Active Antimicrobial Agents Research Articles

Nosocomial bloodstream infections caused by Acinetobacter species in United States hospitals: clinical features, molecular epidemiology, and antimicrobial susceptibility.

We examined the clinical and epidemiological features of nosocomial bloodstream infections (BSIs) caused by Acinetobacter species and observed from 1 March 1995 through 28 February 1998 at 49 United States hospitals (SCOPE National Surveillance Program). Acinetobacter species were found in 24 hospitals (49%) and accounted for 1.5% of all nosocomial BSIs reported. One hundred twenty-nine isolates were identified either as A. baumannii (n=111) or other Acinetobacter species (n=18). Patients with A. baumannii BSI, compared with patients with nosocomial BSI caused by other gram-negative pathogens, were more frequently observed in the intensive care unit (69% vs. 47%, respectively; P<.001; odds ratio [OR] 2.4; 95% confidence interval [CI] 1.6-3.7) and were more frequently receiving mechanical ventilation (58% vs. 30%, respectively; P<.001; OR 3.2; 95% CI 2.1-4.8). Crude mortality in patients with A. baumannii BSI was 32%. Molecular relatedness of strains was studied by use of polymerase chain reaction-based fingerprinting. Clonal spread of a single strain occurred in 5 hospitals. Interhospital spread of epidemic A. baumannii strains was not observed. The most active antimicrobial agents against A. baumannii (90% minimum inhibitory concentration values) were imipenem (1 mg/L; 100% of isolates susceptible), amikacin (8 mg/L; 96%), tobramycin (4 mg/L; 92%), and doxycycline (4 mg/L; 91%). Thirty percent of isolates were resistant to > or =4 classes of antimicrobials and were considered to be multidrug resistant.

Antimicrobial susceptibility of staphylococci isolated from otitis externa in dogs.

Samples were obtained from 65 unmedicated adult dogs, processed for isolation of Staphylococcus species and tested for susceptibility to penicillin G, gentamicin, oxacillin, tetracycline, trimethoprim-sulphamethoxazole, streptomycin, ampicillin and rifampin. Forty-four isolates were obtained, which represents 67.7% of samples. Coagulase-negative species were most commonly found, and the most frequently isolated staphylococcus species were Staph. epidermidis and Staph. aureus. Other species, such as Staph. simulans, Staph. haemolyticus, Staph. saprophyticus and Staph. intermedius were also isolated. Resistance to antibiotics was frequently observed, with 90.9% of the isolates showing resistance to at least one drug. The most active antimicrobial agents against staphylococci isolated from otitis externa of dogs were rifampin and oxacillin. Multidrug resistance was a common finding, and one strain of Staph. haemolyticus species, was resistant to all tested antimicrobial agents. Resistance to three or more different drugs was a common finding, observed in 16 strains (36.4%) of both coagulase-positive and coagulase-negative staphylococci. This study highlights the emergence of cases of otitis externa determined by coagulase-negative staphylococcus strains and once more emphasizes the need for bacterial culture with species identification and susceptibility testing of swab specimens from the ear canal in order to choose appropriate antimicrobial agents.

Respiratory tract pathogens isolated from patients hospitalized with suspected pneumonia: frequency of occurrence and antimicrobial susceptibility patterns from the SENTRY Antimicrobial Surveillance Program (United States and Canada, 1997)

Thirty-seven sentinel hospitals (29 in the United States [US]; eight in Canada) collected bacterial isolates from hospitalized patients with a diagnosis of pneumonia. The antimicrobial susceptibility patterns of these pathogens were determined to more than 60 agents (40 reported) using the reference broth microdilution method described by the National Committee for Clinical Laboratory Standards. The five most frequently recorded species among the 2757 isolates collected during the study were (no. tested/%): Staphylococcus aureus (632/22.9%), Pseudomonas aeruginosa (498/18.1%), Haemophilus influenzae (284/10.3%), Klebsiella spp. (240/8.7%), and Streptococcus pneumoniae (213/7.7%). There was a significant difference in the susceptibility to antimicrobials between the US and Canada for S. aureus to oxacillin (50.1% versus 93.8% susceptible, respectively), gentamicin (78.7% versus 97.8%), and fluoroquinolones (49.5 to 53.0% versus 89.8 to 94.9%). Amikacin (92.8% susceptible) was the most active antimicrobial agent against P. aeruginosa, and meropenem was the most potent β-lactam. Against H. influenzae, most drugs retained a high level of activity, whilst against the S. pneumoniae, only the newer fluoroquinolones (gatifloxacin, levofloxacin, sparfloxacin) remained highly effective in vitro. Only two antimicrobial agents (imipenem and meropenem) were >99% active against the Klebsiella spp. and Enterobacter spp. isolated in this survey (possess extended spectrum β-lactamases or hyperproduction of Amp C cephalosporins); cefepime (95.6–100.0% susceptible) was significantly more active than other cephalosporins tested. Clonal, epidemic outbreaks of multiply resistant strains were very rare in monitored hospitals. In conclusion, important differences exist between the US and Canada in the susceptibility patterns of some respiratory tract pathogens to commonly used antimicrobial agents with Canadian strains generally being more susceptible to currently available antimicrobial agents.

Susceptibility of Polish clinical strains of Yersinia enterocolitica serotype O3 to antibiotics

A total of 199 clinical strains of Yersinia enterocolitica serotype O3, biotype 4 were tested for their susceptibility to antibiotics (158 strains carried the virulence plasmid pYV and 41 strains did not). A total of 114 isolates were tested by a standard disk diffusion method for 21 antibiotics. Almost all strains tested were resistant to ampicillin and cefazolin and susceptible to amoxycillin/clavulanate, cefaclor, cefamandole, cefuroxime, cefotaxime, ceftriaxone, aztreonam, imipenem, gentamicin, amikacin, netilmicin, tetracycline, doxycycline, chloramphenicol, ciprofloxacin, sulphamethoxazole, trimethoprim, co-trimoxazole and furazolidone. In addition, minimal inhibitory concentrations of 15 antibiotics were determined by the agar dilution method for all 199 strains (158 carrying plasmid pYV and 41 strains that did not). Third-generation cephalosporins such as cefotaxime and ceftriaxone and a fluoroquinolone (ciprofloxacin) were the most active antimicrobial agents tested followed by aztreonam, imipenem, trimethoprim, tetracycline, gentamicin, chloramphenicol, amoxycillin/clavulanate, cefaclor, cefuroxime, amikacin, furazolidone and sulphamethoxazole. The present study demonstrated a high susceptibility of clinical strains of Y. enterocolitica to most of the tested antibiotics. In general there was no significant difference between susceptibility to antibacterial agents of strains with or without plasmid pYV.

In vitro susceptibilities to 23 antimicrobial agents of Haemophilus influenzae from pediatric patients in Japan.

One hundred eighty-six clinical isolates of Haemophilus influenzae (H. influenzae) collected from January 1996 through December 1997 from 182 pediatric patients and 16 isolates from blood or cerebrospinal fluid (CSF) of 13 patients with bacteremia and purulent meningitis collected during the last ten years were examined for in vitro susceptibilities to 23 antibiotic agents, including 3 penicillins, 9 cephalosporins, 4 carbapenems and others, as well as for their encapsulated types and beta-lactamase production. Ceftriaxone (a third generation cephalosporin) had the highest activity against the strains in this study (minimal inhibitory concentration, MIC90 of 0.025 microgram/ml) and cefditoren (a new oral cephalosporin) was the most active oral antimicrobial agent (MIC90 of 0.05 microgram/ml). Meropenem had a much higher activity against H. influenzae (MIC90 of 0.2 microgram/ml) than the other carbapenems (imipenem, MIC90 of 1.56 micrograms/ml, panipenem, MIC90 of 1.56 micrograms/ml, and biapenem, MIC90 of 3.13 micrograms/ml). Regarding the serotyping of the encapsulated strains, 172 strains (85.1%) were nontypeable and 30 (14.9%) were serotyped (24 strains of type b, 4 strains of type e, one each of type a and c). Fifteen of the strains isolated from blood and CSF were type b and one was nontypeable. Sixteen of 202 strains (7.9%) produced beta-lactamase and all of them produced both penicillinase and cephalosporinase. The production of beta-lactamase in this study was lower than that reported in previous studies [1-3]. In this study, some strains were found against which the MICs of carbapenems were very high (highest MIC of imipenem was 12.5 micrograms/ml, of panipenem was 6.25 micrograms/ml and of biapenem was 25 micrograms/ml). Therefore, we assayed the binding affinities of imipenem for each of penicillin-binding proteins (PBPs) about one of these resistant strains. In resistant strains, inhibitory concentrations (IC50) of imipenem for PBP4 and 5 were much higher than those in susceptible strains. Thus, the results demonstrate the decrease of the affinity of imipenem for PBP4 and 5. It seems, therefore, that the major factor in the resistance to imipenem of H. influenzae was the low affinity of PBP4 and 5 for the drug.

Synthesis of a new cephalosporin monomer

A new potentially active antimicrobial agent has been synthesized. This new monomer is a cephalosporin derivative carrying a pyridine ring substituted with a polymerizable vinyl group in the C-3 position of the pyridine ring. 3-Vinyl pyridine was first synthesized by a Wittig reaction between 3-pyridine carboxaldehyde and methyl phosphonium bromide. Cefotaxime was then quaternized with this species via nucleophilic substitution at the C acetate group.

Synthesis, antibacterial, antifungal and anti-HIV evaluation of Schiff and Mannich bases of isatin derivatives with 3-amino-2-methylmercapto quinazolin-4(3H)-one

Isatin (Indole 2,3-dione), its 5-chloro and 5-bromo derivatives were added to 3-amino-2-methylmercapto quinazolin-4(3H)-one to form Schiff bases and the N-Mannich bases of these compounds were synthesized by reacting with formaldehyde and several secondary amines. Their chemical structures have been confirmed by means of their IR, 1H-NMR data and by elemental analysis. Investigation of antimicrobial activity of compounds was done by an agar dilution method against 26 pathogenic bacteria, 8 pathogenic fungi and anti-HIV activity against replication of HIV-1 (III B) in MT-4 cells. Among the compounds tested 5-chloro-3-(3′,4′-dihydro-2′-methylmercapto-4′-oxoquinazolin-3′-yl)-1-morpholino methyl imino isatin was the most active antimicrobial agent.

Prevalence and antimicrobial susceptibility of staphylococci isolated from saliva of clinically normal cats.

Samples were collected from 150 adult cats, processed for isolation of Staphylococcus species and tested for susceptibility to penicillin G, gentamicin, oxacillin, enrofloxin and tetracycline. Methicillin resistance was also determined. One hundred and four isolates were obtained (69.3% of samples). Coagulase-negative species were most common, and the most frequently isolated (33 samples) species was Staph. felis. Other coagulase-negative species, such as Staph. haemolyticus, Staph. simulans, Staph. epidermidis and Staph. saprophyticus were also isolated. Coagulase-positive staphylococci were obtained from 30 cats, and the only species recovered in this group was Staph. intermedius. Resistance to antibiotics was frequently observed, with 68.2% of the isolates showing resistance to at least one drug. Resistance to Penicillin G was observed in 68 of the 104 isolates (65.4%), 23 samples were resistant to oxacillin (22.1%), 33 to tetracycline (31.7%) and 24 to enrofloxin (23.1%). Gentamicin was the most active antimicrobial agent. The role of these microorganisms in the saliva of cats is discussed.

The Macrolides: Erythromycin, Clarithromycin, and Azithromycin

In addition to erythromycin, macrolides now available in the United States include azithromycin and clarithromycin. These two new macrolides are more chemically stable and better tolerated than erythromycin, and they have a broader antimicrobial spectrum than erythromycin against Mycobacterium avium complex (MAC), Haemophilus influenzae, nontuberculous mycobacteria, and Chlamydia trachomatis. All three macrolides have excellent activity against the atypical respiratory pathogens (C. pneumoniae and Mycoplasma species) and the Legionella species. Azithromycin and clarithromycin have pharmacokinetics that allow shorter dosing schedules because of prolonged tissue levels. Both azithromycin and clarithromycin are active agents for MAC prophylaxis in patients with late-stage acquired immunodeficiency syndrome (AIDS), although azithromycin may be the preferable agent because of fewer drug-drug interactions. Clarithromycin is the most active MAC antimicrobial agent and should be part of any drug regimen for treating active MAC disease in patients with or without AIDS. Although both azithromycin and clarithromycin are well tolerated by children, azithromycin has the advantage of shorter treatment regimens and improved tolerance, potentially improving compliance in the treatment of respiratory tract and skin or soft tissue infections. Intravenously administered azithromycin has been approved for treatment of adults with mild to moderate community-acquired pneumonia or pelvic inflammatory diseases. An area of concern is the increasing macrolide resistance that is being reported with some of the common pathogens, particularly Streptococcus pneumoniae, group A streptococci, and H. influenzae. The emergence of macrolide resistance with these common pathogens may limit the clinical usefulness of this class of antimicrobial agents in the future.

Prevalence and antimicrobial susceptibility of staphylococci isolated from the skin surface of clinically normal cats.

Samples were collected from 148 adult cats, processed for isolation of Staphylococcus species and tested for susceptibility to penicillin G, gentamicin, oxacillin, amoxycillin, ampicillin, cephalexin and rifampin. Methicillin resistance was also determined. Ninety-eight isolates were obtained (66% of samples). Coagulase-negative species were most common, and the most frequently isolated species (37 samples) was Staph. felis. Other coagulase-negative species, such as Staph. simulans, Staph. epidermidis and Staph. saprophyticus were also isolated. Coagulase-positive species were obtained from 40 cats; the most frequent was Staph. intermedius (26 samples), followed by Staph. aureus (14 samples). Resistance to antibiotics was frequently observed, with 58.2% of the isolates showing resistance to at least one drug. Resistance to Penicillin G was observed in 49 of the 98 isolates (50%), 22 samples were resistant to oxacillin (22.4%) and 12 to rifampin (12.2%). Resistance to amoxycillin and ampicillin was very similar to that observed to Penicillin G. Gentamicin was the most active antimicrobial agent. Three MRSA (methicillin-resistant Staphylococcus aureus) were isolated, which represents 21.4% of the isolates of that species. Nineteen MRS (methicillin resistant staphylococci) were also observed, distributed among Staph. intermedius (eight), Staph. simulans (six) and Staph. felis (five) isolates. The role of these micro-organisms on the skin of cats is discussed.

EVALUATION OF HOSPITAL ACQUIRED PSEUDOMONAS INFECTION IN PARAPLEGIC AND ORTHOPAEDIC CASES

One hundred isolates of Pseudomonas aeruginosa from patients of the spinal cord injury and orthopaedic centre were evaluated on the basis of 2 laboratory assays; antibiotic sensitivity and pyocin typing. Antibiotic drug resistance was found in 54 per cent of the isolates. The urinary tract, pressure sores and wound swabs were the most common clinical specimens. Spinal cord injury patients showed a high rate of nosocomial colonisation. Ceftazidime, amikacin, norflox and ciprofloxacin were the most active antimicrobial agents. Gentamicin, carbenicillin and tobramycin showed high resistance. Pyocin typing with 22 strains did yield information to establish a clinico - epidemiological relationship.

In vitro activity of meropenem against organisms causing serious infections in a Singapore hospital

Meropenem (MEM) is a carbapenem antibiotic effective against infections caused by a variety of organisms. This study was conducted to evaluate MEM, which has not been previously used in the hospital, in parallel with some antimicrobial agents now in use, against organisms causing serious infections in the hospital. A total of 382 organisms isolated from blood cultures were included in the study. In the case of Bacteroides spp. and Burkholderia pseudomallei, organisms recovered from blood as well as from other sites were also included. In addition to MEM, 12 antimicrobial agents were tested against Gram-negative bacilli and seven against staphylococci. Antimicrobial susceptibility testing was carried out by the Kirby-Bauer disc diffusion technique based on the M2-A4 standard. The present paper demonstrates that meropenem, imipenem and ciprofloxacin are the most active antimicrobial agents against clinically important organisms causing serious infections in the hospital.

Non‐specific defence mechanisms in fish, with particular reference to the reticuloendothelial system (RES)

An efficient clearance and degradation system may be needed during microbial invasion which otherwise would lead to severe inflammation and eventually death. Non‐specific defence mechanisms in fish play an important role at all stages in infection. The non‐specific humoral defence including proteases, lysins and agglutinins, for example, in mucosal secretion is the first line of defence, whereas mucosal lining cells function as the second barrier against invasion. Blood cells, especially granulocytes and monocytes, may destroy microbes present in the circulation and may function as the third line of defence. Finally, endocytically active cells such as endothelial cells, macrophages and granulocytes in organs and tissues may take up and degrade microbes or microbial products. The endocytic and degradation processes strongly depend on the effectiveness of the reticuloendothelial system which consists of endothelial cells and macrophages that line small blood vessels (e.g. sinusoids and ellipsoids). Potentiation of non‐specific defence mechanisms may occur during microbial invasion, leading to more efficient clearance and destruction of pathogens or other harmful substances. In microbial invasion, an inflammatory response such as elevated production of antimicrobial substances is often encountered. Central cells in the production of antimicrobial substances are macrophages and granulocytes, and microbial products in inflammation may alter the cells function to a more activated state in vivo. Activated cells may enhance their antimicrobial capacity and efficiency by producing higher amounts and more active antimicrobial agents. This review concerns the non‐specific defence system and gives an introduction to some of the known non‐specific humoral substances and their induction/suppression, and provides a more extensive introduction to cytokine research and immunomodulation. Cellular aspects of non‐specific defence, including macrophages and their products, are discussed in the light of their function in the reticuloendothelial system in fish.

Antimicrobial susceptibility of clinical isolates of Acinetobacter baumannii

The in-vitro activity of 18 antimicrobial agents alone or in combination against 248 clinical isolates of Acinetobacter baumannii from Taiwan were tested by agar dilution. The MIC 90s of ampicillin, amoxicillin, piperacillin, cefuroxime, cefotaxime, ceftriaxone, gentamicin, and amikacin were at least 128 μg/ml. Ceftazidime, cefepime, sulbactam, clavulanic acid, and tazobactam presented moderate activity with MIC 90s of 32, 16, 16, 32, and 32 μg/ml, respectively. The increased activity of ampicillin/sulbactam, amoxicillin/clavulanic acid, and piperacillin/tazobactam was due to the intrinsic effect of sulbactam, clavulanic acid, and tazobactam, respectively. Imipenem, meropenem, and ciprofloxacin were the most active antimicrobial agents with MIC 90s of 1, 1, and 0.5 μg/ml, respectively. Nineteen isolates (7.7%) were resistant to all aminoglycosides and β-lactam antibiotics, except carbapenems and ciprofloxacin. We are concerned about the multidrug resistance of A. baumannii in this study.

In vitro activity of meropenem against ciprofloxacin-resistant enterobacteriaceae and Pseudomonas aeruginosa.

The in-vitro susceptibilities of a total of 174 ciprofloxacin-resistant Enterobacteriaceae and Pseudomonas aeruginosa were determined. According to the BSAC and NCCLS breakpoints, meropenem, aztreonam, ceftibuten, ceftazidime, imipenem and cefotaxime were the most active (> 90%) antimicrobial agents tested against Enterobacteriaceae. Susceptibility of these strains to piperacillin/tazobactam, cefpodoxime and cefixime (84.96%) was higher than that to tobramycin, gentamicin and fosfomycin (50-75%). More than 90% of P. aeruginosa were susceptible to meropenem when both interpretative susceptibility breakpoint criteria were used. Piperacillin, piperacillin/tazobactam and ceftazidime were active against 50-75% of the same strains. Meropenem was the most active antimicrobial tested against all ciprofloxacin-resistant clinical isolates assayed.

Comparison of MICs of ceftiofur and other antimicrobial agents against bacterial pathogens of swine from the United States, Canada, and Denmark.

The MICs of ceftiofur and other antimicrobial agents, tested for comparison, for 515 bacterial isolates of pigs from the United States, Canada, and Denmark with various diseases were compared. The organisms tested included Actinobacillus pleuropneumoniae, Escherichia coli, Pasteurella multocida, Salmonella choleraesuis, Salmonella typhimurium, Streptococcus suis, Streptococcus dysgalactiae subsp. equisimilis, Streptococcus equi subsp. equi, and Streptococcus equi subsp. zooepidemicus. In addition to ceftiofur, the following antimicrobial agents or combinations were tested: enrofloxacin, ampicillin, sulfamethazine, trimethoprim-sulfadiazine (1:19), erythromycin, lincomycin, spectinomycin, lincomycin-spectinomycin (1:8), tilmicosin, and tetracycline. Tilmicosin was only tested against the U.S. isolates. Overall, ceftiofur and enrofloxacin were the most active antimicrobial agents tested against all isolates, with MICs inhibiting 90% of isolates tested (MIC90s) of < or = 2.0 and < or = 1.0 microgram/ml, respectively. Erythromycin, sulfamethazine, spectinomycin, and lincomycin demonstrated limited activity against all of the organisms tested, with MIC90s of > or = 8.0, > or = 256.0, > or = 32.0, and > or = 16.0 micrograms/ml, respectively. Trimethoprim-sulfadiazine was active against isolates of A. pleuropneumoniae, S. choleraesuis, S. typhimurium, P. multocida, S. equi, and S. suis (MIC90s, < or = 0.5 microgram/ml) but was less active against the E. coli strains tested (MIC90, > 16.0 micrograms/ml). Ampicillin was active against the P. multocida, S. suis, and S. equi isolates tested (MIC90s, 0.5, 0.06, and 0.06 micrograms/ml, respectively) and was moderately active against S. typhimurium (MIC90s, 2.0 micrograms/ml). However, this antimicrobial agent was much less active when it was tested against A. pleuropneumoniae, S. cholerae-suis, and E. coli (MIC90s, 16.0, > 32.0, and 32.0 micrograms/ml, respectively). Against the U.S. isolates of A. pleuropneumoniae and P. multocida, tilmicosin was moderately active (MIC90s, 4.0 and 8.0 micrograms/ml, respectively). However, this compound was not active against the remaining U.S. isolates (MIC90s, > 64.0 micrograms/ml). Differences in the MICs from one country to another were not detected with enrofloxacin, ceftiofur, or lincomycin for the strains tested, but variations in the MICs of the remaining antimicrobial agents were observed.

Some characteristics of 452 Pseudomonas aeruginosa strains isolated from Spanish Cystic Fibrosis patients

We have studied 42 Spanish Cystic Fibrosis patients during a two year period. 452 strains of P. aeruginosa were isolated. Mucoid morphotype was the most frequent (32.3 %) followed by rough (20.5 %), dwarf (17.4 %), gelatinous (12.2 %), metallic (10.5 %) and enterobacter-like (7.1 %). Serogroup O:6 and polyagglutinable strains were predominant. By serotyping and phage typing we found a maximum of two strains which colonize chronically the lungs. Norfloxacin, tobramycin, ceftazidime and imipenem were the most active antimicrobial agent. The mucoid and metallic strains were more susceptible to antibiotics than the other morphotypes. We have also investigated the effect of iron upon the different morphotypes of P. aeruginosa and we found that the iron deprivation induces in some cases the mucoid morphotype. Pendant deux ans nous avons étudié 42 malades atteints de mucoviscidose; 452 souches de Pseudomonas aeruginosa ont été isolées. La fréquence de morphotypes parmi ces souches était la suivante : mucoïde (32,3 %), rugueux (20,5 %), petit (17,4 %), gélatineux (12,2 %), métallique (10,5 %) et enterobacter-like (7,1 %). Le sérogroupe O:6 et les souches polyagglutinables étaient prédominants. Par lysotypie nous avons trouvé un maximum de deux souches qui colonisaient chroniquement les poumons. Norfloxacine, tobramycine, ceftazidime et imipénème étaient les antibiotiques plus actifs. Les morphotypes mucoïdes et métallique étaient plus sensibles aux antibiotiques que les autres morphotypes. Nous avons aussi trouvé que la déprivation du fer peut induire in vitro l'apparition du morphotype mucoïde.

Etiology of nosocomial infections and the susceptibility of nosocomial pathogens to imipenem and other antimicrobial agents at a tertiary care referral hospital

Medical care has changed substantially in the last few decades: today's care often includes aggressive surgical interventions, new instrumentations, catheterizations, organ transplants, and immunosuppressive, irradiation, and chemotherapeutic treatments. These advances have not come without a price. One such cost is an increase in the incidence of nosocomial infections, especially in tertiary care referral and teaching hospitals. This problem is compounded by nosocomial pathogens that acquire resistance to many of the therapeutic agents used to eradicate them. In Saudi Arabia, as in other developing countries, bacterial pathogens are significantly more resistant to commonly used antimicrobial agents than are pathogens found in the western hemisphere. Consequently, we looked at the susceptibility patterns of 585 nosocomial pathogens from 497 patients at a tertiary care center in Riyadh, Saudi Arabia. Imipenem was found to be the most active antimicrobial agent against gram-negative bacteria, followed closely by third-generation cephalosporins, ciprofloxacin, and aminoglycosides. The in vitro activity of imipenem was almost as good as that of vancomycin against gram-positive nosocomial isolates.

Mycobacterium haemophilum: An emerging pathogen

Mycobacterium haemophilum is emerging as a pathogen of immunocompromised patients particularly those with AIDS and organ transplants. Infection has also occurred in healthy children. Adults usually present with cutaneous manifestations, septic arthritis or occasionally pneumonia. Children have perihilar, cervical or submandibular adenitis. The organism grows on mycobacterial media supplemented with ferric ammonium citrate or hemin, incubated at 30 degrees C to 32 degrees C, two to three weeks after inoculation. The most active antimicrobial agents in vitro are amikacin, ciprofloxacin, clarithromycin, rifabutin and rifampin. Development of resistance to the rifamycins has been demonstrated after patients were treated for several months with several antimycobacterial agents, including the rifamycins. Treatment for several months with at least two agents demonstrated to have low MICs for the organism has been shown to be effective.

In VitroEvaluation of Cefodizime, Cefuroxime, Ceftriaxone against Respiratory Pathogens

The in vitro activity of cefodizime and two comparative cephalosporins, cefuroxime and ceftriaxone were studied against respiratory pathogens. MIC90s of cefodizime were 0.06-0.512 microgram/ml for Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae. MIC50s of cefodizime for Klebsiella pneumoniae and Staphylococcus aureus isolates were 2 micrograms/ml and 8 micrograms/ml respectively. Cefuroxime and ceftriaxone at a concentration of 2 micrograms/ml and 1 microgram/ml inhibited 50% of Klebsiella pneumoniae and 50% of Staphylococcus aureus strains studied respectively. Cefodizime inhibited many of the important respiratory pathogens and can be suggested as an active antimicrobial agent for respiratory tract infections.