Richard S. Schwalbe

Stool microflora in extremely low birthweight infants

AIM To serially characterise aerobic and anaerobic stool microflora in extremely low birthweight infants and to correlate colonisation patterns with clinical risk factors. METHODS Stool specimens from 29 infants of birthweight <1000 g were collected on days 10, 20, and 30 after birth. Quantitative aerobic and anaerobic cultures were performed. RESULTS By day 30, predominant species were Enterococcus faecalis, Escherichia coli, Staphylococcus epidermidis, Enterbacter cloacae, Klebsiella pneumoniae, and Staphylococcus haemolyticus. Lactobacillus andBifidobacteria spp were identified in only one infant. In breast milk fed (but not in formula fed) infants, the total number of bacterial species/stool specimen increased significantly with time (2.50 (SE 0.34) on day 10; 3.13 (0.38) on day 20; 4.27 (0.45) on day 30) as did quantitative bacterial counts; Gram negative species accounted for most of the increase. On day 30, significant inverse correlations were found between days of previous antibiotic treatment and number of bacterial species (r=0.491) and total organisms/g of stool (r=0.482). Gestational age, birthweight, maternal antibiotic or steroid treatment, prolonged rupture of the membranes, and mode of delivery did not seem to affect colonisation patterns. CONCLUSIONS The gut of extremely low birthweight infants is colonised by a paucity of bacterial species. Breast milking and reduction of antibiotic exposure are critical to increasing fecal microbial diversity.

Antimicrobial Susceptibility Testing Protocols

An Overview of the Clinical and Laboratory Standards Institute and its Impact on Antimicrobial Susceptibility Testing, A. L. Barry Antimicrobial Classifications: Drugs for Bugs, C.B. Calderon, and B. Perdue Sabundayo Disk Diffusion Tests and Gradient Methodologies, A. Wanger Macro and Microdilution Methods of Antimicrobial Susceptibility Testing, S. Qaiyumi Automated Systems: An Overview, S. Stuckey Agar Dilution Susceptibility Testing, A. Hanlon, M. Taylor, and J. Dick Antibiograms/Preventive Surveillance: A Continuum of Data Collection, Analysis, and Presentation, J. Thomas and N.T. Rector Anaerobe Susceptibility Testing, D. E. Roe-Carpenter Antifungal Susceptibility Testing of Yeasts, A. Espinel-Ingroff and E. Canton Antifungal Susceptibility Testing of Filamentous Fungi, A. Espinel-Ingroff and E. Canton Susceptibility Testing of Mycobacteria, B. A. Brown-Elliott, S. Cohen, and R.J. Wallace, Jr. Methods for Determining Bactericidal Activity and Antimicrobial Interactions: Synergy Testing/Time-Kill Curves/Population Analysis, P. Verma Serum Bactericidal Testing, H. Nadler and M. Dowzicky Bioassay Methods for Antimicrobial and Antifungal Agents, D.H. Pitkin and E. Martin-Mazuelos Molecular Methods for Bacterial Strain Typing, S. Michaud and D. Berg Pharmacy and Microbiology: Interactive Synergy, B. Perdue Sabundayo and C.B. Calderon Interactions Between Clinicians and the Microbiology Laboratory, J.H. Powers Clinical Microbiology in the Development of New Antimicrobial Agents, C.D.Webb and B.G. Painter

The effect of application of Aquaphor on skin condition, fluid requirements, and bacterial colonization in very low birth weight infants

OBJECTIVE:To determine the effects of repeated application of an occlusive ointment on the skin of very low birth weight infants.STUDY DESIGN:Nineteen neonates of 26 to 30 weeks gestational age were randomly assigned to receive topical Aquaphor ointment twice daily for 2 weeks or to receive standard skin care. Skin quality, fluid requirements, and skin bacterial colonization counts were assessed.RESULTS:Infants treated with Aquaphor had significantly improved skin condition scores versus controls (p = 0.002). Aquaphor improved skin scores over time (p = 0.012) in treated infants, whereas skin scores of untreated infants worsened before eventually healing. There were no significant differences in total fluid requirements, urine output, serum sodium concentrations, skin bacterial counts, fungal counts, or colonization patterns between treated and control infants in either gestational age cohort.CONCLUSION:Aquaphor ointment, used during the first two postnatal weeks, improved skin condition in infants of 26 to 30 weeks’ gestation without changing skin bacterial flora. We speculate that improved skin condition may limit transepidermal water loss and decrease portals of entry for pathogens, thereby potentially decreasing fluid and electrolyte imbalances and sepsis in very low birth weight infants.

Head-injured patients who are nasal carriers of Staphylococcus aureus are at high risk for Staphylococcus aureus pneumonia.

OBJECTIVE To determine if head-injured patients with premorbid nasal colonization with Staphylococcus aureus are at increased risk for S. aureus infection. DESIGN Patients admitted over a 2-yr period were enrolled if they met the following criteria: Injury Severity Score > or = 9, intensive care unit (ICU) admission, hospitalization in another hospital < 24 hrs, no recent use of antibiotics. SETTING Acute care trauma facility. PATIENTS Any patient sustaining acute, blunt, or penetrating injury and meeting the enrollement criteria were eligible. INTERVENTIONS Swab cultures of both internal nares were performed within 72 hrs of readmission and cultured for S. Aureus. Patients were prospectively monitored for S. Aureus infections until discharge. MEASUREMENTS AND MAIN RESULTS Admission nasal cultures were positive (NC+) for S. aureus in 144 of the 776 patients cultured. Forty of the 144 NC+ patients had isolated head (37) or high cervical spine (3) injury, and 11 of that group (27.5%) developed S. aureus infections. The remaining 104 patients positive for S. aureus on admission had no head injury (74) or head combined with torso and extremity injuries (30). S. aureus infection was diagnosed in 11 of the 104 patients (10.6%). The difference in incidence of infections is significant (p <.01), as is the difference in incidence of pneumonia (20% vs. 3.8%, respectively [p <.01]). Organisms causing pneumonia were often the same organisms isolated from the nares on admission. CONCLUSIONS Nasal colonization with S. aureus at the time of severe head injury increases the risk of S. aureus pneumonia during hospitalization. Prophylactic measures against S. aureus pneumonia may help reduce the length and cost of hospitalization.

In vivo selection for transmissible drug resistance in Salmonella typhi during antimicrobial therapy.

We report the recovery of Salmonella typhi that acquired resistance to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, and gentamicin subsequent to multiple antibiotic therapy. Escherichia coli and Klebsiella pneumoniae isolates which were recovered from the same stool sample displayed identical resistance patterns. Agarose gel electrophoresis revealed that S. typhi and laboratory-derived transconjugants contained a high-molecular-weight plasmid present in the resistant intestinal bacteria. Images

Differential Expression of a Mycobacterium tuberculosis Protein Recognized by a Mouse Monoclonal Antibody

Murine monoclonal antibodies were produced against Mycobacterium tuberculosis (Mtb) using standard hybridoma procedures. By a whole cell enzyme‐linked immunosorbent assay (ELISA), one monoclonal antibody (mAb), HB28, demonstrated high level specific reactivity to Mtb. Western blot analysis demonstrated reactivity to a single 65 kDa Mtb protein in the cell wall extract and culture filtrate. HB28 mAb appears to be recognizing a 65 kDa Mtb protein that is over‐expressed by Mtb but not other species under certain culture conditions. Differential expression and detection of this protein by HB28 mAb may have potential for diagnostic applications.

In Vitro Evaluation of High-Level, Gentamicin-Resistant Enterococci Isolated from Bacteremic Patients

We attempted to characterize the susceptibility of high‐level, gentamicin‐resistant (HLGR, minimum inhibitory concentration [MIC] >2000 μg/ml) enterococcal blood isolates and evaluated a small subset of these isolates for bactericidal synergy. Thirteen Enterococcus faecalis and three Enterococcus faecium isolates that were HLGR were prospectively collected. Standard broth macrodilution techniques were used to determine the MICs and minimum bactericidal concentrations to a variety of antibiotics. Two isolates were evaluated for synergy by time‐kill curve methods using combinations of penicillin and streptomycin, teicoplanin and rifampin, and vancomycin and ciprofloxacin. Teicoplanin was the most active antibiotic tested, with all isolates exhibiting susceptibility to this agent. Four E. faecalis isolates and one E. faecium isolate expressed only low‐level resistance to streptomycin (LLSR, MlCs 32–64 μg/ml). Penicillin and streptomycin produced bactericidal synergy in the LLSR isolate. The other antibiotic combinations did not result in bactericidal synergy in the two isolates tested. For HLGR enterococci that are only LLSR, the combination of penicillin‐streptomycin appears to provide adequate bactericidal activity. Teicoplanin may potentially be useful for streptomycin‐resistant HLGR isolates.