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Prevalence of antibiotic resistance among clinical isolates of methicillin-resistant staphylococci.

The prevalence of methicillin-resistant and multiply antibiotic-resistant staphylococci causing infections in hospitalized patients was studied over a two-year period. Among 122 clinically significant staphylococci, the prevalence of methicillin resistance was 66%, with a higher prevalence of Staphylococcus haemolyticus (85%) and Staphylococcus epidermidis (83%) observed than of Staphylococcus aureus (49%). Multiple antibiotic resistance was observed more frequently among coagulase-negative staphylococcus (52 to 70%) than among Staphylococcus aureus (17%). All strains of methicillin-resistant Staphylococcus aureus were susceptible to glycopeptide antibiotics and to trimethoprim-sulfamethoxazole, whereas approximately 50% of coagulase-negative staphylococci exhibited either moderate susceptibility or resistance to teicoplanin. For these latter strains, vancomycin remains the agent of choice, whereas teicoplanin cannot be recommended unless its efficacy is established by MIC determination.

Anti-Bacterial Agents↗

Distribution of coagulase-negative staphylococci, including the newly described species Staphylococcus schleiferi, in nosocomial and community acquired urinary tract infections.

Four hundred and four coagulase-negative staphylococci were isolated from 4905 urine specimens obtained from 4192 inpatients and outpatients. The distribution of the strains was as follows: 193 Staphylococcus epidermidis (47.8%), 171 Staphylococcus saprophyticus (42.3%), 29 Staphylococcus haemolyticus (7.2%), 5 Staphylococcus warneri (1.2%), 3 Staphylococcus schleiferi (0.7%), 2 Staphylococcus hominis (0.5%) and 1 Staphylococcus simulans (0.2%). All three Staphylococcus schleiferi strains were isolated from inpatients: a 64-year-old female, a 68-year-old male and a 3-month-old male with colony counts of 468,000 cfu/ml, 324,000 cfu/ml and 764,000 cfu/ml respectively. These findings show that among coagulase-negative staphylococci, Staphylococcus schleiferi, a newly described species of coagulase-negative staphylococci not previously reported as a uropathogen, may also cause hospital acquired urinary tract infection.

Aged↗

Characterization of the most frequently encountered Staphylococcus sp. in cats.

Ninety three staphylococci isolated from clinical specimens from cats were characterized and identified. Because the biochemical characteristics of Staphylococcus felis were very similar to those of Staphylococcus simulans, results were submitted to numerical analysis and DNA homology. Forty-two isolates (45%) were identified as S. felis, and 4 isolates (4%) as S. simulans. The other species identified, in order of their frequency were, 12 Staphylococcus aureus (13%), 9 Staphylococcus intermedius (10), 6 Staphylococcus sciuri (6), 6 Staphylococcus epidermidis (6), 2 Staphylococcus haemolyticus (2), 2 Staphylococcus xylosus (2), 1 Staphylococcus capitis (1), 1 Staphylococcus equorum (1), 1 Staphylococcus gallinarum (1) and 1 Staphylococcus lentus (1).

Animals↗

Survey of methicillin-resistant coagulase-negative staphylococci in the hospitals of central Greece.

A sample of 450 consecutive, non-replicated coagulase-negative staphylococci (CoNS), collected from clinical specimens during the period 2000-2001 from the five major hospitals of Thessaly district (Central Greece) were investigated for resistance to methicillin. Most of the isolates had been collected in a sporadic fashion from the intensive care units and the surgical wards of the participating hospitals. The majority of the isolates (76%) were Staphylococcus epidermidis (50%), Staphylococcus haemolyticus (14.8%) and Staphylococcus hominis (11.1%). All 316 isolates (70%) were classified as resistant according to NCCLS breakpoints (MIC > or =0.5 mg/l); 268 (59.5%) of them were mecA-positive in a PCR-based assay. All isolates with MIC > or =8 mg/l carried the gene, while, only 23.8% of isolates with MIC, 0.5-4 mg/l were carriers. Only 9% of the mecA-positive isolates were found to be sensitive to various non-beta-lactams, while 41.8% of the isolates were resistant to more than three antimicrobial groups apart from beta-lactams. Molecular typing by PFGE showed apparent heterogeneity among isolates of each species and the absence of predominant clones.

Coagulase↗

3-Methyl-3-sulfanylhexan-1-ol as a major descriptor for the human axilla-sweat odour profile.

This study sets out to redress the lack of knowledge in the area of volatile sulfur compounds (VSCs) in axillary sweat malodour. Sterile odourless underarm sweat (500 ml) was collected from 30 male volunteers after excessive sweating. Five strains of bacteria, Corynebacterium tuberculostearicum, Corynebacterium minutissimum, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Bacillus licheniformis, were isolated and characterised for their ability to generate an authentic axillary odour from the sweat material collected. As expected, all of the five bacterial strains produced strong sweat odours. Surprisingly, after extensive olfactive evaluation, the strain of Staphylococcus haemolyticus produced the most sulfury sweat character. This strain was then chosen as the change agent for the 500 ml of odourless underarm sweat collected. After bacterial incubation, the 500-ml sample was further processed for GC-olfactometry (GC-O), GC/MS analysis. GC-O of an extract free of organic acids provided three zones of interest. The first was chicken-sulfury, the second zone was onion-like, and the third zone was sweat, clary sage-like. From the third zone, a new impact molecule, (R)- or (S)-3-methyl-3-sulfanylhexan-1-ol, was isolated and identified by GC/MS, MD-GC, and GC AED (atomic emission detector). (S)-3-methyl-3-sulfanylhexan-1-ol was sniff-evaluated upon elution from a chiral GC column and was described as sweat and onion-like; its opposite enantiomer, (R)-3-methyl-3-sulfanylhexan-1-ol, was described as fruity and grapefruit-like. The (S)-form was found to be the major enantiomer (75%).

Adult↗

Methicillin-resistant staphylococcal bacteremia in patients with hematologic malignancies: clinical and microbiological retrospective comparative analysis of S. haemolyticus, S. epidermidis and S. aureus.

Although Staphylococcus haemolyticus (SH) represents an emerging etiology of methicillin-resistant (MR) coagulase-negative staphylococcal nosocomial bacteremia, little is known of clinical significance of this infection. Thus, we performed case-control retrospective comparative analysis of MRSH bacteremias (MRSHB), methicillin-resistant S. epidermidis bacteremias (MRSEB), and methicillin-resistant S. aureus bacteremias (MRSAB) in patients with hematologic malignancies. Most patients in the three groups were neutropenic and had a central venous catheter (CVC) in place at the onset of bacteremia. However, MRSHB patients had a CVC in place prior to bacteremia for a time significantly more prolonged than MRSEB and MRSAB ones (p<0.05). Severe sepsis or septic shock were more common in patients with MRSAB as compared with MRSHB (p=0.02). Nosocomial attributable mortality rate was very low in the 3 study groups (0 to 5.4%) and only two patients developed metastatic infections. Overall, reduced susceptibility to teicoplanin was observed in 19 (47.5%) MRSH and in 4 (10%) MRSE isolates. Resistance to teicoplanin was observed in 6 isolates, all MRSH. Reduced susceptibility or resistance to vancomycin was observed in 2 isolates, both MRSH. All MRSA isolates were susceptible to the glycopeptides. Comparison between cases of bacteremia in patients with MRSH isolates with reduced susceptibility to teicoplanin and those with susceptible MRSH did not reveal significant differences in the clinical-microbiological response to teicoplanin therapy and outcome. Our results seem to suggest that MRSHB in hematologic patients is associated with low morbidity and mortality rates. MRSH frequently shows a reduced susceptibility to teicoplanin; however these in vitro data do not seem associated with an unfavorable clinical response to teicoplanin therapy for MRSHB in patients with hematologic malignancies.

Adolescent↗

Trends in gram-positive bloodstream organism resistance: a seven-year audit of five glycopeptides and other drugs at a large university hospital.

Gram-positive pathogens (n = 525) isolated from bloodstream infections were tested by a reference broth microdilution method to establish antibiotic susceptibility trends (1985 to 1991). Cefazolin, ciprofloxacin, gentamicin, novobiocin, oxacillin, rifampin, teicoplanin, vancomycin, trimethoprim/sulfamethoxazole, daptomycin and two investigational glycopeptides (LY264826 and MDL62873) were investigated. Strains were selected without bias (first two isolates each month/species; no patient duplicates) as follows: 132 Staphylococcus aureus, 129 Staphylococcus epidermidis, 72 Staphylococcus haemolyticus, 130 Enterococcus faecalis and 62 other enterococci. All isolates were susceptible to vancomycin and teicoplanin except for Staphylococcus haemolyticus which had a resistant teicoplanin MIC90 of 64 micrograms/mL. The susceptibilities to vancomycin and teicoplanin were unchanged over the monitored period. Daptomycin, LY264826 and MDL62873 also demonstrated consistent activity; MDL62873 being superior with a MIC90 of 0.12 micrograms/mL. In 1990-1991 a significantly increased resistance to ciprofloxacin was observed among oxacillin-resistant strains of staphylococci. Our data suggest that the emergence of invasive vancomycin-resistant strains in Gram-positive isolates remains a rare phenomenon. However, we have experienced an emergence of numerous ciprofloxacin-resistant strains among staphylococci that precludes its empirical use at our institution.

Anti-Bacterial Agents↗

[The use of teicoplanin in neutropenic patients: values and limits].

The efficacy and the safety of teicoplanin were evaluated for the treatment of febrile episodes in neutropenic patients. A total of 18 patients received teicoplanin once daily as an intravenous injection of 200 mg in 6 patients (after a loading dose of 400 mg) or 400 mg in 12 patients (loading dose: 800 mg). The mean duration of therapy was 15.9 days (range 9 to 39 days). In all patients teicoplanin was combined with another antibiotic usually a beta-lactam. Thirteen of 18 patients were successfully treated. Three febrile episodes proved to be microbiologically documented infections and were cured by teicoplanin: one Streptococcus mitis and two methicillin-resistant (methi-R) Staphylococcus epidermidis bacteremias. Neither toxicity nor side effects were observed in the reported group. Six patients experiencing reactions to vancomycin (2 cases of cutaneous allergy) or to vancomycin and amphotericin B combination (4 cases of nephrotoxicity) were subsequently treated with teicoplanin without any evidence of cross-sensitivity. We observed emergence of teicoplanin-resistant coagulase-negative Staphylococcus in 3 patients receiving teicoplanin: 20, 18 and 8 days after a first febrile episode cured by teicoplanin and a beta-lactam, they developed fever while receiving the same antibiotic regimen. Methi-R Staphylococcus epidermidis was isolated from blood cultures in the first patient and methi-R Staphylococcus haemolyticus in the two other patients. In one patient, successfully treated by teicoplanin for a first febrile episode related to a methi-R Staphylococcus epidermidis, emergence of Staphylococcus haemolyticus occurred 8 days later while the patient was on teicoplanin therapy (6 mg/kg). MICs of teicoplanin were 16 mg/l for the two Staphylococcus strains isolated in this patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

[Prevalence of AA(6')-APH(2")Ia gene among high-level aminoglycoside resistant Enterococci and Staphylococci].

According to new reports the AAC (6')-APH (2")Ia gene is no longer the only gene encoding resistance to gentamycin in Gram-positive cocci and therefore the current method for predicting synergism aminoglycosides with bacterial cell wall active agents in this bacteria may need revision. To further our knowledge of aminoglycoside resistance mechanism in Gram-positive cocci in Gdańsk region we tested presence of AAC (6')-APH (2")Ia gene among 22 enterococcal (E. faecalis) and 41 staphylococcal (S. haemolyticus, S. aureus, S. epidermidis) gentamycin-resistant isolates. Presence of AAC (6')-APH (2")Ia gene varied from 50% (n = 6) in gentamycin-resistant S. epidermidis, 80% (n = 10) in gentamycin resistant S. haemolyticus 88% in methicillin-resistant Staphylococcus aureus (MRSA) (n = 25). In Enterococcus faecalis this gene was noticed only in 59% (n = 22) of gentamycin-resistant isolates. These results suggest that spread of resistance gene among different species is limited and AAC (6')-APH (2")Ia mediated gentamycin-resistance mechanism is more common among MRSA and Staphylococcus haemolyticus.

Aminoglycosides↗

[In vitro susceptibilities of clinical isolates of coagulase-negative staphylococci to glycopeptide antibiotics].

Two hundred and thirteen clinical strains of coagulase-negative staphylococci isolated in Japan between 1980 and 1997 were analyzed for glycopeptide susceptibility by determining MIC using both Mueller-Hinton agar (MHA) and Brain Heart Infusion agar (BHIA) plates. Of 37 Staphylococcus epidermidis strains isolated between 1980 and 1981, all were susceptible to vancomycin and teicoplanin on both MHA and BHIA. However, of 122 isolates of Staphylococcus epidermidis isolated between 1994 and 1997, 1 (0.8%) was intermediate to vancomycin on MHA and 39 (32%) were intermediate on BHIA, while 3 (2.5%) and 27 (22.1%) were intermediate or resistant to teicoplanin on MHA and BHIA, respectively. It was demonstrated that the susceptibilities of the strains in 1990s to vancomycin and teicoplanin were significantly decreased compared with those in 1980s. Population analysis was performed with six strains each of Staphylococcus epidermidis and Staphylococcus haemolyticus (three with vancomycin MIC > or = 8 micrograms/ml and three with vancomycin MIC < or = 4 micrograms/ml using BHIA). The population curves of the Staphylococcus epidermidis strains showed a homogeneous pattern of susceptibility. Whereas, those for two Staphylococcus haemolyticus strains (vancomycin MIC = 8 micrograms/ml using BHIA) showed a typical heterogeneous pattern. Vancomycin-resistant mutants (MIC > or = 32 micrograms/ml) were obtained with a high frequency of 10(-4)-(-5) from the strains by one-step selection with 16 micrograms/ml of vancomycin.

Anti-Bacterial Agents↗

Increased oxacillin activity associated with glycopeptides in coagulase-negative staphylococci.

Vancomycin resistance in methicillin-resistant staphylococci presents a potential therapeutic problem. In order to understand the impact of low-level vancomycin resistance in coagulase-negative staphylococci, stepwise selection of vancomycin resistance was accomplished by growing Staphylococcus haemolyticus in culture media with increasing concentrations of vancomycin. A >40-fold increase in susceptibility to beta-lactam antibiotics was observed. No obvious alterations in the growth curve, the presence of the mecA gene, total DNA restriction fragment length polymorphism (RFLP), beta-lactamase production, or the crude protein fraction were detected in the Staphylococcus haemolyticus-derived clones when compared to the original isolate. The proportion of the oxacillin-heteroresistant population also remained similar. A comparable phenomenon occurred with the selection of Staphylococcus epidermidis exhibiting low-level resistance to vancomycin. Additionally, it was observed that clinical isolates of coagulase-negative staphylococci grown in the presence of sub-minimum inhibitory concentrations of either vancomycin or teicoplanin lost their high-level resistance to oxacillin. Checkerboard tests showed that the combination of vancomycin and oxacillin was synergistic for two isolates of Staphylococcus haemolyticus, two of four isolates of Staphylococcus epidermidis, and one isolate of Staphylococcus hominis.

Anti-Bacterial Agents↗

Emergence of teicoplanin-resistant coagulase-negative staphylococci.

Over a period of 5 years we have recovered 32 clinical isolates of coagulase-negative staphylococci (CoNS) exhibiting either decreased levels of susceptibility or true resistance to teicoplanin (MICs, 16 to 128 micrograms/ml); these isolates make up 0.55% of the total CoNS isolated by us. Twenty-nine of the strains were also methicillin resistant, and all were susceptible to vancomycin. Fourteen of the strains were Staphylococcus epidermidis, fourteen were Staphylococcus haemolyticus, and four were Staphylococcus hominis. In one case, a strain of S. haemolyticus was isolated with a vancomycin-resistant, teicoplanin-resistant Enterococcus faecalis strain. All strains were nosocomially acquired and were isolated from 17 different wards. Teicoplanin resistance occurred as a sporadic phenomenon, and none of the isolates were epidemiologically related. The isolates were from 30 patients, 13 of whom presented with true infections (43%). Five (38%) of the 13 patients with true infections had been previously treated with vancomycin. None of the infected patients were previously treated with teicoplanin. The in vivo development of resistance to teicoplanin among CoNS strains limits the therapy of infections by these microorganisms. There is a need for surveillance of nosocomial isolates of CoNS to determine resistance to glycopeptides.

Aged↗

Observations on coagulase-negative staphylococci in a neonatal unit in India.

Fifty neonates were included in a prospective study which determined the frequency of colonization and infection with coagulase-negative staphylococci (CNS) in a neonatal unit. The isolates were characterised by species, antibiotic resistance and ability to produce slime. Twenty-four epidemiologically related isolates (including four isolates from the hands of staff) were also phage typed and had plasmid analysis performed. On the first day of birth, 18% of infants were colonized with CNS, 40% and 30% by days 3-5 and day 7 respectively, and 25% by the 14th day and beyond. Staphylococcus haemolyticus and S. epidermidis were the most frequent CNS species encountered, accounting for 36% and 35% of isolates. Resistance to four or more antibiotics was present in 37% of strains isolated on the first day and this increased to 100% of isolates from infants who stayed for more than 14 days. Forty-five percent of CNS were slime producers; no significant difference was observed in slime producing ability between the species or isolates at different days after birth. Five infants developed septicaemia due to CNS. Staphylococcus haemolyticus and S. epidermidis were recovered as the only pathogens from three and two cases respectively. Detailed typing revealed that one case of infection with S. haemolyticus was preceded by surface colonization with an identical strain. Evidence was also obtained for the transmission of CNS between babies on the hands of staff.

Age Factors↗

Genomic characterization of efflux pumps and putative small multidrug resistance (SMR)-like transporters in disinfectant-tolerant coagulase-negative staphylococci from a Vietnamese hospital.

Coagulase-negative staphylococci (CoNS) are common inhabitants of healthcare environments and can serve as reservoirs of antimicrobial resistance determinants. However, the relationship among disinfectant tolerance, efflux-associated phenotypes, and multidrug resistance in environmental CoNS remains incompletely defined. Here, 51 staphylococcal isolates were recovered from high-touch hospital surfaces in Hanoi, Vietnam, and 14 isolates showed elevated MICs to at least one disinfectant, including benzalkonium chloride, chlorhexidine gluconate, or hydrogen peroxide, relative to Staphylococcus aureus ATCC 25923. These isolates also displayed multidrug-resistant phenotypes. Moreover, ethidium bromide accumulation assays revealed a clear efflux-associated phenotype, and representative isolates exhibited biofilm-forming ability. Whole-genome sequencing of three representative isolates reclassified SDH.B1 and SDH.B3 as Staphylococcus nepalensis-a CoNS species rarely documented in hospital AMR surveillance-and confirmed SDH.B7 as Staphylococcus haemolyticus. To our knowledge, this is among the first reports of S. nepalensis carrying mecA together with the disinfectant efflux gene qacG, and a set of putative small multidrug resistance (SMR)-like transporters in a hospital environment from Southeast Asia. In addition, six putative SMR-like proteins were identified. Phylogenetic and structural analyses suggested relatedness to YkkC/YkkD-like systems, although their transport activity remains to be experimentally verified. These findings identify environmental CoNS as reservoirs of disinfectant tolerance and multidrug resistance in hospital settings and provide a basis for future functional investigation of putative SMR-like transporters.IMPORTANCEHospital environmental CoNS are often dismissed as low-priority contaminants, yet they may persist under disinfectant pressure and carry clinically relevant resistance determinants. Here, disinfectant-tolerant CoNS recovered from a Vietnamese hospital combined multidrug resistance, efflux-associated phenotypes, and biofilm-related traits. Genome analysis further revealed known qac genes and six putative SMR-like proteins that merit functional testing. These findings support inclusion of environmental CoNS in infection-prevention surveillance and disinfectant stewardship programs.

Staphylococcus haemolyticus↗

Application of molecular typing methods to characterize nosocomial coagulase-negative staphylococci collected in a Greek hospital during a three-year period (1998-2000).

A total of 143 methicillin-resistant coagulase-negative staphylococci (MR-CNS) collected between 1998 and 2000 at the University Hospital of Patras, Greece, were characterized by antibiogram and genomic typing to define the clonal types endemic in this hospital and their evolution during the 3-year period. These isolates corresponded to 93 methicillin-resistant Staphylococcus epidermidis (MRSE) and 50 other MR-CNS, which were isolated from patients in different wards, exclusively from blood and catheter tips cultures. Pulsed-field gel electrophoresis (PFGE) of SmaI macrofragments and hybridization of ClaI digests with mecA and murE DNA probes were performed. The application of these methodologies demonstrated the existence, persistence and spread of MRSE, MR-Staphylococcus haemolyticus, and MR-Staphylococcus hominis clones in this hospital, whereas the SmaI/murE hybridization pattern was shown to be a valuable tool for the MRSE identification.

Bacterial Typing Techniques↗

A comparison of antimicrobial resistance rates in Gram-positive pathogens isolated in the UK from October 1996 to January 1997 and October 1997 to January 1998.

Rates of resistance for two consecutive years for 28 centres (10 Teaching, nine Associate Teaching and nine District General hospitals) in the UK were compared. Combined rates of resistance for each of the hospital types of Staphylococcus aureus to methicillin revealed an increase in the rate of resistance in Teaching hospitals (12.5% year 1, 23.5% year 2), but, for Associate Teaching and District General hospitals rates fell (Associate Teaching 19.1% year 1, 11.9% year 2; District General 16.5% year 1 and 11.3% year 2). Using conventional methodology to determine MICs, no strain was considered to have reduced susceptibility to vancomycin. Among coagulase-negative staphylococci, increased resistance was observed for Staphylococcus epidermidis to rifampicin, for Staphylococcus haemolyticus to clindamycin, for Staphylococcus saprophyticus to penicillin and for Staphylococcus spp. to clindamycin, methicillin and rifampicin. For Streptococcus pneumoniae an upward trend in low-level resistance to penicillin was observed (18 of the 28 centres), however, for high-level resistance the trend was in the opposite direction (only four centres showed an increase). For Enterococcus faecalis there was a trend to a fall in levels of resistance, the only exception being an increase in high-level gentamicin resistance (10.5% year 1, 15.1% year 2, P = 0.0388). For Enterococcus faecium rates of resistance were not significantly different except for increases in resistance to nitrofurantoin and rifampicin.

Anti-Bacterial Agents↗

Human choriogonadotropin-like material in bacteria of different species: electron microscopy and immunocytochemical studies with monoclonal and polyclonal antibodies.

Immunocytochemical studies using antisera to whole human choriogonadotropin (hCG), to its alpha- and beta-subunits and to the COOH-terminal peptide of hCG beta, and two monoclonal antibodies to hCG beta, demonstrated expression of hCG-like material, its individual subunits and/or fragments in nine bacterial strains. Seven of these were isolated from patients with cancer and were definitely identified as Streptococcus faecalis (three strains), Staphylococcus haemolyticus (two strains) and Staphylococcus epidermidis and Escherichia coli (single strains). The other two strains were cell-wall-deficient (CWD) variants, one identified as Streptococcus bovis, isolated from the blood of a patient with a fever of unknown origin and a possible brain abscess. The other was a Gram-negative diphtheroid isolated from the urine of a pregnant woman, which during the period of study reverted to a Gram-positive Corynebacterium identified as a 'C. ulcerans' strain and expressed the hCG-like factor only during its phase as Gram-negative diphtheroid. Electron microscopy of these nine strains (including negative controls of strains of the same species subjected to the same immunocytochemical analyses and under identical cultural conditions) revealed morphological alterations in the bacterial cell walls and cytoplasmic material and/or bizarre forms of reproduction in six of the nine strains expressing hCG-like material including the two CWD variants. Collectively, these results provided evidence that (1) hCG-producing bacteria isolated from patients with overt cancer are not a new and unique species as claimed by others, and (2) there is a close resemblance between the bacterial protein and the human trophoblastic hormone, based on immunochemical recognition of different parts of the hCG molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗