2.8%; risk difference, 0.2 percentage point [95% CI, -1.5 to 1.9 percentage points]), mortality (mupirocin, 3.0%; placebo, 2.8%; risk difference, -0.2 percentage point [CI, -1.9 to 1.5 percentage points]), or duration of hospitalization (median for both, 8 days). However, time to nosocomial S. aureus infection was decreased in the mupirocin group from 12 to 25 days (P > 0.2). A total of 77% of S. aureus nosocomial infections were endogenous. LIMITATIONS: A few infections in both groups may have been missed because investigators assessed a patient for infection only if microbiology culture results were positive for S. aureus. CONCLUSION: Routine culture for S. aureus nasal carriage at admission and subsequent mupirocin application does not provide effective prophylaxis against nosocomial S. aureus infections in nonsurgical patients.

Administration, Intranasal↗

PubMedDate not supplied

[Rapid agglutination tests for the identification of Staphylococcus aureus].

The article deals with rapid agglutination tests for Staphylococcus aureus identification which detect clumping factor and protein A. The tests were compared with standard diagnostic methods: free coagulase, bound coagulase and thermostable deoxyribonuclease, 190 Staphylococcus aureus strains have been examined of which, 105 methicillin susceptible strains, 85 methicillin resistant strains, and 32 coagulase negative staphylococci strains strains. The presence of clumping factor was detected in 100% of examined Staphylococcus aureus strains. No difference between methicillin susceptible strains and methicillin resistant strains was observed. Protein A was present in 96.1% of methicillin susceptible strains and in 90.6% of methicillin resistant Staphylococcus aureus strains. The same test showed false negative results in 12 strains: 4 of which methicillin susceptible and 8 methicillin resistant strains. Coagulase test slide method and protein A detecting test hand one false positive result each for coagulase negative staphylococci examined. The specificity of all tests used was 100% and 99.5% respectively. The authors suggest latex or hemagglutination tests detecting clumping factor and/or protein A for rapid Staphylococcus aureus strains identification in hospital environment. It is important to point out the possibility of getting false negative protein A detecting results in methicillin resistant strains.

Hemagglutination Tests↗