Antimicrobial susceptibility of Stenotrophomonas maltophilia isolates from a Korean tertiary care hospital

We determined the antimicrobial susceptibility of 90 clinical isolates of Stenotrophomonas maltophilia collected in 2009 at a tertiary care hospital in Korea. Trimethoprim-sulfamethoxazole, minocycline, and levofloxacin were active against most of the isolates tested. Moxifloxacin and tigecycline were also active and hold promise as therapeutic options for S. maltophilia infections.     

Metallo-beta-lactamase-producing clinical isolates of Acinetobacter species and Pseudomonas aeruginosa from intensive care unit patients of a tertiary care hospital

Prompt detection of metallo-beta-lactamase (MBL) producing isolates is necessary to prevent their dissemination. Frequency of MBLs producing strains among multidrug resistant (MDR) Acinetobacter species and Pseudomonas aeruginosa was evaluated in critical care patients using imipenem-EDTA disk method. One hundred MDR Acinetobacter spp. and 42 Pseudomonas aeruginosa were checked for MBL production, from January to June 2001. MBL was produced by 96.6 % of imipenem-resistant Acinetobacter isolates, whereas 100% imipenem-resistant Pseudomonas aeroginosa isolates were MBL producers. Carbapenem resistance in MDR Acinetobacter spp. and Pseudomonas aeruginosa isolates in this study was due to MBLs. This calls for strict infection control measures to prevent further dissemination.     

Antimicrobial susceptibility pattern of clinical isolates of non-fermentative bacteria

152 nonfermentative bacteria were isolated from a total number of 965 clinical samples processed routinely in the laboratory of Microbiology Department, M.K.C.G Medical College in South Orissa accounting to a prevalence rate of 15.75%. Pseudomonas spp. (both pigmented and non-pigmented strains) were isolated in maximum percentage (73.6%) followed by Acinetobacter spp. (19.7%) and Alkaligenes faecalis (4.6%). Rarely encountered species were Eikenella corrodens (1.3%) and Stenotrophomonas maltophila (0.6%). Pus from various sites was the major source (116; 76%). 81% of all isolates were sensitive to amikacin and 74% to ofloxacin. Sensitivity to cefotaxime, ciprofloxacin, tobramycin, gentamicin and netlimycin ranged from 53% to 68%. Least effective drugs were carbenicillin and ceftriaxone (48% each).     

Antimicrobial susceptibility survey of Pseudomonas aeruginosa strains isolated from clinical sources

A two-year prospective study of 554 Pseudomonas aeruginosa isolates was recovered from various clinical sources throughout Trinidad, and their resistance patterns to antipseudomonal antimicrobial agents were determined. Of the 554 P. aeruginosa isolates, 20.6% (114/554) were community isolates, 17.3% (96/554) from the intensive care unit (ICU), 10.1% (56/554) from the nursery, and the remaining 52% (288/554) were from other hospital inpatient services. Respiratory tract infections were the predominant source of P. aeruginosa isolates from the ICU--46.9% (45/96)--and nursery--21.4% (12/56), whereas wounds were the principal source of P. aeruginosa from the surgical services--77.0% (141/183). Community isolates of P. aeruginosa were predominantly from ear--100% (51/51)--and urinary tract infections--35.5%, (33/93). The overall prevalence of resistance was low for both hospital isolates (13.9%) and community isolates (3.8%). All community isolates were fully sensitive to four of the nine antimicrobials tested. Resistance rates among community strains ranged from 2.6% (ciprofloxacin and ceftazidime) to 12.3% for piperacillin. All isolates from hospital were fully sensitive to imipenem, but resistance rates for the other drugs ranged between 2.5% and 27.3%. The study showed that the overall resistance pattern of P. aeruginosa was relatively low. This is an encouraging observation but invites caution since resistance to the newly introduced drug, cefepime, has now emerged within the hospital environment and may present serious therapeutic problems within the near future. Policies governing the use of antimicrobials in many institutions are lacking. Such policies must be instituted in order to limit the spread of resistance and also to reduce the emergence of resistance to newly commissioned drugs within the country.     

Extended spectrum -lactamases in urinary isolates of Escherichia coli and Klebsiella pneumoniae - prevalence and susceptibility pattern in a tertiary care hospital

A total of 411 urinary isolates (353 Escherichia coli and 58 Klebsiella pneumoniae) were studied for extended spectrum -lactamase (ESBL) production by double disk approximation test and NCCLS confirmatory test. ESBL production was found to be 41% in E. coli and 40% in K. pneumoniae. Fourteen percent and 12% of ESBL producers showed false susceptibility to ceftazidime and cefotaxime in routine susceptibility testing. The susceptibility of ESBL producers to imipenem, nitrofurantoin and amikacin was found to be 100%, 89% and 86% respectively. A high degree of associated resistance to gentamicin, co-trimoxazole and quinolones was found in ESBL producers. Majority of ESBL producers was detected among patients admitted in medical ICU and surgery ward.     

Effect of basic amino acids on susceptibility to carbapenems in clinical Pseudomonas aeruginosa isolates

We evaluated effects of medium composition, including basic amino acid content and pH, on susceptibility to carbapenems such as imipenem, panipenem and meropenem, in clinical isolates of Pseudomonas aeruginosa. Susceptibility to carbapenems was reduced by basic amino acids in the medium, while susceptibilities to ceftazidime and aztreonam were not. Among carbapenems, susceptibility to panipenem was most sharply reduced by addition of basic amino acids to 1:16 Mueller-Hinton agar (MHA). In 174 of 175 clinical isolates, MICs for carbapenems were affected to different degrees by medium composition. One isolate, in which MICs for carbapenems did not differ between MHA and 1:16 MHA, showed reduced production of porin (OprD). Our results suggest that susceptibility to individual carbapenems, especially panipenem, is difficult to evaluate based on MICs for other carbapenems determined on MHA. For a better prediction of antibiotic efficacy, it may be important to evaluate the susceptibility for each carbapenem individually.     

Physiological diversity in clinical isolates of Pseudomonas aeruginosa

The results of 91 characteristics selected from 165 tests performed on 127 clinical and other isolates of Pseudomonas aeruginosa were subjected to numerical analysis. Only one cluster, representing a single biotype of the species, was revealed at a similarity (SSM) level of 95% and above. Ten melanogenic and six of the non-melanogenic isolates studied gave diverse atypical results in many of the tests; these strain appear to be aberrant forms of the species.     

Antimicrobial resistance profile of nosocomial uropathogens in a tertiary care hospital

A retrospective analysis was done of the resistance pattern of urinary tract pathogens isolated over a 4 months period in a tertiary care hospital. There were a total of 871 clinical isolates comprising of 793 gram negative bacilli and 78 gram positive cocci obtained from 5477 consecutive urine samples. Extended spectrum beta lactamase production was observed in 71.5% of the gram negative bacilli; of these 6.18% were also inhibitor resistant. High level aminoglycoside resistance was observed in 70.17% of Enterococcus isolates while methicillin resistance was documented in 23.8% of the Staphylococcus isolates. A high level of resistance was also noted for ciprofloxacin. Multidrug resistance is a common problem in hospitals which emphasizes the need for judicious use of antimicrobial agents and their continuous in vitro monitoring.     

Antibiotic sensitivity pattern of Citrobacter isolated from various clinical specimens in a tertiary care hospital

A total of 709 isolates of Citrobacter species were recovered from different clinical specimens at Kasturba Medical College, Mangalore. The antimicrobial susceptibility testing of the isolates was performed using Kirby-Bauer's method of disk diffusion. All the isolates were susceptible to Imipenem (100%) and 100% resistance to Ampicillin was recorded. Susceptibility to third generation cephalosporins varied between 29 - 43%. The beta-lactamase inhibitor combination used along with beta-lactam antibiotics increased their sensitivity. The minimum inhibitory concentration (MIC) of cephotaxime to Citrobacter species was determined by agar dilution method (MIC value = or < 8 microg/ml are considered susceptible). Two hundred and fifty three strains were found to be completely susceptible, 71 strains showed intermediate susceptibility and 385 strains were completely resistant to Cephotaxime.     

Antimicrobial susceptibility pattern among methicillin resistant Staphylococcus isolates in Assam

Prevalence of methicillin resistant Staphylococcus aureus from a referral hospital in Assam was studied. Methicillin resistance among the Staphylococcus aureus isolates was 52.9% and 15% among the coagulase negative staphylococci. Resistance to all antibiotics tested among the methicillin resistant and methicillin sensitive staphylococci was found to be 23.2% and 6.6% respectively. Higher resistance to multiple antibiotics in methicillin resistant strains as compared to methicillin sensitive strains was found to be statistically significant. Ciprofloxacin resistance among the strains was still lower in comparison to the findings from other parts of the country.     

Resistance to antibiotics in clinical isolates of Pseudomonas aeruginosa

OBJECTIVES: To analyse the global resistance to some antibiotics used to treat nosocomial infections by Pseudomonas aeruginosa, specially to carbapenems, and its relationship with the presence of carbapenemases, OXA, VIM and IMP. METHODS: The study included 229 P. aeruginosa isolates from a Hospital in Northern Spain (year 2002). Susceptibility to antimicrobial agents was determined by the analysis of the MIC. Genetic typing was carried out by RAPD-PCR fingerprinting with primer ERIC-2. Genetic experiments to detect class-1 integrons were performed by PCR with primers 5'CS and 3'CS. Detection of carbapenemases was done by phenotypic (Hodge test and DDST) and genotypic methods (PCR with primers for imp, vim1, vim2 and oxa40 genes). RESULTS: 23.9% of isolates were resistant to ceftazidime, 35.9% to cefotaxime, 5.3% to amikacin, 54.9% to gentamicin, 14.6% to imipenem and 6.6% to meropenem. Isolates resistant to imipenem (33) were furtherly tested. Genetic typing didn't show clonal relatedness among the most of the isolates. Class-1 integrons were present in most isolates (sizes 600-1700 bp). Phenotypic methods for carbapenemases showed 5 positive isolates. Genotypic methods showed the presence of two isolates with the oxa40 gene. CONCLUSIONS: Meropenem, amikacin and imipenem were the most active agents to treat infections caused by Pseudomonas aeruginosa. In our study, the presence of carbapenemase enzymes wasn't high. Phenotypic tests cannot be considered as accurate screening tool to detect carbapenemases. This is the fist report of the oxa40 gene in Pseudomonas aeruginosa isolates.     

Virulence attributes in Brazilian clinical isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic human pathogen responsible for causing a huge variety of acute and chronic infections with significant levels of morbidity and mortality. Its success as a pathogen comes from its genetic/metabolic plasticity, intrinsic/acquired antimicrobial resistance, capacity to form biofilm and expression of numerous virulence factors. Herein, we have analyzed the genetic variability, antimicrobial susceptibility as well as the production of metallo-β-lactamases (MBLs) and virulence attributes (elastase, pyocyanin and biofilm) in 96 strains of P. aeruginosa isolated from different anatomical sites of patients attended at Brazilian hospitals. Our results revealed a great genetic variability, in which 86 distinct RAPD types (89.6% of polymorphisms) were detected. Regarding the susceptibility profile, 48 strains (50%) were resistant to the antimicrobials, as follows: 22.92% to the three tested antibiotics, 12.5% to both imipenem and meropenem, 11.46% to ceftazidime only, 2.08% to imipenem only and 1.04% to both ceftazidime and meropenem. Out of the 34 clinical strains of P. aeruginosa resistant to both imipenem and meropenem, 25 (73.53%) were MBL producers by phenotypic method while 12 (35.29%) were PCR positive for the MBL gene SPM-1. All P. aeruginosa strains produced pyocyanin, elastase and biofilm, although in different levels. Some associations were demonstrated among the susceptibility and/or production of these virulence traits with the anatomical site of strain isolation. For instance, almost all strains isolated from urine (85.71%) were resistant to the three antibiotics, while the vast majority of strains isolated from rectum (95%) and mouth (66.67%) were susceptible to all tested antibiotics. Urine isolates produced the highest pyocyanin concentration (20.15 ± 5.65 μg/ml), while strains isolated from pleural secretion and mouth produced elevated elastase activity (1441.43 ± 303.08 FAU) and biofilm formation (OD₅₉₀ 0.676 ± 0.32), respectively. Also, MBL-positive strains produced robust biofilm compared to MBL-negative strains. Collectively, the production of site-dependent virulence factors can be highlighted as potential therapeutic targets for the treatment of infections caused by heterogeneous and resistant strains of P. aeruginosa.