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M J Zervos

Publications and source records attributed to M J Zervos.

At least 91 records · Page 5Linked to original sources
PubMed1988

A nosocomial outbreak of ampicillin-resistant Haemophilus influenzae type b in a geriatric unit.

A nosocomial outbreak of Haemophilus influenzae type b (Hib) bronchitis occurred in a geriatric unit. The three infected patients were grouped together in an isolation unit and treated. A prevalence survey was done by obtaining pharyngeal cultures from patients and staff in the unit. One patient and a nurse were asymptomatic pharyngeal carriers of Hib. One infected patient was bedridden, and his only known Hib contact was the nurse. Geographic clustering was the only significant risk factor, as determined by a case-control study. Carriers were treated with rifampin. The isolates were characterized for strain relatedness by using three methods. All produced beta-lactamase and all were serotype b. Plasmid profiles and restriction endonuclease analysis of bacterial DNA were performed; chromosomes were digested with the restriction endonucleases HindIII and HaeIII. Strains were confirmed as identical by using these methods and were different from two Hib control strains producing beta-lactamase. This study documents nosocomial transmission of Hib, by using molecular typing methods.

Aged↗
PubMed1988

A nosocomial outbreak of Branhamella catarrhalis confirmed by restriction endonuclease analysis.

An outbreak of respiratory illness due to Branhamella catarrhalis occurred in the intermediate care unit of a Veterans Administration hospital and involved patients and staff members. Four patients had pneumonia and four had bronchitis. Infected patients were placed in a cohort separated from noninfected patients and were treated. Pharyngeal culture was used to survey prevalence in staff and all other patients on the unit; three of 18 staff members and two of 19 asymptomatic patients were positive for B. catarrhalis. A case-control study showed that respiratory therapy, steroid use, and location within the unit were significant risk factors for B. catarrhalis infection or colonization. Strains from five patients and two staff members had identical bacterial restriction endonuclease digestion patterns with three different enzymes; these patterns were distinct from those of control strains. This study is the first to document an outbreak of B. catarrhalis infection confirmed with a typing system and thus establishes B. catarrhalis as a nosocomial pathogen.

Adult↗
PubMed1988

Enterococcal superinfection in patients treated with ciprofloxacin.

Two patients developed serious enterococcal superinfection following therapy with intravenous ciprofloxacin. The strains causing bacteraemia were susceptible to low concentrations of ciprofloxacin when tested at a standard inoculum. However, at an inoculum of 1 X 10(7) cfu/ml they were resistant to high concentrations of ciprofloxacin. Our data suggest that ciprofloxacin should not be used to treat patients with serious enterococcal infection and that patients treated with ciprofloxacin should be monitored carefully for the development of enterococcal superinfection.

Adult↗
PubMed1988

Characterization and comparison of two penicillinase-producing strains of Streptococcus (Enterococcus) faecalis.

We identified two beta-lactamase-positive enterococci. One strain was high-level (MIC, greater than 2,000 microgram/ml) gentamicin resistant; the other was not (MIC, 12.5 microgram/ml). beta-Lactamase production was extrachromosomally mediated in both strains, and both strains showed an inoculum effect reversed by beta-lactamase inhibitors. The strain lacking high-level gentamicin resistance showed synergistic killing with a combination of penicillin, clavulanic acid, and gentamicin.

Ampicillin↗
PubMed1987

High-level aminoglycoside-resistant enterococci. Colonization of nursing home and acute care hospital patients.

Enterococci with high-level resistance (HLR) to gentamicin sulfate and other aminoglycosides have emerged as pathogens in recent years. More than half of all current isolates of enterococci at the Ann Arbor (Mich) Veterans Administration (VA) Medical Center are HLR strains. We determined the rate of colonization with HLR enterococci in patients in the acute care hospital, the attached nursing home, and a private nursing home. We also studied the factors related to colonization and the molecular relatedness of strains of HLR enterococci in these settings. In the VA facilities, 47.4% of patients in the nursing home and 36.1% of patients in the acute care hospital were colonized, compared with a 4.3% colonization rate in the private nursing home. Intravenous or Foley catheters and bedridden status were associated with colonization in the acute care setting; the need for advanced nursing care and prior antibiotic therapy were associated with colonization in the nursing home. Environmental surfaces were contaminated with HLR enterococci in both VA settings. Plasmid analysis of HLR strains revealed identity between both patient and environmental strains in the nursing home care unit and the acute care hospital. Nursing home patients, with their high rate of colonization with HLR enterococci and their frequent movement into the acute care hospital, may play a role as a reservoir for subsequent transmission of HLR enterococci.

Cross Infection↗
PubMed1987

Single-concentration broth microdilution test for detection of high-level aminoglycoside resistance in enterococci.

Growth in a single broth microdilution well containing gentamicin at a concentration of 500 micrograms/ml predicted high-level resistance to gentamicin (MIC, greater than or equal to 2,000 micrograms/ml) in 505 of 508 clinical isolates of enterococci. Failure to achieve synergistic killing with the combination of penicillin and an aminoglycoside was demonstrated with 100% specificity in 20 strains which showed resistance to 500 micrograms of gentamicin per ml. We recommend this procedure be adopted as a routine screening test to detect high-level aminoglycoside resistance in enterococci.

Anti-Bacterial Agents↗
PubMed1987

Nosocomial infection by gentamicin-resistant Streptococcus faecalis. An epidemiologic study.

Enterococci with high-level resistance to gentamicin account for 55% of clinical isolates of enterococci found in patients at the Ann Arbor Veterans Administration Medical Center. We prospectively studied cultures obtained from all 100 patients hospitalized from 1 December 1985 through 23 January 1986 on the surgical and thoracic intensive care units and a general medical floor. Ten patients' cultures grew colonies of gentamicin-resistant enterococci--six after admission to the intensive care units and four after hospitalization on the medical ward. The initial sites of colonization were the rectal and perineal areas in seven patients, sternal wound in one, urine in one, and the rectal and perineal areas as well as urine after Foley catheter insertion in one. Nine patients died and three of the deaths were associated with enterococcal infection. The acquisition of resistant strains was associated with previous and more frequent exposure to antimicrobial agents, and with geographic clustering of patients. Resistant enterococci were isolated from the hands of hospital personnel and were frequently isolated from environmental surfaces. Nosocomial acquisition and interhospital spread of gentamicin-resistant enterococci was shown to have occurred when plasmid content was used as an epidemiologic marker.

Adult↗
PubMed1986

High-level resistance to gentamicin in Streptococcus faecalis: risk factors and evidence for exogenous acquisition of infection.

Between November 1981 and October 1984, 48 of 3,456 clinical isolates of Streptococcus faecalis that were studied showed high-level (greater than 2,000 micrograms/ml) resistance to gentamicin. A case-control study comparing patients with gentamicin-susceptible (MIC less than 64 micrograms/ml) and -resistant S. faecalis infections showed significant associations (P less than .01) between the development of infection with highly gentamicin-resistant S. faecalis and prior antimicrobial therapy (particularly with cephalosporins or aminoglycosides), perioperative antibiotic prophylaxis, prior surgical procedures, and longer hospitalization. All highly resistant strains appeared to be nosocomial since 12 cases were clustered on a surgical floor and in a burn unit. In vitro transfer of gentamicin resistance by filter mating was observed for 44 of 48 isolates. The use of plasmid content as an epidemiological marker suggested nosocomial transmission and exogenous acquisition of S. faecalis.

Adult↗
PubMed1986

Heterogeneity of plasmids determining high-level resistance to gentamicin in clinical isolates of Streptococcus faecalis.

Between November 1981 and October 1984, 48 of 3,458 clinical isolates of Streptococcus faecalis at the University of Michigan Hospital showed high-level (greater than 2,000 micrograms/ml) resistance to gentamicin, as well as to all other clinically available aminoglycosides. Thirteen percent of clinical isolates in the University of Michigan Hospital currently demonstrate this level of resistance. Transfer of resistance to a plasmid-free streptococcal recipient was observed in filter matings for 44 of 48 such isolates. Analysis of transconjugants by agarose gel electrophoresis showed that gentamicin resistance was transferred alone in 8 isolates and was combined with other antimicrobial resistances on the same plasmid in the other 36 isolates. There were seven isolates which transferred the property of horse blood beta-hemolysis along with gentamicin resistance. Transfer of gentamicin resistance was either by conjugative plasmids or by a nonconjugative but mobilizable plasmid. Transfer frequencies on filters ranged from 4.7 X 10(-2) to 4.1 X 10(-8). Based on donor and transconjugant antibiotic resistance markers, agarose gel electrophoresis, transfer properties, and restriction enzyme analysis, the plasmid content of transconjugants was heterogeneous and could be classified into at least seven different patterns. These findings argue against clonal dissemination as the cause of the increased frequency of resistant strains and suggest that resistance to gentamicin appears on a variety of physically distinct conjugative and nonconjugative plasmids in S. faecalis.

DNA, Bacterial↗
PubMed1985

Reversal of the in vitro susceptibility of enterococci to trimethoprim-sulfamethoxazole by folinic acid.

The in vitro susceptibilities of 21 clinical isolates of Streptococcus faecalis to trimethoprim (TMP) in combination with sulfamethoxazole (SMX) was evaluated in Mueller-Hinton broth (MHB) in the presence and absence of folinic acid as well as in urine. The mean MIC and MBC in MHB, expressed as the TMP concentration, was 0.13 and 0.32 micrograms of TMP-SMX per ml, respectively. In MHB supplemented with folinic acid, the mean MIC and MBC was 3.3 and 5.5 micrograms of TMP-SMX per ml, respectively. In urine the mean MIC of TMP-SMX for these isolates was 8.1 micrograms/ml (range, 1.6 to 50 micrograms/ml). All isolates were inhibited by less than 0.01 micrograms of TMP-SMX per ml when methotrexate was added to the urine.

Drug Combinations↗
PubMedDate not supplied

Time-kill kinetic studies of ampicillin/sulbactam for beta-lactamase-producing enterococci.

beta-Lactamase-producing (Bla+) enterococci have now been reported from several geographic areas. Most of these strains also demonstrate high-level aminoglycoside resistance, making therapy of serious infections due to Bla+ enterococci difficult. Using time-kill kinetic studies, we evaluated the activity of ampicillin-sulbactam (Am/SB) against five clinical Bla+ Enterococcus faecalis isolates from three geographically distinct areas. Am at fourfold minimum inhibitory concentrations (MIC) concentrations did not achieve bactericidal activity as determined by time-kill kinetic studies. Am/SB achieved 99.9% reduction in growth at 24 hr at twofold MIC concentrations without an aminoglycoside in four of five strains. SB alone had little independent activity against any of the strains, but synergy of killing was achieved in all five strains with a combination of Am + SB. No synergy was shown in a Bla- control strain. Am/SB may be useful for serious infections due to Bla+ enterococci.

Ampicillin↗
PubMedDate not supplied

In vitro activity of sparfloxacin and clinafloxacin against multidrug-resistant enterococci.

We evaluated the in vitro susceptibility of 140 clinical enterococcal isolates to the quinolones sparfloxacin and clinafloxacin. Isolates included Enterococcus faecalis (107), Enterococcus faecium (29), Enterococcus raffinosus (3), and one Enterococcus gallinarum. There were 111 isolates that showed high-level [minimum inhibitory concentrations (MICs) > or = 2000 micrograms/ml] resistance to gentamicin and were resistant to high levels of all other aminoglycosides; five isolates produced beta-lactamase; 21 isolates were resistant (MIC > or = 16 micrograms/ml) to ampicillin and were not beta-lactamase producers; and 13 strains were resistant (MIC > or = 32 micrograms/ml) to vancomycin. Most strains were susceptible to low concentrations of sparfloxacin and clinafloxacin, with MIC90S of 0.6 microgram/ml and 0.5 micrograms/ml, respectively. There were no inoculum effects. Time-kill experiments were performed with 22 strains; using 2 x MIC at 24 h, a > or = 2 log10 reduction in growth was observed with sparfloxacin and clinafloxacin for 14 and 17 strains, respectively. Time-kill synergism experiments were performed with 15 strains lacking high-level aminoglycoside resistance. In vitro bacterial synergism with the combination of sparfloxacin or clinafloxacin with streptomycin or gentamicin was observed for five and 12 isolates, respectively. The bactericidal activity of sparfloxacin and clinafloxacin suggest that these antibiotics may prove useful for therapy of multidrug resistant enterococci.

Anti-Infective Agents↗
PubMedDate not supplied

High-level gentamicin resistance in Enterococcus: microbiology, genetic basis, and epidemiology.

Antibiotic resistance is an ever-increasing problem in enterococci. These bacteria are remarkable in their ability to acquire and disseminate antibiotic resistance genes by a variety of routes. Since first described in 1979, high-level resistance to gentamicin (MIC, greater than 2,000 micrograms/mL) has spread worldwide and has been responsible for serious infections. Resistance is plasmid-mediated and due to aminoglycoside-modifying enzymes. High-level gentamicin resistance indicates that there will be no synergistic bactericidal activity with penicillin-gentamicin combinations. The epidemiology of nosocomial enterococcal infections is remarkably similar to that of nosocomial infections caused by methicillin-resistant staphylococci and by multidrug-resistant gram-negative bacilli. The most likely way these resistant bacteria are spread among hospital patients is via transient carriage on the hands of hospital personnel. Patient-to-patient and interhospital transmission of strains has been reported recently. However, clonal dissemination is not the cause of the increased frequency of resistant strains, since gentamicin resistance appears in a variety of different conjugative and nonconjugative plasmids in Enterococcus.

Cross Infection↗
PubMedDate not supplied

Bacteremia in narcotic addicts at the Detroit Medical Center. I. Microbiology, epidemiology, risk factors, and empiric therapy.

The changing microbiology of bacteremia among narcotic addicts in Detroit raised concerns about current presumptive antimicrobial therapy. In a one-year study of incidence, microbiology, sites, and risk factors, 180 bacteremic addicts (15% of addict-related admissions) were followed prospectively. Cases of bacteremia were caused by methicillin-sensitive Staphylococcus aureus (33%), methicillin-resistant S. aureus (MRSA, 24%), streptococci (20%), mixed organisms (11%), Pseudomonas aeruginosa (9%), and miscellaneous other single organisms (3%). Endocarditis (41%) and abscess or cellulitis (34%) were usually found. Multivariate analysis of host factors and addiction habits yielded results predictive of bacterial species but not of infection sites. Previous hospitalization, long-term addiction, and nonprescribed antibiotic use were associated with MRSA acquisition (odds ratio, 8.6:1). All addicts with polymicrobial or P. aeruginosa bacteremia abused pentazocine and tripelennamine (P = .05). Many of the addicts with streptococcal bacteremia were women who did not abuse antibiotics (odds ratio, 20.7:1). Physicians inappropriately prescribed empiric antibiotics for 67 of 72 addicts with MRSA, P. aeruginosa, or polymicrobial infection. The results of regression analysis suggest that, guided by the patient's history, the physician can prescribe appropriate empiric antimicrobial therapy for bacteremia in the febrile addict in Detroit.

Adolescent↗