Top Infectious Disease News of the Week— February 17, 2019

#5: Outpatient Infection Control—Managing Microbial Transmission

Outpatient clinics are not traditionally focused on infection control initiatives. Despite 990 million physician office visits and 125.7 million hospital outpatient visits each year in the United States, these clinics are often overlooked when it comes to controlling the transmission of harmful pathogens.

Until recently, acute and long-term care facilities have been viewed as common sources for microbial transmission. Fortunately, focus has slowly been moving to outpatient clinics and the importance of infection prevention measures for patient and health care provider safety. A new study, published in the American Journal of Infection Control, sought to evaluate outpatient clinic microbial transmission and a disinfecting spray’s role in reducing the spread of germs.

“The key takeaway from our outpatient clinic study is that microbes spread quickly throughout the clinic, contaminating the majority of high-touch surfaces after only 2 hours of work activity,” Kelly Reynolds, PhD, MSPH, professor and chair in the Department of Community, Environment, and Policy at the University of Arizona Zuckerman College of Public Health, told Contagion^® in an interview.

Read about managing microbial transmission in outpatient clinics.

#4: Emergence of Ceftazidime-Avibactam Resistance: What Have We Learned in the Past 4 Years?

The US Food and Drug Administration (FDA) approved ceftazidime-avibactam for clinical use in February 2015, effectively changing the landscape for treatment of carbapenem-resistant Enterobacteriaceae (CRE) infec­tions. Compared with traditional salvage agents (including aminoglycosides, colistin, and tigecycline), treatment with ceftazidime-avibactam is safer and more effective.^1-3 Despite these encouraging findings, the emergence of ceftazidime-avi­bactam resistance has been reported and may pose a serious threat to patients. Over the past 4 years, new insights into the molecular mechanisms and predisposing factors associated with ceftazidime-avibactam resistance have been described.

Avibactam is a novel diazabicyclooctane β-lactamase inhib­itor that reversibly inhibits Ambler classes A, C, and some class D β-lactamases. Avibactam does not inhibit class B metallo-β-lactamases (MBLs). In surveillance studies, the combination of ceftazidime-avibactam demonstrated potent in vitro activity against a wide spectrum of gram-negative pathogens, including multidrug-resistant Enterobacteriaceae and CRE.^4-6 Categorized by the FDA-approved susceptibility breakpoint (≤8/4 μg/mL), ceftazidime-avibactam was active against 97.5% of contemporary CRE isolates.⁶ In a subsequent study, 99.3% of Klebsiella pneumoniae carbapenemase (KPC)- producing CRE were susceptible.5 Against OXA-48 producing CRE, ceftazidime-avibactam was active against 100% of isolates in a recent clinical study.⁷

Read about emerging resistance of ceftazidime-avibactam.

#3: Staying Ahead of the Curve: Implementing AUC-Guided Vancomycin Dosing

Few topics in infectious diseases pharmacotherapy provoke such strong emotions and opinions in so broad an audience as vancomycin dosing and monitoring. After more than 6 decades of experience with the archetypal glycopeptide, clinicians are still learning how best to optimize its dosing.

In 1987, pharmacokinetic/pharmacodynamic data from mouse thigh models were presented that showed that the 24-hour area under the concentration time curve to minimum inhib­itory concentration ratio, or AUC:MIC, was the best predictor of vancomycin efficacy against Staphylococcus aureus.¹ Now, more than 30 years later, we are in the middle of a para­digm shift from trough-guided vancomycin dosing to true AUC-guided dosing.

LAY OFF THE TROUGH AND EMBRACE THE CURVE

Consensus guidelines on vancomycin therapeutic drug monitoring, published in 2009, suggest a serum trough concentration range of 15 to 20 mg/L as a surrogate goal for an AUC:MIC ≥400 in patients with moderate to severe S aureus infections.²

Read about AUC-guided vancomycin dosing.

#2: Fighting Flu With Math: Predicting Peak Season, Spread, and Vaccination Patterns

A team of investigators at New York University is using math to help fight influenza.

Flu activity in the United States continues to rise, with the percentage of people visiting their health care providers for flu-like illnesses up in the week ending February 5, 2019, according to the US Centers for Disease Control and Prevention’s (CDC) weekly FluView.

The mathematical model, developed by NYU professor Maurizio Porfiri, PhD, MSc, and 2 Italian investigators with visiting appointments at NYU, analyzes epidemiological and sociological factors to predict when the influenza season will peak, who should be vaccinated, when vaccinations should occur, and whether to quarantine infected patients, according to study published by the Society for Industrial and Applied Mathematics in the SIAM Journal on Applied Dynamical Systems.

Read about fighting flu with math.

#1: Typhus Outbreak Strikes Los Angeles, but the City Is Not Alone: Public Health Watch

The people of Los Angeles “smell a rat.”

No, not literally—although this too can be troubling, of course—but figuratively. As in, something is just not right. What has the normally laid-back Southern Californians so unsettled? An ongoing outbreak of typhus.

According to a February 18, 2019, report in the Los Angeles Times, there were 19 cases of the age-old disease among the city’s homeless population, centered in the downtown area, late last year. However, as troubling as this outbreak has been, the numbers suggest it may, in fact, be part of a growing trend. According to state health data cited by the Times, there were 167 cases of typhus in California in 2018, compared with just 13 in 2008. In all, 95% of those infected last year resided in Los Angeles and Orange counties.

“Rodents are the [primary] reservoir for typhus, but opossums and domestic pets can also play a role with bringing infected fleas into the living environment,” said Kristy Murray, DVM, PhD, professor of pediatric tropical medicine and molecular virology at Baylor College of Medicine and director of Texas Children’s Hospital Center for Human Immunobiology, in explaining the challenges facing Los Angeles and other larger cities across the US. Dr. Murray and her team have published several reports on typhus outbreaks, include one in the December 2017 issue of Emerging Infectious Diseases, which described 18 confirmed cases among children in Houston.

“These outbreaks have become much more common over the past decade,” she told Contagion®. “We have witnessed incredible emergence here in Texas similar to what is being seen in California. Before 2007, we had no reported cases of typhus in the Houston area. All typhus transmission was confined to the southern part of the state. In 2003, only 22 cases were reported state-wide, compared to over 700 reported cases a year ago. Now in the summers, we see numerous cases hospitalized here in Houston. In children, we see around 1 out of every 5 cases require intensive care.”

Read about the typhus outbreak in Los Angeles.