Tag Archive for: multidrug-resistant bacteria

Staphylococcus aureus

Understanding antibiotic resistance in patients with cystic fibrosis

Staphylococcus aureus

Patients with cystic fibrosis who carried antibiotic-resistant bacteria, such as Staphylococcus aureus, in their lungs had significantly lower microbial diversity and more aggressive disease, according to a small study published in Heliyon.

A defective gene causes thick, sticky mucus to build up in the lungs of patients with cystic fibrosis (CF). There, it traps bacteria, causing patients to develop frequent lung infections that progressively damage these vital organs and impair patients’ ability to breathe.

Most patients with this progressive genetic disorder die by the fourth decade of life. A key to helping patients live even that long – a vast improvement from an average lifespan of 10 years  just decades ago – is judicious use of antibiotics, explains Andrea Hahn, M.D., a pediatric infectious diseases specialist at Children’s National Health System.

But antibiotics are a double-edged sword, Dr. Hahn adds: Although they’re necessary to eradicate lung infections, repeated use of these drugs can lead to antibiotic resistance, making it tougher to treat future infections. Also, antibiotic use can kill the nonpathogenic bacteria living in the lungs as well. That decreases the diversity of the microbial community that resides in the lungs, a factor associated with disease progression. But how antibiotic resistance impacts the relationship between lung bacterial diversity and CF patients’ pulmonary function has been unknown.

Dr. Hahn and colleagues investigated this question in a small study that was published online Sept. 17, 2018, in Heliyon. Their findings suggest that the presence of multidrug resistant bacteria in the airways of patients with CF is associated with decreased microbial diversity and decreased pulmonary function.

In the study, the researchers recruited six patients with CF from Children’s National during well-child visits. During those appointments, the research team collected respiratory secretions from these volunteers. They collected more samples at subsequent visits, including:

  • When patients were admitted to the hospital for pulmonary exacerbations (periods when infections inflamed their airways, making it difficult to breathe);
  • Just after intravenous antibiotic courses to treat these infections; and
  • Thirty days after patients completed antibiotic therapy, when their lungs’ bacterial flora had some time to bounce back.

Over the 18-month study period, these patients made multiple visits for exacerbations and antibiotic treatments, leading to samples from 19 patient encounters overall.

The scientists then analyzed each sample in two different ways. They used some to grow cultures in petri dishes, the classic method that labs use to figure out which bacterial species are present and to determine which antibiotics are effective in tamping them down. They used another part of the sample to run genetic analyses that searched for antibiotic resistance genes. Both methods were necessary to gather a complete inventory of which antibiotic-resistant bacteria were present, Dr. Hahn explains.

“Laboratory cultures are designed to grow certain types of bacteria that we know are problematic, but they don’t show everything,” she says. “By genetically sequencing these samples, we can see everything that’s there.”

Their results revealed a host of bacterial species present in these patients’ airways, including methicillin-resistant Staphylococcus aureus, a notoriously hard-to-treat microbe. Patients who carried this or other antibiotic-resistant bacteria had significantly lower microbial diversity in their samples and more aggressive disease. Their samples also were more likely to contain bacteria of the genus Alcaligenes, whose role in CF is not yet known.

Although heavy antibiotic use probably contributed to both the antibiotic resistance and lowered microbial diversity, Dr. Hahn says, the answer isn’t to reduce use of these drugs: They’re necessary to help patients with CF recover after each bout with pulmonary exacerbations. Rather, she says, using methods beyond a simple lab culture can help doctors target infectious bacteria more selectively, perhaps avoiding collateral damage.

“We can’t stop using antibiotics,” she says, “but we can learn to use them better.”

In addition to Dr. Hahn, Children’s co-authors include Aszia Burrell; Hani Fanous; Hollis Chaney, M.D.; Iman Sami Zakhari, M.D.; Geovanny F. Perez, M.D.; Anastassios C. Koumbourlis, M.D., MPH; and Robert J. Freishtat, M.D., MPH; and Senior Author, Keith A. Crandall, of The George Washington University.

Financial support for the research described in this post was provided by the National Institutes of Health National Center for Advancing Translational Sciences under award number UL1TR000075 and the National Heart, Lung and Blood Institute under award number K12HL119994.

ER Nurse

An unexpected discovery in a central line

ER Nurse

About a year and a half ago, a 6-year-old boy arrived at Children’s Emergency Department after accidently removing his own gastrointestinal feeding tube. He wasn’t a stranger to Children’s National Health System: This young patient had spent plenty of time at the hospital since birth. Diagnosed in infancy with an intestinal pseudo-obstruction, a rare condition in which his bowels acted as if there were a blockage even though one was not present, parts of his intestine died and had been removed through multiple surgeries.

Because of this issue and associated health problems, at 4 years old he had a central line placed in a large vein that leads to his heart. That replaced other central lines placed in his neck earlier after those repeatedly broke. This latest central line in his chest als0 had frequent breaks. It also had become infected with multidrug-resistant Klebsiella bacteria two years before he was treated at Children’s National for inadvertently removing his feeding tube.

On that day, he seemed otherwise well. His exam was relatively unremarkable, except for a small leak in his central line and a slight fever. Those findings triggered cultures taken both from blood flowing through his central line and the surrounding skin.

“No one expected him to grow anything from these cultures, especially from a child who looked so healthy,” explains Madan Kumar, a fellow in Children’s division of Pediatric Infectious Disease and a member of the child’s care team. But a mold grew prolifically. Further investigation from a sample sent to the National Institutes of Health showed that it was a relatively new species known as Mucor velutinosus.

Because such an infection had never been reported in a child whose immune system wasn’t extremely compromised from cancer, Kumar and team decided to publish a case report. The study appeared online Jan. 24, 2018, in the Journal of the Pediatric Infectious Diseases Society.

Kumar notes that this patient faced myriad challenges. Not only did he have a central line, but the line also had numerous problems, necessitating fixes that could increase the chance of infection. Additionally, because of his intestinal issues, he had a chronic problem with malabsorption of nutrients. Patients with this issue often are treated liberally with antibiotics. Although this intervention can kill “bad” bacteria that can cause an infection, they also knock out “good” bacteria that keep other microorganisms – like fungi – in check. On top of all of this, the patient was receiving a nutrient-rich formula in his central line to boost his caloric intake, yet another factor associated with infections.

Patients who develop this specific fungal infection are overwhelmingly adults who are immunocompromised, Kumar explains, including those with diabetes, transplant recipients, patients with cancer and those who have abnormally low concentrations of immune cells called neutrophils in their blood. The only children who tend to get this infection are preterm infants of very low birth weight who haven’t yet developed a robust immune response.

Because there was only one other published case report about a child with M. velutinosus – a 1-year-old with brain cancer who had undergone a bone marrow transplant – Kumar notes that he and colleagues were at a loss as to how best to treat their patient. “There’s a paucity of literature on what to do in a case like this,” he says.

Fortunately, the treatment they selected was successful. As soon as the cultures came back positive for this mold, the patient went on a three-week course of an antifungal drug known as amphotericin B. Surgeons also removed his infected central line and placed a new one. These efforts cured the patient’s infection and prevented it from spreading and potentially causing the multi-organ failure associated with these types of infections.

This case taught Kumar and colleagues quite a bit – knowledge that they wanted to share by publishing the case report. For example, it reinforces the importance of central line care. It also highlights the value of thoroughly investigating potential problems in a patient with risk factors, even one who appears otherwise healthy.

Finally, Kumar adds, the case emphasizes the importance of good antibiotic stewardship, which can help prevent patients from developing sometimes deadly secondary infections like this one. “This is not an organism that you see growing in a 6-year-old very often,” he says. “The fact that we saw it here speaks to the need to be judicious with broad-spectrum antibiotics so that we have a number of therapeutic options should we see unusual cases like this one.”